BIO 161 Lecture questions fpr final exam

Why is blood circulation necessary even when red blood cells already contain O₂?

Blood must be moved to tissues so O₂ and nutrients can be delivered and wastes removed.

Which route correctly describes pulmonary circulation?

Right heart → lungs → left heart

 A red blood cell leaves a systemic capillary bed and returns toward the heart. Which chamber does it enter first?

Right atrium

Which blood vessels make the most direct adjustments to resistance and local tissue blood flow?

 Arterioles

An artery and a vein of similar overall size are compared. Which feature best matches their different functions?

The artery has a thicker muscular/elastic wall; the vein generally has a larger lumen and lower pressure.

In a simplified model, two vessel beds have equal resistance. One has a pressure difference of 80 units and the other 40. What is the expected comparison?

 The 80-unit pressure difference produces about twice the flow.

 If an arteriole constricts while the driving pressure difference remains the same, what happens to blood flow through that tissue bed?

 Resistance rises and flow decreases.

 Two arterioles supply different tissues under the same pressure difference. Which prediction is best?

Arteriole A permits more flow than B because it has a wider lumen and lower resistance.

A runner starts an uphill climb. How can working leg muscles receive more blood within seconds?

 Local arterioles dilate, lowering resistance to the active muscle beds.

Why are capillaries well suited for exchange with nearby tissue cells?

Their thin walls create a short diffusion distance for gases and other small substances.

At a systemic tissue capillary, which direction of gas movement is most typical?

 O₂ moves from blood toward tissue; CO₂ moves from tissue toward blood.

A patient has very low plasma albumin and begins to accumulate fluid in the tissues. What is the most relevant mechanism?

Lower plasma oncotic pressure opposes outward filtration less effectively.

What is the primary role of lymphatic vessels in the brief fluid-balance pathway covered in lecture?

. Collect excess interstitial fluid and return it to the blood.

Why does contraction of the calf muscles help blood return from the legs?

 The muscles compress veins, and one-way venous valves limit backward flow.

During inspiration, thoracic pressure generally falls. How can this affect venous return?

 It can help favor movement of venous blood toward the chest and heart.

 Why is the left ventricular wall thicker than the right ventricular wall?

The left ventricle must generate higher pressure for systemic circulation.

When ventricular pressure first rises above atrial pressure, what normally happens?

The atrioventricular (AV) valves close, limiting backflow into the atria.

What must happen for a semilunar valve to open and blood to leave a ventricle?

Ventricular pressure must exceed pressure in the corresponding artery.

Which systemic vessel region shows the steepest pressure decline in the simplified trace?

Arterioles

A coronary artery becomes severely narrowed. Which downstream effect most directly threatens the heart’s pumping ability?

Less O₂ reaches myocardium, limiting the ATP needed for cardiac muscle contraction.