Bone TissueBone Tissue

A. Physiology: functions of boneA. Physiology: functions of bone

B. Anatomy: structure of boneB. Anatomy: structure of bone

C. Histology of boneC. Histology of bone

D. Bone homeostasisD. Bone homeostasis

1. Remodeling1. Remodeling

2. Bone's role in calcium 2. Bone's role in calcium homeostasis homeostasis

Physiology: Functions of BonePhysiology: Functions of Bone

1. support1. support

2. protection2. protection

3. movement3. movement

4. mineral homeostasis4. mineral homeostasis

5. blood cell production (hematopoiesis)5. blood cell production (hematopoiesis)

6. energy storage6. energy storage

Shapes of BonesShapes of Bones

1. long1. long

2. short2. short

3. flat3. flat

4. irregular4. irregular

Types of BoneTypes of Bone

1. compact (dense)1. compact (dense)

2. spongy 2. spongy (cancellous)(cancellous)

Long Bone AnatomyLong Bone Anatomy

1. diaphysis1. diaphysis2. epiphysis2. epiphysis3. metaphysis3. metaphysis4. epiphyseal plate4. epiphyseal plate

(Read bone dvp. pg. 220-227)(Read bone dvp. pg. 220-227)5. articular cartilage5. articular cartilage6. articular surfaces6. articular surfaces7. periosteum7. periosteum

a. fibrousa. fibrous b. osteogenicb. osteogenic

8. medullary cavity8. medullary cavity9. endosteum9. endosteum

Bone Cell TypesBone Cell Types1. osteoprogenitor cells1. osteoprogenitor cells

2. osteoblasts -- (osteogenesis)2. osteoblasts -- (osteogenesis)

3. osteocytes– (strain sensors)3. osteocytes– (strain sensors)

4. osteoclasts -- (bone resorption/osteolysis)4. osteoclasts -- (bone resorption/osteolysis)

Bone MatrixBone Matrix

1. ground substance (25%)1. ground substance (25%)

2. collagen (25%)2. collagen (25%)

3. mineral salts (50%)3. mineral salts (50%)

-- tricalcium phosphate (hydroxyapatite)-- tricalcium phosphate (hydroxyapatite)

-- ossification-- ossification

Bone HistologyBone Histology

1. Haversian system1. Haversian system

(osteon)(osteon)

2. Haversian canal2. Haversian canal

3. lacuna3. lacuna

4. lamella4. lamella

5. canaliculus5. canaliculus

Bone and Calcium HomeostasisBone and Calcium Homeostasis

1. remodeling1. remodeling

2. serves to:2. serves to:

a. resist mechanical stressa. resist mechanical stress

b. remove worn boneb. remove worn bone

c. store calciumc. store calcium

(1) parathyroid hormone and vitamin D(1) parathyroid hormone and vitamin D

(2) calcitonin(2) calcitonin

> 10.5 mg/dL

< 9.5mg/dL

Less kidney reabsorption(more calcium excretion)

(osteogenesis)

(osteolysis)

(Intestinal absorption too)

CALCITONIN and BLOOD CALCIUM REGULATION

CONTROLLED CONDITION

RECEPTOR

RETURN TO HOMEOSTASIS

EFFECTORS

CONTROL CENTER

Normocalcemia(blood calcium = 9.5-10.5mg%)

A stress or stimulus causes an increase in blood calcium

Parafollicular cells of thyroid gland recognize hypercalcemia

(blood calcium >10.5 mg%

Parafollicular cells secrete calcitonin

Reduced osteoclast activity

Increased osteoblast activity

Increased bone formation results in increased calcium deposition in bone –

Return to normocalcemia

negative feedback

PTH and BLOOD CALCIUM REGULATION

CONTROLLED CONDITION

RECEPTOR

RETURN TO HOMEOSTASIS

EFFECTORS

CONTROL CENTER

Normocalcemia(blood calcium = 9.5-10.5mg%)

A stress or stimulus causes a decrease in blood calcium

Chief cells of parathythyroid glands recognize hypocalcemia

(blood calcium <9.5 mg%

Chief cells secrete PTH

Increased osteoclast activity

Decreased osteoblast activity

Increased urine phosphate output

Decreased urine calcium output

Increased bone breakdown results in increased calcium release to blood –

Return to normocalcemia

negative feedback

end

Bone Growth, Stress and Bone Growth, Stress and OsteoporosisOsteoporosis