The Skeletal System

1. The Skeletal System

2. The Skeletal System • Parts of the skeletal system 1. Bones (skeleton) 3. Ligaments 2. Joints 4. Cartilages • Divided into two divisions 1. Axial skeleton head, neck, & trunk 2. Appendicular skeleton limbs, pectoral girdle, pelvic girdle.

3. Functions of Bones • Support framework for body • Protection of soft organs by skull, rib cage, vertebrae • Movement by attached muscles • Storage of minerals & fats; most important minerals are Ca+ & Phosphorus • Blood cell formation – hematopoiesis, in marrow

4. Bones of the Human Body • The adult skeleton has 206 bones • Two basic types of bone tissue 1. Compact bone • Homogeneous - dense 2. Spongy bone • Small needle-like pieces of bone • Many open spaces Figure 5.2b

5. Classification of Bones on the Basis of Shape Figure 5.1

6. Classification of Bones • Long bones a. Typically longer than wide b. Have a shaft with heads at both ends and a medullary cavity c. Contain mostly compact bone • Examples: femur, ulna, tibia, fibula, phalanges (fingers & toes), metacarpals (palm)

7. Classification of Bones • Short bones a. Generally cube-shape b. Contain mostly spongy bone, no cavity • Examples: carpals (wrist), tarsals (ankle) • Sesamoid – special type of short bone • a. Develop within tendons • Example: patella (kneecap)

8. Classification of Bones • Flat bones a. Thin and flattened b. Usually curved c. Thin layers of compact bone around a layer of spongy bone • Examples: skull, ribs, sternum

9. Classification of Bones • Irregular bones a. Irregular shape b. Do not fit into other bone classification categories • Example: vertebrae, coxal (hip), scapula c. Two or more different shapes; not specifically long or short.

10. Gross Anatomy of a Long Bone • Diaphysis a. shaft b. Composed of compact bone • Epiphysis a. Ends of the bone b. Composed mostly of spongy bone Figure 5.2a

11. Structures of a Long Bone • Periosteum a. Outside covering of diaphysis b. Fibrous connective tissue membrane • Sharpey’s fibers a. Secure periosteum to underlying bone • Arteries a. Supply bone cells with nutrients Figure 5.2c

12. Structures of a Long Bone • Articular cartilage a. Covers the external surface of the epiphyses b. Made of hyaline cartilage (slippery surface) c. Decreases friction at joint surfaces Figure 5.2a

13. Structures of a Long Bone • Medullary cavity a. Cavity of the shaft b. Contains yellow marrow (stores fat) in adults c. Contains red marrow (for blood cell formation) in infants Figure 5.2a

14. Bone Markings • Surface features of bones • Sites of attachments for muscles, tendons, & ligaments • Passages for nerves & blood vessels • Categories of bone markings • Projections and processes – grow out from the bone surface • Depressions or cavities – indentations

15. Microscopic Anatomy of Bone • Osteon (Haversian System) a. A unit of bone • Central (Haversian) canal a. Opening in the center of an osteon b. Carries blood vessels and nerves • Perforating (Volkman’s) canal a. Canal perpendicular to the central canal b. Carries blood vessels and nerves

16. Microscopic Anatomy of Bone Figure 5.3

17. Microscopic Anatomy of Bone • Lacunae • Cavities containing bone cells (osteocytes) • Arranged in concentric rings • Lamellae • Rings around the central canal • Sites of lacunae Detail of Figure 5.3

18. Microscopic Anatomy of Bone • Canaliculi • Tiny canals through which bone cells indirectly receive nourishment • Radiate from the central canal to lacunae • Form a transport system Detail of Figure 5.3

19. Changes in the Human Skeleton • In embryos, the skeleton is primarily hyaline cartilage • During development, much of this cartilage is replaced by bone • Cartilage remains in isolated areas a. Bridge of the nose b. Parts of ribs c. Joints

20. Developmental Aspects of the Skeletal System • At birth, the skull bones are incomplete • Bones are joined by fibrous membranes called fontanelles (soft spots ) • Fontanelles are completely replaced with bone within two years after birth.

21. Bone Growth • Epiphyseal plates allow for growth (in length) of long bone during childhood a. New cartilage is continuously formed b. Older cartilage becomes ossified • Cartilage is broken down • Bone replaces cartilage • Bones are remodeled and lengthened until growth stops a. Bones change shape somewhat b. Bones grow in width

22. Long Bone Formation and Growth Figure 5.4a

23. Long Bone Formation and Growth Figure 5.4b

24. Types of Bone Cells • Osteocytes a. Mature bone cells • Osteoblasts a. Bone-forming cells • Osteoclasts a. Bone-destroying cells b. Break down bone matrix for remodeling and release of calcium (activity of osteoclasts increase when Ca+ levels in blood drop.) • Bone remodeling is a process by both osteoblasts and osteoclasts.

25. Repair of Bone Fractures 1. Hematoma (blood-filled swelling) is formed (Blood Clot) 2. Break is splinted by fibrocartilage to form a callus 3. Fibrocartilage callus is replaced by a bony callus 4. Bony callus is remodeled to form a permanent patch

26. Stages in the Healing of a Bone Fracture Figure 5.5

27. The Axial and Appendicular Skeleton Axial - Forms the longitudinal part of the body Divided into three parts Skull Vertebral column Bony thorax (ribs, sternum) (4).Hyoid Appendicular 1. Limbs (appendages) 2. Pectoral Girdle clavicle scapula 3. Pelvic Girdle – (hips) ilium ischium pubic

28. The Axial Skeleton Figure 5.6