ToB 3 Glandular tissues, and how cells secrete Flashcards
Define gland:
An epithelial cell(s) specialised for secretion
What are the 4 properties of a gland, which allow classification?
1) Destination of secretion (or route it may take)
2) Structure of the gland
3) Nature of the secretion
4) Method of secretion
Define an exocrine gland:
A gland with duct(s), which secrete onto an epithelial surface.
Define an endocrine gland:
‘Ductless’ glands, which secrete into the bloodstream
What is secreted by an endocrine gland?
Hormones
What type of gland secretes hormones?
Endocrine glands
What is meant by a ‘simple gland’?
A gland which has a single duct, or ducts which do not branch
What is meant by a ‘compound gland’?
A gland which has branched ducts
How would you classify a gland with branched ducts?
Compound gland
Describe a goblet cell in glandular terms:
Unicellular exocrine gland which secretes mucous
Why is it important that mucous is rich in NaCl?
This allows the mucous to stay moist, as it creates a water potential gradient across the apical epithelial cell membrane, so water is likely to leave the cell (into the lumen).
Why do cystic fibrosis sufferers have viscous mucous?
They have a defective CFTR gene, resulting in a defective Cl- channel, so Cl- cannot leave the apical epithelial membrane, preventing the setup of a water potential gradient, so water doesn’t leave the cell (into the lumen).
What type of cell produces mucous?
Goblet cell
What does CFTR stand for?
cystic fibrosis transmembrane regulator
What is ‘meconium ileus’?
Bowel obstruction preventing infants passing their first faeces, due to viscous mucous.
What is the most common explanation for meconium ileus?
Cystic fibrosis (defective CFTR gene)
What does an acinus duct look like?
Grape on a stalk
What type of cells make up the acinus?
Acinar cells and ductule cells
Give an example of a simple tubular gland:
Intestinal glands
Give an example of a simple coiled tubular gland:
Merocrine sweat glands
What are the 3 methods of secretion from an exocrine gland?
1) Merocrine
2) Apocrine
3) Holocrine
What is meant by a ‘merocrine’ gland?
It is an exocrine gland, which secretes via exocytosis.
What is meant by an ‘apocrine’ gland?
A portion of the cell membrane buds off the apical side, containing the secretion.
What is meant by a ‘holocrine’ gland?
A glandular cell which disintegrates to release secretion
Give an example of a simple acinar gland:
These are not found in an adult, but are a development stage of simple branched acinar gland.
Give an example of a holocrine simple branched acinar gland:
Sebaceous gland of the skin/nose
How would you classify a gland in which the ducts are branched?
Compound exocrine gland
Give 3 examples of compound tubular glands:
1) Mucous glands in mouth
2) Bulbourethral glands
3) Testes
What do the bulbourethral glands secrete, and where?
A viscous, clear, salty liquid (pre-ejaculate), which neutralises residual acid in the urethra.
Give an example of a compound acinar gland:
Mammary glands
Give 3 examples of compound tubuloacinar glands:
1) Salivary glands
2) Glands of respiratory passages
3) Pancreas
What are the 2 types of secretion ‘nature’, used for classification?
1) Mucous glands
2) Serous glands
Describe ‘mucins’:
Highly glycosylated polypeptides, present in mucous. They swell in the presence of water.
How do mucous glands appear when stained with H&E?
Mucous glands stain poorly in H&E stain, so appear pale
Describe serous gland secretion:
Watery and free of mucous, often containing enzymes.
How do serous glands appear when stained with H&E?
They are eosinophilic, so appear pink.
If a cell is secreting via merocrine secretion, what must the cell do to retain its original surface area?
Because merocrine secretion is exocytosis, in which the secretion is encased in membrane which fuses with the cell membrane. This must be retrieved, to stabilise the cell surface area.