1. Calcium Homeostasis & Bone Tissue
Skeleton is a reservoir of Calcium & Phosphate
Calcium ions involved with many body systems
nerve & muscle cell function
blood clotting
enzyme function in many biochemical reactions

2. Small changes in blood levels of Ca+2 can be deadly
cardiac arrest if too high
respiratory arrest if too low

3. Development of Bone Tissue
Both types of bone formation begin with mesenchymal cells
Mesenchymal cells transform into chondroblasts which form cartilage OR
Mesenchymal cells become osteoblasts which form bone
Development of Bone Tissue
Mesenchymal Cells

4. Developmental Anatomy
5th Week =limb bud appears as mesoderm covered with ectoderm
6th Week = constriction produces hand or foot plate
and skeleton now totally cartilaginous
Developmental Anatomy

5. Principles of Human Anatomy and Physiology, 11e
7th Week = endochondral ossification begins
8th Week = upper & lower limbs appropriately named
Principles of Human Anatomy and Physiology, 11e

6. EXERCISE AND BONE TISSUE
Within limits, bone has the ability to alter its strength in response to mechanical stress by increasing deposition of mineral salts and production of collagen fibers.

7. Removal of mechanical stress leads to weakening of bone through demineralization (loss of bone minerals) and collagen reduction.
reduced activity while in a cast
astronauts in weightless environment
bedridden individuals
Weight-bearing activities, such as walking or moderate weightlifting, help build and retain bone mass.

8. AGING AND BONE TISSUE
Of two principal effects of aging on bone, the first is the loss of calcium and other minerals from bone matrix (demineralization), which may result in osteoporosis.
very rapid in women as estrogens levels decrease
in males, begins after age 60

9. The second principal effect of aging on the skeletal system is a decreased rate of protein synthesis
decrease in collagen production which gives bone its tensile strength
decrease in growth hormone
bone becomes brittle & susceptible to fracture

10. Osteoporosis Decreased bone mass resulting in porous bones
Those at risk
white, thin, menopausal, smoking, drinking female with family history

11. athletes who are not menstruating due to decreased body fat & decreased estrogen levels
people allergic to milk or with eating disorders whose intake of calcium is too low
Prevention or decrease in severity
adequate diet, weight-bearing exercise, & estrogen replacement therapy (for menopausal women)
behavior when young may be most important factor

12. Disorders of Bone Ossification
Rickets
calcium salts are not deposited properly
bones of growing children are soft
bowed legs; also skull, rib cage, and pelvic deformities result
Osteomalacia
new adult bone produced during remodeling fails to ossify
hip fractures are common

13. Bone Scan Radioactive tracer is given intravenously
Amount of uptake is related to amount of blood flow to the bone
“Hot spots” are areas of increased metabolic activity that may indicate cancer, abnormal healing or growth
“Cold spots” indicate decreased metabolism of decalcified bone, fracture or bone infection

14. DIVISIONS OF THE SKELETAL SYSTEM
The axial skeleton consists of bones arranged along the longitudinal axis of the body. The parts of the axial skeleton, composed of 80 bones, are the skull, hyoid bone, vertebral column, sternum, and ribs (Figure 7.1).

15. The appendicular skeleton comprises one of the two major divisions of the skeletal extremities (limbs or appendages) and the pectoral (shoulder) and pelvic (hip) girdles system.It consists of 126 bones in the upper and lower , which attach them to the rest of the skeleton.

16. Chapter 7 & 8 Axial & Appendicular Skeleton
Axial Skeleton
80 bones
lie along longitudinal axis
skull, hyoid, vertebrae, ribs, sternum, ear ossicles
Appendicular Skeleton
126 bones
upper & lower limbs and pelvic & pectoral girdles

17. Chapter 8 The Skeletal System: Appendicular Skeleton
Pectoral girdle
Pelvic girdle
Upper limbs
Lower limbs

18. Bone Shapes
Long – length >width Short – nearly equal in length & width Flat – bone shape is primarily flat Irregular – does not fit in any of the above categories Sutural bones - in joints between skull bones