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Wk 3 Flashcards

Tissues Epithelia: Structure & Function

1
Q

What is epithelia?

A

A sheet of cells that covers a body surface or cavity (dense - lack of extracellular matrix).

Structure:
- Apical (top which faces a lumen)
- Basal (bottom which is bound to basement membrane)
- Lateral (cell to cell junctions form boundaries)

Function:
- Selective barrier
- Secretory surface
- Protective surface

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2
Q

What are the two types of epithelial tissue?

A

Covering epithelia tissues - line and cover structures.

Glandular epithelia tissue - secretes stuff.

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3
Q

What are the types of covering epithelia?

A
  • Mucous membrane
  • Serous membrane
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4
Q

What is a mucous membrane?

A

Lines a body cavity that opens directly to the exterior.

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5
Q

What are the 3 layers that mucosa consists of?

A
  1. Epithelium
  2. Lamina propria
  3. Muscularis mucosae
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6
Q

What is a serous membrane?

A

Lines a body cavity that does NOT open directly to the exterior.
- Covered by mesothelium that secrete fluid (reduces friction)

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7
Q

What are the two types of glandular epithelial tissue?

A
  • Exocrine glands
  • Endocrine glands
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8
Q

Can glands be unicellular OR multicellular?

A

Yes

Unicellular:
Exocrine - Goblet/Paneth cells
Endocrine - Enteroendocrine

Multicellular:
Brunners glands

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9
Q

What are exocrine glands?

A

Will empty their contents into a duct which opens into the lumen of the organ (simple or stratified cuboidal).

Function: digestive enzymes aid digestion, reduce body temperature by sweating.

E.g.
- Pancreas
- Sweat glands
- Digestive glands

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10
Q

What are the types of ducts of exocrine glands?

A

Unbranched - simple
Branched - compound

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11
Q

What are the modes of secretion of exocrine glands? (multicellular)

A
  • Merocrine glands
  • Apocrine glands
  • Holocrine glands
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12
Q

What are merocrine glands?

A
  • Synthesised by ribosomes on ER
  • Packaged and processed by golgi complex
  • Released from cell by exocytosis

E.g. salivary glands

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13
Q

What are apocrine glands?

A
  • Top of cell (apical) is pinched off by exocytosis
  • Cell then repairs itself

E.g. mammary glands

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14
Q

What are holocrine glands?

A
  • Whole cell ruptures to form secretory product

E.g. sebaceous gland

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15
Q

What are endocrine glands?

A

Release hormones into the bloodstream (simple cuboidal and others).

Function: hormones help maintain homeostasis.

E.g.
- Pituitary (stores hormones)
- Pancreas
- Adrenal glands

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16
Q

What are the epithelia cell shapes?

A
  • Squamous cells (flat and thin)
  • Columnar cells (rectangular)
  • Cuboidal cells (square shaped)
  • Transitional cells (change shape)
17
Q

What are the epithelia cell layers?

A
  • Simple epithelium (single layer)
  • Stratified epithelium (2 or more layers)
  • Pseudostratified epithelium (appears to be multiple but only 1 layer)
18
Q

What is simple squamous epithelia?

A

Structure:
- Single layer of cells
- Nuclei lay flat

Function:
- Filtration, diffusion

E.g.
- Epithelium of blood vessels
- Lung alveoli (1 cell thick so gases can diffuse easily)

19
Q

What is simple cuboidal epithelia?

A

Structure:
- Cells with square shape
- Nuclei are round and central

Function:
- Secretion
- Absorption

E.g.
- Capsule of lens
- Collecting tubules of kidney

20
Q

What is simple columnar epithelia?

A

Structure:
- Cells are rectangular shape
- Nuclei are oval shaped, generally at same level

Function:
- Secretion
- Absorption

E.g.
- Lining the gastrointestinal system (GIT)

21
Q

What is stratified squamous?

A

Structure:
- Two or more layers
- Nuclei are flat, often bulges
- Can be keratinised/non-keratinised

Function:
- Provides protection (forms physical barrier)

E.g.
- Skin
- Vagina
- Oral cavity

22
Q

What is transitional (urothelium) epithelia?

A

Structure:
- Round/pear shaped cells

Function:
- Changes shape, located in organs that stretch
- Relaxed (several layers thick)
- Stretched (only 2-3 layers thick)

E.g.
- Ureters and urinary bladder

23
Q

What is stratified cuboidal epithelia? (rare)

A

Structure:
- Two or more layers of square shaped cells
- Nuclei are round/central

Function:
- Protection (limited secretion and absorption)

E.g.
- Ducts of sweat glands

24
Q

What is stratified columnar epithelia? (rare)

A

Structure:
- Two or more layers of rectangular shaped cells
- Nuclei are oval shaped

Function:
- Protection
- Secretion

E.g.
- Parts of conjunctiva of eye
- Ducts of salivary gland

25
Q

What is ciliated simple columnar?

A

Cilia - moves fluid across cell

Structure:
- Single layer of ciliated rectangular cells
- Nuclei are oval shaped, generally at same level

Function:
- Generates movement and mucous

E.g.
- Uterine tubes
- ventricles of the brain

26
Q

What is pseudostratified columnar?

A

Structure:
- Appears multi-layered but is actually a single layer
- Nuclei appear at different levels

Function:
- Generates movement and mucous

E.g.
- Trachea
- Bronchi

27
Q

What are cell junctions?

A

Where two cells meet.

Cell-cell junction:
- Tight junctions
- Adherens junctions
- Desmosomes
- Gap junctions

Cell-matrix junction:
- Hemidesmosomes

28
Q

What are tight junctions?

A

Function: held together firmly like zip ties to prevent substance moving in between cell.

Found:
- Stomach
- Bladder
- Intestines

29
Q

What are adherens junctions?

A

Function:
- Transmembrane glycoprotein (cadherins) join cells together
- Each cadherin inserts plaque (dense layer of proteins) from opposite side of plasma membrane connecting to cadherin of adjacent cell
- Resist separation during contractile (shrinking) activities

Found:
- Intestines

30
Q

What are desmosomes?

A

Function:
- Transmembrane glycoprotein (cadherins) join cells together
- Each cadherin inserts plaque (dense layer of proteins) from opposite side of plasma membrane connecting to cadherin of adjacent cell
- Resist separation under tension

Found:
- Epidermis
- Cardiac cells in heart

31
Q

What are hemidesmosomes?

A

Function:
- Don’t join cells together
- Transmembrane glycoproteins (integrins) hold down cell to basement membrane

Found:
- Epidermis
- Cardiac cells in heart

32
Q

What are gap junctions?

A

Function: tiny-fluid filled tunnels (connexins) connect neighbouring cells, allowing quick communication between cells.

Found:
- Muscle in heart
- Gastrointestinal tract
- Uterus

CTL (10 decks)

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