Glands introduction Flashcards
What is a gland?
An epithelial cell or an aggregate of epithelial cells that are specialised for the secretion of a substance
Endocrine glands (3 things)
- Ductless
- Secrete into bloodstream
- Substances (hormones) affect target tissues
Exocrine glands (3 things)
- Ducts
- Secrete into location or region of the body
- Secrete enzymes or lubricants
Examples of endocrine glands (4 things)
- Pituitary gland
- Thyroid gland
- Parathyroid gland
- Pancreas (islets of langerhans)
Examples of exocrine glands (6 things)
- Salivary glands
- Mammary glands
- Pancreas
- Sudoriferous glands (sweat)
- Sebaceous glands
- Lachrymal glands (eye)
Adenogenesis of exocrine glands (5 things)
- Growth hormone received
- Proliferation of cells occurs and EC protein degradation enzymes produced
- Epithelial cells invade space created
- Central cells die off to produce duct (canalicularisation)
- Link to mother cells remained and significant amount of branching
Adenogenesis of endocrine glands (5 things)
- Growth hormone received
- Proliferation of cells and EC protein degradation enzymes produced
- Epithelial cells invade space created
- Produce angiogenic factors to stimulate blood vessel growth in and around epithelial cells
- Link to mother cells broken via apoptosis and virtually no branching
How does branching occur?
Via reciprocal growth- one factor turned on when other is turned off
Simple tubular glands
Large intestine
Simple branched tubular glands
Stomach
Simple coiled tubular glands
Skin (eccrine)
Simple acinar/alveolar glands
Urethra of penis
Simple branched acinar/alveolar glands (2 things)
- Stomach
- Sebaceous glands
Compound tubular glands
Duodenum
Compound acinar/alveolar glands (2 things)
- Pancreas
- Mammary glands
Compound tubuloacinar/alveolar glands
Submandibular salivary gland
What is a merocrine gland?
Fusion of vesicles with apical membrane (e.g. pancreas)
What is an apocrine gland?
Partial loss of cytoplasm (e.g. lactating mammary gland, sweat glands in axilla)
What is a holocrine gland?
Cells are released as a secretion (e.g. sperm in testis)
2 types of merocrine secretion
- Regulated: accumulation of secretory granules in large vesicles which are released upon stimulation
- Constitutive: secretory product packaged into small vesicles and continuously released
What ion does merocrine secretion require?
Calcium (Ca2+)
How does sulphonylurea work in diabetics?
Binds to ATP-sensitive potassium channel and keeps it closed- mimics function of ATP
What is released by breasts in apocrine secretion?
- Fats (neonatal period)
- Milk proteins and fats (lactation)
Holocrine secretion mechanism (4 things)
- Secretory cell gradually fills up with secretory granules
- Cell organelles degenerate and cell dies
- Plasma membrane breaks and contents (secretum) empties
- Dead cells replaced by mitotic division of basal cells
What is glycosylation?
The covalent attachment of sugars by enzymes to proteins and lipids to form glycoproteins and glycolipids
Roles of glycosylation (5 things)
- Aid protein folding
- Prevent protein digestion by intracellular proteases
- Prevent lipid digestion by intracellular lipases
- Cell recognition (blood groups)
- Role on cell to EC matrix attachment
Transepithelial transport- transcytosis (4 things)
- Aqueous channels: AA
- Through bilayer: steroid hormones
- Carrier proteins: thyroxine transport
- Engulfed by endocytosis then released by exocytosis: cholesterol
3 mechanisms for control of gland secretions
- Hormonal: endocrine
- Neural: only stimulus in salivary
- Humoral (a substance which doesn’t have its own control): endocrine
Neurocrine communication
A combination of neural and hormonal mechanisms (e.g. hypothalamus to pituitary)
