CT Flashcards

1
Q

Constituents of CT

A

In ECM: fibers (elastic, reticular, and collagen) and ground substance (GAGs, proteoglycans, and glycoproteins)

Resident cells: fibroblasts, mesenchymal, adipocytes, chondrocytes, osteocytes, and mature mast cells

Migrating cells: macrophages, monocytes, lymphocytes/plasma cells, immature mast cells, and granulocytes

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2
Q

CT Cytoskeletal Elements

A

In contrast, intracellular cytoskeletal elements consists of microtubules, intermediate filaments, and microfilaments (actin).
Fibroblasts: flat and skinny; heterochromatic and flat nucleus; make different fibers, but do not confuse with cellular elements that are already there like microtubules
Gel like matrix to allow for hydration and flexibility

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3
Q

5 Major Types of Collagen

A

Each collagen is a triple helix made of amino acids arranged in alpha chains; ground substance of proteoglycans

Type I: skin, bone, cornea, and tendons

Type II: very fine and found in all types of cartilage

Type III: reticular fibers and very thin; found in loose CT, support for glands, lymph, and spleen

Type IV: found in sheets in basement membrane (seen in light microscope) or lamina (see basement membrane in eletron microscope and see different layers)

Type VII: anchoring fibrils in basement membrane

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4
Q

Reticular Fibers

A

Thinner (0.5-2 um diam)

type III collagen - form a fine, supportive meshwork; in liver, spleen, lymph node

higher carbohydrate content than other collagen fibers

supportive framework for some organs and glands: lymph nodes, spleen

Usually need special stains (silver or PAS) to see reticular fibers in the light microscope.

Ground substance made of glycoproteins

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5
Q

Elastic Fibers

A

Extremely thin (0.2-1 um), coiled, branching fibers
non-collagenous
Microfibrils of fibrillin embedded in an amorphous core of elastin (glycoprotien)
Relatively rigid regions alternate with random-coil structure resilience or elasticity
May be stretched up to 150% of resting length without tearing
Require special staining to be seen in LM
Provide elastic support of arteries, trachea & mesenteries
Ground substance made of GAGs

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6
Q

Marfan Syndrome

A

Marfan Syndrome – mutations in the fibrillin gene FBN1; autosomal dominant

Because large arteries contains lots of elastic fibers, Marfan patients often experience aortic rupture (life-threatening).

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7
Q

Ground Substance

A

a gel-like matrix rich in tissue fluid composed of:

A. Proteoglycans – ex: aggrecan, syndecan

B. Glycoproteins – globular proteins with attached branched chains of monosaccharides; ex: collagen, elastin, fibrillin, fibronectin, laminin

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8
Q

Proteoglycans

A

proteins covalently linked with glycosaminoglycans (GAGs)

GAGs – long, unbranched polysaccharides made of repeating disaccharide units
frequently sulfated which, with carboxyl groups high negative charge.
Thus, stain how in H&E stain?

Common GAGs: keratan sulfate, chondroitin sulfate, hyaluronan

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9
Q

Proteoglycan Properties

A

Neg charge

Occupy large volumes

Mobilize water

Make solutions viscous (e.g., mucus) or even rigid

Remain porous

Supportive & lubricating in cartilage and joints

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10
Q

Matrix Metalloproteases (MMPs)

A

Collagenases & gelatinases secreted by invading organisms or tumor cells; digest the ECM

ECM will provide a barrier to infectious organism and tumors
Tumors have developed ways to infiltrate ECM by secreting matrix metalloproteases (MMPs) and are enzymes that chew up the ECM so tumor can invade into epithelium
Neutrophils and other WBCs also can also secrete MMPs to get to sites of infection

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11
Q

Glycoproteins

A

ex: fibronectin, laminin, others; entactin/nidogen in basal lamina
attachment and migration of cells along ECM
protein component is more important for biological activities than the sugar
are short, have branching, smaller, and medium sugar content

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12
Q

Fibronectin

A

ECM glycoprotein synthesized by fibroblasts and some epithelial cells.

helps mediate cell adhesion and migration

two large polypeptides disulfide-bonded together at the carboxyl end.

contains specific binding regions for fibrin, heparin, fibrinogen, collagen, and eukaryotic cells

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13
Q

Laminin

A

ECM glycoprotein with cross like structure

Promotes adhesion of cells to basal laminae

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14
Q

Cell - ECM Interactions

A

Cell-surface molecules (integrins) bind to fibronectin, laminin, and collagens in the ECM

Integrins are poking out of the membrane and into the ECM and binds to proteins (laminins and fibronectins)
As the integrin binds to different things in ECM, signals cell actin molecules to get longer and extend to help move the integrins around the cell; be able to regulate cell movement and shape by integrins getting an idea of what is going on in the ECM

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15
Q

Integrins

A

transmembrane glycoprotein;

Links ECM proteins (collagens, laminin, fibronectin) with the intracellular cytoskeleton (actin, intermediate filaments)

Regulate cell adhesion, control cell movement and shape

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16
Q

Loose vs. Dense CT

A

Loose: lots of cells, relatively few fibers, fibers not in thick
bundles

Dense: few cells, abundant fibers, thick bundles of type I
collagen fibers; regular and irregular types

17
Q

Loose/Areolar CT

A

Fibers: loosely arranged; not bundled into thick units; thin & relatively sparse collagen fibers

Cells: abundant, various types, widely dispersed

Ground substance: volume > that of fibers; viscous to gel-like

ECM for diffusion of nutrients, gases; battleground for immune system

Loose CT found beneath epithelia; widely distributed
adipose tissue = fat cells in loose CT

18
Q

Dense Irregular CT

A

Fibers: abundant and randomly arranged bundles mostly of type I collagen

Cells: few; usually a single type, the fibroblast

Ground substance: sparse

Located: in dermis of skin and capsules around organs

19
Q

Dense Regular CT

A

Fibers: densely packed, parallel bundles of type I collagen
Cells: few; fibroblasts mainly
Ground substance: sparse
Located in tendons, ligaments, aponeuroses