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General - Histology 🔬 > L4: Epithelium > Flashcards

L4: Epithelium Flashcards

1
Q

what are the main types of tissues in our bodies?

A

-epithelial
-connective
-muscular
-nervous

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2
Q

what are the characteristics of epithelial tissue?

A

1- The cells are close to each other with minimal intercellular substance.

2- The cells rest on a basement membrane.

3- The cells are supported by underlying connective tissue.

4-High rate of degeneration and regeneration (can divide and form new cells).

5- Nerves can enter between the epithelial cells.

6- No blood vessels enter between the cells.

7-from 3 embryonic origins (mesodermal-ectodermal-endodermal).

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3
Q

how are epithelial tissues classified functionally?

A

-covering:- covers the body and lines the cavities.
-glandular:- secretion
-neuro:- perception of stimuli

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4
Q

what are the types of covering epithelium?

A

-simple
-stratified

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5
Q

what are the types of simple epithelium?

A

-squamous
-cuboidal
-columnar
-pseudostratified

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6
Q

squamous simple epithelium

A

-1 layer

-flat cells

-flat and bulging nuclei

-in the lung alveoli, the lining of the heart, lining of blood vessels(endothelium), and external layer of the bowman’s capsule.

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7
Q

cuboidal simple epithelium

A
  • 1 layer

-cuboidal cells

-central and rounded cells

-medium ducts of glands and kidney tubules.

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8
Q

columnar simple epithelium

A

-1 layer

-tall, elongated cells

-the nucleus is basal and oval

-non-modified in large ducts of glands

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9
Q

what are the sites of modified columnar epithelium?

A

-stomach—-contain vacuolated cytoplasm

-intestine—-where the cells have microvilli on their free side (brush border) for increasing the surface area and consequently absorption and it is associated with goblet cells for secretion of mucous

-uterus and fallopian tube (with cilia).

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10
Q

what is the shape of cells in pseudostratified epithelium?

A

tall and short

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11
Q

what is the shape of the nuclei in pseudostratified cells of epithelium?

A

they are arranged at different levels.

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12
Q

what is the site of pseudostratified epithelium?

A

ciliated with goblet cells: upper respiratory passages (nose-trachea-bronchi)

non-celiated: large ducts of glands

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13
Q

why are pseudostratified epithelium called by this name

A

-because cells are arranged at different levels even though they rest on the same basement membrane.

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14
Q

why are the nuclei arranged at different levels even though they rest in the same basement membrane?

A

-Due to the crowding during development.

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15
Q

How are stratified epithelium classified?

A

according to the shape of top layer cells

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16
Q

what are the types of stratified epithelium?

A

-Transitional
-columnar
-squamous

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17
Q

what is the structure of squamous stratified epithelium?

A

-has a thick wavy basement membrane.

-base layer is composed of columnar cells with basal, oval nuclei and is responsible for the regeneration of cells.

-middle layer is composed of polyhedral cells with central, rounded nuclei and is responsible for junctions between cells.

-top layer is from flat cells and flat nuclei

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18
Q

what is the number of layers in squamous stratified cells?

A

30

19
Q

what are the types and sites of squamous stratified epithelium?

A

keratinized: is dry found in the epithelial layer of skin with horny covering scales

non-keratinized: wet and found in the mouth cavity, esophagus, anal canal, vagina, and terminal urethra.

20
Q

what is the structure of transitional stratified epithelium?

A

-thin ill-defined basement membrane.

-base layer is composed of low columnar cells with basal, oval nuclei

-middle layer is composed of polyhedral cells with central, rounded nuclei and is separated by mucous-like substance that helps in the gliding of cells

-superficial layer consists of the top layer and the underlying layers.

top:composed of cuboidal layer which is dome-like and binucleated which is responsible for protecting underlying layers from the bad effect of urine.

underlying layers are flask-shaped

21
Q

how many layers are there in transitional squamous epithelium?

A

6-8 layers

22
Q

what are the sites of transitional stratified epithelium?

A

-ureter
-urinary bladder
-prostatic urethra
-pelvis of the kidney

23
Q

what are the forms of transitional stratified epithelium and what does it depend on?

A

-it depends on the degree of distention of viscus

-in the case of full bladder it consists of two layers the upper is flat and the underlying is cuboidal

-in the case of an empty bladder it returns back to normal.

24
Q

What is glandular epithelium?

A

It is a modified type of epithelium specialized for secretion.

25
Q

How are glands classified?

A

-presence of ducts or not
-no. Of cells
-Branching and shape of ducts and secretory parts.
-mode of secretion
-Type of secretion

26
Q

What are glands classified into according to the presence or absence of ducts?

A

Exocrine: salivary glands

Endocrine: suprarenal-pituitary-thyroid

Mixed: liver and pancreas

27
Q

What are glands classified into according to no. of cells?

A

Mono like goblet cells and multi-like liver and salivary glands.

28
Q

What are glands classified Into according to branching and shape of ducts and secretory parts?

A

Simple: no branching

Simple branched: branching in secretory part

Compound branched:Branching in both

29
Q

What are types of simple glands?

A

Simple tubular: Have tubular secretory part

Simple alveolar: Have an alveolar (flask-shaped) secretory part.

Simple tubualveolar: Have both tubular and alveolar secretory part

30
Q

What are the types of simple branched glands?

A

1- simple branched tubular

2- simple branched alveolar

3- simple branched tubualveolar

31
Q

What are the types of compound branched glands?

A

1- compound branched tubular

2- compound branched alveolar

3- compound branched tubualveolar

32
Q

What is the classification of glands according to the mode of secretion?

A

Merocrine glands:
- The cells of the glands are intact at the time of secretion
E.g. Salivary glands

Holocrine glands:
- The cells are shed at the time of secretion and then replaced by new cells
E.g. Sebaceous glands

Apocrine glands:

  • The apical portions of the cells are pinched off at the time of secretion
    E.g. Mammary glands
33
Q

What is the Classification of glands according to Nature of secretion?

A
34
Q

What is the structure of neuroepithelium?

A

1- sensory cells:
apical part: hairlets (microvilli)
basal part: surrounded by nerve fibrils

2- supporting cells

3- basal cells (can give the other two types)

35
Q

What are the sites of neuroepithelium?

A
  • Taste buds (tongue)
  • Organ of corti (inner ear)
  • Olfactory epithelium (nose)
36
Q

What is the definition of intracellular junctions?

A

The lateral membranes of the epithelial cells show several specialized structures called intercellular junctions that contribute to adhesion and communication between the cells

37
Q

What are the types of intracellular junctions?

A

Types

1- Tight junction
2- Adherens junction
3- Gap junction

38
Q

What is the structure of occludens (tight) junctions?

A

The 2 adjacent cell membranes fuse completely at certain points (ICS=0) to form a seal between I.C & luminal fluids

39
Q

What are the sites & types of occludens (tight) junctions?

A
  • Epithelial cells of the intestine
  • Proximal convoluted tubules of the kidney
  • Capillary endothelial cells
40
Q

What is the function of occludens (tight) Junctions?

A

Forming a complete seal that prevent passage of materials (water & other fluids) from the lumen to the I.C.S

41
Q

What is the structure of adherens junctions?

A

The 2 adjacent cell membranes are separated by wide I.C.S filled with binding (adhesive) material

42
Q

What are the sites of adherens junctions?

A

Firm adhesion between the cells that fix them strongly and preventing their separation

43
Q

What is the structure of gap junctions?

A

The 2 adjacent cell membranes are separated by 2nm gap to allow cell communication

44
Q

What are the sites & functions of gap junctions?

A

1- In the heart, rapid transmission of nerve impulse between the cells so heart contract as one unit (coordinated heart beat)

2- In smooth muscle: transmission of wave of contraction to act in coordination

3- Between the bone cells for rapid exchange of small molecules

General - Histology 🔬 (8 decks)

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