Chapter 6: Skeletal System I
Dec 18, 2015
Chapter 6:Skeletal System I
Bernard Siegfried Albinus 1697 – 1770
Famous for his drawings in the work entitled Tables of the Skeleton and Muscles
of the Human Body published in 1747.
An example of Albinus’ drawings of the skeleton.
Figure 6.1 The bones and cartilages of the human skeleton.
Axial skeleton
Appendicular skeleton
Hyaline cartilages
Elastic cartilages
Fibrocartilages
Cartilages
Bones of skeleton
EpiglottisLarynx
TracheaCricoidcartilage Lung
Respiratory tube cartilagesin neck and thorax
ThyroidcartilageCartilage in
external earCartilages innose
ArticularCartilageof a joint
Costalcartilage
Cartilage inIntervertebraldisc
Pubicsymphysis
Articular cartilageof a joint
Meniscus (padlikecartilage inknee joint)
Figure 6.2 Classification of bones on the basis of shape.
(a) Long bone(humerus)
(b) Irregular bone(vertebra), rightlateral view
(d) Short bone(talus)
(c) Flat bone(sternum)
Figure 6.3a The structure of a long bone (humerus of arm).
Proximal epiphysis
(a)
Epiphyseal line
Articularcartilage
Periosteum
Spongy bone
Compact boneMedullarycavity (linedby endosteum)
Diaphysis
Distal epiphysis
(b)
Articularcartilage
Spongy bone
Compact bone
Figure 6.3b The structure of a long bone (humerus of arm).
(c)
Yellowbone marrow
Endosteum
Compact bone
Periosteum
Perforating(Sharpey’s) fibers
Nutrientarteries
Figure 6.3c The structure of a long bone (humerus of arm).
Figure 6.4 Comparison of different types of bone cells.
(a) Osteogenic cell (b) Osteoblast (c) Osteocyte
Stem cell Mature bone cellthat maintains the
bone matrix
Matrix-synthesizingcell responsiblefor bone growth
(d) Osteoclast
Bone-resorbing cell
Figure 6.5 Flat bones consist of a layer of spongy bone sandwiched between two thin layers of compact bone.
Compactbone
Trabeculae
Spongy bone(diploë)
Figure 6.9 Endochondral ossification in a long bone.
1 2 3 4 5 Bone collarforms aroundhyaline cartilagemodel.
Cartilage in thecenter of thediaphysis calcifiesand then developscavities.
The periostealbud invades theinternal cavitiesand spongy bonebegins to form.
The diaphysis elongatesand a medullary cavityforms as ossificationcontinues. Secondaryossification centers appearin the epiphyses inpreparation for stage 5.
The epiphysesossify. Whencompleted, hyalinecartilage remains onlyin the epiphysealplates and articularcartilages.
Hyalinecartilage
Area ofdeterioratingcartilage matrix
Epiphysealblood vessel
Spongyboneformation
Epiphysealplatecartilage
Secondaryossificationcenter
Bloodvessel ofperiostealbud
Medullarycavity
Articularcartilage
Childhood toadolescence
BirthWeek 9 Month 3
Spongybone
Bonecollar Primaryossificationcenter
Figure 6.11 Long bone growth and remodeling during youth.
Bone growth Bone remodeling
Articular cartilage
Epiphyseal plate
Cartilagegrows here.
Cartilageis replacedby bone here.
Cartilagegrows here.
Bone isresorbed here.
Bone isresorbed here.
Bone is addedby appositionalgrowth here. Cartilage
is replacedby bone here.
Figure 6.12 Parathyroid hormone (PTH) control of blood calcium levels.
Osteoclastsdegrade bonematrix and release Ca2+
into blood.
Parathyroidglands
Thyroidgland
Parathyroidglands releaseparathyroidhormone (PTH).
StimulusFalling bloodCa2+ levels
PTH
Calcium homeostasis of blood: 9–11 mg/100 mlBALANCEBALANCE
CalcitoninCalcitonin
Figure 6.13 Bone anatomy and bending stress.
Load here (body weight)
Head offemur
Compressionhere
Point ofno stress
Tensionhere
Figure 6.14 Vigorous exercise can lead to large increases in bone strength.
Cross-sectionaldimension of the humerusAddedbone matrixcounteractsadded stress
(b) Serving arm
(a)
Nonserving arm
Steel “Bone Cages” used to lengthen legs. These were originally developed in the Soviet Union in the 1950s to treat dwarfism.
Twelve-year-old boy with pituitary gigantism measuring 6'5" with his mother. Note the coarse facial features and prominent jaw.
An example of untreated acromegaly.
Chelation Therapy – intravenous administration of chemicals designed to absorb toxic substances that have accumulated in the body. Most notably used for exposure to heavy metals such as lead or mercury.
Figure 6.15 Stages in the healing of a bone fracture.
Hematoma Externalcallus
Bonycallus ofspongybone
Healedfracture
Newbloodvessels
Spongybonetrabecula
Internalcallus(fibroustissue andcartilage)
1 A hematoma forms. 2 Fibrocartilaginouscallus forms.
3 Bony callus forms. 4 Boneremodelingoccurs.
Figure 6.16 The contrasting architecture of normal versus osteporotic bone.
Figure UN 6.1
Figure 6.17 Fetal primary ossification centers at 12 weeks.
Parietal bone
Radius
Ulna
Humerus
Femur
Occipital bone
ClavicleScapula
Ribs
Vertebra
Ilium
Tibia
Frontal boneof skull
Mandible
Table 6.2 Common Types of Fractures (1 of 3)
Table 6.2 Common Types of Fractures (2 of 3)
Table 6.2 Common Types of Fractures (3 of 3)