From Canvas (Anatomy Vocabulary) - Unit 9: The Digestive System

Gastroenterology

The medical specialty that studies the anatomy and physiology of the gastrointestinal system and uses diagnostic tests, medical and surgical procedures, and drugs to treat gastrointestinal diseases.

Gastroenterologist

A physician who specializes in the study of the gastrointestinal tract.

Abdomen and Abdominopelvic Cavity

The region that contains the largest organs of the gastrointestinal system, whose walls are lined by the peritoneum; this membrane secretes a watery peritoneal fluid that fills spaces between organs and allows them to slide past each other during digestive movements.

Digestive System

Also known as the gastrointestinal (GI) tract or alimentary canal, it begins at the mouth, continues through the thoracic cavity, and fills most of the abdominal cavity; its purpose is to digest food, absorb nutrients, and remove undigested material (waste) by altering the chemical and physical composition of food (digestion) to prepare it for absorption into the bloodstream and use by body cells.

Upper GI tract

The section of the digestive system that includes the structures from the mouth through the stomach, specifically consisting of the oral cavity, pharynx, esophagus, and stomach.

Oral cavity (Buccal cavity)

The mouth area consisting of the lips, cheeks, hard palate, soft palate, uvula, tongue, teeth, and gums.

Lips and the cheeks

Structures that form the walls of the oral cavity and function to keep food in the mouth while chewing.

Hard palate

The anterior (front, closest to lips) aspect of the roof of the mouth which is supported by bone.

Soft palate

The posterior portion of the roof of the mouth (closer to the throat) made up of skeletal muscle and connective tissue that ends in a small projection called the uvula.

Uvula

A small projection at the end of the soft palate that functions in speech articulation, prevents food from entering the breathing passage and nasal cavities, and is responsible for our gag reflex.

The tongue

A strong, flexible skeletal muscle covered with a mucous membrane, located in the lower jaw bone (mandible), which acts as the principle organ of taste via upper-surface papillae containing taste buds (detecting sweet, sour, salty, bitter); it assists in chewing (mastication) and swallowing (deglutition) by moving food around, mixing it with saliva, shaping it into a ball-like mass known as a bolus, and pushing it toward the throat (pharynx).

Teeth

Structures primarily responsible for chewing (mastication) where food is ground and softened by saliva; the primary set consists of 20 deciduous teeth appearing around 6 months of age, and the secondary set consists of 32 permanent teeth beginning to appear around age 6.

Salivary glands

Three pairs of accessory structures (Parotids near the ear, Submandibulars under the mandible, and Sublinguals under the tongue) that release saliva via ducts into the mouth when triggered by the sight, smell, and taste of food; saliva is mostly water to liquefy food, but contains mucus as a lubricant and digestive enzymes like amylase (digests carbohydrates) and lipase (digests fats).

Pharynx

Known as the throat, this serves as a passageway for both oxygen/respiratory and food/liquid/digestive systems; it is propelled by peristalsis (wavelike contractions of smooth muscle) and divided into three sections: the oropharynx (leading away from the oral cavity), the nasopharynx (behind the nasal cavity), and the laryngopharynx (the lower portion opening into the esophagus and larynx).

Oral Cavity and Pharynx Swallowing

The process where swallowing (deglutition) moves food into the pharynx as the soft palate, uvula, and tongue close off the nasal cavity, while the epiglottis closes the entrance to the larynx so food goes into the esophagus rather than the airway, preventing food from pressing on the uvula and initiating the gag reflex.

Esophagus

A muscular tube about 10 inches long that passes through an opening in the diaphragm into the abdominal cavity, connecting the pharynx to the stomach; it receives food from the pharynx and propels it via a series of wavelike muscular contractions called peristalsis.

Lower esophageal sphincter (LES) or cardiac sphincter

The muscle located in the distal esophagus that controls the passage of food from the esophagus into the stomach; it relaxes and opens to allow food through, and contracts and closes to prevent stomach contents from re-entering the esophagus.

Stomach

A large, muscular, elongated sac located in the left upper quadrant (LUQ) of the abdomen that receives food from the esophagus, churns it via muscular action to mix it with secretions, and breaks it down using gastric juices into a liquidlike mixture of partially digested food and secretions called chyme.

Fundus

The upper region of the stomach located to the left and above the opening of the esophagus into the stomach.

Body of stomach

The central, main portion of the stomach which curves to the right.

Pylorus

The lower tubular section of the stomach (also referred to as the gastric antrum) that angles to the right and leads to the small intestine, containing the pyloric sphincter which regulates the passage of food into the duodenum.

Rugae

Thick, deep folds and ridges in the mucous membrane/gastric mucosa of the stomach that expand to accommodate food as the stomach fills; the mucosa also produces mucus to protect the stomach lining from its own produced acid, and the depressions between folds contain gastric glands that secrete gastric juices.

Small intestine

Also known as the small bowel, this is a long, hollow tube approximately 18-21 feet long that loops around, filling most of the abdominal cavity, where chyme is mixed with bile and pancreatic juice so that the digestive process can be completed and nutrients/water can be absorbed through the intestinal wall into the capillaries.

Duodenum

The first part of the small intestine, extending 10-12 inches from the pylorus of the stomach to the jejunum, where chyme enters along with liver and pancreas secretions to further digestion, and where absorption of nutrients and water mainly takes place.

Jejunum

The second part of the small intestine, measuring about 8 feet long, where absorption of nutrients and water chiefly takes place.

Ileum

The third part of the small intestine, measuring about 12 feet long, which connects to the large intestine at the ileocecal sphincter.

Villi

Millions of tiny projections on the mucous membrane lining of the small intestine that produce digestive enzymes such as lactase to break down sugars, and help to sweep absorbed nutrients into the surrounding capillaries and lymph vessels to be carried by blood in the portal vein to the liver.

Ileocecal sphincter

A muscular ring/sphincter at the junction of the ileum and large intestine that prevents backflow of material from the large intestine back into the small intestine.

Large intestine

A 5-foot-long hollow tube (large bowel) that begins at the ileocecal sphincter and extends to the anus; it receives undigested material and water from the small intestine, slowly moving it via waves of peristalsis while absorbing remaining water through the intestinal wall into the blood until it is eliminated as solid waste (feces or stool) via defecation.

Cecum

A pouch on the right side of the abdomen between the ileocecal junction and the colon, forming the first section of the large intestine.

Appendix

A structure extending from the lower portion of the cecum that is now known to contain white blood cells that help to destroy microorganisms.

Colon

The longest part of the large intestine that travels through all four quadrants of the abdomen and is divided into four sections: the ascending colon, transverse colon, descending colon, and the sigmoid colon (which connects the colon to the rectum).

Rectum

The last 7 to 8 inches of the large intestine that stores waste and connects the colon to the anus.

Anus

The terminal opening of the digestive tract through which feces are eliminated from the body, featuring an anal sphincter that controls the elimination of waste materials from the rectum during the process of defecation or elimination.

Liver

The largest glandular accessory organ in the body, weighing 3 to 4 lbs and located in the right upper quadrant (RUQ) immediately under the diaphragm; its main digestive function is to process raw nutrients absorbed from the small intestine via the portal vein to make all the chemicals the body needs, and its hepatocytes continuously produce bile (a yellowish-green, bitter fluid containing salts, pigments like bilirubin, and cholesterol) to emulsify/break apart fats into fatty acids and help carry away waste. The liver has more than 500 functions, and some of them are: Amino acid (Protein) metabolism | Carbohydrate metabolism (Changes glucose to glycogen and stores it until needed by body cells. When required, glycogen is converted back to glucose | Fat metabolism (The liver serves as a storage place and acts to desaturate fats before releasing them into the bloodstream.) | Produces cholesterol and special proteins to help carry fats through the body | Phagocytosis of old, worn-out red blood cells (erythrocytes) and incorporates them into bile | Detoxification- Detoxifies many harmful substances (toxins) such as drugs and alcohol. Converts potentially harmful substances into less toxic ones. | Storage of vital nutrients- The liver stores iron and vitamins B12, A, D, E, and K. | Uses amino acids to build plasma proteins and clotting factors for the blood.

Additional functions of the liver

Processes including amino acid (protein) metabolism to build plasma proteins and clotting factors; carbohydrate metabolism (converting excess glucose to glycogen via glycogenesis for storage, and glycogen back to glucose via glycogenolysis); fat metabolism/storage; synthesis of cholesterol; phagocytosis of old red blood cells (erythrocytes) to recycle iron and create bile pigments; detoxification of harmful toxins like drugs and alcohol; and storage of vital nutrients like iron and vitamins B12, A, D, E, and K.

Gallbladder

A pear-shaped sac (cholecyst) located on the undersurface/posterior of the liver, connected to it by the cystic duct (which joins the hepatic duct to form the common bile duct leading to the duodenum); its main function is to store and concentrate bile, contracting to release it into the duodenum to emulsify fats when fatty chyme is present.

Pancreas

An accessory organ located in the left upper quadrant (LUQ) posterior to the stomach that functions as an exocrine gland to secrete digestive juices into the pancreatic duct, and as an endocrine gland to secrete hormones into the bloodstream.

Exocrine Functions of Pancreas

The secretion of digestive enzymes into the duodenum in response to food, including Trypsin (breaks down proteins), Pancreatic lipase (breaks down fats), Pancreatic amylase (breaks down carbohydrates), and Sodium bicarbonate (neutralizes acidic stomach contents).

Endocrine Functions of Pancreas

The manufacture of insulin by beta cells (enabling glucose to pass from blood into cells for energy and promoting glycogenesis to store excess glucose as glycogen in the liver) and glucagon by alpha cells (stimulating the liver to convert stored glycogen back to glucose via glycogenolysis when blood glucose is low).

Mechanical digestion

The physical breakdown of food using mastication (chewing) to decimate food, deglutition (swallowing), and peristalsis to move the food or bolus through the esophagus, stomach, and intestines; it also involves the mechanical breaking apart/emulsification of fats in the duodenum.

Chemical digestion

The chemical breakdown of food using enzymes (indicated by the suffixes -ase and -zyme) and acids, starting in the mouth with salivary amylase breaking down carbohydrates, continuing in the stomach with hydrochloric acid, pepsinogen, and gastrin, and completing in the small intestine.

Cholecystokinin

A hormone secreted by the duodenum in response to fatty chyme that stimulates the gallbladder to contract and release bile for fat emulsification, and stimulates the pancreas to secrete its four digestive enzymes (amylase, lipase, and protein-breaking enzymes) into the duodenum.

Life Span Considerations: Aging

Changes over time where the digestive system becomes less motile, gastric motor activity slows (delayed gastric emptying and diminished hunger contractions), nutrient absorption is mildly reduced, teeth are mechanically worn down, gums recede, taste buds are lost causing changing food preferences, and glandular secretions decrease resulting in a drier mouth and less gastric juices.

Alkaline Phosphatase (ALP)

An enzyme found in the highest concentrations in the liver, biliary tract, and bone.

Amylase

An enzyme secreted normally from pancreatic cells (and salivary glands) that travels to the duodenum by way of the pancreatic duct to aid in the digestion of carbohydrates.

glucose

A simple sugar found in foods, especially fruits, that serves as a major source of energy for body cells.