Exocrine glands

Question 1

What exocrine glands are there in the digestive system?

Answer 1

Salivary glands, esophagial glands (stomach- and pancreas glands), bile ducts (small intestine and colon)

Question 2

What other endocrine glands are there?

Answer 2

Sweat, lacrimal, respiratory, prostate, cervix, mammary

Question 3

What other secretory epithelia are there?

Answer 3

Choriod plexus, cilliary, nephrons, fallopian tubes,

Question 4

What does the exocrine glands secrete?

Answer 4

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,

Question 5

What is the lacrimal gland, and what tonicity is the secrete?

Answer 5

Tear gland, isotonic

Question 6

What are eccrine/apocrine glands, and how is tonicity?

Answer 6

Sweat glands, hypotonic

Question 7

What is the composition of human sweat in a healthy person?

Answer 7

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

Question 8

What is the composition of human sweat in a patient with cystic fibrosis?

Answer 8

Na+: 60-145 mmol/l, Cl-: 70-120 mmol/l, K+: 5-60 mmol/l, pH: 4,5-7,3, osmolarity: 300 mosmol/l

Question 9

What is the function of salivary glands?

Answer 9

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

Question 10

How much saliva does a healthy person secrete a day?

Answer 10

0,5-1,5 L

Question 11

What is the composition of saliva?

Answer 11

99 % H2O, 1 % salts: hypotonic

Question 12

What are the major organic components of saliva?

Answer 12

Proline-rich proteins, mucin glycoproteins, enzymes (amylase, lipase, rebonuclease), antimicrobial agents (lactoferrin, IgA), GFs

Question 13

What does alpha-amylase do?

Answer 13

Begins on starch deigestion

Question 14

What does lingual lipase do?

Answer 14

Breaks down dietary treglycerides in mouth and stomach

Question 15

What can cause salivary glands disfunction?

Answer 15

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.

Question 16

Describe the structure of the tear gland.

Answer 16

Acinus and duct. The acinus is a round struture surrounded be exocrine cells, that sercretes NaCl and H2O into the center.

Question 17

Describe the channel composition of the cells in lacrimal gland acinus.

Answer 17

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+

Question 18

Describe the structure of a sweat gland.

Answer 18

Secretory coil and sweat duct.

Question 19

Describe the channel composition of the cells in sweat gland secretory coil.

Answer 19

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+

Question 20

Describe the channel composition of the cells in sweat gland duct.

Answer 20

Luminal side: Cl- channel (inward rectifer, CFTR), ENaC, K+ channel
Basolateral side: Na+/K+-ATPase, K+ channel, Cl- channel

Question 21

What channel is affected by cystic fibrosis in the sweat gland duct cells?

Answer 21

CFTR (cystic fibrosis transmembrane conductance regulator)

Question 22

Describe how the dysfunctional CTFR can lead to the sweat composition found in subjects with cystic fibrosis.

Answer 22

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

Question 23

Describe the structure of a salivary gland.

Answer 23

Simmilar to tear gland: acinus and duct + myoepithelial cells around the acinus

Question 24

Describe the channel composition of the cells in salivary gland acinus (isotonic secretion)

Answer 24

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+)

Question 25

Describe the signaling pathways for macromolecule secretion of the cells in salivary gland acinus.

Answer 25

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

Question 26

What does the salivary gland ducts do?

Answer 26

Modify primary secretion by acini and make it hypotonic

Question 27

How does the salivary gland ducts modify the primary secretion?

Answer 27

Absorb a lot of Na+ and Cl-, and secrete a little K+ and HCO3-. The ducts are “water tight” –> saliva becomes watery and hypotonic

Question 28

Describe the channel composition of the cells in salivary gland ducts.

Answer 28

Luminal side: Cl- channel (inward, CFTR), ENaC, K+ channel
Basolateral side: Na+/K+-ATPase, K+ channel, Cl- channel

Question 29

How does the sympathetic and parasympathetic systems influence the salivary duct cells secretion?

Answer 29

Sym: K+ and HCO3- secretion
Para: NaCl absorbtion