Exam 3 Review: Chapter 23: General Digestive Histology
mucous membranes = mucosae - The specialized epithelial lining which produces a lubricating fluid containing the sticky protein mucin which traps microbes and dirt particles and protects any body structure which is continuous with the external environment except for the skin itself.
epithelium - Tissues with a high degree of cellularity and limited extracellular material, connected with specialized contact structures such as desmsomes, often organized in layers, which have no direct blood supply and which are derived from embryonic ectoderm and endoderm.
lamina propria - The supportive areolar = loose fibrous connective tissue layer found immediately beneath the mucosal epithelium and its basement membrane and the muscularis mucosae.
muscularis mucosae - The thin layer of smooth muscle which forms the boundary between the lamina propria of the mucosa and the submucosa in the walls of the gastrointestinal tract; contraction of this layer of smooth muscle pushes the mucosal membrane into small folds which increase the surface area for digestion and absorption of nutrients.
enteroendocrine cell - Any of a group of diffuse neuroendocrine cells,.also referred to as APUD cells (amine precursor uptake and decarboxylation cells), scattered individually among the cells of the exocrine glands from the stomach to the colon; their amine hormones diffuse into the blood capillaries, and ultimately influence several digestive system target organs; these cells, along with the nervous system, control and coordinate the muscular and secretory activities of the gastrointestinal tract; enteroendocrine cells typically extend a cytoplasmic process into the digestive tract lumen forming an important communication site to monitor the luminal contents, of which dietary amino acids are the most important stimulants; there are more than a dozen different types of enteroendocrine cell and a given enteroendocrine cell will only secrete one type of hormone, or hormone-like substance; these include gastrin, histamine, endorphins, serotonin, cholecystokinin and somatostatin.
MALT = mucosa-associated lymphatic tissue - The general term used for the various aggregations of lymphoid tissue found associated with the mucous membranes of the respiratory and digestive tracts; the consist of lymphatic nodules within the connective tissues walls (in the mucosa and submucosa) of these tubular organs; these lymphocytes are involved in immune defenses.
submucosa - The supportive loose fibrous connective tissue layer found immediately beneath the mucosal epithelium and its basement membrane; in the gastrointestinal tract it lies between the inner muscularis mucosae and the outer muscularis layer; it is the location for networks of nerves, blood vessels, lymphatic vessels, and lymphatic tissue and may be the location for mucous secreting glands.
neural plexus - The interlacing networks of nerve fibers which originate from certain cranial nerves, e.g., the Vagus (X) and the ventral rami of spinal nerves in which individual autonomic nerve processes from the brain stem and individual spinal segments become redistributed to that (1) each resulting branch of the plexus contains fibers from several cranial and spinal nerves and (2) fibers from each ventral ramus travel to the peripheral tissues of the body by several routes; this arrangement permits portion of the digestive tube to be innervated by autonomic motor (afferent) fibers from more than one spinal segment -- as a result, an injury to a single spinal segment or spinal motor (ventral) root cannot completely paralyze any organ.
submucosal plexus - The interlacing networks of unmyelinated nerve fibers
derived chiefly from the superior mesenteric plexus which is located within the
submucosa of the gastrointestinal tract, especially in the intestines; it
consists chiefly of visceral sensory fibers and postganglionic autonomic motor fibers; it is
concerned with the control of functions within the
inner walls of each gut segment, i.e., local absorption, secretion,
and contraction.
myenteric plexus - The interlacing networks of unmyelinated nerve fibers
derived chiefly from the superior mesenteric plexus which is located within the muscularis
of the gastrointestinal tract (between the inner circular and outer longitudinal
layers); it consists chiefly of postganglionic autonomic motor fibers; it is
concerned with the control of smooth muscle tone, peristalsis, and the
relaxation of the pyloric and ileocecal sphincters.
muscularis - The muscular coat or tunic of any hollow organ or tubular structure; its contractions propel the contents of the organ elsewhere; it lies between the inner submucosa and the outer adventitia or serosa; in the gastrointestinal tract, it typically consists of an inner circular layer and an outer longitudinal layer of smooth muscle, but, in the stomach, it also contains a middle oblique layer; it is the location for plexuses of postganglionic autonomic motor fibers concerned with the control of enteric smooth muscle tone, mixing and peristalsis.
serous membrane = serosa - A simple squamous lining found in the various ventral body cavities which lines the walls of the cavities and the organs contained therein and produces a watery serous fluid which lubricates the lining surfaces.
List:21. the type of epithelium lining each part of the digestive (gut) tube and explain why this epithelium promotes the functions of its respective part.
| Organ/Region | Lining Epithelium | Functional Explanation |
| Esophagus | nonkeratinized stratified squamous epithelium | protective lining to limit abrasion during deglutition (swallowing) |
| Stomach | simple columnar epithelium with many goblet cells | protective lining to limit autodigestion by HCl and pepsin |
| Small Intestine | simple columnar epithelium with brush border of microvilli and with goblet cells | microvilli increase surface area for absorption of water, electolytes, and nutrients |
| Large Intestine | simple columnar epithelium with many goblet cells | protective lining to limit abrasion during defecation and to limit invasion by intestinal microbes and parasites |
Diagram and Label:
1. a cross-section of the GI tract (= alimentary canal) showing the main tissue layers and their sublayers. List unique features of the histology of each organ (or region of each organ) of the GI tract.
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