22. Mechanical and Chemical Digestion

Question 1

what are the four steps for food processing?

Answer 1

ingestion - the act pf eatomg

digestion - process of breaking down food into molecules small enouigh to absorb

absorbtion - uptake of nutrients by body cells

elimination - occurs as undigested material passes out of the digestinve compartment

Question 2

what is intracelluar digestioin?

Answer 2

food particles that are englufed via endocytosis and digested within food vacuoles

Question 3

what is extracelluar digestion?

Answer 3

breakdown of food particles outside of cells. requires a complex body plan (mammals)

Question 4

what are the four segments of the GI and what are two parts of each one

Answer 4

headgut - mouth and pharynx

foregut - oesogphagus and stomach

midgut - intestine

hindgut - colon, caecum and rectum

Question 5

what is the general structure of the GI tract? three points

Answer 5

mucousa

submucousa

muscularis layer

study image

Question 6

what is the structure and function of the mucousa in the GI tract? three points

Answer 6

stucture - single layer of epithelial cells lining the gut

functions - they are mostly secretory and abobitve
have underlying connective tissue which has immune cells

Question 8

what is the stucuture and name two thing that submucousa can be?

Answer 8

submucouasa is the connective tissue lying underneath a mucous membrane.

can be blood and lymph vessels or nerves

Question 9

what is the stucture and function of the muscularis layer?

Answer 9

structure - a thin muscle layer in the GI

propells nutrients unidirectionally from the lumen to the submucousa

Question 10

what is peristalis movement in the GI tract?

Answer 10

the wave-like movement including the contraction and relaxation within the GI tract to push the contents forward

Question 11

what are the two types of movement in the GI tract and what do they do?

Answer 11

peristalis - moving contents forward

segmentation - responsible for mixing

Question 12

what does digestion depend on?

Answer 12

hydrolytic enymes to break down large molecules

Question 13

what are the three types of digestive enymes?

Answer 13

intraluminal

membrane - associated

intracelluar

Question 14

describe the digestion of the headgut

Answer 14

chew into smaller pieces to increase durface area of food

saliva acts as chemical digetion and a buffer

salivary amylase - intiates breakfdown of glucose

tounge tastes food

oesophgus takes food from the pharyx and down to the stomcah via peristalis

Question 15

what is the structure and funciton of the stomach? Foregut.

name the four gastric juices secreted as well

Answer 15

its elastic - to store and mix food

secretes gastic juice including hydrochloric acid, pepsinogen, mucus and intrinsic factor (absorbtion of vitamin B12)

Question 16

what causes pepsinogen to go from an inactive zymogen to the active enyme?

Answer 16

it has a masking sequence on the pepsinogen molecule but the low pH of the stomach activated the pepsinogen

Question 17

how does the stomach protect itself from autodigestion of the HCL? two points

Answer 17

keeps pepsinogen seperatley from HCL (HCL stimulates pepsinogen to be in the active form, pepsin breaks down proteins and the stomach is protein)

stomach is lined with a layer of mucous from the mucous neck cells

Question 18

what is the function of the small intestine?

Answer 18

its the major site of digestion and absorbtion (note - the stomach does not absorb nutrients)

Question 20

how does the stomach pass on its conents to the small intestine?

Answer 20

small amounts of chyme is released into the small intestine mixed with gastic juices. the pancrease escretes bicarbonate to neutralise the chyme from the stomach

Question 21

what is the order of pancreatic proteases?

Answer 21

trypsin –> trypsinogen

procarboxypeptidase –> carboxypeptidase

chymotrypisnogen –> chymostrypisin

trypsin also stimulates carboxypeptidase and chymotrypsin

results in the hydrolysis of peptides

Question 22

what is the function of bile located in the gall bladder?

Answer 22

helps with the digestion of fats into fatty acids

Question 23

what is the process of fat digestion? 5 steps

Answer 23

fat is consumed in a meal

bile is released from the ggall bladder

bile + fat create milecelles

pancreatic lipase produce fatty acids and monoglycerides

absorbtion of fatty acids and monoglyrides to form triglycerides

Question 24

what is the function of the large intestine (colon)

Answer 24

to reabsorb water to be secreted back into the GI organs becasue lots of water is used in them.

fibre is broken down in the colon