Heart and Circulation Honor

Science & Health

Requirements

What are the structures that make up the circulatory system? Illustrate and describe the main functions of each one.
Answer: The circulatory system is made up of: (1) heart — a muscular pump with 4 chambers (2 atria and 2 ventricles) that drives the blood; (2) arteries — thick-walled vessels that carry blood from the heart to the tissues (oxygenated, except in the pulmonary artery); (3) veins — thin-walled vessels with valves that bring blood back to the heart; (4) capillaries — microscopic vessels where the exchange of gases, nutrients, and waste between the blood and the cells occurs; (5) blood — a liquid tissue (plasma, red blood cells, white blood cells, and platelets) that transports oxygen, nutrients, hormones, and defenses. — The total length of the blood vessels in the human body is about 100,000 km (2.5 times the circumference of the Earth) — predominantly capillaries, with walls only 1 cell thick to allow the diffusion of gases and nutrients to the cells.
Describe the types of vessels that make up the circulatory system, illustrating each of them.
Answer: Three types of vessels: (1) arteries — thick, elastic walls, carry blood from the heart to the tissues under high pressure (oxygenated, except in the pulmonary artery); (2) veins — thinner, more flexible walls, with internal valves that prevent backflow, bring the blood back to the heart (venous, except in the pulmonary veins); (3) capillaries — microscopic vessels with extremely thin walls (a single layer of cells) that connect arteries and veins and where the exchange of oxygen, nutrients, and waste with the cells takes place. — The valves of the veins are essential in the legs, where the blood needs to rise against gravity — their failure causes varicose veins, a disease that affects about 30% of Brazilian adults according to the Brazilian Society of Angiology.
Know how to locate the following pulse points: carotid, brachial, radial, inguinal, and popliteal. Know how to measure the pulse rate of 2 people, using one of the points above.
Answer: Location: Carotid (side of the neck, next to the larynx); Brachial (medial side of the arm, near the bend of the elbow); Radial (wrist, thumb side); Inguinal/Femoral (groin, midway between the hip bone and the pubis); Popliteal (behind the knee, in the popliteal fossa). — The radial pulse is the most used in clinical practice because it is easily accessible and has low interference — using the thumb to palpate is a common mistake, since it has its own pulse that can be confused with the patient's.
Record your resting pulse, then do exercises (running, swimming, climbing stairs, etc.) for 10 minutes. Measure your pulse again immediately and 5 minutes after the exercise. Do this every day for a week, recording your results on a card or graph. Did the exercise affect your heartbeat?
Answer: The theoretical maximum rate is estimated by '220 minus age' — for a 15-year-old, the maximum is 205 bpm. Elite athletes often have a resting pulse of 40-50 bpm because of the more efficient heart developed through continuous aerobic training.
Use a stethoscope to listen to the heartbeat of a child under five years of age and of an adult. Both measurements should last exactly 60 seconds. Note the results and explain why there is a difference in the number of heartbeats of a child compared to an adult.
Answer: Cardiac output follows the formula CO = HR × SV (heart rate × stroke volume) — since children have a smaller SV, they compensate with a higher HR to maintain the same blood flow needed for growing tissues and the accelerated basal metabolism.
What are the 4 chambers of the heart? What are its 4 main valves? Illustrate.
Answer: The 4 chambers of the heart are: the right atrium (RA), the right ventricle (RV), the left atrium (LA), and the left ventricle (LV) — the atria receive the blood and the ventricles eject it. The 4 main valves are: (1) tricuspid — between the right atrium and the right ventricle; (2) pulmonary — between the right ventricle and the pulmonary artery; (3) mitral (bicuspid) — between the left atrium and the left ventricle; (4) aortic — between the left ventricle and the aorta. — The 'lub-dub' sound of the heartbeat comes from the closing of the valves: 'lub' (S1) is the closing of the atrioventricular valves (mitral+tricuspid); 'dub' (S2) is the closing of the semilunar valves (aortic+pulmonary) — a synchronized sequence of the cardiac cycle.
What is the difference between pulmonary circulation and systemic circulation?
Answer: Pulmonary circulation (or lesser circulation): right ventricle → pulmonary artery → lungs (where the blood is oxygenated) → pulmonary veins → left atrium. Its function is to carry venous blood to the lungs to oxygenate it and eliminate carbon dioxide. Systemic circulation (or greater circulation): left ventricle → aorta → the whole body (where the oxygenated blood delivers oxygen and nutrients to the cells) → vena cavae → right atrium. Its function is to carry oxygenated blood to all the tissues of the body and bring the venous blood back. In short, the pulmonary circulation is between the heart and the lungs, and the systemic circulation is between the heart and the rest of the body. — In the pulmonary artery flows VENOUS blood (low in O₂) and in the pulmonary veins flows ARTERIAL blood (rich in O₂) — the body's only exception, a reason for much confusion in exams and the reason why the naming follows the route (from/toward the heart) and not the content.
What is the name of the vessels that supply the heart itself? What is the name of the body's main artery?
Answer: The vessels that supply the heart are the coronary arteries — right coronary and left coronary — which come out of the base of the aorta just after the aortic valve and carry oxygenated blood to the heart muscle (myocardium). — The blockage of a coronary artery causes myocardial infarction — without blood supply, part of the heart muscle dies within a few minutes; each minute of delay in care increases the area of necrosis by 7.5%, the reason for the urgency of the emergency services (SAMU).
List at least 5 things that help keep the cardiovascular system healthy. Put them into practice, in case you do not already do so.
Answer: Five habits that keep the cardiovascular system healthy: (1) do regular aerobic exercise (about 30 min, 5 times a week — walking, cycling, swimming); (2) maintain a diet rich in fruits, vegetables, and fiber and low in sodium, sugar, and saturated fats; (3) do not smoke or expose yourself to smoke (secondhand smoke); (4) control your weight, blood pressure, and cholesterol; (5) avoid stress, sleep well, and drink plenty of water (avoiding alcohol). Put these habits into practice in your daily life. — The Mediterranean Diet (rich in olive oil, fish, fruits, and vegetables, with little red meat) reduces the risk of cardiovascular events by 30%, according to the PREDIMED study published in the New England Journal of Medicine in 2013.
What is cholesterol and how is it related to atherosclerosis?
Answer: Cholesterol is an essential lipid produced by the liver and also ingested in foods of animal origin, needed to form cell membranes, hormones, and vitamin D. There are two main types: LDL ('bad'), which in excess deposits on the walls of the arteries, and HDL ('good'), which removes the excess and carries it to the liver. When there is too much LDL, it accumulates on the arterial walls forming fatty plaques (atheromas) — a process called atherosclerosis. These plaques harden and narrow the arteries, reducing blood flow and potentially causing heart attack, stroke, and other cardiovascular diseases. — Statins, medications that reduce LDL, are considered the medication that saved the most lives in the 20th century — they reduce cardiovascular events by 25-30% when used by high-risk patients in continuous treatment.
What is an electrocardiogram and what is it for?
Answer: An electrocardiogram (ECG or EKG) is the graphic recording of the electrical activity of the heart, captured by electrodes attached to the skin of the chest and limbs. It is used to detect arrhythmias (abnormal rhythms), acute myocardial infarction, ischemia, hypertrophy, electrical conduction disorders (blocks), and the effects of medications. — The ECG was invented by Willem Einthoven in 1903, a discovery that earned him the Nobel Prize in Medicine in 1924 — the standard waveform we know (P-QRS-T) still uses the nomenclature he created more than 120 years ago.
Find and memorize 3 Bible verses that refer to the heart.
Answer: Three Bible verses that refer to the heart: (1) Proverbs 4:23 — 'Keep thy heart with all diligence; for out of it are the issues of life'; (2) Matthew 22:37 — 'Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind'; (3) Psalm 51:10 — 'Create in me a clean heart, O God; and renew a right spirit within me'. Memorize and recite all three by heart. — The Bible mentions the heart more than 800 times — in ancient Hebrew (lev/levav), the term means not only the organ, but the center of the will, of intelligence, and of moral decisions, the root of the human personality.
What is the lymphatic system? What are its functions?
Answer: The lymphatic system is a network parallel to the circulatory system, composed of lymphatic vessels, lymph (a transparent fluid), lymph nodes, the spleen, the thymus, the tonsils, and the bone marrow. Main functions: (1) immunity — it produces and houses B and T lymphocytes to defend the body against microorganisms; (2) drainage — it collects the excess fluid from the tissues and returns it to the blood, preventing edema; (3) fat absorption — it transports lipids and fat-soluble vitamins absorbed in the intestine (lacteal vessels); (4) filtering — the lymph nodes filter the lymph, retaining infectious agents and abnormal cells. — When a swollen node ('íngua') appears in the neck (enlarged lymph nodes), it is a sign that the lymphatic system is fighting a nearby infection — it may indicate tonsillitis, the flu, or other inflammations of the head and neck region.
Describe the main structures of the lymphatic system.
Answer: Main structures of the lymphatic system: (1) lymphatic vessels — collect the lymph from the tissues and lead it back to the blood; (2) lymph — a transparent fluid with lymphocytes and proteins; (3) lymph nodes — small organs that filter the lymph and produce antibodies; (4) spleen — filters the blood and recycles old red blood cells; (5) thymus — where T lymphocytes mature; (6) tonsils and adenoids — defend the upper respiratory and digestive tracts; (7) bone marrow — produces the defense cells (lymphocytes and other white blood cells). — The thymus is most active in childhood and progressively atrophies after puberty — that is why the defense against new diseases is better during the first years of life, when there is still strong production of naive T lymphocytes.