Digestive System

Main Functions of the Digestive System

•Ingest (take in food)

•Digest (breaks down food, both mechanically & chemically)

•Absorb (nutrient molecules)

•Defecate (eliminates indigestible remains)

Two Main Groups of Organs in Digestive System

Alimentary Canal (“The Tube”)Mouth

Pharynx

Esophagus

Stomach

Small intestine

Large intestine

Rectum

Anus

Accessory Digestive Organs (helps “The Tube” with digestion)

Salivary glands

Teeth

Tongue

Gall bladder

Pancreas

Liver

The Mouth

• Mechanical digestion occurs here (mastication)

• Salivary amylase is an enzyme in the saliva that breaks down starches into sugars. This is what starts the digestive process. Amylase is also made in the pancreas

• Swallowing pushes the food bolus down esophagus

Esophagus

• Long tube that pushes food from mouth into stomach using peristalsis

• Cardioesophageal sphincter allows food to go from esophagus into stomach

Stomach• “C shaped organ”, approx. 10” long• Can hold 1 gallon of food• Folds in stomach (rugae) help with further mechanical digestion

• Stomach secretes gastric juices which contain digestive enzymes that are highly acidic

• Stomach itself is protected by a mucus layer• Food is broken down into a creamy, liquidy substance (chyme)

• Protein digestion occurs here• Sphincter at bottom (pyloric sphincter)only allows small amounts of chymeto enter small intestine

Small Intestine• Coiled muscular tube, that is 6-13 feet long• Chemical digestion of fats, proteins, and carbs occur here with help of specific enzymes released from accessory organs (pancreas & liver)

• Absorption of small molecules (glucose, amino acids, etc.) occurs here through microvilli

• Microvilli are tiny projections which increase surface area allowing for more absorption

• The small intestine is made up of the duodenum, jejunum, and the ileum.

Microvilli

Small intestine

F.Y.I

• The duodenum is the first section of the small intestine, the shortest, and where most chemical digestion takes place.

• The jejunum is the middle section of the small intestine. The lining of the jejunum is specialized for the absorption of small nutrient particles which were previously digested by enzymes in the duodenum. If the jejunum is impacted by blunt force, the emesis (vomiting) will be initiated.

• The ileum is the final section. It’s function is to absorb vitamin B12 and bile salts and any other

products not absorbed by the jejunum.

Large Intestine• Reabsorption of water as well as vitamin absorption occurs here

• Undigested wastes collect & compact here(until expelled/excreted)

• Sections of Large Intestine: Cecum, Ascending, Transverse, and Descending Colon, Rectum, Anus

Accessory Digestive Organs

•Salivary glands in mouth secrete saliva (essential for taste and forming bolus) & salivary amylase

•Teeth carry out mechanical digestion of food

•Tongue helps move food around in mouth to start digestion & helps form bolus and push it down esophagus

Liver

• Largest gland in body and is located under diaphragm in the RUQ

• Humans have 4 lobes

• One of the most important organs in body

• Detoxifies blood (i.e. drug detoxification)

• Produces bile

Bile is a yellow-green watery solution containing bile salts, bilirubin, cholesterol, and other substances. It is made in the liver but is stored in the gall bladder. It does not contain enzymes but the bile salts help to emulsify fat, breaking it down from large fat globules into smaller fat droplets which help with fat digestion in small intestine.

Bile

Gall Bladder•Small, thin, green sac

•Located near (inferior to) liver

•Stores and concentrates bile

•Release bile into small intestine for fat digestion through bile duct

FYI: Gallstones are hard, pebble-like deposits that form inside the gallbladder. Gallstones may be as small as a grain of sand or as large as a golf ball. The two main causes are an increase of bilirubin in the blood due to the breakdown of RBC’s and a build-up of cholesterol in the blood.

Gallstones

Pancreas

•Soft, long, pink, triangular gland that extends horizontally in abdominal cavity

•Produces enzymes that break down all categories of food (fats, proteins, and carbohydrates)

•Produces hormones such as insulin and glucagons

– What disorder is associated with the lack of insulin in the pancreas?

So altogether, the digestive system allows us to ingest and digest food so that we may obtain necessary nutrients and energy. Who can label our Digestive System?