Nokea
One function of the placenta in a human is to
- A. surround the embryo and protect it from shock
- B. allow for mixing of maternal blood with fetal blood
- C. act as the heart of the fetus, pumping blood until the fetus is born
- D. permit passage of nutrients and oxygen from the mother to the fetus
Correct Answer: D
Rationale: The correct answer is D because the placenta serves as a barrier between the maternal and fetal bloodstreams, allowing for the exchange of nutrients, oxygen, and waste products. This is crucial for the fetus's growth and development. Choice A is incorrect because the placenta does not physically surround the embryo. Choice B is incorrect as maternal and fetal blood do not mix due to the placental barrier. Choice C is incorrect as the heart of the fetus pumps blood, not the placenta.
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A fertilized egg, which represents the first cell of a new individual, is called a(n) ________.
- A. blastocyst
- B. zygote
- C. fetus
- D. embryo
Correct Answer: B
Rationale: The correct answer is B: zygote. A zygote is formed when a sperm cell fertilizes an egg cell, marking the beginning of a new individual's development. It is the first cell of the new organism with a full set of chromosomes.
A: Blastocyst is a later stage of development after the zygote has undergone several cell divisions.
C: Fetus refers to the later stages of development when the embryo has developed recognizable features.
D: Embryo is the stage after the zygote when the cells start to differentiate into different tissues and organs.
After birth, the pressure in the pulmonary artery decreases greatly. What is the cause of this?
- A. Systemic arterial pressure increases
- B. Ductus arteriosus closes
- C. Left ventricular pressure increases
- D. Pulmonary vascular resistance decreases
Correct Answer: D
Rationale: The correct answer is D: Pulmonary vascular resistance decreases. After birth, the lungs expand and start functioning, leading to increased oxygen levels, which causes the pulmonary vascular resistance to decrease. This allows blood flow to the lungs and decreases pressure in the pulmonary artery.
A: Systemic arterial pressure increasing does not directly affect the pressure in the pulmonary artery.
B: Ductus arteriosus closing is part of the normal postnatal changes but does not directly cause the decrease in pulmonary artery pressure.
C: Left ventricular pressure increasing is a consequence of the closure of the ductus arteriosus but does not explain the decrease in pulmonary artery pressure.
Which hormone triggers ovulation?
- A. GnRH
- B. LH
- C. FSH
- D. Estrogen
Correct Answer: B
Rationale: The correct answer is B: LH (Luteinizing Hormone) triggers ovulation. Firstly, LH surge stimulates the release of the mature egg from the ovary. Secondly, it plays a crucial role in the development of the corpus luteum, which produces progesterone to prepare the uterus for potential implantation. GnRH (Choice A) is the hormone that stimulates the release of LH and FSH (Choice C) from the pituitary gland, but it does not directly trigger ovulation. Estrogen (Choice D) is involved in the regulation of the menstrual cycle and prepares the uterine lining for implantation but does not directly trigger ovulation.
The epididymis:
- A. is comm
- B. shaped;
- C. is crossed by the deferent duct (vas deferens);
- D. displays tunica albuginea on the inside;
Correct Answer: C
Rationale: Step 1: The epididymis is a structure where sperm mature and are stored.
Step 2: The deferent duct (vas deferens) carries sperm from the epididymis to the urethra.
Step 3: Since the deferent duct crosses the epididymis, choice C is correct.
Summary: Choices A, B, and D are incorrect because they do not accurately describe the anatomical relationship between the epididymis and the deferent duct.
Variations in eye color are determined by the number of pigmented cells in the:
- A. Ciliary epithelium
- B. Iris epithelium
- C. Iris stroma
- D. Corneal stroma
Correct Answer: C
Rationale: The correct answer is C: Iris stroma. The iris stroma contains melanocytes, which are responsible for producing the pigmented cells that determine eye color. These pigmented cells give the iris its color by absorbing and reflecting light. The ciliary epithelium (choice A) is not involved in determining eye color. The iris epithelium (choice B) is mainly responsible for controlling the size of the pupil, not for determining eye color. The corneal stroma (choice D) is a layer of the cornea that primarily provides structural support and transparency to the eye, but it does not play a role in determining eye color.