HRTD Medical Institute HRTD Medical Institute
Organic Anatomy of the Digestive System
The human digestive system is composed of the gastrointestinal (GI) tract (a long, continuous tube) and several accessory organs that together break down food into absorbable nutrients and eliminate waste.
Organs of the Gastrointestinal (GI) Tract
Food passes directly through these hollow organs, which are connected in a long, twisting tube from the mouth to the anus.
- Mouth Digestion begins here with the mechanical breakdown (chewing) of food by the teeth and the chemical breakdown of carbohydrates by enzymes in saliva produced by the salivary glands.
- Pharynx (throat): A passageway for food and air. During swallowing, a flap of tissue called the epiglottis covers the windpipe to prevent choking.
- Esophagus: A muscular tube that transports the swallowed food bolus from the pharynx to the stomach via rhythmic muscle contractions called peristalsis.
- Stomach: A J-shaped, muscular organ that mixes and churns food with strong gastric acids and enzymes, beginning the chemical digestion of proteins and creating a semi-liquid mixture called chyme.
- Small Intestine: The primary site for digestion and the absorption of most nutrients into the bloodstream. It is divided into three parts:
- Duodenum: The first and shortest section, where chyme mixes with digestive juices from the pancreas and liver.
- Jejunum: The middle section where most nutrient absorption occurs.
- Ileum: The final section, where remaining nutrients, bile salts, and vitamins (like B12) are absorbed.
- Large Intestine: The final section of the GI tract, which absorbs most of the remaining water and electrolytes from the indigestible food matter, converting the liquid waste into semi-solid stool (feces). It is subdivided into the cecum, colon (ascending, transverse, descending, and sigmoid), and rectum.
- Rectum: The lower end of the large intestine that stores feces before they are eliminated from the body.
- Anus: The external opening at the very end of the digestive tract through which feces exit the body during a bowel movement.
Accessory Digestive Organs
These organs support the digestive process by producing or storing essential secretions, but food does not pass directly through them.
- Salivary Glands (parotid, submandibular, sublingual) produce saliva, which moistens food and contains enzymes (amylase and lipase) to begin starch and fat digestion.
- Liver: Produces bile, a digestive juice that emulsifies fats in the small intestine, making them easier to digest and absorb.
- Gallbladder: A small, pear-shaped organ that stores and concentrates bile produced by the liver, releasing it into the small intestine when food containing fat is present.
- Pancreas: Produces a range of digestive enzymes (for carbohydrates, proteins, and fats) and bicarbonate to neutralize stomach acid in the duodenum. It also produces important hormones like insulin.
