THE CIRCULATORY SYSTEM:
It´s
the system that circulates blood and lymph through the body. It collects and
distributes substances that the cells need and eliminates waste from the cells.
The circulatory system is composed of two systems:
/ The blood circulatory system: carries oxygen and nutrients and removes waste metabolic
products. The circulating fluid is blood. It´s made up of: blood, blood
vessels and heart.
/ The lymphatic system: removes
excess
fluids from body tissues, absorbs the fatty acids from the small intestine to
the blood and produces immune cells (such as lymphocytes, monocytes, and
antibody producing cells called plasma cells). It is made up of: lymph
capillaries, lymphatic vessels and lymph nodes.
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It´s a thick red liquid that circulates in the arteries and veins of humans and other vertebrate animals. About 7 to 8 percent of your total body weight is blood.
Blood is made up of:
/
Blood plasma: it constitutes approximately 55% of total blood volume. It´s a
yellowish liquid composed of water and disolved substances. The main role of
plasma is to take nutrients,
hormones, and proteins to the parts of the body that need it, also
clotting and defence through the immune system.
/ Blood cells: it constitutes approximately 45% of blood volumen. They are formed in the red bone marrow. Blood cells are: platelets (clotting), erythrocytes (transport oxygen to the cells and pick up carbon dioxide for elimination) and leycocytes (protect the body against infection and foreign substances).
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The
main functions of the blood are:
- / Transport
substances: nutrients and oxygen from digestive track and respiratory system to
the tissues. It also collects waste and carbon dioxide for elimination.
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- / Defence:
carrying cells, certain proteins and antibodies that fight infection and
protect the body.
- / Control
of bleeding: forming blood clots to prevent excess blood loss with platelets
and plasma proteins.
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- / Regulate
body temperature: the blood mantains the body temperatura at about 37ºC.
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BLOOD VESSELS
They are a network of
tubular ducts responsible for transporting blood from the heart to the tissues
and vice versa.
There are three
kinds of blood vessels: arteries, veins, and capillaries. Each
of these plays a very specific role in the circulation process.
/ ARTERIES: carry oxygenated blood away from the heart to
the organs. They’re tough on the outside but they contain a smooth interior
layer of epithelial cells that allows blood to flow easily. They are called
arterioles when they are farther from heart.
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/ VEINS: carry the blood back from the organs to the
heart. They’re similar to arteries but not as strong or as thick. Unlike
arteries, veins contain valves that ensure blood flows in only one direction (arteries
don’t require valves because pressure from the heart is so strong that blood is
only able to flow in one direction.) Valves also help blood travel back to the
heart against the force of gravity. They are called venules when they are
farther from heart.
/ CAPILLARIES: connect the arteries to veins in tissues. It facilitates the exchange of gases, waste and nutrients between the blood, cells and intersticial plasma.
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THE HEART
The
heart is a muscular organ that pumps the blood through the circulatory system
by rhythmic contraction and dilation. It´s between the lungs, just to the left
of the sternum. Its walls are made of myocardium (cardiac muscle that pumps the
blood).
The
heart consists of four chambers:
- The atria: These
are the two upper chambers, which receive blood.
- The ventricles: These
are the two lower chambers, which discharge blood.
The
chambers on the same side are connected: tricuspid valve connects the right
atrium and the right ventricle and the mitral valve connects the left atrium
and left ventricle. This valves open to let blood in and close to prevent it from flowing backwards.
The RIGHT SIDE OF THE HEART receives deoxygenated blood and sends it to the lungs.
/ The right atrium receives deoxygenated
blood from the body through superior and inferior cava veins.
/ The
right atrium contracts, and blood passes to the right ventricle.
/
When the right ventricle is full, it contracts and pumps the blood to the lungs
via the pulmonary artery. In the lungs, the blood picks up oxygen and expell
carbon dioxide.
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The LEFT SIDE OF THE HEART receives blood from the lungs and pumps it to the rest of the body.
- Oxygenated blood
returns to the left atrium via the pulmonary veins.
- The left atrium
contracts, pushing the blood into the left ventricle.
- Once the left
ventricle is full, it contracts and pushes the blood back out to the body
via the aorta.
THE
CARDIAC CYCLE
Each
heartbeat has two parts:
Systole: movement of contraction.
/ Atrial systole: atria contract and push blood
through the valves (mitral and tricuspid) into the ventricles. Ventricles fill
with blood.
/ Ventricular systole: ventricles contract, the
valves (pulmonary and aortic) open and blood passes to the pulmonary artery
and aorta.
Diastole: The
ventricles an atria relax, the atria fill with blood, the valves (mitral and tricuspid) open and the ventricles fill
with blood.
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CARDIOVASCULAR DISEASES
They
are diseases that affect the blood vessels or the heart of the circulatory
system:
Some
of them are:
/
Myocardial infarction.
/ Angina pectoris: is a crushing pain or discomfort in the chest. It happens when some part of your heart doesn't get enough blood and oxygen. Angina can be a symptom of coronary artery disease (CAD). There may also be pain in the shoulders, arms, neck, jaw, or back.
/ Heart failure: occurs when there is an imbalance between
the heart's ability to pump blood and the body's needs.
/ Pulmonary thromboembolism (PTE): is the occlusion or
blockage of a part of the pulmonary artery due to an embolus or thrombus that
comes from another part of the body.
/ Atrial fibrillation: irregular and abnormal heart rhythm.
/ Valvulopathies: diseases of the heart valves due to infections,
trauma, aging, etc.
/ Arrhythmia: disturbance of heart rhythm.
/
Atherosclerosis: the walls of the artery become hard and thick with less
elasticity. It causes narrowing (stenosis) of the arteries that can progress to
the occlusion of the vessel, preventing the proper flow of blood through the
affected artery. It is produced by plaques (mainly cholesterol) that can
break and detach causing an embolism.
/ Hypertension:
arterial tension is the pressure of the blood that circulates through the
arteries. If the pressure is high, the arteries can be damaged and have to work
harder. Normal blood pressure is 120mmHg (systolic) over 80mmHg (diastolic).
HEALTHY HABITS FOR THE CIRCULATORY
SYSTEM
The healthy habits for our circulatory system to work
properly are:
/ Balanced and varied heart-healthy diet. You have to eat
fruits, vegetables, vegetables, fish, olive oil, lean meats, cereals and
skimmed dairy products. Avoid high-fat diets. Remember: salt and sugar in small
quantities.
/ Physical activity adapted to physical condition: aerobic
exercises such as: walking, dancing, running, outdoor activities...
/ Do not smoke because it increases blood pressure and
multiplies the risk of heart attacks. It is also a risk factor for atherosclerosis.
/ Check your blood pressure.
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/ Check your cholesterol and glucose levels. The best way to keep them well is to follow a healthy diet and exercise.
/ Control your stress and anxiety. Increased emotional
tension is dangerous for the heart.
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Drink at least two litres of water every day because it helps dilute and
eliminate waste from the body.
