The Small Intestine and the Large Intestine

Flashcards covering the functional anatomy, secretions, and applied physiology of the small and large intestines.

Small Intestine

Part of the gastrointestinal (GI) tract, extending between the pyloric sphincter of the stomach and ileocecal valve, which opens into the large intestine.

Duodenum

Proximal part of the small intestine; responsible for acid neutralization.

Jejunum

Middle part of the small intestine; bulk of chemical digestion and nutrient absorption occurs here.

Ileum

Distal part of the small intestine; involved in Vitamin B12 absorption.

Intestinal Villi

Minute projections covering the mucous membrane of the small intestine, increasing surface area for absorption.

Enterocytes

Columnar cells lining the villi of the small intestine; give rise to microvilli and secrete enzymes.

Microvilli

Hair-like projections on enterocytes that further increase the surface area of the mucous membrane.

Lacteal

Central channel within each villus that opens into lymphatic vessels and contains blood vessels.

Crypts of Lieberkühn

Simple tubular glands of the intestine that open into the lumen of the intestine between the villi.

Enterocytes (function)

Cells that move to villi and secrete enzymes after undergoing division by mitosis in intestinal glands.

Argentaffin Cells

Cells interposed between columnar cells of intestinal glands that secrete the intrinsic factor of Castle.

Goblet Cells

Cells interposed between columnar cells of intestinal glands that secrete mucus.

Paneth Cells

Cells interposed between columnar cells of intestinal glands that secrete cytokines called defensins.

Brunner Glands

Mucus glands found in the first part of the duodenum that secrete mucus and traces of enzymes.

Succus Entericus

Secretion from the small intestine with a volume of 1800 mL/day and an alkaline reaction (pH 8.3).

Peptidases

Proteolytic enzymes present in succus entericus that convert peptides into amino acids.

Amylolytic Enzymes (Succus Entericus)

Lactase, sucrase, and maltase convert disaccharides into monosaccharides; dextrinase converts dextrin into glucose.

Intestinal Lipase

Lipolytic enzyme that acts on triglycerides and converts them into fatty acids.

Enterokinase

Enzyme present in intestinal juice that activates trypsinogen into trypsin.

Malabsorption

Failure to absorb nutrients such as proteins, carbohydrates, fats, and vitamins.

Malabsorption Syndrome

Condition characterized by the failure of digestion and absorption in the small intestine, often caused by Crohn’s disease or celiac disease.

Crohn’s Disease (Enteritis)

Inflammatory bowel disease characterized by inflammation of the small intestine, leading to malabsorption and diarrhea.

Celiac Disease

Autoimmune disorder characterized by damage of mucosa and atrophy of villi in the small intestine due to gluten, leading to impaired digestion and absorption.

Steatorrhea

Condition caused by deficiency of pancreatic lipase, resulting in malabsorption of fat.

Large Intestine (Colon)

Extends from the ileocecal valve up to the anus, consisting of the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal.

Tenia Coli

Three long bands formed by the longitudinal muscle fibers of the large intestine.

Haustra

Series of pouches formed in the large intestine due to the length of the tenia coli being less than the length of the large intestine.

Large Intestinal Juice

Watery fluid with pH of 8.0 secreted by the large intestine, containing water, solids, organic substances, and inorganic substances.

Dietary Fiber (Roughage)

Group of food particles that pass through the stomach and small intestine without being digested and reach the large intestine unchanged.

Diarrhea

Frequent and profuse discharge of intestinal contents in loose and fluid form due to the increased movement of the intestine.

Constipation

Failure of voiding of feces, which produces discomfort, due to the lack of movements necessary for defecation.

Appendicitis

Inflammation of the appendix, typically causing pain in the lower right side of the abdomen.

Ulcerative Colitis

Inflammatory bowel disease characterized by inflammation and ulcerative aberrations in the wall of the large intestine.