III. The Respiratory System. Respiration.
I. The Skeleton.
1. Which part of the skeleton is the most important?
2. What classes do the naturalists divide all the animals into?
3. What do the bones of the body include?
4. Where is the skull? What do the bones of the head include?
5. What do the bones of the trunk include?
6. Which organs do the ribs protect?
7. How does the wrist work?
8. How many bones are there in the framework of the wrist and hand?
The bones form the skeleton of the body. The most important part of the skeleton is the backbone. It is so important that naturalists divided animals into two classes - those which have a backbone and those which have none. All the higher animals have a backbone, or vertebral column and they are called vertebrate animals. The others are called invertebrate animals.
The bones which form the body include the bones of the head, the bones of the trunk, the bones of the lower and upper limbs.
At the upper end of the backbone there is the skull. Inside the skull there is the brain. The bones of the head include the bones which make up the box-like structure, the skull, and freely movable bone which forms our lower jaw.
The bones of the trunk include the spinal column, the ribs and the breastbone. The ribs form a strong cage - the chest, inside of which there is the heart and the lungs.
The arms join the body at the shoulder, and the shoulder consists of two bones – the collar-bone and the shoulder-blade. In the wrist there are eight small bones. They are bound together, but their large number allows the wrist to bend freely. Next come the bones of the hand itself. There are five long bones in the palm. Each of the fingers has three bones, and the thumb has two. Thus we have twenty-seven bones in the framework of the hand and wrist alone.
II. The Cardiovascular System. Blood.
1. What is the circulatory system?
2. What is the center of the circulatory system?
3. Where does the heart lie?
4. How many chambers does the heart have?
5. What are the functions of the left and the right ventricles?
6. Name four valves in the heart. In which parts of the heart are they situated?
7. Which types of vessels do you know?
8. What is the artery, the vein, the pulmonary artery, the pulmonary vein?
9. What is the blood?
10. Which types of blood cells do you know?
The heart, lungs and blood vessels make up the circulatory system (the cardiovascular system) of the human body. The center of the circulatory system is the heart. It lies in the thoracic cavity, just behind the breastbone and between the lungs. The heart consists of four chambers – the left atrium and the left ventricle, and the right atrium and the right ventricle. The heart is a hollow muscle, which also has four valves.
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The left atrium of the heart receives oxygen-rich blood from the lungs and then empties into the left ventricle through the mitral valve. The left ventricle pumps oxygen-rich blood out to the rest of the body. Blood leaves the left ventricle through the aortic valve and enters the aorta. It then flows from the aorta into the branches of many smaller arteries , providing the body’s organs with the oxygen. The smallest arteries are the arterioles, which divide into capillaries. An artery is a blood vessel that takes blood away from the heart to all parts of the body. Oxygen in the blood is released to the tissues, the deoxygenated blood returns to the heart through the veins. Veins are blood vessels that carry blood towards the heart. (Pulmonary veins are the veins that transfer oxygenated blood from the lungs to the heart.) This blood enters the right atrium of the heart and then travels across the tricuspid valve into the right ventricle. The right ventricle then pumps deoxygenated blood through the pulmonic valve into the lungs.
The blood is a red fluid, which clots when escapes from a blood vessel. It mainly consists of plasma, leucocytes, lymphocytes, erythrocytes, and platelets. Platelets are tiny blood cells that help your body form clots to stop bleeding. Erythrocytes (or red blood cells) provide oxygen to tissues, lymphocytes form our immune system, and leucocytes (or white blood cells) defend the organism from infection.
III. The Respiratory System. Respiration.
1. Why is respiration so important?
2. What gases are involved in breathing?
3. What parts of the respiratory system does the air pass on its way to the alveoli?
4. Describe the mechanism of breathing.
5. What is inhalation/exhalation?
6. How many respiratory movements do the people do?
7. When does increased respiration occur?
Respiration is the process of breathing, which occurs in all living things, both plants and animals. It is important, because it sustains life, and interruption of breathing causes death. Breathing includes two main gases: oxygen which is delivered to body cells and carbon dioxide which is removed from the organism. Nitrogen, which makes up about 79 per cent of the atmosphere, is not involved in the breathing process.
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Air is breathed through the mouth or nose into the oral cavity, or pharynx. It then passes through the voice box, or larynx, into the windpipe, or trachea. The trachea divides into two smaller tubes, bronchi, one is going to each lung. The bronchi divide into bronchioles, which lead directly to alveoli. The exchange of life-giving gases is effected through the walls of the alveoli.
Respiration consists of rhythmically repeated inhalations and exhalations. An inhalation involves a contraction of muscles, an expansion of the lungs, and entrance of atmospheric air into the lungs through the air passages. Inhalation is followed by exhalation. The muscles relax, the lungs become compressed, the pressure in them rises and the air rushes out through the air passages.
An adult makes 16-20 respiratory movements per minute, children make more movements. Physical exercise is usually accompanied by faster respiration. Increases respiration is also observed in many diseases.
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