Connective Tissue Flashcards
two groups of CT
nonspecialized - loose and dense CT
specialized - adipose, cartilage, bone, blood
components of CT
ECM
Nonpolarized cells
what properties does ECM impart on connective tissue
elasticity (elastic fibers)
tensile strength (fibrous collagens)
resilience (proteoglycans)
what are the three major functions of CT
defense
support
nutrition, transport, storage
What are the two components of ECM
ground substance
fibrous proteins
What are the two components of ground substance?
proteoglycans
glycoproteins
what is the ground substance three functions
retain water
matrix between cells and fibers
anchor cells to matrix and allow them to move
what is the general structure of proteoglycans
core p
negatively charged, long disaccharides
what is unique about hyaluran (a glycoprotein)
no core p
linker p binds many HA to a core p
giant aggregates bind fibrous elements of ECM (collagen fibers)
what are the three functions of glycoproteins
cell-to-cell recognition
adhesion
migration
what is the general structure of glycoproteins
mostly protein
short polysaccharides, branched, diverse
what are the three main binding sites on glycoproteins?
integrins (cells) collagen fibers (ECM) proteoglycans (ECM)
what are two types of glycoproteins
laminin
fibronectin
what does laminin do and what secretes it?
binds proteoglycans, epithelial cell membrane, collagen IV (in lamina dense of basal lamina)
epithelial cells
what does fibronectin do and what secretes it?
mediates attachment of fibroblasts (or other cells) to collagen fibers, proteoglycans
give the general scheme for collagen formation
alpha chains in RER..
procollagen sent to golg, exocytosed..
terminal peptides cleaved giving tropocollagen..
self assembly
which collagen types form fibrils?
I, II, III
what collagen types form fibers?
I, III
what collagen type forms reticular fibers?
III
Type I: what cells synthesize it, where is it found? what is its function? what form does it take?
fibroblasts, osteoblasts
dermis, tendons, ligaments, bone, fascia, organ capsule, loose CT
resist force, tension, stretch
fibers
type 1 is also found in fibrocartilage. what cells synthesize it, what form does it take, and what is its function?
chondroblasts/cytes
fibers
resist force, tension, stress
Type II: what cells synthesize it, where is it found? what is its function? what form does it take?
chondroblasts
hyaline, elastic cartilage
resists intermittent pressure
fibrils
Type III: what cells synthesize it, where is it found? what is its function? what form does it take?
fibroblasts, smooth muscle, reticular cells, schwann cells, liver cells
soft tissue support network, lamina reticularis of basement membrane, hepatocyte support, lymph nodes
structural support, elasticity, wound repair
fine fibers, reticular fibers
what do reticular fibers do? (III)
delicate for support of lymph nodes, bone marrow, spleen
slow fluid flow so Ag can be recognized and phagocytosed
Type IV: what cells synthesize it, where is it found? what is its function? what form does it take?
epithelial cells, muscle cells, schwann cells
lamina densa of basal lamina, external lamina
support and filtration
no fibers, no fibrils
elastic fibers: what cells synthesize them, where are they found?
fibroblasts
lungs, walls of large arteries, elastic ligaments between vertebrae
discuss the general structure and composition of elastic fibers
elastin deposited on microfibril bed of fibrillin.
cross-link to form elastic fiber
relaxed – randomly coiled
stretched – organized
typically associate with collagen fibers
what are the four cells of CT
fibroblasts
macrophages
mast cells
adipocytes
what are the four functions of CT cells
defense, support, metabolism, tissue repair
function of fibroblasts
synthesize collagen fibers elastic fibers proteoglycans hyaluronan glycoproteins organize
what are fibroblasts called in cartilage? bone?
chondroblasts
osteoblasts
fibroblast morphology?
nucleus - large, oval, pale, nucleolus
irregular shape
solitary
abundant cytoplasm (active), non-abundant (inactive)
fibroblast origin?
mesenchymal cells form fibroblasts, osteoblasts, chondroblasts, or adipocytes
what is unique about myofibroblasts?
take on contractile properties when activated from tissue damage
function of macrophages?
acute inflammation, phagocytosis
what do macrophages do in acute inflammation?
release IL-1 –> chemotactic for neutrophils and proliferation of fibroblasts
proliferation of B cells
what triggers phagocytosis
recognizes Fc and C3b (opsonized pathogen)
what are macrophages called in liver, lymph nodes/spleen, cartilage, and bone?
kupffer cells
reticuloendothelial cells
chondroclasts
osteoclasts
macrophage morphology?
bipolar darkened nucleus infoldings in plasma membrane irregularly sized phagocytic vacuoles electron dense granules
macrophage origin?
when monocytes leave bone marrow and circulate, become macrophage
what is the function of mast cells?
detect Ag entry in lamina propria and elicit local inflammatory response
what 6 substances do mast cells release?
histamine heparin slow reacting substand of anaphylaxis eosinophil chemotactic factor neutrophil chemotactic factor tumor necrosis factor-alpha
how do mast cells detect pathogen and respond?
on first exposure, IgE component of Fc binds to mast cell
on second exposure, Ag binds and crosslinks w/ mast cell IgE –> release of factors
mast cell origin and location?
bone marrow then migrates to CT and stays
mast cell morphology/
discrete cell boundaries
round oval cell
uniformly sized secretory granules
what are the three types of non-specialized CT
Loose
Dense irregular
dense regular
what is the predominant collagen in non-specialized CT
type I
loose CT: where is it found, what is it’s composition and characteristics? (5)
Beneath epithelia Binds different tissue types Large proportion of cells Sparse elastic and coll fibers Abundant ground substance
dense irregular: where is it found, what is it’s composition and characteristics? (3)
where more mechanical stress or required support
irregular orientation of abundant collagen fibers
fewer cells, ground substance
dense regular CT: where is it found, what is it’s composition and characteristics? (5)
Mechanical stress greatest Regular orientation of abundant coll fibers Minimal ground substance Fibroblasts squeezed between fibers Tendons, aponeuroses, ligaments
what are the four types of specialized CT
adipose tissue
cartilage
bone
blood
three functions of adipose tissue
lipid storage
heat production
hormone secretion
adipocyte origin?
mesenchymal cells
two types of adipocytes?
unilocular white
multilocular brown
5 functions of unilocular white adipocytes
energy storage shock absorption insulation hormone secretion organ positioning
how are white adipocytes shaped and organized?
intracellular - single fat droplet surrounded by intermediate filaments
polyhedral cells bound by reticular fibers
each cell surrounded by external lamina
what are 4 substances released by white adipocytes for their endocrine function?
leptin (appetite, energy balance)
resistin (insulin resistance)
plasminogen activator inhibitor 1 (predicts typeII diabetes)
pro-inflammatory cytokines (TNFalpha, IL-6, IL-8)
brown adipocyte morphology?
many fat droplets
numerous mitos, capillaries
polyhedral but smaller than white
centrally located nucleus, rounded
white adipocyte morphology?
thin cytoplasm surrounding empty fat vacuole (on histo)
elliptical, flat nucleus squished to edge of cell
function of brown adipocytes
nonshivering thermogenesis
5 functions of cartilage?
support soft tissues shock absorption structural framework of organs allow smooth movement of skeletal elements at joints lay down skeletal model in embryogenesis
composition of cartilage?
ECM
chondroblasts, chondrocytes
what is lacking in cartilage?
nerves, blood vessels, lymphatic vessels
how does cartilage get nutrients
diffusion of surrounding fluids facilitated by negatively charged proteoglycans
how is cartilage organized?
surrounded by perichondrium which contains perichondrial fibroblasts embedded in dense irregular CT of collagen I and proteoglycans
what is the glycoprotein that connects chondrocytes to ECM?
chondronectin
what are the two steps in appositional growth?
- perichondrial fibroblasts and mesenchymal cells differentiate into chondroblasts
- chondroblasts synthesize cartilage matrix
what is the cartilage matrix composed of?
hyaluronan
collagen II
chondroitin sulfate
keratin sulfate
how does interstitial growth work?
deep chondrocytes divide giving isogenous groups and synthesize cartilage
as isogenous groups synthesize cartilage the chondrocytes separate
what are the two identifying characteristics of hyalin cartilage?
- composition: hyaluronan, collagen II, chondroitin sulfate, keratin sulfate giving amorphous appearance
- perichondrium, isogenous groups
what is lacunae?
space in cartilage for chondrocytes
where is hyalin cartilage found?
articular surface of joints
costal (ribs) locations
structural elements of trachea and larynx
what is unique about elastic cartilage?
has elastic fibers
where is elastic cartilage found?
pinna of ear, external auditory meatus, nose, epiglottis
what are identifying characteristics of fibrocartilage?
- collagen I in bundles. run parallel, woven
- chondrocytes, isogenous groups in lacunae
- no well-defined perichondrium, scarce ECM
- resembles and merges with dense CT
where is fibrocartilage found and what does it do?
in intervertebral disks, replaces damaged hyaline cartilage
what causes scurvy?
vitamin C deficieny which is needed for hydroxylation of collagen residues
what is the symptoms of scurvy?
abnormal bone growth
poor fracture healing
tendency to bleed
what is the cause of marfan syndrome?
fibrillin defective/missing
what is the consequence of marfan syndrome?
progressive dilation of ascending aorta and subluxation of lens.
eventually get a ruptured aorta from defective elastic membranes
what is the cause of osteoarthritis?
degenerative disease of hyalin cartilage
- cracks and tears in articular surface
- proteoglycan content decreases
- chondrocyte proliferation decreases
