Human Anatomy- Digestive System

Large intestine

Absorbs water from indigestible food residue and eliminates them from the body as feces. Subdivided into: cecum, appendix, colon, rectum, and anal canal.

Jejunum

Starts at the duodenum and ends at the ileum. Amino acid, sugar, fatty acid particles, vitamins, minerals, electrolytes and water are small enough to soak into the villi of the jejunum and drop into the blood stream.

Liver

Accessory organ associated with the small intestine. Most important organ and also has metabolic and regulatory roles. Digestive function-produce bile for export to duodenum. Main function- filter and process nutrient rich blood delivered to it.

Alimentary Canal

Also known as the GI tract. Continuous muscular digestive tube that winds through the body. Digests food-breaks it into smaller pieces-absorbs digested fragments. Consists of the following: -mouth -pharynx -esophagus -stomach -small intestine -large intestine

Appendix

Attached to the postermedial surface of the cecum. Contains small masses of lymphoid tissues. Plays a role in immunity.

Ileum

Starts at the duodenum and ends at the large intestine at the ileocecal valve. Mainly absorbs vitamin B12 and bile salts and whatever products of digestion that were not absorbed by the jejunum.

Small Intestine

Body's major digestive organ. Digestion is completed and all absorption occurs here. Three divisions are: duodenum, jejunum, ileum.

Visceral Peritoneum

Covers the external surfaces of most digestive organs

Mechanical Digestion

Digestive Process #3 Physically prepares food for chemical digestion by enzymes. -chewing -mixing of food with saliva by tongue -churning food in stomach -segmentation (rhythmic local constrictions of the intestine that mixes food with digestive juices and increases efficiency of absorption by repeatedly moving different parts of food mass over the intestine wall)

Chemical Digestion

Digestive Process #4 Series of catabolic steps that breaks down complex food molecules into their chemical building blocks by enzymes secreted into the lumen of the alimentary canal (begins in the mouth and completes in the small intestine)

Absorption

Digestive Process #5 Passage of digested end products (plus vitamins, minerals, and water) from the lumen of the GI tract through the mucosal cells by active or passive transport into the blood or lymph. (Small intestine is the major absorptive site)

Defecation

Digestive Process #6 Eliminates indigestible substances from the body via the anus in the form of feces. (Happens in large intestine)

Ingestion

Digestive process #1 Process of taking food into the digestive tract, usually through the mouth

Propulsion

Digestive process #2 Moves food through alimentary canal. Includes swallowing (voluntary) and peristalsis (involuntary) actions

Mesentery

Double layer of peritoneum- sheet of two serous membranes fused back to back and extends to the digestive organs from the body wall. These provide routes for blood vessels, lymphatics, and nerves to reach the digestive viscera, hold organs in place, and store fat.

Cecum

First part of large intestine, starts at ileocecal valve of the small intestine.

Colon

Has four regions: ascending- travels up the right side of the abdominal cavity to the level of the right kidney and makes a right angle turn transverse- travels across the abdominal cavity and bends acutely to the left descending- descends down the left side posterior abdominal wall sigmoid- enters pelvis

Anal canal

Last segment of the large intestine. Begins where rectum penetrates the levator ani muscle of the pelvic floor and opens to the body exterior at the anus. Has 2 sphincters: internal anal sphincter and external anal sphincter which act like purse strings to open and close the anus. Stay closed unless defacating.

Parietal Peritoneum

Lines the body walls

Stomach

Mechanical Digestion and propulsion of food. Chemical digestion of proteins. Absorption of a few fat soluable substances, alcohol, aspirin, and some drugs. Storage site of food until moved to duodenum.

Gallbladder

Organ that stores bile. Thin walled green sac

Pancreas

Produces enzymes (pancreatic juice) that break down all categories of food stuff- delivers the enzyme to the duodenum

Submandibular Gland

Salivary gland that lies along the medial aspect of the mandibular body. Its secretion duct runs beneath the mucosa of the oral cavity floor and opens at the base of the lingual frenulum. Contains equal numbers of serous and mucus cells

Parotid Glands

Salivary gland that lies anterior to the ear between the masseter muscle and skin. (Inflammation of this gland is called the Mumps) Contains only serous cells

Sublingual gland

Salivary gland that lies anterior to the submandibular gland under the tongue and opens via 10-12 ducts into the floor of the mouth. Contains mostly mucus cells

Serous Cells

Secretory cell that produces a watery secretion containing enzymes, ions, and a tiny bit of mucin.

Mucus Cells

Secretory cell that produces mucus (a stringy viscous solution)

Peritoneum

Serous membrane that forms the lining of the abdominal cavity

Duodenum

Starts at the stomach and ends at the jejunum. Contains the bile duct and main pancreatic duct which delivers bile from the liver and pancreatic juice from the pancreas through a bulb called hepatopancreatic ampulla in the wall of the duodenum. Carbohydrates are broken down by enzymes from the pancreas and liver into sugars. Fats are broken down by "lipase" from the pancreas into fatty acids.

Peristalsis

Waves of contraction and relaxation of muscles that squeezes food along the tract. Some mixing occurs in this process. Major means of propulsion

Bile

a digestive juice secreted by the liver and stored in the gallbladder. Contains bile salts, bile pigments, cholesterol, neutral fats, phospholipids, and electrolytes.

Rectum

segment of large intestine between sigmoid colon and anal canal. Contains 3 lateral curves called rectal valves. These valves seperate feces from flatus so that feces do not pass with gas.

Peritoneal Cavity

space between serous membranes

Accessory Digestive Organs

teeth tongue gallbladder digestive glands salivary glands liver pancreas