Connective Tissue Flashcards
CT vs. Epithelium
CT: widely spread, no polarity, vascularized (usually.. not cartilage)
general CT composition
cells + ECM
CT cells
long-term resident or transient resident
principal cell produces ECM components, all other cells do something else NOT produce ECM
Principal long-term resident cell
produces ECM components (ground substance + fibers)
usually fibroblasts
ECM components
- gelatinous ground substance + fibers/fibrils
- both parts produced by principal CT cell
Ground Substance
rich in GAGs and proteoglycans (interact to form proteoglycan aggregates)
secrete multiadhesive glycoproteins (stabilize matrix and aid in cell-connective tissue interactions)
GAG
Glycosaminoglycan
-long chain, linear polysaccharides
GAGs in CT
in ground substance: keratan sulfate, heparan sulfate, condroitin sulfate, and hyaluronic acid (hyaluronan)
- sulfate = negative (basophilic).. attracts sodium ions which attract water to the matrix
- interact with proteins to form proteoglycans
hyaluronic acid in ground substance
- longer and more rigid than other GAGs
- increases the viscosity of ground substance (makes it thicker)
proteoglycans
- linear proteins with glycosaminoglycan (GAG) side chains
- look like a bottle brush
proteglycan aggregate
proteglycan + GAG (hyaluronic acid)
mutiadhesive glycoproteins
- secreted by principal CT
- stabilize ECM and link EXM to the surface of cells
- ex: fibronectin and laminin (attach epithelial cells to basal lamina)
FIbrous component of CT
- proteins secreted from principal CT cells
- proteins assemble into fibrils (TEM), which usually assemble inter fibers (LM)
3 major types of fibers in connective tissue
- collagen
- elastic
- reticular (type III collagen)
constituency of CT
can be solid (bone) , watery (blood), or viscous (cartilage)
role of ground substance vs. fibers
fibers: tensile strength + resiliance
ground substance: diffusion of molecules + access of blood borne cells
fibroblasts (derived from? role in loose CT, function, in LM, in TEM)
derived from mesenchymal cells
PCT in loose CT
produce TYPE I COLLAGEN + ELASTIC FIBERS
in LM: elongated nucleaus, thin cytoplasm, and hard to tell (unless cell is making a lot of collagen)
in TEM: lots of rER (making proteins!), scalloped cell body, and thin processes extending from cell into collagen bundles
Macrophages (derived from? role in loose CT, function, in LM, in TEM)
derived from monocytes
-monocytes in blood, enter loose CT via diapedesis = macrophages
-function: resident phagocytic cells; phagocytosize bacteria or dying cells
in LM: larger nuclei than FB, and indented nuclear envelope, vesicles are apparent (foamy looking) when active
in TEM: lots of lysosomes, extending pseudo pods if active
mast cells
promote inflammation
granules in mast cells and their respective function
heparin (anticoagulant); histamine (promotes inflammation); eosinophil chemotactic factor tryptase (mast cell marker) NO leukotrienes (produced from PM after the release of granules)
uriticaria
hives;
produces from skin mast cell activation
explain inflammation response via mast cell (starting from antibody production) (DEGRANULATION OF MAST CELLS)
- antibody produced by plasma cell and released
- IgE specific receptor on extracellular mast cell bind the antibody to the mast cell
- antibodies bind to antigen (when present)
- ca 2+ channels open (calcium influx)
- granules pour out supstances: heparin (anticoagulant), histamine (promotes inflammation), eosinophilic chemotactic factor
- production of leukotrienes from PM (promotes inflammation)
“promote inflammation” = calls for leukocytes from blood vessel
leukocytes
promote immune response to antigens, parasites, or bacteria (that pass through epithelium)
-include granulocytes and agrangulocytes
cells in CT
- fibroblasts (produce collagen type I + elastic fibers)
- Macrophage (phagocytsize bacteria + old cells)
- Plasma cells (make antibodies)
- Mast cells (promote inflammation)
- adipose (energy storage, convert hormones to estrogen, weight control)
- leukocytes (promote immune response..WBC)
Loose CT ECM
produced from fibroblasts (PCT)
contain type I collagen, elastic fibers + viscous ground substance (sulfated and non-sulfated glycoasminoglycans
type I collagen
- most abundant type of collagen in humans
- most of loose and dense CT
- high tensile strength, but very flexible (links on a chain)
- best visualized with trichrome stain
how is type I collagen produced?
- from fibroblasts
1. FB secrete procollagen via constitutive exocytosis into ECM;
2. peptidase cleaves terminal end of procollagen = tropocollagen
3. tropocollagen proteins self assemble into collagen fibrils
4. fibrils assemble into eosinophilic fibers that are held together with proteoglycans
type IV collagen
- component of basal (external) lamina
- secreted by epithelial cells, adipocytes, schwann cells, muscle cells
- (also the anchoring protein in hemidesmosome)
Elastic fibers content/compostion
-made of elastic fiber, elastin (desmosine + isodesmosine), fibrillin, other glycoproteins
LITTLE HYDROXYPROLINE; NO HYDROXYLYSINE
function of elastin
stretchiness
function of fibrillin
organizing and structural protein
desmosine and isodesmosine
bind adjacent elastin molecule together to allow them to stretch and recoil
elastic fiber stain
orecein, resorcin fuchsin, aldehyde fuchsin, verhoeffs stain
Dense CT (Regular): location, structure
- in tendons/ligaments, type I collagen fibers are oriented linearly in direction to best resist stress
- poorly vascularized
- FB nucleus widely spread (compared to smooth muscle and peripheral nerve)
Dense CT (Irregular): location/structure
- in dermis of skin and capsule of other organs
- type I collagen is arranged into sheets and stacked. within each sheet the fibers are all lineraly aligned in one direction, but since the layers are stacked, it appears like they are going in all different directions (FB randomly w/in the collagen)
vit C and collagen?
vitamin C is a cofactor in the synthesis of type I collagen; deprivation of vit c greatly reduces collagen synthesis resulting in SCURVY (especially seen in the periodontal ligament anchoring teeth in their bone sockets.. loose teeth)
Loose CT vs. Dense CT
Loose: more cells less collagen
Dense: more collagen less cells
reticular fiber formation
via reticular cells: same as collagen I production (via FB):
-reticular cell secretes procollagen, cleaved to tropocollagen, assemble to collagen III fibrils, fibrils arrange into a mesh-bag network
reticular fiber stain
PAS (carbohydrates), silver
Ehlers Danlos Type IV Syndrome
insufficient synthesis of type III collagen… aorta and intestines have large amounts of type III.. thus they are very prone to rupture
Marfan’s syndrome
- caused by mutations in the gene for microfibrilar component of elastic Ct
- affects large vessels
- elastic wall of aorta is deficient and leads to rupture
fibers affiliated with adipocytes
reticular (collagen III) network
Mesenchyme
- loose, primitive CT found in embryo
- allows passage of cells and fluid within the organ
whartons jelly
found in umbilical cord
ground substance has lots of hyaluronic acid and sulfated GAGs that draws in water… makes the ground substance a good compression protection.. which prevents the umbilical cord from kinking
TYPE I +III collagen
Brown Fat
has multiocular fat cells (lots of lipid inclusions and lots of mitochondria… make it look brown). this fat is good for converting lipid into thermal energy type III collagen
cartilage (general)
- flexible CT that resists compression and provides an organizing framework for other cells
- avascular
- aneaural
3 types of cartilage
- hyaline
- elastic
- fibrocartilage
what type of cartilage is surrounded by perichondrium? what is perichondrium
- hyaline + elastic cartilage
- dense irregular CT (fibroblast) = outer layer
- chondrogenic layer of chondrocytes (produces chondrocytes) = inner layer
aggrecan
a proteoglycan that contains high concentrations of sulfated GAGs (keratan sulfate + chondroitin sulfate)
whats the advantage of sulfated gags?
bring in water (negative sulfate attracts sodium, which brings water with it).
this results in a ground substance that can resist compression
and in cartilage: allows free diffusion of material to/from blood vessels outside the cartilage
why is the matrix of hyaline cartilage basophilic?
lots of sulfated GAGs
Lacuna
space that contains a chondrocyte inside (visible in H/E after the cell shrinks)
-territorial matrix/interterritorial matrix
territorial matrix
borders the lacuna; appears darker because the GAGs (matrix material) is concentrated there… very basophilic
interterritorial matrix
between the groups of matrix; stains lighter (ie: if there are two chondrocytes/lacunae next to each other, then two dark circle around the chondrocyte = territorial matrix, and the little space between them is the interterritorial matrix)
Cartilage growth
2 ways:
- appositional
- interstitial
appositional cartilage growth
- growth at the edges
- chondroblasts in inner chondrogenic layer of perichondrium divide and add to cartilage along the outside
- “chondrogenic” cells of the perichondrium (i.e., the cells in the overlying CT that have the potential to become chondrocytes) gear up, begin active synthesis, and start creating new cartilage at the boundaries of the structure. Eventually these new chondrocytes will become trapped in lacunae and become integrated as part of the main mass of cartilage. At that point, if they’re still active in synthesis, they’ll be participating in interstitial growth.
interstitial cartilage growth
- growth from the inside
- mitosis of chondrocytes in lacunae produce isogenous groups of cells (clones) within the cartilage matrix
- result of chondrocytes in their lacunae actively synthesizing matrix material. This causes the total volume of the cartilaginous structure to increase
Fibrocartilage
combo of dense regular CT + chondrocytes (no perichondrium)
- function as a strong anchor for dense CT
- in public symphosis, intervertebral discs, meniscus of knee etc.
cartilage repair
damaged cartilage is largely incapable of repair.. avascular! few chondrocytes are added following damage (most repair is done by producing more dense CT)
hyaline cartilage can ossify as a part of normal aging
ie: in tracheal cartilage
osteoarthritis
- erosion of the hyaline cartilage lining the articular surfaces of bones
- loss of aneural cartilage allows grinding of bony surfaces (highly innervated .. produce intense pain
chondroma vs. chondrosarcoma
chondroma = benign tumor formed by chondrocytes chondrosarcoma = malignant
PCT in Loose CT
fibroblast
fibers in Loose CT
type I collagen + elastic fibers
ground substance in Loose CT
sulfated and nonsulfated GAGs
PCT in dense CT
fibroblasts
fibers in dense CT
type I collagen mainly (some elastic)
in regular: all run in the same direction
in irregular: run obliquely
ground substance in dense CT
minimal - GAGs
PCT in reticular CT
reticular cells (lymphatics), schwann cells, adipocytes, muscle cells
fibers in reticular CT
type III collagen
ground substance in reticular CT
minimal- GAGs
PCT in elastic CT
fibroblasts, chondrocytes, smooth muscle
fibers in elastic CT
elastic fibers mainly
- elastin = fiber component
- fibrilin = microfibril component
ground substance in elastic CT
minimal- GAGs
PCT in adipose
adipocytes
fibers in adipose
reticular fibers (type III collagen)
ground substance in adipose
minimal - GAGs
PCT in mesenchyme CT
mesenchymal cells
fibers in mesenchyme
type III collagen
ground substance in mesenchyme
abundant: thin, gelatinous
PCT in Wharton’s Jelly
mesenchymal cells
fibers in Wharton’s Jelly
type III collagen fibers (reticular) + type I collagen
ground substance in Wharton’s Jelly
Jelly- like
lots of hyaluronic acid + sulfated GAGs cause an influx of water.. its good for compression
PCT of brown adipose tissue
multilocular adipocytes rich in mitochondria
fibers of brown adipose tissue
type III collagen fibers (reticular fibers)
ground substance of brown adipose tissue
minimal - GAGs
hyaline cartilage PCT
chondrocyte
fibers in hyaline cartilage
type II collage FIBRILS
ground substance in hyaline cartilage
aggrecan (high concentration of sulfated GAGs (keratan sulfate + chondroitin sulfate))
PCT in elastic cartilage
chondrocyte
fibers in elastic cartilage
type II collage FIBRILS
elastic FIBERS
ground substance in elastic cartilage
aggrecan
PCT in fibrocartilage
chondrocyte + fibroblast
fibers in fibrocartilage
type II collagen FIBRILS
type I collagen FIBERS