Structures and Functions of the Gastrointestinal System Flashcards
What are Etiologies of GI disorders?
-structural abnormality
-gut perfusion
-gut motility
-nutrient absorption
-neoplasia
What are the types of structural abnormalities?
-congenital
-acquired (disease or surgery)
-traumatic
Where are nutrients absorbed in the GI system?
small bowel (intestine)
What are the functions of the GI system?
-ingestion, digestion, and absorption of nutrients
-elimination of wastes
-protection of immunity
What is ingestion?
taking in food
What is digestion?
breaking food down into nutrients
What is absorption?
taking in nutrients by cells
What is excretion?
elimination of metabolic waste
What are the digestive organs?
mouth, pharynx, esophagus, stomach, small intestine, large intestine
What is GI motility?
the movement of food and fluid through the length of the GI tract
What does the enteric nervous system control?
the GI tract with influences from the autonomic nervous system and nerve fibers within the local structures
How many layers are in the stomach?
3 layers of smooth muscle
What is the stomach lined with?
mucosa that serves as a protective barrier
What are the two sphincters of the stomach?
cardiac/esophageal and pyloric
What does the cardiac sphincter do?
tight muscle keeps stomach acid from regurgitating back up in esophagus
What does the pyloric sphincter do?
Regulates the movement of food and stomach acids into the small intestine
What produces gastric juice?
HCL, pepsin, mucus
What does hydrochloric acid do?
-breaks down food
-destroys invading bacteria or viruses
-converts pepsinogen made in gastric cells, into pepsin
What does pepsin do?
breaks down proteins
What does mucus do?
protects stomach lining from the hydrochloric acid it produces
What is mechanical digestion?
churning of food into chyme; breakdown of food into smaller particles without any molecular change
What does the stomach secrete?
intrinsic factor from parietal cells in mucosa lining to absorb Vitamin B12 in the ileum of small bowel
Intrinsic factor + Vitamin B12=
RBC
What is chemical digestion?
bigger molecules are dismantled into smaller molecules which become a different structure
Increased motility and secretions of GI tract is a result of what?
parasympathetic stimulation through the vagus nerve
What does sympathetic stimulation do to GI motility?
decreases
What leads to decreased peristalsis?
decreased GI motility due to sympathetic stimulation
What does pyloric sphincter prevent?
back flow of highly acidic gastric contents that have passed into duodenum
What are examples of gastric motility disorders?
-gastroparesis
-dumping syndrome
-pyloric stenosis
Gastroparesis
stomach emptying is too slow or absent
Dumping Syndrome
consumed contents pass into small bowel too quickly
Pyloric stenosis
tight pyloric valve prevents food from passing out of the stomach into the duodenum (can be congenital in infants and requires surgery)
What are the 3 parts of the small intestine?
duodenum, jejunum, ileum
What is the duodenum?
-contains openings for bile duct and main pancreatic duct
-bile and pancreatic fluid enter intestine through ducts
What is the jejunum?
-food is digested and majority of absorption occurs here
-digested nutrients are absorbed through intestinal walls
What is the ileum?
-food is digested and absorbed
-compacts the leftover to pass through to large intestine
What is the normal pH of large intestine?
6.5-7.5
What is a major function of the large intestine?
water absorption from waste material
What Vitamins are produced by intestinal bacteria?
Vitamin B and K
What happens to the leftover waste in the large intestine?
it is compacted and stored in rectum
What happens when rectum is full and sphincter relaxes?
waste is eliminated
What is the major metabolic function of microflora in the colon?
fermentation of indigestible food and other digestible dietary residue
Which colonic microorganisms play a role in vitamin production and absorption?
-calcium
-magnesium
-iron
What do colonic microorganisms do?
provide a crucial line of defense against microorganisms that are consumed
What does the use of large amount board spectrum antibiotics allow?
overgrowth of potential harmful pathogens- clostridium difficile
What is the GI tract a main site for?
the internal body’s contact with the external world
What does the GI tract consume?
essential food and microbes, but also possible pathogenic organisms
What is the stomach fluid pH?
1-4
What is intestinal mucosa?
a physical, biochemical, and immune barrier
What does intestinal tissue (Peyer’s patches) contain?
immune cells including lymphocytes that protect against harmful consumed substances
What does amylase in saliva do?
breaks down ingested starches into disaccharides
What do disaccharides do?
digest disaccharides to monosaccharide by more amylase from the pancreas in the small bowel
What happens when disaccharides are not broken down to monosaccharides?
they cannot be absorbed and remain active causing diarrhea
Deficiency of lactase to breakdown lactose causes what?
diarrhea when eating dairy products
What is emulsification?
break down of large fat globules into smaller sizes
What is Steatorrhea?
fatty stools (indicates fat not absorbed)
What do water-soluble enzymes act on?
fat in the stomach and continues in the duodenum with bile from the liver (breaks down fat)
Is fat used for immediate energy?
no, it is stored as triglycerides
What does elevated triglycerides mean?
calorie intake higher than body need
Where does protein digestion begin?
in the stomach due to action of pepsin that breaks down in tact proteins into smaller amino acid chains called peptides
Enzymes from the pancreas travel to the duodenum to do what?
mix with chyme to break down peptides to amino acids
What absorbs amino acids into the blood?
the small bowel
What controls the delivery of amino acids to various body sites?
the liver
