The Alimentary Canal

- the one way passageway for food / nutrients / waste

Human Alimentary Canal

• Mouth

• Pharynx

• Esophagus

• Stomach

• Small intestine

• Large intestine

Mouth

• True digestive organ

• physical & chemical digestion

• Salivary Amylase breaks carbohydrates into disaccharides/maltose

• contains teeth, tongue, soft & hard palate to help with physical digestion

• food is ingested

Salivary Glands

• Accessory Organs

• produce salivary amylase– sublingual– submandibular– parotids

Pharynxaka. The throat

• True digestive organ

• no physical or chemical digestion occurs here

• hooks in with the respiratory system

Esophagus

• True digestive organ

• no physical or chemical digestion occurs here

• food considered a BOLUS - wet ball of chewed food

• PERISTALSIS starts here - wavelike contractions of the tube that moves the foodstuff along the alimentary canal

Stomach

• Very muscular organ that participates in both physical & chemical digestion

• true digestive organ• lined with thick protective

mucous• the enzyme pepsinogen

activates in the acid conditions in the stomach and becomes pepsin

• pepsin digests the proteins into groups of 2 amino acids

• cardiac sphincter valve is at the top and the pyloric valve is between the stomach & small intestine

• the bolus is now considered chyme

Small Intestine

• True digestive organ

• chemical digestion is completed here

• contains 3 main portions– duodenum first 10 cm of small intestine– jejunum next 2 ½ meters– ileum last 4 meters

•the role of the small intestine is threefold

1. Finish digestion2. Absorb nutrients3. Storage

•contains villi for absorption of nutrients

Small IntestineEnzyme Action

• Common bile duct hooks into duodenum

• this hooks up to the pancreas and gallbladder

• pancreatic juice & bile is secreted is secreted through this

• BILE & bile salts- emulsifies the fat - breaks into smaller droplets

• Pancreatic Juice contains:– sodium bicarbonate / to neutralize the acid

from the stomach– lipase / breaks fats into fatty acids & glycerol– trypsinogen in changed into trypsin in the si.

Environment and digests the dipeptides into single amino acids

– pancreatic amylase finishes carbohydrate digestion by breaking disaccharides into monosacharides

Villi• Increases the surface area in the small intestine for the maximum nutrient absorption

• monosaccharides & amino acids are diffused into the capillaries bloodstream

• fatty acids & glycerol are absorbed by the lacteal which hooks into the lymphatic system

Pancreas • Accessory digestive organ

• produces pancreatic juice which contains pancreatic amylase, sodium bicarbonate, trypsinogen and lipase

• located under the stomach

• LIVER

– produces bile which breaks up the larger fats

• GALLBLADDER

– stores the bile until needed

Large Intestine• True digestive organ, but digestion is all done by

now!!!

• The function is to absorb water & minerals

• at the junction of the

small & large intestine

is the appendix

• there are 5 portions of the large intestine

– ascending colon– transverse colon– descending colon– sigmoid colon– rectum which ends in the anal sphincter

methane in is a normal bi-product andin combination with e. coli bacteria produceflatulence

• At this point the waste products are referred to as feces

• CONSTIPATION - waste sits in large intestine too long and the stool becomes too hard and is difficult to evacuate

• DIARRHEA - waste does not sit in the large intestine long enough and not enough water is absorbed producing a watery stool

Hormones of the Digestive System

• GASTRIN -– cells of the stomach

secrete into bloodstream

– triggers cells of stomach to secrete hydrochloric acid so pepsinogen converts to pepsin

• SECRETIN -– when food enters the

small intestine– secreted by the cells

of si. Into the bloodstream

– triggers pancreas to make pancreatic juice