Chapter 9- The Digestive System Flashcards
2 types of digestion
- intracellular- metabolism, oxidation of glucose and fatty acids for energy.
- extracelluar- process by which nutrients are obtained from food (occurs in lumen on alimentary canal- mouth to anus)
sphincters
circular smooth muscles around the canal that can contract to allow compartmentalization of function. sections off the alimentary canal (mouth to anus)
mechanical vs. chemical digestion
m- physical breakdown of large food particles into smaller ones.
c- enzymatic cleavage of chemical bonds
absorption
transport of products of digestion from digestive tract into the circulatory system for distribution to the body’s tissues and cells.
digestive tract order
oral cavity–> pharynx–> esophagus–> stomach–> small intestine–> large intestine–> rectum
other helper organs include: salivary glands, pancreas, liver, gallbladder
enteric nervous system
collection of 1hundredmillion neurons that governs the function of the GI system. neurons are present in walls of digestive tract and trigger peristalsis (rhythmic contractions of gut to move materials through system)
what hormone triggers the sensation of thirst?
ADH and aldosterone (encourage behavior of fluid consumption)
ghrelin
secreted by stomach and pancreas (stimulates feelings of hunger)
leptin and cholecystokinin
stimulate feelings of satiety (feeling full)
mastication
chewing
salivary amylase
aka: ptyalin. hydrolyzes starch into smaller sugars. (found in saliva)
lipase
catalyzes hydrolysis of lipids (found in saliva)
3 parts of pharynx
- nasopharynx- behind nasal cavity
- oropharynx- back of mouth
- laryngopharynx- above vocal cords
emesis
reversal of peristalsis, vomiting
upper esophageal sphincter
swallowing is initiated here (muscles of the oropharynx)
lower esophageal sphincter
cardiac sphincter. relaxes and opens to allow the passage of food into the stomach
4 main anatomical divisions of stomach
1/2. fundus/ body, which have mainly gastric glands
3/4. antrum/ pylorus, which contain mostly pyloric glands
gastric glands
respond to signals from the vagus nerve of the parasympathetic nervous system. 3 types of cells here: mucous, chief, and parietal
mucous cells of gastric glands
produce bicarbonate-rich mucus that protects the muscular wall from harsh stomach environment
chief cells and parietal cells of gastric glands
gastric juice is a combo of secretions from these two.
chief- secrete pepsinogen
parietal- secrete H+ions in form of HCl, intrinsic factor
pepsin
digests proteins by cleaning peptide bonds near aromatic amino acids resulting in short peptide fragments. activated by acidic environment
intrinsic factor
glycoprotein secreted by parietal cells. absorption of vitamin B12
stomach secretes 6 products
HCl (kill microbes, denatures proteins), Pepsinogen (cleaved to pepsin then digests proteins), mucus (protects mucosa), bicarbonate (protects mucosa), water (dissolves/dilutes ingested material), intrinsic factor (B12 absorption)
pyloric gland
contain G cells that secrete gastrin (peptide hormone that induces parietal cells in the stomach to secrete more HCl and signals stomach to contract to mix its contents)
chyme
digestion of solid food in stomach results in this acidic semifluid mixture
2 substances absorbed directly from stomach
alcohol and aspirin
3 segments of small intestine (in order)
- duodenum (major chemical digestion and minor absorption)
- jejunum (absorption)
- ileum (absorption)
pyloric sphincter
sphincter between stomach and duodenum