oVERVIEW OF dIGESTIVE sYSTEM
· · The main parts in the process of the Digestive System are the mouth, the esophagus, the stomach, the liver, the pancreas, small intestine and large intestine. There are others parts also in the process which will be explaioned on this page
The gastrointestinal (GI) or digestive system digests food and transports (absorbs) nutrients (including salts and water) into the blood.· Digestion involves breaking down foods both chemically and mechanically into smaller components that can be transported (absorbed) through the digestive tract wall (epithelium) and into the blood (most breakdown products) or lymph (for fat breakdown products).
· Many secretions of the digestive system together with the muscular action of the GI tract are necessary to complete digestion.
· Hunger and satiety are controlled via hormones and other chemicals that influence the hypothalamus control center for ingestion. Social factors and the availability of food also influence the amount of food that we eat
INtroduction
· The digestive system consists of two components: the alimentary canal (a.k.a. digestive tract) and accessory organs.
·After food is ingested and then processed in the digestive tract, undigested food leaves the system as feces. The human digestive system is a complex series of organs and glands that processes food. In order to use the food we eat, our body has to break the food down into smaller molecules that it can process; it also has to excrete waste.
Most of the digestive organs (like the stomach and intestines) are tube-like and contain the food as it makes its way through the body. The digestive system is essentially a long, twisting tube that runs from the mouth to the anus, plus a few other organs (like the liver and pancreas) that produce or store digestive chemicals.
These are some goals you should be able to accomplish after reading these pages.
- To identify the organs and circular muscles (sphincters) of the digestive tract.
- To list the structures found in a representative section of the wall of the digestive tract
- To recognize the accessory organs of the digestive system.
mouth
- Ingestion occurs in the mouth.
- Chemical digestion (saliva w/amylase for starch digestion) and mechanical digestion (teeth & tongue) occur in the mouth.
- The lining of the oral cavity and pharynx is a stratified squamous epithelium mucosa.
- The partially digested bolus of food is moved from the mouth to the esophagus, and then the stomach.
- There is a transition in the esophagus wall from striated (skeletal) to smooth muscle, from the upper to lower portions, respectively,.
stomach
- The muscular stomach is involved in chemical (mostly protein) and mechanical digestion, as well as storage of food.
- The cardia, fundus, body, and pyloric (w/antrum) regions are specialized areas of the stomach.
- The muscularis externa layer of the stomach wall is unique in that it has three sheets of muscle (circular, longitudinal, and oblique).
- The stomach can expand greatly because of internal folds called rugae
- Once food is mixed with gastric juices in the stomach it is called chyme, which is then moved from the pylorus to the duodenum of the small intestine.
intestines
- The majority of chemical digestion and virtually all-nutrient absorption occur in the small intestine.
- The three regions of the small intestine are the duodenum, jejunum, and ileum
- The three modifications of the inner wall of the small intestine that function to increase surface area are (from macroscopic to microscopic) the plicae circularis (circular folds), villi, and microvilli
- The intestine aids the body in its defense against pathogens by secreting antibacterial enzymes and antibodies (immunoglobulins) and by providing specialized sites in the ileum (lymphoid nodules called Peyer’s patches) where leukocytes can fight pathogens
- The large intestine absorbs water, salt, and vitamin K
- The large intestine includes the cecum, appendix, colon, rectum, and anal canal
here is an overview from the Esophagus to the Anus
gO ON THE LINK BELOW TO LEARN MORE ABOUT THE DIGESTIVE SYSTEM!!!
Intereactive Website of the Anatomy of the Digestive System
http://www.innerbody.com/image/digeov.html
http://www.innerbody.com/image/digeov.html