Upper digestive tract
Mouth-
Functions: Ingestion of the food.
Deglutition
Mechanical digestion (mastication)
Production of saliva.
Sense the food.
Moist the food – make the bolus.
Chemical digestion -Enzyme (Components in saliva help keep the pH in your mouth between 6.5 and 7 so th...
Case Study 1
Digestive system:
Important key concepts.***
Book: Saladin, K. (2019). Anatomy and Physiology: The Unity of Form and Function (9th ed.).
Upper digestive tract
Mouth-
Functions: Ingestion of the food.
Deglutition
Mechanical digestion (mastication)
Production of saliva.
Sense the food.
Moist the food – make the bolus.
Chemical digestion -Enzyme (Components in saliva help keep the pH in your mouth between 6.5
and 7 so that the enzyme salivary amylase can start to break down carbohydrates. The enzymes
that help digest food in the stomach, such as pepsin, work best at a pH around 2, while those that
function in the intestines, including peptidases and maltase, work best at a pH around 7.5)
Saliva also contains a small amount of lipase, which digests lipids. Sometimes called lingual
lipase because it is produced by the lingual salivary glands, it functions at a low pH and thus can
break down lipids as it moves into the stomach and into the upper duodenum. Lingual lipase-
lipids.
Pharynx-
The act of swallowing, or deglutition, moves a rounded mass of food, called a bolus, from the
mouth to the stomach. As the food bolus passes from the mouth, it enters the oropharynx by
passing through a constricted, archlike opening called the faucets.
Deglutition only
Esophagus-
The esophagus, a collapsible, muscular, mucosa-lined tube about 25 cm (10 inches) long, extends
from the pharynx to the stomach and pierces the diaphragm in its descent from the thoracic
cavity to the abdominal cavity.
Deglutition and Peristalsis
Stomach-
Functions of the stomach
1. Reservoir for food until it is partially digested and moved farther along the GI tract
2. Secretes gastric juice to aid in digestion of food
3. Breaks food into small particles and mixes them with gastric juice
4. Secretes intrinsic factor and HCL
5. Performs limited absorption
6. Produces gastrin and ghrelin
7. Helps protect the body from pathogenic bacteria swallowed with food
Duodenum-
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