Histology: Connective tissue (lecture) Flashcards
What type of connnective tissue surrounds vessels and nerves?
loose CT (acts to fill and pack around)
T or F: dense CT has thinner fibers than loose CT?
False
What type of connective tissue is characterized by loose packing of its fibers?
Loose CT
What type of CT has large, closely packed fibers and contains cells that are mostly fibroblasts?
Dense CT
What are 4 areas where dense irregular CT can be found?
Stroma of organs
dermis of skin
periosteum and perichondrium
capsules of organs
What are 3 areas where dense regular CT can be found?
tendons
ligaments
aponeurosis
What does dense regular CT consist of?
fibroblasts in linear rows and paralel-oriented collagen fibers
What type of collagen is typically found in dense regular CT?
type I - resisted tensile stress
Where can reticular connective tissue be found? (5 places)
bone marrow lymph nodes lymph nodules spleen tonsils
T or F: reticular cells are modified fibroblasts?
True
What type of collagen makes up reticular fibers?
type III collagen
What allow special stains to be used in reticular fiber visualization?
Lots of carbohydrates
Compare reticular cells to fibroblasts
they are branching and have much more cytoplasm (they lie along the length of the reticular fiber)
What type of cells and fibers are most important in lymph nodes and blood forming organs?
Reticular cells
What is the earliest CT in the embryo?
mesenchyme - undifferntiated and can form all kinds of CT
T or F: mesenchyme contains sparse reticular fibers in an abundant ground substance?
True
T or F: Mesenchymal cells are non-existent in adulthood
False - they are more common in children but a smaller amount persist into adulthood
What is a pericyte?
adult mesenchymal cell that can give rise to fibrolasts and participate in new vessel formation during wound healing
How does CT participate in tissue repair in the body most often?
fibroblasts become myofibroblasts and mesenchymal stem cells
Describe what scar tissue is.
dense irregular CT that may compromise function (e.g. cornea)
What are myofibroblasts derived from?
fibroblasts
What cells are partly responsible for wound contraction?
myofibroblasts
T or F: myofibroblasts are intermediates between fibroblasts and smooth muscle because they contain actin.
True
How do myofibroblasts work?
They have proteins attached to collagen outside of cell and actin in the cell. The proteins move along actin and grip onto collagen to pull cells together
What happens as a clot forms in the skin?
macrophages and neutophils invade and clean up debris, dead cells, degrade ECM and collagen
What are growth factors in the wound produced by?
macrophages
What do growth factors in the wound stimulate?
fibroblasts and mesenchymal stem cells proliferate and re-synthesize ECM (sometimes scar = hyperprolferative)
T or F: collagen metabolism is low in adults
True - degration and deposition = usually equal
In what adult tissue is collagen metabolized at a higher rate?
scar tissue
What types of cells modulate collagen degradation?
Fibroblasts, macrophages, neutrophils = collagenases
What affect does scruvy have on collagen deposition and degradation?
It increases the rate of collagen degradation by collagenases
Scars begin to open
What causes scurvy?
Lack of Vit. C - cofactor needed for the hydroxylation of proline and lysine in collagen
What is the disease that causes overproduction of tissue as a result of minor injury?
Keloids - collagen sythesis out of control
What are common causes of liver fibrosis?
viral infections, alcohol
T or F: there is a great amount of ECM in fat cells?
False
Where are 4 places that adipose connective tissue is commonly found.
subcutaneous tissue (skin)
around kidney
around vessels of the heart
in mesenteries (abdomin)
What type of cells contain only a single droplet of fat?
White adipose tissue
How are triglycerides and very low density lipoproteins (VLDL) delivered to fat cells?
transported by blood from intestin and liver and broken down into fatty acids and glycerol that diffuse into adipocyte to reform triglycerides
What is leptin?
adipokine that regulates appetite in mice
Why might leptin be unaffective in humans?
target cells in hypothalmus etc. may have insufficient receptors or post-receptor signal transduction
What factors characterize metabolic syndrome?
central obesity high BP (cardiovascular disease) High triglycerides low HDL insulin resistance (diabetes)
What does metabolic syndrome look like?
lots of weight around the belly
What type of adipose tissue is multilocular?
Brown adipose
where is brown adipose tissue most commonly found?
hibernating animals and infants because it helps regulate body temp
Is multilocular fat associated with disease?
NO
What do mast cells look like?
Oval cells with a small oval nucleus
Filled with small membrane bound granules
Where are mast cells found in the largest numbers?
along the course of small blood vessels
Why are granules not typically seen in sectioned material?
because they are water soluble
What do mast cell granules contain?
Heparin (anticoagulant),
Histamine
Slow reactive Substance of Anaphylaxis (SRSA)
What are the biological effects of histamine?
vasodilation
increased capillary and venule permeability
What are the biological effects of SRSA?
increases smooth muscle contraction
What do endothelial cells do in the presence of histamine?
develop gaps between them and they leak fluid from vasculature into the tissue (edema)
What are Hurler, Sanfillipo, and Morquio syndromes?
Ground substance diseases where deficiency in lysosomal enzymes (Hydrolases) that degrade proteoglycans and glycosaminoglycans resulting in intracellular accumulation of these thing
What are symptoms Hurler, Sanfillipo, and Morquio syndromes?
mental retardation, growth and heart abnormalities, shortened lifespan
What causes Marfan Syndrome?
genetic defect in fibrillin gene causing abnormal elastic fibers
T or F: people with marfans have an additional risk of aorta rupture and blurred vision?
True - aortic rupture = due to lack of elastic recoil
T or F: elastic fibers are generally thinner than collagen fibers?
T
What are elastic fibers composed of?
fibrillin and microfibrils
where is elastin located?
Dermis of the skin, CT of lung (recoil during exhalation), elastic cartilage, larger arteries
What is Ehlers-Danlos and what are its symptomes?
genetic disorder of CTs, people typically have overly flexible joints, stretchy fragile skin, fragile BVs, propensity for dislocations
What type(s) of collagen are affected by classical ehlers-danlos syndrome?
Type V
What type(s) of collagen are affected by hypermobility ehlers-danlos syndrome?
Type III, Tenascin-XB (extracellular protein)
What type(s) of collagen are affected by vascular ehlers-danlos syndrome?
Type III
