25.1 General Anatomy and Digestive Processes Flashcards
digestive system
the organ system that processes food, extracts nutrients from it, and eliminates the residue
ingestion
the selective intake of food
digestion
the mechanical and chemical breakdown of food into a form useable by the body
absorption
the uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood or lymph
compaction
absorbing water and consolidating the indigestible residue into feces
defecation
the elimination of feces
mechanical digestion
the physical breakdown of food into smaller particles
chemical digestion
a series of hydrolysis reactions that break dietary macromolecules into their monomers, carried out by digestive enzymes
digestive tract (alimentary canal)
a muscular tube: mouth, pharynx, esophagus, stomach, small intestine, large intestine
gastrointestinal tract
stomach and intestines
accessory organs
teeth, tongue, salivary glands, liver, gallbladder, pancreas
mucosa (mucous membrane)
inner lining of the digestive tract, consisting of an epithelium, the lamina propria, and the muscularis mucosae
lamina propria
a thin layer of areolar tissue immediately deep to the epithelium of a mucous membrane
muscularis mucosae
a thin layer of smooth muscle immediately deep to the lamina propria of a mucosa
submucosa
a thicker layer of loose connective tissue containing blood vessels and lymphatics, a nerve plexus, and glands that secrete lubricating mucus into the lumen
muscularis externa
the external muscular wall of certain viscera such as the esophagus and small intestine
serosa
a thin epithelial membrane composed of a simple squamous epithelium overlying a thin layer of areolar tissue that covers the external surfaces of viscera and forms membranes
adventitia
a fibrous connective tissue layer in the pharynx, esophagus, and rectum that blends into the adjacent connective tissue of other organs
enteric nervous system
a nervous network that regulates digestive tract motility, secretion, and blood flow
submucosal plexus
network of neurons in the submucosa; controls movements of the muscularis mucosae and glandular secretion of the mucosa
myenteric plexus
network of neurons consisting of parasympathetic ganglia and nerve fibers between layers of the muscularis externa; controls peristalsis and other contractions of the muscularis externa
mesenteries
connective tissue sheets from which the stomach and intestines are loosely attached to the abdominal wall
parietal peritoneum
a serous membrane that lines the wall of the abdominal cavity
posterior mesentery
a translucent two-layered membrane extending to the digestive tract
anterior mesentery
a sheet of tissue that hangs freely in the abdominal cavity or attaches to the anterior abdominal wall or other organs
lesser omentum
mesentery that extends from the liver to the right superior margin (lesser curvature) of the stomach
greater omentum
large, fatty mesentery that hangs like an apron from the left inferior margin (greater curvature) of the stomach, loosely covering the large intestine; part of the body’s first line against toxins and infections
mesocolon
mesentery that anchors the colon
milky spots
clusters of lymphatic tissues in the omentum that collect antigens from the peritoneal fluid and initiate an immune response
intraperitoneal
within the peritoneal cavity; enclosed by mesentery (serosa) on all sides (e.g. stomach, liver, intestines)
retroperitoneal
outside of the peritoneal cavity; adjacent to the posterior abdominal wall and covered by peritoneum on the anterior side only (e.g. duodenum, pancreas, large intestine)
short (myenteric) reflexes
stretching or chemical stimulation of the digestive tract acts through the myenteric plexus to stimulate contractions in nearby regions of the muscularis externa (e.g. peristaltic contractions of swallowing)
long (vagovagal) reflexes
reflexes that act through autonomic nerve fibers that carry sensory signals from the digestive tract to the brainstem and motor commands back to the digestive tract
paracrine secretions
secretions (of histamine and prostaglandins) that diffuse through tissue fluids and stimulate nearby target cells
