the digestive system

Question 1

what is the fistula

Answer 1

an abnormal hole between the stomach and the torso.

Question 2

what are the functions of digestive system

Answer 2

-secretion
-motility: mixing and propulsion resulting from contractions and relaxation of muscle fibres
-digestion
-absorption
-protective

Question 3

what is digestion

Answer 3

breaking down our food into absorbative forms.

Question 4

what are the organic compounds that we digest

Answer 4

carbohydrate, proteins lipids and some nucleic acids

Question 5

what do the three main groups of food we eat turn into

Answer 5

carbohydrates - monosaccharides
proteins - amino acids
lipids (triglycerides) - fatty acids

Question 6

what is the digestive system composed of

Answer 6

(main organs) = oral cavity, oesophagus, stomach, small and large intestine
(accessory organs) = teeth, tongue, salivary glands, liver, gallbladder and pancreas

Question 7

how many layers does the GI tract have

Answer 7

inner to outside =
lumen: opens up to the external environment. its a scientific name for space and is what our food particles goes to
mucosa: largely epithelial tissue. creates barrier from outside and inside. first layer is epithelium, and the last layer is musucularis mucosae - creates folds to increase surface area for increased absorption, secretion etc
submucosa: blood vessel nerves, nutrients absorbed can travel to the rest of the body
muscularis externae: has two muscles responsible for prostatic contractions to push food down the digestive tract
- serosa: allos for gliding movement between digestive tract and other organs.

Question 8

explain the oral cavity

Answer 8

contains teeth, tongue and salivary glands.
secretion of saliva
protection through antimicrobial properties
digestion ( physical through mastication or chewing) and chemical through amylase breaking down starch to maltose.

Question 9

what is being secreted in the oral cavity and what is it made of

Answer 9

saliva is being secreted by salivary glands which is mostly water and 1% salt and proteins. it is to help lubricate food.
saliva also has antimicrobial properties like lysozyme to break down bacterial cell walls

Question 10

bolus

Answer 10

combination of chemical and physical digestion that forms bolus- food

Question 11

what is the role of oesophagus

Answer 11

made of skeletal muscles, then mixed and then smooth muscles. this allows for muscular contractions

Question 12

what is peristalsis

Answer 12

continuous waves of contraction and relaxation of muscles. this is moving the bolus to the stomach

Question 13

explain the properties of the stomach

Answer 13

• pylorus (biggest muscle in the stomach) . it starts to narrow down to the vascular valves- prevents backflow to the mouth
• musularis: three layers rather than two to churn the food to turn the bolus into chine
• rugae- folds of the mucosa. it extends when you eat. increases surface area for more contact between the bolus and the gastric juices to turn it into chine.

Question 14

explain the mechanical digestion and motility properties of the stomach

Answer 14

1. propulsion: you push food from top of the stomach to the pylorus. 1/10 of the chyme gets pushed through from the stomach to the intestine
2. retopulsion: rest os chyme gets picked back into the middle of the stomach where there is more chemical and mechanical digestion

Question 15

why do we need propulsion to happen int eh stomach and to not push all the chine to the intestine straight away

Answer 15

acidic and hypertonic

Question 16

explain the chemical digestion involved in stomach

Answer 16

the mucosa extends toward the submucosa to clumps of specialised secretory cells called gastric glands, they are specialised cells that produce different secretions.

Question 17

what are the components of gastric juice

Answer 17

Gastrin: hormone that stimulates secretion of HCI and pepsinogen.
pepsinogen: activated to pepsin when it makes HCI
pepsin: chemically digests proteins into peptides in the stomach
HCI: denatures proteins, converts pepsinogen to pepsin, snd kills microbes
bicarbonate rick mucus: protects stomach wall from protein digestion and corrosion from HCI
intrinsic factor: needed fro transportation and absorption of vitamin B12 in small intestine

Question 18

why don’t we just have pepsin

Answer 18

they are very acidic and will degrade the proteins in the stomach

Question 19

what is the anatomy and importance of small intestine

Answer 19

has specialised folds called villi- extension of mucosa into the lumen. they are fingerlike projections that go into the lumen. this is different from stomach where th mucosa invagenates within itself. it also has microvilli which are hair like projections of enterocytes -absorptive cells. all together the microvilli form a brush border. embedded in the walls are enzymes which break down compounds.

Question 20

where in the small intestine does chemical digestion occur

Answer 20

duodenum

Question 21

where does most enzymes in the small intestine come from

Answer 21

pancreas

Question 22

how does the pancreas release enzyme

Answer 22

endocrine cells release insulin and glucagon while the exocrine cels secrete pancreatic juice- water, bicarbonate ions (neutralises HCI from stomach), amylase - break down starch into maltose , lipase (break down triglycerides into fatty acids and glycerol or monoglycerides )

Question 23

whats the role of the liver in digestion in terms of bilirubin

Answer 23

it secretes bile- have bile salts that emulsifies fats, facilitates absorption of fat and cholesterol. it also has bilirubin which is a byproduct of red blood cells. they go into bile. microbes further break it down and secrete it in faeces.

Question 24

explain the motility role in small intestine

Answer 24

there is segmentation that occurs which means periodic sections of contractions to prevent chyme from moving down the track and maximise contact between chyme and intestinal walls to obtain maximum absorption. occurs in jejunum

Question 25

what is the top, middle and bottom part of the small intestine

Answer 25

jeodenum- top jejunum- middle ileum- bottom

Question 26

what is absorbed in jejunum

Answer 26

carbohydrates, protein, electrolytes, water and minerals. doesn't do digestion.

Question 27

where is 90% of the water absorbed

Answer 27

small intestine

Question 28

what is absorbed in ileum

Answer 28

hydrophobic components like fatty acids. because chyme is hydrophilic, these hydrophobic components usually just float on top of it.

Question 29

since hydrophobic components just sit on top of the chyme, what does the body do to mix them and what is this called

Answer 29

emulsification through biles salts. you form micelles and carry them to walls of the small intestines where the enterocytes are (absorptive cells).

Question 29

if there is not enough biles, what happens to the lipid molecules

Answer 29

there is not enough biles salts and you cannot form micelles so the lipids would float in the chyme and it gets eliminated through faeces

Question 30

explain the role of large intestine in digestion and absorption

Answer 30

there is some chemical digestion- produced by enzymes in the microbiome through fermentation and break down of short chain fatty acids. the large intestine absorbs the rest of the water and electrolytes. you also absorb the vitamins produced by the microbiome.

Question 31

what is the role of large intestines in absorption

Answer 31

the large intestine absorbs the rest of the water and electrolytes. you also absorb the vitamins produced by the microbiome.

Question 32

what is the role of large intestine in motility

Answer 32

haustral contractions localise chyme that occur every 30 minutes to increase water and electrolyte absorption

Question 33

what is the role of large intestine in elimination

Answer 33

peristalsis but much slower to expel faeces

Question 34

what does the stomach digest mostly

Answer 34

proteins through pepsin into peptides.

Question 35

why is there no absorption of water in stomach

Answer 35

there is no absorption in water because of mucosal lining and no aquaporins and because cyme is hypertonic.

Question 36

explain what happens in each part of small intestine

Answer 36

duodenum: chemical digestion from amylase breaking starch into maltose. lipase breaking down fatty triglycerides into fatty acids and glycerol/monoglycerides. jejunum: no digestion but absorption of carbs, peptides, amino acids, water 90% and electrolytes 80%. ileum: absorption of lipid products

Question 37

what is lysozyme

Answer 37

digestive enzyme that