Which of the following substances is necessary for the absorption of vitamin B12?
Intrinsic factor
Bile salts
Pepsin
Amylase
The Correct Answer is A
A. Intrinsic factor is a glycoprotein produced by the stomach that binds to vitamin B12 and facilitates its absorption in the small intestine, particularly in the ileum. This is the correct answer.
B. Bile salts are involved in the digestion and absorption of fats, not vitamin B12.
C. Pepsin is an enzyme in the stomach that aids in the digestion of proteins but is not involved in vitamin B12 absorption.
D. Amylase is an enzyme that helps break down carbohydrates, not involved in the absorption of vitamin B12.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. Vitamin B12 is not synthesized in the skin. It is primarily absorbed through the digestive system from dietary sources such as meat and dairy products.
B. Vitamin D is synthesized in the skin when exposed to sunlight, specifically ultraviolet B (UVB) radiation, which triggers the production of vitamin D3, a precursor to the active form of vitamin D.
C. Vitamin A is obtained from dietary sources, such as fruits and vegetables, and is not synthesized in the skin.
D. Vitamin K is primarily absorbed from food and produced by bacteria in the intestines, not synthesized in the skin.
Correct Answer is D
Explanation
A. The tricuspid valve has three leaflets and is located between the right atrium and right ventricle. It closes during ventricular contraction (systole) but does not have two leaflets.
B. The pulmonic valve has three leaflets and controls blood flow from the right ventricle to the pulmonary artery. It is closed during the systolic phase but is not the correct answer for having two leaflets.
C. The aortic valve has three leaflets and controls blood flow from the left ventricle into the aorta. It also closes during systole, but it does not have two leaflets.
D. The mitral valve, also known as the bicuspid valve, has two leaflets and is located between the left atrium and left ventricle. It closes during systole to prevent backflow of blood into the left atrium.
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