gastrointestinal tract

Question 1

what are the 8 parts of the gastrointestinal tract/system

Answer 1

oral cavity
oesophagus
small intestine
liver
pancreas
gall bladder
large intestine

Question 2

what is the total length of the GIT

Answer 2

6m

Question 3

due to what can increase the SA of the intestinal lumen to almost 200 square meters

Answer 3

villi

Question 4

what are the 5 things that make up the structure of the oesophagus

Answer 4

1. stratified squamous epithelium
2. muscular mucosa
   (1 and 2 together are simply considered as mucosa)
3. submucosa
4. circular muscle
5. longitudinal muscle

Question 5

what are the 3 pairs of salivary glands and where in the mouth are they found

Answer 5

1. sublingual (under the tongue)
2. parotid (overlying the cheek)
3. submandibular gland (close to jawline)

Question 6

why is saliva able to dissolve soluble food components

Answer 6

it is made of mostly water

Question 7

what found in saliva can aid in digesting starch

Answer 7

amylase

Question 8

how is the chewed food/bolus of food carried down into the stomach?

Answer 8

carried by the peristalsis (involuntary muscle movement) to stomach via cardiac sphincter (upper portion of stomach/lower oesophageal)

Question 9

what prevents food from falling into the lungs

Answer 9

epiglottis covers the trachea

Question 10

why is the oesophagus lined by squamous epithelium

Answer 10

to protect it from food which is abrasive

Question 11

what makes the oesophagus squamous lining resilient

Answer 11

larger surface area attachment and long periphery attaching it to its neighbours

Question 12

what role does the submucosa play when the squamous cells aren’t working well

Answer 12

• they are relatively loose with many elastic fibres so can swell (due to pressure) during passage of food
• they also contain small seromucous glands which aid lubrication

Question 13

why is the oesophagus muscle layer thick

Answer 13

it undergoes waves of muscular contractions (peristalsis) to move food towards the stomach

Question 14

what are the 3 sections of the stomach?

Answer 14

1. fundus (dome shaped section at top of stomach)
2. body ( main section that stored food till passing to small intestine)
3. pylorus ( part of stomach that connects to small intestine/duodenum)

Question 15

protein and fat are not acted on enzymatically

Question 16

what 2 food groups are acted on in the stomach

Answer 16

lipids and protein

Question 17

why is there mucosa in the folds/rugae of the stomach

Answer 17

to give stomach extra capacity when food distends it

Question 18

where can the gastric glands of the stomach be found and what do they do?

Answer 18

found in the epithelium (simple columnar) of stomach which extends to open into stomach lumen via gastric pits

they secrete gastric juice (HCL, pepsinogen etc)

Question 19

describe the 5 structural components of stomach

Answer 19

1. mucosa
2. submucosa
3. (inner) oblique
4. (inner) circular muscle
5. (outer) longitudinal muscle

Question 20

why does the stomach need an extra oblique layer compared to the oesophagus>

Answer 20

it provides strong musculature enabling the stomach to effectively churn food

Question 21

what are the 4 structural components of the small intestine/ ileum

Answer 21

1. villi
2. submucosa
3. circular muscle
4. longitudinal muscle

Question 22

what 3 additional structural components can be found within the small intestine

Answer 22

1. goblet cells
2. brunners glands
3. crypt/ intestinal glands

Question 23

what 3 things in the epithelium of the villi allow the digestion of lipids

Answer 23

pancreatic fluid
bile
enzymes

Question 24

what specifically does pancreatic fluid contain to allow the breakdown of lipids and what does it breakdown into

Answer 24

lipase
breakdown into monoglycerides

Question 25

how does bile acid aid in digestion of lipids

Answer 25

it acts as a detergent (emulsifies) lipid droplets down to 1micrometer diameter

Question 26

once the monoglycerides pass through the epithelial cell of villi, what do they resynthesises into and using what

Answer 26

smooth endoplasmic reticulum resynthesises it into triglycerides

Question 27

after triglycerides are resynthesises in the villi, what happens

Answer 27

- Golgi surrounds it with protein coat forming chylomicron - chylomicrons discharged via exocytosis into lymph vessels, lacteals draining the villi

Question 28

what proportion of ingested fats fail to breakdown and get digested hence released in feaces

Answer 28

1/3

Question 29

what is a zymogen

Answer 29

proteins that contain an inactive enzyme

Question 30

explain how proteins are further broken down in the duodenum

Answer 30

- further digested by 4 zymogens (produced by pancreas) - zymogens are activated in duodenum to form various endopeptidase - different endopeptidases cut at different places on peptide chain as they target different sequences

Question 31

what are the 4 different endopeptidases used to digest proteins

Answer 31

- trypsin - chymotrypsin - elastase - carboxypeptidase

Question 32

what also the short peptide chains to further digest into amino acids

Answer 32

exopeptidase

Question 33

where are exopeptidase found

Answer 33

in the membrane of the ileum epithelial cells

Question 34

explain how 3 types of exopeptidase form amino acids

Answer 34

- carboxypeptidase work on c-terminal end - aminopeptidases work on N-terminal end - dipeptidases cut dipeptides in half

Question 35

what transport mode is amino acids absorbed by

Answer 35

active transport via co-transport with sodium ions

Question 36

describe how further digestion of disaccharides occur in iileum

Answer 36

- in general, dissachridases convert disaccharides into their monosaccharide units - maltase hydrolyses maltose into glucose - lactase hydrolyses lactose into glucose and galactose - sucrase hydrolyses sucrose into glucose and fructose

Question 37

how do each monosaccharide get absorbed

Answer 37

- fructose simply diffuses into villi - glucose and galactose absorbed via active transport with co-trasport of sodium

Question 38

symbiotic (friendly) bacteria in ileum occur but less numerous than in colon

Question 39

what is the function of villi

Answer 39

maximise surface area for absorption of nutrients (mainly occurring in small intestine)

Question 40

what additional feature does the duodenum have compared with the proximal jejunum and ileum

Answer 40

burners glands

Question 41

what is the function of brunners glands and where is it found

Answer 41

- lies in submucosa deep to the muscular mucosae - secrete alkaline mucus which neutralises the acidic chyme passing down from the stomach

Question 42

what are paneth cells + function

Answer 42

- secretory cells in the crypt - can occur in duodenum and provide host defence against microbes

Question 43

what is the only difference between the jejunum and ileum

Answer 43

jejunum has no aggravated lymph nodes (Peyers patches)

Question 44

why are the villi in the ileum shorter than int he duodenum

Answer 44

most absorption happens here so faster

Question 45

what is the function of goblet cells in the mucosa

Answer 45

produce mucin for lubrication of intestinal contents and protection of epithelieum

Question 46

explain the role of the gallbladder and pancreas in digestion

Answer 46

- chyme enters duodenum - hormones secretin and cholecystokinin stimulates pancreas and gall bladder to discharge pancreatic fluid and bile into duodenum

Question 47

what is the role of liver in digestion

Answer 47

- detoxifies foreign compounds in foods and drugs - secretes bile - veins draining intestine lead to 2nd set of capillary beds in liver and here the liver removes many of the materials absorbed by intestine

Question 48

how do the liver and gall bladder work together in digestion

Answer 48

- bile released by the liver accumulates in the gallbladder

Question 49

how does bile aid in digestion

Answer 49

- contains salts derived from cholesterol - salts help emulsify fats

Question 50

what makes poo brown

Answer 50

- breakdown of haemoglobin from old RBC makes bile pigments which form brown colour

Question 51

how does the liver aid in digesting non-nutritive molecules

Answer 51

liver screens blood reaching it in the hepatic portal system (removes and detoxifies) so blood composition when leaving liver is close to normal

Question 52

how does the liver deal with excess amino acids

Answer 52

- removed and deaminated - amino group is converted to urea - residue enters pathway of cellular respiration and oxidised for energy

Question 53

glucose is removed from the blood in liver and converted into glycogen. other monosaccharides are removed and converted into glucose

Question 54

how is pancreatic fluid moved into the duodenum?

Answer 54

- pancreas consists of endocrine cells (islets of langerhand) and exocrine cells - their secretion drains into duodenum

Question 55

what 4 types of things is pancreatic fluid consisted of

Answer 55

- sodium bicarbonate (neutralise acid) - pancreatic amylase - lipase - 4 zymogens

Question 56

why does pancreatic fluid consist of inactive enzymes (zymogens)

Answer 56

protease enzymes are dangerous so synthesised by RER as inactive forms

Question 57

how/what are the 4 different zymogens activated

Answer 57

- trypsinogen activated to trypsin by enterokinase (secreted from duodenum epithelium) - trypsin activates chymotrysinogen to chymotrypsin - proelastase to elastase - procarbozypeptidase to carboxypeptidase

Question 58

what are the 2 main structures of large intestine

Answer 58

- circular muscle - longitudinal muscle

Question 59

what 2 additional structures does the large intestine/colon have

Answer 59

goblet cells lymphoid

Question 60

what does the residue from ileum consist of in the colon

Answer 60

- mainly water - non digested materials

Question 61

what is there a large population of in the colon

Answer 61

bacteria (mainly harmless)

Question 62

what can the intestinal flora/bacteria do

Answer 62

- capable of fermenting indigestible carbohydrates to short-chain fatty acids e.g acetate - acids formed can be energy source for host - they can also produce vitamin k, biotin, folic acid, thiamine, vitamin b12 (absorbed in colon)

Question 63

what 5 beneficial components can the bacteria in our colon produce

Answer 63

- folic acid - vitamin b12 - vitamin k - biotin - thiamine

Question 64

what causes diarrhoea

Answer 64

irritation of large intestine causing discharge of contents before water reabsorption

Question 65

what causes constipation

Answer 65

colon retains contents for too long, fecal matter dries out and compresses

Question 66

what is the main function of the colon

Answer 66

reabsorption of water

Question 67

what 2 types of cells does the mucose epithelium of the colon contain

Answer 67

1. absorptive cells 2. mucus-secreeting goblet cells

Question 68

absorptive cells decrease in number from proximal to distal while goblet cells increase in number

Question 69

what is particular about the structure of goblet cells in the colon

Answer 69

arranged in closely packed straight tubular glands/crypts which extend to muscular mucosa

Question 70

why does mucus because increasingly important as faeces pass along the colon

Answer 70

faeces become progressively dehydrated so mucus required to protect mucosa from trauma

Question 71

the anus has stratified squamous mucosa

Question 72

the appendix is located in which area of the GI tract

Answer 72

small intestine