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Cell & Tissue Biology > L12: Connective Tissue > Flashcards

L12: Connective Tissue Flashcards

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1
Q

Elements of CT

A
  • Cell types: fixed and migratory
  • ECM: ground substance (water, proteoglycans, glycosaminoglycans and multiadhesive glycoproteins) and fibers (elastic, collagen and reticular)
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2
Q

What are the functional attributes of CT?

A
  • Structure
  • Defense/protection
  • Nutrition
  • Fat depot (for cushioning, insulation, energy reserve)
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3
Q

Embryological origin of cells of CT

A
  • Mesoderm

- Ectodermal neural crest

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4
Q

List of fixed cells found in CT

A
  • Fibroblasts (active and quiescent known as fibrocytes)
  • Myofibroblast
  • Adipocytes
  • Mast cells
  • Macrophages
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5
Q

List of migratory/transient cells found in CT

A
  • Plasma cells

- Leukocytes (NLMEB)

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6
Q

Fibroblast: distinguish between active and quiescent, function, histological attributes

A
  • Active fibroblast: large, large amount of cytoplasmic processes (star-shaped) – large rER volume, many mitochondria, euchromatic nucleus, basophilic cytoplasm, nucleoli visible?
  • Quiescent fibroblast: small, fewer amount of cytoplasmic processes, heterochromatic nucleus, acido/eosinophilic cytoplasm, nucleoli not visible
  • Active fibroblasts synthesize and secrete fibers (incl. collagen) and ground substance. Quiescent fibroblasts have ability to do so when stimulated.
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7
Q

Briefly discuss synthesis and secretion of collagen

A
  • Procollagen alpha chains containing propeptides are synthesized
  • Hydroxylation of prolyl and lysyl residues occurs in ER (Vit C dependent)
  • Glycosylated
  • Assembly of chains into triple helix
  • Soluble (since propeptide chains) transported to Golgi
  • Packaged into vesicles
  • Exocytosed to EC space, peptidases cleave terminal peptides transforming collagen into insoluble collagen molecules, which aggregate into fibrils
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8
Q

Function of cortisol as far as fibroblasts are concerned?

A
  • Chronic administration of cortisol decreases activity of fibroblasts resulting in degradation of CT, including bone
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9
Q

What is a myofibroblast? Clinical relevance

A
  • Cells that possess characteristics of fibroblasts and smooth muscle (actin myosin present) cells
  • These are numerous in areas of wound healing
  • Dupuytren’s contracture: microvascular ischemia leads to trauma to palmar aponeurosis. As a result, tissue repair occurs involving fibroblasts and myofibroblasts. T1 collagen replaced with T3 collagen. T3 collage crosslinks with myofibroblasts causing contraction at the MP joints, commonly 4/5th digits.
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10
Q

Two types of adipocytes

A
  • Unilocular aka white adipocytes

- Multilocular aka brown adipocytes

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11
Q

Histological features of unilocular adipocytes

A
  • Large, single droplet not bound by membrane, ensheathed by vimentin filaments giving stipled effect at boundaries of droplet.
  • Nucleus pushed to periphery by droplet – signet ring appearance = thin boundary of cytoplasm with nucleus
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12
Q

What do adipocytes secrete? Function? Absence leads to what?

A
  • Leptin
  • Works in concert with other hormones to signal satiety, depress appetite
  • Absent/mutation leads to morbid obesity
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13
Q

What are lipodystrophies?

A
  • Disorders of lipid distribution in body and loss of body fat, in some cases due to defective lamins in nuclear envelope. These tend to be genetic in nature
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14
Q

Difference between brown and white adipocytes? Functionally?

A
  • White adipocytes have single fat droplet that serve as TGL store for energy needs of body
  • Brown adipocytes have multiple fat droplets, also ensheathed by vimentin. These are abundant in early development and serve to generate heat (decoupling in ETC). They are well-endowed with mitochondria therefore acidophilic. Nucleus is not displaced in these cells and is spherical.
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15
Q

Mast cells. Derived from what? Function – important chemicals? Histological features? Principle location?

A
  • Derived from bone marrow stem cells
  • Mediate inflammatory response and hypersensitivity reactions: Fc receptors present on cell allow cell to degranulate when bound to antigen/antibody complex. Histamine release causes tissue swelling and increased mucus production (eg. Nasal mucosa in hay fever). Leukotrienes can elicit bronchospasms in asthma. Allergic reactions to bee stings, drugs trigger release of mediators too. List: heparin, histamine, chondroitan sulfates, proteases, chemotactic factors – ILs, TNFs, leukotrienes, thromboxanes etc.
  • Histo: large ovoid cells (largest of fixed cells), multiple granules seen that are metachromatic
  • Location: located in CT proper adjacent to blood vessels and in subepithelial layers of respiratory and GI tracts. Not found in nervous tissue.
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16
Q

Difference between macrophages and monocytes?

A
  • Macrophages are monocytes that are non-travelling – they stay in the tissue where they have immigrated to. Monocytes travel through blood.
17
Q

Macrophages. Histological features, function?

A
  • Histological features: kidney-shaped (oval with indent) nucleus, nucleus has clumps of heterochromatin along border. Well endowed with Golgi, rER and lysosomes
  • Function: phagocytose cellular debris and microorganisms, present antigens to lymphocytes
18
Q

Discuss changes to macrophages in chronic inflammatory states

A
  • Activated macrophages morph into epithelial-like cells, which sometimes fuse to form giant, multinucleated cells (50+ nuclei sometimes) – nuclei at periphery – gives horse-shoe appearance
19
Q

Plasma cells. Derived from? Histological attributes? Function?

A
  • Derived from B lymphocytes
  • Histo: large oval-shaped cells with nucleus displaying heterochromatin in clock-like fashion around periphery, basophilic due to large volume of rER. Prominent negative Golgi image visible at light level next to nucleus
  • Function: synthesis and release of ABs, mediated by constitutive pathway (not stored), that function in immunological responses
20
Q

Name leukocyte cell types

A
  • NLMEB

- Neutrophils, lymphocytes, neutrophils, eosinophils, basophils

21
Q

Where are leukocytes found?

A
  • Blood compartment and can migrate in CT compartment, including being found bw epithelial cells
22
Q

Which leukocytic cells are found in inflammatory sites first? Second?

A
  • First wave = marines = neutrophils

- Second wave = monocytes

23
Q

Classes of CT

A
  1. ) Embryonic CT
    a. ) Mesenchyme
    b. ) Mucous
  2. ) CT proper
    a. ) Loose (areolar)
    b. ) Dense
    i. ) Dense irregular
    ii. ) Dense regular: collagenous and elastic
  3. ) Specialized CT
    a. ) Adipose
    b. ) Reticular
    c. ) Cartilage
    d. ) Bone
    e. ) Blood
24
Q

CT type = mesenchymal. Ground substance, fibers, cells, location?

A
  • Ground substance = abundant, gel-like filled with glycoproteins and GAGs
  • Fibers = reticular fibers scattered
  • Cells = mesenchymal
  • Location = embryonic intramembranous bone formation
25
Q

CT type = mucous. Ground substance, fibers, cells, location?

A
  • Ground substance = abundant, jelly-like containing hyaluronic acid and glycoproteins
  • Fibers = few collagen type I and III
  • Cells = fibroblasts
  • Location = umbilical cord (Wharton’s jelly), subdermal in embryo
26
Q

CT type = loose(aka areolar). Ground substance, fibers, cells, location?

A
  • Ground substance = abundant, big 3 of ground substance with hyaluronic acid
  • Fibers = loose array of collagen, reticular, elastic fibers
  • Cells = fibroblasts, macrophages, adipose, mast, undiff cells
  • Location = deep to epithelium, surrounds blood vessels
27
Q

CT type = dense regular collagenous. Ground substance, fibers, cells, location?

A
  • Ground substance = sparse, big 3 of ground substance with hyaluronic acid
  • Fibers = densely packed parallel type I collagen, scattered elastic
  • Cells = scattered fibroblasts between collagen bundles
  • Location = tendons, ligaments, aponeurosis
28
Q

CT type = dense irregular elastic. Ground substance, fibers, cells, location?

A
  • Ground substance = sparse, big 3 of ground substance with hyaluronic acid
  • Fibers = elastic forms thing fenestrated membranes, fibers branch and run parallel with one another, collagen is few
  • Cells = scattered fibroblasts
  • Location = ligamenta flava, suspensory ligament of penis, vocal ligament, arteries
29
Q

CT type = dense irregular. Ground substance, fibers, cells, location?

A
  • Ground substance = sparse, big 3 of ground substance with hyaluronic acid
  • Fibers = tightly packed type I collagen oriented in many axes, elastic fibers interspersed
  • Cells = scattered fibroblasts
  • Location = organ capsules, dermis of skin, sleeve around nerves
  • *Note: angry sea look
30
Q

CT type = reticular. Ground substance, fibers, cells, location?

A
  • Ground substance = little ground substance
  • Fibers = reticular fibers (type III collagen)
  • Cells = reticulocytes, others
  • Location = red bone marrow, liver, lymphatic tissue organs
31
Q

CT type = unilocular adipose. Ground substance, fibers, cells, location?

A
  • Ground substance = sparse
  • Fibers = reticular fibers bw adipocytes
  • Cells = white adipocytes
  • Location = abdominal cavity
32
Q

CT type = multilocular adipose. Ground substance, fibers, cells, location?

A
  • Ground substance = sparse
  • Fibers = reticular fibers bw adipocytes
  • Cells = brown adipocytes
  • Location = limited in fetus and newborn (back, shoulders), adult = limited
33
Q

Discuss elastin function besides in elastic fibers of ground substance

A
  • Elastin forms lamellae and laminae in blood vessels. This is not the same as elastic fibers, which requires microfibrils
34
Q

What are foam cells?

A
  • Macrophages that accumulate cholesterol in cytoplasm = foam cells. These are seen in biopsies of xanthomas and in arteries with atherosclerosis
35
Q

What is mucoid degeneration of ACL?

A
  • Pts present with knee pain or restricted movement at knee
  • Mucoid degeneration of ACL = congenital or acquired synovial tissue entrapment between ACL fibers. ACL has celery stalk appearance on MRI.
36
Q

What is Ehlers-Danlos?

A
  • CT tissue disorder of multiple subtypes due to defects of genes encoding collagen
  • Clinically depending on subtypes: varicose veins, aortic rupture, intestinal rupture, hyperelasticity of skin, rupture of eyeball, joint dislocation, hypermobility of joints, gum ulcerations, hemorrhages, etc.
37
Q

What are xanthomas?

A
  • Accumulations of lipid material, including cholesterol

Cell & Tissue Biology (18 decks)

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