Med Term

Roles of HCL:

-denatures protein -kills bacteria/parasites -erodes cementing b/w cells-food easier to digest -activates pepsinogen (convert it to pepsin)

Gastric glands produce 3 components of gastric juice:

1. mucous (mucous cells)- lubricates and protects cells lining stomach 2. HCL (parietal cells)-hydrogen and chloride ions 3. Pepsinogen (chief cells), inactive form of enzyme pepsin, protects cells of gastric glands

How is pepsin formed?

How is pepsin formed? Parietel cells secrete H+ and CL- (HCL) into the lumen of the stomach. Pepsinogen will be released by the chief cells. Next HCL converts pepsinogen into pepsin, pepsin then activates more pepsinogen-chain reaction, positive feedback (end product of a process promotes the formation of more end product.)

Where in the small intestine does most of the absorption take place?

Mostly in jejunum and ileum

what happens to protein in the stomach

When PH is low in the stomach (presence of HCL), proteins-----pepsin----peptides

hepatic portal vein

between intestines and heart, capillaries from large and small intestine converge into veins that lead into the hepatic portal vein which transports blood to the liver

HDL

• Made by liver • Transport cholesterol from tissues back to liver, cleans up!: cholesterol—bile • Can be increased by exercise, I drink a day • "good cholesterol" associated with decrease in the risk of cardiovascular disease.

When symbiotic digestion int he large intestine breaks down fiber (cellulose) it produces:

• odour and other gases • fatty acids-absorbed for energy (6-10% of daily energy) • Vitamin K (not in newborns)

large intestine role details ****

•Absorption of rest of water (1.5-2L day), minerals and vitamins •feces become more solid, move along colon by peristalsis •mucus production because of dryer feces •feces consist of: cellulose and prokaryotes that usually live in the colon •Bacteria breaks down cellulose (in some animals???) •some colon bacteria(ex. E-coli-not good in small intestine! Wash hands!) produce vitamins (B,K)-absorbed in bloodstream •feces stored in rectum until they can be eliminated •2 rectal sphincters (voluntary and involuntary) regulate opening of anus

Destination of leftover chylomicron after in the blood stream

1. moves to the liver where cholesterol is added to the triglyceride=VLDL-very low density lipoprotein (low protein content, high fat content) 2. Body removes TG via adiposal muscle cells (take fat for muscles) 9.Leftover VLDL receives a facelift- LDL-low density lipoprotein, delivers cholesterol to body cells, "bad cholesterol", associated with atherosclerosis (thickening of artery walls because of build up of cholesterol and tryglicerides), heart disease-heart attack, raises blood cholesterol

How are gastric juices not secreted all the time?

Gastric glands don't secrete acidic gastric juices all the time. Signal from brain stimulates your gastric glands, food arrives to stomach it stretches stomach walls and triggers release of hormone GASTRIN. When stomach contents too acidic, negative feedback mechanism stops production, the acid inhibits the release of gastrin.

by the time juices move out of___ , chemical digestion about complete, rest of small intestine _____ _____ and _____

duodenum, absorbs nutrients and water

autotrophs

organisms that get energy from the sun

heterotrophs

organisms that must eat other organisms for energy

3 sections of small intestine

1. Duodenum-1st 25cm, chyme from stomach mixes with digestive juices from pancreas, liver, gallbladder and glands cells of intestinal wall 2. Jejunum 3. Ileum

content of digestive (pancreatic) juices

1. alkaline fluid (NaHCO3-sodium bicarbonate), buffer that neutralizes acidity of chyme as it enters small intestine 2. digestive enzymes (hydrolytic)- amylase, lipase, trypsin (inactive trypsinogen), protease

Negative feedback.

A change in a variable triggers mechanism that reverses that change. Ex. When stomach is too acidic it causes gastrin to stop releasing, less gastrin in the blood, gastric glands secrete less gastric juices.

alimentary canal

A digestive tract with two openings-mouth and anus.

Large Intestine Major Role

Absorbs water from the alimentary canal and compacts feces

peristalsis

Alternating waves of contraction and relaxation of the smooth muscles lining the canal that propel food through the alimentary canal once food is swallowed.Outer layer: longitudinal, inner layer: circular (thicker forms sphincters)

cecum

At junction where large intestine meets small intestine there's a small pouch and it has bacteria that helps break down of plant materials. Huge in herbivores!!!

Acid reflux

Backflow of chyme up the esophagus. Usually opening between stomach and esophagus is closed but not in acid reflux.

Ruminants

Cattle, sheep and deer. 4 chamber stomach with symbiotic microbes. Regurgitates food, chews it some more- (break it down) exposing more plant fibers to its microbes for digestion. Cud is swallowed and moves to last chambers for digestion

Diarrhea!

If colon is irritated (ex. by viral or bacterial infection), colon less affective at reclaiming water, diarrhea may result

How are long fatty acids and monoglycerides absorbed?

Long fatty acids +monoglycerides: 1. Micelles (bile salts surround them ), via diffusion move into: 2. epithelial cells (villi cells of duodenum?): SER resynthesises them into triglyceride (but cytoplasm is water, how to make them soluble?) 3. Triglycerides+ protein: chylomicron (re-packaged). Go to: 4. Lymph (via exocytosis, inside the villi) 5. Thoracic vein (circulatory system-around heart) 6. Once in the blood stream Chylomicrons deliver triglycerides (that you ate) to body's cells

esophagus

Long tube that links pharynx to the stomach. Muscles at top of esophagus are under voluntary control but then peristalsis (involuntary contractions of smooth muscles in the rest of the esophagus) take over.

Herbivores VS carnivores and omnivores

Longer alimentary canal (digestive tracts) because it allows for more time for digestion and more surface area to absorb nutrients. Vegetation is more hard to digest than meat because they have plant cell walls. Cecum in herbivores holds cellulose-digesting microbes so herbivours have longer cecums

sphincter

Muscular ring like valves. Top of esophagus, between esophagus and stomach, between stomach and small intestine, between small intestine and large intestine, the anus (2! one voluntary one involuntary)

What prevents gastric juice form digesting away stomach lining?

Pepsinogen protects cells of gastric glands and mucus helps protect the stomach lining from pepsin and acid. Stomach lining (epithelium) gets replaced completely every 3 days! Gastrin, digestive hormone that stimulates the secretion of gastric juice, stops being released when stomach is too acidic.

Constipation!

Peristalsis moves the feces along too slowly, colon absorbs too much water, feces too compacted BC not enough fiber in diet!!

How do single-celled organisms digest? In humans which cells digest this way?

Phagocytosis-intracellular digestion, in humans only the white blood cells do this

Major role of liver in digestion

Produces bile which contains bile salts that break up fats into small droplets, easier to digest by enzymes

Villi

Small finger like projections in large circular folds of inner wall of small intestine. Increase surface area so there's more room for absorption

Gerd

Those who suffer acid reflux frequently and severely enough to harm the lining of the esophagus. Stop smoking, lose weight, avoid alcohol, eat small meals, refrain from lying down after eating, sleep with head of bed raised. . Antacids-reduce stomach acidity. Or surgery: strengthen lower esophageal sphincter.

Microvilli

Tiny projections on the epithelial cells on the surface of a villi

How does food not go in wrong hole?

Tongue pushes bolus of food into pharynx, triggering swallowing reflex. Larynx, moves up, tips epiglottis over opening of the larynx, preventing food from entering trachea. Esophageal sphincter relaxes, bolus enters the esophagus. Esophageal sphincter then contracts above the bolus, and epiglottis tips up again, reopening the breathing tube.

absorption and destination of water, monosaccharides, amino acids, vitamins and short fatty acids

Water: osmosis (small intestine receives 7-9 L/day and reabsorbs 5-7)----BLOOD Monosaccharides: active transport, mainly facilitated diffusion (not lipid soluble)---BLOOD Amino Acids: active transport (very water soluble)---BLOOD Short FA diffusion : BLOOD---LIVER Vitamins: fat soluble-diffusion, non-fat soluble-facilitated diffusion (active transport?)

Gastric ulcers

When gel like coat of mucous that protects the stomach wall from corrosive effect of digestive juice fails, open sores develop on the stomach wall. Symptom: gnawing pain in upper abdomen after eating (a few hours after). H. pylori, a bacteria (microbe) that survives the low pH of the stomach and burrows beneath stomach releasing harmful chemicals that cause loss of protective mucus and damage to cells lining the stomach. _____ occur when pepsin and hydrochloric acid destroy cells faster than cells can regenerate. Medication- antibiotics and bismuth-kills bacteria, promotes healing.

gastrovascular cavity

animals with a digestive compartment with a single opening-mouth. Digestion completed with food vacuoles Hydra, jelly fish.

Gastrin

digestive hormone produced in the stomach that stimulates the secretion of gastric juice. When stomach is too acidic it causes___ to stop releasing, less ___ in the blood,____ glands secrete less gastric juices.

positive feedback, example in digestive system

end product of a process promotes the formation of more end product. Pepsinogen----HCL---pepsin which in turn makes more pepsinogen

pancreas, 2 roles

endocrine: production of hormones for blood sugar regulation exocrine: digestive juices: 1.201.5L daily (on TOP of chyme) Pancreatic Juices: 1. alkaline fluid (NaHCO3-sodium bicarbonate), buffer that neutralizes acidity of chyme as it enters small intestine 2. digestive enzymes (hydrolytic)- amylase, lipase, trypsin (inactive trypsinogen), protease

stomach lining

epithelium

Appendix

extension of the cecum-mass of white blood cells that make a minor contribution to immunity. Prone to infection (appendicitis)-emergency surgery before it bursts!

Lacteal

lymphatic capillary that absorbs dietary fat (in form of chylomicron) in the villi of the small intestine. (blood vessels+lymph vessel)

Small intestine major role

major organ of chemical digestion and nutrient absorption

Intestinal gland produces enzymes (complete carb and protein digestion in brush border)

maltase, lactase (lactose---lactase---glucose and galactose), peptidase (dipeptide----peptidase---AA) sucrase

Rabbits

many nutrients produced by cellulose-digesting bacteria living in the large intestine and cecum, do not get absorbed because does not pass through small intestine (main site for nutrition absorption)-gets pooped out. Rabits recover these nutrients by eating some of their feces.

Stomach: major role

stores and breaks down food with acid and enzymes

Gallbladder

stores bile until it's needed by the small intestine.

•All four large molecules-carbohydrates, proteins, nucleic acids and fats-digested in small intestine

• Starch/polysaccharides-----pancreatic amylase------maltose (disaccharide G+G)-pancreas Maltose----maltase----glucose (monsaccharide) *() brush border enzymes-microvili Sucrose----sucrase----glucose and fructose ( Lactose---lactase----galactose and glucose brush • Polypeptides-----Tripsin, chymotripsin----smaller polypeptides (????)pancreas, duodenum Smaller polypeptides------peptidases----amino acids (brush border • DNA and RNA----nuclease------nucleotides (??? Nucleotides-----other enzymes-----nitrogenous bases, sugars and phosphates • Fat globules---bile salts---fat droplets (emulsified) liver,duodenum • Fat droplets---lipase----fatty acids and glycerol (pancreas) duodenum

Stomach: detailed answer

•absorption of substances (alcohol, aspirin etc) •production of HCL (hydrochloric acid)-( SER), pepsin (RER), alcohol dehydrogenase (RER)-women make less!, gastrin-hormone that stimulates secretion (RER)----- •Start chemical breakdown of proteins---enzyme pepsin---peptides (not amino acids yet!) •storage and liquefaction-bolus turns to chyme (acidic, nutrient rich soup) •mixing of stomach contents- churning action of stomach's muscular walls, made possible by 3rd muscle layer, muscles contract (hunger pangs-contractions of muscles when stomach is hungry) •gastric juices-break down cells in food, kills bacteria