Digestive System Flashcards
What is the alimentary canal (gastrointestinal tract)?
continuous open-ended hollow muscular tube tat extends from the laryngeal pharynx to the anus (terminal)
What are the digestive accessory organs?
teeth, tongue, salivary glands, liver, pancreas
Path of digestive system?
Oral cavity➡️oral pharynx➡️laryngo-pharynx➡️esophagus➡️stomach➡️small intestines (duodenum, jejunum, ileum) ➡️large intestines (cecum, ascending colon, transverse colon, descending colon, sigmoid colon) ➡️rectum ➡️anus (<30 feet long altogether).
4 functions of the digestive system?
Motility
secretion
digestion
absorption
What is motility?
food is mixed with digestive juices through smooth muscle contractions and moved down.
contractions are regulated by intrinsic and extrinsic signals (NS)
What is secretion?
release of mucus, enzymes and other digestive secretions (H+ and HC03-)
What is digestion?
breakdown of large molecules (proteins, starches) into small ones (amino acids, glucose)
What is absorption?
nutrients crossing into vessels and lymph (into internal environment)
What are the four main layers of tissue throughout the GI tract?
serosa
muscularis
submucosa
mucosa
What is serosa?
external wrapping of GI tract (connective tissue and lubricates)
What is muscularis?
smooth muscle layers for mobility
What is submucosa?
has glands, autonomic nerves and blood vessels
What is mucosa?
inner lining made of simple columnar epithelium (in contact with lumen)
Where does digestion begin?
in the mouth with chewing
What do salivary glands do?
secrete mucus in the oral cavity that moistens and lubricates food before swallowing
What does saliva contain?
amylase (breaks down starch) and lysosyme (anti-microbial enzyme)
Purpose of stomach?
secretes HCl. when this mixes with food, it forms gastric chyme.
Pepsin in released into stomach
hollow bag which stores contents of meal.
(produces acid + pepsin)
What happens in small intestine?
motility of small intestine mixes the chyme and moves it towards the colon
digestion and absorption of nutrients
pancreas and liver ass their digestive secretions to the duodenum
What does the large intestine (colon) do?
reabsorb water and minerals before excretion
What are the accessory glands?
liver, gallbladder, pancreas
What part of the small intestine receives pancreatic juices and bile from the liver?
duodenum
What is cystic fribosis?
pancreatic duct gest blocked, no more lipase (enzyme digest lipids).
high risk of vitamin A, D, E, K deficiencies
common in caucasians
What is the only digestive muscle in the thoracic cavity?
esophagus
What makes up the large intestine?
duodenum+jejunum+ileum
Where is almost all of the digestive system locates?
abdominal cavity
Exocrine function of the pancreas?
secretes digestive enzymes in the duodenum
amylase, protease, lipase, nuclease
What does the liver do?
produces bile
breakdown products from hemoglobin
What is bilirubin?
molecule in bile. Too much causes jaundice
What does bile do?
emulsifies fat
What does pepsin do?
digest protein
What do the special cells in the stomach do?
produce intrinsic factor which bind to vitamin B12 and allows absorption in body
Lack of B12 causes what?
pernicious anemia
Vitamin A?
night vision
Vitamin B12?
synthesis of RBC
Vitamin D?
bones
Vitamin E?
antioxidants
Vitamin K?
blood coagulation
What does the large intestine do?
dry out food by absorbing water and eliminate the residue through feces
caecum, appendix, colon, rectum, anal canal
What is digestion in duodenum?
Chemical hydrolysis of polymers to monomers
What is secretion?
Release of various digestive juices from the lumen of the GI
What is absorption in jejumen?
Nutrients moving from GI lumen to blood vessels
What is excretion (extrection)
Minor components which are undigestible
Functions of the stomach?
Production of HCl
Synthesis of intrinsic factor (binds to vit. B12 [red cell synthesis] and allows absorption in ileum
Production of protease enzyme (pepsinogen which becomes pepsin when in contact with HCl and is then activated
Is there absorption in the stomach?
Little to none
Where does chemical digestion of starch start?
Mouth
Parts of the small intestine?
Duodenum, jejunum, ileum
Function of the small intestine?
Longest stretch of the GI tract
Most active organ in digestion and absorption
Release internal signals (local hormones) to regulate the organs in close proximity
What does the duodenum do?
Receives digestive juices from accessory glands (liver, pancreas, gallbladder)
Function of pancreas?
Releases various enzymes (bicarbonate ion, neutralize HCl)
What does bile do?
Emulsifies fat
Product of bilirubin from hemoglobin
Contains bicarbonate (HCo)
What is the function of the gallbladder?
Concentrates bike and removed water out of bile
What hormones are produced by the duodenum?
GIP (gastric inhibitory peptide): slows down the rate of gastric emptying. Travels through blood vessels
CCK (cholecystokinin): stimulates pancreas, liver and gallbladder. Travels through blood vessels
What is the function of the large intestine?
Reabsorbs remaining water trough osmosis by absorbing Na+ and Cl- (absorbs water and salt)
Has 4 distinct segments
What are the segments of the large intestine?
Ascending colon Transverse colon Descending colon (feces) Sigmoid colon (leads to rectum) Rectum
