Transport in Humans

Which blood vessel carries oxygenated blood from the lungs to the heart?

• • Pulmonary artery

• • Vena cava

• • Aorta

• • Pulmonary vein

What is the main function of platelets in blood?

• • Produce antibodies

• • Help in blood clotting

• • Fight infection

• • Transport oxygen

Which statement about blood plasma is correct?

• • It is responsible for blood clotting

• • It makes up 75% of blood volume

• • It transports carbon dioxide, nutrients, and hormones

• • It contains only dissolved proteins

: During the cardiac cycle, when do the heart sounds occur?

• • When the heart muscle relaxes

• • When the heart valves close

• • When blood leaves the ventricles

• • When blood enters the atria

Why do veins have valves while arteries don't?

• • Arteries don't need to maintain blood flow

• • Arteries have thinner walls than veins

• • Valves would interfere with arterial blood flow

• • Blood in veins is at lower pressure and needs help returning to the heart

During tissue fluid formation, which process occurs?

• • Complete filtration of blood

• • Osmosis of water into blood vessels

• • Active transport of materials into tissue spaces

• • Blood pressure forces plasma out of capillaries

Why do capillaries have thin walls?

• • To maintain high blood pressure

• • To prevent tissue fluid formation

• • To allow efficient exchange of materials

• • To prevent blood loss

During the cardiac cycle, when does the highest pressure occur in the left ventricle?

• • During late diastole

• • During ventricular systole

• • During early diastole

• • During atrial systole

What is the correct sequence of events in blood clotting?

• • Fibrinogen disappears → platelets dissolve → clot forms

• • White blood cells gather → platelets form → clot develops

• • Fibrin forms → platelets gather → fibrinogen appears

• • Platelets gather → fibrinogen converts to fibrin → blood clot forms

A person has atherosclerosis. Which statement is most likely true?

• • Their coronary arteries have a narrowed lumen

• • Their veins have become more elastic

• • Their capillaries have thickened walls

• • Their arteries have become more flexible