What causes the "lub" sound in the heart?

• The relaxation of the heart muscle.

• The contraction of the atria.

• The closing of valves between the atria and ventricles.

• The closing of valves between the ventricles and large blood vessels.

Which type of blood vessel is characterized by being thick, muscular, and elastic, and carries oxygen-rich blood from the heart to the rest of the body?

• Veins

• Capillaries

• Arteries

• Lymphatic vessels

Which of the following substances is primarily transported by blood plasma?

• Oxygen

• Hemoglobin

• Nutrients and waste products

• White blood cells

What is a key characteristic of red blood cells (erythrocytes) that allows them to maximize oxygen transport?

• They are produced in the bone marrow.

• They have a biconcave shape and lack a nucleus.

• They are made of hemoglobin, which contains iron.

• They have a lifespan of approximately 120 days.

What is the primary function of thrombocytes in the human body?

• Transporting oxygen to cells.

• Fighting off infections.

• Initiating blood clotting to stop bleeding.

• Producing antibodies.

How many times does blood pass through the heart in one complete cycle of human blood circulation?

• Once

• Twice

• Three times

• Four times

What is the main characteristic of atherosclerosis?

• High blood pressure due to increased heart rate.

• Plaque buildup on artery walls, hardening and narrowing them.

• Rupture of blood vessels in the brain.

• Insufficient oxygen supply to the lungs.

Why is hypertension often referred to as a "silent killer"?

• It only affects people who are physically inactive.

• It causes immediate and severe pain.

• It often has no noticeable symptoms until severe damage occurs.

• It is easily cured with over-the-counter medication.