Digestive System: Colon, Accessory Organs, and Pathology

Explain the length and location of the large intestine (colon)

~5 ft long; begins at the ileocecal valve (RLQ) and surrounds the small intestine

What is a by product of the bacterial fermentation in the GI system?

flatulence (CO₂ and methane produced)

What % of absorption takes place in the colon?

80% of water absorption

What are taeniae coli?

longitudinal muscles that aid in pushing the waste bolus into the rectum for excretion

What are haustra?

lumps in the large intestine

Where is the liver located?

RUQ

What is the part of the liver that separates it into the 2 lobes called?

falciform ligament

What is the main digestive function of the liver?

production of bile

What is the function of bile? What is it made up of?

breaks down fats; made up of water, salts, bilirubin, and cholesterol

What is the function of the gallbladder?

stores, secretes, and concentrates (absorbs 90% of water) bile

Explain what happens with bile after a fatty meal

• cholecystokinin is secreted by cells in the duodenum that stimulates gallbladder to contract

• bile is then secreted

What are Kupfer cells?

macrophage cells involved in the destruction of bacteria and other harmful organisms that lie on the lining of the liver (kill pathogens coming from the bowel to the liver)

Explain the endocrine and exocrine functions of the pancreas

endocrine

• ductless

• secretes insulin directly into the bloodstream to control sugar levels

exocrine (digestive function)

• ducts

• secretes pancreatic juice/enzymes

• contains enzymes that digest food

• neutralizes HCl acid from the stomach

The right and left hepatic ducts join together to form the ___

common hepatic duct

The gallbladder drains into the ___

cystic duct

The cystic duct and the common hepatic join together to form the ___

common bile duct

Before exiting into the duodenum, the common bile duct joins to the ___

pancreatic duct

The common bile duct and pancreatic duct eventually go through the ___ and ___

ampulla of Vater (hepatopancreatic duct) and sphincter of Oddi

Explain Barrett’s esophagus

• occurs when the cells in the esophagus begin to change due to chronic exposure to acid

  • from reflux

• precancerous disease

What pathology is shown here?

Barrett’s esophagus

Explain Zenker’s diverticulum

• occurs mostly in the elderly

• excessive pressure within the lower pharynx, causing the weakest portion of the pharyngeal wall to balloon out, forming a diverticulum

• results in dysphagia, cough, halitosis

What pathology is shown here?

Zenker’s diverticulum

Explain paraesophageal hiatal hernia

• hernias in which the GE junction stays where it belongs, but part of the stomach bulges into the chest beside the esophagus

• 1% of hiatal hernias

• causes ischemia (impeded blood supply)

• caused by muscle weakness, obesity, pregnancy, trauma

Explain sliding hiatal hernia

• stomach and the GE junction slide up into the chest through the hiatus

• 99% of hiatal hernias

• caused by muscle weakness, obesity, pregnancy, trauma

What pathology is shown here?

paraesophageal hiatal hernia

What pathology is shown here?

sliding hiatal hernia

Explain duodenal and gastric ulcers

• “peptic ulcers”

• open sore of mucosa

• caused by infection, inflammation, or substance (tobacco, coffee, aspirin, NSAIDs) which erodes mucosa

Explain duodenal atresia

• “closing off” of the duodenum

• congenital disease where the duodenum has not developed properly

  • not open and cannot allow the passage of stomach contents

  • atresia is usually just distal to ampulla of Vater

  • about 30% of children with duodenal atresia will have down syndrome

• double bubble sign

What pathology is shown here?

duodenal atresia

Explain esophageal varices

• increased pressure in liver causes varicose veins in esophagus

  • pressure due to deteriorated function of liver, often from cirrhosis

  • scar tissue forms, interfering with liver function

• radiographic image demonstrates filling defects

  • wormlike or cobblestone appearance

• bleeding is a major complication

What pathology is shown here?

esophageal varices

Explain small bowel obstruction

• the most common cause is adhesions secondary to abdominal surgery

• radiographically dilated loops of bowel and air fluid levels

• paralytic

  • adynamic bowel obstruction due to paralyzed bowel muscles

• mechanical

  • dynamic bowel obstruction arising from a mechanical cause/foreign body

What are the two types of mechanical ileus?

volvulus: coffee bean sign, twisting upon itself

intussusception: crescent sign, collapsing upon itself

What pathology is shown here?

volvulus

What pathology is shown here?

intussusception

Explain pyloric stenosis

• hypertrophy and hyperplasia of muscle in the pyloric canal

• most common in newborns

• causes projectile vomiting, not tolerating food, continuous crying

• “string” sign

What pathology is shown here?

pyloric stenosis

Explain colon polyps

• growth on the inside lining

• more common as people age

• can become cancerous

• routine screenings after age 50

Explain colon diverticula

• outpouchings on the intestinal wall

• most common area is sigmoid colon due to increased pressure

What pathology is shown here?

colon polyps

What pathology is shown here?

diverticula

Explain colorectal carcinoma

• constriction of the lumen of the colon

• most commonly at the rectum

• apple core sign

What pathology is shown here?

colorectal carcinoma

Explain cirrhosis

• healthy liver tissue is replaced with scar tissue

• prevents liver from functioning properly

  • scar tissue blocks the flow of blood

• causes jaundice, increased liver pressure, esophageal varices

• caused by alcoholism, hep C, hep B

What pathology is shown here?

cirrhosis (of the liver)

What are the 3 types of gastric bypass surgery?

• Roux-en-Y gastric bypass

• sleeve gastrectomy

• laparoscopic gastric banding

Explain the Roux-en-Y gastric bypass surgery

• small stomach pouch

• jejunum is cut and attached to new pouch, bypassing the duodenum

• the portion of the intestine still attached to the main stomach is reattached farther down (allows digestive juices to flow)

• limits amount of food eaten: REDUCES ABSORPTION OF CALORIES AND NUTRIENTS

What is the most invasive of the gastric bypass surgeries?

Roux-en-Y

Explain the sleeve gastrectomy gastric bypass surgery

• part of the stomach is separated and removed from the body

• the remaining section of the stomach is formed into a tubelike structure

• smaller stomach cannot hold as much food, but DOES NOT AFFECT ABSORPTION OF CALORIES AND NUTRIENTS

Explain the laparoscopic banding gastric bypass surgery

• a band containing an inflatable balloon is placed around upper stomach

• adjustable, non-permanent port is placed under skin

• restricts amount of food eaten, but DOES NOT AFFECT ABSORPTION OF CALORIES AND NUTRIENTS

What is the least invasive of the gastric bypass surgeries?

laparoscopic banding

Which type of gastric bypass is shown?

Roux-en-Y

Which type of gastric bypass is shown?

sleeve gastrectomy

Which type of gastric bypass is shown?

laparoscopic banding