Digestive Tract PDF

Upper Digestive Tract The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion. Digestion involves the breakdown of food into smaller and smaller components until they can be absorbed and assimilated into the body. Digestive System The following are...

Upper Digestive Tract The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion. Digestion involves the breakdown of food into smaller and smaller components until they can be absorbed and assimilated into the body. Digestive System The following are the functions and structures of digestive systems in humans. You have probably heard the term **digestive system** before. What do you think it means? What do you think the functions of this system are? Let us take a look at the four functions of this system below. Ingestion Food material is taken into the mouth. Digestion Food is broken down mechanically and chemically as it travels through the digestive system. The digestive enzymes speed up the breakdown of complex nutrients such as proteins, sugars, and fats. Absorption Digested food passes through the lining of the gastrointestinal tract and into the bloodstream. Blood then carries the nutrients to other cells of the body to be used as fuel and building materials. Elimination Solid wastes are compacted and eliminated from the body. The **oral cavity (or/o, stomat/o)**, or the mouth, is the beginning of the digestive system. Here the ingestion process happens once you take food into your mouth. The following are the many parts of the oral cavity: The lips are the opening to the digestive tract. They hold food inside the mouth. Lips also aid in breathing, speaking, and others. Cheeks form the walls of the oral cavity. The palate forms the top of the oral cavity. The **hard palate** is the anterior bony portion, and the **soft palate** is the flexible, posterior portion. Do not to confuse the soft palate and its function of closing off the nasal cavity during swallowing with the epiglottis, which covers the trachea during swallowing. The uvula aids in sound production. The tongue, which is a muscle, moves food around the oral cavity and aids in speech. The tongue aids in the mastication of food and prepares the bolus for tavel to continue the digestion process. Papillae are the raised areas on the tongue that contain the taste buds. The five tastes are sweet, salty, sour, bitter, and unami. Tonsils are masses of lymphatic tissue that act as filters against microorganisms. Lymphatic tissue which is a part of the body's immune system helps protect it from bacteria and other foreign entities. This tissue includes the tonsils, lymph nodes, spleen etc. Teeth grind and chew food so it can be swallowed. Teeth are covered in enamel. Gums, or gingiva, make up the fleshy tissue that surrounds the sockets of the teeth. The salivary glands secrete saliva which moistens food, cleanses and lubricates the oral cavity, and contains the enzymes amylase and lipase which begin the digestive process. There are three pairs of salivary glands: - Parotid - Submandibular - Sublingual - Pharynx (pharyng/o) and Esophagus - The **pharynx (pharyng/o) **or throat connects the nasal and oral cavities to the trachea and esophagus. The throat is the passageway for both air and food. A flap of tissue covers the airway during deglutition, This flap, called the **epiglottis**, ensures that food passes through the esophagus. You will hear more about this tissue in the respiratory systems part. - Check out this quick animation to help you visualize [[deglutition]](http://www.dnatube.com/video/29963/Swallowing--of-Food-in-Human). - The esophagus is a muscular tube that leads from the pharynx to the stomach. It moves food towards the stomach by peristalis. View this short animation on [[peristalsis]](http://www.dnatube.com/video/29949/All-About-Peristalsis). Stomach (gastr/o) The **stomach (gastr/o)**, which is located in the left upper quadrant of the abdomen, begins the digestion of proteins and prepares food for further digestion and absorption in the small intestine. This sac-like muscular organ has a capacity of approximately 1.5 L. The interior of the stomach is lined with a mucous membrane arranged in rugae which contain glands that produce enzymes and acid. The exterior is lined with visceral peritoneum. The stomach has three main parts: the fundus, body, and antrum. It is bounded by two sphincters: - lower esophageal (cardiac) - pyloric These sphincters control the flow of chyme from one area to another. The lower gastrointestinal (GI) tract is the last part of the digestive tract; it includes the small intestine and the large intestine. The small intestine, or small bowel, finishes digestion and absorbs nutrients. The walls are lined with villi which are microscopic projections in the wall of the small intestine that absorb nutrients into the bloodstream. The small intestine is approximately six meters long! There are three parts to the small intestine: - **Duodenum (duoden/o):** receives food from the stomach as well as digestive fluids from the accessory organs - **Jejunum (jejun/o):** secretes a large number of digestive enzymes and absorbs nutrients - **Ileum (ile/o):**this longest portion absorbs the remaining nutrients and ends in the ileocecal sphincter The large intestine, or the large bowel, is wider but shorter than the small intestine is. It stores and prepares wastes for excretion. The large intestine mixes chyme with mucus and extracts the water. It also compacts waste into solid feces (stool). There are several regions of the large intestine: - Cecum (cec/o) - Appendix - Ascending colon - Transverse colon - Descending colon - Sigmoid colon - Rectum (rect/o) The appendix does nothing except hang from the cecum. It has no clear function to it; however, if it becomes clogged or blocked, it can become inflamed or infected. This causes serious pain and requires immediate removal. The anus, which is the lower opening of the digestive tract, is controlled by two anal sphincters. Here defecation, which is the expulsion or passage of feces from the body, occurs. **Proct/o** refers to both the rectum and the anus. The liver, the largest gland of the body, is located in the RUQ. It is estimated that the liver has more than 500 functions! Functions of the liver include: - Produces bile - Detoxifies and cleans blood - Stores vitamins and minerals - Manufactures necessary proteins - Regulates the body\'s fuel sources +-----------------------------------+-----------------------------------+ | - **Combining Form** | **Meaning** | +===================================+===================================+ | Gastr/o | Stomach | +-----------------------------------+-----------------------------------+ | Intestin/o | Intestine | +-----------------------------------+-----------------------------------+ | Or/o; Stomat/o | Mouth | +-----------------------------------+-----------------------------------+ | Cheil/o; Labi/o | Lips | +-----------------------------------+-----------------------------------+ | Bucc/o | Cheeks | +-----------------------------------+-----------------------------------+ | Palat/o | Palate | +-----------------------------------+-----------------------------------+ | Gloss/o; Lingu/o | Tongue | +-----------------------------------+-----------------------------------+ | Tonsill/o | Tonsil | +-----------------------------------+-----------------------------------+ | Dent/i; Odont/o | Tooth | +-----------------------------------+-----------------------------------+ | Gingiv/o | Gums | +-----------------------------------+-----------------------------------+ | **Prefix** | **Meaning** | +-----------------------------------+-----------------------------------+ | Endo- | Inside | +-----------------------------------+-----------------------------------+ | Peri- | Surrounding | +-----------------------------------+-----------------------------------+ | Sub- | Below; under | +-----------------------------------+-----------------------------------+ | Ex-; exo- | Outside | +-----------------------------------+-----------------------------------+ **Suffix** **Meaning** --------------- ----------------------------- -ase Enzyme -stalsis Contraction -logist; -ist Specialist; one who studies