S3 Glands Flashcards
What is a gland?
An epithelial cell or aggregate of epithelial cells that are specialised for the secretion of a substance
What is secretion?
The production and release of materials by a cell or aggregate of cells
How do glands regulate human physiology?
Receive stimulus from the brain
Receive stimulus from circulating levels of chemicals and from neighbouring cells
What are endocrine glands?
Ductless, secrete hormones directly into the blood stream and secretion acts on distant parts of the body
What are 3 examples of endocrine glands?
- Pituitary gland
- Thyroid gland
- Parathyroid gland
What are exocrine glands?
Ducted glands that secrete enzymes/lubricants into a location or region of the body through a duct
What are 5 examples of exocrine glands?
- Salivary gland
- Pancreas
- Mammary gland
- Sebaceous gland
- Lachrymal glands
Which cells of the duct secrete the product?
The cells at the apex of the duct
What a growth factor causes gland formation?
Fibroblast-growth factor
How are glands produced in uterus development?
- Epithelial cells proliferate due to FGF released by MSC
- In exocrine glands, central cells die off to produce a duct (canalicularisation)
- In endocrine glands, produce angiogenesis factors to stimulate blood vessel growth in and around the epithelial cells (and duct cells disappear)
What do some cells at the excretory end of the duct change morphology into? What is their role?
Myoepithelial cells - have features of epithelial cells and smooth muscle cells - help to eject secretions from the duct
What is another name for alveolar?
Acinar
What are the 7 different gland duct shapes?
- Simple tubular
- Simple branched tubular
- Simple alveolar
- Simple branched alveolar
- Compound tubular
- Compound alveolar
- Compound tubuloalveolar
What is an example of where you can find simple tubular ducts?
Intestinal glands
What is an example of where you can find simple branched tubular ducts?
Stomach glands
What is an example of where you can find simple alveolar ducts?
No important examples in human
What is an example of where you can find simple branched alveolar ducts?
Sebaceous glands
What is an example of where you can find compound tubular ducts?
Duodenal glands of small intestine
What is an example of where you can find compound alveolar ducts?
Mammary glands
What is an example of where you can find compound tubuloalveolar ducts?
Salivary glands
What are the two types of secretion from salivary glands?
Mucous and serous
What are 5 stages of salivary gland growth and development?
- Prebud
- Initial bud
- Psuedoglandular
- Canalicular
- Terminal bud
What is merocrine secretion? Give an example of a gland.
Fusion of vesicles with apical membrane
Acinar and endocrine glands of the pancreas
What is apocrine secretion? Give examples of glands.
Partial loss of cytoplasm
Lactating mammary gland and sweat glands in external genitalia
What is Holocene secretion? Give an example of a gland.
Complete loss of cytoplasm or cell
Sebaceous gland in skin
What is cytocrine secretion? Give an example of a gland.
Cells are released as a secretion
Spermatid released from the seminiferous tubule (testis)
What are the two merocrine pathways?
- Regulated secretion - secretory granules accumulate in large vesicles and are released by exocytosis upon stimulation (regulated by Ca2+)
- Constitutive secretion - secretory product isn’t concentrated into granules, it is packaged into small vesicles and is continuously released to the cells surface - used to repopulate the plasma membrane with plasma proteins
How does insulin secretion occur?
- Glucose enter cell through GLUT2
- Glucose is metabolised, this releases ATP
- The ATP activates the ATP-sensitive K+ channels resulting in K+ moving out of the cell
- This leads to membrane depolarisation
- Depolarisation causes Ca2+ influx
- Ca2+ activates the vesicles containing insulin to exocytose, releasing insulin
What is the only thing secreted by apocrine secretion in the neonatal period?
Fats
During lactation, what is secreted by apocrine secretion?
Fats and proteins
Describe the process of Holocene secretion in sebaceous glands.
- Secretory cell fills up with secretory granules
- Cell organelles degenerate
- Cell dies
- Plasma membrane breaks down and the contents empty into the duct
- The dead cells are replaced by mitotic division of the basal cells
What is glycolysation of proteins?
The covalent attachment of sugars (by enzymes) to proteins and lipids to form glycoproteins and glycolipids
What are the roles of glycolysation of proteins/lipids?
- Aids protein folding
- Prevents protein and lipid digestion by intracellular proteases/lipases
- Cell recognition
- Involved in cell to ECM attachment
How many proteins undergo glycolysation?
About half
Where does glycolysation happen?
In the Golgi apparatus
What is exocytosis?
Secretion of molecules outside the cell via a vesicle fusing to a membrane
What is endocytosis?
Engulfing of molecules inside the cell via vesicle formation
What is phagocytosis? Which cells use this?
Process by which cells envelop or engulf other cells or particles.
Immune response cells - macrophages, dendritic cells, neutrophils, basophils and eosinophils
What is pinocytosis? Which cells use this?
Process in which liquid droplets are ingested by cells
Used by all cells, especially smooth muscle cells
What are the types transepithelial transport?
Transcytosis from lumen to interstitium or the opposite way.
- molecules move through aqueous channels in intercellular junctions (paracellular transport) - amino acids
- molecules move through lipid cell membranes (trasncellular transport) - steroid hormones
- molecules transported through carrier proteins into/out of cells - thyroxine transport across thyroid follicular cell
- molecules may bind to cell surface receptors, become engulfed by cell membrane (endocytosis) and then released inside the cell or expelled via vesicles out of the cell and into the extracellular space (exocytosis) - cholesterol transport
What is an example of a humoral stimulus in glandular control?
Low blood Ca2+ concentration stimulates secretion of parathyroid hormone (PTH) which acts to increase blood Ca2+
Through feedback loop
What is an example of a neural stimulus in glandular control?
Preganglionic sympathetic fibres stimulate adrenal medulla cella’s to secrete catecholamines (amino acid derivatives) - adrenaline and noradrenaline
What is an example of a hormonal stimulus in glandular control?
The hypothalamus secretes hormones that stimulates the anterior pituitary glands to secrete hormones that stimulate other endocrine glands to secrete hormones
What is neurocrine communication?
Release of neurotransmitters
