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
