Question

11. Which of the following about human red blood cells is false:  

a. They are generated by stem cells in bone marrow.

b. They lack nuclei when mature.

c. They tend to rupture as they get older and less flexible.

d. Erythropoietin controls their production.

C. Their biconcave shape yields a small surface area.

12. A child falls off his bicycle and skins his knee. All the following processes are involved in the formation of the blood clot that seals the wound except

a. formation of a clot in a fibrin mesh.

b. platelets sticking to exposed collagen fibers at the wound site.

c. clotting factors being activated by platelets,

d. activation of thrombin.

e. cleavage of fibrinogen into fibrin threads by prothrombin.

13. Which of the following about arterioles is false?

2. They have smooth muscle cells in their walls that control diameter and resistance.

b. They are called resistance vessels because their resistance can vary, allowing them to control blood flow to tissues.

c. Their velocity of blood flow is lower than that of arteries.

d. Their total area is larger than that of capillaries.

e. Their mean blood pressure is lower than that of arteries.

14. Which statement about capillaries is false?

a. Osmotic pressure pulls fluid back into capillaries.

b. Blood osmotic pressure is due to the large protein molecules that leave capillaries, taking fluid with them.

c. Blood pressure squeezes fluid out of capillaries.

d. Blood hydrostatic pressure is high at the arterial end of a capillary bed.

e Bicarbonate ions help pull fluid back into capillaries.

15. All the following facilitate the return of blood to the heart except

2. gravity, when veins are above the heart.

b. muscles involved in inhalation.

c. one-way valves that prevent backflow.

d. Squeezing of veins by contractions of smooth muscles of the digestive tract.

e. squeezing of veins by contractions of surrounding skeletal muscles.

Answer 1

1- A their biconcave shape yields a smaller surface area.

2- cleavage of fibrinogen into fibrin threads by prothrombin

3- Their velocity of blood flow is lower than that of arteries

4- Bicarbonate ions help pull fluid back in capillaries

5- squeezing of the veins by contraction of smooth muscles of the digestive tract.