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MTC Block 3 > 3 - Extracellular Matrix and Connective Tissue > Flashcards

3 - Extracellular Matrix and Connective Tissue Flashcards

1
Q

What are fixed cells? What are some examples?

A

Relatively stable populations of long-lived (weeks, months) cells that develop from mesenchyme.

Fibroblasts, which form from ECM, and adipocytes, which store lipids.

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2
Q

What are free/wandering cells?

A

Changing populations of specific defense cells (WBCs) that are short-lived (days) and enter the connective tissue from the blood vessels.

Macrophages, eosinophils, monocytes, lymphocytes, plasma cells, and mast cells.

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3
Q

What is extracellular matrix?

A

Hydrated gel-like substance with fibers embedded in it.

Dominant component of connective tissue.

Complex of non-living macromolecules manufactured by the cells of the tissue; exported by them in to the extracellular space.

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4
Q

What are five normal functions of connective tissue?

A
  1. Mechanical support/anchoring to organs
  2. Exchange of metabolites
  3. Storage of energy reserves (- lipids in fat cells
  4. Protection against infection - phagocytosis by macrophages
  5. Repair following injury - fibroblast secretion in wound healing
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5
Q

What is the ground substance of ECM made of? What are the fibers made of?

A

A mixture of GAGs and proteoglycans that resist compression.

Fibers: collagen and elastic for tensile strength

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6
Q

What types of tissue has high amount of extracellular matrix? Low?

A

High - connective tissue

Low - nervous tissue

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7
Q

What are adhesion glycoproteins in the ECM and what is their function?

A

Laminin and fibronectin, link the cell to the ECM by binding to integrins in the cell membrane.

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8
Q

What are glycosaminoglycans (GAGs)? What is their function in the ECM?

A

Long, inflexible polysaccharide chains made of repeating disaccharides.

Highly negative.

Amino sugar is usually sulfated and has carboxyl projecting from it.

Helps make a porous hydrated gel that absorbs compressive loads.

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9
Q

What are the four types of GAGs?

Which is prominent in loose supporting connective tissue?

A
  1. Hyaluronate
  2. Chondroitin sulfate and dermatan sulfate
  3. Heparan sulfate and heparin
  4. Keratan sulfate

Hyaluronate predominant in loose connective tissue.

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10
Q

What differentiates hyaluronic acid from other GAGs? When is it produced in large quantities?

A

It is not sulfated, single disaccharide unit consisting of long chains,

It doesn’t form covalent links to other proteins.

Large quantities during wound healing.

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11
Q

How do sulfated GAG chains interact with other proteins?

A

Covalently link with core protein in golgi to form proteoglycans with a bottlebrush appearance.

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12
Q

What are aggregan proteoglycans?

A

Proteins that bind to a hyaluronate backbone by link proteins to make cartilage and connective tissue.

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13
Q

What is the structure of collagen? How is it made?

A

Triple helix composed of three a-helix chains; usually repeat Gly-X-Y where X and Y can be any amino acid.

Made and secreted by fibroblasts.

  • Secreted as procollagen and cleaved by peptidases
  • Tropocollagen selassembles .
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14
Q

Where is type 1 collagen polymerized to? III? IV? VII?

A

Type 1: fibril

Type III: reticular fibers

Type IV: Sheetlike network (basal lamina)

Type VII: anchoring fibrils

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15
Q

What is osetogenesis imperfecta?

A

Defect in type 1 collagen, yielding easily fractured bones.

“Brittle bone”

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16
Q

What is chondrodysplasia?

A

Defect in type II collagen resulting in cartilage join deformities.

Usually results in dwarfism b/c growth plate does not make new bone cells.

17
Q

What is Ehlers-Danlos Syndrome?

A

Type III collagen mutation resulting in weak skin, fragile blood vessels, and hypermobile joints.

Minor injuries may result in gaping wounds, sprains, and dislocations.

18
Q

What are elastic fibers made of? How are they made?

A

Made of elastin and fibrillin proteins, elastin linked by lysines.

Elastin made by fibroblasts in the ECM: elastin core covered by sheath of microfibrils made of fibrillin.

19
Q

What is marfan syndrome?

A

Mutations in fibrillin gene resulting in weakening of connective tissues rish in elastic fibers.

Weakened tissues stretch, distort, and can tear. Aneurisms/ruptured vessels common.

20
Q

What is the structure of fibronectin?

A

A large glycoprotein heterodimer containing collagen, heparin and integrin separated by flexible hinge proteins.

21
Q

What is the structure of laminin? What is this the major component of?

A

Large glycoprotein made of three large polypeptide chains formong a cross pattern of one long and three short chains held by disulfide bonds.

Basement membrane (basal lamina).

22
Q

Where is the basement membrane found?

A

Under all epithelial cell sheets, separating epithelia from connective tissue.

MAde of type IV collagen, perlecan heparan sulfate, laminin, and entactin.

Collagen fibrils tether it to connective tissue.

23
Q

What are the three function of the basement membrane?

A
  1. Molecular filter
  2. Selective barrier to cells such as fibroblasts and endothelial cells
  3. Scaffolding for regeneration
24
Q

What are fibroblasts? What are they associated with? What do they look like?

A

Most abundant cells of connective tissue.

Synthesis of almost all ECM in connective tissue and is associated with collagen bundles.

Cytoplasm contains golgi and abundant RER for making collagen.

25
Q

What are myofibroblasts and where are they found?

A

In between a fibroblast and smooth muscle cell that contains actin filaments for shrinkage of scar tissue.

Found in areas of wound healing.

26
Q

What are adipose cells? What receptors do they have?

A

Fully differentiated cells that synthesize, store, and release fat as triglycerides.

Receptors for insulin, glucocoricoids, GH, and noradrenaline.

27
Q

What is White adipose tissue characterized by? Where is it found in the body?

A

Single, large lipid droplet (unilocular), surrounded by a thin rim of cytoplasm.

Heavily supplied with blood vessels.

20-25% of body weight, found in deep layers of the skin for insulation and structural support.

28
Q

What is brown adipose tissue characterized by? Where is it found?

A

Contains multiple small lipid droplets (multilocular); reddish due to capillaries and mito.

Newborns have it by neck and axilla, adults have very little.

29
Q

How do you calculate BMI?

A

weight in kg / heigh in meters squared

30
Q

What is the difference between hypertrophic obesity and hypercellular obesity?

A

Hypertrophic: accumulation and storage of fat in white adipose cells, which increase in size

Hypercellular: more severe, overabundance of adipocytes.

31
Q

What is leptin and what is its function?

A

Hormone secreted by adipocytes involved in regulation of appetite and adipose tissue mass.

32
Q

How does leptin regulate adipose tissue?

A
  • Binds receptor in hypothalamus
  • Activates SNS to release norepi
  • Causes shift from fat storage (TG) to mobilization (glycerol and FAs) and oxidation
33
Q

What is the main function of leukocytes? Name the types of leukocytes?

A

Provide the first line of defense against invasion by microorganisms and foreign substances.

Macrophages, neutrophils, eosinophils, lymphocytes, plasma cells, mast cells.

34
Q

What are the five types of connective tissue?

A
  1. Embryonic: mesenchymal and mucus
  2. Loose (areolar)
  3. Dense (irregular or regular)
  4. Reticular
  5. Adipose (white or brown).
35
Q

Describe embryonic mesenchymal connective tissue? Where is it found?

A

Gel-like ground substance with reticular fibers.

Only found in the embryo.

36
Q

What is the structure of loose (areolar) connective tissue? Where is it typically found?

A

Loose arrangement of fibers and dispersed cells, primarily fibroblasts and some WBCs in the ground substance.

Found under epithelia, organs, and around capillaries.

37
Q

What is the structure and irregular dense connective tissue? What is it’s function and where is it located?

A

Irregularly arranged collagen fibers with few cells.

Withstand tension from many directions, structural strength.

Located in the reticular layer of the dermis of skin, submucosa of GI tract, and in capsules of organs and joints.

38
Q

What is the structure of regular dense connective tissue? What is it’s function and where is it located?

A

Composed of coarse collagen bundles oriented in parallel sheets.

Great tensile strength when force is in one direction.

Attaches muscles to bones or muscle, and bones to bones.

39
Q

What is the structure of reticular connective tissue? Where is it located?

A

Network of reticular fibers (collagen type 3) in loose ground substance.

Located in lymphoid organs.

Supports the parenchyma of organs.

MTC Block 3 (20 decks)

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