Flashcards in ToB 3 Glandular tissues, and how cells secrete Deck (93)
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?
What type of gland secretes hormones?
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?
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?
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:
Give an example of a simple coiled tubular gland:
Merocrine sweat glands
What are the 3 methods of secretion from an exocrine gland?
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
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:
Give 3 examples of compound tubuloacinar glands:
1) Salivary glands
2) Glands of respiratory passages
What are the 2 types of secretion 'nature', used for classification?
1) Mucous glands
2) Serous glands
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.
If a cell is secreting via apocrine secretion, what must the cell do to retain its original surface area?
Apocrine secretion is endocytosis, so membrane must be constantly added to the cell membrane to retain original surface area.
A lactating mammary gland secretes via what method?
Apocrine secretion of fat droplets,
Merocrine secretion of protein
What type of gland is a mammary gland?
Compound acinar exocrine gland
What is present around a mammary gland to assist secretion?
Myoepithelial cells contract ('let down')
Why is 'sweat-testing' often used to confirm a diagnosis of cystic fibrosis?
Due to a defective Cl- channel in the apical membrane of the epithelial cells lining sweat gland ducts, there is poor reabsorption of Cl-, leading to abnormally salty sweat.
Is sweat usually hypertonic, isotonic, or hypotonic?
Hypotonic (contains less salt than normal body cells)
Give an example of a holocrine gland:
Sebaceous gland cells (on skin)
What is the function of a sebaceous gland cell?
Via holocrine secretion they fill the hair follicle on skin with sebum.
When the cell 'engulfs' outside molecules into the cell, enveloped in part of the cell membrane.
When vesicles inside the cell fuse with the cell membrane, releasing the contained molecules outside the cell.
Describe the appearance of the Golgi Apparatus:
Stack of flattened sacs called cisternae
Where does the glycosylation of newly synthesised proteins and lipids occur?
In the Golgi Apparatus
What are the 2 methods of exocytosis of proteins from the Golgi Apparatus?
1) Constitutive secretion (continuous)
2) Regulated secretion (requires signal)
What are the 3 possible destinations for the glycosylated products from the Golgi apparatus?
1) Extruded via secretory vesicles
2) Retained in cell
3) Enters plasma membrane
A glycoprotein-polysaccharide covering which surrounds most animal epithelial cells, and some bacteria.
What are the main 4 possible functions of the glycocalyx:
1) Adhesion - to neighbouring cells and substrates
2) Mobility of cells
3) Communication with neighbouring cells
4) Contact inhibition - of division and movement (of neighbouring cells)
What is a key component of the glycocalyx for its specific interactions?
Branched sugar chains
What are the 4 basic control mechanisms of secretion?
1) Nervous stimulation/inhibition
4) Negative feedback chemicals
What control mechanism leads to the release of adrenaline in the body?
Sympathetic nervous stimulation of the adrenal medullary cells
What control mechanism leads to the secretion of cortisol?
Endocrine stimulation: ACTH release stimulates adrenal cortex to release cortisol
What does ACTH stand for?
Define 'neuroendocrine' cell:
A cell which receives neuronal stimulation, and consequently releases hormones
How do thyroid hormones use negative feedback control?
High levels of T3/T4 inhibit further release of TSH (thyroid stimulating hormone)
Name the 3 major salivary glands:
Does the submandibular salivary gland contain mucous or serous cells?
The submandibular gland secretes both mucous and serum (so both)
Where are the submandibular glands, and where does their duct open?
Under the jawbone, with the duct opening at the front of the mouth under the tongue
Where are the sublingual glands?
Under the tongue
Where are the parotid glands?
Inside the cheek, just in front of the ears
Does the parotid salivary gland contain mucous or serous cells?
Serous cells, it doesn't secrete mucous
Why are the serous cells sometimes referred to as 'serous demilunes'?
After fixation serous cells which are in between mucous cells become distorted and form a demilune cap over the mucous cells. This is ARTEFACTUAL.
Does the sublingual cells contain mucous or serous cells?
Both, but predominantly mucous cells.
What type of a gland is the pancreas?
The pancreas is both exocrine and endocrine: compound acinus exocrine cells, but also endocrine cells in pancreatic islets.
What type of secretory cells are present in the pancreatic duct?
Why does cystic fibrosis usually cause pancreatitis?
The secretions of the exocrine pancreas contain too little water, which blocks the ducts, causing inflammation.
Why is fat often present in the faeces of cystic fibrosis sufferers?
Cystic fibrosis causes the blockage of pancreatic ducts (due to thick secretions), which results in insufficient lipase secretion, causing malabsorption of fat.
What is stored in the colloid of a thyroid follicle?
Where is thyroglobulin synthesised?
In the simple cuboidal epithelial cells in the thyroid gland
What must the epithelial cells in the thyroid gland take up from the capillary in order to synthesise thyroid hormones?
Where does iodination of thyroglobulin (to synthesise T3/T4) occur?
In the colloid of thyroid follicles
Are T3 and T4 hormones synthesised via oxidative or reductive coupling reactions?
Oxidative coupling reactions
By what method of secretion do T3 and T4 leave the epithelial cells of the thyroid gland?
What shape is the thyroid gland?
Bow-tie shape (and position)
How many parathyroid glands are there in the body, and where are they situated?
4, 2 in each lobe of the thyroid gland
What are the 2 main types of cells in a parathyroid gland?
1) Principal (chief) cells
2) Oxyphil cells
3) Adipose cells
Which cells in the parathyroid gland secrete PTH?
Principal (chief) cells
How many adrenal glands are there in a body, and where are they situated?
2, one above each kidney
What are the 3 zones within the adrenal cortex?
1) Zona reticularis
2) Zona fasciculata
3) Zona glomerulosa
What way does blood flow through an adrenal gland?
From the cortex towards the medulla
What type of hormones are secreted by the adrenal cortex cells?
Which hormones are secreted by the adrenal medullary cells?
What name is given to the layer surrounding the adrenal cortex?
What type of hormones are secreted by the zona glomerulosa in the adrenal cortex?
Give an example of a mineralocorticoid:
What type of hormone is secreted by the zona fasciculata in the adrenal cortex?
What is the most abundant glucocorticoid hormone?