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What is the principal cation of the ECF?

A.

Na+

B.

Ca2+

C.

CL-

D.

K+

Answer and Explanation

The Correct Answer is A

A. Na+: Sodium (Na+) is the principal cation in the extracellular fluid (ECF), which includes interstitial fluid and blood plasma. 

 

B. Ca2+: Calcium (Ca2+) is important in various bodily functions but is not the principal cation in the ECF. Sodium is more predominant in ECF.

 

C. Cl-: Chloride (Cl-) is the principal anion in the ECF, not a cation. Sodium is the principal cation. 

 

D. K+: Potassium (K+) is the principal cation in the intracellular fluid (ICF), not the ECF. Sodium is the principal cation in the ECF.


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Correct Answer is B

Explanation

A. 20,000 to 30,000: This number is too high for the typical number of sperm that reach the vicinity of the egg.

B. 20 to 200: This number is within the range of the actual number of sperm that typically reach the vicinity of the egg.

C. Half: This is an exaggerated number, as far fewer than half of the ejaculated sperm reach the vicinity of the egg.

D. 2000 to 3000: This number is too high for the typical number of sperm that reach the vicinity of the egg.

Correct Answer is D

Explanation

A. To the lining of the uterine tube: If an embryo attaches to the uterine tube, it results in an ectopic pregnancy, which is not typical or safe.

B. To the myometrium: The myometrium is the muscular layer of the uterus and is not the usual site of embryo attachment.

C. To the perimetrium: The perimetrium is the outermost layer of the uterus and is not involved in embryo implantation. This is incorrect.

D. To the endometrium: The endometrium is the inner lining of the uterus, where the embryo typically implants and attaches. This is the correct answer.