Digestive System Overview

Alimentary canal

One-way tube from the mouth to the anus

Mucosa

Mucinous epithelium in direct contact with ingested food surrounded by a layer of loose connective tissue and a layer of smooth muscle

Enteroendocrine cell

Cell that secretes hormones into the interstitial space between cells

Goblet cell

Cell that secretes mucus and fluid into the lumen

Lamina propria

Areolar tissue layer with blood and lymphatic vessels to transport absorbed nutrients from the alimentary canal

Muscularis mucosae

Thin layer of smooth muscle in a constant state of tension, pulling the mucosa of the stomach and small intestine into undulating folds

Submucosa

Broad layer of dense connective tissues that connects the mucosa to the underlying muscularis; contains blood and lymphatic vessels, nerves, and glands

Muscularis externa

Double layer of smooth muscle that contract to promote mechanical digestion; inner layer is circular, outer layer is longitudinal

Tenia coli

Three narrow parallel bands of longitudinal muscle found in the muscularis externa of the large intestine

Serosa

Layer of visceral peritoneum overlaying a layer of loose connective tissue superficial to the muscularis; only found in the region of alimentary canal within the abdominal cavity

Adventita

Dense sheath of collagen fibers that hold the alimentary canal in place; replaces the serosa in the mouth, pharynx, and esophagus

Myenteric plexus

Part of the enteric nervous system responsible for motility (rhythm and force of contractions); in the muscularis layer

Submucosal plexus

Part of the enteric nervous system responsible for regulating digestive secretions and reacting to the presence of food; located in the submucosal layer

Splanchnic circulation

Supplies blood to the digestive system and transports nutrients absorbed by mucosal cells to the liver

Lesser omentum

Suspends the stomach from the inferior border of the liver; provides a pathway for structures connecting to the liver

Mesocolon

Attaches two portions of the large intestine (transverse and sigmoid) to the posterior abdominal wall

Peritoneum

A broad serous membranous sac made of squamous epithelium tissue

Greater omentum

Apron-like structure that lies superficial to the small intestine and transverse colon; site of fat deposition

Mesentery

Vertical band of tissue anterior to the lumbar vertebrae that anchors the small intestine (except the duodenum)

Ingestion

Entry of food into the alimentary canal through the mouth; food is chewed and mixed with saliva containing digestive enzymes

Falciform ligament

Anchors the liver to the anterior abdominal wall and inferior border of the diaphragm

Propulsion

Movement of food through the digestive tract, including the voluntary process of swallowing and the involuntary process of peristalsis

Peristalsis

Sequential, alternating waves of contraction and relaxation of alimentary wall smooth muscles, which act to propel food along and mix it with digestive juices

Segmentation

Localized contractions of circular muscle of the muscularis that isolate small sections of the intestine, moving their contents back and forth while continuously subdividing, breaking up, and mixing the contents