Gastrointestinal System

Question 1

Ingestion

Answer 1

The intake of food into the GI tract via the mouth

Question 2

Mechanical Processing

Answer 2

Physical breakdown of food by the teeth, stomach and intestines

Increases the surface area of food, allowing enzymes to work more efficiently

Question 3

Chemical Processing

Answer 3

Breakdown of complex molecules (polymers) into monomers using enzymes and other substances

Question 4

Secretion and Absorption and Egestion

Answer 4

Secretion: release of water, acid, enzymes, buffers and salts which aid in chemical digestion and absorption

Absorption: uptake of useful molecules across the epithelium of the GI tract and into interstitial fluid

Egestion: removal of waste products

Question 5

Breaking down of polymers

Answer 5

we cannot absorb polymers such as proteins, lipids and carbohydrates so they must be broken down by chemical and physical digestion

Proteins are broken down into amino acids
Lipids are broken down into fatty acids and glycerol
Carbohydrates are broken down into monosaccharides

Question 6

What is someone lacking if they are lactose intolerant

Answer 6

lactase enzyme

Question 7

Layers of the GI tract wall

Answer 7

Serous: fibrous connective tissue - structure and support

Muscularis: two layers of smooth muscle. Antagonist pair. Lognitudinal muscle (down GI tract) and circular (around circumference of GI tract). creates peristalsis

Submucosa: connective tissue layer which contains blood vessels, lymph vessels and nerves

Mucosa: inner lining, cells get replaced every 5-7 days

Lumen

Question 8

Chemical and Physical processing in the mouth

Answer 8

Chemical: amylase breaks down starch into maltose, saliva makes food softer and helps form a bolus. Taste sensation increases to prepare the rest of the digestive system = stimulation of gastric juices

Mechanical: teeth. Food is broken down into smaller pieces creating a larger surface area for enzymes to act on. helps mix food with saliva

Question 9

Voluntary phase of swallowing (deglutition)

Answer 9

tongue pushes bolus into the pharynx whilst oesophagus is kept closed. Bolus travels down the oesophagus via peristalsis

Question 10

Involuntary phase of swallowing (deglutition)

Answer 10

soft palate rises to close the passage to the nasal cavity and the epiglottis decompresses over the trachea

Question 11

How does peristalsis occur?

Answer 11

circular muscle contracts behind bolus and longitudinal muscle contracts in front of bolus

Question 12

Where are these 4 sphincters
Oesophageal
Pyloric
ileo-caecal
Odi

Answer 12

oesophageal = Between the oesophagus and cardia part of the stomach
pyloric = connects the stomach to the duodenum
ileo-caecal = small intestine to caecum
Odi = bile duct

Question 13

What is food mixed with in the stomach?

Answer 13

hydrochloric acid and gastric juices to create chyme

Question 14

How many muscle types in the stomach & name them

Answer 14

3

circular, longitudinal and oblique

Question 15

4 parts of the stomach

Answer 15

cardia, fundus, body and pylorus

Question 16

Functions of the stomach

Answer 16

storage area
mechanical and physical processing
Protective - hydrochloric acid kills bacteria

Question 17

Mechanical and chemical processing in the stomach

Answer 17

Mechanical: 3 layers of muscle. stomach folded into rugae to expand as it fills

Chemical: gastric juices (hydrochloric acid, lipases, intrinsic factor and mucus

Question 18

What is intrinsic factor?

Answer 18

helps with the absorption of vitamin B12

Vitamin B12 is a water soluble vitamin with an important role in the functioning of the brain, nervous system and blood

Question 19

What would happen if insulin was taken as a tablet?

Answer 19

Would have less of an affect because it would get broken down in the stomach by pepsin since it is a hormone and hormones are proteins

Question 20

What reflex regulates stomach emptying?

Answer 20

Enterogastric reflex

Question 21

Why does chyme need to be neutralised in the small intestine?

Answer 21

because the stomach has a pH of 2 and the small intestine has a pH of 7-8

Question 22

What are the 3 parts of the small intestine

Answer 22

Duodenum, jejunum and ileum

Question 23

Mechanical and chemical processing in the small intestine

Answer 23

Mechanical: peristalsis, segmentation

Chemical: microvilli secrete enzymes such as maltase, sucrase and peptidases. Other secretions from accessory organs also help break down complex molecules

Question 24

Villi and Microvilli

Answer 24

on the walls of the small intestine - majority of nutrients are absorbed

Create a larger surface area for absorption

highly vascular to maintain a diffusion gradient

Question 25

Absorption

Answer 25

nutrients are absorbed through epithelial cells in microvilli and enter the bloodstream via capillaries or the lymphatic system via lacteals

Question 26

Where are amino acids and glucose taken after they are absorbed

Answer 26

to the liver via the hepatic portal vein

Question 27

Where are fats absorbed

Answer 27

into lacteals to enter the lymphatic system. They eventually enter the bloodstream at the subclavian vein

Question 28

Order of segments in the large intestine

Answer 28

ascending colon, transverse colon, descending colon and sigmoid colon

Question 29

Functions of large intestine

Answer 29

absorption of water, ions and vitamins
formation of faeces

Question 30

What is faeces made of

Answer 30

water, inorganic salts, undigested food and epithelial cells

Question 31

Cause of diarrhea and constipation

Answer 31

Diarrhea = bacteria inside stomach increase the rate of peristalsis

Constipation = codeine slows peristalsis. Too much water absorbed

Question 32

Appendix

Answer 32

attached to the posteromedial surface of the caecum

little function in humans but is painful when inflammed

Question 33

Process of excretion

Answer 33

rectal walls stretch = activation of the parasympathetic nervous system = we can ignore signals until another mass enters the rectum

long rectal muscles contract = increased pressure = voluntary contraction of diapghram and accessory muscles = relaxation of internal anal sphincter

Question 34

Where is bile produced and what is it’s function

Answer 34

Liver

emulsified fats making them more water soluble

bile enters the duodenum when we are eating

When we are not eating the sphincter of Odi closes and bile backs up into the gall bladder

Question 35

Functions of the pancreas

Answer 35

Endocrine (directly into bloodstream) and Exocrine gland (into gland)
Insulin - beta cells
Glucagon - alpha cells

secretes enzymes such as amylases and lipases

produces sodium bicarbonate (reduces acidity of stomach contents)

Question 36

What are the following processes
deamination
transamination
protein synthesis

Answer 36

Deamination: removal of amino acids to enable the conversion into carbohydrates

Transamination: converting one amino acid to another

protein synthesis: making proteins from amino acids

Question 37

What is the livers role in lipid metabolism

Answer 37

fatty acids are oxidised to form ATP

liver is involved in the synthesis of lipoproteins, cholesterol and phospholipids and is responsible for breaking down cholesterol to form bile salts

Question 38

True or false
as the rectum fills, the rectal walls stretch and activate the sympathetic nervous system

Answer 38

False

Activates the parasympathetic nervous system