Cheatography
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More histology of epithelial cells (glands)
This is a draft cheat sheet. It is a work in progress and is not finished yet.
SECRETION Introduction
3 distinct cellular activities: |
- Uptake of extracellular fluid |
- Processing of these within the cells --> Produce a more complex product |
- Active release of these product |
NOTE:
Different from EXCRETION, the passive release of waste products
Introduction (cont.)
2 functional types of glands: |
Exocrine:
- Release secretory products onto epithelial surface via a duct |
Endocrine:
-No ducts connecting to epithelial surface
- Secrete products into blood or lymph (Product is Hormones) |
Ex: salivary, sweat glands |
Ex: pancreas, thyroid gland |
Methods of secretion
Merocrine/Eccrine
tuyến toàn vẹn |
Apocrine
Tuyến bán hủy |
Holocrine
Tuyến toàn hủy |
- Exocytosis of vesicles |
- Vesicles accumulate at apical portion |
- Secretory products accumulate and the cell ruptures |
- Most common form of secretion |
--> mass of cytoplasm and vesicles are pinched off |
--> Death of cell |
- Ex: Sweat glands, salivary glands |
Ex: mammary gland, some sweat glands |
Ex: Sebaceous glands |
Glandular Structure
Unicellular
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Multicellular |
Goblet cells:
Found in: digestive and respiratory tracts
--> Secretes mucin -> Mucous |
Most glands |
Unicellular Exocrine Gland
Goblet cell |
- Amongst columnar walls of epithelium |
- Found in: respiratory/digestive tracts |
-Extended apical portion (theca) contains mucigen droplet |
- Released by melocrine(toàn vẹn) secretion
--> Mucigen + H20 = Mucous |
- Basal nucleus |
Multicellular Exocrine Glands
- Secreted onto epi surface via ducts |
- The deeper cells within CT is secretory |
- Secretion is discharged from secretory cells, into the duct, onto epi surface |
Classification of Multi Exo Glands
Classified by: |
Ducts: |
Secretory End Pieces: |
- Simple: single, unbranched duct (may be uncoiled) |
- Tubular: glandular cells form tubes |
- Simple branched: 2 or more secretory areas dump into a single duct |
- Alveolar: rounded cluster of cells |
- Compound: branched duct system |
- Tubuloalveolar: contain some tubular/alveolar units as well |
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Classification of Multi Exo Glands (cont.)
Nature of Secretory Product
Exocrine can be described based on nature of Secretory products: |
- Mucous glands: thick, sticky, glycoproteins |
- Serous glands: watery, contains enzyme |
- Mixed: contains more than 1 cell type --> secrete both Serous and Mucous |
Control of Exocrine Secretion
- Most glands secrete at low level continuously |
- Rate modulated by: hormones, autonomic innervation, or both |
- In glands with alveoli --> contractile myoepithelial cells contract to squeeze secretion into ducts |
Endocrine
- Lost connection with epi surface |
- Secrete products directly into blood or lymph |
- Well vascularised |
- Secretions are hormones: proteins, steroids |
- Adapted for storing and releasing when required |
- Often form cords or clumps |
Thyroid gland
Endocrine cells are arranged into follicles surrounding a mass of secretory product (since it stores the product extracellularly) (colloid, thyroglobulin) |
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