Cartilage and bone physiology Smith Week 2 Flashcards
what type of cells make up cartilage?
chondrocytes
cartilage is structurally designed to do what 4 things?
- withstand tension and compression
- provide low friction surface at joints
- provide support to soft tissue
- provide a framework for long osteogenesis during development
how is cartilage different from bone?
- more flexible
- avascular
- less organized structure
- no nerve fibers
- composed of up to 80% water
how do nutrients get into the cartilage?
via perichondrium
what is the perichondrium made of?
- fibrous connective tissue sheath
- type I collagen
- vascular supply
- chondrogenic cells
- no present in all types of cartilage
what are the 3 types of cartilage in the body?
- Hyaline-along axial skeleton
- Fibrocartilage-meniscus, pubic symphisis, and intervertebral disks
- Elastic cartilage-external ear, and epiglottis
fiber types in hyaline cartilage
type II collagen fibers only
fiber types in fibrocartilage
type I and II collagen
fiber types in elastic cartilage
elastic fibers, and type II collagen
what does chondoitin sulfate, a proteoglycan, do in cartilage?
provides much of the resistance to compression via electrostatic repulsion
*loss of chondoitin leads to osteoarthritis *
collagen II bound to proteoglycan aggregates made up of chondroitin sulfate linked to hyaluronic acid is what provides repulsion force in you cartilage? T/F
True
hyaline cartilage
most widespread type of collage weakest of the three types of collagen looks like frosted glass *has a perichondrium *has spherical chondrocytes *made of type II collagen *no nerves or blood vessels
Fibrocartilage
strongest of all the cartilages
- contains both type I and II collagen
- more fibers than cells
- lacks a perichondrium
- highly compressible
- menisici of knee, intervetebral discs, and pubic symphysis
Elastic cartilage
resembles hyaline cartilage but is more springy
- contains collagen type II and elastic fibers
- has a perichondrium
- only found in external ear and epiglottis
axial skeleton composition
skull, vertebrae, ribs and sternum
five functions of bone
support protection assist in movement mineral homeostasis blood cell production
Bone compared to cartilage
- both contain living cells with occupy cavities called lacunae
- contain a fibrous connective tissue covering
- bone is highly vascularized
- bone contains more collagen
- all bone growth is by apposition or by deposition on an already existing surface
adult bone is composed lamellae and are arranged to form types of bone
compact or cortical-most of bone in body 80%
trabecular or spongy 20%
what do osteoclasts do?
bone resorption(breakdown) by creating SEALING zones and in part lowers the pH which dissolves hydroxyapatite and collagen.
do osteoblasts build or break down bone?
build
Bone calcium is available from two reservoirs, what are they?
exchangeable and stable. Most is in the stable form and is released slowly where the exchangeable is readily available
where are the four places we get calcium and phosphorus from?
bone, kidneys, GI and diet.
*most of the calcium and phosphate in the body is in the bone
parathyroid hormone (PTH)
- secreted by chief cells of the parathyroid gland
- mobilizes calcium from bone and increases calcium in blood
- increases urinary phosphate excretion and *increases calcium reabsorption
1,25-dihydroxycholecalciferol
aka calcitriol
is a steroid hormone formed from Vit. D n skin via the sun and successive hydroxylations in the liver and kidneys
- increases calcium absorption form the intestine
- increases calcium in bone
Calcitonin
lowers the calcium in blood via
- inhibiting bone resorption(breakdown)
- inhibiting calcium absorption by the intestine
- stimulates osteoblastic activity in bones
- inhibits reabsorption of calcium in kidney
- secreted by the parafollicular cells in the thyroid gland
regulatory feedback between Vit D and PTH
- PTH helps activate Vit D to 1,25-dihydroxycholecalciferol in kidney
- then it can down regulate PTH release
osteopetrosis
osteoclasts are defective and unable to resorb bone, so osteoblasts operate unopposed. bone over growth
osteoperosis
relative excess of osteoclast function results in loss of bone matrix and high risk of bone fractures.
two causes: age and bisphosphinates(inhibit osteoclast activity, preventing resorbtion and increasing mineral content of bone.
