The Digestive System

Anatomy of the Digestive System
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Identify and describe the six major processes involved in the gastrointestinal activity.
The six major processes involved in the gastrointestinal activity are ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation (Marieb& Smith, 2016). Digestion is the process of transforming food, previously ingested, into simpler substances to be absorbed. Enzymes break down nutrients into simpler molecules.
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* Ingestion is the entry of food.
* Propulsion is the set of activities associated with moving food along the alimentary canal.
* Mechanical digestion is whenall of the activities break food down into smaller pieces to prepare them for further degradation by enzymes where they can be absorbed.
* Chemical digestion is the chemical breakdown of food into smaller products for absorption.
* In absorption, the simple molecules pass through the walls of the tube and are carried by the blood. 
* The last stage is the defecation, where undigested or unabsorbed substances are eliminated as feces.
What role do hormones play in hunger and satiety?
Various hormones influence hunger and satiety (a feeling of not being hungry). The level of ghrelin (GREL-in) changes when one is hungry, and the hormone produced by P/D1 cells and secreted into the stomach wall before meals to initiate hunger. The hormone goes through the blood channel and crosses the blood-brain barrier until it reaches the hypothalamus, which signals that when one is hungry, one should eat. Ghrelin also induces the production of abdominal fat. Besides an empty stomach, the lack of sleep, lack of exercise, and a sedentary lifestyle cause Ghrelin levels to increase, especially when this is continued. Also, age influences hormone production. 
Leptin is a hormone secreted by adipose cells. These are cells that contain fat and are found in fatty tissues, and are considered a satiety hormone. It is also secreted in other areas such as the stomach, heart, placenta, and muscles. These hormones send a signal that is directed to the hypothalamus of the brain. With this, it is possible to regulate food intake and energy expenditure.
Outline the usual pathway for digestion and absorption of triglycerides (fats).
Triglycerides are a type of lipid that makes up both fats and oils, and both are soluble in water. Because of insolubility, there a...