Nutrition in Humans

What to Learn

The meaning of nutrition in living beings: nutrition as an exchange of matter and energy. Humans as heterotrophs.
Overview of the nutrition in humans; organ systems involved (digestive system, respiratory system, circulatory system and excretory system).
The digestive system anatomy: alimentary canal and accessory glands.
Stages of the digestive system work: ingestion, digestion (types, stages, enzymes), absorption and elimination.
Ventilation and respiration as contributing processes to human nutrition.
The respiratory system anatomy: respiratory pathways, lungs, ribcage.
The respiratory system physiology: breathing movements, gas exchange, breathing rhythm control.
Components of the blood: plasma and blood cells (types and functions).
The cardiovascular system: blood vessels (types and roles); the heart (structure and function); cardiovascular circuits.
Overview of the lymphatic system.
The urinary system: its role in homeostasis and waste disposal; structure and function of the kidney; structure and function of the nephrons; composition of the urine as compared to the blood.
The sweat glands: their role in homeostasis and waste disposal; composition of the sweat as compared to the blood.
Types of nutrients.
Types of foods.
Balanced diets; basal metabolic rates.
Specific diets: for weight management, for sports, for longevity.
Food conservation, manipulation and marketing.
Food production enhancement methods and their consequences: fertilisers, pesticides, herbicides, intensive farming, GM foods.

Key Information

Vocabulary: Nutrition

Nutrition	Getting the matter and the energy that every living being needs to grow, survive and reproduce. As it also involves the removal of waste substances and residual energy, it can be described as an exchange of matter and energy with the environment.
Breathing	The movements performed by the lungs (along with the rib cage) to inhale and exhale the atmospheric air.
Respiration	The process carried by the mitochondria, whereby small energetic nutrients (monosaccharides, fatty acids) are burnt with the help of the oxygen to produce the energy that the cells need. This process also involves the removal of CO₂, H₂O(g), and heat.
Gas exchange	You need to convey O₂ from the atmospheric air to the mitochondria and to convey the CO₂ produced in the mitochondria to the atmospheric air. To do this, two gas exchanges are needed: (a) between the alveoli and the blood and (b) between the blood and the cells of every organ in your body. The blood vessels that take part in both gas exchanges are always the capillaries, because of their very thin membranes.
Blood	The fluid that, amongst other things, conveys (a) the oxygen from the lungs to the cells, (b) the other nutrients from the small intestine to the cells, (c) the CO₂ from the cells to the lungs, and (d) the other waste substances from the cells to the kidneys and the sweat glands.
Heart	The organ that pumps the blood throughout all the body. It has two chambers to receive the blood (right and left atria) and two others to expell the blood (the left and right ventricles). Two valves (tricuspid and mitral) control the passing of the blood from the atria to the ventricles, and two other valves (aortic and pulmonary) control the passing of the blood from the ventricles to the arteries.
Blood vessels	The organs that transport the blood throughout all the body. The arteries transport the blood from the heart to the organs (small arteries are called arterioles), the veins from the organs to the heart (small veins are called venules), and the capillaries are the very thin ones that perform the exchange of gases between the blood and the cells or the blood and the alveoli.
Excretion	Disposing of the waste substances produced by the cells. It is done through the exhalation movement of the lungs, the kidneys and the sweat glands.

Vocabulary: Digestive System

Peristalsis	The wavelike muscular contractions of the digestive tract by which its contents are forced to move onwards. It is performed by the ring-like muscles of the walls of the esophagus, the stomach and the intestines.
Bolus	The food mass that crosses the esophagus after having undergone a first digestive stage in the mouth.
Chyme	The fluid food mass that is produced in the stomach when the bolus undergoes a second digestive stage.
Chyle	The very fluid food mass that is produced in the duodenum when the chyme undergoes the third digestive stage.
Enzymes	They are special proteins that behave as catalysts, i.e., they accelerate each and every chemical reaction in your body; otherwise, those chemical reactions wouldn't take place, or would do at a very slow pace. Enzymes are very specific and each one can catalise only one chemical reaction: for instance, the only thing that salivary amylase can do is breaking the starch into maltose.
Digestive enzymes	The enzymes that break down the long molecules in the foods into much smaller ones that can later on be absorbed into the bloodstream. The main ones are the amylases (break down carbohydrates into sugars), the proteases (break down proteins into aminoacids) and the lipases (break down the lipids into glycerol and fatty acids). They come in the following digestive juices: the saliva, the gastric juice, the pancreatic juice and the intestinal juice.
Bile	One of the five digestive juices. It is produced by the liver, stored in the gall-bladder, and it is greenish. It is necessary mostly not to carry digestive enzymes to the duodenum, but to transport bile salts to the duodenum. The bile salts are necessary to help the lipids to "dissolve" in the chyle, forming small droplets, easy to be attacked by the lipases. This process is called emulsification.
Villi	The finger-like folds in the small intestine. They increase greatly the absorption surface in the small intestine (otherwise, the absorption of the nutrients from every meal would last for weeks). To allow an easy passing of the nutrients, they are very thin. Inside them, the nutrients are collected by capillary vessels and lymphatic vessels, and end up in the bloodstream.
pH	A measurement that expresses the level of acidity of a substance: the lower the pH, the greater the acidity; the higher the pH, the greater the alkalinity. Substances with a pH of 7 are neutral, i. e., neither acid nor alkaline.
Lymph	A clear fluid that circulates through the vessels of the lymphatic system. It collects the lipids in the small intestine and transports them to the bloodstream near the neck; it also helps the maturing of the young white blood cells before they are sent to the blood.

Functions of the Digestive System

	What	Where
Digestion	Breaking down the foods into small molecules that the blood can absorb later on (the nutrients) and into somewhat bigger molecules that can't be absorbed (dietetic fibre and others).	Mouth, stomach and duodenum
Absorption	The small nutrients from the digested foods pass from the digestive tract to the blood and the lymph.	Jejunum and ileum
Elimination	The indigestible molecules of the foods and some other waste substances are expelled out of the body.	Rectum and anus

Digestive Juices

	Produced by	Released to
Saliva	Salivary glands (parotids, sublinguals and submandibulars).	Mouth
Gastric juice	Small glands in the lining of the stomach.	Stomach
Bile	Liver (and stored in the gall-bladder).	Duodenum
Pancreatic juice	Pancreas.	Duodenum
Intestinal juice	Small glands in the lining of the duodenum.	Duodenum

A good overview, with text and images, on all the organs of the digestive system and their work, the digestive diseases, a glossary and additional readings.

Digestion time of foods.

Do you know how long takes an apple to be digested?

We are more microbe than man.

About a 90% of your cells are not yours: they are bacteria, most of which live in your intestines. Learn why. You can also listen to the embedded audio version of the article.

Why does my stomach growl?

Whether you call it grumbling, rumbling, gurgling or growling, from time to time everybody's belly chimes in. Learn why.

Cooking and cognition: how humans got so smart.

Learn how cooking improved our digestive efficiency and spurted our brain development.

Respiratory System

The respiratory system at Faqs.org.

A good overview, with text and images, on all the organs of the respiratory system and their functions, the respiratory disorders, a glossary and additional readings.

Circulatory System

The cardiovascular system at Faqs.org.

A good overview, with text and images, on all the organs of the circulatory system and their work, the blood, the cardiovascular disorders, a glossary and additional readings.

How blood works.

Detailed description of the composition and the function of the human blood. It contains two animations that start on page load… you might want to stop and restart them after reading the texts.

Heart pictures.

A set of eight photos related to the heart and its working.

Urinary System

The urinary system at Faqs.org.

A good overview, with text and images, on all the organs of the urinary system and their functions, the urinary diseases, a glossary and additional readings.

Nutrients, Diets and Foods

Nutrition at Faqs.org.

A wide overview, with text and images, on food groups, nutrients, dietary habits, diets, eating disorders, a glossary and additional readings.

How food works.

A lot of interesting and detailed info about the main human nutrients. It contains some images and one animation that starts on page load… you might want to stop and restart it after reading the texts.

How to calculate how many calories you need to eat to lose weight?

The key to fat loss is first figuring out how many calories you should be taking in each day. Learn how.

How food preservation works.

Freezing, canning, salting… Detailed info on these and other commonly used food preservation techniques.

Nutrition Diva.

Sort food facts from fiction, separate the good information from the bad, to make eating healthy just a little bit easier.

Snake oil?

Excellent chart showing how much scientific evidence there is for popular health supplements.

Healing food reference.

A website meant to empower consumers with information about the healing power of foods.

Videos

I U

b f d 0

Digestive System

Digestive system

Short introductory video on the function of the digestive system.

Digestion

Watch the digestion process.

Respiratory System

Respiratory system (I)

Respiration Medical Animation, with detailed information on the respiratory system.

Argosy Medical Animation

Respiratory system (II)

Comprehend the structure and location of various respiratory organs that together make the respiratory system and explore the continuous process of breathing.

Produced by DesignMate Pvt. Ltd.

Respiratory system (III)

This video gives a detailed description of the anatomy and physiology of the lungs.

Nucleus Medical Media

Respiratory system (IV)

The mechanism of breathing and the anatomy of the organs that carry out this activity, brought vividly to life through revealing animation and x-ray motion pictures.

Produced by the Phoenix Learning Group