Introduction To Glands - Lecture 5 Flashcards
What is the definition of a gland?
An epithelial cell or an aggregate of epithelial cells which are specialised for the secretion of a substance.
What are the stages of secretion?
Production and release of materials (by a cell or aggregate of cells)
What is autocrine secretion?
The molecules act of the same cells that produced them.
Paracrine means they act of nearby cells
How do glands regulation human physiology?
Mainly by receiving signals from the brain (CNS), but can also from circulating chemicals or neighbouring cells.
How are glands normally classified?
- Structure
2. How there products are released
What is the difference between and endocrine and an exocrine gland?
Endocrine glands do not have a duct
Who do endocrine glands secrete hormones?
Straight into the blood so Nora,l act on something further away in the body
What type of gland is the pituitary and where is it situated?
Endocrine gland, found bellow the hypothalamus.
What is the pituitary glands divided into?
Anterior and posterior regions of the gland
What glands are produced in the anterior part of the pituitary gland?
ACTH (released in response to stress)
LH (luteinising hormone - can stimulate ovulation or testosteroneproduction)
FSH (follicle-stimulating hormone - regulates development, growth, pubertal maturity)
TSH (Thyroid stimulating hormone - stimulates metabolism)
Prolactin - stimulates milk production
Somatotropin - regulates growth of body and tissues
What hormones does the posterior part of the pituitary gland produce?
Vasopressin (and anti- diuretic hormone) - prevents water loss from the kidney
Oxytocin - signals uterus for delivery and gestation and ejection of milk during breast feeding
What type of glands are the thyroid and parathyroid gland?
Endocrine
What does the thyroid gland produce?
T3 and T4 which control metabolism of calcitonin, are involved in calcium homeostasis
What does parathyroid hormone do?
It is involved in calcium homeostasis.
What are the secretions from exocrine glands made up of?
Mainly lubricants and enzymes
What type of gland is the salivary gland what does it produce?
Exocrine - secretes saliva for partial digestion of food and lubrication
What type of gland is the pancreas what does it produce?
Exocrine - secretes enzymes; amylase, trypsin and lipase.
These digest carbohydrates, proteins and fats.
What type of gland is the mammary gland what does it produce?
Exocrine - Colostrum and milk in response to oxytocin and prolactin
What type of gland is the sweat gland what does it produce?
Exocrine - secretes sweat which regulates body temperature
What type of gland is the sebaceous gland what does it produce?
Exocrine - secretes sebum onto the skin and ear to protect these tissues from pathogens
What type of gland is the lachrymal gland what does it produce?
Exocrine - secretes water in the eye and also produces lysozyme to attack bacteria
What is lysozyme.
An enzyme produced by the lachrymal gland which attacks bacteria in the eye
Which cells secretes the products in the exocrine gland?
Only the calls at the apex of the ducts
Which cells secretes the products in the endocrine gland?
All the epithelial cells in the gland secrete the hormones
How are the cells, involved in secretion of products, in the exocrine glands arranged?
There are 2 layers of cells, the inner are complex cells and these are responsible for producing the sebum, and the calls in the duct are simple cuboidal and these release the product at the end of the apex.
Describe the structure for the thyroid gland?
There is a inner colloid which contains the thyroglobulin precursors for T3 and T4 and there are outer follicular cells where thyroid is produced and then simple cuboidal epithelial cells which line the gland.
How are glands generated?
They are made in utero, they begin with a layer of epithelial cells, the epithelia produces a substance which is a fibroblast growth factor, which makes the epithelial grow towards the mesenchymal cells which sit underneath the epithelial cells.
The epithelial cells produce enzymes which breaks down the connective tissue where the mesenchymal cells lie.
The inner cells undergo apoptosis and produce a duct and the apical cells begin to differentiate. (Exocrine glands)
In endocrine glands angiogenic factors stimulate growth of blood vessels in and around the epithelial cells and they break away from the epithelial surface.
How does branching occur?
It is controlled by other growth factors,
1 causes elongation and 1 causes branching
In exocrine glands what are the 2 types of epithelial cells?
Cells lining the ducts
Cells making secretory products
Which type of gland duct don’t exist in adults?
Simple alveolar (Acinar)
What are the 3 types of acini in the salivary gland?
- Serous
- Demilune - ‘half moon’ the inner layer is a mucous acinus which the serous demilune has been squeezed out of and then on the surface of the serous there is a layer of myoepithelial cells
- Striated
What are the 2 ducts?
Interlobular ducts - first one down the gland
Intercalated - these are between the acini
What is merocrine secretion?
The vesicles are fused with the membrane and released by the epithelial cells
Eg. Acinar and endocrine glands in the pancreas
What is apocrine secretion?
When the top part of the cell is lost onto the duct
Eg. Sweat glands, mammary glands
What is holocrine secretion?
The whole cytoplasm or epithelial cell is released in the secretion
Eg. Sebaceous gland
Which type of secretion is a type of exocytosis?
Merocrine secretion
What are the 2 merocrine secretion pathways?
Regulated secretion - needs Ca2+ to work released upon stimulation
Constitutive - continuously released
What is a cargo?
A vesicle
What is an example of regulated merocrine secretion?
Release of insulin from the pancreas
What type of secretion causes the signet fragment?
Apocrine secretion, part of the cell is still attached to the product released so it gives the ‘ring’ structure
What is an example of apocrine secretion?
During lactation in pregnancy, both fats and proteins are released by apocrine secretion
How are the cells after holocrine secretion reproduced?
By mitosis and cytokinesis
What is an example of holocrine secretion?
In the sebaceous gland the secretory granules build up and the cell organelles degenerate, the cell dies and the plasma membrane breaks and contents are emptied into the plasma (contents are called the secretum)
What is glycation?
The production of glycoproteins in the absence of enzymes
What is glycosylation?
The covalent attachment of sugars by enzymes to proteins and lipids to form glycoproteins and glycolipids
What does glycosylation have a critical function in?
Glycosylation is a critical function of the biosynthesis-secretory pathway in the endoplsamic reticulum
What are the roles of glycosylation?
It aids protein folding, prevents protein and lipid digestion by intracellular enzymes, helps with cell to extracellular matrix attachment
What is pinocytosis?
It is the process by which lipid droplets are ingested by cells
(It is used by all cells, esp. smooth muscle cells)
Why is the removal of cholesterol from the blood important?
Because cholesterol is used for the production of steroid hormones (it uses the pit system)
What are the 3 types of glandular control?
Humoral, neural, hormonal
