Skeletal and Muscle Systems Part 1 Flashcards
Purpose of the Skeletal System
- Forms the body
- Supports tissues
- Permits movement by providing points of attachment for muscles
- Site of blood cell formation
- Mineral storage (especially Calcium)
- Rigid connective tissue
- Constituents
- Cells
- Fibers
- Ground substance
Bone is an Organ
- bone tissue (connective tissue classification)
- cartilage tissue (connective)
- fibrous connective tissue
- blood (connective)
- nerve tissue
Bone Structure
A. Parts of a long bone
1. Epiphyses at both ends
covered with articular cartilage; articulates w/ bone
2. Diaphysis - shaft
3. Periosteum covering
4. Compact bone - strength and resists bending
5. Spongy bone - strength with weight reduction
6. Medullary cavity - red or yellow marrow
Bone Structure
B. Microscopic structure
- CORTICAL or Compact bone has osteons cemented together
- Osteonic canals with blood vessels
- Intracellular matrix of collagen & inorganic salts (Ca, Mg, K, Carbonate, Na)
- Spongy cells nourished by diffusion from thin bony plate surfaces
- Osteocytes
- Osteoblasts
- Osteoclasts
Osteoblasts- Modeling bone cells
– Derived from mesenchymal cells – Produce type I collagen – Respond to parathyroid hormone – Produce osteocalcin – assist in calcification – Synthesize osteoid • Nonmineralized bone matrix
Osteocytes
– A transformed osteoblast that is surrounded in osteoid as it hardens from deposited minerals
– i.e. - mature bone cells (calcified matrix surrounding osteoblasts)
Osteoclast
• cells to break down the calcified matrix
• The major reabsorptive cell of the bone
• produce acids to solubilize salts
• Large, multinucleated cells
• digest organic matrix
– Contain lysosomes filled with hydrolytic enzymes
Bone Matrix
- 35% organic and 65% inorganic
- Collagen fibers
- Calcium and phosphate minerals
- Proteoglycans
- Glycoproteins
Nerve Supply Bone
- sparse
- periosteum
- afferent sensory
- sympathetic efferent
- dilation of bone
- blood vessels
Bone Blood Supply
- small bones single artery and vein
- chief is Principle Nutrient artery
- internal branches
Bone Tissue:
Compact (Cortical) bone
– 85% of the skeleton
– Haversian system
• Haversian canal, lamellae, lucunae, osteocyte, and canaliculi
Bone Tissue:
Spongy (cancellous) bone
– Lack haversian systems
– Trabeculae
Bone Tissue:
Periosteum
- See textbook
Homeostasis of Bone
Constant modeling and remodeling
3 - 5% bone calcium exchanged each year
Bone Remodeling
• Bone-remodeling units • Repairs microscopic injuries and maintains bone integrity • Phases – Activation of the remodeling cycle – Reabsorption – Formation of new bone
Factors Affecting Bone Growth (Formation)
- Calcium, Phosphorus
- Parathyroid Hormone
- Vitamin D
- Calcitonin
- Sex Hormones
- Growth Hormone
- Weight bearing
- Glucocorticoids
- Vitamins A and C
Calcium, Phosphorus
- plasma and interstitial fluid
-osteoblasts - calcium salts precipitate on collagen fibers
-hydroxyapatite crystals
- crystalline structure of
bone mineralization - GI absorb
-Vit D and PTH
-PTH and calcitonin - phosphorous absorb with Ca
Parathyroid Hormone
GI absorb Ca
promotes formation osteoclasts
retards formation of osteoblasts
increase tubular reabsorb of Ca and decrease same of PO4
Vitamin D (Vit D2 and Vit D3)
diet and skin + UV
Vit D2 and D3 same metabolism and bio. act.
D2/D31,25[OH]2D3 = active form
control GI Ca absorb
Calcitonin
-hypercalcemia stimulus
-thyroid gland
-reduce bone reabsorption
- decreases osteoclast and increases osteoblast
Sex Hormones
- estrogen stim osteoblast
- testosterone increase bone thickness and epiphyseal closure
- low test –> osteoporosis
Growth Hormone
N/A
Weight Bearing
- Stimulates osteoblast activity
- electrical potential ?
Glucocorticoids
- Protein breakdown - bone collagen
Vitamins A and C
N/A
Factors that Retard Bone Formation
Estrogen/androgen deficiency Vitamin deficiency Starvation Diabetes Steroids Inactivity/Immobility Heparin Excess parathyroid hormone
Bone Mass across the Life Span
- Peaks in third decade
- Stable until approx 50 yrs women
- Stable until approx 60 yrs men
- Slowly declines (1% per year)
- Women accelerated after menopause for a few years (2-3% year)
- Men decline more slowly
Why bone mass decrease with age?
• Net bone loss:
Because rate of resorption of old bone is faster than deposition of new bone.
Why the Sex Differences ?
- Men initial bone mass is more, so takes longer for the decline to lead to disease
- Men begin decline later than women
- Men do not have menopause
What is a Joint?
Articulations
- functional junctions between bones
- classified by type of tissue
- —fibrous
- —cartilaginous
- —-synovial
- classified by degree of movement
- —-synarthroses: immovable
amphiarthroses: slightly movable
diarthroses: freely movable
What is a Joint?
A. Fibrous joints B. Cartilaginous joints C. Synovial joints 1. ball-and-socket 2. condyloid 3. gliding joints 4. hinge joint 5. pivot joint 6. saddle joint
Fibrous Joints
- bones in close contact
- thin layer of fibrous connective tissue
- no movement: e.g. skull
- limited move: e.g. leg - between tibia and fibula
Cartilaginous Joints
-connect two bones with discs of fibrocartilage or hyaline cartilage
-disc:
—band of fibrous tissue surrounding gelatinous core
—absorb shock and equalize pressure
- limited movement: Vertebrae
Synovial
-synovial membrane - lubrication
-free movement: e.g. knee
-complicated structure
bursae - fluid sacs shock absorb
menisci - fibrocartilage
Ligaments and Tendons
See next cards
Ligaments
viscera to viscera
bone to bone
stability
connective tissue
Tendons
extension of muscle/connective tissue
attach muscle to bone or other tissue
receive innervation
poor blood supply
