Lecture 2.2: Glands Flashcards
How are glands classified?
Destination of secretion: Exocrine, Endocrine (some are mixed)
Method of secretion: Merocrine/Eccrine, Apocrine, Holocrine
Nature of secretion: Serous, Mucous
Organisation/Structure: Simple, Compound, Uni/Multicellular
Destination of secretion: Exocrine
These glands secrete their products through ducts
Destination of secretion: Endocrine
Ductless
Directly into blood
Method of secretion: Merocrine/Eccrine
Exocrine Glands only
Most glands are merocrine
The secretions of that cell are excreted via exocytosis from secretory cells into an epithelial-walled duct or ducts and then onto a bodily surface or into the lumen.
Producing a secretion that does not contain cellular components and is discharged without major damage to the secreting cell, no part of the gland is lost or damaged
Method of secretion: Apocrine
Exocrine Glands only
Mammary glands, anogenital region and axillae.
They bud their secretions off through the plasma membrane producing extracellular membrane-bound vesicles.
It loses part of its cytoplasm in their secretions.
Method of secretion: Holocrine
Exocrine Glands only
Sebaceous glands of the skin, Meibomian glands of the eyelid
Secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen.
Nature of secretion: Serous
Produce a watery (protein rich) secretion
Stain intensely with H&E
Sweat Glands, Mammary Glands
Nature of secretion: Mucous
Mucous glands secrete a protein called mucin (highly glycosylated polypeptides) , which with water forms the substance known as mucus
Mucus is washed way during H&E staining, so mucous glands stain more poorly, leaving a ‘foamy’ appearance
Along whole digestive tracts
Organisation/Structure: Simple (Ducts)
Unbranched
Single duct
Organisation/Structure: Compound (Ducts)
Branched ducts
Acinar
Pear-like secretory portions with wide base and little inner free space
Tubular
Tube-like secretory portions
Goblet Cells
Unicellular Glands
Contain large Golgi in which new carbohydrates are added to newly-synthesised protein to create mucin
Colonic Crypts
Simple Tubular Glands
Resorption of water and electrolytes
Eccrine Sweat Glands
Simple coiled tubular glands
Secretory portions are surrounded by contractile “myoepithelial cells”
Their contraction transports luminal contents towards the ducts
Simple branched acinar galnds
Simple: Duct
Branched Acinar: Secretory Portion
Complex Glands: Features + Examples (acinar/tubular)
Branching Ducts so compound ductal sections
Glands of Brunner in the Duodenum
Exocrine Pancreas (compound tubular)
Salivary Glands (compound acinar)
Mammary Glands (compound tubuloacinar)
Intercalated Ducts
Join acini with larger collecting ducts
What is an acinus?
An acinus is any cluster of cells that resembles a berry
Exocrine Pancreas
Complex Acinar Gland
The simple squamous epithelium of the intercalated ducts penetrates the pancreatic exocrine acini
The Pancreas Gland Type
Mixed
Exocrine/Endocrine Gland
Cystic Fibrosis and Sweat Ducts
In CF, the absence of the CFTR in the apical membranes of the epithelial cells of the sweat duct results in poor reabsorption of Cl-
This suppresses Na+ reabsorption
Cystic fibrosis and sweat testing for abnormally can confirm a diagnosis of CF
Why was Cystic Fibrosis previously known as ‘Fibrocystic Disease of the Pancreas’?
In CF, exocrine secretions contain too little water
They become thickened, and block ducts
The exocrine pancreas becomes painfully inflamed (pancreatitis) and fibrotic
The gut receives insufficient pancreatic digestive enzymes, and malabsorption results
When do symptoms of insufficient secretion of pancreatic digestive enzymes appear in CF?
Usually in the first year of life in 90% of cases