Digestion and Metabolism

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Our food choices are connected to the environment

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We have learned about nutrient cycles that explain how nutrients such as nitrogen and phosphorous get into our food.

We have learned about food webs and how everything is connected from the microbes to the whales.

Let's learn more about anatomy and physiology starting with digestion and metabolism.

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Today we learn more about digestion

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Digestion: the mechanical breakdown and chemical breakdown of food into subunits so that nutrients can be absorbed.

Ingestion: the act of taking food into the mouth

Digestive Tract: the central pathway of the digestive system; a long muscular tube that pushes food through

Salivary Glands: glands that secrete enzymes including salivary amylase, which digests carbohydrates in the mouth

Tongue: a muscular organ in the mouth that aids in swallowing. 

Esophagus: the section of the digestive tract between the mouth and the stomach

Peristalsis: coordinated muscular contractions that force food down the digestive tract 

Stomach: an expandable muscular organ that stores, mechanically breaks down, and digests protein in food.

Pepsin: a protein digesting enzyme that is active in the stomach

Chyme: the acidic "soup" of partially digested food that leaves the stomach and enters the small intestine

Small intestine: the organ in which the bulk of chemical digestion and absorption of food occurs

Duodenum: the first portion of the small intestine; the duodenum receives the chyme from the stomach and mixes it with digestive secretions from other organs

Jejunum: 0.9 meters (3 feet) long

Ileum: the longest part of the small intestine, about 1.8 meters (6 feet) long. It is thicker, more vascular, and has more developed mucosal folds than the jejunum.

https://socratic.org/questions/what-are-the-parts-of-the-small-intestines-which-portion-connects-directly-with-

Pancreas: an organ that helps digestion by producing enzymes such as lipase that act in the small intestine, and by secreting a juice that neutralizes acidic chyme. 

Liver: an organ that aids digestion by producing bile salts that emulsify fats

Bile Salts: chemicals produced by the liver and stored by the gallbladder that emulsify fats so they can be chemically digested by enzymes.

Emulsify: to break up large fat globules into small fat droplets that can be more efficiently chemically digested by enzymes 

Gallbladder: an organ that stores bile salts and releases them as needed into the small intestine.

Lipase: a fat-digesting enzyme active in the small intestine

Epithelial cells: cells that line organs and body cavities; in the digestive tract they sit in direct contract with food and its breakdown products.

Absorption: the uptake of digested food molecules by the epithelial cells lining the small intestine

Villi (singular: Villus): fingerlike projections of folds in the lining of the small intestine that are responsible for most nutrient and water absorption. 

Large Intestine: the last organ in the digestive tract, in which remaining water is absorbed and solid stool is formed

Colon: the first and longest portion of the large intestine; the colon plays an important role in water reabsorption.

Stool: poo, solid waste material eliminated from the digestive tract. 

Elimination: the expulsion of undigested material in the form of stool

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The digestive system works with the nervous system

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Also the endocrine system

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What is Gastric Bypass Surgery?

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