1 Human Anatomy, McKinley & O'Loughlin Chapter 7 Lecture Outline: Axial Skeleton
7-2
Skeletal System
The bones of the skeleton form an internal framework to support soft tissues, protect vital organs, bear the body’s weight, and help us move.
Typically, there are 206 bones in an adult skeleton, although this number varies in some individuals.
A larger number of bones are present at birth, but the total number decreases with growth and maturity as some separate bones fuse.
7-3
Skeletal System
The axial skeleton is composed of the bones along the central axis of the body,
1. the skull
2. the vertebral column
3. the thoracic cage
4. Hyoid & auditory ossicles
The appendicular skeleton consists of the bones of the appendages
1. upper and lower limbs
2. the bones that hold the limbs to the trunk of the body.
7-6
The Skull
1. Cranial bones form the
rounded cranium, which
completely surrounds
and encloses the brain.
2. Facial bones form the
bones of the face. They
also
• protect the entrances
to the digestive and
respiratory systems as
well as
• provide attachment
sites for facial muscles
The human skull (Cranium, face) • The skull consists of 8
cranial bones and 14 facial
bones =22
• The facial bones are
i. Maxillae2
ii. Palatine bone2
iii. Nasal bone2
iv. Inferior nasal conchae2
v. Zygomatic bone2
vi. Lacrimal bone2
vii. Vomer1
viii.Mandible 1
8
Cranial bones 1. The occipital bone 1
2. The Parietal bone 2
3. The frontal bone 1
4. The temporal bone 2
5. The sphenoid bone 1
6. The ethmoid bone 1
The Occipital bone 1
• Inferior surfaces of the occipital bone contains a large
circular opening, the foramen magnum, which
connects the cranial cavity with the spinal cavity
enclosed by vertebral column.
• At occipital condyles the skull articulates with the first
cervical vertebra.
• Inside the skull the grooves follow the path of major
vessels. The ridges mark the attachment sites of the
meninges that stabilize and position the brain.
11
The Temporal bone 2
• Contributes to the
inferior and lateral
walls of the cranium.
• Contributes to the
Zygomatic arches of
the cheek; forms the
only articulation with
the mandible
• Temporomandibular joint (TMJ).
• Protect the sense organs
of the inner ear.
14
18
Insert Fig. 7.9 superior view of skull
•The sphenoid bone has median portion, known as the body of sphenoid bone, containing the sella turcica, which houses the pituitary gland as well as the paired paranasal sinuses, the sphenoidal sinuses. •Two greater wings and two lesser wings.
19
The ethmoid bone is an irregular shaped bone. Forms the roof of the nasal cavity It also forms part of the orbit.
20
The ethmoid has three parts: 1- the cribriform plate, which is perforated by foramina for the passage of the olfactory nerves. 2-the ethmoidal labyrinth, dominated by the superior nasal conchae, and middle nasal conchae. 3-the perpendicular plate
7-24
Sutures of the Skull
• Sutures are immovable fibrous joints that form the boundaries between the cranial bones.
• Dense regular connective tissue seals cranial bones firmly together at a suture.
• Allow the cranium to grow and expand during childhood.
• In adulthood, when cranial growth has stopped, the sutures fuse and are obliterated(destroyed)
Sutures
1. Coronal Suture: is a joint that separates the frontal and
parietal bones of the skull.
2. sagittal Suture: joint between the two parietal bones of
the skull.
3. Lambdoid Suture: is a joint on the posterior aspect of
the skull that connects the parietal with the occipital
bone.
4. Squamous Suture: One on each side of the skull.
between the parietal and temporal bones.
25
14 Facial bones are
1. Maxillae2
2. Palatine bone2
3. Nasal bone2
4. Inferior nasal conchae2
5. Zygomatic bone2
6. Lacrimal bone2
7. Vomer1
8. Mandible 1
29
30
upper palate of mouth or maxilla: two halves that are fused at the intermaxillary suture to form the upper jaw.
Nasal bone
3 pairs of nasal
conchae
Are scroll like bones,
(shaped like an
elongated sea-shell)
that protrudes into
the breathing
passage of the nose.
1. The inferior
2. The middle
3. The superior
Help swirl and filter air
before it passes into
the lung.
39
the zygomatic bone (cheekbone, malar bone) is a paired bone which articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone.
part of the lateral wall and floor of the orbit
45
The vomer is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones. The vomer forms the posterior part of the nasal septum.
7-47
The Mandible
• The lower jaw is
formed by the
mandible.
• The prominent
“chin” of the
mandible is called
the mental protuberance.
7-49
Cavities of
The Skull – The largest cavity
is the cranial
cavity, which
encloses,
cushions, and
supports the brain.
– The skull also has
several smaller
cavities, including
the orbits (eye
sockets), the oral
cavity (mouth), the
nasal cavity, and
the paranasal sinuses.
• the maxillary sinuses, are
under the eyes, in the
maxillary bones.
• the ethmoidal sinuses,
between the nose and the
eyes.
• the sphenoidal sinuses, in
the sphenoid bone.
behind the ethmoids
(sphenoidal sinuses
• the frontal sinuses,
superior to the eyes, in
the frontal bone.
52
7-54
Sinuses
Have a mucous lining that helps to humidify and warm inhaled air.
Cause these skull bones to be lighter.
Provide resonance to the voice.
57
The following bones Superior margin: frontal bone Inferior margin: maxilla, palatine and zygomatic Medial margin: frontal, lacrimal and ethmoid Lateral margin: zygomatic and sphenoi
7-59
Auditory Ossicles
Three tiny ear bones called auditory ossicles are housed within the temporal bone.
the malleus
the incus
the stapes
7-60
Hyoid Bone
Slender, curved bone located inferior to the skull between the mandible and the larynx (voice box).
Does not articulate with any other bone in the skeleton.
Serves as sites for attachment for tongue and larynx muscles and ligaments.
7-61
The Vertebral Column
• Composed of 26 bones, including
– 24 individual vertebrae and the
– fused vertebrae that form both the sacrum and the coccyx
C- Vertebral column.
• Vertebral column
consists of vertebrae
• Cervical vertebrae,
they are 7 in number,
• Thoracic vertebrae,
they are 12
• Lumber vertebrae,
they are 5 in number
• Sacral vertebrae
(sacrum), 5 fused
• Coccygeal vertebrae
3 or 4 united
63
The vertebral column has several functions:
1. Providing vertical support for the body
2. Supporting the weight of the head
3. Helping to maintain upright body position
4. Helping to transfer axial skeletal weight to the appendicular skeleton of the lower limbs
5. Housing and protecting the delicate spinal cord and providing a passageway for spinal nerves connecting to the spinal cord
67
Atlas: the 1st cervical vertebra has no body, and this is due to the fact that the body of the atlas has fused with that of the next vertebra
69
The movement of shaking or rotating the head left and right happens almost entirely at the joint between the atlas and the axis, the atlanto-axial joint.
The movement of nodding the head takes place predominantly through flexion and extension at the joint between the atlas and the occipital bone, the atlanto-occipital joint.
70
(sacrum 5 fused bodies united by four intervertebral disk;
Coccygeal vertebrae (coccyx), triangular tail bone united with sacrum by intervertebral disk (embryonic tail).
7-72
Three Main Spinal Curvature
Deformities
Kyphosis is an exaggerated thoracic curvature that is directed posteriorly, producing a “hunchback” look.
Lordosis is an exaggerated lumbar curvature, often called “swayback,” that is observed as a protrusion of the abdomen and buttocks.
Scoliosis is an abnormal lateral curvature that sometimes results during development when both the vertebral arch and body fail to form, or form incompletely, on one side of a vertebra.
scoliosis is the most common spinal curvature deformity.
B- Thorax / (bony thorax).
The rib cage or consists of:
A. 12 thoracic vertebral bodies posteriorly,
B. 12 pairs of ribs laterally
C. sternum (1) anteriorly.
Posterior View Of Ribs & Articulating Vertebrae
7-78
Thoracic Cage
Acts as a protective cage around vital organs, such as the heart, lungs, trachea, and esophagus.
Provides attachment points for many muscles supporting the pectoral girdles, the chest, the neck, the shoulders, the back, and the muscles involved in respiration.
7-80
Ribs
• Both males and females 12
pairs
– Ribs 1–7 are called true ribs.
At the anterior body wall, the
true ribs connect individually
to the sternum by separate
cartilaginous extensions
called costal cartilages.
– Ribs 8–12 are called false ribs
because their costal cartilages
do not attach directly to the
sternum. The costal cartilages
of ribs 8–10 fuse to the costal
cartilage of rib 7 and thus
indirectly articulate with the sternum.
– The last two pairs of false ribs
(ribs 11 and 12) are called
floating ribs because they
have no connection with the sternum.