Functions of the Organs of the Digestive System

Mouth: The mouth analyzes and recognizes food material before swallowing, physically processes food with the actions of the teeth and tongue, and mixes food with mucus and saliva, making it easier to swallow.

Pharynx: The Pharynx is a passage for food, liquids, and air. It carries food from the mouth to the esophagus.

Esophagus: The esophagus transports food material from the mouth to the stomach

Stomach: The stomach is responsible for the bulk storage of ingested food, the mechanical breakdown of ingested food, and the chemical digestion of ingested food through the disruption of chemical bonds by acids and enzymes

Small Intestine: The small intestine is the primary organ of nutrient digestion and absorption through the use of enzymes.

-The three subdivisions of the small intestine are:

-The duodenum

-The jejunum

-The ileum

Large Intestine: The large intestine absorbs vitamins, compacts intestinal contents into feces, and stores fecal matter before defecation.

-The five subdivisions of the large intestine are:

-The cecum

-The ascending colon

-The transverse colon

-The descending colon

-The sigmoid colon

Rectum: The rectum temporarily stores fecal matter before defecation.

Anus: The anus excretes indigestible material from the body.

Salivary Glands: The salivary glands secrete saliva and certain enzymes that break down carbohydrates.

Liver: The liver has a wide variety of functions, including: secretion of bile, storage of nutrients, storage of glycogen and lipid reserves, maintenance of normal blood glucose, amino acid, and fatty acid concentrations, synthesis and release of cholesterol, inactivation of toxins, breakdown of circulating hormones, and blood storage.

Pancreas: The pancreas secretes buffers, digestive enzymes, and hormones.

Gallbladder: The gallbladder stores and concentrates bile before its excretion into the small intestine.

Sphincters: Sphincters are circular muscles that are arranged around the openings and passageways of the digestive system. The contractions of these muscles aid in the movement of material through the digestive system.

The Digestive System

The digestive system allows the human body to ingest and process food. Food is broken down into small molecules by the digestive system so that it can be absorbed by the lining of the digestive tract and transferred to the blood.

Alimentary Organs of the Digestive System

Mouth

Pharynx

Esophagus

Stomach

Small Intestine

Large Intestine

Rectum

Anus

Accessory Organs of the Digestive System

Salivary Glands

Liver

Gallbladder

Pancreas

Carbohydrate Digestion

In the oral cavity, pharynx, and esophagus, polysaccharides are broken down into smaller polysaccharides or disaccharides such as maltose by salivary amylase.

In the lumen of the small intestine, polysaccharides are broken down into disaccharides such as maltose by pancreatic amylases.

In the epithelium of the small intestine, disaccharides are broken down into monosaccharides by disaccharidases.

Protein Digestion

In the stomach, proteins are broken down into small polypeptides by pepsin.

In the lumen of the small intestine, polypeptides are broken down into amino acids by pancreatic trypsin, chymotrypsin and carboxypeptidase.

In the epithelium of the small intestine, small peptides are broken down into dipeptidase, carboxypeptidase, and aminopeptidase.

Lipid Digestion

In the lumen of the small intestine, fat globules are broken down into smaller fat droplets by bile salts. Then, the fat droplets are broken down into glycerol, fatty acids, and glycerides by pancreatic lipase.

Disorders of the Digestive System

Ulcers

Ulcers are open sores on the lining of the stomach or small intestine. Ulcers can be caused by infection, inflammation, or frequent use of certain medications. The most common symptom of an ulcer is abdominal pain but ulcers can also cause nausea, vomiting, appetite changes, or weight loss. Treatment of ulcers usually includes antibiotics to kill bacterium and other medications that reduce the level of acid in the digestive system to relieve pain and speed healing. The risk of the average person developing an ulcer is about 10%.

Celiac Disease

Celiac Disease is a digestive condition triggered by gluten consumption. When a person with Celiac Disease eats foods containing gluten, an immune response is issued by their small intestines. This can result in damage to the small intestines or an inability to absorb certain nutrients. Celiac Disease can cause symptoms such as abdominal pain and diarrhea. Eventually, the inability of the small intestine to absorb nutrients can also result in vitamin deficiencies. There is no cure for Celiac Disease, but it can be managed by diet change. Prevalence of Celiac Disease in the United States is at least 1 in 133.