1. Skeletal System

2. Divisions of Skeletal System
Axial skeleton – bones of the skull, vertebral column, and rib cage
Appendicular skeleton – bones of the upper and lower limbs, shoulder, and hip

3. Axial Skeleton 80 bones Consist of bones in the: Skull
Vertebral Column
Thorax
Hyoid

4. Appendicular 126 bones Bones in the: Shoulders Upper limbs Lower limbs
Pelvic girdle

7. Classification of Bones: By Shape
Long bones – longer than they are wide (e.g., humerus)
Figure 6.2a

8. Classification of Bones: By Shape
Short bones
Cube-shaped bones of the wrist and ankle
Bones that form within tendons (e.g., patella)
Figure 6.2b

9. Classification of Bones: By Shape
Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones)
Figure 6.2c

10. Classification of Bones: By Shape
Irregular bones – bones with complicated shapes (e.g., vertebrae and hip bones)
Figure 6.2d

11. Function of Bones Support – form the framework
Protection – provide a protective case for the brain, spinal cord, and vital organs
Movement – provide levers for muscles

12. Function of Bones
Mineral storage – reservoir for minerals, especially calcium and phosphorus
Blood cell formation – (hematopoiesis) occurs within the marrow cavities of bones

13. Gross Anatomy of Bones: Bone Textures
Compact bone – dense outer layer
Spongy bone – honeycomb of trabeculae filled with yellow bone marrow

14. Spongy Bone Does NOT contain osteons
Made up of trabeculae (irregular latticework)
Btw. spaces of trabeculae is filled with red bone marrow
Only site of RED bone marrow:
Vertebrae
Skull
Hips
Ribs
Sternum
Ends of long bones

15. Bone Structure – Typical Long Bone
Diaphysis = shaft, yellow bone marrow produced here
Epiphyses = distal & proximal ends
Epiphyseal line = remnant of epiphyseal plate
Periosteum = outer, fibrous, protective covering, essential for bone growth & diameter
Endosteum = inner lining of medullary cavity, contains bone forming cells
Articular cartilage = pad of hyaline cartilage on the epiphyses where long bones articulate or join, reduces friction, absorbs shock
Medullary cavity=space w/in diaphysis that contains fatty yellow marrow

16. Typical Long Bone Structure

17. Structure of Long Bone
Figure 6.3

18. Structure of Long Bone
Figure 6.3a

19. Structure of Long Bone
Figure 6.3b

20. Structure of Long Bone
Figure 6.3c

21. Bone Tissue
Bone is made up of an inorganic component (mineral salt) making them hard
Also made up of an organic component (collagen fibers) giving it strength

22. Bone Surface Markings Depressions & Openings
Foramen HOLE through which blood vessels, nerves, or ligaments pass through (ex. Foramen magnum)
Meatus PASSAGE extending within a bone (ex. External auditory meatus)
Fossa DITCH or shallow depression on a bone (ex. Mandibular fossa of temporal bone)

23. Processes that form joints
Condyle large rounded prominence forming a joint
Head rounded projection that forms a joint & supported (ex. Head of femur)
Facet smooth, flat surface (ex. Facet of vertebrae)

24. Processes to which tendons, ligaments, & other connective tissues attach
Tuberosity large rounded projection with a rough surface (ex. Deltoid tuberosity of humerous)
Spinous process sharp, slender projection (on vertebrae)
Crest Prominent ridge (ex. illiac crest of pelvic bone)
Trochanter large, blunt projection (only on femur)

25. Microscopic Structure of Bone: Compact Bone
Haversian system, or osteon – the structural unit of compact bone
Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen
Haversian, or central canal – central channel containing blood vessels and nerves
Volkmann’s canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal

26. Microscopic Structure of Bone: Compact Bone
Osteocytes – mature bone cells
Lacunae – small cavities in bone that contain osteocytes
Canaliculi – hairlike canals that connect lacunae to each other and the central canal

27. Microscopic Structure of Bone: Compact Bone
Figure 6.6a, b

28. Microscopic Structure of Bone: Compact Bone
Figure 6.6a

29. Microscopic Structure of Bone: Compact Bone
Figure 6.6b

30. Microscopic Structure of Bone: Compact Bone
Figure 6.6c

31. Chemical Composition of Bone: Organic
Osteoblasts – bone-forming cells
Osteocytes – mature bone cells
Osteoclasts – large cells that resorb or break down bone matrix

32. Functional Zones in Long Bone Growth
Growth zone – cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis
Transformation zone – older cells enlarge, the matrix becomes calcified, cartilage cells die, and the matrix begins to deteriorate
Osteogenic zone – new bone formation occurs

33. Long Bone Growth and Remodeling
Growth in length – cartilage continually grows and is replaced by bone as shown
Remodeling – bone is resorbed and added by appositional growth as shown

34. Long Bone Growth and Remodeling
Figure 6.10

35. Bone Deposition
Occurs where bone is injured or added strength is needed
Requires a diet rich in protein, vitamins C, D, and A, calcium, phosphorus, magnesium, and manganese

36. Importance of Ionic Calcium in the Body
Calcium is necessary for:
Transmission of nerve impulses
Muscle contraction
Blood coagulation
Secretion by glands and nerve cells
Cell division

37. Homeostasis of Bone Tissue
Nutrition
Vitamin D absorbs calcium in small intestine
Vitamin A bone resorption
Vitamin C Hardens bones
Hormones
Growth Hormone (from pituitary gland) stimulates growth
Parathyroid  Can increase or decrease calcium levels
Thyroid Promotes normal bone growth

38. Developmental Aspects of Bones
By age 25, nearly all bones are completely ossified
In old age, bone resorption predominates
Until age of 25 osteoblasts dominate
Mid-old age osteoclasts dominate

39. Hyoid Bone
Not actually part of the skull, but lies just inferior to the mandible in the anterior neck
Only bone of the body that does not articulate directly with another bone
Attachment point for neck muscles that raise and lower the larynx during swallowing and speech

40. Vertebral Column
Formed from 26 irregular bones (vertebrae) connected in such a way that a flexible curved structure results
Cervical vertebrae – 7 bones of the neck
C1=Atlas
C2=Axis
Thoracic vertebrae – 12 bones of the torso
Lumbar vertebrae – 5 bones of the lower back
Sacrum – bone inferior to the lumbar vertebrae that articulates with the hip bones

41. Vertebral Column
Figure 7.13

42. Bony Thorax (Thoracic Cage)
Functions
Forms a protective cage around the heart, lungs, and great blood vessels
Supports the shoulder girdles and upper limbs
Provides attachment for many neck, back, chest, and shoulder muscles
Uses intercostal muscles to lift and depress the thorax during breathing

43. Bony Thorax (Thoracic Cage)
Figure 7.19a

44. Comparison of Male and Female Pelves
Table 7.4.1

45. Comparison of Male and Female Pelves
Table 7.4.2

46. Developmental Aspects: Fetal Skull
Infant skull has more bones than the adult skull
At birth, fetal skull bones are incomplete and connected by fontanels
Fontanels
Unossified remnants of fibrous membranes between fetal skull bones
The four fontanels are anterior, posterior, mastoid, and sphenoid

47. Developmental Aspects: Fetal Skull
Skull bones such as the mandible and maxilla are unfused
Figure 7.33

48. Developmental Aspects: Old Age
Intervertebral discs become thin, less hydrated, and less elastic
Risk of disc herniation increases
Loss of stature by several centimeters is common after age 55
Costal cartilages ossify causing the thorax to become rigid
All bones lose mass

49. Questions?