MCAT Biology - The Digestive System

Chapter 9

Intracellular Digestion

Oxidation of glucose and fatty acids for energy

Extracellular Digestion

The process by which nutrients are obtained from food

Sphincters

Circular smooth muscles around canal that contract to allow compartmilization of function

Digestions

Breakdown of food into ints constituent organic molecules

Mechanical Digestion

Physical breakdown of large food particles into smaller food particles, but does not involve breaking chemical bonds

Chemical Digestion

Enzymatic cleave of chemical bonds

Absorption

Transport of products of digestion from digestive tract into circulatory system for distribution to the body’s tissue and cells

Enteric Nervous System

Collection neurons that govern the function of gastrointestinal system

Pharynx

Shared pathway for food entring digestive system and air entering respiratory system

Peristalsis

Rhythmic contractions of the gut tube in order move material through system

ADH and aldesterone

trigger thirst, encouraging behavior of fluid consumption

Glucagon and ghrein

Feelings of hunger

Leptin and cholectstokini

feelings of satiety

Mastication

breaking up large food particles into smaller pieces using teeth tounge and lips

Salivary amylase

hydrolizes starch into smaller sylase

Lipases

catalyzes hydrolysis of lipids

Nasopharynx

behind nasal cavity

Oropharynx

Back of the mouth

Laryngopharynx

Above vocal cords

Epiglottis

Cartilaginous structure that folds down to cover the laryngeal inlet

Esophagus

Muscular tube connects pharynx to the stomach

Stomach

Highly muscular organ with a capacity of approximately two liters

Lesser curvature

The internal curvature of the stomach

Greater curvature

The external curvature of the stomach

Rugae

lining of the stomach

Gastric glands

Respond to signals fromt he vagus nerve, which is activated by brain in response to sight, taste and smell of food

Gastric juice

combination of the secretions from chief and parietal cells

Pepsinogen

Inactive zymogen form of pepsin

Pepsin

Digest proteins by cleaving peptide bonds near aromatic amino acids

Gastrin

induces the parietal cells in stomach to secrete more HCL and signals stomach to contract

Muscous Cells

Produce bicarbonate rich mucus that protects muscular walls from teh harshly acidic and proleokytic environment of stomach

Chief Cells

Secrete pepsinogen

Parietal Cells

Secrete hydrogen ions in stomach as Hydrochloric acid

Brush Border Enzyme

Present luminal surface of cells linging the duodenum and break down dimers and trimers of biomolecules into absorbable monomers

Bile

Is complex fluid composed of bile salts, pigments and cholestrol

Pancreatic Juices

Are a complex mix of several enzyme in a bicarbonate rich alkane solution

Pancreatic amylase

Breaks down large polysaccharides into small disaccharide and responsible for protein digestion

Pancreatic Lipase

Capable fo breaking down fats into free fatty acids and glycerol

Liver

Located in upper right quandrant of the abdomena dn contains two unique structure for communicating with digestive system

Bile Ducts

Connect liver with gall bladder and small intestine

Bilirubin

Byproduct of the breakdown hemoglobin

Jaundice

yellowing of skin

Gallbladder

Located beneath the liver and both stores and concentrates bile

Salivary amylase Site of production

Salivary glands

Salivary amylase Site of function

Mouth

Salivary amylase function

Hydrolyzes starch to maltose and dextrins

Pancreatic amylase site of production

pancrease

Pancreatic amylase site of function

Duodenum

Pancreatic amylase function

hydrolyzes starch to maltose and dextrins

Maltase site of production

Intestinal glands

Maltase site of function

Duodenum

Maltase function

Hydrolyzes mallose to two glucose molecules

Isomaltase site of production

Intestinal glands

Isomaltase site of function

duodenum

Isomaltase function

Hydrolyzes isomaltose into two glucose molecules

Sucrase site of production

intestinal glands

Sucrase site of function

Duodenum

Sucrase function

Hydrolyzes sucrose to glucose to fructose

Lactase site of production

intestinal gland

Lactase site of function

Duodenum

Lactase function

hydrolyzes lactose to glucose and glactose

Pepsin site of production

gastric gland

pepsin site of production

stomach

pepsin function

hydrolyzes specific peptide bonds, activated by HCl

trypsin site of production

pancreas

trypsin site of function

duodenum

trypsin function

hydrolyzes specific peptide bonds, converts chymotrypsinogen to chromotrypsin, activated by encidpeptidase

Chymotrypsin site of production

pancreas

Chymotrypsin site of function

duodenum

Cymotrypsin function

hydrolyzes specific peptide bonds activated by trypsin

procarboxy peptidases A and B site of production

pancreas cacinor cells

Pro carboxy peptidases A and B site of function

Duodenum

Pro carboxy peptidases A and B function

Hydrolyzes terminal peptide bond at carboxy end, activated by enteropeptidase

Aminopeptidase site of production

instenstinal glands

Aminopeptidase site of function

duodenum

Aminopeptidase funciton

Hydrolyzes terminal peptide bond at amino end

Dipeptidases site of production

intestinal gland

Dipeptidases site of function

duodenum

Dipeptidases function

Hydrolyzes pairs of amino acids

Enteropeptidase site of production

Intestinal gland

Enteropeptidase site of function

Dueodenum

Enteropeptidase Function

Convert trypsinogen to trypsin and procarboxy peptidases A and B to carboxypeptidases A and B

Bile Site of prodcution

Liver

Bile Site of function

Duodenum

Bile Function

Emulsifies fat

Lipase site of production

Pancreas

Lipase site of function

Duodenum

Lipase function

hydrolyzes lipids

Villi

Small finger like projection from epithelial linging

Lacteal

A lymphatic channel that takes up fats for transport into the lymphatic system

Transcellulary

across cell membrane

Paracellulary

squeezing between cells

Cecum

An outpoketing that accepts fluid exiting the small intestine through the ileocecal valve and is stie of attachment of the appendix

Anus

opening through which wastes are eliminated and consists of two sphincters external sphincter is under somatic control, the internal is under autonomic control.