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Connective Tissue: Cartilage and Bones

Cartilage
1. Functions
  1. support and protecction of soft tissues
  2. provide a gliding surface at articulations or joints
  3. provide a model for the formation of most bones
    1. bony precursor or a "rough draft" that later ossifies into bone
2. Characteristics
  1. perichondrium
    1. dense irregular connective tissue surrounding artilage
    2. aids in protection adn regeneration
  2. primary cells
    1. CHONDROBLASTS
      1. secrete matrix below perichondrium, become chondrocytes
    2. CHONDROCYTES
      1. mature cells, maintain cartilage
  3. Fibers
    1. Collagen and Elastic
  4. Ground Substance
    1. gel like made of mostly water
    2. contiants sugars that draw in water
3. WHY DOESN"T CARTILAGE REGNERATE OR HEAL WELL?
  1. They are avascular and lack innervation
  2. nutrients recieved via diffusion
  3. movement (compression & tension) help nutrients diffuse through ground substance
4. Hyaline Cartilage
  1. Most Common
  2. Fibers: collagen
  3. locations
    1. articular cartilage of joints (does not have perichondrium)
    2. respiratory tract
    3. nose
    4. costal cartilage
  4. Bone precursor during embryonic development
5. Elastic
  1. Least abundant in body
  2. highly flexible
  3. fibers: elastic & collagen
  4. locations
    1. ear
    2. epiglottis
6. FIbrocartilage
  1. Fibers: collagen
  2. less ground substance
  3. lots of dense collagen fibers resist tension
  4. location
    1. intervertebral discs
    2. pubic symphysis
    3. menisci (in knees)
  5. Distribute loads and create congruent joints
Bones
1. Functions
  1. Support and protection of soft tissue
  2. Movement
    1. Muscles does not push. It only shortens. When a muscle is anchored on two bones and shortens, it will cause movement
  3. Energy Metabolism
    1. some bone cells help to regulate blood sugar and fat storage through hormone secretion
  4. Mineral storage
    1. 90% of body's calcium and phosphate reserves
  5. blood cell formation (hematopoiesis) and energy storage
    1. occurs in bone marrow
2. characteristics
  1. Extracellular Matrix (aka. osteoid)
    1. Solid
    2. fibers: Collagen
      1. provides flexibility, resists tension
    3. mineral component (hydroxyapatite)
      1. provides rigidity against compression
    4. Bones are flexible and dynamic organs - not just rigid rods
      1. growth and development
      2. heal and regenerate
    5. vascular and innervated, unlike cartilage
3. cells
  1. osteoblasts
    1. near periosteum and endosteum
    2. Function
      1. produce osteoid (bone matrix)
  2. Osteocytes
    1. function
      1. maintain bone
    2. osteoblasts creates osteocytes
    3. housed in lacunae
  3. Osteoclasts
    1. Function
      1. destroy bone
    2. derived from fused bone marrow cells
    3. help with remodeling of bone during growth and repair
4. Types
  1. compact
    1. dense or cortical
    2. hard, outer surface of bone
    3. solid with canals for neurovasculature
  2. spongy bone
    1. trabecular or cancellous
    2. located within bone
5. microstructure of bone
  1. Spongy
    1. does not have osteons
    2. lamellae with osteocytes in lacunae
    3. trabeculae organize along lines of stress
6. class of bone
  1. Long bones
    1. longer than wide
      1. bones of extremities, hands, and feet
    2. medullary cavity
      1. space within the shaft
    3. epiphyseal line
      1. remnant of growth plate
  2. short bones
    1. approximately cube shaped
      1. carpals and tarsals
  3. flat bones
    1. flat and thin
      1. neurocranial bones, scapula, sternum
  4. irregular bones
    1. unlike all others
      1. vertebrae, os coxa, facial bones
  5. special types of bone
    1. sesamoid bones
      1. found within muscle tendons ( patella)
  6. short, irregular, and flat bones
    1. a layer of spongy bone sandwiched by outer layers of compact bone
      1. also called diploe
    2. no medullary cavity
7. bone growth
  1. interstitial
    1. growth in length
    2. during childhood and adolescence
    3. occurs at growth plate made of cartilage
    4. stops when epiphysis and diaphysis meet and growth plate ossifies
  2. Appositional
    1. growth in diameter (thickness)
    2. osteoblasts secrete matrix forming outer ring at periosteum
    3. new bone is destroyed by osteoclasts then replaced by osteons
    4. osteoclasts also remove bone in medullary cavity
8. Remodeling
  1. bone is replaced during life to
    1. maintain fluid concentrations of calcium and phosphate
    2. respond to mechanical stress
  2. is coordinated to maintain total bone mass
    1. bone resorption
      1. osteoclasts break down bone tissue
    2. bone deposition
      1. osteoblasts lays down new bone
  3. renewal rate
    1. compact bone replaced every 10 years
    2. spongy bone replaced every 3-4 years
9. clinical correlate: osteoporosis
  1. deterioration of microscopic architecture bone, low bone mass
  2. resorption greater than deposition (more osteoclasts)
  3. leads to bone fractures
    1. most common - vertebrae and neck of femur (broken hip)
    2. occurs mostly in older individuals
      1. common in postmenopausal individuals (estrogen deficiency)

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Connective Tissue: Cartilage and Bones

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	Created by Andrea Vang about 2 years ago