GI 1 Flashcards
what Primary function of digestive system
absorption of nutrients, water and electrolytes from the external environment into the body’s internal environment
what is the digestive system central to
regulation and integration of metabolic processes throughout body
what is proper functioning of digestive system necessary for
whole-body homeostasis
what % of health care costs related to GI system
10%
where does digestive system extend from
mouth -> large intestine
15ft in live person
what is the GI tract
long tube with muscular walls lined by transporting and secretory epithelial (esophagus to end)
order of the digestive system
mouth - pharynx - esophagus - stomach - small int - large int - external environment
stomach to anus
the gut
digestion
mechanical and chemical breakdown of food primarily occurs in gut
what contributes to digestion
secretions from accessory glandular organs
salivary glands, liver, gallbladder, pancreas
GI tract is technically what
a continuation of external environment
where does digestion begin
in mouth with mastification and addition of saliva
what are three salivary glands in mouth
parotid, sublingual, submandibular
what are the 4 functions of salivary glands
- moisten and lubricate food
- salivary amylase partially digests polysaccharides
- dissolve some food molecules (taste)
- lysozyme kills bacteria
esophagus
passageway from mouth to stomach
what is the esophagus made of
top 1/3 skeletal muscle (voluntary) bottom 2/3 smooth muscle
what sphincter are connected to esophagus
upper and lower esophageal sphincters
what does the esophagus do
moves food via perstaltic waves (just motility no digestion)
where does digestion continue after esophagus
stomach
what happens in stomach
mixes food with acid and enzymes to create chyme (lots of mechanical)
3 parts of stomach and the valve
- fundus (upper)
- body
- antrum (lower)
pylorus valve (sphincter)
where does majority of digestion and absorption take place
small intestines
what is the largest portion of digestive tract
small int 10-12 ft
What releases exocrine secretions into duodenum
liver and pancreas
3 parts of small intestine
- duodenum (first 25cm)
- jejunum
- ileum (combined 260cm)
what passes through the large intestine each day
1.5L of watery chyme
what happens in large int
not much digestion
water and electrolytes removed (absorption) to created semisolid feces
what triggers the defecation reflex
feces entering the terminal section of the large intestine (rectum)
5 parts of large int
cecum, ascending colon, transverse colon, descending colon, sigmoid colon
what is sphincter between ileum and large int
ileocecal sphincter (valve)
what are the sphincter in the rectum
internal anal sphincter (involuntary, smooth muscle)
external anal sphincter (voluntary, skeletal)
4 GI layers from lumen to abdominal cavity
mucosa, submucosa, muscularis externis, serosa
3 layers of mucosa
epithelium
lamina propria
muscularis mucosa
what are two nerve networks of the ENS
submucosal plexus
myenteric plexus
what is surface area increased by in the stomach
gastric glands (invaginations)
rugae (microscopic gastric folds)
what is the small intestine’s surface area increased by
villi
crypts (invaginations)
plicae (large foldings)
what does the epithelium include
transporting epithelial cells (enterocytes in sm int), endocrine and exocrine secretory cells
what part of mucosa is most variable
epithelium
what are difference in junctions
very tight in stomach and colon, leaky in small intestine (more absorption)
why do GI stem cells have to constantly produce new cells
epithelia have short lifespan
~17 billion replaced daily
what is the lamina propria of mucosa
subepithelial tissue containing nerve fibres, small blood vessels, and lymph vessels
what is the muscularis mucosae of the mucosa
thin layer of smooth muscle that can alter the surface area available for absorption
what is the submucosa
middle distensible layer containing large vessels (lymph +blood) and submucosal plexus
muscularis externa
2-3 layers of smooth muscle and myenteric plexus
- circular decrease diameter, longitudinal shortens tube
what does the myenteric plexus do
controls the smooth muscle (in between 2 layers)
serosa
outer covering of dense connective tissue that is continuation of peritoneal membrane, sheets of mesentery hold intestines in place
digestion
chemical and mechanical breakdown of food into absorbable units
secretion
movement of material from cells into lumen or ECF OR movement of water and ions from ECF to lumen
absorption
movement of material from GI lumen to ECF
motility
movement of material through the GI tract as result of muscle contraction
