intro to digestive Flashcards
typical recomended diet
500g carbs
125g proteins
50g lipids
50% veggies and fruits
25% whole grain foods
25% proteins
function of digestive systems
break down food to release thier nutrients and absorb those nutrients
GI tract includes
organs of the alimentary canal as well as accessory glandular tissues
alimentary canal
muscular tube made up of diff organs that coordinate their activity to move unidirectionally from mouth to anus
examples of the alimentary canal organs
mouth
pharynx
esophagus
stomach
small intestine
large intestine
anus
exocrine organs
lie outside the digestive tract and empty their secretions through ducts into the digestive tract lumen
example of exocrine organs
salivary glands
exocrine pancreas
biliary system
liver
gallbladder
what is the alimentary canal lined by
from outside in
serosa
muscularis
submucosa
mucosa
submucosa
anchors mucosa
connective tissue layer that anchors the epithelia to the rest of the alimentary canal
mucosa
contains:
epithelium
laminal propria
muscularis mucosae
direct contact with food
lines the alimentary canal
epithelial cell layer is directly in contact with food or chyme and physically separates the food from the inner environment of the body
organized diff based on part of the alimentary canal
muscularis mucosae
smooth muscle contracts the mucosa
circular muscle
longitudinal muscle
serosa
another layer of connective tissue which anchors GI tract to other organs in the body
areolar connective tissue
epithelium
what is the alimentary canal exposed to
the external enviroment
what protects the body from external assaults in the alimentary canal
GI tract barrier
tight junctions bw the epithelial cells
mucus and other secretion production by mucosa
what are the external assaults that might affect the alimentary canal
acidic pH of the somach
digestive enzymes
gut flora
what does the mucus secreted by epithelial cells and mucous cells do
serves as protective barrier against several forms of potential injury to the gastric mucosa
alkaline (basic)
also serves as padding from physical damage by sharp food
what are the types of cells that are joined by tight junctions- luminal membrane of the gastric mucosa
chief cell and parietal cell
what do the luminal membrane of the gastric mucosa do
impermeable to H+ so HCl cant penetrate
and mucus coating offers further protection
what are the four main GI functions
secretion
motility
digestion
absorption
GI function- secretion
digestive jioces are secreted into the digestive tract lumen by exocrine glands
gastrointestinal hormones help control digestive motility and exocrine gland secretion
GI function- motility
muscular contractions that mix and move forward the contents of the digestive tract through
propulsive movements that push the contents forward through the digestive tract
and
mixing movements facilitate the absorption by exposing intestinal contents to the absorbing surfaces of digestive tract
GI function- digestion
biochemical breakdown of complex foodstuffs into smaller absorbable units
large food molecules are converted to simple absorbable untis as the digestive tract contents are propelled forward
GI function- absorption
small absorbable units that result from digestion along with water, vitamins, and electrolyes are trasnferred from the digestive tract lumen into blood or lymph
mechanical and chemical digestion in the mouth
mechanical- chewing and swallowing
chemical- carbs and fats
mechanical and chemical digestion in the stomach
mechanical- perstaltic mixing and propulsion
chemical- proteins and fats
absorption- lipid soluble substances such as alchohols and aspirin
mechanical and chemical digestion in the small intestine
mechanical- mixing and propulsion primarily by segmentation
chemical- carb, fat, polypeptides, nuc acids
absorption- peptides, aa, glucose, fructose, fats, water, minerals, vitamins
mechanical and chemical digestion in the large intestine
mechanical- segmental mixing and propulsion
no chemical digestion exception by bacteria
absorption of ions, water, minerals, vitamins, and organic molecules
what are the 3 types of sensory receptors that respond to local changes in the digestive tract
chemoreceptors
mechanoreceptors
osmoreceptors
chemoreceptors
sensitive to chemical components within the lumen
mechanoreceptors
sensitive to stretch or tension within the wall
osmoreceptors
senstitive to the osmolarity of the luminal contents
regulation of digestion function and relation to the CNS
- duodenum fills with chyme
- sensory stretch receptors are stimulates
- sensory nerve impulses travel to central nervous system
- nerve impulses inhibit peristalsis in stomach wall
what do sensory receptors in digestive tract do and what do they trigger
monitor luminal content and wall tension
triggers neural reflexes or hormonal secretion to influence digestive effector cells
what are the digestive effector cells
smooth muscle cells
exocrine gland cells
endocrine gland cells
smooth muscle effector cells
modify gut motility
exocrine gland effector cells
secrete digestive juices
endocrine gland effector cells
secrete gastrointestinal hormones
local stimulus in digestive function
pH, stretch, osmolarity, products of digestion
external stimulus of digestive function
sight, smell, etc
