31 Years NEET Previous Year Questions: Human Reproduction - 1 - NEET MCQ

The Fallopian tubes, also known as oviducts or uterine tubes, are structures in the female reproductive system that stretch from the uterus to the ovaries. These tubes play a crucial role in the journey of the egg from the ovary to the uterus. The primary components of the Fallopian tubes include the infundibulum, ampulla, and isthmus:
When examining the options provided, Option A mentions the "Uterine fundus". The fundus is actually the top part of the uterus, situated above the openings of the Fallopian tubes into the uterine cavity. The fundus of the uterus is not a part of the Fallopian tubes; instead, it is a region of the uterus itself. Therefore, the correct answer is: Option A: Uterine fundus

To answer this question correctly, we need to evaluate the facts around each statement individually before making a comparison:

• Statement I: The presence or absence of hymen is not a reliable indicator of virginity. This statement is true. The hymen is a thin, elastic membrane located at the entrance to the vagina. Contrary to common belief, the hymen is not an impermeable barrier that is always torn when virginity is lost via sexual intercourse. It can vary greatly in shape and size from person to person. Some girls are born without a hymen, some have small hymenal tissue, and others have hymens that are very elastic. Moreover, the hymen can be stretched or torn during a variety of non-sexual activities such as tampon use, physical exercise (e.g., biking, gymnastics), or medical examinations. Therefore, the state of the hymen is not a definite indicator of virginity, making statement I true.
• Statement II: The hymen is torn during the first coitus only. This statement is false. As previously mentioned, the hymen can be stretched or torn by activities that are not sexual in nature. Additionally, many women may not experience tearing of the hymen at all during their first sexual intercourse. In cases where the hymen is more elastic or resilient, it may not tear during sexual activity. Furthermore, there are practices and surgeries, such as hymenoplasty, that can restore or create a hymen-like structure, indicating that the hymen can be altered multiple times throughout a woman's life. Thus, the claim that the hymen is torn only during the first coitus is incorrect.

Based on the explanations provided:
Option C (Statement I is true but Statement II is false) is the correct answer.

The correct answer is option no. (A) as

(A) is FSH which is a pituitary hormone.
(B) is Leydig cells which are found in the interstitial space outside of the seminiferous tubules.
(C) is Sertoli cells are found inside the seminiferous tubules.
(D) is Spermiogenesis which is a process that helps in transformation of spermatids into spermatozoa.

Option (a) is the correct answer to this question because statement I and statement II both are correct. Vas deferens receives a duct from seminal vesicle and opens into urethra as the ejaculatory duct. The cavity of cervix is called cervical canal which along with vagina forms the birth canal.

The correct answer is option (d) as first menstrual cycle that begins at puberty is called menarche.
Cyclic menstruation is an indicator of normal reproductive phase and extends between menarche and menopause.
In primates, cyclical changes during reproduction are called menstrual cycle.

Option (b) is the correct answer because both Assertion and Reason are true.
Implantation is embedding of the blastocyst into endometrium of uterus.
Correct explanation of reason is Corpus luteum secretes large amount of progesterone which is essential for maintenance of endometrium of uterus. In absence of fertilisation, the corpus luteum degenerates hence the decrease in the level of progesterone hormone will cause disintegration of endometrium leading to menstruation.

• The process of spermatogenesis occurs in testis, in which the immature male germ cells or spermatogonia are converted to sperms. 
• The spermatogonia present on the inside wall of seminiferous tubules undergoes mitosis. 
• Some spermatogonia periodically undergo meiosis. These spermatogonia are called as primary spermatocytes (2n). 
• A primary spermatocyte completes the first meiotic division and forms secondary spermatocytes (n). 
• The secondary spermatocytes undergo the second meiotic division to produce spermatids.
• The spermatids are then, transformed into spermatozoa or sperms by the process called spermiogenesis. 
• After spermiogenesis, sperm heads become embedded in the Sertoli cells. These spermatozoa are finally released from the seminiferous tubules by the process called spermiation.

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Oogenesis starts at embryonic development stage in females. 

• In both, spermatogenesis and oogenesis haploid gametes are formed. So (a) is true for both.
• The spermatids are transformed into spermatozoa (sperms) by the process called spermiogenesis. Hence, (b) is true for spermatogenesis only.
• Spermatogenesis and oogenesis both are controlled by LH and FSH secreted by the anterior pituitary. Hence, (d) is true for both.
• Spermatogenesis is a continuous process that begins at puberty. So (e) is true for spermatogenesis. Oogenesis on the other hand begins during embryonic development of the female.

Sperm plasma membrane receptors bind to ZP3 on the zona pellucida. Binding to ZP3 allows sperm to adhere to the zona pellucida, which is an important step in fertilisation.

The secretions of the acrosome help the sperm enter into the cytoplasm of the ovum through the zona pellucida and the plasma membrane.

Fig: Sperm binding receptors

Relaxin is produced first by the corpus luteum of the ovary and later by the placenta. It helps in parturition as it increases the flexibility of the pubic symphysis and helps dilate the uterine cervix.

LH (Luteinizing hormone) is produced by the pituitary gland in the brain. It triggers ovulation & promotes the development of the corpus luteum by rupture of the Graafian follicle and high concentration of estrogen is released by mature Graafian  follicle. The egg ruptures the ovary wall and heads into the fallopian tubes where it waits for the sperm.

In follicular phase of menstrual cycle, LH and FSH increase gradually and stimulate follicular development as well as secretion of estrogens by the growing follicles.

• The motile sperms swim rapidly, pass through the cervix, enter into the uterus and finally reach the junction of the isthmus and ampulla (ampullary-isthmic junction) of the fallopian tube.
• The ovum released by the ovary is also transported to the ampullary isthmic junction where fertilization lakes place.
• Fertilization can only occur if the ovum and sperms are transported simultaneously to the ampullaryisthmic junction. This is the reason why not all copulations lead to fertilization and pregnancy.

• Prolactin is the hormone which induces lactation (enables females to produce milk) and has no role in parturition.
• Parturition is a phenomenon of giving birth. It is a process of delivering a child from the womb to the outside. It is usually initiated by the release of oxytocin hormone. 
• This hormone increases the contraction of uterine muscles. Prostaglandins are synthesized and released in response to the oxytocin hormone. Also, an increase in estrogen and progesterone ratio indicates the initiation of the parturition process.

During gametogenesis, spermatogonia are diploid because of undergoing the process of meiosis.

Spermatogenesis:

Urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids from the body. The urethra travels through the penis and carries semen as well as urine.

The corpus luteum is a temporary endocrine structure in female mammals that is involved in the production of relatively high levels of progesterone.

Corpus Luteum:

Synthesis of estrogen and progesterone due to high level of hCG is a normal gonadotropic activity in a normal pregnant female. 

• Human chorionic gonadotropin is the embryonic hormone, which ensures the corpus luteum continues to produce progesterone throughout the first trimester of pregnancy.  
• As well as maintaining progesterone production from the ovary, human chorionic gonadotropin may also play a role in making sure the lining of the uterus (endometrium) is ready to receive the implanting embryo. hCG may also promote the production of other steroids (e.g., estrogen) and protein (e.g., relaxin, inhibin A) hormones whose actions in the uterus may facilitate gestation.
• So, the correct answer is 'High level of hCG stimulates the synthesis of estrogen and progesterone.'