Exocrine glands Flashcards
What exocrine glands are there in the digestive system?
Salivary glands, esophagial glands (stomach- and pancreas glands), bile ducts (small intestine and colon)
What other endocrine glands are there?
Sweat, lacrimal, respiratory, prostate, cervix, mammary
What other secretory epithelia are there?
Choriod plexus, cilliary, nephrons, fallopian tubes,
What does the exocrine glands secrete?
1) Electrolyte containing fluid, that is appropiate for its function (iso/hypo/hypertonic)
2) macromolecules, such as enzymes, mucus, GFs, peptides, immunoglobulins, autocrine/paracrine mediators,
What is the lacrimal gland, and what tonicity is the secrete?
Tear gland, isotonic
What are eccrine/apocrine glands, and how is tonicity?
Sweat glands, hypotonic
What is the composition of human sweat in a healthy person?
Na+: 10-40 mmol/l, Cl-: 0-30 mmol/l, K+: 2-25 mmol/l, pH: 6,8-7,3, osmolarity: 154 +/- 30 mosmol/l
What is the composition of human sweat in a patient with cystic fibrosis?
Na+: 60-145 mmol/l, Cl-: 70-120 mmol/l, K+: 5-60 mmol/l, pH: 4,5-7,3, osmolarity: 300 mosmol/l
What is the function of salivary glands?
Lubrication, emulsification of food, facillitation of swallowing, mastication and speech, protection of teeth and oral/oesophageal mucosa, taste, initial digestion of starch and lipids, oral acid buffering, antimicrobial actions
How much saliva does a healthy person secrete a day?
0,5-1,5 L
What is the composition of saliva?
99 % H2O, 1 % salts: hypotonic
What are the major organic components of saliva?
Proline-rich proteins, mucin glycoproteins, enzymes (amylase, lipase, rebonuclease), antimicrobial agents (lactoferrin, IgA), GFs
What does alpha-amylase do?
Begins on starch deigestion
What does lingual lipase do?
Breaks down dietary treglycerides in mouth and stomach
What can cause salivary glands disfunction?
Medication (a lot of antidepressants, app. 30 % of all medications cause dry mouth), radiation/chemo therapy, chronic inflammatory diseases, genetic disorders (cytic fibrosis), aging, neurological diseases etc.
Describe the structure of the tear gland.
Acinus and duct. The acinus is a round struture surrounded be exocrine cells, that sercretes NaCl and H2O into the center.
Describe the channel composition of the cells in lacrimal gland acinus.
Luminal side: Cl- channel
Basolateral side: Na+/K+/Cl- cotransporter, Na+/K+-ATPase, K+ channel.
Na+ is transported papcellularly, H2O by simple diffusion following Na+
Describe the structure of a sweat gland.
Secretory coil and sweat duct.
Describe the channel composition of the cells in sweat gland secretory coil.
Luminal side: Cl- channel
Basolateral side: Na+/K+/Cl- cotransporter, Na+/K+-ATPase, K+ channel.
Na+ is transported papcellularly, H2O by simple diffusion following Na+
Describe the channel composition of the cells in sweat gland duct.
Luminal side: Cl- channel (inward rectifer, CFTR), ENaC, K+ channel
Basolateral side: Na+/K+-ATPase, K+ channel, Cl- channel
What channel is affected by cystic fibrosis in the sweat gland duct cells?
CFTR (cystic fibrosis transmembrane conductance regulator)
Describe how the dysfunctional CTFR can lead to the sweat composition found in subjects with cystic fibrosis.
CFTR dysfunction –> no Cl- influx on luminal side –> Vm = 0 mV on luminal side –> Vm = -70 mV on basolateral side –> Cl- channel is not gated –> no signal –> high osmolarity
Describe the structure of a salivary gland.
Simmilar to tear gland: acinus and duct + myoepithelial cells around the acinus
Describe the channel composition of the cells in salivary gland acinus (isotonic secretion)
Luminal side: Cl- channel (CaCC=Ca2+ activated Cl- channel)
Basolateral side: Na/K/Cl cotransporter, Na+/K+-ATPase, K+ channel
Na+ is transported paracellularly, H2O is transported both para- and transcellularly (follows Na+)
Describe the signaling pathways for macromolecule secretion of the cells in salivary gland acinus.
Basolateral side: beta-receptors (adrenalin/NA), M3-receptors (Acetylcholine)
Beta-receptors activated by sympaticus –> AC activation –> increase in cAMP –> activation of PKA –> exocytosis of protein filled vesicles
M3-receptors activated by parasympaticus –> PLC cleaves PIP2 into IP3 and DAG –> IP3 gates Ca2+ channels on ER –> Ca2+ increase –> PKC activation –> exocytosis of mucin filled vesicles
What does the salivary gland ducts do?
Modify primary secretion by acini and make it hypotonic
How does the salivary gland ducts modify the primary secretion?
Absorb a lot of Na+ and Cl-, and secrete a little K+ and HCO3-. The ducts are “water tight” –> saliva becomes watery and hypotonic
Describe the channel composition of the cells in salivary gland ducts.
Luminal side: Cl- channel (inward, CFTR), ENaC, K+ channel
Basolateral side: Na+/K+-ATPase, K+ channel, Cl- channel
How does the sympathetic and parasympathetic systems influence the salivary duct cells secretion?
Sym: K+ and HCO3- secretion
Para: NaCl absorbtion
