Digestive System Function and Anatomy

Nursing Mnemonics 30 Most Important For Every NureseHunger and thirst prompt us to eat and drink, but after that our digestive system takes care of everything else automatically. As food travels on its journey of digestion, which takes up to two days, it is broken down to release essential nutrients.

Food digestion in digestive system
Food Digestive System


How Digestive System Works.

The digestive system comprises the organs that enable us to take in food, break it down physically and chemically, extract useful nutrients from it, and excrete what we don’t need. This process begins in the mouth, where the teeth, tongue, and saliva work together to form a food into a moist ball that can be swallowed.

The mouth, pharynx, stomach, intestines, rectum, and anal canal form a long tube that is referred to as the digestive tract. It usually takes between one and two days for ingested food to travel all the way from the mouth to the anus. Other organs—including the salivary glands, liver, gallbladder, and pancreas—complete the digestive system.



The mouth is primarily designed for taking in food, but it is also used for speaking and breathing.

An expandable bag, the stomach holds food and releases it bit by bit into the small intestine. It also secretes hydrochloric acid, which kills dangerous ingested bacteria.

Large intestine.
This comprises the cecum and the colon. The large intestine is where water is absorbed from digested food.

Small intestine.
Comprising the duodenum, jejunum, and ileum, the small intestine is where food is digested and nutrients are absorbed.

The largest organ in the human body, the liver produces bile and receives all the nutrients absorbed from the gut.

This baglike organ stores bile until it is needed in the small intestine.

Partially hidden behind the stomach, the pancreas produces hormones (including insulin), and makes enzymes that
aid digestion, which it secretes into the small intestine.


Parts of Digestive System
Organs of the Digestive System

All cells of the body require nutrients. These nutrients are derived from the intake of food that contains proteins, fats, carbohydrates, vitamins and minerals, and cellulose fibers and other vegetable matter of no nutritional value. The primary digestive functions of the GI tract are the following:
• To break down food particles into the molecular form for digestion.

• To absorb into the bloodstream the small molecules produced by digestion
• To eliminate undigested and unabsorbed foodstuffs and other waste products from the body After food is ingested, it is propelled through the GI tract, coming into contact with a wide variety of secretions that aid in its digestion, absorption, or elimination from the GI tract.


Chewing and Swallowing

The process of digestion begins with the act of chewing, in which food is broken down into small particles that can be swallowed and mixed with digestive enzymes. Eating—or even the sight, smell, or taste of food—can cause reflex salivation. Saliva is secreted from three pairs of glands: the parotid, the submaxillary, and the sublingual glands. Approximately 1.5 L of saliva is secreted daily. Saliva is the first secretion that comes in contact with food. Saliva contains the enzyme ptyalin, or salivary amylase, which begins the digestion of starches . Saliva also
contains mucus and water, which help to lubricate the food as it is chewed, thereby facilitating swallowing.

Swallowing begins as a voluntary act that is regulated by a swallowing center in the medulla oblongata of the central nervous system. As food is swallowed, the epiglottis moves to cover the tracheal opening and prevent aspiration of food into the lungs. Swallowing, which propels the bolus of food into the upper esophagus,
thus ends as a reflex action. The smooth muscle in the wall of the esophagus contracts in a rhythmic sequence from the upper esophagus toward the stomach to propel the bolus of food along the tract. During this process of esophageal peristalsis, the lower esophageal sphincter relaxes and permits the bolus of food to enter the stomach. Subsequently, the lower esophageal sphincter closes tightly to prevent reflux of stomach contents into the esophagus.


Small Intestine Function
The digestive process continues in the duodenum. Secretions in the duodenum come from the accessory digestive organs—the pancreas, liver, and gallbladder—and the glands in the wall of the intestine itself. These secretions contain digestive enzymes and bile. Pancreatic secretions have an alkaline pH because of high concentrations of bicarbonate. This neutralizes the acid entering the duodenum from the stomach. The pancreas also secretes digestive enzymes, including trypsin, which aids in digesting protein; amylase, which aids in digesting starch; and lipase, which


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