What are the three types of cartilage?
- hyaline cartilage
- elastic cartilage
- fibrocartilage
What body system is cartilage found in?
-skeletal system
In some vertebrates the entire skeletal system is cartilage.
Most bone is preceded by cartilage.
What are the functions/characteristics of cartilage?
- compressible
- resists distortion
- absorbs shock
- reduces friction
- template for endochondral bone growth
- involved in bone fracture repair
What is the name of the space where chondrocytes/blasts are found?
-lacunae
How does cartilage receive nutrients? How does this affect the tissue?
- diffusion of nutrients through matrix from surrounding blood vessels (cartilage is avascular)
- cartilage is slow to heal
What differentiates territorial matrix and inter-territorial matrix?
Territorial matrix:
- more newly formed
- closer in proximity to chondrocytes
- high GAG, low collagen
Inter-territorial matrix:
- older
- further from chondrocytes
- low GAG, high collagen
What are the different layers of perichondrium and what are their functions?
Outer fibrous later:
- contains fibroblasts
- point of connection to other structures
Inner chondrogenic layer:
- contains chondroblasts which become chondrocytes
- produces matrix components
What are characteristics of hyaline cartilage?
- most common cartilage
- avascular, receives nutrients by diffusion
- type II collagen
- translucent, blue grey/white
- solid but flexible
- chondrocytes found in groups
- perichondrium.
- grows both appositionally and interstitialy
What are the characteristics of elastic cartilage?
- contains type II collagen and elastic fibers
- yellow color (without staining)
- more opaque, flexible and elastic
- chondrocytes mostly located singly
- surrounded by perichondrium.
What are the characteristics of fibrocartilage?
- type I cartilage
- increased collagen concentration
- opaque
- reduced cellularity
- single, sparse chondrocytes
- no perichondrium
Where is hyaline cartilage found?
- external auditory meatus
- larynx
- trachea
- bronchi
- fetal long bones
- epiphyseal plate
- articular surfaces
Where is elastic cartilage found?
- auricle (pinna) of ear
- epiglottis
Where is fibrocartilage found?
- intervertebral discs
- pubic symphysis
- insertion of some tendons and ligaments
- associated with dense connective tissues and hyaline cartilage
What is the organization of bone tissue and why is it organized this way?
-organized in a canalicular system allowing penetration of blood vessels for high vascularity
How is bone length increased?
- appositional growth of a hyaline cartilage model
- bone can not grow intersttially
Bone is a(n) __________ tissue meaning that it is constantly __________, __________, and __________.
Active/living; resorption; reconstructed; remodeled
What are the different components of bone matrix and what is their function?
Organic component:
- osteoid
- provides flexibility
Inorganic component:
- hydroxyapatite
- 35-65% of matrix
- provides rigidity
What are the types of bone tissue and what are their characteristics?
Woven:
- occurs during bone development and repair
- rapidly produced
- haphazard collagen
- less structural integrity
Spongy:
- also called trabecular or cancellous bone
- 3D lattice of bone spicules
- spaces for bone marrow
Compact bone:
- also lamellar bone
- Haversian structure
- lacks larger cavities
Describe the features of the Haversian structure of compact bone.
- Haversian system, also called OSTEON, consists of multiple concentric layers called LAMALAE
- border of osteon is called CEMENT LINE
- at center is a HAVERSIAN CANAL which contains a blood vessels and nerves
- blood vessels and nerves penetrate osteons to reach Haversian canals via VOLKMAN’S CANALS
- cells are located in LACUNAE between lamellae
- lacunae are connected to each other and Haversian canal by CANALICULI
What are osteoprogenitor cells?
- stem cells which differentiate into osteoblasts and bone lining cells
- found on the inner periosteum, the nostrum, and lining vascular canals
Describe osteoblast characteristics and major products.
Characterized by:
- alkaline phosphates (not in osteocytes)
- vitamin D3 (regulates osteocalcin)
Major products:
- type I collagen
- osteocalcin (binds hydroxyapatite)
- osteonectin
- osteopontin
- osteoprotegerin
- RANKL
What cell type is the progenitor for osteoclasts?
-monocytes and monocytes progenitors located in the bone marrow
What does high and low parathyroid hormone have on bone regulation.
Low PTH:
- bone formation
- osteoblast activation
High PTH:
- bone reabsorbtion
- release of osteoclast differentiation factors
- differentiation of monocytes into osteoclasts
- osteoclast activation
Describe the process of osteoclast regulation by osetoblasts.
Formation:
- PTH binds osteoblast
- osteoblast stimulated to release M-CSF (monocytes colony stimulating factor) and RANKL (RANK receptor)
- M-CSF binds receptor on monocyte
- monocyte differentiates into macrophage
- macrophage releases RANK which binds RANKL (coupling cells)
- macrophage becomes immature osteoclast
Inhibition:
- osteoprotegerin binds RANKL prevents maturation of osteoclast
- calcitonin reduces bones resorption
