Skeletal System

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. 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 Homeostasis of Bone Tissue

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?