Histology of the Digestive System

Comprehensive vocabulary flashcards covering the histology of the gastrointestinal tract, oral cavity, teeth, and accessory organs such as the liver and pancreas.

GALT

The gut-associated lymphoid system, which is a defense mechanism distributed throughout the digestive tract.

Mucosa

The innermost layer of the alimentary canal consisting of an epithelial lining, lamina propria, and muscularis mucosae.

Submucosa

A layer of dense irregular connective tissue containing blood and lymph vessels and the Meissner's nerve plexus.

Muscularis Externa

The layer containing smooth muscle cells usually arranged into an inner circular layer and an outer longitudinal layer.

Myenteric (Auerbach's) nerve plexus

A nerve plexus located between the two muscle sublayers of the muscularis externa.

Pyloric sphincter

A gastroduodenal sphincter that controls the release of chyme into the duodenal portion of the small intestine.

Serosa

The outermost layer of the alimentary canal consisting of a simple squamous mesothelium and loose connective tissue.

Lining mucosa

The nonkeratinized stratified squamous epithelium covering the inner surface of the lips, cheeks, soft palate, and floor of the mouth.

Masticatory mucosa

The keratinized stratified squamous epithelium covering the gingiva and hard palate, which lacks a submucosa.

Filiform papillae

The smallest and most numerous papillae on the tongue; they are conical, highly keratinized, and do not contain taste buds.

Fungiform papillae

Mushroom-shaped projections on the tongue that contain taste buds on their dorsal surface.

Circumvallate papillae

Large, dome-shaped structures ($8$ to $12$ in number) located anterior to the sulcus terminalis containing numerous taste buds.

von Ebner’s glands

Lingual salivary glands that empty serous secretions into the base of the moats of circumvallate papillae.

Neuroepithelial cells

Sensory cells in taste buds that synapse with afferent neurons of CN VII, CN IX, or CN X.

Enamel

The hardest substance in the body, composed of $96$ to $98\%$ calcium hydroxyapatite.

Ameloblasts

Cells derived from the enamel organ that produce enamel but degenerate when a tooth erupts.

Dentin

The most abundant dental tissue, containing $70\%$ hydroxyapatite and produced by neural crest-derived odontoblasts.

Cementum

An avascular, bonelike material consisting of $65\%$ mineral that is secreted by cementocytes.

Sharpey’s fibers

Fibers that extend from the periodontal ligament into the cementum of the tooth.

Apical foramen

The site at the tip of the tooth root where blood vessels and nerves enter the pulp cavity.

Waldeyer’s ring

The circular organization of tonsils in the pharynx, including the palatine, tubal, pharyngeal, and lingual tonsils.

Esophageal glands proper

Small, compound, tubuloalveolar glands located in the submucosa of the esophagus.

Rugae

Longitudinal submucosal folds that allow the stomach to distend when filled.

Parietal (Oxyntic) cells

Cells in the gastric glands that produce $HCl$ and intrinsic factor, with a lifespan of $150$ to $200$ days.

Chief (Zymogenic) cells

Cells in the lower region of gastric glands that produce pepsinogen and lipase.

Intrinsic factor

A glycoprotein produced by parietal cells necessary for the absorption of vitamin $B_{12}$ in the ileum.

Plicae circulares

Permanent transverse folds of mucosa and submucosa in the small intestine, also known as Kerckring's valves.

Crypts of Lieberkühn

Simple tubular intestinal glands located between the villi in the small intestine.

Paneth cells

Cells located deep in intestinal crypts that possess acidophilic apical secretory vesicles and secrete antimicrobial substances.

Peyer's patches

Aggregates of lymphoid nodules in the lamina propria and submucosa of the ileum.

M cells (microfold cells)

Specialized epithelial cells covering Peyer's patches involved in the gut-associated lymphoid system.

Teniae coli

Three prominent longitudinal bands formed by the condensation of the outer longitudinal layer of the muscularis externa in the large intestine.

Anal transitional zone (ATZ)

The middle third of the anal canal characterized by a stratified columnar epithelium.

Demilunes

Serous cells forming crescent-shaped caps under mucous cells in mixed secretory units of salivary glands.

Parotid gland

A major salivary gland that is a branched acinar gland and exclusively serous.

Centroacinar cells

Duct cells located inside the pancreatic acinus that mark the beginning of the intercalated duct.

Islets of Langerhans

Spherical bodies of endocrine cells in the pancreas containing alpha, beta, delta, and F cells.

Glisson's capsule

The thin connective tissue capsule that covers the liver.

Space of Disse

A perisinusoidal space between the sinusoidal endothelium and hepatocytes that serves as the site for material exchange.

Kupffer cells

Phagocytic cells found within the walls of the liver sinusoids.

Portal triad

The collection of a venule (portal vein branch), arteriole (hepatic artery branch), and bile duct located at the corners of liver lobules.

Rokitansky-Aschoff sinuses

Deep diverticula of the mucosa that may extend through the muscularis externa of the gallbladder.