Digestive System - adv. med bio

oral cavity

entranceway for the food and where food is held for initial mechanical digestion

tongue

this muscular organ

1. positions the food for chewing

2. mixes food w/ saliva

3. pushes bolus of food down the pharynx during swallowing

teeth

responsible for the physical breakdown (mechanical digestion) of food to increase its surface area for digestion

salivary gland

produces saliva which contains

1. water to moisten and dissolve food

2. amylase to initiate carbohydrate digestion

3. mucins to lubricate food

4. bicarbonate ions to neutralize acidic food

soft palate

during swalloqing, this lifts to block the opening to the nasal passages to prevent food/liquid from entering

epiglottis

during swallowing, this lowers over the glottis (the opening to the trachea) to prevent food from entering the respirtory tract

pharynx

the passageway shared by both food and air (aka. throat)

esophagus

the muscular tube that carries the bolus of food from the pharynx to the stomach through involuntary contractions called peristalsis

cardiac sphincter

this regulate the entry of the bolus into the stomach and prevents the stomach contents from going back up the esophagus when the sphincter is closed

stomach

this temporarily stores food and secretes

1. hydrochloric acid to kill microorganisms

2. pepsin to initiate protein digestion

3. mucus and bicarbonate ions to protect the stomach lining from the harsh HCl and pepsin. the stomach secretes a hormone called gastrin to stimulate the release of the gastric juices that contain 1,2 and 3

pyloric sphincter

this regulates the release of the chyme (stomach contents) from the stomach into the first part of the small intestine (duodenum)

duodenum

first part of the small intestine where most of the chemical digestion occurs. with the help of secretions from accessory organs, lipids, proteins and carbs are digested. this secretes a hormone called secretin which causes the pancreas to release pancreatic juices. it also secretes cholecystokinin (CKK) which signals to the gall bladder to release bile as well as stimulates the release of pancreatic juices

liver

this organ produces bile to help physically break down lipids into smaller droplets call micelles to increase the surface area for the chemical digestions that is to follow. the bile stores in the gall bladder until needed

gall bladder

stores bile and contracts in response to the presence of CCK to release the bile.

bile duct

a tube that helps transport the bile from gall bladder to the duodenum

pancreas

this organ produces

1. bicarbonate ions to neutralize the acidic chyme in the duodenum (converting from pH 2 to 8) to prevent damage to the intestine

2. various enzymes to aid in the chemical breakdown of lipids (lipases), proteins (proteas like trypsin and erepsin) and carbohydrates (more amylase and various diaccharidases)

jejunum

the second part of the small intestines where some of the digestion finishes off and the absorption of digested nutrient begin. contains finger-like projections called villi and microvilli to increase the surface area of the intestinal lining to increase the rate of absorption.

ileum

the third part of the small intestines where the absorption of nutrient continues and is completes. contains finger-like projections called villi and microvilli to increase the surface area of the intestinal lining to increase the rate of absorption

appendix

a vestigial structure that no longer players a vital role in humans. it can often get infected and inflamed causing a condition called appendicitis. also has beneficial bacteria

cecum

the first part of the large intestine

large intestine

responsible for

1. storing food waste

2. reabsorbing water from food waste

3. housing a large population of symbiotic gut flora which aids in proper digestive function (helps create bulk, creates B and K vitamins from food waste which can be absorbed by this). these are broken up into several sections in this order: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum

rectum

the last part of the large intestine which is responsible for storing feces until a bowel movement voids the feces. it contains stretch receptors that activate when there is enough volume in this which stimulates the urge to void

anus

a sphincter that regulated the release of feces from the rectum to the outside.