KINE 2031 Lecture Notes - Lecture 16: Muscularis Mucosae, Lamina Propria, Muscular Layer
16 Dec 2016
School
Department
Course
Professor
• Chapter 23: The digestive system
The various organs of the digestive system can be divided into two main groups:
1) The alimentary canal (aliment = nourishment)
- also called the gastrointestinal (GI) tract, is the muscular digestive tube that winds
through the body, extending from the mouth to the anus. The organs of the alimentary
canal are the mouth, pharynx, esophagus, stomach, small intestine (small bowel), and
large intestive (large bowel), the last of which leads to the terminal opening, or anus. In a
cadaver, the alimentary canal is about 9 m (30 feet) long, but in a living person it is considerably
shorter because of its muscle tone. Food material in the alimentary canal is technically
considered to be outsidethe body because the canal is open to the external environment at both
ends.
2) The accessory digestive organs.
- The accessory digestive organs are the teeth and tongue, plus the gallbladder and
various large digestive glands – the salivary glands, liver, and pancreas—that lie external
to and are connected to the alimentary canal by ducts. The accessory digestive glands
secrete saliva, bile, and digestive enzymes, all of which contribute to the breakdown of
foodstuffs.
find more resources at oneclass.com
find more resources at oneclass.com
Digestive processes:
The organs of the digestive system perform the following six essential food-processing
activites: ingestion, propulsion, mechanical digestion, chemical digestion, absorption,
and defecation
1) Ingestion is taking of food into the mouth.
2) Propulsion is the movement of food through the alimentary canal. It includes
swallowing, which is initiated voluntarily, and peristalsis, an involuntary process.
Peristalsis aoud otatio, the ajo eas of populsio thoughout the
alimentary canal, involves alternate waves of contraction and relaxtion of musculature
in the organ walls. Its net effect is to squeeze food from one organ to the next, but some
mixing occurs as well.
3) Mechanical digestion physically prepares food for chemical digestion by enzymes by
breaking it into smaller pieces. Mechanical processes include chewing, the churning of
food in the stomach, and segmentation, the rhythmic local constrictions of the
intestine. Segmentation mixes food with digestive juices and increases the efficiency of
nutrient absorption by repeatedly moving different parts of the food mass over the
intestinal wall.
4) Chemical digestion is a series of steps in which complex food molecules
(Carbohydrates, proteins, and lipids) are broken down to their chemical building blocks
(simple sugars, amino acids, and fatty acids and glycerol). Glands in the gastrointestinal
tract and in the accessory organs produce enzymes and other substances and secrete
them into the lumen of the alimentary canal, where they carry out chemical digestion.
5) Absorption is the transport of digested end products from the lumen of the
alimentary canal into the blood and lymphatic capillaries located in the wall of the canal.
6) Defecation is the elimination of indigestible substances from the body as feces.
find more resources at oneclass.com
find more resources at oneclass.com
Peristalsis:
-Major means of propulsion
-Adjacent segments of the alimentary canal relax and contract
-
find more resources at oneclass.com
find more resources at oneclass.com
