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GI Tract in Health_Small_Large_Intestine

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The document provides an overview of the anatomy and physiology of the gastrointestinal tract, focusing on the small and large intestines.

The <strong>small intestine</strong> is about 20–25 feet long and is the main site for digestion, nutrient absorption, water absorption, and movement of food through the GI tract. It has three parts: the <strong>duodenum</strong>, <strong>jejunum</strong>, and <strong>ileum</strong>. The <strong>duodenum</strong> is the first and shortest section, divided into four parts, and receives bile from the liver/gallbladder and pancreatic enzymes through the bile and pancreatic ducts. It is the major site for food breakdown and begins absorption of nutrients, including iron. The <strong>jejunum</strong> is the middle segment, about 8–10 feet long, and is responsible for absorbing carbohydrates, fats, proteins, minerals, and some vitamins. The <strong>ileum</strong> is the final 8–15 feet and connects to the colon at the ileocecal valve. It continues nutrient absorption and is specialized for absorbing bile salts, fat-soluble vitamins (A, D, E, and K), and vitamin B12.

The small intestine contains <strong>villi</strong>, which greatly increase surface area for absorption.

The <strong>large intestine</strong>, or colon, is the last part of the GI tract and is about 4–5 feet long. Its main functions are absorption of water and electrolytes and elimination of solid waste. Its major sections include the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anus.

The document also explains <strong>peristalsis</strong>, the coordinated contraction and relaxation of smooth muscle that moves contents through the GI tract. Finally, it describes the <strong>rectum and anus</strong>, including the internal and external anal sphincters, which control stool retention and defecation.

Keywords

small intestine

large intestine

duodenum

jejunum

ileum

villi

peristalsis

colon

rectum

anus