Digestive System Part I: Alimentary Canal Flashcards

Digestive System
Terms Definitions
Organs of the digestive system
consist of those that form the digestive tract and those that are called accessory organs.
Digestive tract/alimentary canal/gastrointestinal (GI) tract
make up a hollow tube that extends from oral cavity to anus; consist of organs – mouth, pharynx, esophagus, stomach, small intestine, large intestine
Mouth, pharynx, esophagus, stomach, small intestine, large intestine
organs of the alimentary canal/GI tract
Accessory organs of digestive System
empty their products into the alimentary canal via ducts; include these organs – salivary glands, liver, gallbladder, pancreas
Salivary glands, liver, gallbladder, pancreas
accessory organs of digestive system
Ingestion
eating food, drinking liquids
Propulsion
movement of food through alimentary canal; includes swallowing and peristalsis
Swallowing
part of propulsion; voluntary process dependent on skeletal muscle
Peristalsis
major means of propulsion; involuntary process dependent on smooth muscle; involves alternate waves of contraction & relaxation of musculature in the organ walls; net effect is to squeeze food from one organ to the next
Mechanical/Physical Digestion
the physical manipulation of food to prepare it for enzymatic chemical digestion; exemplified by the chewing of food by teeth and the churning of food by the stomach.
Chemical Digestion
refers to the chemical breakdown of large, complex food molecules into smaller building block molecules via enzymes; includes enzymatic breakdown of large carbohydrates to simple sugars, proteins to amino acids, lipids to fatty acids
Absorption
primarily involves movement of digested end products from lumen of GI tract into blood in blood capillaries; but some lipids/fats are also absorbed into lymph in lymphatic capillaries called lacteals
Defecation
elimination of largely indigestible material from the body via anus in form of feces
Same from digestive tract through large intestine; Mucosa, submucosa, muscularis externa, serosa (visceral peritoneum)
Histology of the alimentary canal wall; four major/general layers from inner to outermost
Mucosa
innermost layer of GI tract; mucous membrane; three specific layers – lining epithelium, lamina propria, muscularis mucosae
Simple columnar epithelium
specific epithelium tissue component of lining epithelium of most of digestive tract, including stomach, small intestine, large intestine
Stratified squamous epithelium
specific epithelium tissue component of mouth, most of pharynx, esophagus due to greater physical abrasion from food
Lining epithelium, lamina propria, muscularis mucosae
three specific sublayers of mucosa
Lining epithelium
specific layer of mucosa; lines actual lumen of the GI tract so has direct contact with food; specific epithelial tissue component is simple columnar epithelium
Lamina propria
specific layer of mucosa; connective tissue positioned deep to lining epithelium; contains most of mucosa-associated lymphoid tissue (MALT) which defends against invasion by bacteria and other microbes in GI tract
Mucosa-associated lymphoid tissue (MALT)
tissue that defends against invasion by bacteria and other microbes in the GI tract
Muscularis mucosae
specific layer of mucosa; very thin layer of smooth muscle external to lamina propria
Submucosa
layer of GI tract; external to mucosa; consists of connective tissue
Musularis externa
layer of GI tract; external to submucosa; usually 2 sublayers-longitudinal and circular layer of smooth muscle; 3rd oblique layer present in stomach; contractions mix food in, and propel food through alimentary canal and provide for peristalsis
Longitudinal and circular layers
sublayers of smooth muscle tissue found in muscularis externa of GI tract
Oblique layer
third sublayer of smooth muscle tissue found only in stomach
Parasympathetic division of ANS via vagus nerve
how activity of smooth muscle in muscularis externa is increased thus enhancing digestive tract motility
Sympathetic division of ANS via vagus nerve
how activity of smooth muscle in muscularis externa is decreased thus inhibiting digestive tract motility
Serosa/visceral peritoneum
outermost layer of GI tract wall; has serous fluid that allows digestive organs to slide easily along one another and against wall of peritoneal cavity
Peritonitis
infection & inflammation of peritoneum; usually results from a burst appendix that leaks feces and bacteria into peritoneal cavity
Mesentery, greater omentum, falciform ligament
“special folds” of the peritoneum
Mesentery
sheet-like structure that fans inferiorly from the posterior abdominal wall like long, pleated curtains to support the long coils of the jejunum and ileum of small intestine
Greater omentum
attached to greater curvature of stomach from which it extends inferiorly to cover most of the front of the intestines like a lacy apron
Nerve plexuses in wall of alimentary canal
contain both parasympathetic and sympathetic components; psymp components stimulate digestive functions; symp components inhibit digestive functions
Myenteric nerve plexus, submucosal nerve plexus
nerve plexuses in wall of alimentary canal
Myenteric nerve plexus
nerve plexus of alimentary canal located in musularis externa where it controls smooth muscle activity esp. associated with peristalsis
Submucosal nerve plexus
nerve plexus of alimentary canal located in submucosa
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