1. Bone Formation
Begins as cartilage or fibrous membranes in embryos – ossification replaces it with bone.

2. Fetal Skeleton at 12 Weeks

3. Bone Growth and Remodeling
Bones increase in length
epiphyseal plate
epiphyseal line is left behind when cartilage gone
Bones increase in width = appositional growth
osteoblasts lay down matrix in layers on outer surface and osteoclasts dissolve bone on inner surface
Bones remodeled throughout life
architecture of bone determined by mechanical stresses
action of osteoblasts and osteoclasts
greater density and mass of bone in athletes or manual worker is an adaptation to stress

4. Control of Growth & Remodeling
Growth hormone from pituitary gland and sex hormones control long bone growth
PTH (parathyroid hormone) activates osteoclasts to break down bone and release Ca+2 ions to blood if levels too low.
When Ca+2 level is too high, deposits in bone matrix where mechanical stress is high.

5. Dwarfism Achondroplastic Pituitary
long bones stop growing in childhood
normal torso, short limbs
spontaneous mutation during DNA replication
failure of cartilage growth
Pituitary
lack of growth hormone
normal proportions with short stature

6. Ion Imbalances hypocalcemia hypercalcemia
Changes in calcium can be serious
hypocalcemia
causes excitability of nervous system if too low
muscle spasms, tremors or tetany
laryngospasm and suffocation
hypercalcemia
depresses nervous system
muscle weakness and sluggish reflexes, cardiac arrest

7. Hormonal Control of Calcium Balance
Calcitriol, PTH and calcitonin maintain normal blood calcium concentration.

8. Calcitriol (Activated Vitamin D)

9. Calcitonin
Secreted by thyroid gland when calcium concentration rises too high
Functions
reduces osteoclast activity as much as 70%
increases the number and activity of osteoblasts
Can be used to treat what condition???

10. Correction for Hypercalcemia

11. Correction for Hypocalcemia
Increased absorption from intestines
Calcitriol

12. Other Factors Affecting Bone
Hormones, vitamins, and
growth factors
Growth rapid at puberty
hormones stimulate osteogenic cells, chondrocytes and matrix deposition in growth plate
girls grow faster than boys and reach full height earlier (estrogen stronger effect)
males grow for a longer time and taller
Growth stops (epiphyseal plate “closes”)
teenage use of anabolic steroids = premature closure of growth plate and short adult stature

13. Fractures and Their Repairs

14. Fractures and Their Repair
Stress fracture caused by trauma
car accident, fall, athletics, etc
Pathological fracture in bone weakened by disease
bone cancer or osteoporosis
Open (simple) vs closed (compound) fractures
Reduction is realignment of broken bone ends
Immobilization to allow healing.

15. Fibrocartilage Callus
Healing of Fractures
Hematoma
Bony Callus
Fibrocartilage Callus
Remodeling
3-4 months
6 weeks

16. Joints (Articulations)
Classified two ways:
Function – degree of movement
Structure – fibrous tissue, cartilage, or joint cavities separate the bones

17. Functional
Synarthroses
Amphiarthroses
Diarthroses
Structural
Fibrous
Cartilaginous
Synovial

18. Synarthroses/ Fibrous joints

19. Amphiarthroses/ Cartilaginous Joints

20. Diarthrotic/Synovial Joints
Condyloid

21. Synovial Joint Structure

22. Quiz
1. _______________ is secreted by the parathyroid gland when calcium blood levels are low. It increases osteoclast population, promotes calcium resorption by the kidneys, & promotes calcitriol synthesis in the kidneys. It also inhibits collagen synthesis and bone deposition by osteoblasts.
____________ is secreted by thyroid gland when calcium concentration rises too high.
It reduces osteoclast activity as much as 70% and increases the number and activity of osteoblasts.
3. ________ is made by the skin, liver, and kidneys, and behaves as a hormone that raises blood calcium concentration by:
-increases intestinal absorption and absorption of calcium from the skeleton
-increasing osteoclasts
-promoting urinary reabsorption of calcium ions