Connective Tissue - Bone & Cartilage Flashcards
What are the main functions of cartilage?
- provide resilient and pliable support
2. direct formation and growth of bone
What do chondrocytes do?
make cartilage matrix and tissue
- primitive mesenchymal cells -> chondrocytes
- perichondrium -> chondrocytes
- secrete ECM components
What are lacuna?
isolated compartments wehre cartilage resides
- interstitial growth is possible here
- continue to secrete cartilage matrix
What are the 3 type of cartilage?
- Hyaline Cartilage
- Elastic Cartilage
- fibrocartilage
Describe hyaline cartilage
Thin fibrils
Ground substance = hyaluronic acid -> hydration & flexibility
- allows metabolites to diffuse through tissue
- resilient to compression
- allows growth of chondrocytes within matrix
- can calcify and initiate bone formation
What distinguishes elastic cartilage from hyaline and fibrocartilage?
- abundant elastic fibers and interconnecting sheets (lamellae) - external ear - epiglottis_ larnyx Should not calcify
Describe fibrocartilage
large bundles of regularly arranged collagen
- continuation of dense connective tissue (very similar to one another )
- resists compression and shear forces
- found where tendons attach to bones
- intervertebral discs
What are the two types of bone?
- flat bone (skull, mandible)
2. long bone (femur, tibia, humerus)
What are the parts of a long bone?
diaphysis - long shaft
epiphysis - expanded ends
What are the two regions of bone?
compact bone spongy bone (aka cancellous/ trabecular)
What are trabeculae?
- thin anastomosing spicules in spongy bone
- important in signaling
What is the function of compact bone?
provide support
What is the function of spongy bone?
trabeculae provide surface area for metabolism
Where is bone marrow and what does it consist of?
Bone marrow is the inner spongy tissue between trabeculae
consists of:
- hematopoietic tissue (red bone marrow)
- adipose cells (white bone marrow)
What is the outer covering of bone called? and what does it contain?
periosteum
- dense connective tissue
- fibroblasts
- bone precursors
- bone cells
What is the endosteum?
Inner contact between trabeculae and inner soft tissue
- location of most calcium mobilization
What are the different types of bone cells?
osetoprogenitor
osteoblasts
Osteocytes
osteoclasts
What are osteoprogenitor cells?
stem cells, periosteum and endosteum
What are osteoblasts?
- secrete osteoid
- release matrix vesicles -> initiate bone calcification
- capable of division
What are osteocytes?
from osteoblasts
- do not divide
- form in lacuna
- interconnected living lattice of cells
- signal one another through gap junctions
What are osteoclasts?
NOT FROM OSTEOPROGENITOR
- from monocytes of blood
- related to macrophage -> phagocytose
- degrade bone or cartilage
- allow inward growth of blood vessels
- resorb/ remodel bone
- mobilize Ca2+
What substance is specific to the gone matrix? What is it made of?
hydroxyapatite
- Ca2+
- PO4
What are haversian canals?
channels traversing long axis of long bones - surrounded by lamellae
canal + lamellae = osteon
What are Volkmann’s canals?
link haversian canals
How do flat bones form?
intramembranous ossification
How do long bones form?
Encochondral ossification
What is appositional growth?
Growth in pericondrium at cartilage surface -> fibroblasts proliferate into more chondrocytes -> secrete hyaline matrix
What is interstitial growth?
Chondrocytes within matrix continue to proliferate within their lacunae
- groups of chondrocytes within lacunae
=> isogenous groups
What are some disorders of bone remodeling?
osteoperosis -> decrease in bone mass
(defect in resoption/formation coupling)
Osteopetrosis -> defective resorption & increased bone mass
Osteomalacia rickets -> abnormal increase in uncalcified osteoid -> interferes with mineralization
How do osteoblasts initiate mineralization of osteiod?
secrete matrix vesicles
- have high levels of Ca2+ and PO4
- activate and form precipitates -> grow and rupture vesicle-> nucleation sites that trigger mineralization cascade
What pathways control bone remodeling/ regulation?
Short range signals (BMPs)
Long range signals
Mechanical stress
Neuronal stimulation
What are bone morphogenetic proteins (BMPs)?
secreted by cells
- bind surface receptors -> trigger intracellular phosphorylation -> alter gene expression=> promote specific differentiation patterns
What is the effect of parathyroid hormone on Ca2+ levels in the blood?
increases blood calcium
What is the effect of Calcitonin on Ca2+ levels in the blood
Decreases blood calcium
stiumlates resorption
