Untitled Quiz

Digestive System Overview

• The digestive system's function is ingestion, transport, breakdown of food, absorption of nutrients, and expulsion of wastes.
• Food mixed with saliva is called a bolus.
• The stomach converts bolus into chyme.
• The esophagus transports food to the stomach.
• The liver detoxifies molecules, stores vitamins/iron/glycogen, and creates bile.
• The gallbladder stores and concentrates bile.
• The pancreas releases digestive enzymes and hormones (e.g., insulin).
• The small intestine absorbs nutrients.
• The rectum/anus stores and expels feces.
• The large intestine absorbs water and ions.

Structure of the Digestive System

• The gastrointestinal (GI) tract includes the oral cavity, pharynx, esophagus, stomach, small intestine, and anus.
• Accessory digestive organs are the teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Anatomy of the Oral Cavity and Esophagus

• The oral cavity has a vestibule between the cheeks/lips and gums and an oral cavity proper central to the alveolar processes of the jaw bones.
• Structures within the oral cavity: teeth, tongue, vestibular, palatoglossal arch, palatopharyngeal arch, palatine tonsil, lingual frenulum, salivary ducts, sublingual, and submandibular glands.
• The esophagus connects the pharynx to the stomach, is a muscular tube (25-30 cm long), begins at C6 and cricoid cartilage, and extends to the cardiac orifice of the stomach.

Anatomy of the Stomach

• The stomach is located in the upper left quadrant and in the epigastric and left hypochondriac regions.
• The stomach has four regions: cardia, fundus, body, and pylorus.
• The internal surface of the stomach has gastric folds (rugae).
• The pylorus is the funnel-shaped terminal region.
• The lesser curvature and greater curvature are distinct regions of the stomach.

Innervation and Circulation of the Stomach

• The stomach is innervated by parasympathetic fibers from the vagus nerve and sympathetic fibers from the celiac ganglia.
• Branches of the celiac trunk supply blood to the stomach.
• Blood drained from the stomach and intestines enters the hepatic portal circulation and is filtered through the liver before returning to the heart.

Small Intestine

• The small intestine is the longest part of the GI tract (about 5 m in a living person; up to 8 m in a cadaver).
• It has a diameter of about 2.5 cm.
• The small intestine is subdivided into the duodenum, jejunum, and ileum.
• The duodenum begins at the pyloric valve, receives stomach contents, pancreatic juice, and bile.
• The duodenojejunal flexure marks the border between the duodenum and jejunum.
• The jejunum is intraperitoneal, has a rich blood supply (which gives it a red color).
• The ileum is intraperitoneal; the ileocecal junction is where the ileum joins the cecum of the large intestine.
• The ileal papilla protrudes into the cecum, and controls the passage of food residue into the large intestine.

Large Intestine

• The large intestine begins as the cecum inferior to the ileal papilla.
• The colonic regions include ascending, transverse, and descending colon and portions between them like right and left colic flexures, and the sigmoid colon.
• The rectum has three curves and folds, called transverse rectal folds/rectal valves..
• The anal canal is the final 3 cm of the large intestine; passes through the levator ani muscle and pelvic floor, and terminates at the anus.
• The internal and external anal sphincters are located at the end of the anal canal.

Liver

• The liver is a reddish brown organ located immediately inferior to the diaphragm, in the right upper abdominal quadrant.
• It is the body's largest organ (~1.4 kg (3 lbs)).
• The liver performs various functions, including detoxification, production of cholesterol and hormones like vitamin D, metabolism, storage of micronutrients, and immune response.
• The liver produces bile.
• The liver is divided into four lobes (Right, Left, Quadrate and Caudate lobes).
• The liver has ligaments, including the falciform ligament, which separates left and right lobes.
• The round ligament (ligamentum teres) is a fibrous remnant of the umbilical vein.