The thin segment of the nephron loop's descending limb
is easily broken and replaced often
aids in the passive movement of water out of the tubule
aids in the passive excretion of nitrogenous waste
helps to pack a greater number of nephron loops into a smaller space
The Correct Answer is B
A. is easily broken and replaced often: The epithelial cells of the nephron loop are durable and maintained through normal cellular repair mechanisms. They are not designed to be "broken" or frequently replaced as a standard part of renal function. The structural integrity of the tubule is essential for maintaining the osmotic gradients in the medulla.
B. aids in the passive movement of water out of the tubule: The descending limb of the nephron loop is composed of simple squamous epithelium that is highly permeable to water but relatively impermeable to solutes. As filtrate descends into the hypertonic renal medulla, water moves out of the tubule by osmosis. This process significantly concentrates the tubular fluid.
C. aids in the passive excretion of nitrogenous waste: The primary role of the thin descending limb is water conservation rather than the excretion of wastes like urea or creatinine. Nitrogenous waste excretion occurs primarily through filtration at the glomerulus and secretion in the convoluted tubules. The loop focuses on the concentration and dilution of urine.
D. helps to pack a greater number of nephron loops into a smaller space: The thinness of the segment refers to the height of the epithelial cells (simple squamous) rather than the overall diameter of the tube for packing purposes. This anatomical design is a functional adaptation for rapid osmotic diffusion. It allows for the concentration of urine without requiring active transport in this segment.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. uterus: While the uterus houses the developing fetus, it is the organ within which the nutritive interface is formed. The uterine wall itself provides the environment, but it does not directly perform the complex metabolic exchange or hormone secretion attributed to the specialized fetal-maternal organ.
B. placenta: This temporary organ is responsible for the exchange of nutrients, gases, and wastes between the maternal and fetal blood. It also functions as an endocrine gland, secreting human chorionic gonadotropin, estrogens, and progesterone to maintain the pregnancy. It is the vital lifeline for fetal development.
C. myometrium: The muscular layer of the uterus serves primarily for the mechanical expulsion of the fetus at the end of gestation. It does not possess the transport mechanisms or secretory capacity required for fetal nutrition. Its role is structural and contractile rather than metabolic or endocrine.
D. blastocyte: This is an early developmental stage of the embryo consisting of an inner cell mass and a trophoblast. While the trophoblast eventually gives rise to the placenta, the blastocyte stage itself is too early to provide sustained nutrition. It represents the entity that is being nourished.
E. endometrium: The endometrium provides the initial site for attachment and secretes "uterine milk" for the very early embryo. However, once the placenta is established, the endometrium's role in direct nutrition is superseded by the placental circulatory interface. The placenta becomes the primary regulator of fetal growth.
Correct Answer is B
Explanation
A. neutral: A pH of 7.0 would be insufficient to protect spermatozoa from the physiological stressors of the female reproductive tract. Semen requires a specific chemical buffer to maintain the viability and motility of the gametes. Neutral solutions lack the necessary buffering capacity to counteract external acidic environments effectively.
B. alkaline: Semen typically possesses a pH ranging from 7.2 to 8.0 due to the high volume of alkaline secretions from the seminal vesicles and bulbourethral glands. This alkalinity is essential to neutralize the acidic environment of the male urethra and the female vagina. A basic environment is critical for optimizing sperm motility and survival.
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