Glands Flashcards

1
Q

Define gland

A

an epithelial cell or collection of cells specialised for secretion`

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2
Q

How can glands be classified?

A

Destination of secretion
Structure of the gland
Nature of the secretion
Method of discharge.

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3
Q

Define exocrine

A

A gland with ducts

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4
Q

Define endocrine

A

A ‘ductless gland’ that secretes directly into the blood

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5
Q

How can you classify glands by structure?

A

unicellular/multicellular

coiled/branched

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6
Q

Define mucous glands

A

Secretions contain mucus, rich in mucins (highly glycosylated polypeptides). Such cells stain poorly in H&E sections.

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7
Q

Define serous glands

A

Secretions (often enzymes) are watery and free of mucus. Eosinophilic (pink) in H&E sections.

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8
Q

What are the modes of secretion?

A
  • Merocrine
  • Apocrine
  • Holocrine
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9
Q

How does Merocine secretion work? (exocytosis)

A
  • Membrane bound vesicle approaches cell surface
  • Vesicle fuses with plasma membrane
  • Contents of vesicle are in continuity with the extracellular space
  • Plasma membrane is very slightly larger
  • Membrane retrieved, stabilising cell surface area
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10
Q

How does Apocrine secretion work?

A
  • Non-membrane bound structure (e.g. a lipid) approaches cell surface
  • Makes contact and pushes up apical membrane
  • Thin layer of apical cytoplasm drapes around droplet
  • Membrane surrounding droplet pinches off from cell
  • Plasma membrane is very slightly smaller
  • Membrane added to regain original surface area
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11
Q

How does Holocrine secretion work?

A
  • Disintegration of the entire cell
  • Release of contents
  • Discharge of the whole cell
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12
Q

Define endocytosis

A

Endocytosis is the process of engulfing material initially outside the cell. It is the opposite of exocytosis (merocrine secretion). Endo/Exocytosis are coupled in transepithelial transport.

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13
Q

Define transepithelial transport

A
  • Material is endocytosed at one surface of the cell
  • The transport vesicle shuttles it across the cytoplasm
  • The material/vesicle is then exocytosed at the opposite surface.
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14
Q

What is the structure of the golgi apparatus?

A
  • Stack of disc-shaped cisternae
  • One side of the discs are flattened, other side is concave
  • Discs have swelling at their edges (Vesicles that bud off)
  • Distal swellings pinch off as migratory Golgi Vacuoles
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15
Q

What is the function of the golgi apparatus?

A
  • Sorting into different compartments
  • Packaging through condensation of contents
  • Adding sugars to proteins and lipids (Glycosylation)
  • Transport
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16
Q

What are the possible destinations of products of the golgi apparatus

A
  • Majority extruded in secretory vesicles
  • Some retained for use in the cells (eg lysosomes)
  • Some enter the plasma membrane (Glycocalyx)
17
Q

What mechanisms can control secretion?

A

Nervous
Endocrine
Neuro-endocrine
Negative feedback