1. Bone Physiology

2. Bones are Classified by shape and structure
limbs
Carpals
tarsals
vertebrae
Skull bones
Ribs
Sternum
scapula

4. Epiphysis Epiphyseal Line Diaphysis Periosteum Articulating Cartilage
Anatomy of Long Bone
Epiphysis Epiphyseal Line Diaphysis Periosteum Articulating Cartilage

5. Compact Bone
Canaliculi
Haversian Canal
Lamellae
Osteon

6. Another picture of Compact Bone

7. Compact Bone

8. Spongy Bone Located along the epiphyses of long bones Site of Erythrocyte (RBC) formation
(tra-BEK-ū-lē)
Collagen fibers are not arranged in concentric rings. But the lamellae form rods called trabeculae. No Osteons or Haverian Systems are present.

9. Cells in Bones Osteocyte – mature bone cells; recycle Ca and PO4
Osteoclasts – dissolve bone by secreting enzymes and acids. Release Ca to be returned to blood stream
Osteoblasts – cells that produce new bone cells referred to as osteogenesis
Osteoclasts remove matrix, osteoblasts adds matris.
When an osteoblast’s lacunae is calcified the cell becomes and osteocyte.

10. Endochondrial Ossification
Bone tissue in a fetus begins as hyaline cartilage
Inside is cartilage, cartilage becomes ossified.
In 6 weeks cartilage is replaced to bone except at growth plates.

11. In 6 weeks cartilage is replaced to bone except at growth plates.

13. Longitudinal Growth at the Epiphyseal line

14. Two growth plates Composed of hyaline cartilage
Longitudinal growth is completed when epiphyseal lines become completely ossified.

15. Chrondroblasts closest to epiphyses begin to undergo cell division
Cells enlarge (hypertrophy)
Cells die, bone eventually replaces cartilage (invasion zone)

16. Resting Zone
Mitosis Zone
Hypertrophy
Zone
Ossification Zone

17. Growth along Epiphyseal Line
Resting Zone
Mitosis Zone

18. Maturation/Hypertrophy Zone
Ossification Zone

19. Longitudinal Growth Controlled by 3 hormones Growth Hormone
Baby to prepuberty
Sex Hormones (estrogen/testosterone)
Causes growth spurt at puberty
Shapes your skeleton to your sex
Thyroid Hormones (PTH & Calcitonin)
PTH = parathyroid hormone
Controls whether bone growth occurs
Affects Appositional Growth – bone growth in diameter

20. Bone Homeostasis Bone Remodeling
Osteons are formed by osteoblasts
In healthy adults:
Bone deposit = bone resorption
Osteoblasts = Osteoclasts
Bone Remodeling refers to the regular mineral turnover that occurs in bone.
In adults, 18 % of proteins and minerals turns over yearly. Not uniform. I.e. Head of femur is remodeled more. Why?

21. Bone Remodeling Controlled by Negative Feedback Loop
Bone Deposit
Occurs where bone is injured or added bone strength is required
Deposits Ca+2 into bone
Bone Resorption
Osteoclasts break down bone
Calcium is taken from bone and placed into blood stream
Lysosomes assist in the process
Ca and PO4 are released; eventually releasing the blood stream

22. Blood Calcium is the original stimulus
Bone Remodeling is controlled by 2 hormones by a Negative Feedback Loop
Blood Calcium is the original stimulus
Normal Blood Ca is 9-11 mg CA/100 ml of blood
When blood Ca decreases (< 9 mg) Parathyroid Hormone (PTH) is released into bloodstream.
Bone resorption occurs causing Ca to leave bone and goto the blood stream
Osteoclasts are working

23. High levels of blood Ca (>11mg)
When blood Ca levels are high, Calcitonin is released.
Causes bone deposit to occur
Ca from the blood is stored into bone.
(Osteoblasts and Osteocytes are working.)
99% of all Ca is found in bone.

24. PTH
Calcitonin

25. Osteoclasts cause bone resorption
Controlled by PTH
Osteoblasts cause bone deposit
Controlled by calcitonin

26. Factors that help with Bone Deposit
Vitamin D – aids in the absorption of Calcium into the bone. Part of vitamin D is converted to the hormone calcitriol which allows Ca to pass through the S.I.(What food is Vitamin D fortified?)
i.e. rickets results from Vitamin D deficiency
Vitamin C – helps osteoblasts function
i.e scurvy – caused from a reduction in osteoblast activity
Calcium tablets -
Diet -

27. Appositional Growth over time.

28. 2nd Response to Regulating Bone Remodeling
Wolff’s Law
Bone grows or remodels in response to the forces or stresses placed on it.
Appositional growth – growth in diameter is controlled by the amount of mechanical stress and gravity placed on the bone
Heavy usage leads to heavy bones; nonuse leads to atrophy (bone loss)

29. Controlling Bone Remodeling
Hormones PTH and Calcitonin determines whether and when bone remodeling occurs.
Mechanical Stess determines where remodeling occurs. High stress areas grow appositionally.

30. Body’s Needs for Calcium
Transmit nerve impulses
Muscle contractions
Blood coagulation
Cell division
If blood Ca levels are low for an extended time, bones continually lose Ca.
Once bone density loss begins, women lose 8% of their bone mass every decade, men lose 3% every decade

31. Osteoporesis Osteoporesis Normal Bone Risk Factors
Sex (females more affected than males; especially after menopasue)
Insufficient exercise or too much exercise
Poor diet (low in Ca and protein
Smoking
Race: Black > bone density

32. Change in Bone Density with Age

33. Bone Fracture and Repair
Simple Fractures take 8-12 weeks to heal
Healing time increases age due to poor circulation

34. Phases of Bone Repair Hematoma formation
A mass of clotted blood appears
Blood vessels
hemorrhage, causing
internal bleeding
Blood pools and clots around fx area; which closes off injured blood vessels
Hematoma formation

35. Fibrocartilage Callus Formation
Macrophages invade and clean area
Fibroblasts help form chondroblasts and collagen fibers
Helps to form cartilage splint that will connect ends of broken bones

36. Osteoblasts replace the cartilage with spongy bone
Bony Callus
Osteoblasts replace the cartilage with spongy bone
Bone cells replace cartilage from the outside fx toward the inside
Cells are not organized in the bony callus

37. Bone Remodeling
Continues 4 months to a year Removes excess material; a layer of compact bone is produced