9.3 Bowel Flashcards
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
Lymphoid, IgA
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
drives defecation
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?
Muscle type?
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?
Diverticula=pouch
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 Liver Sinusoids Central Veins Hepatic Veins IVC
What is the portal triad?
branch of hepatic portal vein
branch of hepatic artery
bile duct
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
Clotting factors
Thrombopoetin- platelets
and many more
How does the liver impact fat metabolism?
cholesterol production
bile production for fat emulsification (helps with digestion)
lipolysis: convert free fatty acids to ketones
How does the liver impact protein metabolism?
protein synthesis
proteolysis (breakdown)
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
