Mx Flashcards
What do exocrine glands do?
Ducted
Excrete into a location/region of body through a duct
Cells at ape of duct secrete enzymes or lubricants
Name some exocrine glands
- SALIVARY GLAND: buccal cavity=saliva for partial digestion of food & lubrication
- PANCREAS: amylase (carbohydrates), trypsin (proteins), lipase (fats)
- MAMMARY: produces colostrum & milk in response to prolactin & oxytocin
- SWEAT GLANDS: secrete sweat for thermoregulation
- SEBACEOUS GLAND: secretes sebum onto the skin & ear (contributes to ear wax)= protection from pathogens
- LACHRYMAL GLANDS: in eye= secrete water to moisten eye & produce lysozyme
What is acini?
Multicellular gland
What does serous, mucous and mixed serous-mucous acinus do?
SEROUS ACINI: secretes proteins in an isotonic watery fluid
MUCOUS ACINUS: secretes mucin lubricant
MIXED SEROUS-MUCOUS ACINUS: serous acinus forms a serous demilume around mucous acinus
What do the secretory units of the salivary glands?
Secretory units merge into INTERCALATED DUCTS which are lined by simple low cuboidal epithelium and surrounded by myoepithelial cells
What does the striated ducts of the salivary gland do?
STRIATED DUCTS: folded basal membrane- enable active transport of substances out of the duct. Water resorption and ion secretions= saliva is hypotonic (reduced Na, Cl ions)
Striated ducts lead into interlobular (excretory) ducts lined with a tall columnar epithelium
Glands are dived into lobules by connective tissue septa
Each lobule contains numerous secretory acini
Describe the generation of a gland
Generation of gland
Growth signal
Proliferation of daughter cells
EC protein degradation enzymes produced
Epithelial cells invade space created
=Exocrine gland- canalicularisation=central cells die off to produce duct
=Endocrine: produce angiogenic factors to stimulate blood vessel growth in and around epithelial cells= link to mother cells broken through apoptosis
What two of types epithelial cells are there in exocrine glands
Exocrine glands: two types of epithelial cells
- Cell lining the ducts
- Cells that make secretory proteins
Some cells at secretory ends of the ducts change morphology and class= myoepithelial
Myoepithelial: features of smooth muscle and epithelial = help eject secretions
Describe Holocene secretion
HOLOCENE- the entire cell dies and becomes the secretion (sebaceous gland)
- Secretory cell gradually fills up with secretory granules
- Cell organelles degenerate and cells die= PM breaks and contents (secretum) empties
- Dead cells replaced by mitotic division of the basal cells
Cytocrine gland- cells are released as secretion e.g. sperm in seminiferous tubule
Describe merocine secretion
MEROCINE: only secretory product is released e.g. parotid gland, endocrine glands of pancreas
- Regulation of exocytosis
o Calcium ion specific signals for active secretion
o Cargo vesicles migrate to cell surface along microtubules and fuse with plasmalemma
o Cargo released to EC space
Describe apocrine secretion
APOCRINE: small piece of cell’s cytoplasm accompanies the secretory product (lactating mammary gland, sweat glands)
Describe Golgi apparatus secretion
GOLGI APPARATUS SECRETION
- Cis face of Golgi faces ER= entry face that receives small membrane vesicles from ER
- Vesicle membranes are incorporated into the Golgi membranes= contents enter Golgi cisternae
- Trans face faces away from nucleus and towards PM: exit face- vesicles leave Golgi and move to targets
What is the glycosylation of proteins and its role in the cell?
Glycosylation of proteins: covalent attachment of sugars by enzymes to proteins and lipids to form glycoproteins and glycolipids
Role:
- Aid protein folding
- Prevents protein digestion by IC protease
- Prevents lipid digestion by IC lipases
- Cell recognition (blood group)
- Role on cell to EC matrix attachment
Describe phagocytosis, pinocytosis and transcytosis
PHAGOCYTOSIS: engulf other cells or particles= used by immune system cells e.g. macrophages. Explored in drug design
PINOCYTOSIS: liquid droplets are ingested by cells= used by all cells especially smooth muscle
TRANSCYTOSIS: Transepithelial transport
Transcytosis is the transfer of molecules across cells from one side to the other
A process that entails endocytosis, vesicular transfer and exocytosis, and which speeds the bulk movement of molecules through tissues. In some cases, transcytosis is receptor-mediated, and is often carried out by distinct vesicles called caveolae,
Describe constitutive secretion and its function
CONSTITUTIVE SECRETIONS IS REQUIRED TO MAINTAIN PM
- Polarised cells secreted different classes of proteins
- Protein from ER through GA – not modified to specific location. Thus is packaged to be sent to the PM for immediate secretion
- Secretory vesicles leave GA and merge with PM- releasing cargo outside the cell by exocytosis
- Lipids and membrane of vesicle are donated to PM
- WBC use constitutive secretion to release interleukins
- Fibroblast constitutively secrete proteins such as collagen and proteoglycans and help to maintain the structural integrity of connective tissue
