MCM Final - Structural Connective Tissue Flashcards
hyaline
cartilage type - articular surfaces, etc.
- most common
- clear cartilage that can resist compression
- matrix has collage type II fibers
Cartilage
rigid, flexible, and resilient
three types:
hyaline, elastic, and fibrous
cells - chondrogenic, chondroblasts, chondrocytes
fibers - collagen and elastic
ground substance - aggrecan (GAG) and chondronectin (adhesive glycoprotein
elastic cartilage
contain collagen type II
pinna and epiglottis
high concentration of elastic fibers
fibrous cartilage
aka fibrocartilage
pubis symphysis, intervertebral disks
has collagen type I
What cell type does cartilage develop from?
embryological mesenchyme
chondroblasts
cells in cartilage that will produce new cells
chondroblasts
cells in cartilage that are actively proliferating
chondrocytes
cells in cartilage that are not proliferating
lacunae in cartilage
chondroblasts become chondrocytes grouped together surrounded by matrix
-group of chondrocyte cells separated from matrix is lacunae
perichondrium
layer of irregular connective tissue around cartilage
- two layers:
- fibrous - outer layer
- cellular - inner layer
source of all future chondroblasts and chondrocytes
Cartilage Growth
-two types?
appositional - at the surface
-adds new cartilage at the periphery
interstitial - expansion of matrix from within
regulation of cartilage growth
growth hormone - stimulatory (insulin-like growth factor 1)
thyroid hormone - stimulatory (directly and IGF-1)
-stimulates hypertrophy
glucocorticoid - inhibitory
-down-regulate collagen type I
-up-regulate collagenase type III
testosterone - stimulate
estradiol - inhibitory
vitamin A deficiency - slows growth and calcification
vitamin C deficiency - inhibits collagen synthesis (scurvy)
vitamin D deficiency - inhibits calcification
Scurvy
result of vitamin C deficiency
-inhibits collagen synthesis
Wolff’s Law
bone adapt to the stress place on it
-change in bony structure
Bone composition
40% organic - collagen I (arranged radially each lamellar ring)
-polysaccharides, aggrecans, chondroitin-4,6 sulfate, heparan sulfate
60% inorganic - hydroxyapatite salt (calcium salt)
-plates that align with collagen fibers
lamellae
calcified interstital rings in bone
surround Haversian canal and are interspersed with lacunae
collagen in every other lamellae is perpendicular (extra strength)
lacunae
small cavities within each lamellae
contain osteocytes
canaliculi
tunnels between lamellae that allow osteocytes to receive nutrients
four types of lamellae
outer circumferential - below periosteum
osteon - haversian system, functional unit of bone
interstitial - remnants of old osteons
inner circumferential - immediately along the endosteum
osteon
Haversian canal surrounded by circular lamellae with lacunae connected by canaliculi
Haversian canal
contains blood vessels
runs parallel to longitudinal axis of bone
cancellous bone
spongy bones
- no haversian systems (no osten)
- have trabeculae and spicules
- lamellar structure
Volkmann’s canal
vascular channels at right angles to connect osteon vessels
periosteum
fibrous connective tissue sheath enveloping bone
- outer fibrous layer
- inner cellular layer
- contains undifferentiated osteogenic cells
- osteoprogenitor cells > osteoblasts > osteocytes
- contains undifferentiated osteogenic cells
sharpey’s fibers
anchor periosteum to underlying bone
-collagen fibers from outer periosteum layer embed in bone
endosteum
thin cellular layer lining bony walls of adjoining marrow cavity
- line all bone cavities (haversian canals and marrow spaces)
- have osteogenic potential
modulation
reversible change in cell function
differentiation
irreversible change in cell
osteoid
extracellular matrix of bone before it gets calcified
osteoblasts
arise from mesenchymal cells(embryo) and osteoprogenitor cells(adult)
lay down new bone
osteoprogenitor:
- nucleus is away from bony surface bc secreting things - cytoplasm basophilic (lots of acids > RNA )
osteocytes
reside within lacunae
maintain health of bone
participate in Ca2+ and PO4- transport
osteoclasts
large and multinucleated
though to arise from fusion of macrophages
bone resporption
Howship’s lacunae
location of osteoclasts
ruffled border
edge of osteoclasts
- lots of lysosomal vesicles and mitochondria - increased surface are for resporption
spicules
first deposition of bone
-spike - like a shard of new bone
multiple spicules merge into trabecule
trabeculae
bony spicules radiation from ossification centers
-spicules which have merged
mechanism of osteogenesis
intramembranous (mesenchymal)
endochondral
intramembranous bone formation
mesenchymal
occurs in flat bones of skull
pre-existing cells - mesenchymal cells, fibrous CT (collagen type I)
1 mesenchymal cells cluster, proliferate, and enlarge
2 differentiate into osteoblasts- secrete matrix which calcififes
3 cells trapped in lacunae - become osteocytes
endochoncral bone formation
occurs in long bones
1 start with cartilage
2 osseus cuff forms
3 calcification of midregion
4 death and resporption of central chondrocytes
5 blood bessels penetrate diaphysis - form marrow cavity
6 osteogenic cells migrate into cavity
7
four zones of epiphyseal plate
zone of long bone growth during endochondral osteogenesis
1 zone of resting cartilage - pool of chondrocytes (collagen type II)
2 zone of proliferating cartilage (stacked nickels) - rapid proliferation
3 zone of hypertrophying cartilage - slow proliferation
-production of collagen type I and VEGF (vascular recruiter)
zone of calcifying cartilage
-chondrocytes degenerate
-cartilagenous matrix calcified
-osteoprogenitor cells arrive via new vasculature
(also, zone of resorption/ossification)
-osteoblasts develop on cartilage spicules > new bone!
Process of Bone Healing
similar to osteogenesis
1 hyaline cartilage by chondrogenic cells
2 forms a callus
3 fracture heals, as new bony tissue laid down to replace cartilage
Regulation of Bone Growth
both hormone control and calcium level
-
3 ways to regulate Calcium metabolism
1 change in bone turnover
2 change in gut absorption
3 urinary secretion
calcitonin
inhibits bone resorption
-inhibits osteoclasts
produced by parafollicular cells of thyroid gland
-increase in Ca2+ > release of calcitonin
parathyroid hormone
increase resorption of calcium
affects osteoclasts indirectly
- binds osteoblasts and stimulates release of cytokine - cytokine increases osteoclast activity
secreted by chief cells of parathyroid gland
Vitamin D and Bone growth regulation
converted to circulating hormone
-calcitriol
regulate calcium and phosphate in blood stream
promotes calcium uptake in gut
produced in skin
ingested in food
