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What are the components of the circulatory system?

A.

Heart

B.

Blood vessels

C.

Blood

D.

Heart and blood vessels

E.

Heart, blood vessels, and blood

Answer and Explanation

The Correct Answer is E

A. Heart: The heart is a central component of the circulatory system, but not the only one.
B. Blood vessels: Blood vessels (arteries, veins, capillaries) are essential, but alone they don’t make up the whole system.
C. Blood: Blood is a major component (transport medium), but not the whole system by itself.
D. Heart and blood vessels: These two form the pump and conduits, but blood (the transported fluid) is also required.
E. Heart, blood vessels, and blood:  The circulatory system consists of the heart (pump), blood vessels (conduits), and blood (transport medium).


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Related Questions

Correct Answer is {"dropdown-group-1":"D"}

Explanation

A. thymus: The thymus secretes thymosins that influence T-cell maturation (immune function), not hormones that raise blood calcium - so it does not respond to hypocalcemia.
B. thyroid gland: The thyroid’s parafollicular (C) cells secrete calcitonin, which lowers blood calcium in response to hypercalcemia, not hypocalcemia.
C. pituitary gland: The pituitary releases many trophic hormones, but it does not directly secrete the primary hormone (PTH) that corrects hypocalcemia.
D. parathyroid glands: The parathyroid glands secrete parathyroid hormone (PTH) in response to low blood Ca²⁺; PTH raises serum calcium by acting on bone, kidney, and vitamin D activation.
E. pineal gland: The pineal gland secretes melatonin to regulate circadian rhythms, not calcium homeostasis.

Correct Answer is C

Explanation

A. Granulocytes: granulocytes (neutrophils, eosinophils, basophils) are white blood cells that are part of the buffy coat.
B. Lymphocytes: lymphocytes (T cells, B cells, NK cells) are white blood cells found in the buffy coat.
C. Erythrocytes: erythrocytes (red blood cells) form the red cell layer below the buffy coat; the buffy coat contains white cells and platelets, not RBCs.
D. Agranulocytes: agranulocytes (lymphocytes and monocytes) are included in the buffy coat.

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