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PHSL 233 > L27 > Flashcards

L27 Flashcards

1
Q

what are some endocrine secretions of the GI system and what is their role

A

 Regulation of motility and secretion

 gastrin stimulation of stomach motility and gastric acid secretion
 CCK and secretin inhibition: stomach motility, stimulation: pancreatic
secretion

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2
Q

what are some exocrine secretions of the GI tract and what is their function

A 
Prepare food for digestion by:
 diluting it to the osmolality of the plasma
 altering pH for optimal digestion
 digesting food
 protection/lubrication
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3
Q

what are the major components of GI secretions

A

mucus = protection

enzymes = breakdown

electrolytes and serous solutions = further mixing and preparations

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4
Q

how much saliva do we produce per day

A

1.5 L

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5
Q

what is the osmolarity of saliva and is it hyper or hypotonic

A

osmolarity = 100mOsmol

this is less than 300 therefore it is a hypOtonic solution

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6
Q

what is the concentration of ions in saliva

A

Na = 40 mmol

K = 15

Cl = 25

HCO3 = 30

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7
Q

what is the pH of saliva

A

7.5

it is slightly higher than plasma (7.4) because it contains more bicarbonate ions (30 compered to 24mmol in plasma)

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8
Q

The GI system is a long tube that is constricted in some areas and has connections to other organs. It also secretes things

Twe are producing a lot f fluid which is 2x the plasma volume but the final feces only has 200mL of water in it

Diarrhea messes up the water homeostasis and people die

A

j

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9
Q

saliva is essential and has a number of roles. what are these

A

 oral hygiene

aids in
 talking
 chewing and swallowing by moistening and
dissolving food

 assists in rendering food isosmotic

 amylase - starch digestion

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10
Q

what is xerostomia

A

(dry mouth, lack of saliva)

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11
Q

xerostomia causes tooth decay. why

A

This happens because food is quite acidic (even healthy things)

Sugar in the mouth is converted to acids by bacteria in the mouth and the alkalinity of saliva helps balance that acidity

when you aren’t producing saliva then this cant happen

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12
Q

saliva is the window to your body as it can be used to diagnose many things. what can saliva annalise

A 
 DNA (forensic, ancestry)
 cancer
 heart attack
 infections (HIV)
 homeopathy (neurotransmitter balance, burnout syndrome, migraine)
 COVID-19 testing
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13
Q

there are 3 pairs of salivary glands. what are they

A

 parotid (serous)

 submandibular (mixed mucous/serous)

sublingual (mucous)

 plus minor buccal glands in mouth, pharynx and
oesophagus

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14
Q

why would the submandibular and sublingual salivary glands secrete mucus

A

to protect the epithelia from abrasion

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15
Q

what are the 2 anatomical structures that make up the salivary glands

A

acinus and ducts

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16
Q

what cells are in the acinus and what do they secrete

A

acinar cells are the site of primary secretion

serous acinar cells secrete zymogen granules

mucous acinar cells secrete mucus

over all the acinar cells secrete isotonic NaCl solution

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17
Q

there are 2 kinds of ducts. what are these

A

intercalated and striated ducts

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18
Q

what is the functions of the ducts

A

drain secretions from acinar cells into mouth

reabsorption from primary fluid to..
 dilute solution
 limited further secretion

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19
Q

1.4L of saliva is produced per day. what is the basal rate of production and how can this be increased

A

basal rate = 0.5mL/min

stimulation via the special sensors can increase this 10x

20
Q

what is the composition of saliva

A

mucus (sublingual & submandibular & buccal glands)

digestive enzymes
 a-amylase, parotid gland
 salivary glands of tongue - lingual lipase

serous secretion
 primarily parotid, lesser extent submandibular
 hypo-osmotic solution of NaCl with slightly elevated K+ and HCO3-
 composition varies with rate of secretion

21
Q

what are the digestive enzymes in saliva and where are they secreted from

A

 a-amylase, parotid gland (main enzyme)

 salivary glands of tongue - lingual lipase

22
Q

where do the serous secretions in the saliva come from

A

 primarily parotid, lesser extent submandibular

23
Q

describe the serous secretion from the primarily parotid, lesser extent submandibular

A

 hypo-osmotic solution of NaCl with slightly elevated K+ and HCO3-

composition varies with rate of secretion

24
Q

what are some CRITICAL points about the osmolarity of saliva

(5 points)

A

 saliva is always hypo-osmotic

 [Na+] & [Cl-] < in plasma

 [K+] higher than plasma

 [HCO3-] higher than plasma

 osmolarity increases as rate of secretion increases

25
Q

what does composition of saliva vary with the rate of secretion (increase in osmolarity as the rate increases)

A

because the rate of secretion by acini
variable whereas the rate of absorption by duct is constant

this means that….at slow rates of secretion
 primary fluid in contact with duct epithelium for extended
period of time meaning that you will get greater absorption of NaCl (more time for it to be absorbed)

 high rates of secretion the primary fluid passes through
ducts rapidly meaning there is limited absorption of NaCl

26
Q

Saliva
A. is hypertonic during stimulation of secretion.

B. helps digesting starch.

C. contains enzymes such as pepsin.

D. contains less bicarbonate than plasma.

E. is rich in NaCl.

A

A. hypOtonic

C. pepsin is in the stomach

D. more bicarbonate then plasma

E. this is true but in order for it to be correct it would need to say [rich in NaCl compeered to the plasma]

B is correct

27
Q

what kind of epithelium is in the ducts

A

tight obsorbitive epithelium

28
Q

what epithelium is in the acini

A

leaky secretory epithelia

check??

29
Q

what do striated and excretory ducts do

A

they modify the fluid by
reabsorption of Na+ and Cl without water!!!

they secrete…
 limited amount of K+ and HCO3- secretion depending on species
 mucus

30
Q

describe saliva and water secretion from the acinar cells

A

Key players are NKCC transporters

Bicarbonate coming from the acini and Cl as well (HCO3- from carbonic anhydrase and Cl from NKCC1). The Cl will compete with the bicarbonate (CFTR?)

There is also NA/K ATPase in basolateral membrane

Na and water go through the paracellular pathway

Water secretion and reabsorption require leaky epithelium

NKCC1 is on the basolateral side and dives water secretion. This is driven by Na/K ATPase

This electrical greident dives Na secretion via the paracellular pathway to balance out the change

This creates an osmotic force and drives water secretion through both the transcellular (AQP) and the paracellular pathway

31
Q

what transporters drive water secretion in acinar cells

A

NKCC1 is on the basolateral side and dives water secretion. This is driven by Na/K ATPase

This electrical greident dives Na secretion via the paracellular pathway to balance out the change

This creates an osmotic force and drives water secretion through both the transcellular (AQP) and the paracellular pathway

32
Q

how is saliva modified

A

through reabsorption in the duct cells

33
Q

describe the process in which duct cells modify the saliva

A

Once you have produced isotonic primary saliva the first things that happens is the NA is reabsorbed via ENaC

The faster we produce saliva the less we can reabsorbe (through ENAC)

K is secreted (we dont know how). There is more K coming from secretion of K in the duct cells of the salivary gland than the acinar cells

We then have the carbonic acid production to produce bicarbonate and the H+ ion is then moved the basolateral side to control pH

We can then secrete CO3- through the bicarbonate chloride exchanger

Therefore you end up with a hypotonic saliva

34
Q

describe Na reabsorption in the duct cell

A

Once you have produced isotonic primary saliva the first things that happens is the NA is reabsorbed via ENaC

The faster we produce saliva the less we can reabsorbe (through ENAC)

35
Q

where does most of the K secretions in the saliva come from

A

the duct cells

36
Q

in the duct cell carbonic anhydrase produces H+ and HCO3-

what happens to these

A

H+ go through Na/H exchanger to regulate pH on basolateral membrane

HCO3-

36
Q

in the duct cell carbonic anhydrase produces H+ and HCO3-

what happens to these

A

H+ go through Na/H exchanger to regulate pH on basolateral membrane

We can then secrete CO3- through the bicarbonate chloride exchanger in the apical membrane

37
Q

what channels are in the apical membrane of the duct cells

A

ENaC

a K channel

CFTR

Cl/HCO3- exchanger (Cl in and HCO3 out)

38
Q

what transporters are in the basolateral membrane of the duct cells

A

Na/H exchanger

Na/HCO3- cotransporter (both into the cell)

39
Q

what regulates salivary secretion

A

mainly nervous (both branches of the ANS)

40
Q

describe the parasympathetic NS in relation to regulation of the salivary secretions

A

 main system (acetylcholine)

activation stimulates blood flow which causes production of a high amount of serous saliva

The PNS helps to increase perfussions of the salivary gland because to make more saliva you need more water

41
Q

describe the sympathetic NS in relation to regulation of salivary secretion

A

noradrenalin binds to α1 and b2 receptors which inhibits blood flow and causes low amount of mucous saliva

SNS decreases perfusion to the salivary glands therefore less water = less saliva

42
Q

the ANS is the main thing that regulates salivary production. what is the other thing

A

saliva is secreted at the  thought of food
 approach of food
 food in the mouth

43
Q

there are 2 reflexes involved in saliva secretion. what are these

A

conditioned reflex
 due to sight and smell of food
 learned response – Pavlov

unconditioned reflex
 due to presence of food in mouth and response to taste receptors

44
Q

Secretion of a hypotonic salivary solution

A. depends on sympathetic activation.

B. requires a basolateral chloride and bicarbonate channel in acini.

C. requires para-cellular re-absorption of Na+ in acini.

D. requires leaky acinar epithelium.

E. requires an apical Na+/K+/2Cl- co-transporter to re-absorb
Na+ in duct cells.

A

A. PNS

B. apical

C. secretion?

E. duct cells

D is correct

PHSL 233 (31 decks)

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