GI 1 Flashcards
what is the primary function of the GI system?
-move nutrients, water and electrolytes from the external environment into the body’s internal environment
what is the introduction to the GI system?
-central to regulation and integration of metabolic processes throughout the body
-proper functioning necessary for whole-body homeostasis
-10% of health care costs related to GI system
what is digestion?
-mechanical and chemical breakdown of food primarily occurs in the gut
what is the GI tract technically?
-continuation of external environment (bacteria)
how big is the digestive system?
-extends from mouth to large intestine (15ft length)
what is the gut?
stomach to anus
what is the GI tract?
-a long tube with muscular walls lined by transporting and secretory epithelial
what is the digestive system joined by?
joined by secretions from accessory glandular organs
-salivary glands, liver, gallbladder, pancreas
where does digestion begin?
-in the mouth with mastication and the addition of saliva
-three salivary glands with multiple functions
what are the functions of salivary glands?
-moisten and lubricate food
-amylase partially digests polysaccharides
-dissolve some food molecules (taste)
-lysozyme kills bacteria
what is the esophagus?
passageway from mouth to stomach
-upper and lower esophageal sphincters
-wall: top 1/3 is skeletal muscle, bottom 2/3 smooth muscle
-moves food via peristaltic waves
what happens when digestion continues to stomach from esophagus?
mixing food with acid and enzymes to create chyme
what is the small intestine?
-majority of digestion takes place here
-liver and pancreas release exocrine secretions into the duodenum
what is the large intestine (colon)?
-large diameter but short (150cm)
-1.5L of watery chyme pass into here each day
-water and electrolytes removed to create semisolid feces
-feces entering the terminal section of the large intestine (rectum) trigger a defecation reflex
what are GI layers?
-basic structure of GI wall is similar in both the stomach and intestines with slight variations from one section to another
what is the graph of GI layers?
what is mucosa graph of stomach?
what is mucosa graph in small intestine?
what is epithelium (mucosa)?
most variable
-include transporting epithelial cells (enterocytes in small intestine), endocrine and exocrine secretory cells
-junctions very tight in stomach and colon, leaky in small intestine
-short lifespan (a few days), GI stem cells constantly producing new cells (17 billion replaced daily)
what is lamina propria (mucosa)?
-subepithelial tissue containing nerve fibers, small blood vessels and lymph vessels
what is muscularis mucosae?
-thin layer of smooth muscle that can alter the surface area available for absorption
what is the submucosa?
-middle distensible layer containing larger vessels (lymph and blood) and the submucosal plexus: one of the major nerve networks in the enteric nervous system
what is the muscularis externa and serosa?
-muscularis externa: 2 or 3 layers of smooth muscles: circular diameter, longitudinal shortens the tube. contains myenteric plexus
-serosa: outer covering of connective tissue that is a continuation of the peritoneal membrane, sheets of mesentery hold intestines in place
what are the digestive functions and processes?
what are the challenges of the digestive system?
-avoiding autodigestion
-defense
what is avoiding autodigestion?
-breaking food down into small enough molecules to be absorbed without digesting the cells of the GI tract
what is the defense challenge?
absorbing water and nutrients while preventing bacteria, viruses and other pathogens from entering the body
-mechanisms include mucus, digestive enzymes, acid and the largest collection of lymphoid tissue
-80% of lymphocytes in small intestine
