Flashcards in 9.3 Bowel Deck (35):
What are the regions of the large intestine?
Cecum – blind-ended pouch, connected to ileum via ileocecal valve
Appendix – hangs from the cecum, helps support good bacteria, immune function
Ascending colon – travels up the right side
Transverse colon –travels across the cavity
Descending colon -travels down the left side
Sigmoid – s-shaped portion, travels posteriorly into the pelvis
Rectum – anterior to the sacrum and coccyx, controlled via rectosigmoid sphincter
Anal Canal – exit point, controlled via internal and external anal sphincters
What is the function of the appendix?
What type of immune tissue?
=safehouse for beneficial bacteria, due to placement, avoids flow of feces, immune component allows recolonization of gut microbiome/”good” bacteria
How does the large intestine increase surface area? Fxn?
crypts: folds for increased surface area
active absorption of Na+, water and Cl- follow, K+ lost in feces when Na+ absorbed
What are the 2 types of motility in the large intestine?
Haustral contractions (“haustrations”) are ring-like contractions at a rate of 1 every 30 minutes, mixing and kneading of contents
increased contact with mucosal surface for absorption
triggered by parasympathetic input
Mass Movements are contractions of large segments of the colon at a rate of 3-4 per day
What triggers mass movements?
Triggered by CCK, secretin, gastrin release during gastrocolic reflex as food enters stomach to make room for incoming food
inhibited by sympathetic nervous system
What are the sphincters of the anus?
Internal involuntary sphincter: smooth muscle
External voluntary sphincter: skeletal muscle
What is the defication reflex?
How is it controlled?
controls elimination of stool from large intestine
sigmoid colon and rectum wall stretch detected -> “urge” to defecate
involuntary contraction of rectum, relaxation of internal anal sphincter
voluntary control of external anal sphincter can override, or allow release contents
Sacral spinal cord:
promoted by pelvic splanchnic nerves (parasympathetic)
inhibited by sacral splanchnic nerves (sympathetic)
What is the difference between Chron's and Ulcerative Colitis at a tissue level?
Chron’s- “cobblestoning” of mucosa/submucosa
UC-Large intestine only, polyps common, precursor to Ca
What is colitis?
Irritable Bowel Syndrome (IBS, “colitis”) is altered bowel activity, increased pain sensitivity with no evidence of inflammation or mucosal changes
abdominal pain > 6 months, constipation and/or diarrhea, increases with eating, decreases with bowel movement
also: anxiety, mucus stools, nausea, vomiting, abdominal distension, flatulence
physical exam is normal
rule out other conditions, esp. with weight loss, anemia, family history, rectal bleeding, age >50, nocturnal symptoms
NOT Inflammatory Bowel (Crohn’s Disease or Ulcerative Colitis)
What are diverticula, diverticulosis, diverticulitis?
Diverticulosis= multiple diverticula exist
Diverticulitis- inflammation of diverticula
In the digestive system, what is the function of the liver, gallbladder, and pancreas?
Pancreas- produces enzymes and bicarbonate
Liver- produces bile
Gallbladder: stores bile from liver
What is in the portal hepatsis?
Hepatic portal vein
Hepatic artery proper
Common bile duct
What is the flow of blood to/from the liver?
Hepatic portal vein
What is the portal triad?
branch of hepatic portal vein
branch of hepatic artery
What are Kupffer cells and hepatic stellate cells?
Kuppfer cells: macrophages that line the sinusoids, detoxify blood
hepatic stellate cells: respond to liver damage, fibrosis, lipid accumulation
What is the path of bilirubin? From RBC out of the body
RBC-> Fe+ and unconjugated bilirubin
Liver conjugates bilirubin
Conjugated bilirubin excreted in bile
bilirubin -> urobilinogen (exerted in urine)
OR urobilinogen ->stercoblinogen (turns poop brown) excreted as feces
How does the liver regulate blood?
Albumin production-> osmolarity
and many more
How does the liver impact fat metabolism?
bile production for fat emulsification (helps with digestion)
lipolysis: convert free fatty acids to ketones
How does the liver impact protein metabolism?
deamination of proteins (nitrogen group removal)
ammonia (NH3) production, converted to urea in blood, excreted in urine
How does the liver impact carbohydrate metabolism?
glycogenesis: forming glycogen from glucose
glycogenolysis: breakdown of glycogen
gluconeogenesis: form glucose from amino acids and glycerol
What is enterohepatic recycling of bile?
bile salts are reabsorbed from the ileum, returned to the liver via hepatic portal circulation
What are micelles and chylomicrons?
Micelles are water-soluble transport vesicles formed by bile salts and lecithin
Chylomicrons are large particles of fat-soluble substances made from micelle contents that move from the small intestinal epithelium to the Lacteals of the Lymphatic system
What is the path of bile from bile cannaliculi to the gallbladder? From gallbladder to intestine?
Cannaliculi empty at portal triad from L or R hepatic duct, to
Common hepatic duct, to
Cystic duct, to Gallbladder, to
Cystic duct, to
Common bile duct, to
Hepatopancreatic ampulla in the duodenum
What is the hepatopancreatic sphincter?
Hepatopancreatic sphincter (Sphincter of Oddi) where common bile duct enters lumen of duodenum
empties bile from the liver
digestive enzymes from the pancreas
What is cholestatis? Sx?
backup of bile
accumulation of unconjugated bilirubin in bloodstream
dark-colored urine (bilirubin in urine)
What is hyperbilirubinemia?
Increased breakdown of red blood cells, or decreased elimination by the liver can cause excessive bilirubin levels hyperbilirubinemia
bilirubin -> yellow in color, adheres to connective tissues, especially skin and sclera of the eye
yellow toned skin & sclera -> jaundice
What are the causes of Hep A?
contaminated food or water, fecal-oral contamination
routine vaccination in U.S
What are the causes of Hep B?
sexually transmitted, blood-borne, body fluid exposure
routine vaccination in U.S
5-10% of cases can lead to end-stage, chronic liver disease
What are the causes of hep C?
blood-borne, needle-stick and drug use exposure
70% becomes chronic, 20-50% develop cirrhosis (fibrosis and scar tissue)
can lead to liver failure, liver cancer
What are the causes of Hep D?
similar to HepB, transmitted via blood, sexual contact, IV drug use
What are the causes of Hep E?
What causes cirrhosis? Sx?
fibrosis (collagen) and scar tissue build up, irreversible damage to liver, final stage of liver injury
3rd most common cause of death in U.S
Causes: alcoholic liver disease, non-alcoholic fatty liver disease, chronic hepatitis, biliary dysfunction
stellate cells activated and produce collagenous fibrous tissue
constricts portal circulation
back up of pressure in intestine, spleen, pancreas, stomach, esophagus
prone to rupture hematemesis from esophageal veins, rectal bleeding
caput medusa: over time, dilated veins around umbilicus may be visible
increases density of liver
What is the cephalic phase of digestion?
The Cephalic Phase refers to the time when the brain expects food to enter the stomach: thinking about, seeing, smelling, tasting, chewing, swallowing food
PSNS (Vagus nerve -> acetylcholine):
Increases HCl, increases pepsinogen
Increase pancreatic juices
Increase liver secretion of bile
What is the gastric phase of digestion?
The Gastric Phase refers to the time when food first enters the stomach, stretch of the stomach wall with food or fluids, high protein content
Stimulates gastric pits to produce more gastric juices
Stimulates gastric pits to release gastrin, histamine, mucous, HCl, intrinsic factor
Stimulates PSNS (Vagus)
Opens ileocecal valve
Gastrocolic reflex: Stimulates mass movements in large intestine