What is the function of fibrin?
Fibrin creates the framework of a blood clot.
Fibrin, released from platelets, attracts other platelets.
Fibrin stimulates cell division.
Fibrin activates prothrombin.
Fibrin dissolves blood clots after tissue repair is complete.
The Correct Answer is A
Choice A rationale
Fibrin is a crucial protein in the coagulation cascade. It is formed from fibrinogen by the enzyme thrombin. Fibrin polymerizes to form a mesh-like network that traps red blood cells and platelets, creating the structural framework of a stable blood clot, effectively sealing off damaged blood vessels and preventing further blood loss.
Choice B rationale
While platelets are involved in coagulation, fibrin itself is not released from platelets to attract other platelets. Platelets release various factors like ADP and thromboxane A2 to aggregate. Fibrin's role is structural, forming the clot framework after platelet plug formation.
Choice C rationale
Fibrin does not directly stimulate cell division. Its primary role is in hemostasis and clot formation. Cell division, or mitosis, is regulated by growth factors and signaling pathways independent of fibrin's direct action, although clot removal is part of wound healing.
Choice D rationale
Fibrin is a product of prothrombin activation, not an activator of prothrombin. Prothrombin is converted into thrombin by prothrombinase, and thrombin then acts on fibrinogen to produce fibrin, which then forms the clot. The sequence is critical for proper coagulation.
Choice E rationale
Fibrin is the main component of a blood clot and needs to be dissolved for tissue repair to be complete. However, fibrin itself does not dissolve blood clots. Fibrinolysis, the process of clot dissolution, is mediated by plasmin, an enzyme that degrades fibrin.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice D rationale
Hyposecretion, or inadequate hormone release, can indeed result from a combination of factors. Tumors or lesions directly destroying glandular tissue (primary hyposecretion), interference with the gland's ability to receive stimulating signals (secondary hyposecretion), or inadequate trophic hormone stimulation from a higher center all lead to insufficient hormone production.
Choice A rationale
Tumors or lesions that destroy an endocrine gland directly impair its ability to synthesize and secrete hormones, leading to primary hyposecretion. For example, damage to pancreatic islet cells can cause insufficient insulin production, leading to diabetes mellitus.
Choice B rationale
Tumors or lesions that interfere with a gland's ability to receive signals from another gland, such as the pituitary, result in secondary hyposecretion. If the adrenal cortex cannot respond to ACTH due to receptor damage, it will not produce sufficient corticosteroids.
Choice C rationale
Inadequate stimulation of the gland, such as insufficient release of a trophic hormone from the pituitary or hypothalamus, leads to insufficient hormone production. For example, if the pituitary does not release enough TSH, the thyroid gland will exhibit hyposecretion of thyroid hormones.
Correct Answer is A
Explanation
Choice A rationale
Glycogen is the storage form of glucose, primarily found within cells, particularly liver and muscle cells, as a readily accessible energy reserve. It is a polysaccharide, and its presence in plasma is not typical because glucose is the primary circulating carbohydrate, maintained at a narrow homeostatic range (normal fasting plasma glucose: 70-99 mg/dL or 3.9-5.5 mmol/L) for cellular energy.
Choice B rationale
Fibrinogen is a soluble plasma protein synthesized by the liver, crucial for hemostasis. Upon activation by thrombin, it polymerizes into insoluble fibrin strands, forming the structural meshwork of a blood clot, essential for stopping bleeding. Its normal concentration in plasma is approximately 200-400 mg/dL.
Choice C rationale
Glucose is a monosaccharide, the body's main source of energy, and is transported in the plasma to cells throughout the body for metabolic processes. Its concentration is tightly regulated by hormones like insulin and glucagon to ensure adequate cellular fuel while preventing hyperglycemia or hypoglycemia.
Choice D rationale
Urea is a metabolic waste product derived from the breakdown of proteins, specifically from the deamination of amino acids in the liver. It is transported in the plasma to the kidneys for excretion in urine, playing a vital role in nitrogenous waste elimination. Normal blood urea nitrogen (BUN) levels range from 7-20 mg/dL.
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