II Thoracic Limb 76 I. Vessels & Nerves, left neck & shoulder area, lateral view B. Cephalic v. * w v NERVES & VESSELS of the THORACIC LIMB - 1 t a b A. Ext. jugular v. 1. Axillobrachial v. (I, III): in the carnivore, it is a branch of the cephalic v. in the arm, passing proximally between the deltoideus and triceps brachii mm., then under the deltoideus m. and behind the humerus to dump into the axillary v. (found later) in the armpit (axilla). 2. Omobrachial v. (I, III): a branch of the axillobrachial v. that crosses over the brachio- cephalicus m. to empty into the external jugular v. in the carnivore. a. Omotransversarius m. (I) b. Trapezius m. (I) c. Latissimus dorsi m. (I) d. Deep pectoral m. (I) e. Long head - triceps brachii m. (I) f. Lateral head - triceps brachii m. (I) g. Deltoid m. (I) h. Extensor carpi radialis m. (II) i. Medial & lateral branches of the superficial brachial a. (II) j. Medial & lateral branches of the superficial radial n. (I, II) k. Superficial cervical a. and v. (I) m. Cranial vena cava (III) n. Brachiocephalic v. (III) o. Subclavian v. (III) p. Axillary v. (III) Left side: place your dog in right lateral recumbency. Carefully remove the skin from the neck, left limb, and thorax very carefully, saving all vessels and nerves! Do not have to worry about the cutaneous trunci m., unlike on the right side. - Incise transversely from both ends of your midline inci- sion to the dorsal midline. The cranial incision should pass over the caudal side of the mandible and 1/100" behind the ear. - Circumscribe an incision 2" (5 cm) distal to the carpus (not the elbow, as was done on the right limb). - Connect your midline incision with an incision across the axilla and medial side of the limb to the circumscribed incision. After all the skin incisions are done, separate the skin from Skinning the left thoracic limb the body and arm, roughly as done for the right side: - Separate the skin so your assistant can pull on the two skin flaps, stretching the subcutaneous (SQ) tissue. - Take long, sweeping passes through the SQ reflecting the skin as two long planes to the thoracic limb. - Extreme care is needed to NOT remove the cephalic v. from the cranial aspect of the forearm and elbow (do not pull off the veins with the skin). . Dissect the skin off the limb to meet the two skin flaps past the limb forming one continuous line of dissection. . Continue reflecting the single line to the dorsal midline with sweeping passes of the scalpel. Dissect the large superficial vein in the neck: A. External jugular v. (I, III): the large cutaneous vessel in the neck that is the main venous return from the head. It is formed by the joining of the maxillary and linguofacial vv. near the mandible. Locate and carefully bluntly dissect the vessels (see box opposite). B. Cephalic v.: arises on the palmar side of the paw, travels proximally, wrapping around the medial side of the ante- brachium to reach the cranial forearm. It is joined there by the accessory cephalic v. The cephalic v. then continues up the cranial forearm and elbow. It passes over the triceps brachii m. in the arm, then under the brachiocephalicus m. to empty into the external jugular v. close to the thoracic inlet. C. Accessory cephalic v. (II, III): arising from the dorsum of 2 * 1 * z d c f e g q. Subscapular v. (III) r. Brachial v. (III) s. Median v. (III) t. Proximal lateral cutaneous branches (I) u. Intercostobrachial n. (I) v. Sternocephalicus m. (I) w. Brachiocephalicus m. (I) x. Maxillary v. (I) y. Linguofacial v. (I) z. Accessory n. (I) u k y x * Defined in the legend or text j D *
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II Thoracic Limb
76
I. Vessels & Nerves, left neck & shoulder area, lateral view
B. Cephalic v.*
w
v
NERVES & VESSELS of the THORACIC LIMB - 1
t a
b
A. Ext. jugular v.
1. Axillobrachial v. (I, III): in the carnivore, it is a branch of the cephalic v. in the arm, passing proximally between the deltoideus and triceps brachii mm., then under the deltoideus m. and behind the humerus to dump into the axillary v. (found later) in the armpit (axilla).
2. Omobrachial v. (I, III): a branch of the axillobrachial v. that crosses over the brachio-cephalicus m. to empty into the external jugular v. in the carnivore.
a. Omotransversarius m. (I)b. Trapezius m. (I)c. Latissimus dorsi m. (I) d. Deep pectoral m. (I)e. Long head - triceps brachii m. (I) f. Lateral head - triceps brachii m. (I)g. Deltoid m. (I)h. Extensor carpi radialis m. (II)i. Medial & lateral branches of the superficialbrachiala.(II) j. Medial & lateral branches of the superficialradialn.(I, II) k.Superficialcervicala.andv.(I)m. Cranial vena cava (III)n. Brachiocephalic v. (III)o. Subclavian v. (III)p. Axillary v. (III)
Left side: place your dog in right lateral recumbency. Carefully remove the skin from the neck, left limb, and thorax very carefully, saving all vessels and nerves! Do not have to worry about the cutaneous trunci m., unlike on the right side. - Incise transversely from both ends of your midline inci-sion to the dorsal midline. The cranial incision should pass over the caudal side of the mandible and 1/100" behind the ear.
- Circumscribe an incision 2" (5 cm) distal to the carpus (not the elbow, as was done on the right limb).
- Connect your midline incision with an incision across the axilla and medial side of the limb to the circumscribed incision.
After all the skin incisions are done, separate the skin from
Skinning the left thoracic limb
the body and arm, roughly as done for the right side: - Separate the skin so your assistant can pull on the two skin flaps, stretching the subcutaneous (SQ) tissue.
- Take long, sweeping passes through the SQ reflecting the skin as two long planes to the thoracic limb.
- Extreme care is needed to NOT remove the cephalic v. from the cranial aspect of the forearm and elbow (do not pull off the veins with the skin).. Dissect the skin off the limb to meet the two skin flaps past the limb forming one continuous line of dissection.
. Continue reflecting the single line to the dorsal midline with sweeping passes of the scalpel.
Dissect the large superficial vein in the neck:A. External jugular v. (I, III): the large cutaneous vessel in the neck that is the main venous return from the head. It is formed by the joining of the maxillary and linguofacial vv. near the mandible.
Locate and carefully bluntly dissect the vessels (see box opposite).
B. Cephalic v.: arises on the palmar side of the paw, travels proximally, wrapping around the medial side of the ante-brachium to reach the cranial forearm. It is joined there by the accessory cephalic v. The cephalic v. then continues up the cranial forearm and elbow. It passes over the triceps brachii m. in the arm, then under the brachiocephalicus m. to empty into the external jugular v. close to the thoracic inlet.
C. Accessory cephalic v. (II, III): arising from the dorsum of
2* 1*
z
d
c
f
e
g
q. Subscapular v. (III) r. Brachial v. (III)s. Median v. (III)t. Proximal lateral cutaneous branches (I)u. Intercostobrachial n. (I) v. Sternocephalicus m. (I)w. Brachiocephalicus m. (I)x. Maxillary v. (I) y. Linguofacial v. (I)z. Accessory n. (I)
u
k
y
x
* Definedinthelegendortext j
D*
II Thoracic Limb
77
In the illustration, notice that the cephalic v. is associated with the brachioradialis m., the medial and lateral branches of the superficial brachial a., and the lateral and medial branches of the superficial radial n. (Do not dissect these).
D. Mediancubitalv.:crossesthecranial(flexor)aspectofthe elbow, connecting the cephalic v. with the deep vein on the medial side of the arm (brachial v.),whichyouwillfindlater.E. Brachioradialis m. (II): passes with the cephalic v.
SUPERFICIAL VEINS - 2
B. Cephalic v.*
C. Accessory cephalic v.*
E. Brachioradialis m.
D. Median cubital v.*
i
j
Dissecting vessels and nerves: use a probe and for-ceps /scissors (open and close them in the fascia) to break down the enclosing tissue while the vessels and nerves stretch. Do NOT use a scalpel! Once free and exposed from the fascia, continue freeing the vessel /nerve along its path.
A. Ext. jugular v.*
B. Cephalic v.*
D. Median cubital v.*
1*
2*
m
n
o
pq
r
s
II. Vessels & Nerves, forearm, cranial view
III. Veins of the neck & shoulder, cranial view (modifiedfromEvans'Miller's Anatomy of the Dog)
h
CLINICAL: • Cephalic v.: easiest for venipunc-ture in the dog and thus is often saved for emergencies, using the
external jugular v. instead.• Jugular v. (I, III): just beneath the skin, it is the 2nd most common site for venipuncture after cephalic in the dog. It is not bound in a jugular groove by the brachiocephalicus and sternocephalicus mm. as in the large animals (horse and cow), so it is harder to puncture, as it moves freely.
• Brachioradialis m. (II): not the cephalic v., note when performing a venipuncture, p62.
the paw, it joins the cephalic v. proximal to the carpus. If you can't locate these two veins, look for them attached to the reflected skin of the forearm and arm.
• Veins over the shoulder (axillobrachial, omobrachial): ligate during surgery if
they are in the way.
B*
II Thoracic Limb
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CERVICAL & BRACHIAL PLEXUSES - 1Start to learn about the nervous system before dissecting the nerves of the thoracic limb.
NERVOUS SYSTEM: the control center allowing the body to react to the environment. It stores, integrates, and initi-ates all appropriate responses to information it receives. It is organized into a communication network.
Structurally the nervous system is divided into the central andperipheralsystems.Thisisanartificialdivisionbe-cause many of the nerves of the body are partly in both divisions.
• Central nervous system (CNS): the control center consist-ing of the brain and spinal cord.
• Peripheral nervous system (PNS): all nerve processes connecting to the CNS, consisting of cranial and spinal nerves and ganglia.
Functionally thenervoussystemisclassifiedbytheactivi-ties that are directed into a somatic and autonomic nervous systems.
• Somatic nervous system (soma, body): carries sensory information from the skin and deeper structures of the body such as skeletal muscle, tendons, joint capsules, bones, etc. to the CNS, and conscious voluntary motor impulses from the CNS to the skeletal muscles along cranial and spinal nn. It functions to keep the body in balance with its external environment by allowing the animal to move and interact with its surroundings. We will deal with this system (somatic) now.
• Autonomic nervous system (ANS): carries involuntary impulses (sensory and motor) to and from smooth muscle, cardiac muscle, and glands of the body via cranial and spinal nn. to and from the CNS (spinal cord and brain). It regulatesthebalance(homeostasis)ofthebody'sinternalenvironment, and, when needed, deals with emergency situations. We will start to learn more about this system in the next chapter: "Thorax."
• Sensory (afferent)and motor(efferent):thetwoimpulsesof the nervous system, both somatic and autonomic.
Read the following and study the illustration, and any avail-able models before dissecting the nerves and vessels of the neck and forelimb.
A. Spinal nerve: formed by the joining of the ventral (mo-tor) and dorsal (sensory) roots that arise from the spinal cord. A spinal nerve leaves the spinal canal through the intervertebral foramen to immediately branch into dorsal and ventral branches that supply the periphery with motor andsensoryfibers(axons).B. Dorsal (sensory) root (I, III): carries only sensory infor-mation from the periphery to the spinal cord. C. Dorsal root ganglion (I, III): a collection of cell bodies of sensory nn. that passes over the dorsal root.
D. Ventral root (I, III): carries only motor nervefibers/axons from the spinal cord to the periphery. These are also called lower motor neurons (LMN).
E. Dorsal branch (I, II): roughly innervate the structures dorsally to the transverse processes (motor: epaxial muscles of the trunk and sensory: skin over the back). The dorsal branches like the ventral ones form plexuses by joining
A. Spinal n.
D. Ventr. root
E. Dors. br.
F. Ventr. br.
Motor n. (LMN,
Sensory n.
Sensory nerve cell
I. Cervical spinal nerve, cranial view, schematic
lower motor neuron)
each other. F. Ventral branch (I, II): roughly supplies structures ventral to the transverse processes (motor: hypaxial mm., trunk mm., almost all of the muscles of the limbs; and sensory: the skin). As the spinal nerves and the dorsal branches, theycarrybothsensoryandmotorfibers/axons.
Locate on an articulated skeleton and in the illustrations: G. Intervertebral foramina (I, II): the openings where spinal nerves exit the vertebral column to branch into dorsal and ventral branches.
Note in the illustrations:H. Cervical spinal nn. (II): 8 pairs of nerves. Most leave the vertebral column through the intervertebral foramina (see "Back" chapter for more).
I. Phrenic n. (II): formed by ventral branches of cervical nerves 5-7 (± 4) and passes through the thorax to the diaphragm.
J. Brachial plexus (II): the network formed from the ventral branches of the last few cervical and first one or two tho-racic spinal nn. It gives rise to the named nerves supplying the thoracic limb and adjacent areas.
B. Dors. (sensory) root
C. Dors. root ganglion
G
REFLEX ARC (III): the simplest impulse pathway, it is an involuntaryresponsetoasensorystimulus.Mostreflexarcs involve a sensory neuron, an interneuron, and a motor neuron. This makes them multisynaptic (the patellar tap reflexlacksaninterneuron[monosynaptic]).Specializedreceptors at the end of sensory neurons receive a stimulus (e.g., pin prick), resulting in an impulse (nerve action poten-tial/NAP)intothespinalcordtosynapseonaninterneuronwhich synapses on a motor neuron. The motor neuron stimulates a receptor organ (muscle or gland) to complete thereflex(e.g.,withdrawalfromthestimulus).
F. Stimulus (III): a change in the environment (e.g., pin prick/noxiousstimulus).
G. Receptor (III): of a sensory neuron (e.g., pain detector in
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C1, C2....T1: Cervical spinal n. 1, 2.... Thoracic spinal n. 1
1. ^ Great auricular n. (II): the large cuta-neous branch of the ventral branch of second cervical n. (C2) that passes craniodorsally to the ear. It is sensory to the skin of the neck, ear, and back of the head.
2. Transverse colli n. (II): the other large cutaneous branch of the ventral branch of second cervical n. C2 that crosses ventrally over the cranial part of the neck.
3. Occipital n. (II): the dorsal branch of the second cervical n. (C2)
4. ̂ Ventral branches of the cervical nn. (II): join to form the cervical plexus and the last couplejoinwiththefirstfewthoracicventralbranches to form the brachial plexus.
5. Cervical plexus (II): the joining of many ventral branches of the cervical nn., supplying structures in the neck.
6. ^Intercostobrachial nn. (II): branches of the second and third intercostal nn. (ventral branches of T2-3) that pass in the wall of the thorax and wrap around the caudal arm to reach the skin of the caudolateral part of the brachium to which they supply cutaneous sensory innervation.
7. Cervical loop (ansa cervicalis) (II): com-munication between the ventral branch of the 1st cervical n. and the small descending branch of the hypoglossal n.
a. Suprascapular n. (C6-7) (II)b. Subscapular nn. (C6-8) (II)c. Musculocutaneous n. (C7-8) (II)d. Axillary n. (C8) (II)e. Radial n. (C7-T1) (II)f. Median n.(C8-T1/T2) (II)g. Ulnar n. (C8-T1) (II)
IX. Glossopharyngeal n. (II): cranial n. 9# X. Vagus n. (II): cranial n. 10XI. Accessory n. (II): cranial n. 11XII. Hypoglossal n. (II): cranial n. 12
II. Cervical nn. & brachial plexus, lateral view, schematic
C2C1
C3 C4C5 C6 C7 C8 T1
T2
I. Phrenic n.
a b
d c
e f g
G. Intervertebral foramina
1*
2*
3*
4*
A. Spinal n.
E. Dors. br.
J. Brachial plexus
5*
6*
X
IX
XII
XI. Accessory n.
7*
H. Cervical spinal nn.
*Definedinthelegend
a digit of paw) that responds to change (stimulus-flame)bygeneratinganim-pulse (NAP).
H. Sensory (afferent) neuron (III): carries a sensory impulses to the CNS.
I. Interneuron or association neuron (III): located in the spinal cord, connects a sensory neuron with a motor neuron. It can also connect with other neurons and send information up to the brain (so whenthereflexisover,itcanbeperceivedand commented on, “ouch!”).
J. Motor (efferent) neuron or lower motor neuron (I. III): carries an impulse to an effectororgan.
K. Effector (target) organ (III): the muscle or gland innervated by a motor neuron which reacts to the stimulus (e.g., pulling away from the pin).
K. Effector organ(muscle or gland)
H. Sensory neuron I. Interneuron
J. Motor neuron
G. Receptor
F. Stimulus
III. Reflex arch, schematic
A. Nerve (spinal n.)
B
D
C
CERVICAL & BRACHIAL PLEXUSES - 2
F. Ventr. br.
#Arabic numerals are used because the authors think they help with learning especially for those with learning disorders, so sorry..
II Thoracic Limb
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As you dissect the vessels, nerves, and lymph nodes of the thoracic limb; dissect the extrinsic muscles of the thoracic limb.
Locate and isolate the brachiocephalicus m. (A) com-pletely separate the it from the body and the omotransver-sarius m. Do this completely or you will not be able to find the following structures.
Transect the brachiocephalicus m. (cervical and mastoid parts) where it crosses over the cephalic v. Reflect the muscle and note the large nerve entering its deep sur-face.
• VentralbranchofC6spinaln./cleidobrachialis n.: enters the brachiocephalicus m.
Cut this nerve to complete the reflection of the parts of the brachiocephalic m. (This means all the way to the ear and dorsal neck! Just do it!)
Dissect the parts of the trapezius m. (B) and cut them 1/2" (1 cm) from their attachments to the spine of the scapula and reflect them as you did for the right limb.
Identify and dissect the omotransversarius m. (D) that arises from the acromion and travels cranially up the neck deep to the brachiocephalic m. If you haven't completely reflected the brachiocephalic m., do it now, separating it from the omotransversarius m.
Bluntly dissect the fascia along the dorsal border of the omotransversarius m. where it was under the brachio-cephalic m. to locate:
1. Accessory n. (cranialn.11[XI],spinal accessory n.) (II, III):acranialn.(comingoffthebraininthecranium)thatexits from the skull and travels on the dorsal side of the omotransversarius m. to innervate, among others, the trapezius m.
Transect the omotransversarius m. 1/2" (one cm) from the acromion of the scapula and reflect it.
2. Superficial cervical (prescapular) lymph nodes (I, II): the usually two (one-four) large glandular structures cranial to the shoulder under the omotransversarius m. They drain thesuperficialandlateralneckregion,lateralsurfaceofthethoraciclimb,andcaudalhead(ear).Theirefferentspass to the venous angle inside the thoracic inlet (external jugular, tracheal duct, or tracheal trunks).
3. Superficialcervicala.(II):locatednearandsupplyingthesuperficialcervicallnn.andthecaudalneck.Followitbackuntil it disappears into the thorax (you will dissect its origin from the subclavian a. in the Thorax chapter).
Reflect any of the cutaneous trunci m. left on the body to the axilla (armpit) and transect it 1/2" (one cm) from the caudal border of the arm. Discard the detached piece.
Dissect and transect the superficial and deep (F) pectoral mm. 1/4" (.5 cm) from their attachments to the humerus (don't leave too much with the limb).
4. Accessory axillary lymph node (I): may or may not be present on the dorsal border of the deep pectoral m. in the caudalaxilla(armpit).Ifpresent,itsefferentductsdrains
NECK - 1the thoracic wall, shoulder and arm, and cranial mammary glandstotheaxillarylymphnode(FigI[5]).
Transect the latissimus dorsi m. (C) 2" from its brachial attachment.
Abduct the limb and move the part of the deep pectoral m. medially to observe:
• Vessels and nerves of the axilla: fascia-obscured, they cross the axilla.
Abduct the limb and identify the serratus ventralis m. Cut through the rhomboideus and serratus ventralis (G) mm. close to the scapula as you abduct and twist the limb. Cut all attachments until the limb is connected to the trunk by only the brachial plexus and axillary vessels.
Bluntly separate the vessels and nerves crossing the axilla and locate:
5. Axillary lymph node(s) (I): the glandular structure (usually just one) associated with the vessels and nerves of the axilla. It drains the deep thoracic limb, thoracic wall, and cranial mammaryglands. Itsefferentductspasstothevenousangle inside the thoracic inlet (external jugular, tracheal duct, or tracheal trunks). It, with the accessory axillary node if present, make up the axillary lymphocenter.
4. ± Accessory axillary ln.
5. Axillary ln.
2. Supf. cervical lnn.
I. Lymph centers of the shoulder region, lateral view, schematic
Venous angle
b*
c
c*
a*
b* Thoracic duct
%Roman numeral(s) in parentheses after a structure indicate in which illustration(s) they are labeled. Absence indicates they are in all illustrations.
II Thoracic Limb
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NECK - 2
II. Superficial neck & thoracic limb, brachiocephalic & omotransversarius mm. cut, lateral view
a. ^Sternal lymph node (I): also drains the cranial mammary glands
b. Afferentlymphvessels/ducts (I): enter a lymph node
c. Efferentducts (I): pass from a lymph noded. Cephalic v. (II) e. Jugular v. (II)f. Radial n. (C7-T1) deep branch (II) fi. Superficial branch of radial n. g. Lateral thoracic n. (II, III) h. ^Great auricular n. (II)i. Transverse colli n. (II)j. Ventral branch of the cervical n. (II)
k. Cranial lateral cutaneous brachial n. (II) from axillary n.
m. Omobrachialis v. (II) n. Intercostobrachial n. (II)o. Median cubital v. (II) p. Thoracodorsal vessels & n. (II)q. Cutaneous vessels and nerves (II)r. Supraspinatus m. (II)s. Splenius m. (II) t. Sternocephalicus m. (II)u. Deltoid m. (II) v. Lateral head of triceps brachii m. (II)
Review these extrinsic muscles as you find the nerves of the area p50-3.
Extrinsic mm. of the limb A. Brachiocephalicus m. (II)B. Trapezius m (II)C. Latissimus dorsi m. (II)D. Omotransversarius m. (II)E. Rhomboid m. (II)F. Deep pectoral m. (II)G. Serratus ventralis m. (II)
2. Supf. cervical lnn.
3. Supf. cervical a.
m1. Accessory n.
A
D
B
n
A
e
d
m
g
C
G
E
F
h
i
kf
fi
j
o
p
G
q
q
r
q
t
u
v
q
s
* Definedinthelegend
II Thoracic Limb
82
S SM
A
Overview page, not dissection page: Use the schematics on these two pages to orient yourself as you dissect out the nerves of the thoracic limb and refer back to them constantly. Learn the names that are written in the legends (A-M). Those that are numbered are best used for reference, for anatomy trivia quizzes, or if your instructor demands.
Be able to trace the paths of the nerves in relationship to an articulated skeletal limb.
Dissection continues after the following page.
A. Suprascapular n.
B. Subscapular n.
Ci. Med. cutaneous antebrachial n.
D. Axillary n.
E. Radial n.
Ei. Deep br. Eii. Supf. br.
G. Median n.
F. Ulnar n.
Fi. Dorsal br.
M. Lat. thoracic n.
I, K, L. Digital nn.
C. Musculocutaneous n.
A. Suprascapular n. (C6-7)(I)B. Subscapular n. (C6-8)(I)C. Musculocutaneous n. (C7-8)(I, II)Ci. Median cutaneous antebrachial n.
(I, II)D. Axillary n. (C8)(I)E. Radial n. (C7-T1)(I, II)Ei. Deep branch of the radial n. (mo-
F. Ulnar n. (C8-T1)Fi. Dorsal branch of the ulnar n.
G Median n. (C8-T1/T2)(I)I. Digital nn., dorsal and palmar (II,
III) - K. Axial digital nn. (II, III)- L. Abaxial digital nn. (II, III)
M. Lateral thoracic n. (C8-T1) (I)
Brachial plexusCranial plexusSuprascapular n. Subscapular n.
SS MAR MU (Memory Aid: the order of the main nerves in the brachial plexus
to help in lesion localization if there are problems
Middle part of plexus Musculocutaneous n. Axillary n. Radial n.
Caudal part of plexus Median n. Ulna n.
R
M U
I. Nerves of the thoracic limb, medial view, schematic
1*2*
4*
5*
6*
9*
C6C7C8T1T2
8*
10*
3*
13*
12*
11*a
15*
19*
E. Radial n.
7*
NERVES - THORACIC LIMB - 1
a
a
*Definedinthelegend
1. ^Proximal muscular branch of the muscu-locutaneous n. (I): supplies the coracobrachialis and biceps brachii mm.
2. Communicating branch (I): between the musculocutaneous and median nn. near the elbow in carnivores.
3. Distal muscular branch of the musculocutane-ous n. (I)
4. Cranial lateral cutaneous brachial n. (I): a sensory branch of the axillary n. to the lateral arm
5. Cranial cutaneous antebrachial n. (I): the continuation of the cranial lateral cutaneous brachial n. (axillary n.), sensory to the cranial antebrachium
6. ^Cranial pectoral nn. (C6-8) (I): motor to the superficialpectoralm.
7. ^Long thoracic n. (C7&/orC8)(I):runsoverand innervates the serratus ventralis m.
8. ^Thoracodorsal n. (C8) (I): motor to the latis-simus dorsi m.
9. ^Caudal pectoral nn. (C6-8) (I): motor to the deep pectoral m.
14*
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Caudal part of plexus Median n. Ulna n.
I. Nerves of the thoracic limb, medial view, schematic
C. Musculocutaneous n.
Fi. Dors. br. of ulnar n.
Ci. Medial cutaneous antebrachial n.
E. Radial n.
E'. Deep branch
E''. Superficial branch
F. Ulnar n.
15*
G. Median n.
II. Nerves of the left forepaw, cranial view, schematic
12*
F
E
III. Nerves of the left forepaw, caudal view, schematic
13*
I
II
III IV
V
a
I
II
IIIIV
V
16*
18*
I. Dorsal digital nn.
K. Axial digital nn. K. Axial digital nn.L. Abaxial digital nn.
L. Abaxial digital nn.
17*
16. Palmar branch of the ulnar n. (III)
• Palmar digital nn. in the metacarpus: di-videdintosuperficialanddeepsetsarisingfromthemedian and ulnar nn. The dorsal digital nn. (14) only havesuperficialnn.
- 17. Palmar common digital nn.:superficialbranches in the metacarpus that bifurcate in the digits (ex. 19i).Superficialbranchesthatdon'tbifurcatehavethe same digital name in the metacarpus (ex. 19ii).
- 18. Palmar metacarpal nn.: deep branches of the ulnar n. (palmar branch) located next to the metacarpal bones
19. Proper or not: proper may be added to the name of a dorsal or palmar digital nn. (in the digital area) that arises from a bifurcation of a common digital nn., and
isnotproperifitdoesn'tarisefromabifurcation.- 19i. Properpalmar/dorsal(axial)digitaln. V (IV):
- 19ii. Abaxial palmar/dorsal digital n.V (IV): both palmar and dorsal carry only ulnar n.fibers.
20. Dorsal branches and plexuses of the spinal nerves C6-T2 (I) roughly innervate the structures dorsal to the transverse processes of the vertebrae
a. ^Muscular branches: include all visible branches of each nerve that pass to muscles
11*
NERVES - THORACIC LIMB - 2
a
10. Lateral caudal cutaneous brachial n. (I): from radial n., sensory to the skin over the lateral arm
11. Lateral cutaneous antebrachial n. (I): of the radial n., sensory to craniolateral forearm
12. Medial branch ofthesuperficialradialn.(I,II):traveling with the cephalic v., sensory to dorsum of the paw
13. Lateral branch of the superficial radial n. (I,II): travels with the cephalic v., sensory to dorsum of the paw
14. Dorsal common digital nn.: located in the metacarpus, there are no dorsal metacarpal nn.
15. ̂ Caudal cutaneous antebrachial n. (I): from ulnar n., sensory to the caudal forearm.
19ii*
19i*
19ii*
19i*
14*
*Definedinlightlegend (LPI: low priority item)^ More important (LPI)
Axis
II Thoracic Limb
84
BRACHIAL PLEXUS - 1
1. Supraspinatus m. 2. Subscapularis m. 3. Coracobrachialis m.4. Biceps brachii m.5. Teres major m.6-7. Triceps brachii m. 6. Long head 7. Medial head
8. Tensor fascia antebrachii m.9. Pronator teres m. 10. Latissimus dorsi m. 11. Superficial pectoral m. 12. Deep pectoral m. 13. Cutaneous trunci m. (maybe with skin)14. Serratus ventralis m.
Dissect these muscles as you find the nerves of the area p50-60.
Plan for Identifying Nerves (Memorize yesterday!)Suprascapular n. (B) between the supraspinatus & subscapularis mm.Subscapular n. (C): into the subscapularis m. Musculocutaneous n. (D): beside & into the coracobrachialis & biceps brachii mm.Axillary n. (I): between the subscapularis & teres major mm.Radial n. (J): medially: dives into the triceps m. - laterally: under the lateral head (triceps) -Superficialbranches: onthesidesofthecephalicv. - Deep branch: into the extensor mm. of the forearm.Median & ulnar nn.: together in the brachium.Ulnar n. (K): runs to the ulna (olecranon) in arm. -caudal:undertheextensor&flexorcarpiulnarismm.
in forearm. Median n. (L): down the medial arm & forearm. Digital nn. (p102): sides of the digitsThoracodorsaln.(E): intothelatissimusdorsim.Long thoracic n. (G): over the serratus ventralis m. Lateral thoracic n.(F): passes to the cutaneous trunci m.(don'tlocate,butknow).
*Definedinthelegend
2
B. Suprascapular n.
I. Axillary n.
D. Musculocutaneous n.*
L. Median n. K. Ulnar n.
J. Radial n.
C. Subscapular n.
H. Phrenic n. 4
k
j
Ji. Superficial radial n. (med. br.)
5
h
A. Brachial plexus
E.Thoracodorsaln.
F. Lat. thoracic n.
g
9
m
3
7
6
i
1
11
14
12
f*
G. Long thoracic n.
C6
C7C8
T1
T2
12
10
11
8
a*
b*
c*d*
e
Di. Med. cutaneous antebrachial n.
I. Nerves of the brachial plexus, left axilla, ventral view
II Thoracic Limb
85
BRACHIAL PLEXUS - 2
@ Textbook of Veterinary Anatomy, Dyce- Sack-Wensing# Underlined structures: often hard to find, so don't, instead note them in
the illustration; and, if bold, know why (they may not be tagged on the lab test, but will be part of the lecture test).
Poke a blunt probe between the vessels and nerves and repeatedly move it back and forth in the direction of these structures. Repeat this over and over, and over, and over ... until individual vessels and nerves appear. Use a thumb forceps to pick away fat and fascia as it clumps up. Then pick a single structure, strip it, and dissect it to its termination to name it.
Dissect and identify the medial muscles of the shoulder and the arm as a review (see box opposite), and to help name the arteries and nerves entering them, while dissecting the vessels and nerves. Bluntly dissect and identify the network of nerves that come together and then separate into individual nerves in the axilla.
A. Brachial plexus (C6,7,8,&T1±C5&/orT2):thenetworkformed from the ventral branches of the last few cervical andfirstoneortwothoracicspinalnn.(C6-T2±C5)Theventral branches emerge ventral to the scalenus m. to reach the axilla, where they further divide and communicate with eachothertoformthebrachialplexus.Fromthebrachialplexus, peripheral named nerves extend to innervate the thoracic limb, adjacent muscles and skin, and, via the phrenic n., the diaphragm.
"Get a plan": to identify the nerves, memorize the "Plan of Forelimb Nerves" NOW. As you locate a nerve, find where it travels, usually either into a specific muscle or between two muscles. From this information and the "Plan", name the nerve. Do this during lab quizzes with confidence!
"Several branches...bare mention of their names and desti-nation is all that is required" (as other anatomists include: long thoracic, thoracolumbar, cranial and caudal pectoral, and subscapular - these are not bolded in this text).
B. Suprascapular n. (C6-7)@: dives between the supraspina-tus and the subscapularis mm. and crosses the scapular notch to innervate the infraspinatus and supraspinatus mm.
Optional: Remove a wedge of the supraspinatus m. over the suprascapular n. to follow its course across the neck of the scapula to reach the infraspinatus m.
C. Subscapular n. (C6-7): one or two branches that dive into the subscapularis m. (2)
D. Musculocutaneous n. (C6-8): runs along the medial side of the coracobrachialis m. and the biceps brachii which it innervates, along with the brachialis m.
See the musculocutaneous n. branches dive into the biceps brachii proximally and distally to identify it. Di. Medial cutaneous antebrachial n. (I): cutaneous branch of the musculocutaneous n. to the skin of the medial side of the forearm to the level of the carpus (do not dissect).
E.Thoracodorsal n. (C8): passes to the latissimus dorsi m. (10) with the thoracodorsal vessels.
F. Lateral thoracic n.# (C8-T2):clinicallysignificant,itextendscaudally with the lateral thoracic a. and v. to supply the cutaneous trunci m. (13), do not dissect.
G. Longthoracicn.:thelarge,flat,palewhitestructurelyingon and supplying the serratus ventralis m.
H. Phrenic n.: formed by ventral branches of the fourth or fifthtoseventh cervical nn, it passes through the thorax to the diaphragm (dissect later).
I. Axillary n. (C7-8): crosses the axilla and dives, with the subscapular vessels, between and into the subscapularis and teres major mm. It passes behind the humerus to reach the lateral side of the arm to innervate the deltoideus, teres major,andteresminormm.Itgivesoffthecraniolateralcutaneous brachial n.
J-L: see following pages or chart opposite.
a. ^Proximal muscular branch of the musculocutaneous n.: supplies the coracobrachialis and biceps brachii mm.
b. Distal muscular branch of the musculocutaneous n. c. Communicating branch: the connection between the musculocutane-
ous and median nn. just proximal to the elbow.d. ^Caudal cutaneous antebrachial n.: from ulnar., p88e. ^Cranial pectoral nn. (C6-8): supply the superficial pectoral m.f. ^Caudal pectoral nn. (C8-T2): innervate the deep pectoral m.g. Sternocephalicus m. (I)h. Axillary a. and v. (I)i. External jugular v. (I)j. Extensor carpi radialis m.k. Brachiocephalicus m. (I)m. Flexor carpi ulnaris m.
arises, not from the brachial plexus, but from intercostal nn.[T2-3]).Therefore,feelingonthecaudolaterallimbsometimes gives owners a false sense of hope. - Incomplete avulsion: you may be able to determine which part of the plexus is avulsed by loss of muscular function using SS MAR MU and by loss of sensation
todifferentareasofthelimb,butitis doubtful if this will change your treatment.
• Suprascapular n. damage ("Sweeney"): most common in horses, it causes paralysis of the
CLINICAL:• Brachial plexus avulsion: results in a flaccid limb. The limb will be insensitive to pain, except on the cau-dolateral arm, which is innervated by the intercostobrachial n. (which
infraspinatus and supraspinatus mm., resulting in lateral instability of the shoulder joint ("joint slip"). With time, the muscle atrophy corrects the instability, but results in a prominent scapular spine.
• Panniculus/cutaneous trunci response: mediated by lateral thoracic n. (motor) and the lumbar and thoracic spinal nn. (sensory) helps to localize T3-L4 spinal cord damage (see p90).
II Thoracic Limb
86
THORACIC LIMB NERVES - 1
NERVE MOTOR: muscles SENSORY: skin area
Suprascapular n. (B) .............. M: supraspinatus & infraspinatus mm. None Subscapular n. (C)..................... M: subscapularis m. NonePectoral nn. (a, b)...................... M: pectoral m. NoneLong thoracic n. (G)................ M: serratus ventralis m. None Thoracodorsal n. (E)............... M: latissimus dorsi m. None Lateral thoracic n. (F).......... M: cutaneous trunci m. & deep pectoral m. None Musculocutaneous n. (D)....... M: flexors of the elbow (coracobrachialis, biceps brachii, & brachialis mm.) - Medial cutaneous .............................................................................................. S: medial forearm (overlapped by others) antebrachial n. (Di) (clinical: horse for nerve blocks)Axillary n. (I)......................... M: flexors of the shoulder (teres major, teres minor & deltoideus mm.) Cranial lateral cutaneous brachial n. (g)............................................................... .................. S: lateral side of the arm Cranial cutaneous antebrachial n. (h)........................................................................................ S: shares the cranial surface of the forearm w/ other nn. (radial & musculocutaneous) Radial n. (J)....................... M: extensors of the elbow, carpus & digits (triceps brachii, anconeus, tensor fasciae antebrachii mm.) - Deep br. (Ji) M: extensors of the carpus & digits (extensor carpi radialis, common digital extensor, lat. digital extensor, lat.
ulnar, oblique carpal extensor, & supinator mm.) - Superficial branch (Jii) ....................................................................................... S: lateral forearm & dorsal manus/paw . Medial br. (i) S: dorsal paw . Lateral br. (j) S: dorsal paw .. Lateral cutaneous antebrachial n. (k) S: lateral forearmUlnar n. (K) ............................ M: some flexors of forearm & muscles of manus (flexor carpi ulnaris, interosseous mm.) - Caudal cutaneous antebrachial n. (f).....................................................................S: caudolateral forearm - Dorsal branch (p 89).......................................................................................S: dorsolateral metacarpus & 5th digitMedian n. (L)....................... M: most of flexors of forearm ................................S: w/ ulnar n. to ca. forearm & palmar pawIntercostobrachial n. (M) S: lateral side of the arm (Not from the brachial plexus, but from intercostal nn. T2-3)
a. ^Cranial pectoral n. (I)b. ^Caudal pectoral n. (I)c. ^Proximal muscular branch of the
musculocutaneous n. (I) d. Distal muscular branch of the muscu-
locutaneous n. (I) e. Communicating/anastomotic
branch (I): connects musculocutaneous and median nn. just proximal to the elbow.
f. ^Caudal cutaneous antebrachial n.: a branch of the ulnar n. arising proximal to the elbow and traveling caudally with the col-lateral ulnar a. over the medial surface of the olecranon. It supplies sensory innervation to the caudal forearm. (It may have been removed with the skin).
g. Cranial lateral cutaneous brachial n. (II): a sensory branch of the axillary n. appear-ing just caudal to the deltoideus m., it supplies sensation to the lateral side of the arm and caudal scapular region.
h. Cranial cutaneous antebrachial n. (II): the continuation of the cranial lateral cutaneous brachial n. (axillary n.).
i. Medial branch ofthesuperficialradialn. (I): travels with the cephalic v.
j. Lateral branchofthesuperficialradialn.(II): travels with the cephalic v.
k. Lateral cutaneous antebrachial n. (II): from radial, it is sensory to the skin covering the extensor mm. in the forearm (craniolateral surface).
I. Nerves & vessels of the shoulder, medial view
A. Brachial plexus
C. Subscapular n.
D. Musculocutaneous n.
I. Axillary n.J. Radial n.
K. Ulnar n.
L. Median n.
E.Thoracodorsaln.B. Suprascapular n.
C6C7
C8T1
T2
c
de*
f*
Jii, i* 14
5
6
7
8
9
16
14
15
17
11
12ii
12ii
13
F. Lateral thoracic n.
G. Long thoracic n. a
Di. Med. cutaneous antebrachial n.
22
b
II Thoracic Limb
87
I. Nerves & vessels of the shoulder, medial view
THORACIC LIMB NERVES - 2
A-I: see preceding pages or chart opposite. Move to the lateral side of the left shoulder to dissect the axillary n. and the deltoid m. (see box).
Dissect and transect the two parts of the deltoideus m. very close to the acromion of the scapula (1/1000") and reflect the parts to observe the axillary n.:
Relocate the axillary n. in the axilla (medially). Pull on it and see it move where it enters the deltoid m. on the lateral side of the limb.
J. Radial n. (C7-T2):thelarge,clinicallysignificantnervecross-ing the axilla to dive between and into the long and medial heads of the triceps brachii m.. It innervates the extensors of
the limb (arm and antebrachium). Move to the lateral side of the left shoulder to dissect the radial n. and the brachialis m.
Bluntly dissect the distal side of the lateral head of the triceps brachii m. to locate:
The radial n. passing with the collateral radial a. on the brachialis m., which is in the brachial groove, to reach the lateralsideofthearm.Itbecomessuperfi-cial under the distal border of the lateral head triceps brachii m.
Transect the lateral head of the triceps and reflect its parts. Note the radial n. on the brachial m. that divides near the elbow, into: J'.Deepbranch(ramusprofundus)(II):motortoex-tensors of the forearm.
J''. Superficial branches (II): sensory to the dorsal paw travelling on either side of the cephalic v.
Flip the limb over to see the medial side. Locate:K, L. Ulnar and median nn. (C8-T2)(I): arise together from the brachial plexus and, as a nerve bundle, travel with the brachial vessels in the arm, caudal to the musculocutaneous n. It bifurcates proximal to the elbow into the median and ulnar nn., both which innervate the flexors of the forearm.
K. Ulnar n. (C8-T2)(I): separates from the median n. in the distal brachium and passes toward the ulna (olecranon process).
L. Median n. (C8-T2)(I): continues down the medial side of the arm and forearm with the brachial and median vessels respectively. It crosses over the me-dial collateral ligament to reach the forearm, where it dives under the pronator teres m. (we will continue to dissect it later).
M. Intercostobrachial nn.: lateral cutaneous branches of the second and third intercostal nn. (not from the brachial plexus) that supply the lateral skin of the arm/brachium over the long head of the tricepsbrachii m.
1. Cephalic v. 2. Axillobrachial v. (II)3. Omobrachial v. (II)4. Median cubital v. (I)5. Supraspinatus m. 6. Subscapularis m. (I)7. Teres major m. (I)8. Coracobrachialis m. (I)9. Biceps brachii m.10. Brachialis m. (II)11. Tensor fascia antebrachii m. (I)12. Triceps brachii m. - 12i. Long head
- 12ii. Medial head (I) - 12iii. Lateral head (II)
13. Latissimus dorsi m. 14. Brachiocephalic m.15. Pronator teres m. (I) 16. SDF m. (I) 17. Flexor carpi ulnaris m. (I) 18. Trapezius m. (II) 19. Omotransversarius m. (II)20. Infraspinatus m. (II) 21. Teres minor m. (II) 22. Superficial pectoral m.23. Extensor carpi ulnaris m. (II)
II. Nerves & vessels of the shoulder, lateral view
J. Radial n.Fi
Fii
Accessory n.
1 12iii
Deltoid m.
k*
g*
J", h*
Jii, j*
2 3
57
10
12iii
12i
13
14
23
18
19
20
2122
23
22
I. Axillary n.
M. Intercosto- brachial nn.
K, f*
• Intercostobrachial n. and complete brachial plexus avulsion: sensation on the lateral arm is due to this nerve and not nerves of the brachial plexus, sosensationtoarmdoesn'tindicatereturn to function.
CLINICAL: • Radial n. paralysis (more on p90): supplies all the extensors of the thoracic limb. - "High paralysis" results in
an inability to stand on the limb, along with "knuckling over" (see below).
- "Low paralysis" doesn'tprevent standing, but causes "knuckling over." see p90)
II Thoracic Limb
88
A. Median n.
15
B. Ulnar n.
1*
Incise the skin longitudinally down the caudal aspect of the manus medial to the carpal pad and through the middle of the metacarpal pad.
Cut around the base of the dew claw. Reflect the skin distally to the metacarpal pad, removing the carpal pad with the skin. Leave the skin and digital pad on the dew claw. Leave the skin attached (or save the skin if removed) so you can wrap it around the limb each day.
Di. Med. cutaneous antebrachial n.
10
14
18
Cii. Supf. radial br. (med.)
13
16
9
NERVES - FOREARM - 1
17
11
1. ^Caudal cutaneous antebrachial n.: a branch of the ulnar n. arising proximal to the elbow and traveling caudally with the collateral ulnar a. over the medial surface of the olecranon. It sup-plies sensory innervation to the caudal forearm. (It may have been removed with the skin).
2. ^Palmar branch of the ulnar n. (II): extends distally on the palmar side of the paw, supplying, along with the median n., most of the muscles of the forepaw and sensation (from a communicating branch to the median n.) to the palmar aspect of the forepaw.
3, 4. Medial (II) and lateral branches of the superficialbranch of the radial n.: terminal branches arising in the proximal forearm that pass with the medial and lateral branches of the super-ficialbrachialaa.oneithersideofthecephalicv.tothecarpus.Theysupply sensory innervation to the cranial surface of the antebrachium and the dorsum of the forepaw.
5. Lateral cutaneous antebrachial n. (II): a branch of the larger lateralbranchofthesuperficialbranchoftheradialn.totheskinofthe lateral side of the forearm.
6. Cranial lateral cutaneous brachial n. (II): a sensory branch of the axillary n. appearing just caudal to the deltoid m.
7. Cranial cutaneous antebrachial n. (II): the continuation of
12
D. Musculocutaneous n.
h
i. SDF
a. Extensor carpi radialis m.f. Pronator
teres m.
g
the cranial lateral cutaneous brachial n. (axillary n.). It is sensory to the proximocraniolateral side of the antebrachiumoverlappingthesuperficialbranchesof the radial n. and the musculocutaneous n.
8. Intercostobrachial n. (II) 9. Cephalic v. (I) 10. Brachial a. (I)11. Median cubital v. (I) 12.Superficialbrachiala. (I) 13. Cranial superficial antebrachial a.,
medial branch (I)14. Median a. (I)
15. Accessory cephalic v. (I) 16. Collateral ulnar a. (I)17. Biceps brachii m.18. Flexor retinaculum (I)19. Deltoid m. (II) 20-21. Triceps brachii m. 20. Long head (II)21. Lateral head (cut) (II)
22. Brachialis m. (II) 23. Tensor fascial antebrachii (I)24. Anconeus m.
h
I. Nerves & vessels of the forearm, medial view
3*
23
Review (dissect and identify) the extensor and flexors mm. of the forearm as you dissect the nerves (p63-71):
a. Extensor carpi radialis m.b. Common digital extensor m. (II)c. Lateral digital extensor m. (II) d. Extensor carpi ulnaris (lateral ulnar) m. (I)e. Oblique carpal extensor (abductor pollicis longus) m. (II)f. Pronator teres m. (cut) (I)g. Flexor carpi ulnaris m.h. Flexor carpi radialis m. (cut) (I)i. SDF (superficial digital flexor) m. (I)j. DDF (deep digital flexor) m. (not shown)k. Supinator m. (not shown)
Relocate the median n. in the arm:A. Median n. (I): separates from the ulnar n. proxi-mal to the elbow to pass deep to the pronator teres m.. It gives, with the ulnar n., motor branches to the flexor mm. of the forearm.
Transect the pronator teres m. and separate the flexor carpi radialis and deep digital flexor mm. to follow the median nerve distally.
The median n. continues with the median a. and v. into the forearm, then passes through the carpal canal to the manus. Here it supplies sensory innervation to the palmar surface of the paw, along with the ulnar n. Do not dissect the digital branches of the median n.
II Thoracic Limb
89
a. Extensor carpi radialis m.
Bi. Dors. br. of the ulnar n.
C. Radial n.Ci. Deep br.
Cii. Supf. brs.
B. Ulnar n.
NERVES - FOREARM - 2
II. Nerves of the forearm, lateral view
19
20
8
6
21
22
13
17
7*3*
4*
5*
1
24
e
b. Common digital extensor m.
c
d. Extensor carpi ulnaris m.
g. Flexor carpi ulnaris m.
2*
B. Ulnar n.: along with the median n., innervates the flexors of the forearm and, by itself, the interosseous mm. of the manus. It separates from the median n. in the distal arm and goes toward the ulna. Passing under the ulnar head of theflexorcarpiulnarism.,itinnervatestwoflexormuscles(flexorcarpiulnarism.andpartofthedeepdigitalflexorm.).Itcontinuesdeeptotheflexorcarpiulnarism.andsuperficialtotheDDFm.tothecarpus,whereitbifurcatesinto dorsal and palmar branches.(Don'tdissect,butnotethem in the illustrations).Bi. Dorsal branch of the ulnar n.(don'tdissect)(II):travelsforward (cranially) and distally to supply sensation to the lateral (abaxial) side of the metacarpus and 5th digit.
Now note the nerve passing distal to the lateral head of the triceps brachii m.
C. Radial n. (II): after entering the triceps brachii m. on the medial side It travels distally on the brachialis m. with the collateral radial a. to reach the lateral side. It becomes superficialunderthedistalborderofthelateral head of the triceps brachii m. Near the elbow, it divides into deep and superficial branches.
Trace the radial n. proximally and verify with a probe, that it is a continuation of the radial n. on the medial side of the arm. Follow it distally until it divides into a superficial (Cii) and a:- Ci. Deep branch of the radial n. (II): passes under the cranial edge of the extensor carpi radialis m. to innervate the extensors of the carpus and digits.
Dissect the extensor carpi radialis and common and lat-eral digital extensors mm. and cut through the extensor retinaculum to the metacarpal region.
Follow the deep branch into the extensor mm.Dissect around the cephalic v. to follow: - Cii. Superficial branch of the radial n.: bifurcates into lateral and medial branches that pass distally on either side of the cephalic v. These branches supply sensation to the lateral forearm and the dorsal aspect of the paw.
Relocate:D. Musculocutaneous n. (I): runs along the biceps brachii m. in the arm separated from the median and ulnar nn. - Di. Medial cutaneous antebrachial n. (I): (note in the il-lustration, not on your cadaver) arises from the musculo-cutaneous n. and supplies the skin on the medial side of the forearm. It is usually removed with the skin during dissection.
E. Digital nn. (II):(don'tdissect)many,inthemanustheyare divided into dorsal or palmar; and in the digit, further divided into axial or abaxial and have the Roman numeral of the digit they supply (e.g., abaxial dorsal digital n. III).
CLINICAL: • Medial cutaneous antebrachial and dorsal branchoftheulnarnn.:oflittleclinicalsignifi-cance in the dog, they may be involved in nerve blocks to diagnose lameness in horses.
E. Digital nn.
*Definedinthelegend
a
II Thoracic Limb
90
CUTANEOUS INNERVATION - CLINICAL 1
Cutaneous innervation:onlymemorizeradialandulnarnn.,astheresthavelittleclinicalsignificance.1. Axillary n. (cranial cutaneous brachial n.): lateral side of the arm. 2. Axillary n. (cranial cutaneous antebrachial n.): cranial surface of the forearm.3. Musculocutaneous n. (medial cutaneous antebrachial n.): medial surface of the forearm.4. Ulnar n. (caudal cutaneous antebrachial n.): caudal surface of the forearm.5. Radial n.(superficialbranches):lateralforearmand dorsal paw.6. Ulnar n. (dorsal branch): lateral paw (digit 5). 7. Ulnar & median nn.: caudal forearm & palmar paw.
8. Intercostobrachial nn.: lateral skin of the arm.
Read this page, there is no dissection involved.Cutaneous areas of innervation (CA): the areas of skin innervatedbyanerve.Thecutaneousareasofdifferentnerves overlap (overlap zones - OZ). • Dermatome or autonomous zone* (AZ): the area of the skin innervated by only one nerve. Absence of feeling fromanautonomouszoneindicateswhatspecificnervehas been damaged.
• Radial n. (superficial branch): innervates the dorsal paw and is the most clinically important dermatome, helping diagnose its damage. Besides the radial n., the other sensory areas are interesting, but probably not used in clinics.
• Ulnar n. (dorsal branch): sensory to the lateral digit, (which is often asked on national boards).
• Intercostobrachial nn.: lateral cutaneous branches of the second and third intercostal nn. (not from the brachial plexus) that supply the lateral skin of the arm over the long head of the triceps brachii m.
to stand on the limb, along with "knuckling over" (see below).
CLINICAL:• Clinical significance of the thoracic limb nerves: only a few situations (i.e., radial n. paralysis, complete brachial plexus avulsion, and possibly supraspinatus n. damage) are significant to the general small animal veterinarypractitioner.Damagetoanyoftheotherspecificnervesshows very subtle signs, if any, due to compensation. What is more important than cutaneous zones is know-ing where the nerves pass in order to avoid them during surgery.Morenervesbecomeclinicallysignificantinthehorse when doing nerve blocks to localize a lameness.
• Radial n.: supplies all the extensors of the thoracic limb. - Path of the radial n.: passes into the triceps mm. then curves around the humerus in the brachial groove to the lateral side to become su-perficialwhereitisvulnerableto
trauma from the side or damage to a humeral fractured.
- "High" paralysis: paralyses the tri-ceps brachii m., preventing extension of the elbow resulting in an inability
- "Low" paralysis (damage below triceps innervation) would permit standing on the limb, but eliminates the ability to extend the distal limb, resulting in "knuckling over" and dragging the limb on its dorsum. Animalslearntocompensatebyflippingtheir limb forward to extend the digits and plant the limb when moving.
• Panniculus/cutaneous trunci response: used to localize thoracic spinal cord damage. It is mediated by the lateral thoracic n. that passes from the bra-chial plexus and ex-tends caudally with the lateral thoracic a. and v. to supply the cutaneous trunci m.
(sensation and motor loss)• Intercostobrachial n.: sensation toarm,sodoesn'tindicatereturnto function after brachial plexus avulsion (see p85).
• Suprascapular n. damage ("Sweeney"): causes paralysis
of the infraspinatus and supraspinatus mm. (see p85).
• Dorsal branch of the ulnar n. and medial cutaneous an-tebrachial n.: may be blocked to help diagnose lameness in the horse (see p89).
Sensationfromthelateraltrunk(flyorpinch)passesupover the thoracic and lumbar spinal ventral branches which pass caudoventrally to the spinal cord, up the cord to the cell bodies of the lateral thoracic n. Motor fiberspasstothecutaneoustruncim.- Absence of the panniculus response cau-dally which then appears cranial to a point localizes the lesion to the spinal cord.
• Brachial plexus avulsion = flaccid limb. In incomplete avulsion use SS MAR MU
II Thoracic Limb
91
Cutaneous sensation of the forelimb• Arm- Lateral surface: Intercostobrachial nn. (8), axillary n. (cranial cutaneous brachial n.)(1)•Forearm:- Cranial surface: axillary n. (cranial cutaneous antebrachial n.)(2)- Medial surface: musculocutaneous n. (medial cutaneous antebrachial n.) (3)- Caudal surface: ulnar n. (caudal cutaneous antebrachial n.) (4)- Lateral surface proximally: radial n. (lateral cutaneous antebrachial n.) (5)- Lateral surface distally: radial n. (superficialbranch)(5)
• Manus:- Dorsal paw: radial n. (superficialbranch)(5)- Lateral paw (digit 5): ulnar n. (dorsal branch) (6)- Palmar paw - ulnar & median nn. (7)
5. Radial n.
8. Intercostobrachial nn.
7
6. Ulnar n.
53
2
1
4
CUTANEOUS INNERVATION - CLINICAL 2
Cutaneous innervation of the thoracic limb, lateral view
II Thoracic Limb
92
I. Arteries of left arm, medial view
ARTERIES - THORACIC LIMB - 1
B. Axillary a.*
C. Subscapular a.*
D. Brachial a.*
Axillary ln.
Accessory axillary ln.
2*
1*
6*4*
3*
5
8*
9*
10*
13*12i
12*
11*
A. Subclavian a.
Median a.
a
b
c
ef
fi
g
h
i
d
j
k
nm
A. SUBCLAVIAN A. (see text opposite page)1. Superficialcervicala.: supplies the muscles of thescapulaandtheshoulder,superficialcervicallymphnode,andsuperficialmm.ofthebaseoftheneck
- 2. Suprascapular a.: passes between supraspina-tus and subscapular mm. with the suprascapular n. to supply the scapula and the supraspinatus m.
B. AXILLARY A. see text opposite page.3. ̂ Externalthoracica.: the branch of the axillary a. supplyingthesuperficialpectoralm.,itisaccompaniedby the cranial pectoral nn.
4. Lateral thoracic a.: runs caudolaterally with the lateral thoracic n. over the thoracic wall on the dorsal border of the deep pectoral m. to supply the axillary lymph node, deep pectoral, latissimus dorsi, cutaneous trunci mm., and the thoracic mammary glands.
C. SUBSCAPULAR A. (see text opposite page)
5. ^Thoracodorsal a.: arises from the start of the subscapular a. and extends caudally with its satellite v. and n. to the latissimus dorsi m.
6. ̂ Caudalcircumflexhumerala.: arises from the subscapular a. and travels behind the caudal side of the humerus to anastomose with the cranial circumflexhumerala. It is themainsupply to thetriceps brachii m.
7. Collateral radial a. (II)%: accompanies the radial n. on the brachial m. which it supplies
8.^ Cranialcircumflexhumerala.: can arise from either the axillary or subscapular a. It travels in front of the humerus and anastomoses with the caudal circumflexhumerala.
D. BRACHIAL A.: (see text opposite page)9. ̂ Deep brachial a.: passes with the radial n. into
the triceps brachii m. which they both supply
10.^ Bicipital a.: passes into the distal end of the biceps brachii m. which it supplies
11.^ Collateral ulnar a.: travels with the ulnar n. (caudal cutaneous antebrachial n.) toward the elbow which it supplies.
12. ^Superficialbrachiala.: branch of the bra-chial a., it passes from the brachium to the cranial surfaceoftheantebrachiumwhereitgivesoffame-dialbranch,thencontinuesasthecranialsuperficialantebrachial a.
- 12i.Cranialsuperficialantebrachiala.- 12ii. Medial branch: other branch of 12
13. ̂ Transverse cubital a.: transverses the elbow cranially under the biceps brachii m. to supply the elbow.
14. Recurrent ulnar a.: supplies the forearm flexors.
a. Subscapularis m. (I)%
b. Supraspinatus m. (I)c. Teres major m. (I)d. Biceps brachii m.e. Tensor fascia antebrachii m. (I)f. Triceps brachii m., long head (I) - fi. Medial head (I)g. Latissimus dorsi m. (I) h. Pectoral mm. (I) i. Brachiocephalicus m. j. Extensor carpi radialis m. k. Pronator teres (cut) (I)m. Superficial digital flexor m. (I) n. Flexor carpi ulnaris m. (I)
E. Common interosseous a.*
12ii
Cephalic v.
*Definedintextorlegend^ More important (LPI)
II Thoracic Limb
93
Transect the teres major m. and reflect it to see:C. Subscapular a.: the large branch of the axillary a. passing caudodorsally along the border of the scapula, between the subscapularis and teres major mm. It becomes subcutane-ous at the caudal angle of the scapula.
D. Brachial a.: the continuation of the axillary a. on the me-dial aspect of the arm/brachiumroughlypasttheoriginof the subscapular a.# It continues as the median a. in the forearmaftergivingoffthecommoninterosseousa.Thebrachial a. travels on the medial side of the arm with the musculocutaneous n., median n., and brachial v. between the biceps brachii and the triceps brachii mm.
Transect the pronator teres m. and reflect its parts (if it hasn't already been done for the median n.), to follow the brachial a. past the elbow.
Pull the brachial a. medially and bluntly locate its last branch diving deep between the two bones of the forearm (ulna and radius):
E. Common interosseous a.: the last branch of the brachial a. (NAV), it dives through the interosseous space between the ra-dius and ulna. and branches into cranial and caudal interosseous branches
# The conjoined tendon of the teres major and latissimus dorsi mm. is the actual demarcation between the axillary and brachial aa.
ARTERIES - THORACIC LIMB - 2
We will now start learning the circulatory system by dissecting out the arteries of the thoracic limb. They come from the heart in the thorax by way of the subclavian aa.
Arterial patterns are variable. The main branches usually follow the text books, but lesser branches will vary con-siderably from dog to dog. Even though origins may vary, the area supplied is consistent. Veins vary even more than arteries, nerves less, and lymphatics the most.
Therefore, identify a vessel nerve by the structure it supplies, not where it arises.
Dissect the following vessels of the arm and antebrachium to their terminations.
Locate the artery crossing the axilla (axillary a.) and follow it back to the first rib to its parent artery:
A. Subclavian a.: arises in the chest on the left side directly from the aorta and on the right from the brachiocephalic trunk (which arises from the aorta). It passes cranially out of the thorax through the thoracic inlet, then around the 1st rib to become the axillary a.
Relocate the large artery crossing the axilla:B. AXILLARY A.: the continuation of the subclavian a. af-terthefirstrib,itcrossestheaxilla(armpit)tosupplythestructures of the shoulder and continues as the brachial a. in the arm.#
D. Brachial a.
Median a.
C. Subscapular a.*
E. Common interosseous a.*
B. Axillary a.*
Ca. interosseous a.
1*
2*
3*
4*
5*
6*
7*
8*
9*
10*
13*
11*
12*
14*
A. Subclavian a.*
12i
12ii
II. Arteries of left arm, medial view, schematic
II Thoracic Limb
94
Relocate: A. Common interosseous a. (I, IV): the last branch of the brachial a.
Cut longitudinally the proximal end of the pronator quadratus m. and, with the end of a scalpel handle, scrape the muscle off the ulna and radius to locate:
B Caudal interosseous a. (IV): the continuation of the com-mon interosseous a. passing distally in the space between the caudal ulna and radius.
C. Median a. (I, IV): the direct continuation of the brachial a. in the forearm after the common interosseous a. It continues to the manus as the main arterial supply of the manus.
Do not dissect the following:D-G. Digital aa. (III, IV): on the dorsal and palmar sides of the digits and metacarpus. They can be further divided into dorsal and palmar branches which can also be divided in the digits into axial and abaxial aa.-D, E. Palmar and dorsal digital aa. (III, IV): are further divided into superficial (common digital aa.) and deep sets(metacarpal aa.) in the metacarpus. They join at the digits and then branch into medial and lateral branches that pass on the axial and abaxial sides of the digits. The palmar digital aa.arisefromthesuperficialanddeeppalmararches.
- F, G. Axial and abaxial digital aa. (palmar or dorsal). (III, IV): further division of the digital arteries once they reach the digits depending on which side of the digit they pass on.
Relocate and trace: H. Cephalic v. (I, II): arises on the palmar aspect of the paw and passes proximally, wrapping around the medial side of the forearm to be joined by the accessory cephalic v. It then continues up the cranial side of the forearm.
I. Accessory cephalic v. (I): arising on the dorsum of the paw, it passes proximally to empty into the cephalic v.
J. Median cubital v. (I): connects the cephalic and brachial vv.
I. Arteries of left forearm, medial view
ARTERIES - THORACIC LIMB - 1
II. Arteries of left forearm, lateral view
Brachial a.
H. Cephalic v.*
A. Common interosseous a.*
C. Median a.*
I. Accessory cephalic v.*
H. Cephalic v.*
Radial n.
i
16*
4*
5i*
5ii*
Deep br.
m
j
k
aa
b
bii
n
e
f
h
g
h
d
d
c
f
j
7*
5*
c
Median n.
Median n.
Ulnar n.
Ulnar n.
Supf. br. J. Median cubital v.*
3*
CLINICAL:• Cephalic v.: the most common site of venipuncture. Realize that the super-ficialbranchesoftheradialn.andthe
• Caudal interosseous a.:can'tbeoccludedwithatour-niquet in the mid-forearm as it is protected
between the radius and ulna. It is also prone to injury if the forearm is fractured.
branchesofthesuperficialbrachiala.travelwithit.
II Thoracic Limb
95
*Definedinthetextorlegend
A. COMMON INTEROSSEOUS A. (I, III) see text
1. Ulnar a. (IV): arises from the common interosseous a. and travels distally with the ulnar n.
B. Caudal interosseous a. (IV) see text2. ^Cranial interosseous a. (III, IV): continues
through the interosseous space between the radius andulnaafterthecaudalinterosseousa.isgivenoff.Once on the cranial side of the ulna and radius, it extends distally.
C. MEDIAN A. (I, IV) see text^3. ^Deep antebrachial a. (I, IV): runs caudally fromthemediana. tosupply theflexorsideof theforelimb.
4. ^Radial a. (I, III, IV): runs cranial to the median a. on the radius.
5.^ Superficial brachial a. (I, III): branch of brachial a. see p 92
- 5i. ^Cranial superficial antebrachial a. (III): : along with the medial branch (12ii) courses withthecephalicv.andbranchesofthesuperficialradial n. to supply the dorsum of the paw via dorsal common digital aa.
- ^5ii. Medial branch (III)6. ^Transverse cubital a. (III) see p 927. ̂ Collateral ulnar a. (I, IV) travels with the ulnar
n. (caudal cutaneous antebrachial n.) toward the elbow which it supplies.
8. Recurrent ulnar a. (IV): see p929. Dorsal carpal rete (III): network on dorsal
carpusARTERIES - FOREPAW/metapodium (meta-
carpus and digits): divided into palmar and dorsal branches,whichcanbefurtherdividedintosuperficialand deep.
D, Palmar digital aa: dividedintosuperficialanddeepsetsarisingfromthesuperficialanddeeppalmararches (15)
- 10. ^Palmar common digital aa. (IV): the mainsupplytothedigits,superficialbranchesthatbifurcateinthedigits.Superficialbranchesthatdon'tbifurcate have their digital name in the metacarpus also (ex. 14ii).
- 11. ̂ Palmar metacarpal aa. (IV) deep branches located next to the metacarpal bones
• Dorsal branches: also divided - 12. ^Dorsal common digital aa. (III): su-perficialbranches
- 13. ̂ Dorsal metacarpal aa. (III): deep branches near the metacarpal bones
14. Proper or not: proper may be added to a digital aa. in the digital area that arises from a bifurcation ofacommondigitalaa.,andisnotifitdoesn'tarisefrom a bifurcation.- 14i. Properpalmar/dorsal(axial)digital
a. V (III, IV):
ARTERIES - THORACIC LIMB - 2
III & IV. Left forearm & manus, III.Cranial/dorsalview, IV.Caudal/palmarview, schematic
- 14ii. Abaxialpalmar/dorsaldigitala.V(III, IV)
15. Superficialanddeeppalmar arches (IV)
a. Biceps brachii m. (I, II)b. Triceps brachii m., long head (I, II) - bii. Lateral head (II) c. Extensor carpi radialis m. (I, II)d. Pronator teres (cut) (I)e. Superficial digital flexor m. (I) f. Flexor carpi ulnaris m. (I)g. Extensor carpi ulnaris m. (ulnaris lat-
eralis) m. (II)h. Flexor carpi radialis m. (I)i. Caudal cutaneous antebrachial n. (ulnar n.) (II)j.Medialbranch(superficialbranch,radial
n. (I)k. Lateral branch (of superficial branch,radial n.) (II)
m. Lateral cutaneous antebrachial n. (II)n. Dorsal branch of ulnar n. (II)
Med. side
Lat. side
D. Brachial a.
6*
C
A. Common interosseous a.*
B. Ca. interosseous a.
C. Median a.*
5*
12*
13*
11*
10*
7*
Brachial a.
1*
2*
3*
4*
2* Med. side
4*
5i* 5ii*
8*
E. Abaxial dors. digital aa. D. Axial dors. digital aa.
E. Abaxial palm. digital aa.
D. Axial palm. digital aa.
9*
15
14i*
14ii*
14i*
14ii*
Digital aa.
Light legend (LPI, lower priority items)^ More important (LPI)
Axis
II Thoracic Limb
96
THORACIC LIMB PALPATION - 1Palpate the regions of the thoracic limb and the bone(s) in each:
• Shoulder: area around the scapula and humeral joint.• Brachium or arm: area containing the humerus.• Elbow/cubital region: area where humerus, radius, and ulna articulate.
• Antebrachium: area containing the ulna and radius.• Manus: area containing the carpal, metacarpal, digital, and sesamoid bones.
Palpate on the live animal the following structures:A. Spine of the scapula:pressandrunyourfingertipsata right angle over the scapula.
N. Metacarpal bones: palpate distal to the carpus. O. Digits and phalanges: palpate at the end of the limb. P. Digital joints (metacarpophalangeal joints, proximal and distal interdigital joints):locatebyflexingandextendingthe digits
Q. Claws: check for length, imagine clipping. R-S-T. Pads of the dog/cat:- R. Carpal pad: located palmar to the carpus. - S. Metacarpal: locate this heart-shaped padonthepalmar/plantar surface at the level of the metacarpophalangeal joints.
- T. Digital pads: locate these pads on the distal end of each digit.
U. Dew claw or paradigit: medial side of the limb. Muscles: stand or lean over the animal and palpate the re-gions of the limb on both side of the animal at the same time. Compare the sides for any lesions or abnormalities.
1. Superficial cervical lymph nodes: retract the limb and runyourfingersfromtheshoulderupthenecktofeelthelarge lumps at the level of the acromion.
2. Axillary lymph node: not palpable unless enlarged, it is located on the medial side of the shoulder.
3. Accessory axillary lymph node: occasionally is present caudal to the shoulder on the chest wall at the level of the olecranon.
4. Tendon of the biceps brachii m.:first,locatethegreater tubercleofthehumerusthenpushyourfingersmediallyto feel the tendon in the bicipital groove. It is covered by a continuation of the joint capsule (synovial sheath) which willfillwithpalpablefluidifthetendon,sheathorshoulderjoint capsule are injured.
Palpate vessels and nerves:5. Pulse of the brachial a.: palpated on the medial side of the arm between the biceps brachii and the medial head of the triceps brachii mm.
6. Ulnar n.: press from cranial to caudal just caudal to the medial epicondyle to feel the nerve "pop" under your finger.
7. Radial n.: palpate just past the distal border of the lateral head of the triceps brachii m. on the brachialis m. from proximal to distal to feel the pop of the
byflexionandextension.- Antebrachiocarpal joint: palpate the dorsal surface as youflexthecarpusandnoteitopensmorethanthedistaltwo carpal joints.
- Carpal joints: the distal two communicate.M. Accessory carpal bone: locate on the lateral and palmar
B. Acromion: once the spine of the scapula is found, palpate down to theendofthescapulatofindtheacromion.
C. Point of the shoulder/greater tubercle: feel the most cranial aspect of the upper thoracic limb distal to the acromion.
D. Shoulder joint: locate its level between the acromion and the pointoftheshoulderbyflexingand extending it.
F. Elbow joint: locate it distal to the shoulderbyflexingandextendingthe elbow.
G, H. Lateral and medial epicon-dyles: feel the lateral and medial most points of the distal humerus just proximal to the elbow joint byrunningyourindexfingerandthumb up and down this area of the limb. Note the medial epicondyle projects further caudally thus preventing medial luxation of the elbow.
I. Point of the elbow/olecranon (process): locate the large process proximocaudal to the elbow joint. It is at the level of the 5th ICS (intercostal space) in the standing dog.
J. Styloidprocessoftheradius:maximallyflextheantebra-
superficialbranchoftheradialn.Test of the nervous system• Proprioception placing: an easy check is to stand the animal on the dorsum of the paw. Normal animals will quickly replace the paw in the correctposition.Failuredoesn'tlocal-izethelesiontoaspecificareabutdoeslocalize it to the nervous system.
• Extensor carpi radialis reflex: a stretch (myotatic) reflex that tests the radialn., it roots, and spinal cord segments C7-T2. Place the animal in lateral recumbency, support the elbowwiththeelbowandcarpusflexed,andtaptheexten-sor muscle just distal to the elbow. Normally the carpus willextend.Thisisthemostreliablemyotaticreflexoftheforelimb,butstilllessreliablethanthepatellarreflexofthe
chiocarpal joint and palpate the point on the distal end of the radius on the medial side of thelimb(ifnotflexed,theradialcarpalbonewill be felt instead).
K. Styloid process of the ulna: palpate the distal end of the ulna on the lateral side of the limb.
L. Carpus/carpal joints: locate distal to the elbow
side of the carpus under the carpalpad.Flexandextendthecarpus while palpating this area. This is a lateral/palmar landmark for radiographs of the limb.
II Thoracic Limb
97
THORACIC LIMB PALPATION - 2
I. Palpable structures of the thoracic limb, lateral view
• Joint blocks: injection to anaesthetize the joint to localize where lameness is, this is more commonly done in horses. - Shoulder block: place needle through the deltoid m. between the acromion
and greater tubercle cranial to the tendon of the infraspinatus m. -Elbowjointblock:inserttheneedlebetweenthelateralepicondyleand
the olecranon through the anconeus m. - Antebrachiocarpaljointblock:flexthecarpusandinsertaneedleinto
the proximal depression (antebrachiocarpal joint) on either side of the extensor carpal radialis tendon. This only blocks the proximal carpal joint.-Middlecarpaljointblock:flexthecarpusandinsertaneedleintothe
depression distal to the antebrachiocarpal joint on either side of the extensor carpal radialis tendon. This blocks both the distal 2 of the three carpal joints.
across the medial and cranial surface of the elbow. -Compressthelimbwhilemovingyourfin-ger or thumb slightly lateral to straighten the cephalic v. in the forearm.
- Hold the back of the elbow with your
Radial n.
Ulnar n.
• Bicepsreflex:tapthe insertion of biceps brachii and brachialis mm. on the cranial side of the elbow to elicit flexionoftheelbowtocheckthemusculocutaneousn. (not reliable).
P. Digital joints
A. Spine of the scapula
C. Point of the shoulder
B. Acromion
D. Shoulder joint
4. Tendon of biceps brachii m.
F. Elbow joint
H. Lat. epicondyle
G. Med. epicondyle
I. Point of elbow
J. Styloid process of radius
K. Styloid process of ulna
L. Carpus/carpal joints
M. Accessory carpal bone
N. Metacarpal bones
O. Digits & phalanges
Metacarpophalangeal joint
Prox. interdigital joint
Dist. interdigital joint
R. Carpal pad
S. Metacarpal pad
5. Pulse - brachial a.
6. Ulnar n.
7. Radial n.
T. Digital pad
W. Cephalic v.
Q. Claw
U. Dew claw
2
1. Supf. cervical lnn.
3
thumborfingertopreventjerkingofthelimb.- Veterinarian: palpate distally to locate the fluid-filled
11 Radial n. - autonomous zone: pinch the dorsum of the paw.
12 Ulnar n. - autonomous zone: pinch the lateral digit (V) of the paw.
• RAISE THE CEPHALIC VEIN for veni-puncture: an assistant and a veterinarian.-Assistant:placeyourindexfingerorthumb
II Thoracic Limb
98
VIEWS OF THE THORACIC LIMB: the most common:- Lat (mediolateral) view of limb bones and joints: out-lines/silhouettesthecranial and caudal surfaces of the bones. Place the affected limbon the cassette, so it isusually shot from medial to lateral.
- Craniocaudal (caudocranial) or dorsopalmar views (pal-marodorsal) (anterior-posterior [AP%]) view: outlines/silhouettes the medial and lateral structures of the limb.
• Long bones of the limbs: always include the proximal and distal joints in the radiograph.
• Joints of the limbs: center the joint on the cassette.• Comparisonfilms:taketheoppositelimbifthereisaques-tion as to what you are seeing, and compare the two.
Evaluating radiographs of the limbs:recognizedifferentanatomical variations for the bones (German Shepherd humeruscomparedtoachondrodystrophicdog[Dachs-hund]).Followthecortexandseeifitthinsorthickensorif there are breaks in it.
Put up radiographs of the bones and joints of the thoracic limb on a viewing screen. Use individual and articulated bones while viewing radiographs, identify the following.
1. Scapula(I,II):accessoryossificationcenterofthecaudalaspect of the scapula.- 2. Glenoid cavity (I, IV): outline, note not a straight line. - 3. Spine (I, II): check for fractures on the CrCa view. - 4. Acromion (I, II): distal end of spine. - 5. Supraglenoid tubercle (I, II): anossification center,origin of biceps brachii m.
6. Clavicle: seen in cats, it is absent (usually) or rudimentary
in the dog, if present it may be seen in radiographs.7. Humerus (II, III, IV, V): craniocaudal and lateral views.- 8. Head of the humerus (II, III, IV, I): smooth and round, withnoflattening,directedcaudally.
- 9. Greater tubercle (III, IV, V): laterocranial structure.- 10. Lesser tubercle (IV, V): medial structure. - 11. Humeral condyle (III, IV, VI): whole distal end of humerus, there is only 1. . 12. Medial epicondyle (IV, VI, VII) silhouetted in both the craniocaudal and lateral projections.
. 13. Lateral epicondyle (VI): silhouetted only in the cran-iocaudal projection.
SHOULDER JOINT/scapulohumeral or humeral joint: standard views: lateral and caudocranial views. Remember tolookatallthefilm,noticingneck,cervicalvertebrae,air-filledtrachea,ribs,andlungfields(air-filled).
14. Joint space (IV, V, VI): should be of equal width all around the humeral head.
ELBOW JOINT: a flexed lateral view (VII) is added to standard craniocaudal and lateral. 15. Radius (IV, VI, VII): cranial in lateral view. 16. Olecranon (III, IV, VI): the point of the elbow.-17. Trochlear notch (VI)): cups the humerus-18. Anconeal process(VII):ossificationcenterununitedifnot joined by 6 months, best seen in flexed lateral view.
-19. Medial coronoid process (VII) large distal end of notch: clinicallysignificancehardtoseeinradiographs.
20. Supinator sesamoid bone: seen occasionally in the dog on the lateral side of the elbow joint.
I. Scapula, Craniocaudal view (taken CaCr)
a
7
Radiographs: Dr. Small-wood, NCS University
RA
DIO
LOG
Y - T
LIM
B BO
NES
- 1
3. Spine
1. Scapula
4. Acromion
5. Supraglenoid tubercle
2. Glenoid cavity
II. Shoulder, lat view, Not atruescapularviewasdoesn'tinclude all of the bone5
Lat. surface
Med. surface
Ca. edge
8
7 Review bones: p33-5
II Thoracic Limb
99
RADIOLOGY - THORACIC LIMB BONES - 2
13. Lat. epicondyle
IV. Humerus, Elbow, lat view
1. Supraglenoid tubercle
12. Med. epicondyle
VI. Elbow, CrCa view
VII. Elbow,Flexed lateral view
14. Joint space 15. Radius
17. Trochlear notch
16
a. Supraspinous fossa (II)b. Deltoid tuberosity (IV)c. Brachial groove (IV)d. Lateral coronoid processe. Olecranon process
19
e
V. Shoulder, craniocaudal view
14
11
15
15
c
b
12
9. Greater tubercle
19. Med. coronoid process
d
e
18. Anconeal process
16III. Humerus, craniocaudal view
18
8. Head
2 Glenoid cavity
4
12
14
Med. surface
11. Condyle
2
16
10. Lesser tubercle
7. Humerus
VII
III IVV
VI
8
II Thoracic Limb
100
2. Styloid process (radius)
4. Olecranon5. Trochlear notch 6. Anconeal process
8. Styloid process (ulna)
RADIOLOGY - THORACIC LIMB BONES - 3
1. Radius (I, II): curves cranially in lateral view.2. Styloid process of radius (II): on medial side.3. Ulna (I, II): caudal in a lateral view.8. Styloid process of the ulna (I): lateral side.
9. Interosseous space (II)10. CARPUS: proximal and distal rows.10. Cr, Radial carpal bone (III, IV, V, VI): medial side10. Cu, Ulnar carpal bone (III, IV, V): lateral side
10. Ca, Accessory carpal bone (III, IV, V, VI): landmark for the palmar and lateral sides of the carpus.
10. C1-4, Carpal bones (IV): numbered medial to lateral 11. Sesamoid bone of the oblique carpal extensor (IV): medial side of the carpus, not a chip fracture
16. Intermetacarpal joints (V)17. Carpal pad (III):outlined/silhouettedinLat18. Mc 1-5, Metacarpal bones I-V (III, IV, V)DIGITS: 1-5 or I-V. 19. Dew claw or paradigit (IV)20. Proximal sesamoid bones (III, IV)21. Dorsal sesamoid bones (III): lateral view 22. Proximal phalanx/P1 (III, IV)23. Middle phalanx/ P2 (III, IV)
10. C2
RADIOLOGY - THORACIC LIMB BONES - 4
24. Distal phalanx/P3 (III, IV)25. Ungual process (III, IV)26. Ungual crest (IV): only tangential side ("hook") is seen 27. Horny claw (III)28. Metacarpophalangeal joint (VIII)29. Proximal interphalangeal joint (VIII)30. Distal interphalangeal joint (VIII)31. Metacarpal pad (IV)32. Digital pad (III)
Pinky naming obliques: • Clue: accessory carpal is located palmar and lateral•DecidethefilmisNOTaDPorlateral,thus,anoblique
- Lateral (LM): the accessory carpal on palmar side- DP (dorsal palmar view): the accessory is overlapped • Eyeball and pinky: check if the accessory carpal is slightly
highlighted or overlapped-Flexyourlittlefinger(representingtheaccessorycarpal,asit
is on the lateral and palmar side)-Pointyouroppositeindexfinger(representstheprimarybeam)
at either the medial or lateral side of the dorsal surface of your hand.Lookdownthefingertomatchtheamountofthepinkyseenwiththeaccessorycarpalonthefilm,eitherhighlightedoroverlapped. Name the oblique by the entrance and exit points of the beam always starting with dorsal. . Dorsomedial-palmarolateral oblique (DMPLO), or. Dorsolateral-palmaromedial oblique (DLPMO).
Ca
Cr
Cu
C3
10. C1C4
18. Mc 5
Mc 4
17. Mc1
Mc 2
18. Mc 3
II
IIIIV
V
22. P123. P2
24. P3
31. Metacarpal pad
IV. Left manus, DP view
VI. Carpus, DMPLO, dorso-medial/palmarolateraloblique view, slight
V. Carpus, DLPMO, dorso-lateral/palmaromedialoblique view
Radiographs:Dr.EdSmallwood,NCSU
19. Dew claw
11. Oblique carpal extensor sesamoid
20. Prox. palmar sesamoid bones
crest
25. Ungual process
10. Accessory carpal
Dorsolat. surface
Radiograph: Dr. Mariona Makara
Cu
18. Mc 2
Cr
Palmaromed. surface
Palmarolat. surface
Lat. surface
Med. surface
26. Ungual
16
16
II Thoracic Limb
102
Joint mouse
RADIOGRAPHS - THORACIC LIMBDist. Physis - ulna
Dist. physis - radius
Fractures
Dist. epiphysis Mc 5
Prox. epiphysis P1, digit 4
Prox. Physis P1, digit 1
I. Manus, young, dorsal view
CLINICAL:• Osteochondrosis (OC): seen in young, rapidly growing, large breeds. The shoulder is the #1 location. Radiographically, carti-lage is invisible, so check the subchondral bone for indications of cartilage damage (flatteningorcrateringofthecaudalaspect
YOUNG DOG - RADIOGRAPHS: are confusing especially of the manus or pes.
• Growth plate (physis): appears as a dark line easily confusedwithajoint.Inthemanus,firstlocatethedistalphalanx of a digit and the associated metacarpal bone, then locate the middle and proximal phalanges and their growth plates and epiphyses. At first use growth plate instead of physis during tests to avoid confusion with epiphysis.- Proximal and distal: don't forget to include when identifying. In the metacarpals, and proximal, and middle phalanges there is usually only the proximal is visible as the distal has closed.
• Epiphyses (sin. = epiphysis): distal ends of forming long bones. Include proximal and distal when identifying, give number of metacarpal bone or the phalanx, and for pha-langes the number of the digit for full credit on tests.
Crater & subchondral sclerosis
Anconeal process
of the humeral head with subchondral bone sclerosis (thickening/"whitening");seenbestinaLat radiograph.
around in the synovium, it is called a “joint mouse”.
• Ununited anconeal process: failure of the anconeal process to unite with the ulnabyfiveto 6 months of age. A straight or ragged radiolucent line is seen. There may be degenerative changes in the el-bow (DJD). The best view is the flexed
lateral elbow, which pulls the anconeal process out of the olecranon fossa of the humerus.
Dist. humeral physis
Prox. radial physis
Dist. radial physis
Dist. ulnar physis
Accessory carpal bone
Dist. physis of Mc5
Distal epiphysis - humerus
Prox. epiphysis- radius
Diaphysis - humerus
Metacarpophalan-geal joint
II. DP view, manus, puppy
I. Lat view, forearm, puppy
Dist. radial epiphysis
Distal epiphysis - ulna
Metaphysis
II Thoracic Limb
103
REGIONS:Shoulder: Scapula (clavicle absent or greatly
ventralis m.• Humerus- Neck of humerus- Brachial (musculospiral, spiral) groove: ca. to lat. - Lateral supracondylar crest: prox. from lat. epicondyle- Articular surface of the condyle: divided
. Trochlea: groove for trochlear notch
. Capitulum: for radial head - Supratrochlear foramen: ± in dog
- Base: proximal extremity of P1 & P2- Axial groove of P1: for Mc sagittal ridge - Head: distal trochlea of P1 & P2MUSCLES•Dorsalfibrousraphe: connective tissue where mm. from
both sides meet on dorsal midline• Thoracolumbar fascia•Extensorbranchofinterosseousm.• Branch of interosseous m.: to prox. sesamoid boneJOINTS• Glenohumeral ligaments (medial & lateral): thicken-
ings of joint capsule •Elbow- Tricipital (olecranon) bursa: over olecranon
• Carpus-Intercarpal joints: plane joints between individual
- Distal sesamoidean lig.: anchors sesamoidsNERVES• Great auricular n.: C2 to ear• Cervical plexus: joining of ventral brs. of cervical nn.• Intercostobrachial nn.: brs. of 2nd & 3rd intercostal nn.
(thoracic) to caudolateral brachium - sensory• Brachial plexus- Cranial pectoral nn. (C6-8): motor - supf. pectoral m. - Caudal pectoral nn. (C6-8): motor to the deep pectoral m. - Caudolateral cutaneous brachial n.: of radial n.,
sensory to lateral arm - Medial & lateral branches of superficialbranches
of radial n.: travel on sides of cephalic v. . Dorsal digital nn.:continuationofsuperficialradialnn.
pass on dorsal abaxial & axial sides of digits- Caudal cutaneous antebrachial n.: ulnar n. - sensory
to caudal forearm- Palmar branch of the ulnar n.: gives rise to palmar
metacarpal nn. - Axial & abaxial palmar digital nn.
• Dorsal branches & plexuses of spinal nn. C6-T2ARTERIES• Suprascapular a.: between supraspinatus & subscapular mm.,w/supraspinatusn.•Externalthoracic:tosuperficialpectoralm.• Lateral thoracic: to deep pectoral m. • Thoracodorsal a.: to latissimus dorsi m. •Caudalcircumflexhumerala.: around ca. humerus• Collateral radial a.: with radial n. in brachial groove•Cranialcircumflexa.: cr. to humerus• Deep brachial a.: to triceps brachii m.• Bicipital a.: to distal biceps brachii m.• Collateral ulnar a.: with ulnar n. toward ulna• Transverse cubital: transverses elbow deep to biceps
brachii m.•Superficialbrachiala.: with cephalic v. in forearm