Digestive System (A/P 2)
Terms in this set (52)
Digestive System Includes
Digestive Tract, Accessory Digestive Organs
Digestive System Major Function
Process food until molecules are small enough to be absorbed (and utilized by the cells of the body) and waste products are eliminated
(GI Tract) the mouth, pharynx, esophagus, stomach, small intestine, and large intestine
Food Undergoes These Processes
Digestion, Absorption (GI Tract)
Metabolism (After Reabsorption)
Sum of all chemical reactions that take place in the body (including the utilization of nutrients).
Occurs after absorption.
Digestive system prepares nutrients for utilization by body cells through six activities:
First activity of the digestive system
Large pieces of food -> smaller ones
(Then enzyme activity begins)
Begins in the mouth with chewing (mastication) of food; continues with the turning and mixing actions within the stomach.
Complex molecules -> simple
For easy absorption
Food moves from mouth -> pharynx -> esophagus
Peristalsis: movements that propel the food particles through the digestive tract
(Rhythmic waves of contractions)
Simple molecules pass through the cell membrane of the lining in the small intestine into the blood or lymph capillaries
Food molecules that cannot be digested need to be eliminated from the body.
Defecation: removal of indigestible wastes through the anus, in the form of feces
Tunics of Alimentary Canal Wall
Surface epithelium (mostly simple columnar), Lamina propria (areolar CT), Muscular mucosal (small layer of smooth muscle)...
Secretion (enzymes, mucus, hormones)
Absorption of digested food
Protection (against bacteria)
Dense connective tissue.
Contains: Blood and lymphatic vessels, Scattered lymphoid follicles, Nerve fibers.
Intrinsic nerve supply: submucosal plexus.
Functions: Nutrition, Protection.
Bilayer of smooth muscle: Inner layer runs circularly, Outer layer runs longitudinally.
Intrinsic nerve plexus: myenteric plexus - controls smooth muscle of the musularis and thereby regulates GI motility.
Visceral peritoneum. Abdominopelvic Cavity.
Mesothelium associated with a thin layer of areolar connective tissue.
Reduces friction as digestive organs work and slide across one another and the cavity walls.
Layer of coarse fibrous connective tissue that binds the organ to surrounding tissues, i.e. esophagus.
Anchors and protects the surrounded organ.
Ingestion: Breaks down food into small particles by mastication.
Contains the teeth and the tongue.
Receives the secretions from the salivary glands.
Walls consist of two layers of skeletal muscle. Initiate wave-like contractions that propel food into the esophagus.
No digestive/absorptive function.
Gastroesophageal sphincter: jcn of esophagus and stomach.
(Thickening of smooth muscle layer, Controls food passage into the stomach)
Rugae: folds in stomach lining when the stomach is empty.(Allow for expansion and elasticity of the muscle folds for food intake.)
Storage of food, Mixing and breakdown of the food into chyme, Slow emptying into the duodenum at a rate suitable for digestion and absorption to occur.
Cardia -> Fundus -> Body -> Pylorus
Extends from pyloric sphincter to the ileocecal valve, where it empties into the large intestine. Finishes the process of digestion, absorbs the nutrients, and passes the residue on to the large intestine.
Duodenum -> Jejunum -> Ileum
(Villi, Microvilli, Plicae)
First, shortest, and widest.
Almost entirely fixed to the posterior body wall. (Only section)
Food from the stomach enters through the pyloric sphincter.
Bile and pancreatic ducts empty into.
Often empty, and generally thicker, more vascularized.
Inner mucus membrane is deeply folded for more absorbing surface area
Jejunum and ileum are suspended from the posterior body wall by a thin vascularized two-layer mesentery.
Longest Section. Contents empty into the cecum.Ileocecal valve between the ileum and the cecum allows chyme to travel one way only.
(lymphoid follicles) Spread under the mucosa of the entire small intestine, especially the ileum.
Remaining undigested food residue contains lots of bacteria that will be removed before entering the bloodstream.
Consolidate and propel unusable fecal matter toward the anus.
Also responsible for:
Absorption of water from the indigestible residue of food, Production of vitamins B and K.
Cecum -> Appendix -> Colon (Ascending, Transverse, Descending) -> Sigmoid -> Rectum -> Anus/anal canal
Small pouch near the ileocecal valve
Finger-like projection of lymphatic tissue near the cecum
Consists of: ascending colon, transverse colon, descending colon, sigmoid colon
Straight final portion of the large intestine
(opening to the rectum)
Internal sphincter - smooth muscle, involuntary
External sphincter - skeletal muscle, voluntary
Longitudinal bands of muscle that run the length of the large intestine.
Cause the large intestine to form pouches (haustra) that change location as the smooth muscle of the large intestine contracts.
Accessory Digestive Organs
Teeth, Salivary Glands, Liver, Gallbladder, Pancreas
Types: Primary, Secondary
Incisors, Cuspids/canines, Bicuspids/premolars and molars.
First set usually begins to appear at ~6 months.
Begin to appear at ~6-7 yo
Third molars = last teeth to erupt (Wisdom teeth)
Begin to erupt between ~17 - 25 yo
May remain embedded in he jaw bone
In some cases, absent all together.
Chiseled with sharp edges for biting
Cone shaped with points for grasping/tearing
Bicuspids/premolars and molars:
Flat surfaces with rounded projections for crushing/grinding
A tooth consists of two major regions:
Visible portion of the tooth which is covered by enamel
Portion embedded in the sockets of the mandible and the maxilla
Surrounds the pulp cavity forming the bulk of the tooth.
Hardest substance in the body.
Surrounds the dentin in the crown of the tooth.
Tooth Pulp cavity
Consists of connective tissue, blood vessels, and nerves.
Three pairs empty secretions into the oral cavity.
Parotid glands: the largest of the salivary glands
Submandibular glands: located on the floor of the mouth
Sublingual glands: in the floor of the mouth
Contains water, mucin (glycoprotein), and the enzyme amylase.
Largest gland in the body.
Four lobes divided by fissures.
Produce bile, which leaves the liver through the common hepatic duct then enters the duodenum through the bile duct.
emulsifies fats = breaks up large fat particles into smaller ones
Small, green sac on the inferior surface of the liver. Stores the bile that is made in the liver until needed by the body; enters through the cystic duct.
Elongated organ that lies below and behind the stomach. **Acinar Cells
Exocrine - Secretes substances into the digestive tract
Endocrine - Secretes hormones insulin and glucagon into the blood
Secrete digestive enzymes that help break down food in the small intestines.
Proteases (break up proteins)
Lipases (break up fats)
Amylase (breaks up carbohydrates)
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