When the left ventricle contracts, the ________ valve is pushed open and the ________ valve closes.

Choice A rationale

The spleen is primarily involved in filtering blood, removing old red blood cells, and housing immune cells. While it plays a role in blood storage and immune responses, it is not a primary site for the synthesis of most clotting factors, which are complex proteins.

Choice B rationale

Red bone marrow is the primary site of hematopoiesis, the production of all blood cells, including platelets, erythrocytes, and leukocytes. However, it does not synthesize most of the plasma clotting factors; rather, it produces the cellular components involved in coagulation.

Choice C rationale

Perivascular tissue surrounds blood vessels and contains various cell types, including fibroblasts and adipocytes. While these tissues can contribute to local inflammatory responses or tissue repair, they are not major sites for the systemic synthesis of plasma clotting factors.

Choice D rationale

The kidneys play a vital role in blood filtration, waste excretion, and regulation of blood pressure and erythropoiesis (via erythropoietin). However, the kidneys do not synthesize the majority of the plasma clotting factors required for hemostasis.

Choice E rationale

The liver is the primary site for the synthesis of most plasma clotting factors, including fibrinogen, prothrombin, and factors V, VII, IX, X, and others. Hepatocytes in the liver are responsible for the complex protein synthesis required for the coagulation cascade, making it critical for hemostasis.

Choice D rationale

Prolactin is a hormone secreted by the anterior pituitary gland, not the hypothalamus. Its primary function is to stimulate milk production in the mammary glands after childbirth. The hypothalamus produces prolactin-inhibiting hormone (dopamine) and prolactin-releasing factors that regulate prolactin secretion.

Choice A rationale

Antidiuretic hormone (ADH), also known as vasopressin, is synthesized in the hypothalamus and then transported to the posterior pituitary for storage and release. It plays a critical role in water reabsorption by the kidneys, regulating fluid balance and blood pressure.

Choice B rationale

Oxytocin is synthesized in the hypothalamus and subsequently stored and released from the posterior pituitary gland. It is involved in uterine contractions during childbirth and milk ejection during lactation, also playing a role in social bonding.

Choice C rationale

Growth hormone-releasing hormone (GHRH) is a hypothalamic hormone that stimulates the anterior pituitary to secrete growth hormone (GH). GHRH is crucial for regulating body growth and metabolism by promoting the release of GH.