Lecture 3 (Part 1)- The Digestive system - Gastrin

Question 1

The digestive system consist of 5 main components:

Answer 1

Mouth

Oesophagus

Stomach

Small intestine

Large intestine

Question 2

what are the accessory organs of the digestive system

Answer 2

Liver

gallbladder

pancreas

Question 3

How do the Accessory Organs of the digestive system connect and communicate with the main digestive system

Answer 3

Connects and communicates with the main digestive system mainly through the duodenum papilla

Question 4

Components of the mouth

Answer 4

Tongue

Salivary glands (parotid, submandibular, and sublingual)

Question 5

The oesophagus connects which two digestive organs together

Answer 5

mouth and stomach

Question 6

What are the two different methods that the mouth can breakdown food?

Answer 6

Mechanical breakdown

saliva breakdown

Question 7

What enzymes are present in saliva and what are their functions?

Answer 7

Saliva contains two key enzymes:

amylase = breaks down carbohydrates,

lingual lipase = breaks down lipids.

Question 8

How does the mouth contribute to the efficiency of digestion?

Answer 8

by increasing the surface area of food through mechanical breakdown. This allows enzymes to more effectively act on the food, starting the digestive process even though the time food spends in the mouth is limited and little digestion occurs.

Question 9

What role does the mouth play in preparing food for digestion in the stomach and intestine?

Answer 9

The mouth lubricates and mixes food into a bolus, setting the conditions for effective digestion in the stomach and intestine by ensuring food is in the right form for further enzymatic action and absorption.

Question 10

what is the cardia in the stomach?

Answer 10

contracts and opens, allowing food to go in; related to the fact that it is close to the heart

Question 11

fundas (stomach) location

Answer 11

upper portion of stomach

Question 12

what are the two curvatures of the stomach

Answer 12

Greater curvature: longer curve

Lesser curvature: smaller curve

Question 13

Pyloric sphincter (stomach)

Answer 13

opens to release processed food ‘chyme’ once it reaches a certain consistency into intestines

between stomach and duodenum

Question 14

Antrum (stomach) location:

Answer 14

bottom portion of the stomach

Question 15

functions of the stomach

Answer 15

Grinds food into chyme

In response to gastrin, the stomach releases HCl and pepsins

Question 16

Acidification of the stomach is important for:

Answer 16

Enzyme activation (pepsin; activated and lipase; deactivated)

Destruction of potentially harmful bacteria

Question 17

Stomach is protected by…

Answer 17

highly alkaline mucus that resists the actions of enzymes and acids

(allows food to be processed without harming the stomach)

Question 18

Stomach is very distensible. True or False

(has the ability to stretch and accommodate varying volumes of food and liquid.)

Answer 18

True

allows it to hold a max of 4L of food

Question 19

How does the stomach progressively release small portions of chyme through the pyloric sphincter that
opens into the duodenum

Answer 19

through peristaltic waves

each of these waves pumps 1-3ml of chyme
into the duodenum (compatible with the speed that we eat; we don’t eat everything all
at once)

Question 20

Secretion of HCl is stimulated by three factors that act at specific receptor on the oxyntic cells (located in the stomach and responsible for releasing HCl):

Answer 20

1. Acetylcholine
2. Histamine
3. Gastrin

Question 21

Maximal acid production is only achieved when all three signals (Acetylcholine, Histamine, Gastrin) are present. True or false

Answer 21

true

Question 22

pH of the stomach ranges between:

Answer 22

1.5-2.5

Question 23

1. how is Acetylcholine released
2. Steps

Answer 23

1. Released by the parasympathetic nervous system via vagus nerve

2a. stretch receptors are activated and sends a signal to the brain

2b. activates vagus nerve

2c. signals the stomach to increase acid secretion

Question 24

Stomach enteroendocrine cells release

Answer 24

histamine and gastrin as food enters the
organ

Question 25

Histamine acts locally through

Answer 25

H2 -receptors on nearby cells (paracrine manner) which release HCl

Question 26

how is gastrin released, what cell does it act on, and what does it stimulate release of

Answer 26

Released by enteroendocrine cells (gastric pits of the pyloric region) and acts directly on oxyntic cells to stimulate acid secretion (HCL)

Question 27

Gastric acids reduce ferric to what and why is this important

Answer 27

ferrous salts

which is important for the absorption of nonheme iron (heme iron comes from animals and is much more easily absorbed than nonheme iron which comes from plants)

Question 28

heme iron comes from where?

Answer 28

animals

Question 29

nonheme iron comes from where

Answer 29

plants

Question 30

which is more easily absorbed non-heme iron or heme iron

Answer 30

heme iron more easily absorbed

Question 31

which is more easily absorbed by the body ferric or ferrous salts

Answer 31

ferrous salts

This is important because the body absorbs ferrous iron more efficiently than ferric iron.

Question 32

Oxyntic cells of the stomach produce:

Answer 32

intrinsic factor

Question 33

intrinsic factor:

Answer 33

a mucoprotein important for the absorption of vitamin B12

(protects it from the acidity and other enzymes which might destroy it before it get a chance to be absorbed)

Question 34

Gastric secretion occurs in three phases:

Answer 34

1. Cephalic: triggered by smell, taste, and/or thought of food (accounts for 30% of acid secretion); neurological response
2. Gastric: triggered by stomach distension and by amino acids and peptides activating chemoreceptors (accounts for 60% of acid secretion)
3. Intestinal: triggered by the distention of the small intestine and by the presence of proteins and products of protein digestion (accounts for 10% of
   acid secretion)