Connective Tissue 2 Flashcards
CARTILAGE
- Strong, resilient and
semi-rigid connective
tissue - Allows both strength AND
flexibility - Role in maintaining
shape, reduce friction at
joints, shock absorber,
fusion and support - Avascular – produce anti-angiogenesis factor
- Heals poorly
- Perichondrium (dense irregular connective
tissue) covers some cartilage surface
CARTILAGE CELLS - CHONDROCYTES
- Chondrocytes within
lacunae in the
extracellular matrix - Matrix consists of
collagen/elastic fibres
embedded in
chondroitin
sulphate
TYPES OF GROWTH
2 Mechanisms of growth
Appositional Growth
Chondroblasts in perichondrium differentiate into chondrocytes, start and producing matrix and add to existing cartilage
Interstitial Growth
Proliferation and hypertrophy of existing chondrocytes
Types Of Cartilage
- Hyaline Cartilage
- Fibrocartilage
- Elastic Cartilage
HYALINE CARTILAGE
-Most abundant.
- Examples: Between tips of ribs; covering synovial joints; supporting larynx and trachea.
- Reduces friction at joints
- Tough but quite flexible.
- Surrounded by perichondrium
FIBROCARTILAGE
- Extremely durable
- Lacks ground substance
- Tightly packed collagen fibres
- Examples: between spinal vertebra; some joints/tendons
- Resists compression; absorbs shock; prevents bone
damage
ELASTIC CARTILAGE
- Numerous elastic fibres
- Resilient and flexible
- Provides support, allows distortion
- Examples: external ear flap; parts of larynx
- Epiglottis – made almost entirely of elastic
cartilage
OSTEOARTHRITIS
- Degeneration of
articular/hyline cartilage - Bone ends rub together
at joints - Pain, stiffness and
swelling - Age, weight, previous
injury
What are the
functions of
bone?
-Production of
blood cells
(Haematopoiesis)
-Protection
-Leverage
-Support
-Storage of minerals
-Storage of lipids
BONE – OSSEOUS TISSUE
Supportive connective tissue
Low volume of ground substance
2/3 matrix calcium salts (phosphate and
carbonate)
The rest is collagen
Minerals arranged around collagen fibres
Highly shatter resistant
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LONG BONE STRUCTURE
-Epiphysis – Spongy bone with
compact cover
-Diaphysis – wall is a layer of
compact bone covering central
marrow cavity
BONE ANATOMY
-Yellow Marrow- Apidocytes
-Red Marrow- RBCs, WBCs
and stem cells
* Lacunae contain osteocytes
* Lacunae arranges around branching blood vessels
* Canaliculi – long slender passageways! Allow exchange of materials
with blood
* Generally covered in periosteum (similar to perichondrium)
BONE- COMPACT
- Osteon - basic unit
- Lamellae - the different
layers
BONE- SPONGY
- NO osteons!
- Matrix forms Trabeculae
- Diffusion of nutrients
along canaliculi - Red marrow present
BONE CELL 1: OSTEOCYTE
Osteocyte
- In Lacuna
- Layers of Lamella
- Can’t divide
- Maintain/monitor protein/mineral
- Repair
BONE CELL 2: OSTEOBLAST
- Osteoblast
- Osteogenesis – produce bone matrix and deposit Calcium
- Osteocytes develop from osteoblasts
BONE CELL 3: OSTEOPROGENITOR CELL
- Osteoprogenitor cells
- Stem cells
- Differentiate into osteoblast
- Repair of fractures
BONE CELL 4: OSTEOCLAST
- Osteoclast
- Remove bone matrix
- Giant cells with 50+ nuclei
- Monocyte derived!
- Osteolysis
BONE COMPOSITION
2/3 Calcium phosphate
+ Calcium hydroxide
Together make crystals of Hydroxyapatite
1/3 collagen
Cells only account for 2% weight
Strong, yet flexible
Ossification – Bone formation
Calcification – deposition of calcium
OSSIFICATION BONE FORMATION
2 methods of bone formation
1) Intramembranous ossification
- Bone forms directly within mesenchymal connective tissue in
deep dermis.
- Includes formation of flat bones the skull, numerous facial
bones.
2) Endochondrial ossification
- During development
- Bone forms from hyaline cartilage
- Includes formation of long bones
In Embryo
Endochondral ossification
-Replacing cartilage
with bone
intramembranous ossification
-Producing roofing
bones of skull
BONE FORMATION
OSSIFICATION - the process by which bone
forms
Occurs in 4 different situations:
1) Initial bone formation in embryo & foetus
2) Bone growth during childhood/adolescence
3) Remodelling of bone (replacing old bone with
new, throughout life)
4) The repair of fractures
BONE REMODELLING
Older minerals released into circulation
Simultaneous absorption of minerals into bone
Interplay of osteocytes, osteoblasts and osteoclasts
Osteoblasts → formation of osteon
Osteoclasts → Remove osteon
1/5th skeleton recycled annually in adults
Regional differences
EXERCISE
Bone stress – Mineral crystals minute electrical fields
* Osteoblasts are attracted to these
* Lack of exercise – brittle bones
* Even a few weeks of inactivity – lose a 3rd
* Heavily stressed boned – thicker/stronger
OSTEOPOROSIS
- Resorption outpaces
deposition - Calcium depletion (urine,
faeces, sweat) - Spontaneous fracture,
height loss, bone pain - 80% cases are female
- Lack of oestrogen after
menopause (blast activity) - Genetic factor
DEXA
- Dual energy X-ray
absorptiometry - Measures bone
mineral density - Quick & painless
- Less radiation than
regular x-ray - Used in diagnosis of
osteoporosis
