Gastro-Intestinal Tract (GIT) 2

Question 1

Describe the bile produced by the liver - what it contains and its role

Answer 1

contains sodium & potassium salts - these emulsify lipids within fat to form globules which can be broken down further by pancreatic lipase

Question 2

Describe the path of bile from the liver

Answer 2

Bile drains through the right and left hepatic ducts into the common hepatic duct then passes through the common bile duct into the small intestine

Question 3

Describe what happens to the sphincter and bile between meals

Answer 3

the sphincter closes and bile is stored in the gall bladder as it cannot enter the intestine

Question 4

Describe the mucosa in the small intestine and its role and also describe the walls of the small intestine

Answer 4

the mucosa contains Brunner’s glands which secrete mucous to neutralise gastric acid, the walls of the SI have deep crevices lined with glandular epithelium - these form intestinal glands called Crypts of Lieberkuhn which secrete intestinal juice

Question 5

Describe what intestinal juice and pancreatic juice together does

Answer 5

this aids absorption of constituents of chyme

Question 6

Describe the role of epithelial cells in the small intestine and what its aided by

Answer 6

epithelial cells begin absorption and brush border enzymes aid this
Dextrinase, Maltase, Sucrase, Lactase = carbohydrates
Peptidase = proteins
Nucleotide digesting enzymes

Question 7

Describe the mucosa lining of the inner walls of the small intestine

Answer 7

covered with villi - finger-like projections - increases surface area for digestion, the villi house an arteriole/venule & lymphatic vessel - because the walls are so thin, the passage of nutrients (results of food breakdown) is possible, there are also goblet cells which secrete mucous aiding digestion

Question 8

Describe the role of Paneth Cells

Answer 8

these regulate the number of microbes - keeps the environment at its optimum

Question 9

Describe the micro-villi found on the walls of the SI

Answer 9

smaller than villi, increase surface area further to aid digestion, estimated 200 million per square mm

Question 10

Describe Plicae Circulares and its role

Answer 10

these are deep folds within the intestine, increase surface area for successful digestion, enables the chyme to spiral rather than travel in straight line

Question 11

Describe Segmentation

Answer 11

the movement of the intestine to bring the food contents in close contact with the mucosa, the food is sloshed back and forth approx. 12 times per minute in the duodenum and 8 times per minute in the ileum

Question 12

What does intestinal distention trigger

Answer 12

nerve impulses to stimulate motility

Question 13

What is peristalsis called in the small intestine and what is its role

Answer 13

migrating motility complex (MMC), moves food through GIT 1cm/1min, controlled by nerve impulses

Question 14

How long does it take food to move from the stomach to the end of the SI

Answer 14

120 minutes

Question 15

ABSORPTION - carbohydrates

Answer 15

all become monosaccharides for absorption, Fructose & Glucose = monosaccharides and are absorbed by diffusion or active transport through the lumen of the villi

Question 16

ABSORPTION - proteins

Answer 16

become amino acids and are absorbed by active transport through the lumen of the villi

Question 17

Monosaccharides and amino acids ….

Answer 17

enter the bloodstream and are transported to the liver

Question 18

ABSORPTION - fats

Answer 18

Tri/Di glycerides become monoglycerides by the action of bile, monoglycerides are converted to glycerol & fatty acids by lipase - these recombine with proteins to become phospholipids which are too large to pass into the bloodstream - enter the lymphatic system and drain eventually into the bloodstream through the subclavian vein - transported to the liver for further breakdown

Question 19

ABSORPTION - electrolytes

Answer 19

absorbed by sodium/potassium pumps, diffusion & secondary transport

Question 20

ABSORPTION - vitamins

Answer 20

mostly by simple diffusion but Vit B12 needs intrinsic factor and needs active transport for absorption

Question 21

ABSORPTION - water

Answer 21

via osmosis but fluctuates as it is dependent on the concentration of electrolyte balance within water, approx. 8.3 litres of water absorbed, 90% of absorption takes place in the small intestine

Question 22

Describe Alcohol Absorption - 4 points

Answer 22

can begin in the stomach, absorbed more quickly in SI because theres a larger surface area, presence of fat slows gastric emptying so blood alcohol level rises slower because it remains in the stomach longer so less enters the bloodstream

Question 23

Describe the role of gastric alcohol dehydrogenase enzyme and where its found

Answer 23

found in the stomach, breaks down alcohol into non-intoxicating elements

Question 24

Describe the basic features of the Large Intestine (LI)

Answer 24

1.5m length, 6.5cm diameter, commences at ileo-caecal valve and finishes at anal orifice, consists of caecum and appendix, ascending/transverse/descending/sigmoid colon, Rectum & Anal Column

Question 25

Describe the position of the caecum

Answer 25

hangs below the ileo-caecal valve

Question 26

Describe the appendix

Answer 26

small coiled tube, 8cm

Question 27

Describe the passage of food through the LI

Answer 27

ascends up the right side of the abdomen via the ascending colon & turns left under the liver at the hepatic flexure, then travels across to the left side of the abdomen via the transverse colon, then turns through the splenic flexure to travel down the left side of the abdomen via the descending colon, at the level of the iliac crest it travels towards the midline via the sigmoid colon, terminating at the 3rd sacral vertebrae where it becomes the rectum

Question 28

Describe the Rectum - 3 points

Answer 28

20cm long, has good blood supply, has internal & external muscular sphincter

Question 29

Describe the Mucosa lining in the walls of LI

Answer 29

no villi, no permanent folds but do have goblet cells which secrete mucus to assist passage through intestine

Question 30

Describe the Muscularis lining in the walls of LI

Answer 30

external, longitudinal fibres

internal, circular fibres

Question 31

Describe the Taeniae Coli lining in the walls of the LI

Answer 31

bands of muscle fibre which run the length of the LI and gather it into haustral folds during contraction

Question 32

Name the 4 functions of the LI

Answer 32

Haustral Churning
Peristalsis
Mass Peristalsis
Chemical Digestion

Question 33

Describe Haustral Churning in the LI

Answer 33

process movement of food contents from 1 haustra to the next

Question 34

Describe Peristalsis in the LI

Answer 34

12 contractions/min to move food along

Question 35

Describe Mass Peristalsis in the LI

Answer 35

move food from mid transverse colon to rectum in a strong peristaltic movement

Question 36

Describe Chemical Digestion in the LI

Answer 36

by bacterial action, breaks down any remaining carbohydrates and prepares waste products (faces) for elimination

Question 37

Describe Pressure Receptors in the Rectal Walls

Answer 37

recognise the need for expulsion although (fortunately) voluntary control of external sphincter which controls rate of release

Question 38

Prior to expulsion, the LI is responsible for …

Answer 38

absorption of remaining water - approx. 100mls along with electrolytes such as sodium