Reproductive Systems

Mucous gland + duct (esophagus submucosal gland) (MYOO-kus gland): A tubuloacinar gland located deep in the submucosa of the esophagus; these glands secrete neutral mucus that lubricates and protects the esophageal lining, especially during the passage of a bolus. Gastric gland (GAS-trik gland): Simple, branched tubular glands found in the lamina propria (mucosa) of the stomach; they extend from the base of the gastric pits down to the muscularis mucosae and contain the various secretory cells of the stomach (chief, parietal, enteroendocrine, and mucous neck cells). Chief (zymogenic) cell (cheef zye-moh-JEN-ik sell): A pyramidal secretory cell found predominantly in the base of gastric glands; these cells have a granular apex (zymogen granules) and strong basal basophilia, and they secrete the inactive enzyme pepsinogen and gastric lipase. Parietal cell (Oxyntic cell) (puh-RYE-uh-tul sell/ok-SIN-tik sell): Large, rounded, or triangular cells found primarily in the upper half of gastric glands; they are characterized by an eosinophilic cytoplasm and a central nucleus, and they actively secrete hydrochloric acid (HCl) and intrinsic factor (necessary for Vitamin B12​ absorption). Enteroendocrine cell (en-ter-oh-EN-duh-krin sell): A dispersed cell type found throughout the epithelial lining of the gastrointestinal tract, especially in gastric glands and intestinal crypts; they secrete various peptide hormones (e.g., gastrin, serotonin) in a paracrine or endocrine fashion to regulate digestion. Mucous neck cell (MYOO-kus nek sell): Epithelial cells located in the neck region of the gastric glands; they secrete a soluble, acidic mucus (different from the surface mucus) that helps protect the epithelium within the glands. Surface epithelial cell (stomach) (SUR-fis ep-uh-THEE-lee-ul sell): The simple columnar epithelial cells that line the lumen and the gastric pits of the stomach; they secrete a thick, alkaline, visible layer of protective mucus that buffers the gastric acid. Gastric pit (Foveola) (GAS-trik pit/foh-VEE-oh-luh): The funnel-shaped indentations or depressions on the luminal surface of the stomach; the gastric glands open into the base of these pits. Mucosa (myoo-KOH-suh): The innermost layer of the gastrointestinal tract wall, composed of the lining epithelium, the underlying connective tissue (lamina propria), and a thin layer of smooth muscle (muscularis mucosae). Muscularis mucosae (mus-kyoo-LAIR-is myoo-KOH-see): A thin layer of smooth muscle found at the boundary between the mucosa and the submucosa; its contractions cause local movements of the mucosa, assisting in absorption and secretion. Mucous tubule (Duodenal gland) (MYOO-kus TOO-byool/doo-uh-DEE-nul gland) The secretory unit of the Duodenal glands (Brunner’s); these tubules are lined by mucus-secreting cells. Duodenal gland (Brunner’s) (doo-uh-DEE-nul gland/BROO-nerz gland): Large, branched, coiled glands located only in the submucosa of the duodenum; they secrete a highly alkaline mucus that protects the duodenal mucosa from the acidic chyme leaving the stomach and optimizes the pH for pancreatic enzymes. Myenteric plexus (Auerbach’s) (my-en-TER-ik PLEK-sus/OW-er-bahks PLEK-sus): A large parasympathetic ganglionated nerve plexus located between the inner circular and outer longitudinal layers of the muscularis externa; it primarily controls peristalsis and gastrointestinal motility. Submucosal plexus (Meissner’s) (sub-myoo-KOH-sul PLEK-sus/ MYZ-nerz PLEK-sus): A parasympathetic ganglionated nerve plexus located in the submucosa of the gastrointestinal tract; it primarily controls local functions such as gland secretion and muscularis mucosae contraction. Intestinal crypt (Crypt of Lieberkühn) (in-TES-tih-nul kript/kript uhv LEE-bur-koon): Simple tubular glands that extend downward from the base of the intestinal villi into the lamina propria; they contain stem cells for epithelial renewal, enteroendocrine cells, and specialized anti-microbial secretory cells (Paneth cells). Lacteal (LAK-tee-ul): A single, blind-ended lymphatic capillary located in the core of an intestinal villus; it is responsible for the absorption of dietary fats. Plica circulare (Valves of Kerckring) (PLY-kuh sur-kuh-LAIR-ee/valvz uhv KERK-ring): Permanent, large, circular folds of the mucosa and submucosa found prominently in the small intestine (especially jejunum); they increase the surface area and slow the passage of chyme to maximize absorption. Enterocyte (EN-ter-oh-syt): The principal absorptive cell of the small and large intestine; these tall columnar cells are characterized by a prominent apical microvilli layer (brush border) and are responsible for the final digestion and absorption of nutrients. Mitotic cell (my-TAH-tik sell): A cell undergoing cell division; in the intestine, these rapidly dividing stem cells are found predominantly at the base of the intestinal crypts, providing continuous renewal for the entire epithelial lining. Anti-microbial secretory cell (Paneth cell) (an-ty my-KROH-bee-ul SEK-ruh-tor-ee sell/PAN-eth sell): Specialized exocrine cells located in the base of the intestinal crypts; they have large, eosinophilic apical secretory granules and secrete defensive substances (e.g., lysozyme and defensins) that regulate the intestinal bacterial flora. Taenia coli (TEE-nee-uh KOH-ly): Three separate, narrow bands of thickened longitudinal smooth muscle that form the outer layer of the muscularis externa in the large intestine (colon); their tonic contraction creates the characteristic bulges (haustra) of the colon. Internal anal sphincter (smooth muscle) (in-TUR-nul AN-ul SFINGK-ter): A thickened, involuntary ring of smooth muscle that forms the terminal end of the inner circular layer of the muscularis externa; it is under autonomic control and provides resting anal tone. External anal sphincter (skeletal muscle) (eks-TUR-nul AN-ul SFINGK-ter): A thick, voluntary ring of skeletal muscle that surrounds the internal anal sphincter; it is under somatic (conscious) control and provides voluntary control over defecation. Apocrine sweat gland (AP-uh-krin swet gland): A type of coiled tubular sweat gland found abundantly in the skin of the axilla, groin, and perianal region (and modified in the breast); it secretes a viscous, protein-rich product into a hair follicle or to the skin surface. Anal canal (AN-ul kuh-NAL): The terminal portion of the large intestine leading to the anus; its lining transitions from simple columnar epithelium to stratified squamous epithelium. Anorectal junction (ay-noh-REK-tul JUNK-shun): The transition point between the simple columnar epithelium of the rectum and the non-keratinized stratified squamous epithelium of the upper anal canal; it marks the change from internal (visceral) to external (somatic) sensory innervation. Rectal venous plexes (REK-tul VEE-nus PLEK-sez): Extensive networks of veins found in the lamina propria and submucosa of the rectum and anal canal; engorgement or prolapse of these veins results in hemorrhoids. Central vein (liver) (SEN-trul vayne): The terminal hepatic venule that runs down the center of a classic hepatic lobule; blood flows from the periphery of the lobule, through the sinusoids, and collects here before draining into the hepatic veins. Perisinusoidal space (Space of Disse) (per-ih-sy-nuh-SOY-dul spays/spays uhv Diss): A narrow space located between the sinusoidal endothelial lining and the underlying hepatocyte cell plates; it is the site where plasma fluid collects and exchanges substances with the hepatocyte microvilli before the fluid enters the lymphatics. Bile canaliculi (byl ka-nuh-LIK-yoo-ly): Small, tiny channels or grooves formed by the tight junctions and adjacent membranes of two neighboring hepatocytes; they are the starting point for bile flow, which travels outward towards the portal triad. Hepatocyte (HEP-uh-toh-syt): The principal parenchymal cell of the liver; these large, polyhedral epithelial cells perform most of the liver's metabolic functions, including nutrient storage, synthesis of plasma proteins, detoxification, and bile production. Portal triad (POR-tul TRY-ad): A characteristic arrangement of three structures found at the corners of a classic hepatic lobule; it contains a branch of the interlobular portal venule, a branch of the interlobular hepatic arteriole, and an interlobular bile duct. Interlobar bile duct (in-ter-LOH-ber byl dukt): A small duct lined by cuboidal epithelium that is part of the portal triad; it collects bile from the bile canaliculi and carries it toward the hepatic duct. Interlobar portal venule (in-ter-LOH-ber POR-tul VEN-yool): A branch of the hepatic portal vein found in the portal triad; it carries nutrient-rich, deoxygenated blood from the gastrointestinal tract to the liver sinusoids. Interlobar hepatic arteriole (in-ter-LOH-ber huh-PAT-ik ar-TIR-ee-ohl): A branch of the hepatic artery found in the portal triad; it carries oxygenated blood to the liver sinusoids to meet the high metabolic demands of the hepatocytes. Crypts/diverticuli (gall bladder) (kripts dy-ver-TIK-yoo-ly): Pouch-like invaginations of the gall bladder's simple columnar epithelium (often called Rokitansky-Aschoff sinuses when they penetrate the muscle layer); their presence suggests an overgrowth or pathological change in the mucosa. Pancreatic islet (Islet of Langerhans) (pang-kree-AT-ik EYE-let): The pale-staining endocrine component of the pancreas, appearing as ovoid clusters of specialized cells (alpha, beta, delta, F cells) interspersed among the exocrine pancreatic acini; it secretes hormones (insulin, glucagon, somatostatin) that regulate blood glucose. Beta cell (β cell) (BAY-tuh sell): The most numerous cell type in the pancreatic islet; these cells secrete the hormone insulin, which lowers blood glucose levels. Alpha cell (α cell) (AL-fuh sell): A cell type found mainly in the periphery of the pancreatic islet; these cells secrete the hormone glucagon, which raises blood glucose levels. Delta cell (δ cell) (DEL-tuh sell): A cell type found in the pancreatic islet; these cells secrete the hormone somatostatin, which acts locally to inhibit the secretion of insulin and glucagon. F cell/PP cell (ef sell/pee pee sell): A minor cell type in the pancreatic islet; these cells secrete pancreatic polypeptide, which primarily regulates exocrine pancreatic secretion. Fenestrated capillary (FEN-uh-stray-ted KAP-ih-lair-ee): A capillary whose endothelial cells contain large pores (fenestrae); these are highly permeable vessels found in endocrine glands (pancreatic islet) and the kidney (glomerulus) to facilitate rapid substance exchange. Interlobular duct (in-ter-LAH-byoo-ler dukt): A large, cuboidal or columnar epithelial-lined duct that collects the secretion from several pancreatic acini; these ducts converge to form the main pancreatic duct. Pancreatic acini (exocrine cells) (pang-kree-AT-ik AS-ih-ny): The spherical or berry-like secretory unit of the exocrine pancreas; these cells secrete an alkaline fluid rich in digestive proenzymes (e.g., trypsinogen, amylase, lipase) into the duct system.