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2. Circulation and respiration
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Circulation and respiration 2
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3. The circulatory system
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The circulatory system 3
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4. Functions of the circulatory system
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Functions of the circulatory system
In animals, the circulatory systems has three functions:
transport of gases, nutrients, metabolic waste, hormones;
thermoregulation;
defense (transport of cells and chemicals that help fight against attacks from pathogens). 4
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5. Structure of the circulatory system
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Structure of the circulatory system
The human circulatory system (or cardiovascular system) consists of the heart, blood vessels and blood.
The heart is a muscle organ, divided into two atria (right and left) and two ventricles (right and left).
The blood is pumped from the heart into arteries and returns to the heart through veins.
left
atrium
left
ventricle
right
ventricle
right atrium 5
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6. Pulmonary and systemic circulation
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Pulmonary and systemic circulation
Pulmonary circulation transports blood from the heart to the lungs, where it is oxygenated and then returns to the heart.
Systemic circulation transports blood from the heart to the rest of the body. 6
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Structure of the heart
The walls of the heart are made up of three layers:
the endocardium is formed by endothelial tissue;
the myocardium is formed by muscle tissue;
the epicardium is formed by a protective membrane. 7
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8. The cardiac cycle During a cardiac cycle, two phases alternate:
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The cardiac cycle
During a cardiac cycle, two phases alternate:
a relaxation phase (diastole);
a contraction phase (systole).
The heartbeat is controlled by electrical activity generated by the heart itself in the senatorial node (a natural pacemaker).
The senatorial node spontaneously induces the rhythmic and regular contractions of the heart. 8
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Blood vessels
Blood vessels include arteries, veins and capillaries – each have different structures and functions.
Arteries transport blood from the heart to the lungs and the rest of the body. They have thick and elastic walls.
Veins transport blood back to the heart. They have thinner and less elastic walls.
Capillaries have very thin walls which allow the exchange of gases and nutrients. Capillaries control the blood flow to organs. 9
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Blood
Blood contains cells (white cells, red cells and platelets), that are suspended in plasma.
Red cells (erythrocytes) specialize in the transport of respiratory gases. They also contain hemoglobin.
White cells (leucocytes) are dedicated to the defense of the organism and are the main component of the immune system.
Platelets are not real cells, but cell fragments. They allow blood clotting and repair damaged vessels. 10
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11. Lymphatic system The lymphatic system supports the circulatory system:
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Lymphatic system
The lymphatic system supports the circulatory system:
it collects fluids that filter from the capillaries;
it transports white blood cells, defending the body against pathogens;
it collects nutrients. 11
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12. The respiratory system
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The respiratory system 12
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13. Functions of the respiratory system
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Functions of the respiratory system
The respiratory system is responsible for pulmonary ventilation and the exchange of gases with cells. Inside cells, cellular respiration takes place.
organ
lungs
blood
blood O2 O2
CO2
CO2 13
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14. Anatomy of the respiratory system
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Anatomy of the respiratory system
The respiratory system includes:
the upper respiratory tract (nose, mouth, pharynx, larynx);
the lower respiratory tract (trachea, bronchi);
the lungs, that contain alveoli where the exchange of gases occurs. 14
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15. Pulmonary ventilation
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Pulmonary ventilation
In humans, pulmonary ventilation (breathing) has two phases:
during inspiration (or inhalation), air enters the lungs;
during expiration (or exhalation), air exits the lungs.
These phases depend on changes of pressure inside the rib cage.
Control of the rhythm of ventilation is involuntary, but can also be modified voluntarily. 15
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Hemoglobin and oxygen
Hemoglobin located in red blood cells takes on oxygen at the level of the lungs and then transports it through the blood stream to all the parts of the body.
Hemoglobin releases oxygen once it reaches tissues.
Myoglobin, located in muscle cells, can also carry oxygen.
It is a reserve of oxygen during intense efforts or during apnea. 16
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