Human Anatomy and Physiology: IX. Reproduction and Embryo Development

Total Questions: 6

1. Where does fertilization occur? [45th B.P.S.C. (Pre) 2001]

(a) In uterus
(b) In oviduct
(c) In ovary
(d) In vagina

Correct Answer: (b) In oviduct

Solution:Fertilization occurs at the end of the fallopian tube or oviduct away from the uterus (close to the ovary). The oviduct is the tube that links ovary to the uterus and ovulated oocyte travels down to become fertilized by sperm present in the female tract.

Fertilization is the natural life process, which is carried out by the fusion of both male and female gametes, which results in the formation of a zygote. In humans, the process of fertilization takes place in the fallopian tube or oviduct.

During this process, semen comprising thousands of sperms are inseminated into the female vagina during coitus. The sperms move towards the uterus and reach the opening of the fallopian tube. only a few sperms will succeed in reaching the opening of the fallopian tube.

The secondary oocyte releases from the matured Grafian follicle of the ovary and enters into the fallopian tube, where it is fertilized within 24 hours, after which it is released from the ovary.

Though surrounded by several sperms, the oocyte is fertilized by a single sperm. During meiosis-II, the sperm enters the secondary oocyte and completes the meiosis. After this, the secondary oocyte is known as the egg.

Both sperm and egg can show their vitality only to a limited period. Sperm is alive for 48-72 hours in a female reproductive system, whereas the egg can be fertilized for 24 hours before it is released.

2. In human beings, normally in which one of the following parts, does the sperm fertilize the ovum ? [I.A.S. (Pre) 2007]

(a) Cervix
(b) Fallopian tube
(c) Lower part of uterus
(d) Upper part of uterus

Correct Answer: (b) Fallopian tube

Solution:Fallopian tube, also called oviduct or uterine tube, either of a pair of long narrow ducts located in the human female abdominal cavity that transport the male sperm cells to the egg, provide a suitable environment for fertilization and transport the egg from the ovary, where it is produced.

3. After reaching the female genital tract, human sperms retain their fertilizing capacity for - [U.P.P.C.S. (Mains) 2010]

(a) Two minutes
(b) Twenty minutes
(c) Ninety minutes
(d) One to two days

Correct Answer: (d) One to two days

Solution:A sperm remains alive for up to about 72 hours after entering into oviduct but its capacity to fertilize the ovum lasts for about 48 hours (2 days).

The "fertile window" is the period around ovulation when a woman can get pregnant. This window generally lasts for about 5 days, including 5 days before ovulation and the day of ovulation, with the best chances of fertilization occurring on the day of ovulation. An egg released during ovulation can only be fertilized for a short period, typically within 12-24 hours after ovulation.Having intercourse within the fertile window, particularly within the 2-day window of the egg's lifespan, greatly increases the chances of conception.

4. The heart of human embryo starts beating [I.A.S. (Pre) 1994]

(a) In the first week of development
(b) In the third week of its development
(c) In the fourth week of its development
(d) In the sixth week of its development

Correct Answer: (c) In the fourth week of its development

Solution:About 4-5 weeks after fertilization, when the heart first begins to beat, the sound of the little heart is too soft to hear. In 4 weeks, the heart typically beats between about 105 to 121 times per minute.

The heartbeat can be seen and often heard with a transvaginal ultrasound as early as 6 weeks after fertilization. Ultrasound is crucial for early detection and confirmation of a heartbeat, as it provides a visual representation of the cardiac activity. While a heartbeat may be detectable with transvaginal ultrasound at 6 weeks, it's typically not audible with a Doppler until around 8-10 weeks.

5. Which one of the following is a membrane that protects the developing embryo from desiccation? [I.A.S. (Pre) 1995]

(a) Amnion
(b) Allantois
(c) Chorion
(d) Yolk sac

Correct Answer: (a) Amnion

Solution:The amnion is a membrane that covers the embryo. It is filled with the amniotic fluid which causes the amnion to expand and become the amniotic sac which serves to provide a protective environment for the developing embryo.

6. In which organ sertoli cells are found? [M.P. P.C.S. (Pre) 2021]

(a) Ovary
(b) Kidney
(c) Liver
(d) Testis

Correct Answer: (d) Testis

Solution:Sertoli cells are somatic cells found in human testes which contribute to the process of spermatogenesis (the production of sperm) as a structural component of the seminiferous tubules. They are activated by follicle-stimulating hormone (FSH) secreted by the adenohypophysis and express FSH receptor on their membranes. They are a type of sustentacular ‘nurse’ cell.