Skeletal System Overview

1. Skeletal System Overview Chapter 7 p. 192 – p. 204

2. What makes up bone? • Osteocytes (bone forming cells) and extracellular matrix • Osteocytes are found in lacunae (holes in the bony matrix) • Extracellular matrix is made up of collagen and inorganic salts

3. Types of Bones • Long bones • Short bones • Flat bones • Irregular bones • Sesamoid bones

4. Long Bones • Epiphysis • Articular Cartilage • Diaphysis • Spongy bone • Compact bone

5. Parts of the Long Bone • Periosteum • Vascular, fibrous outer covering of bone • Endosteum • Lines medullary cavity • Contains bone forming cells • Medullary Cavity • Hollow region of bone • Continuous with the spongy bone • Marrow, blood vessels found here

6. Spongy Bone • Trabeculae: branching bony plates • Space between the bony plates allows for cushion

7. Compact Bone • Made up of osteons • Circular units with central blood vessels and nerves • Also called Haversian systems • Resists compression • Volkmann’s canals • Also known as perforating canals • Contain larger blood vessels and nerves • Communicate with surface of the bone

9. Osteon

10. Volkmann’s Canals

11. Short Bones • Make up hands and feet

12. Flat Bones • Scapula (shoulder blade) • Skull • Ribs

13. Irregular Bones • Vertebrae • Facial bones

14. Sesamoid Bones • Not always a separate category • Round bones • Patella

15. Bone Marrow

16. Bones under the microscope

17. Osteoporosis

18. Bone Development • Osteogenesis: development of bone • Intramembranous Bone (flat bones) • Unspecialized cells appear at site of new bone formation • Blood vessels move into these cells and allow cells to differentiate into osteoblasts • Deposit bony matrix to form spongy bone • Spongy bone would fill in with higher amounts of bony matrix to form compact bone

19. Bone Development • Endochondral Bones • Develop from masses of hyaline cartilage • Hyaline cartilage lays down basic bone layout • Over time, bone forms over the cartilage template • Osteoblasts form and secrete bony matrix • Once bony matrix surrounds the osteoblasts, they are called osteocytes • Endochondral ossification

20. Bone Development • Primary ossification center • Bone begins to replace hyaline cartilage in the diaphysis • Osteoblasts in periosteum deposit compact bone • Secondary ossification centers • Epiphyses • Spongy bone • Epiphyseal plate – zone of cartilage between diaphysis and epiphysis

21. Bone Development

22. Growth at the Epiphyseal Plate • 4 layers • Resting cartilage • No growth • Closest to the epiphysis • Proliferating cartilage • Young cells, mitosis • Zone of hypertrophic cartilage • Older cells • Zone of calcified cartilage • Dead cells and extracellular matrix

24. Growth at the Epiphyseal Plate • http://www.gla.ac.uk/ibls/US/fab/tutorial/generic/bone5.html

25. Osteoclasts • Invade areas of calcified cartilage • Break down extracellular matrix • Osteoblasts then move in • Deposit bony matrix in place of calcified cartilage

26. Ossification Timetable (p. 200)

27. Factors Effecting Bone Growth and Repair • Nutrition • Exposure to sunlight • Hormones • Physical exercise • Work with a partner to research a factor effecting bone growth and it’s effect on development • Look up a bone growth disorder, too. (Brief!)

28. Fractures • Greenstick – incomplete, across bone (usually in developing bone) • Fissured – incomplete, longitudinal • Comminuted – complete, shatters the bone • Transverse – complete, right angle to bone axis • Oblique – at an angle other than a right angle • Spiral – caused by excessive twisting of the bone • Compound – bone breaks the skin

29. Fractures

30. Bone Repair • Hematoma forms (blood released from vessels within the bone) • Formation of spongy bone and fibrocartilage • Bony callus • Osteocytes, osteoblasts and osteoclasts

31. Functions of the Skeletal System • Support and Protection • Movement • Origin and insertion of muscle • Origin: immovable end of the muscle • Insertion: movable end – during contraction, insertion will move toward the origin

32. Functions of the Skeletal System • Blood production • Hematopoiesis • Bone marrow – long bones, spongy bone, larger canals of compact bone • Red marrow: produces red blood cells, white blood cells and platelets • White marrow: fatty tissue

33. Functions of the Skeletal System • Inorganic salt storage • Salts account for approximately 70% of extracellular matrix of bone • Mostly calcium phosphate – hydroxyapatite • Also: magnesium, sodium, potassium, carbonate ions • Will also absorb small amounts of harmful metallic elements (lead, strontium)