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Histology > Epithelium > Flashcards

Epithelium Flashcards

1
Q

What are three characteristics of epithelial cells?

A
  1. It has polarity (basal, apical and lateral sides)
  2. Closely connected to neighboring cells by desmosomes and tight junctions
  3. Basement membrane
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2
Q

What is the function of the basement membrane?

A

It helps anchor the epithelial cells to the underling connective tissues.

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3
Q

What is the basement membrane composed of?

A

Basal lamina

Reticular lamina

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4
Q

What is basal lamina?

A

This is the part of the basement membrane that is closest to the epithelial cells

It is an adhesive sheet secreted by the epithelial cell and anchors them

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5
Q

What is the reticular lamina?

A

This is a component of the basement membrane made up of a network of collagen fibers secreted by the fibroblast connective tissue

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6
Q

Is the Epithelia vascularized?

A

The epithelia is avascular because the capillaries do not penetrate the basement membrane

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7
Q

How does the epithelium get its oxygen and nutrients?

A

The loose connective tissues under the basement membranes contain capillaries and they provide nutrients and gas exchange.

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8
Q

List the functions of the Basement membrane

DAR

A

Anchor epithelial tissue to the underlying connective tissue

Resists stretching and tearing

Defines epithelial boundary

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9
Q

Is epithelial tissue innervated?

A

Although the basement membrane and epithelial tissue is avascular it is innervated by nerve fibers

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10
Q

What causes regeneration in epithelial cells?

A

Loss of apical-basal polarity and broken lateral contacts

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11
Q

What special structures are on the lateral sides of epithelial cells?

A

Tight junctions

Desmosomes

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12
Q

What is the function of tight junctions?

A
  1. Present mostly and closest to the apical side of the cell.
  2. Block the movement of substances in between adjacent cells from the environment
  3. Maintains polarity of the cell membrane
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13
Q

What is the function of desmosomes?

A

Typically deep to adhering junctions closest to the basal side

Abundant in stratified epithelia exposed to stress

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14
Q

What type of cell adhesive are tight junctions?

A

Occluding junctions at the apical end

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15
Q

Classifications of Epithelial cells

A
  1. Simple squamous epithelium
  2. Simple cuboidal epithelium
  3. Simple columnar epithelium
  4. Pseudostratified ciliated columnar epithelium
  5. Stratified squamous epithelium
  6. Transitional (urinary) epithelium
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16
Q

Describe squamous

A

Wider than tall

Flattened

nucleus is ovular

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17
Q

Describe cuboidal

A

Roughly similar in thickness and width

Nucelus centered

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18
Q

Describe columnar

A

Height is far greater than the width

Nucleus closer to basal end

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19
Q

What does it mean for epithelium to be simple?

A

There is a single layer of cells

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20
Q

What does it mean for the epithelium to be stratified?

A

It has 2 or more layers

named after the shape of the top layer

Squamous

cuboidal

columnar

kerantized

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21
Q

Characteristics of squamous epithelium

A
  • Made of one layer of scale-like flattened cells
  • Flat nuclei
  • Very small amount of cytoplasm
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22
Q

What type of epithelial cell is mesothelium?

A

Simple squamous epithelia

These cells secrete lubricating fluid to reduce friction in serous membranes

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23
Q

What is the main functions of simple squamous epithelium?

PEAM

A

Mesothelium lines organs and body cavities like the pericardial, pleural, and peritoneal spaces

Endothelium lines the vascular and lymphatic spaces

Lining lung alveoli for gas exchange (pneumocytes)

Parietal layer of Bowmen’s capsule to facilitate diffusion and filtration

24
Q

Describe simple cuboidal epithelium

A
  1. Made of one layer of cells
  2. Height of each cell is equal to the width
  3. Nuclei are rounded and centrally located
25
Q

Main functions of simple cuboidal epithelia

A

Involved in secretion and absorption

ie. kidney tubules

26
Q

Location of simple cuboidal epithelia

KONG

A

Kidney tubules

Nephron

Ducts and secretory portions of small glands (sweat)

Ovary surface

27
Q

Describe simple columnar epithelia

A
  1. One layer of cells
  2. height of cells exceeds the width
  3. nuclei are oval and located in the lower half of cells
  4. Nonciliated (microvilli) (GIT) or partly ciliated (Uterine tubes)
  5. Some layers may have mucus-secreting goblet cells
28
Q

Function of simple columnar epithelium

A

Absorption and secretion of mucus, enzymes, and other substances

Absorption (brush border) ie. small intestine, gallbladder

Secretory functions (maybe non-ciliated or microvilli)

29
Q

What is the location of simple columnar epithelium

AUGG!!

A

GIT (stomach to anus) ciliated or non-ciliated

Glands (base of the duct)

Airways (Bronchi → move mucus)

Uterus/ Uterine tube

30
Q

Describe pseudostratified columnar epithelium

A
  1. Cells vary in height
  2. Appear to be multilayered and stratified, but all cells are attached to the BM
  3. Many cells are ciliated
  4. Nuclei are in irregular layers giving false impression of being stratified
  5. Ciliated or non-ciliated
31
Q

What are the three types of cell connections?

A

Occluding (tight)

Adhering (anchoring)

Communicating (gap)

32
Q

What are occluding junctions?

A

These are cell connections that tightly seal the intercellular space between epithelial cells on the apical side

33
Q

What is an adhering (anchoring) junctions?

A

Desmosomes connect cell to cell

Hemidesmosomes connects cell to basement membrane

34
Q

What are gap junctions?

A

These are pores or channels in the membranes of neighboring cells that help in communicating between cells

35
Q

What are the two types of glands formed by the unfolding of epithelium?

A

Endocrine: no contact with the exterior, no ducts, produces hormones

Exocrine: has a duct that allows for substances to be directly secreted onto the exterior.

36
Q

Merocrine secretion

A

Secretions such as membrane-bound granules are stored in vesicles that when stimulated will be transported to the apical surface fuse with the cell membrane and released via exocytosis into the lumenal space

37
Q

Apocrine secretions

A

The secretion is released with some cytoplasm surrounded by a plasma membrane.

Instead of the membrane-bound secretion fusing with the plasma membrane some plasma membrane released with it into the lumenal space.

38
Q

Holocrine secretion

A

The secretions are accumulated within the cell but instead of simply using exocytosis the secretions are released when the cell dies via apoptosis and releases its contents in the lumenal space.

The whole-cell is shed in the secretion

Sebaceous gland

39
Q

What are the classifications of exocrine glands?

A

Unicellular

Multicellular

40
Q

What are unicellular glands?

A

These are single mucus-producing cells shaped like a wine glass seated in an epithelial surface all by its own.

Pseudostratified columnar epithelia

Columnar epithelia

Simple cuboidal

41
Q

What are multicellular exocrine glands?

A

They have specialized duct and secretory cells and form a sheet of cells that is invaginated

42
Q

What are the classifications of multicellular exocrine glands?

A

Simple

Compound

Tubular

Acinar (alveolar)

43
Q

What does it mean if a multicellular gland is simple?

A

If the duct is unbranched, but the secretory portion can be branched

44
Q

What does it mean if the multicellular exocrine gland is compound?

A

It means that the duct part of the gland is branched

45
Q

What does it mean if an exocrine gland is tubular?

A

The secretory portion of the gland is about the same size as the duct

46
Q

What does it mean if an exocrine gland is acinar or alveolar?

A

The secretory part of the gland is larger than the duct

47
Q

Can an exocrine gland be both tubular and acinar?

A

Yes if the secretory part of the gland is the same size as the duct but the branches at the end are bigger than the duct

48
Q

What are myoepithelial cells?

A

Contractile epithelial cells that surround the secretory side of the gland to contract to push the secretion into the duct

Mammary, sweat, and saliva glands

49
Q

What is the function of Pseudostratified Columnar epithelial cells?

A

Presence in the upper respiratory system when ciliated allows it to aid in the movement of mucus up and out of the airway.

50
Q

What are cilia?

A

Located on the apical surface of the anchored cell and moved the liquids produced by goblet cells for instance over the cell surface.

51
Q

What are microvilli?

A

Located on the apical surface of anchored cells to increase the surface area for absorption

Also called the brush border

52
Q

Stratified squamous epithelium

A
  1. Surface cells can either be keratinized or non-keratinized
  2. If non-keratinized (wet, flattened, and nucleated surface)
  3. If keratinized (dry and dead)
  4. Middle layer → polyhedral cells held together by desmosomes
  5. Basal layer → columnar cells, mitotically active and migrates upwards to replace destroyed cells
53
Q

Where are stratified squamous non-keratinized cells?

A

These surfaces are wet and protective

  1. Mouth cavity, pharynx, esophagus
  2. Vagina and vaginal surface of cervix
  3. Anal canal
  4. Cornea
54
Q

Stratified squamous keratinized

A

Basal and middle layers are non keratinized

Uppermost layer has dead, enucleated, cells with keratin filled cytoplasms solidly packed together as a surface keratin layer for safety

55
Q

Stratified columnar

A

Lines the ducts of sweat glands

Has 2 layers of cuboidal cells

56
Q

Transitional epithelium

A
  1. This tissue is able to change its shape and the number of layers as the bladder fills and empties
  2. The surface tissue is rounded with large cuboidal cells bulging into the lumen.
  3. Relaxed → 5-8 layers, round cuboidal tissue surface
  4. Distended → 2-3 layers, “squamous” tissue surface

Histology (9 decks)

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