Sistema circulatorio en ingles.

Questionnaire on circulatory system

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Student: Alegre Diego

Subject: Biology

Hand-in date: 11/4/2016

1. Why do large organisms need a transport system? FUNCTIONS of the blood

Answer: Large organisms need a transport system to carry all the substances (amino acids, glucose, proteins, etc.) that are needed in all living cells(such as the brain cells, leg muscle cells and kidney cells). The blood has three main functions: it works as the agent replenishing the tissue fluid surrounding the cells, as a circulatory transport system and as a defence mechanism against harmful bacteria, viruses and foreign proteins.

1. List the components of the blood, their function, where they are made and their structure.

Answer: Blood consists of red cells white cells and platelets floating in liquid called plasma. Red cells are disc-like cells that do not have nuclei, made of spongy cytoplasm enclosed in an elastic cell membrane. In their cytoplasm is their red pigment called haemoglobin (a protein combined with iron). Haemoglobin can be combined with oxygen in places where there is a high concentration of oxygen, to form oxyhaemoglobin. Oxyhaemoglobin breaks down and releases oxygen in places where oxygen concentration is low; this makes haemoglobin very useful in carrying oxygen from the lungs to the tissues. Blood which contains mainly oxyhaemoglobin is oxygenated. Blood with little oxyhaemoglobin is called deoxygenated. Red cells are made by the red bone marrow of certain bones in the skeleton (in the ribs, vertebrae and breastbone for example).

There are several different kinds of white cells. Most are larger than the red cells and have a nucleus. There is one white cell of every 600 red cells (they are made in the same bone marrow that makes red cells. Many of them go through a process of maturation and development in the thymus gland, lymph nodes or spleen. The two most numerous types of white cells are phagocytes and lymphocytes. Phagocytes can move about by a flowing action of their cytoplasm and can escape from the blood capillaries into the tissues by squeezing between the cells of the capillary walls. They collect at the site of an infection, engulfing and digesting harmful bacteria and cell debris, by doing this they prevent the spread of infection through the body. The lymphocytes mainly produce antibodies.

The platelets are pieces of special blood cells buffed off in the red bone marrow; they help in the coagulation of blood at wounds and so stop the bleeding.

Plasma is the liquid part of the blood; it is water with a large amount of dissolved substances in it (the ions of sodium, potassium, calcium, chloride, and hydrogen carbonate, among others are present).

 An important part of the plasma is constituted by proteins (fibrinogen, albumin, and globulins); fibrinogen is needed for clotting and the globulin proteins include antibodies, which combat bacteria and other foreign matter.

1. What is a double circulatory system?

Answer: The double circulatory system is the whole circuit around the body, which has two circuits: the circulation through the lungs is called the pulmonary circulation and the circulation through the rest of the body is called the systemic circulation.

1. Draw a heart and name its chambers. Explain the journey of the blood. Where does it become oxygenated? Which side of the heart contains oxygenated blood?

Answer: The journey of the blood begins when it enters the atria (thin-walled chambers in the upper part of the heart) from large veins. The pulmonary vein brings oxygenated blood from the lungs into the left atrium. The vena cava brings deoxygenated blood from the body tissues into the right atrium. The blood passes from each atrium to its corresponding ventricle, and the ventricle pumps it out into the arteries. The artery carrying oxygenated blood to the body from the left ventricle is the aorta. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. In pumping the blood, the muscle in the walls of the atria and ventricles contract and relaxes. The walls of the atria contract first and force blood into the two ventricles. Then the ventricles contract and send blood into the arteries. The blood is stopped from flowing backwards by four sets of valves. Between the right atrium and the right ventricle is the tricuspid (=three flaps) valve. Between the left atrium and left ventricle is the bicuspid (=two flaps) valve. The flaps of these valves are shaped rather like parachutes, with tendons or chords to prevent their being turned inside out. In the pulmonary artery and aorta are the semi-lunar valves. These consist of three pockets which are pushed flat against the artery walls when blood flows one way. If blood tries to flow the other way, the pockets fill up and meet in the middle to stop the flow of blood. When the ventricles contract, blood pressure closes the bicuspid and tricuspid valves and these prevent blood returning to the atria. When the ventricles relax, the blood pressure in the arteries closes the semi lunar valves so preventing the return of blood to the ventricles. When the ventricles relax, their internal volume increases and they draw in blood from the pulmonary vein or vena cava through the relaxed atria. Atrial contraction then forces the final amount of blood into the ventricles just before ventricular contraction.

1. Why do the ventricles have thicker walls than the atria? Why does the left ventricle have a thicker wall than the right ventricle?

Answer: Because when the ventricles contract they send the blood to the lungs (right ventricle) and to the rest of the body (left ventricle), so they require more pressure to propel the blood out of the heart. The left ventricle has a thicker wall because it needs to propel blood to the rest of the body, unlike the right ventricle, that only sends blood to the lungs.

1. What’s the function of the coronary arteries?

Answer: The function of the coronary arteries is to supply the heart muscle with food and oxygen.

1. What is systole and what is diastole? What is the normal heart rate? What does it depend on?

Answer: Systole is the part of the cardiac cycle when the ventricles contract and the diastole is the part of the cardiac cycle when the heart refills with blood after systole occurred. The normal heart rate is between 50 and 100 beats per minute, depending on age, sex and other factors.

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