The digestive system is a fascinating organ system of the body. It involves many organs to ultimately digest and absorb nutrients necessary for survival. This article will discuss the different digestive system organs and their functions.
The digestive system is composed of the digestive tract and other accessory digestive organs. The digestive tract is a very long tube that starts from the mouth and ends in the anus. Accessory digestive organs are structures that aid in the breakdown of food particles such as the teeth, salivary glands, the pancreas and the liver.
The different digestive tract structures are the mouth, pharynx, esophagus, stomach, small intestine, large intestine, the rectum and the anus. The structures are arranged in order where food particles pass through.
The Digestive Process
Ingested food passes first through the mouth where partial breakdown of food starts. Larger food chunks are broken down into smaller pieces by the teeth during chewing-medically termed as mastication. Saliva produced by the salivary glands help to keep the food moist and slippery for easy passage to the digestive tract. In addition an enzyme in saliva-called salivary amylase-starts breakdown of carbohydrates.
Before swallowing, the food particles usually are formed into a mass of food called bolus. The bolus then passes through the pharynx, the esophagus and eventually enters the stomach.
The stomach is a j-shaped, hollow muscular organ. This digestive structure is also the most distensible organ of the digestive system. This means that the stomach can expand as food fills its inside lumen. The stomach acts as storage and mixing chamber for ingested food. In addition, microorganisms that might be present in the food are killed by the powerful hydrochloric acid produced by the stomach. Also, the stomach produces an enzyme that helps start digestion of fats.
Food in the stomach is converted into soup-like substance called chyme. Ingested food can be stored in the stomach for up to 2 hours where slowly, food particles are emptied into the small intestine.
The small intestine is the longest part of the digestive tract measuring about 6 meters long. However, in a live person the small intestine can be shorter at about 3 meters. The reason for this is that smooth muscles in the small intestine wall are in a state of partial contraction. It is subdivided into three portions: the duodenum (first part), the jejunum (second) and the ileum.
The small intestine is where major digestion and absorption of nutrients occur. The small intestine produces several enzymes that help breakdown food particles. In addition, the liver and pancreas also release enzymes that drain in the small intestine, which aid in digestion as well. Once most of the nutrients are absorbed the remaining food particles are emptied into the large intestine. Once in the large intestine the food substances are called stool or feces.
The large intestine, the last part of the digestive tract, is subdivided into several portions. They are the cecum, the colon, the rectum and the anal canal.
Major functions of the large intestine include absorption of some water, ions and vitamins. In addition, friendly bacteria in the large intestine help produce some B vitamins and vitamin K. Vitamin K is needed for production of certain clotting factors that ultimately help form a clot that can seal wounds. This is probably the reason why use of certain antibiotics-medicines that kill bacteria-can affect bleeding time and sealing of wounds by blood clots.
Defecation or emptying of the bowel occurs at the rectum and anal canal
References:
Your Digestive System and How it Works. Retrieved February 11, 2010 from http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/index.htm
Seeley, R. et al: ESSENTIALS OF ANATOMY AND PHYSIOLOGY. 5th ed. McGraw – Hill, 2005.
Tortora, G. and Grabowski, S.: PRINCIPLES OF ANATOMY AND PHYSIOLOGY. 10th ed. John Wiley and Sons, Inc., 2003.
