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General - Histology πŸ”¬ > L5: Connective tissue cells > Flashcards

L5: Connective tissue cells Flashcards

1
Q

What is the function of CT?

A

The CT supports, surrounds, binds, and separates various tissues and organs.

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2
Q

What are the types of CT?

A

True(proper)β€”->loose and dense

Supportiveβ€”β€”>bone and cartilage

Liquidβ€”β€”>blood

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3
Q

What are the characters of white collagenous fibers?

A

❖ Color: the bundles are white in color.

❖ Strong and resist stretch.

❖ It forms wavy bundles.

❖ Can be affected by
 converted into gelatin by boiling
 Destroyed by acids & alkalies.

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4
Q

What are the components of CT?

A

-cells, fibres and matrix

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5
Q

How is white collagenous fibres seen under LM?

A

The bundles can be stained:
 Acidophilic with Hx & E.
 Blue with Mallory trichrome stain.
 Red with Van Gieson’s stain.V

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6
Q

How is white collagenous fibres seen under EM?

A

❖ Each collagenous bundle is formed of a group of fibers which are composed of fibrils.

❖ Each fibril is formed of tropocollagen molecules: -.
οƒœ Synthesized by Fibroblasts

οƒœ Length is 280 nm

οƒœ Each molecule is composed of 3 polypeptide chains twisted around each other to form a triple helix.

οƒœ The arrangement of tropocollagen molecules gives the fibril a cross banding appearance Structure

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7
Q

What are the types and sites of collagen?

A
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8
Q

What are the characters of yellow elastic fibers?

A

οƒœ Color: yellow.
οƒœ Elastic in nature
οƒœ The fibers branch & anastomose

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9
Q

How is yellow elastic fibre seen under LM?

A

οƒœ Hx & E.: acidophilic.
οƒœ Van Gieson’s stain: yellow.
οƒœ Ver-Hoff’s stain: black.

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10
Q

How are yellow elastic fibres seen under EM?

A

Each fiber is formed of:
 Amorphous protein in the center called elastin
 Microfibrils in the periphery called oxytalan fibers.

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11
Q

What are the sites of yellow elastic fibres?

A

οƒœ In the walls of arteries.
οƒœ In the trachea, bronchi, and bronchioles.
οƒœ Ligamentum flavum between vertebrae.
οƒœ Ligamentum nuchae in the back of the neck
οƒœSuspensory ligament of the penis

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12
Q

What is the structure of reticular fibers?

A

οƒœ They are very thin fibers that branch and anastomose to form a network.

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13
Q

How are reticular fibres seen under LM?

A

οƒœ Hx & E: not stained.
οƒœ Silver: brown to black (Agyrophilic)
οƒœ PAS: Magenta colored (polysaccharides).

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14
Q

What are the sites of reticular fibers?

A

οƒœ The stroma of parenchymatous organs e.g. Liver, spleen, and lymph nodes.
οƒœ Reticular lamina of the basement membranes.

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15
Q

What is the matrix composed of?

A

οƒœ Composed of three components:
1) Amorphous component.
2) Fibrous component
3) Tissue fluid

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16
Q

What is the amorphous part composed if?

A

οƒœ The amorphous part: formed of two main parts:
1) Glycosaminoglycans (gags)
2) Glycoproteins

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17
Q

GAGS in CT

A

Non-sulphated type (hyaluronic acid)

Soft jelly-like
Not linked to a core of protein
Can be hydrolyzed by hyaluronidase enzyme

Sulphated type (chondroitin sulphate)

hard
Linked to a core of protein forming proteoglycans.
Not affected.

οƒœ Stain: Metachromatic stain e.g., Toluidine blueβ†’reddish-purple in Color.

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18
Q

Glycoproteins in CT.

A

Act as adhesive material.

Examples:
 Chondronectin in cartilage.
 Osteonectin in bone.

οƒœ Stain: PASβ†’ magenta-colored.

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19
Q

What are fixed CT cells?

A

-undifferentiated mesenchymal cell
-fibroblasts
-adipocytes (fat cells or adipose cells)
-reticular cells
-macrophages (clasmatocyes or histiocytes)

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20
Q

What is the origin of the undifferentiated mesenchymal cell?

A

Mesodermal cells of the embryo

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21
Q

Can mesenchymal cells divide?

A

Yes

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22
Q

Are mesenchymal cells differentiated?

A

No

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23
Q

How is UMC seen under LM?

A

Cytoplasm: pale basophilic due to little ribosomes

Nucleus:clovesβ€”->central,vesicular,large,oval,single

Sites: pre-natalβ€”->in the embryonic CT
Post-natalβ€”->in decides teeth and in pericytes surrounding the blood capillaries

Shape: Branched with few cell processes which are thin and long

Number: common in embryonic CT (mucoid and mesenchymal)

Size: Tiny

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24
Q

How is UMC seen under LM?

A

Cytoplasm: pale basophilic due to little ribosomes

Nucleus:clovesβ€”->central,vesicular,large,oval,single

Sites: pre-natalβ€”->in the embryonic CT
Post-natalβ€”->in decides teeth and in pericytes surrounding the blood capillaries

Shape: Branched with few cell processes which are thin and long

Number: common in embryonic CT (mucoid and mesenchymal)

Size: Tiny

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25
Q

how is UMC seen under EM?

A

Mainly free polysomes (little rER and small Golgi)

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26
Q

What is the function of UMC?

A

It acts as a multipotent stem mother cell.

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27
Q

What are fibroblasts?

A

The most common type of C.T. cells that are responsible for the synthesis of C.T. matrix and fibers.

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28
Q

What is the origin of fibroblasts?

A

develop from pericytes (branched cells around blood capillaries) which develop from U.M.C.

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29
Q

Can fibroblasts divide?

A

No

30
Q

Are fibroblasts differentiated?

A

Yes

31
Q

How are fibroblasts seen under LM?

A

Cytoplasm: Deep basophilic with negative Golgi image

Nucleus: oval, vesicular (with fine chromatin and prominent nucleolus), and eccentric in position

Shape: branching spindle-shaped cells.

Sites: The most common type of C.T. cells, very numerous in the loose C.T.

32
Q

How are fibroblasts seen under EM?

A

οƒœ The cytoplasm is rich in ribosomes, rER, and prominent Golgi.
οƒœ Some mitochondria
οƒœ Microtubules and microfilaments preserve the shape of the cell.

33
Q

What is the function of fibroblasts?

A

1- Synthesis of the components of the C.T. matrix.

2- Synthesis of nearly all types of C.T. fibers (fiber-forming cells).

3- Responsible for the growth of C.T. and healing of wounds.

34
Q

What are fibrocytes?

A

Fibrocytes: are old fibroblasts characterized by:
 Shape: spindle-shaped but flatter and has fewer processes.
 Nucleus: darker.
 Cytoplasm: less basophilic (less rER).
 Function: preserve and renew the already formed components of the CT matrix and fibers.

35
Q

What are the steps of the formation of white adipocytes?

A

UMCs β†’ Lipoblast β†’ Brown adipocyte β†’ White adipocyte.

36
Q

Can both brown and white adipocytes divide?

A

No

37
Q

Are both brow and white adipocytes differentiated?

A

Yes

38
Q

How are the brown adipocytes seen under LM?

A

Cytoplasm: Contains many fat droplets:
Paraffin sections (Hx&E) β†’ Cytoplasm is acidophilic with many vacuoles due to dissolved fat droplets.

Nucleus: single central and rounded nucleus.

Shape: oval

Sites: In sites of Brown adipose CT

Number: The main cells in adipose CT

Size: 10-times smaller than white adipocytes

39
Q

How are the white adipocytes seen under LM?

A

Cytoplasm: Contains a large fat globule:
1. Paraffin sections (Hx&E) β†’ an empty space due to dissolved fat globule.

Nucleus: A single flat peripheral nucleus pushed to one side giving a Signet Ring appearance.

Shape: oval

Sites: Mainly in sites of white adipose CT, Also in loose CT.

Number: The main cells in adipose CT

Size: 10 times larger than brown adipocytes.

40
Q

How are brown adipocytes seen under EM?

A

Multiple fat droplets.
οƒœ sER and numerous mitochondria are scattered among
the fat droplets

41
Q

How are white adipocytes seen under EM?

A

sER & some mitochondria are present in the remaining
cytoplasm beside the nucleus.

42
Q

What is the origin of white reticular cells?

A

UMC

43
Q

Can reticular cells divide?

A

No

44
Q

are reticular cells differentiated?

A

Yes

45
Q

How are reticular cells seen under EM?

A

Few organelles include rER, ribosomes, and mitochondria.

46
Q

How are reticular cells seen under LM?

A

Cytoplasm: Hx & E β†’ Pale basophilic.
Special stain β†’ Silver stain

Nucleus: central,oval, and pale

Site: reticular stroma of parenchymatous organs.

Shape: branched with many processes

Size: small

Number: most common cell in reticular CT.

47
Q

What is the function of reticular cells?

A

It acts as a multipotent stem (mother) cell for:
1. Supportive function: with reticular fibers, they both form a delicate network that supports parenchymal cells.

  1. Antigen Presenting Cells (APCs): present antigens to T-Helper lymphocytes to activate the immune system.
  2. Phagocytic function.
48
Q

What is the origin of macrophages?

A

From migrating blood monocytes (that originally develop from UMCs in bone marrow).

49
Q

Can macrophages divide?

A

No

50
Q

Are macrophages differentiated?

A

Yes

51
Q

How are macrophages seen under LM?

A

Cytoplasm: Hx & E: Pale basophilic and not clear.

οƒœ Special stains:
 Vital stain e.g. trypan blue.
 Supravital stain e.g. neutral red.

Nucleus: Eccentric, small, kidney-shaped oval or irregular, single and pale.

Site: mainly in loose CT

Shape: rounded with pseudopodia

Number: the 2nd most common in loose CT

Size:large

52
Q

How are macrophages seen under EM?

A

Many lysosomes, few rER and free polysomes, small Golgi, and few mitochondria.

οƒœ Pseudopodia, phagosomes, and pinocytotic vesicles.

53
Q

What are the types and functions of macrophages?

A

A) M1 β€œkiller” macrophages:

  1. Phagocytic function: can phagocytize foreign bodies e.g. bacteria.
  2. Many phages may fuse together to form multinucleated foreign body giant cells to attack a large foreign body
  3. Antigen Presenting Cells (APCs): present antigens to T-Helper lymphocytes to activate immunity
  4. Secretory function: they secrete enzymes (e.g. collagenase and elastase) and cytokines.

B) M2 β€œrepair” macrophages: function in constructive processes like wound healing and tissue repair, they secrete growth factors and other cytokines

54
Q

What are the types of skin?

A

❖ Thick (non-hairy) skin: found in palms and soles.
❖ Thin (hairy) skin: covers the rest of the body.

55
Q

What is the function of adipocytes?

A

Same as adipose connective tissue

56
Q

What are free connective tissue cells?

A

οƒœ Mast cells.

οƒœ Plasma cells.

οƒœ Melanophores = Chromatophores = Melanophages.

οƒœ Migrated Blood leucocytes.

οƒœ Wandering (Free) macrophages.

57
Q

What is the origin of mast cells?

A

UMC

58
Q

Can Mast cells divide?

A

No

59
Q

Are mast cells differentiated?

A

Yes, Fully differentiated

60
Q

How are Mast cells Seen under LM?

A
61
Q

How are Mast cells Seen under LM?

A
62
Q

What is the shape of Mast cells under EM?

A

οƒœ The cell border is irregular with short process.

οƒœ The cytoplasm contains: Much membrane-bounded electron dense granules, ribosomes, rER and mitochondria

63
Q

What are the functions of Mast cells?

A

οƒœ Secretion of Heparin: natural anticoagulant.

οƒœ Synthesis, storage and secretion of Histamine: in cases of allergy and inflammation.

οƒœ Secretion of Slow Reacting Substance of Anaphylaxis (SRS-A): has similar action as histamine but longer in duration.

οƒœ Secretion of Eosinophil Chemotactic Factor (ECF): attract eosinophils

64
Q

What is the origin of plasma cells?

A

Activation of B-lymphocytes (originating from UMCs) by specific antigen leads to formation of plasmablasts which mature into plasma cells.

65
Q

Do plasma cells divide and are they differentiated?

A
  • Cannot divide.
  • Fully differentiated.
66
Q

What is the Shape of plasma cells under LM?

A
67
Q

What is the shape of plasma cells under EM?

A

οƒœ Cell border is irregular.

οƒœ The cytoplasm is rich in rER, ribosomes, prominent Golgi and mitochondria.

68
Q

What are the functions of plasma cells?

A

Secretion of antibodies (responsible for humoral immunity).

69
Q

What are melanophores? (Pigment cells)

A

Melanin-containing C.T. macrophage that engulfs melanin made by melanocytes.

70
Q

What is the site of melanophores?

A

Found in the choroid of the eye and dermis of skin.

71
Q

What is the shape and structure of Melanophores?

A

Branched with melanosomes in the cytoplasm.

72
Q

what are migrated leukocytes?

A

Blood leucocytes leave the blood stream and accumulate in the C.T. in certain conditions, e.g.:

(i) Eosinophils: in allergy or parasitic infestation.

(ii) Neutrophils: in acute infections.

(iii) Monocytes & lymphocytes: in chronic infections.

General - Histology πŸ”¬ (8 decks)

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