It prepares food molecules for use in the body by the use of physical digestion and chemical digestion.

Alimentary - mouth/oral cavity, pharynx, esophagus, stomach, small intestines, large intestines, rectum

Accessory Organs - salivary glands, liver, gall bladder, pancreas, teeth, tongue

Mucus is secreted by the lining of the entire alimentary canal.

Function is for lubrication and protection.

Saliva lubricates food and starts the chemical digestion of carbohydrates.

Controlled by the nervous system.

Mastrication - teeth are used for mechanical digestion

Chemical digestion - Salivary amylase converts carbohydrates into dextrins(shorter chained molecules.

Has very little absorption abilities.

Voluntary Stage - bolus is forced to the back of the oral cavity and into the oropharynx by the movement of the tongue upwards and backwards against the palate.

Pharygeal Stage - Controlled by the medulla - respiration inhibited - larynx raises and glottis closes - epiglottis closes off trachea - pharyngeal muscle contract forcing bolus into esophagus

Esophageal stage - (per'-is-STAL-sis; stalsis = constriction) Controlled by the medulla -Circular smooth muscle layer above bolus contracts forcing it down - longitudinal smooth muscle layer below bolus contracts widening the esophagus to accept the bolus - previous contractions occur in waves=peristalsis - gastroesophageal sphinter opens and bolus enter stomach - gastroesophageal sphincter closes

Hydrochloric Acid (HCI) - produced by parietal cells, it protects against pathogens and breaks food into smaller pieces.

Pepsin - produced by chief cells, it is an enzyme involved with digestion

Cephalic Phase- thought, taste, smell or sight of food stimulates increase in cerebral cortex/hypothalamus which stimulates increase in medulla oblongata which stimulates increase in gastric glands and gastric mobility

Gastric Phase
1 - Distention of stomach and increase in PH stimulates gastric gland(pyloric) endocrine glands - gastrin - stimulates gastric glands and gastric motility
2 - distention of stomach and increase in PH stimulates gastric glands and gastric motility

Intestinal Phase - turns gastric glands off
1 - Ditention of duodenum/presence of fatty acids - glucose stimulates duodenal endocrine glands - gastric inhibitory peptide (GIP), secretetin and cholecystokinin (CCK) decrease gastric glands and gastric motility
2 - Enterogastric reflex: distention of duodenum/presence of fatty acids glucose stimulates medulla oblongata decrease gastric glands and gastric motility

1. HCI - breaks food into smaller pieces.

2. Pepsin - converts proteins into proteoses and peptones, smaller chained molecules.

3. Very little absorption since only small molecules can be absorbed, water and alcohol

1. Receptive relaxation

2. Tonic contractions

3. Peristalsis

4. Control of gastric motility

1. Receptive relaxation - gastric muscles relax as food enters the stomach.

2. Tonic contractions - contractions of the longitudinal smooth muscle layer - mixes the chyme, stomach contents.

3. Peristalsis - moves chyme through the stomach.

4. Control of gastric motility - See previous for control of secretion.

Acinar cells

Water, bicarbonate ion and digestive enzymes (trypsin, chymotrypsin, carboxypeptidase, pancreatic lipase, pancreatic nuclease and pancreatic amylase).

1. Sight, thought, taste, or smell of food stimulates medulla which stimulates pancreas.

2. Acids in duodenum stimulates duodenal endocrine glands, which stimulates hormones (secretin and CCK), which then stimulates pancreas.

Bile = Water, bile salts and bile pigments, (gets its greenish color from this).

1. Bile is produced continuously and stored in the gall bladder.

2. CCK, secretin, gastrin and parasympathetic n.s. causes contraction of the gall bladder and the release of bile into the duodenum.

Brunner's glands

Crypts of Lieberkuhn - produce two groups of enzymes erepsin and carbohdrases.

Control - mechanical/chemical stimulates small intestines which stimulates intestinal glands to produce erepsin and carbohdrases.

1. Dextrins converted to disaccharides by pancreatic amylase

2. Disaccharides converted to monosaccharides by carbohydrases

1. Proteoses/ peptones converted to dipeptides by trypsin, chymotrypsin and carboxypeptidase

2. dipeptides converted to amino acids by erepsin

1. Converted to emulsified fats (makes big blobs small blobs) by bile.

2. Emulsified fats converted to glycerol and fatty acids by pancreatic lipase.

Converted to nucleotides by pancreatic nuclease.

They are actively absorbed, (by active transport).

They are diffused into intestinal cells and combine to form fat which then diffuse out, become attached to proteins becoming chylomicron diffuse into lacteals - blood, (lymph capillaries).

Vitamins diffuse into the blood, not digested at all.

Cations are actively absorbed

Anions diffuse into blood

Water moves into blood by osmosis.

Segmenting

Pendular

peristalsis

gastroileal reflex

Segmenting movement - contractions of the circular muscle layer that segments and mixes the chyme.

Pendular movement - contractions of the longitudinal smooth muscle layer that moves and mixes the chyme.

Peristalsis - moves chyme through the intestines, like stomach and esophagus.

Gastroileal reflex - ileum contracts moving contents into the large intestines.

1. Sodium - is actively absorbed

2. Water - is absorbed by osmosis

3. Vitamins, K, B12, thiamin and riboflavin - produced by bacteria in the gut

Segmenting - has to move at just the right rate, to fast = diarrhea to slow = constipation

Tonic contractions

Peristalsis

Mass movement - strong peristaltic wave that moves feces into the rectum

Defecation - Rectum stretches as it fills, stimulates stretch receptors, peristalsis, contraction of rectal muscles and relaxation of internal sphinter, cerebral cortex, relaxation of external sphincter and contraction of diaphragm.