Glands Flashcards

(57 cards)

1
Q

Gland definition

A

An epithelial cell or an aggregate of epithelial cells that are specialised for the secretion of a substance.

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2
Q

Secretion definition

A

The production and release of materials by a cell or aggregate of cells.

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3
Q

Two types of gland

A

Endocrine (ductless)

Exocrine (ducted)

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4
Q

Endocrine glands

A

Secrete directly into the blood flowing through them, to let the secretions function at distant parts of the body - secretions are hormones.

Eg pituitary gland

All epithelial cells in the gland secrete the hormone.

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5
Q

Exocrine glands

A

Secrete into a location/region of the body through a duct; their secretions are mostly enzymes or lubricants.

Eg salivary gland, mammary glands, sweat glands

Only cells at apex of duct secrete the products.

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6
Q

Endocrine gland - histology

A

Blood vessels close by
Hormone producing epithelial cells
Larger lumen

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7
Q

Exocrine gland - histology

A

Stratified cuboidal cells
Two layers of cells
Lumen of duct

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8
Q

Adenogenesis

A

Gland development in utero
1. Growth signal received
2. Proliferation of cells occurs and extracellular protein degradation enzymes produced
3. Epithelial cells invade space created

=> exocrine gland - central cells die off to produce duct (canalicularisation); link to mother cells remains; significant amount of branching

=> endocrine glands - produce angiogenic factors to stimulate blood vessel growth in and around epithelial cells; link to mother cells broken through apoptosis; virtually no branching

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9
Q

How does branching occur?

A

FGF10 released by immature fibroblasts.

Epithelial cells move towards signal.

Causes:
1 - tubule elongation (growth factor 1 active; growth factor 2 inactive)
2 - tubule branching (growth factor 1 inactive; growth factor 2 active)

Elongation and branching stopped by Shh.

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10
Q

Simple tubular duct structure

A

Duct does not branch

a) simple tubular - intestinal glands
b) simple branched tubular - gastric glands

Cuboidal epithelial cells

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11
Q

Alveolar secretory duct structure

A

Duct does not branch

a) simple alveolar - no examples in adult humans, some in foetus
b) simple branched alveolar - sebaceous glands (only found where there is hair)

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12
Q

Compound tubular duct structure

A

Duct branches

a) compound tubular - duodenal glands of small intestine

Epithelial cells with muscle so as to contract

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13
Q

Compound alveolar secretory duct structure

A

Duct branches

a) compound alveolar - mammary glands
b) compound tubuloalveloar - salivary glands

Epithelial cells with muscle so as to contract

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14
Q

Stages of growth and development of glands

A

Prebud
Initial bud
Pseudoglandular
Canalicular
Terminal bud

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15
Q

Two types of secretion

A

Mucous

Serous

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16
Q

Interlobular duct

A

Located between lobules,

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17
Q

Intercalated duct

A

Between acinus and striated duct.

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18
Q

Myoepithelial cells

A

Cells that have features of both an epithelial cell and a smooth muscle cell - help to eject secretions from the duct.

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19
Q

Merocrine gland

A

Fusion of vesicles with apical membrane - a form of exocytosis

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20
Q

Apocrine gland

A

Partial loss of cytoplasm eg lactating mammary gland.

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21
Q

Holocrine gland

A

Complete loss of cytoplasm eg sebaceous gland in skin.

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22
Q

Cytocrine gland

A

Cells are released as a secretion eg spermatid

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23
Q

Merocrine secretion

A

Secretion from cells via exocytosis - secretory vesicles joining with membrane.

24
Q

Apocrine secretion

A

Pinched off portion of cell is the secretion.

25
Holocrine secretion
Mature cell dies and becomes secretory product.
26
Cytocrine secretion
Lose whole cell but cell doesn’t die.
27
Types of merocrine secretion
Regulated secretion: secretory granules accumulate in cell and are released by exocytosis upon stimulation - needs Ca2+ ions. Constitutive secretion: product not concentrated into granules but packaged into small vesicles and continuously released to cells surface - used mainly to repopulate the plasma membrane with plasma proteins.
28
Example of merocrine secretion
Release of insulin from beta cells in Islet of Langerhans
29
Glycosylation
The covalent attachment of sugars by enzymes to proteins and lipids to form glycoproteins and glycolipids.
30
Roles of glycosylation
To aid protein folding. Prevents protein digestion by intracellular proteases. Prevents lipid digestion by intracellular lipases. Cell recognition (blood groups). Role of cell to extracellular matrix attachment.
31
Glycation
Covalent attachment of sugars to proteins and lipids to form glycoproteins and glycolipids. Same as glycosylation without enzymes.
32
3 ways of control mechanisms
Hormonal Neural Humoral
33
Striated duct - H + E
Simple columnar epithelium Striations in cells Nucleus near lumen
34
Function of striated duct
Contain a number of ion transporters to keep ions balanced to prevent water loss.
35
Parotid gland
Almost totally serous - serous acini - look like acinar in pancreas. Almost totally purple
36
Submandibular gland
Mostly serous, more mucous. Mix of pink and gray.
37
Sublingual gland
Almost totally mucous. Pale acini - like a dappled grey/purple
38
Saliva production - what type of stimulus?
Neuronal stimulus - control is neural only
39
Is the liver endo or exocrine?
The largest exocrine gland.
40
Hepatic blood supply
Hepatic portal vein Hepatic artery
41
Liver lobule
Hexagonal shaped lobule with portal triad at each point.
42
Kupffer cells
Macrophages in the liver; form part of sinusoidal lining Trap and phagocytose at damaged or aged erthryocytes that were missed by spleen. After splenectomy, these cells take over removal of 120 day old (aged) RBC.
43
Blood flow and bile flow in liver
Blood flows from the outside of the lobule inside towards the central canal. Bile flows from inside out, through the bile duct.
44
Sinusoids
Cells that line portal vein. They have large gaps between them.
45
Three types of capillary vessel
Continuous Fenestrated Sinusoid
46
Continuous capillary vessel
(From outside in): Intact basement membrane; endothelial layer (tunica intima) with intercellular clefts. - in brain and most of body
47
Fenestrated capillary vessel
Intact basement membrane; endothelial layer (tunica intima) with fenestrations - pituitary, small intestine, kidneys
48
Sinusoid capillary vessel
Incomplete basement membrane; endothelial layer (tunica intima) with intercellular gaps (whole cell can pass through) - spleen, bone marrow, liver, lymph nodes
49
Portal triad
Vein - biggest Bile duct - stains purple Artery - similar size to bile duct
50
Canaliculi
Narrow spaces between cells in liver lobule.
51
Route of bile
Canaliculi -> interlobular tributaries -> periportal bile ductules -> bile ducts -> left and right hepatic ducts
52
Space of Disse
Space between sinusoid and hepatocytes.
53
Pit cells
Kill tumour cells that enter sinusoids. The most active form of NK (natural killer) cells.
54
Stellate (Ito) cell
Cells found in space of Disse. Cytoplasmic vacuoles containing vit A. In liver cirrhosis, they lose vit A storage abilities and differentiate in myofibroblasts, which synthesis and deposit collagen within perisinusoidal space => liver fibrosis.
55
Hepatocytes (compared to other cells)
Many mito Many peroxisomes Many free ribosomes A lot to RER and SER Many Golgi Glycogen deposits
56
Rate of liver regeneration
Low to mild damage - 7-8 days Mild to medium damage - 30-40 days Medium to severe damage - never
57
Functions of liver
Storage: iron and copper; vit A (Ito cells), D, E, K (hepatocytes); sugars (glucose as glycogen) Anabolism: >60% of body’s proteins (plasma proteins, enzymes, apolipoproteins); a.a synthesis; haemopoiesis in the embryo/foetus Catabolism: drugs; hormones; Hb; poisons/toxins; sugars; removal of old/damaged RBC after splenectomy Other: bile production; filter cell debris from blood; hormones/growth factors (endocrine); modifies hormones for excretion or function