(15) Abdomen III: Small and Large Intestines

Comprehensive flashcards covering the anatomy, function, blood supply, and clinical conditions of the small and large intestines.

Duodenum length

About $10\text{ inches}$ long, extending from the pylorus of somach to the duodenojejunal junction. organized into 4 parts:

• superior, descending, horizontal, ascending

1st part of the duodenum

Also called the upper duodenal cap, it is free and suspended by the hepatoduodenal part of the lesser omentum.

Retroperitoneal duodenum

Refers to the sections of the duodenum (parts 2, 3, and 4) that are fixed in place.

Descending (2nd) part of the duodenum

The part of the duodenum that receives the bile duct and pancreatic duct.

Hepatopancreatic ampulla

The site where the bile duct and pancreatic duct come together before opening at the major duodenal papilla.

Major duodenal papilla

The opening in the duodenum for the pancreatic and bile ducts, guarded by the sphincter of the hepatopancreatic ampulla.

Inferior (3rd) part of the duodenum

Also known as the horizontal part, it crosses anterior to the aorta and the IVC.

Ascending (4th) part of the duodenum

The final section of the duodenum that connects with the jejunum at the duodenojejunal junction.

Duodenum Funtions

regulatory center, utilizing hormones released from its epithelium to manage the digestive environment

Secretin

A hormone released from the duodenal epithelium when pH is low to stimulate water and bicarbonate secretion.

Cholecystokinin

A hormone released in the presence of fatty acids that stimulates gallbladder contraction and relaxes the hepatopancreatic sphincter.

Pancreaticoduodenal arteries

The blood supply for the duodenum, originating from the celiac trunk and superior mesenteric artery.

Venous Drainage of Duodenum

Follows the arterial pathways and empties into the portal venous system.

Duodenal ulcers

Clinical condition often occurring at the first part of the duodenum where acid chyme is squirted from the stomach.

→ more common than gastric ulcers

Jejunum and Ileum length

The combined length of these two parts of the small intestine is about $20\text{ feet}$.

Jejunum

The proximal $\frac{2}{5}$ of the small intestine following the duodenum.

Ileum

The distal $\frac{3}{5}$ of the small intestine where most digestion and almost all nutrient absorption occurs.

Mesentery

The structure that attaches the jejunum and ileum to the posterior abdominal wall.

Superior mesenteric artery

The primary arterial source for the jejunum and ileum via jejunal and ileal branches.

Lymphatic Systems

A network of vessels and nodes that play a crucial role in the immune system by transporting lymph, a fluid containing infection-fighting white blood cells, throughout the body.

Thoracic duct

The ultimate drainage destination for lymph containing digested fat after passing through mesenteric lymph nodes.

Meckel's diverticulum

An outpouching of the ileum present in about $2\%$ of the population, caused by the persistence of the omphalomesenteric duct.

Omphalomesenteric duct

An embryonic structure that, if persistent, results in Meckel's diverticulum.

Large intestine primary functions

Absorption of water and electrolytes and storage of undigested material until excretion as feces.

Teniae coli

Three thickened bands of longitudinal muscle found in the large intestine wall.

Haustra

Sacculations of the wall of the large intestine formed by the contraction of the teniae coli.

Epiploic appendages

Pouches of peritoneum filled with fat that serve a protective and defensive mechanism in the large intestine.

Cecum

The mobile part of the large intestine lying below the junction of the ileum, despite having no mesentery.

Vermiform appendix

A narrow blind tube joining the cecum about one inch below the ileocecal opening.

Mesoappendix

The short mesentery associated with the vermiform appendix.

McBurney's Point

The site of the base of the appendix, located $\frac{1}{3}$ of the distance from the right anterior superior iliac spine to the umbilicus.

Ileocecal valve

A partly functional valve located at the end of the ileum at its junction with the cecum and colon.

Ascending colon

The retroperitoneal part of the large intestine extending upward from the cecum to the right colic flexure.

Right colic flexure

Also known as the hepatic flexure, the point where the ascending colon becomes the transverse colon.

Transverse colon

The segment of the colon suspended by the transverse mesocolon, extending between the right and left colic flexures.

Transverse mesocolon

The double layer of peritoneum that suspends the transverse colon.

Phrenicocolic ligament

A ligament that attaches the left colic flexure to the diaphragm.

Left colic flexure

Also called the splenic flexure, where the transverse colon becomes the descending colon.

Descending colon

The retroperitoneal segment that passes inferiorly from the left colic flexure to the brim of the pelvis.

Sigmoid colon

The pelvis-bound part of the colon extending from the iliac fossa to the 3rd sacral vertebra.

Sigmoid mesocolon

The peritoneal attachment that suspends the sigmoid colon from the pelvic wall.

Ileocolic artery

A branch of the superior mesenteric artery that supplies the ascending colon and cecum.

Right colic artery

A branch of the superior mesenteric artery supplying the ascending colon.

Middle colic artery

A branch of the superior mesenteric artery that supplies the transverse colon.

Left colic artery

A branch of the inferior mesenteric artery that supplies the descending colon.

Sigmoid branch of the inferior mesenteric artery

The arterial supply specifically for the sigmoid colon.

Superior rectal artery

The terminal branch of the inferior mesenteric artery supplying the rectum.

Marginal artery

An anastomosis of colic arteries located around the margin of the large intestine.

Appendicitis

Inflammation of the appendix, usually caused by obstruction from fecal material.

Ulcerative colitis

A chronic disease involving severe inflammation and ulceration of the colon and rectum.

Celiac and superior mesenteric plexus

Sources of sympathetic and parasympathetic nerves for the duodenum.

Vagus and greater splanchnic nerves

Nerve sources for the jejunum and ileum, acting through the celiac ganglion.

3rd sacral vertebra

The anatomical level where the sigmoid colon typically ends.