Glandular tissues Flashcards
Define a gland
An epithelial cell of collection of cells specialized for secretion.
How can glands be classified?
by; Destination of secretion Structure of the gland nature of the secretion method of discharge
Destination definitions.
Exocrine- glands with ducts
Endocrine- ductless glands, which secrete into the bloodstream
Classification by structure of the secretory part of the cell.
includes: unicellular/muticellular, acinar/tubular and coiled/branched
Classification by structure of the duct system.
Simple gland- single duct
compound gland- branched ducts
An example of a unicellular gland
Goblet cell- secretes mucous
Describe the pathology of CF
The CFTR is not present in the apical membranes of the epithelial cells. As a result the chloride ion transport across the membrane is compromised. Water does not leave the epithelium in sufficient quantities to adequately hydrate the secreted mucus.
Mucous becomes viscous
Describe the affect of CF on the GI tract
Mucous also becomes viscous, this can result in constipation and invagination of the GI tract. In newborn it can lead to meconium ileus- an inability to pass first feaces.
Classification by secretion.
Mucous glands- contain mucus, rish in mucins (highly glycosylated polypeptides) stain poorly with H&E
Serous glands-secretions (often enzymes) are watery and free of mucus. Eosinophillic in H&E sections
Examples of glands that use merocrine sectretion
Salivary glands, pancreas, apocrine sweat glans (occur in axillar, areolae of nipples and genital and perineal regions)
What is merocrine secretion?
Exocytosis Vesicles fuse with PM contents of vesicle are in continuity with extracellular space PM is very slightly larger Membrane retrieved, stabilizing cell SA
What is apocrine secretion?
non-membrane bound structure approaches the cell surface, pushing out apical membrane coating itself in a thin layer of apical cytoplasm, membrane surrounding droplet pinches off from the cell.
PM transiently smaller
Membrane added to regain original area
Examples of apocrine secretion
mammary gland (myoepithelial cells assist secretion)
What is Holocrine secretion
Disintergrate entire cell
Release of contents
discharge of whole cell
Examples of Holocrine secretion
Sebaceous gland
CF affects on sweat glands
The lack of CFTR in the epithelial cells lining the swear gland results in poor reabsorption of cholride ions. As a result the sweat is rich in chloride and sodium ion.
Describe endocytosis
Endocytosis is the process of englufing material initially outside the cell.
Opposite of exocytosis, exocytosis and endocytosis are coupled in transepithelial transport.
What is meant by transepithelial transport?
Material is endocytosed at one surface, a transport vesicle shuttles across the cytoplasm and material is exocytosed at the oppostie surface.
Describe the structure of the Golgi Apparatus
Stack of disc shaped cisternae
One side of the discs are flattened the other concave
discs have swelling at the edges (vesicles that bud off)
Distal swellings pinch off as migratory golgi vacuoles
Describe the function of the golgi apparatus
sorting into different compartments
Pacaging through condensation of contents
Adding sugars to proteins and lipids- GLYCOSYLATION
Transport
Describe the affect of glycosylation and specificity
branching sugars offer complex shapes for specific interactions in the glycocalyx
Destruction of this layer by enzymes can alter many specificity based properties of the cells;
-adhesion to substrates and neighboring cells
-mobility of cells
-communication with neighboring cells
-contact inhibition of movement and division
What types of mechanisms exist to control secretion?
Nervous control (adrenaline release) Endocrine control (ACTH stimulating Coristol) Neuro-endocrine (nervous control of the hypothalmux on ACTH secretion from the anterior pituitary gland) Negative feedback chemical mechanism (T3 and T4 on TSH)
What are the three salivary glands?
Parotid, submandibular, sublingual
What is the nature of secretion from the parotid gland?
Serous (Exocrine gland)
What is the nature of the secretion from the submandibular gland?
mucus cells predominate (tubular) crescemt shaped serous demilunes (get artefactual distortion
What type of gland is the pancreas?
Exocrine and endocrine (islet of langerhans)
What affects does CF have on the pancreas?
The exocrine pancreas secretions contain too little water and become thickened, resulting in blocking. It becomes inflamed and fibrotic. The gut receives insufficient pancreatic digestive enzyme leading to malabsorption (especially deficient in lipase as its not released elsewhere- faecal excretion of undigested fats usually as diarrhoea)
Throglobulin synthesis and secretion
Uptake of idodied from blood, oxidation to iodine and release into colloid.
Iodination of thyroglobulin
Formation of T3 & T4 by oxidative coupling reactions
Resorption of colloid by receptor-mediated endocytosis
Release of T3 & T4 by exocytosis.
What cells secrete PTH in the parathyroid glands?
Principal (chief) cells
What does the medulla secrete?
Adrenaline and noradrenaline
What does the cortex secrete?
Corticosteroid hormones
What are the three zones of the adrenal cortex?
Zona glomerulosa, zona fasciculata, zona reticularis
