intro to digestive system
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Define digestion
The process of breaking down food into molecules small enough to be absorbed into the circulatory system for transport through the body.
What are the two types of Digestions?
• Mechanical digestion • Chemical digestion
Mechanical digestion
breaks down food through chewing and movement of the tongue, and the grinding action of the stomach.
Where does mechanical digestion take place?
In mouth and stomach
Chemical digestion
the use of digestive enzymes to break down large molecules in food to make them small enough to be absorbed into the blood.
Where does chemical digestion take place?
A little bit in the mouth and majority takes place in the stomach.
What are digestive enzymes?
These are proteins used to catalyze the process of digestion or breaking down food.
Digestive enzymes are equivalent to =
Chemicals that help breakdown food.
Name the 5 layers of the digestive tract wall?
• Mucosa • Muscularis Mucosae • Submucosa • Muscularis Externa • Serosa
(1) Mucosa Layer
-Thin lining on the inside of digestive tract
What is the primary function of the layer mucosa?
secretion of mucous to keep the digestive tract moist.
What kind of tissue is the Mucosa layer made up of?
-Mostly simple columnar epithelium with deeper -loose connective tissue (in the lamina proper)
(2) Muscularis mucosae Layer
region in the mucosa containing two layers of smooth muscle.
In the muscularis mucosae layer, what are the characteristics of the two layers of smooth muscle?
-Inner layer is circular -Outer layer is Longitudinal.
What is the purpose of the two layers of smooth muscle found in the muscularis mucosae in the digestive tract?
The contraction of these two layers of muscle allow for the movement of food inside of the digestive tract.
(3) submucosa Layer
-A layer of dense irregular connective tissue beneath the mucosa -Contains blood vessels, nerves and lymph ducts
(4) Muscularis Externa Layer
A region that contains two layers of smooth muscles (circular and longitudinal in shape).
What is the purpose of the two smooth muscle layer (circular and longitudinal) in the digestive tract?
The contraction of these muscles allow for the movement of food passing through the digestive tract.
What is Peristalsis?
involuntary contraction and relaxation of longitudinal and circular muscles throughout the digestive tract, allowing for movement of food.
(5) Serosa layer
-This is the most outer layer or the most superficial layer covering the digestive tract. -only specific to the digestive tract
What organs are said NOT to be covered by the serosa layer? but are otherwise covered by?
• Pharynx • Esophagus • Mouth • Rectum These organs are covered by a layer called Adventitia
What kind of tissue lines the esophagus?
stratified squamous epithelium
The serosa layer of the digestive tract is said to cover above/below the diaphragm?
below diaphragm
The adventitia layer is said to cover below or above the diaphragm?
covers organs above the diaphragm. i.e esophagus.