Unit2: Nutrition

Unit 2: Nutrition

0. Introduction
1. Digestive System
2. Circulartory System
3. Respiratory System
4. Escretory system


0. INTRODUCTION

Our bodies need energy to work. The energy we receive in the form of food and drink is processed by the digestive system. The respiratory system extracts oxygen from the atmosphere and uses it to convert the nutrients into energy. The circulatory system then transports this energy to different parts of the body. Finally, the excretory system gets rid of unwanted or toxic subtances. The different systems all work in harmony to keep us healthy.

Analyse and organise:

Look at the box below. It has terms for different parts of the body. What function do they have?
Copy and complete the diagram.

1. DIGESTIVE SYSTEM

Digestion is the way your body gets nutrients and energy from the food you eat. Many organs help in digestion.

 

VÍDEO TIME!

2. THE CIRCULATORY SYSTEM

The circulatory system transports nutrients and oxygen through blood to the cells and also helps to get rid of waste.

The main organ of the circulatory system is the heart.

           

A. BLOOD

Blood consists of plasma and blood cells.

1. Plasma:

Plasma is a yellowish liquid which is 90% water. The blood cells float in. It carries the nutrients and waste products.

2. Blood cells:

• Red blood cells give blood its colour. They carry oxygen and carbon dioxide.
• White blood cells fight infection. They surround and absorb germs which enter the body.
• When the body is losing blood because of a cut in the skin, platelets join together and help stop the bleeding.

3. Blood vessels:

Blood is transported through three types of blood vessels.

• Arteries carry blood from the heart to the rest of the body. This blood contains oxygen.
• Veins carry the blood back to the heart. This blood contains carbon dioxide.
• Capillaries are tiny blood vessels which connect the arteries and the veins. They have very thin walls so gases and nutrients can easily pass through them to the cells.

B. THE HEART

The heart is a muscle which pumps blood through the body. It usually beats between 60 and 100 times per minute. When we do exercise, our bodies need more oxygen, so our heart beats faster.

The heart is made up of four chambers: two atria and two ventricles.

The top two chambers are called the right and left atria; they receive blood coming into the heart. 

The bottom part of the heart is made up of the right and left ventricles.

The atria and the ventricles are separated by valves which prevent blood from flowing backwards.

The heart contracts and expands to push blood around the body through beating. Each beat has two phases:

• Systole: The heart contract and sends blood to the arteries.
• Diastole: The heart relaxes and blood enters from the veins.

C. CIRCULATION: HOW YOUR BLOOD MOVES AROUND YOUR BODY.

The movement of the blood through the heart and around the body is called circulation.

Blood flows around the body in a double circuit.

• During pulmonary circulation, blood flows from the heart to the lungs and                     back to the heart again.
• During systemic/general circulation, the blood flows from the heart to                      the rest of the body.

ERASE UNA VEZ EL CUERPO HUMANO....EL CORAZÓN
ONCE UPON A TIME....THE HEART

3. RESPIRATORY SYSTEM

Our cells need oxygen (O2) to combine with nutrients and to produce energy. During this process, the cells produce carbon dioxide (CO2) that has to be expelled from the body. To obtain oxygen and get rid of carbon dioxide we use our respiratory system.

RESPIRATION

When we take a breath, air enters through the nose and mouth. It passes down the pharynx and then to the trachea (or windpipe). 

The trachea divides into two tubes called bronchi. Each bronchus then subdivides into smaller and smaller bronchi. The smallest are bronchioles. 

At the end of each bronchiole is a cluster of tiny air sacks called alveoli. Lungs have about 600 million alveoli. The alveoli are covered with a network of capillaries. Gas exchange takes place in the alveoli. Oxygen passes from the alveoli to the capillaries and into the blood. 

At the same time carbon dioxide leaves the blood and enters the alveoli. The air carrying carbon dioxide goes through the bronchioles to the bronchi and the trachea and finally out through the mouth and nose.

There are two processes involved in respiration: pulmonary ventilation and gas exchange.

A. Pulmonary ventilation

It is the movement of air into and out the lungs. The process is performed by two movements: inhalation and exhalation.

INHALATION
When we take a breath, our diaphragm, the big muscle under the lungs, contracts and flattens to allow the lungs to inflate. The ribs expand and move up to make more room.

EXHALATION
When we breathe out, the ribs relax and move back in. The diaphragm relaxes and moves up, pushing the carbon dioxide out of the lungs and back up the trachea, out of the nose and mouth.

B. Gas exchange.

In your lungs you have alveoli. It is here that gas exchange occurs. During this process, oxygen passes into your blood and carbon dioxide leaves your body.


4. EXCRETORY SYSTEM

The excretory system eliminates (or excretes) waste products from our body. Our body excretes carbon dioxide, urine and water. The excretory system consists of the urinary system and the sweat glands.

A. The urinary system

The urinary system is the principle way in which the body gets rid of waste

from blood. It produces about 1.4 litres of urine every day.

• 1. The renal arteries carry blood to the kidneys.
• 2. The kidneys eliminate water and waste products from the blood. This
• combination of water and harmful substances forms urine.
• 3. Urine leaves the kidneys and passes down through two tubes called 
• the ureters to the bladder.
• 4. When the bladder is about half-full, it sends signals to the brain that it 
• needs to be emptied. This is when you want to go to the toilet!
• 5. The bladder is emptied by another tube called the urethra.

B. Sweating

Our body also eliminates waste products through the skin. When we get hot, sweat glands in our skin are activated to cool down the body. These glands excrete sweat which is a mixture of water and minerals. Sweat leaves our body through pores.