6.1 & D.2 ( digestion and absorption)

chylomicrons

lipoprotein particle used to transport fats (from intestines to parts of body), made of triglycerides, cholesterol and proteins

mouth/oral cavity

chews and mixes food with saliva, starts starch digestion

esophagus

moves the food mixture (bolus) down to stomach by peristalsis

peristalsis

muscle contractions to move food down esophagus

stomach

food is churned with acid to form chyme, stomach acid kills bacteria and starts protein digestion

small intestine

where most absorption happens, 3 parts: duodenum, jejunum, ileum

pancreas

releases hormones into blood + digestive enzymes into small intestine (secretes amylase, lipase, protease)

liver

secretes bile into stomach

gall bladder

stores bile

large intestine

reabsorbs water, vitamin k+b (made by the bacteria that lives here), feces is formed (sent to rectum), anaerobic bacteria ferments undigested polysaccharides to produce energy

exocrine glands

produce and secrete substances via a duct onto a epithelial surface

nervous control of digestion

vagus nerve to medulla: sight + smell of food secrete gastric juice for ingestion / food entering stomach cause peptide detection to produce gastrin hormone (in gastric pits)

hormonal control of digestion

gastrin is secreted into bloodstream, secretin + CCK stimulate pancreas + liver to release digestive juices

stomach ulcer

inflamed and damaged areas in stomach wall, symptoms include stomach pain, heartburn, nausea, blood in stool

stomach cancer

growth of tumors in stomach wall (has strong correlation to baterium h.pylori)

H. Pylori

bacterium that can survive acidic conditions of stomach, penetrates mucus lining

proton pump inhibitors

low ph of stomach is maintained by proton pumps in gastric pits, PPI are drugs that irreversibly bind to them stopping H+ secretion

villi

finger like projections in small intestine that increases surface area

microvilli

hair like projections attached to villi, increase SA

tight junctions (part of small intestine)

create impermeable barriers between plasma membranes and adjacent cells, keep digestive fluids separated from tissues (maintain conc. gradient to ensure one-way mvmt)

lacteals

part of lymphatic system, run up middle of villi, allow products of lipid digestion to be absorbed

features of small intestine

villi, tight junctions, lots of mitochondria and capillaries, mb proteins and pinocytotic vesicles

absorption

process where small molecules and nutrients pass into blood vessels in wall of intestine

assimilation

process where molecules are used to build up larger molecules that become part of structure of body/tissue

lumen

center of small intestine that food bolus pass through

epithelial layer

inner tissue layer in contact with lumen

mucosa

in between epithelial cells near lumen

serosa

outside small intestine

dietary fibre

indigestible part of food that reduces constipation, hemorrhoids, butt cancers, lower blood cholesterol

egestion

eliminating materials that are not absorbed by the small and large intestines as feces

sub-mucosa

tissue layer that has blood and lymph vessels

saliva

has amylase and enzymes in it

duodenum

1st part of small intestine, stomach acid neutralized for enzymes to function

ileum

last section of small intestine, digestion is completed and products are absorbed (to the bloodstream)

amylase

breaks down starch (into maltose → glucose)

lipase

breaks down lipids (into fatty acids)

protease

breaks down proteins (to smaller polypeptides → aas)

bile

NOT A ENZYME, breaks large lipids into smaller globules to emulsify lipids

examples of exocrine glands

surface of body - sweat glands & lumen of digestive tract

epithelial surface

outermost layer of cells that covers body, line internal organs, blood vessels, and cavities. Provides protection, absorption, and secretion.

stomach/gastric glands

gastric juices (hcl and protease) to break down protein

pancreatic glands

pancreatic juices (enzymes) and bicarbonate to break down food and neutralise stomach acid

gastrin

hormone that increases hcl secretion into stomach (made in g cells found in stomach, small intestine, pancreas) stimulated by physical presence of food

secretin

hormone that neutralises pH in small intestine and does osmoregulation through kidney

cholecystokinin (CCK)

releases pancreatic juice and bile (hunger suppressor)

somatostatin

inhibitory hormone that stops release of gastrin, secretin, cck

ingestion

eating food

digestion

chemical breakdown of food

absorption

passage of smaller molecules from digestive system into bloodstream/ lymphatic system

medulla oblongata control in digestive system

hungry/eating: sends message to start secreting gastric juice. when full/enough food: stomach expands and increase production to breakdown food

pyloric sphincter valve

open and releases food from stomach into small intestine, secretes hormone that stops gastric juice production

HCl

for food: denatures proteins so it becomes susceptible to digestive enzymes. activates pepsinogen (breaks proteins down) and kills pathogens

feces

what we cant absorb, made of cellulose(fiber), bile and bacteriam

dialysis tubing (visking)

partially permeable cellulose tubing with microscopic pores that separates smaller molecules from larger ones in a solution by selective diffusion

path of food (super simple)

food digested → absorbed into lumen → capillaries (sugar, a.a.s) or lacteals (fats)

epithelial cells

in villi take end products (ex. bases, phosphates, glucose)

goblet cell

makes mucus

how to treat stomach ulcers

antibiotics: amoxicillin( prevents cell wall making), clarithromycin (prevents the growth of bacterium) or PPIs (stop stomach acidification

cholera

bacterial pathogen that infects intestines, releases a toxin that binds to epithelial cells

symptoms of cholera

dehydration, diarrhea, and death if not rehydrated