NURS 1114: The Digestive System

Major organ responsible for digestion and absorption, measuring 2-4 meters long.
Subdivided into three parts: Duodenum, Jejunum, and Ileum.
Duodenum is approximately 25 cm long, receives bile and pancreatic enzymes at the major duodenal papilla, regulated by the hepatopancreatic sphincter.
Jejunum extends 2.5 meters and the Ileum is about 3.6 meters long, connecting to the large intestine at the ileocecal valve.

Circular folds (plicae circulares) enhance nutrient absorption surface area.
Villi are fingerlike projections containing absorptive cells (enterocytes) and goblet cells that secrete mucus.
Microvilli form a brush border to further increase absorption efficiency, housing enzymes for digestion.

Contain secretory cells producing intestinal juice and enteroendocrine cells that secrete hormones like secretin and CCK.
Intraepithelial lymphocytes (IELs) release cytokines for immune defense, while Paneth cells secrete antimicrobial agents.

Mechanical digestion occurs through segmentation and peristalsis.
Chemical digestion involves approximately 2 liters of daily secretions enriched with bicarbonate, neutralizing stomach acid.
Enzymes include maltase, sucrase, lactase, and peptidases that break down carbohydrates and proteins.

Functions as both an exocrine and endocrine gland, producing digestive enzymes and bicarbonate to regulate pH.
Key enzymes include pancreatic lipase, amylase, and proteases which contribute to the digestion of fats, carbohydrates, and proteins.

Carbohydrates are absorbed as monosaccharides entering the capillary bed and transported to the liver via the hepatic portal vein.
Proteins are absorbed as amino acids, similarly traveling to the liver.
Fats, particularly fatty acids and monoglycerides, diffuse into cells, reform into chylomicrons, and enter the lymphatic system.

Measures around 1.5 meters long and has a larger diameter than the small intestine.
Absorbs water and eliminates indigestible substances as feces.
Consists of key structures: cecum (with appendix), colon (ascending, transverse, descending, sigmoid), rectum, and anus.

Teniae coli and haustra form, allowing contraction and forming pouches.
Contains a rich supply of goblet cells for mucus secretion, aiding in fecal passage.

The largest gland in the body, responsible for over 500 functions, including bile production.
Comprised of four lobes: right, left, caudate, and quadrate; divided by the falciform ligament.
Hepatic portal vein and hepatic artery converge at the porta hepatis, where bile ducts form.

Composed of liver lobules, the fundamental units that filter nutrient-rich blood.
Portal triads at each lobule corner include a bile duct, portal arteriole, and hepatic venule.
Hepatocytes perform various functions including nutrient processing, detoxification, and bile production.

Synthesize blood proteins, store vitamins, detoxify substances, and regenerate efficiently.
Produce around 900 ml of bile daily, which is essential for fat digestion.

Regulated autonomously by the central nervous system, involving smooth muscle contraction to expel stool.

No digestive enzymes produced; nutrient digestion mainly through resident bacteria, yielding vitamins K and B.
Water and soluble nutrients absorbed, with excess materials eliminated as feces.### The Gallbladder
Thin-walled muscular sac located on the liver's ventral surface.
Stores and concentrates bile by absorbing water and ions.
Releases bile through the cystic duct into the bile duct.
Cholecystokinin (CCK) is released from enteroendocrine cells upon detection of fatty chyme.

Yellow-green, alkaline solution composed of bile salts, bilirubin, cholesterol, neutral fats, phospholipids, and electrolytes.
Bile salts are cholesterol derivatives essential for fat emulsification and absorption.
Bilirubin is a pigment derived from heme.
Functions through enterohepatic circulation, recycling bile salts between the ileum and the liver.

Acidic, fatty chyme in the duodenum prompts release of CCK and secretin.
Bile salts and secretin in the bloodstream stimulate bile production in the liver.
Vagal stimulation triggers weak gallbladder contractions.
CCK leads to gallbladder contraction and relaxation of hepatopancreatic sphincter, allowing bile flow into the duodenum.

Located deep to the stomach's greater curvature; head encircled by the duodenum, tail near the spleen.
Has both exocrine and endocrine functions; secretes pancreatic juice for digestion and hormones (insulin and glucagon).

Water solution containing digestive enzymes and bicarbonate ions (HCO3−) to neutralize acidic chyme.
Enzymes released in inactive forms, activated in the duodenum:
- Trypsinogen converts to trypsin.
- Procarboxypeptidase converts to carboxypeptidase.
Active enzymes include amylase, lipases, and nucleases—requiring ions or bile for optimal activity.

Secretin and CCK released when fatty or acidic chyme reaches the duodenum.
CCK stimulates enzyme-rich pancreatic juice secretion; secretin induces bicarbonate-rich juice.
Vagal stimulation also enhances pancreatic juice release.

Intestinal obstruction can be mechanical (adhesions, tumors, foreign objects) or nonmechanical (peristalsis halt, trauma).
Inflammatory bowel disease includes Crohn's disease and ulcerative colitis.
Viral hepatitis presents with jaundice and flu-like symptoms, categorized into types A, B, C, and G.

Alimentary canal formation starts in week three, enclosing a tubular yolk sac.
Divided into three regions: foregut, midgut, and hindgut, marked by the vitelline duct.

Middle age complications include gallstones and ulcers.
In older age, digestive organ activity declines, causing reduced digestive juices, less efficient absorption, dehydration of fecal mass leading to constipation, and higher risks of diverticulosis and digestive organ cancers.

Digestive enzymes in the small intestine are primarily secreted by the pancreas.
Fingerlike projections of the intestinal mucosa are called villi.
Pancreatic secretion that helps neutralize chyme is bicarbonate.
The ileum is not part of the large intestine; it is part of the small intestine.
Pocketlike sacs of the large intestine are known as haustra.