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