Cartilage and Bones Flashcards
(44 cards)
What 3 functions is cartilage structurally designed to do?
-withstand tension & compression
-provides low friction surface at joints and
to provide support to soft tissue.
-Provide a framework for long bone osteogenesis (during development).
Functional difference between chondrocytes and chondroblasts
- Chondroblasts produce new matrix until skeleton stops growing. They are ‘immature/undifferentiated’
- Chondrocytes are found in groups in cavities called lacunae. They are ‘mature cells’ and are less active.
5 differences between cartilage and bone
Cartlage is:
- More flexible
- Avascular (less blood supply, thus heals very slowly)
- Less organized structure
- No nerve fibers
- Composed of up to 80% water
How are nutrients provided to cartilage?
Via diffusion through the perichondrium
What is the perichondrium?
A fibrous connective tissue sheath that contains:
- Type I collagen fibers
- Vascular supply for collagen
- Chondrogenic cells
- perichondrium is NOT found in all cartilage types
Main difference between 3 different types of cartilage
- cell distribution and number
- type of fiber in the matrix
What two main fibers are found in cartilage?
1) collagen fibers - stronger than steel fibers of the same size
- Thin fibers - hyaline cartilage
- Thick fibers - fibrocartilage
2) elastic fibers
- elastic cartilage
3 main components of cartilage
Cells, fibers, and ground substance
What does ground substance of cartilage consist of, and what is the main function?
- contains water, glycosaminoglycans, glycoproteins, and proteoglycans
- proteoglycans are aggregates of chondroitin sulfate and hyaluronic acid
- functions to generate electrostatic repulsion and resist compression
What is caused by the loss of chondroitin sulfate in cartilage ground substance?
osteoarthritis
Explain proteoglycan repulsion
occurs between negative fixed charges on adjacent glycosaminoglycan molecules
Main functions of hyaline cartilage
- absorbs mild compression, provides support, flexibility, and resilience
- weakest of the 3 types of cartilage
- most widespread type
simple composition of hyaline cartilage
- has perichondrium
- has spherical chondrocytes
- type II collagen fibers
- no nerves or blood vessels
4 hyaline cartilage locations
- articular cartilages - end of long bones
- costal cartilage - ribs/sternum
- respiratory cartilage
- nasal cartilage
What is ossification?
The process of hyaline cartilage turning into bone
-chondroblasts die and are replaced by osteoblasts in ossification centers
Characteristics of fibrocartilage
- strongest type of cartilage
- contains both type I and type II collagen
- lacks perichondrium
- highly compressible
- located at sites subject to pressure & stretch
Characteristics of elastic cartilage
- resembles hyaline cartilage, but more stringy
- contains perichondrium
- network of elastic fibers within matrix in addition to type II collagen fibers
- found in external ear and epiglottis
5 functions of bone
- support
- protection
- assisting movement
- mineral homeostasis
- blood cell production
What 3 hormones regulate calcium homeostasis?
- parathyroid hormone
- 1,25-dihydroxycholecalciferol
- calcitonin
Characteristics of parathyroid hormone
- secreted by chief cells of parathyroid glands
- mobilizes calcium from bone
- increases urinary phosphate excretion
characteristics of 1,25-dihydroxycholecalciferol
- formed from vit D in skin via sun, and from liver and kidneys
- increases calcium absorption from intestine
- increases calcium in bone
characteristics of calcitonin
- calcium lowering hormone secreted by parafollicular cells in thyroid gland
- inhibits bone resorbtion
Interaction of PTH and calcitonin
- PTH increases blood levels of calcium when plasma levels get too low
- calcitonin decreases blood levels of calcium when plasma levels get too high
Regulatory feedback between vit D and PTH
- PTH helps activate vit D to 1,25-dihydroxycholecalciferol in kidney
- 1,25-dihydroxycholecalciferol can then downregulate PTH release
