Digestive System

OT Dude Academy’s Free NBCOT® Exam Prep Course Medical Terminology, Anatomy, and Physiology Digestive System
Contents Hide
1 Mouth
2 Tongue
3 Salivary Glands
4 Pharynx
5 Esophagus
6 Stomach
7 Small Intestines
8 Large Intestines
9 Cecum
10 Colon
11 Accessory Digestive Organs
12 Function of the Digestive System

Source 1  licensed under Creative Commons Attribution 4.0 International License.

Mouth

  • The oral cavity is made of the cheeks, tongue, and palate.
  • The lips (labia) are at the entrance to the mouth.
  • The soft palate is composed mainly of skeletal muscle.
  • The uvula drops down from the center of the posterior edge of the soft palate.
  • During the swallowing phase, the soft palate and uvula move upward, helping to keep foods and liquids from entering the nasal cavity.
  • The palatine tonsils are clusters of lymphoid tissue that protect the pharynx.
  • The Lingual tonsils are located at the base of the tongue.

Tongue

  • Facilitates ingestion, mechanical digestion, chemical digestion (lingual lipase), sensation (taste, texture, temperature), swallowing, and vocalization.

Salivary Glands

  • Housed within the mucous membranes of the mouth and tongue.
  • Exocrine glands secrete saliva.
  • Saliva secretion increases when eating and is essential to moisten food and initiate the chemical breakdown of carbohydrates.
  • Saliva is also secreted by the labial glands in the lips.
  • The buccal glands in the cheeks, palatal glands in the palate, and lingual glands in the tongue ensure that all areas of the mouth are supplied with adequate saliva.

Pharynx

  • Involved in both digestion and respiration.
  • When food enters the pharynx, involuntary muscle contractions close off the air passageways.
  • The nasopharynx is involved in breathing and speech.
  • The oropharynx and the laryngopharynx are used for both breathing and digestion.

Esophagus

  • A muscular tube that connects the pharynx to the stomach.
  • The upper esophageal sphincter controls the movement of food from the pharynx into the esophagus.
  • Rhythmic waves of peristalsis, which begin in the upper esophagus, propel the bolus of food toward the stomach.
  • Secretions from the esophageal mucosa lubricate the esophagus and food.

Stomach

  • Four main regions in the stomach: the cardia, fundus, body, and pylorus.
  • The smooth muscle pyloric sphincter is located at this latter point of connection and controls stomach emptying.
  • In the absence of food, the stomach deflates inward, and its mucosa and submucosa fall into a large fold called a ruga.

Small Intestines

  • Chyme released from the stomach enters the small intestine, which is the primary digestive organ in the body.
  • Also where practically all absorption occurs.
  • Its large surface area is necessary for complex processes of digestion and absorption that occur within it.
  • 3 Regions: duodenum, jejunum, ileum.

Large Intestines

  • Functions to finish absorption of nutrients and water, synthesize certain vitamins, form feces, and eliminate feces from the body.
  • 4 main regions: the cecum, the colon, the rectum, and the anus.
  • The ileocecal valve, located at the opening between the ileum and the large intestine, controls the flow of chyme from the small intestine to the large intestine.

Cecum

  • Cecum receives the contents of the ileum and continues the absorption of water and salts.
  • The appendix contains lymphoid tissue, suggesting an immunologic function, but largely considered vestigial (having become functionless in the course of evolution).

Colon

  • The cecum blends seamlessly with the colon.
  • Food travels up the ascending colon, past the hepatic flexure, through the transverse colon, takes a turn at the splenic flexure, down the descending colon, and then the sigmoid colon before reaching the rectum.

Accessory Digestive Organs

  • Chemical digestion in the small intestine relies on the activities of three accessory digestive organs: the liver, pancreas, and gallbladder.
    • The digestive role of the liver is to produce bile and export it to the duodenum.
    • The gallbladder primarily stores, concentrates, and releases bile.
    • The pancreas produces pancreatic juice, which contains digestive enzymes and bicarbonate ions, and delivers it to the duodenum.

Function of the Digestive System

  • Ingesting food
  • Digesting food
  • Absorbing nutrients
  • Elimination of waste products

 

 

  1. Betts, J.G., Young, K.A., Wise, J.A., Johson, E., Poe, B., Kruse, D. H., Korol, O., Johnson, J.E., Womble, M. & DeSaix, P. (2013). Anatomy and Physiology. OpenStax. http://cnx.org/content/col11496/latest/[↩]
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