L21 - gi system: structure & function

Question 1

what is the gastrointestinal system?

Answer 1

network of organs and specialised cells that allows food to be converted to energy and nutrients needed for life

Question 2

what does the gi tract consist of?

Answer 2

1. mouth
2. oesophagus
3. stomach
4. small intestine
5. large intestine
6. rectum
7. anus

Question 3

what does the gi system consist of?

Question 4

accessory organs - help function of gi system but not apart of it

Answer 4

• salivary organs
• liver
• gallbladder
• pancreas

Question 5

mesentery

Answer 5

• membranes tissue in stomach
• surrounds organs in go tract
• holds intestines in place
• provides blood vessels & lymphatics

Question 6

what does mouth in gi system consist of?

Answer 6

• teeth
• tongue
• mucous membranes

Question 7

how does mouth play part in eating?

Answer 7

• main function is to chew
• food passed to pharynx and epiglottis
• prevents food travelling to lungs

Question 8

bolus in oesophagus

Answer 8

• tube like structure
• involuntary movement of food bolus
• transports bolus to stomach

Question 9

stomach

Answer 9

• mixing
• muscular organ
• protein digestion
• HCl, pepsin
• fat emulsion

Question 10

3 parts of stomach wall

Answer 10

1. mucosa = mucus layer (top)
2. submucosa = glands and blood vessels
3. muscularis = smooth muscle

Question 11

cells present in stomach wall

Answer 11

1. mucous neck cell
2. parietal cell
3. enterochromaffin like cell
4. chief cells
5. d cells
6. g cells

Question 12

mucous neck cells in stomach wall

Answer 12

produce mucus and bicarbonate

Question 13

parietal cells in stomach wall

Answer 13

produces gastric acid and intrinsic factor

Question 14

enterochromaffin like cells

Answer 14

involved in enteric nervous system

Question 15

chief cells

Answer 15

produce enzymes (pepsin, gastric lipase)

Question 16

d cells in stomach wall

Answer 16

produce peptide hormone somatostatin to inhibit acid

Question 17

g cells

Answer 17

produce gastrin to stimulate acid

Question 18

small intestine structure

Answer 18

• longest part of gi tract
• main sight of absorption
• 3 sections (duodenum, jejunum, illeum)

Question 19

what does the SI do?

Answer 19

• site of breakdown of carbs, proteins, fats
• primary site of absorption

Question 20

the villi in the SI

Answer 20

• increase SA
• allow for better absorption

Question 21

crypts of lieberkuhn in SI (glands)

Answer 21

• paneth cells play role in defence and produce antimicrobial enzymes
• stem cells for regeneration
• goblet cells for mucus

Question 22

what is the large intestine for?

Answer 22

• water and ion conservation
• bulk movement of faeces
• storage
• defaection

Question 23

salivary glands

Answer 23

• lubrication via mucus
• protection
• digestion (amylase & lipase)

Question 24

liver

Answer 24

• bile production
• excretion

Question 25

gallbladders

Answer 25

• concentrating reservoir for bile (bile emulsifies fats)
• bile contains bilirubin (used to make hb)
• delivers bile to duodenum (SI) in response to meals

Question 26

pancreas

Answer 26

• makes enzymes to digest proteins, fats, carbs
• makes hormones insulin + glucagon

Question 27

6 functions of GI system

Answer 27

1. ingestion
2. secretion
3. movement
4. digestion
5. absorption
6. excretion

Question 28

what is ingestion?

Answer 28

process of eating food / having a drink through mouth

Question 29

what is secretion?

Answer 29

release of substances that contribute to digestion

Question 30

movement in the gi system

Answer 30

1. segmentation
2. peristalsis

Question 31

segmentation

Answer 31

contraction of circular muscles in gi tract (the one that’s really circular) (forwards backwards movement)

Question 32

peristalsis

Answer 32

wave like movement. main way

Question 33

what is digestion?

Answer 33

breakdown of food into smaller components that can be absorbed into the bloodstream

Question 34

mechanical digestion

Answer 34

physically breaking food with mouth / stomach movements

• mastication
• peristalsis
• gastric acids

Question 35

chemical digestion

Answer 35

enzymes breakdown food
- fats to fatty acids / monoglycerides
- nucleic acids to nucleotides
- polysaccharides / carbs to monosaccs
- proteins to a.a
- these enzymes are usually secreted by accessory organs

Question 36

what is absorption?

Answer 36

process through which nutrients, water, electrolytes enter blood

Question 37

what is excretion?

Answer 37

metabolic waste eliminated from body

Question 38

immune function

Answer 38

• first line of defence against pathogens
• diverse microbiome contributes to immune regulation
• microbiome prevents overgrowth of bad bacteria
• cells secrete mucus and antimicrobial peptides
• gut resident immune cells

Question 39

what is the sphincter?

Answer 39

muscular ring that prevents stomach juices from going back into the oesophagus

Question 40

stomach acid

Answer 40

HCl, allows pepsin to work best & kills bacteria

Question 41

chyme

Answer 41

thin watery material left behind when digestion is complete