Human Reproduction

(A) Incorrect : Spermatogonia undergo mitotic differentiation.

(B) Incorrect : Primary spermatocytes undergo $1^{\text {st }}$ meiotic division to form secondary spermatocytes.

(C) Correct : Secondary spermatocytes undergo $2^{\text {nd }}$ meiotic division to form the haploid spermatids.

(D) Incorrect : Spermatids form spermatozoa through a differentiation process called spermiogenesis.

(E) Correct : Spermatids produce spermatozoa via spermiogenesis.

Thus, the correct statements are (C) and (E) only.

• By the end of second month of pregnancy ( 8 weeks), the foetus develops limbs and digits

• By the end of 12 weeks (first trimester) of pregnancy, most of the major organ system are formed. The limbs and external genital organs are also well developed.

• During the fifth month ( 20 weeks) of pregnancy, the first movements of the foetus and appearance of hair on the head are usually observed.

• By the end of about 24 weeks (ends of second trimester) of pregnancy, the body is covered with fine hair, eye lids separate and eyelashes are formed.

So, the correct match is A-II, B-III, C-IV, D-I

The cell layer/structure around the female gamete from outer to inner side is : Corona radiata → zona pellucida → perivitelline space → plasma membrane of ovum.

So the correct answer is $\mathrm{C}, \mathrm{A}, \mathrm{B}, \mathrm{D}$.

The Graafian follicle ruptures to release the secondary oocyte (ovum) from the ovary by the process called ovulation.

The secondary oocyte forms a membrane called zona pellucida surrounding it.

Endometrium is the innermost layer of uterine wall.

Chorion is the outermost extraembryonic membrane that surrounds the embryo.

The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens. The oviducts, uterus and vagina constitute the female accessory ducts.

Infundibulum is the part of oviduct.

Rapid secretion of LH leading to its maximum level during the mid-cycle called LH surge induces rupture of Graafian follicle and thereby the release of ovum (ovulation).

The remaining parts of the Graafian follicle transform as the corpus luteum, which secretes large amounts of progesterone.

Sperm travels across the fallopian tube via flagellar movement.

The placenta acts as a temporary endocrine gland during pregnancy, secreting several vital hormones essential for fetal development and maintenance of pregnancy.

Several hormones produced by placenta are human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogen, progestogens, etc.

Luteinizing hormone (LH) is secreted by anterior pituitary.

The first menstruation begins at puberty and is called menarche.

$\bullet$ Ovulation is the process that deals with the release of secondary oocyte from the mature Graafian follicle.

$\bullet$ In human beings, menstrual cycles ceases around 50 years of age; that is termed as menopause.

$\bullet$ Diapause is a state of dormancy or developmental arrest in an organism.

In a human female's pregnancy.

$\bullet$ After one month of pregnancy, the embryo's heart is formed.

$\bullet$ By the end of second month of pregnancy, the foetus develops limbs and digits.

$\bullet$ The first movements of foetus and appearance of hair on head are usually observed during the fifth month.

The head of the sperm contains an elongated nucleus that houses the genetic material.

The middle piece is rich in mitochondria, which generate the energy required for sperm movement.

The acrosome is a cap-like structure situated at the head of the sperm. It contains enzymes that play a crucial role in the fertilization of the ovum.

The tail of the sperm is responsible for facilitating sperm motility, which is essential for fertilization.

Statements A and B are true while statements C and D are false.

The first polar body is associated with the formation of the secondary oocyte LH surge leads to ovulation. Decreased levels of progesterone during late luteal phase leads to degeneration of the endometrium and onset of menstrual bleeding.

Twins who are a boy and a girl are most likely fraternal twins, also known as dizygotic twins. These twins originate from two separate fertilized eggs, and they typically develop their own amniotic sacs, placentas, and supporting structures. Unlike identical (monozygotic) twins who arise from the same fertilized egg and share identical genetic material, fraternal twins have unique genetic make-ups, similar to regular siblings. Therefore, it's more accurate to categorize boy-girl twins as fraternal.

The correct answer is option (C), because in a 28 days menstrual cycle of a human female, rapid secretion of LH leading to its maximum level during the mid-cycle (14th day) called LH surge induces the rupture of Graafian follicle and thereby the release of ovum (ovulation).

Hence, both (A) and (R) are correct and (R) is the correct explanation of (A).

To understand the correct sequence in the route of milk ejection from the human mammary gland, we need to follow the anatomical pathway that milk travels. Let's break down each part and its function in the sequence:

Mammary alveolus (C): These are the milk-producing structures in the mammary gland. Milk is initially produced here and stored in the alveolar cells.

Mammary tubule (E): The mammary alveoli are connected to small ductules called mammary tubules, which transport the milk out of the alveoli.

Mammary duct (A): The mammary tubules merge to form larger ducts known as mammary ducts. These ducts conduct the milk toward the nipple area.

Ampulla (D): The mammary ducts widen into lactiferous sinuses, known as ampullae, which act as reservoirs for the milk before it is ejected.

Lactiferous duct (B): Finally, the milk travels through the lactiferous ducts, which open at the nipple for milk ejection.

So, the correct sequence is:

$\mathrm{C} \rightarrow \mathrm{E} \rightarrow \mathrm{A} \rightarrow \mathrm{D} \rightarrow \mathrm{B}$

Thus, the correct answer is:

Option C

The correct answer is option (A) because

$\bullet$ Mons pubis is a cushion of fatty tissue covered by skin and pubic hair. So (A) matches with (II).

$\bullet$ Clitoris is a tiny finger like structure which lies at the upper junction of the two labia minora above the urethral opening. So, (B) matches with (III)

$\bullet$ Hymen is a membrane which partially covers the opening of vagina., So (C) matches with (IV)

$\bullet$ Labia majora are fleshy folds of tissue which extends down from the mons pubis and surround the vaginal opening. So, (D) matches with (I)

Other options (B), (C) and (D) are incorrect as they represent mismatches for (A), (B), (C) and (D)

The correct answer is option (A) as

$\bullet$ Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully developed foetus and the placenta that induce mild uterine contractions called foetal ejection reflex.

$\bullet$ Placenta acts as an endocrine tissue and produces several hormones like hCG, hPL estrogens, progestogens, etc.

$\bullet$ The milk produced during the initial few days of lactation is called colostrum that contains several antibodies absolutely necessary to develop resistance for the new-born babies.

Fimbriae helps in collection of the ovum after ovulation.

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:

• Infundibulum: This is the funnel-shaped end of the Fallopian tube nearest the ovary. Its edges are fringed with structures known as fimbriae, which help in capturing the egg released from the ovary.


• Ampulla: Representing the longest portion of the Fallopian tube, the ampulla forms about half of its length. It is typically where fertilization occurs when a sperm meets an egg.


• Isthmus: This is the narrower region of the tube that connects to the uterus.

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. (1) 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.

Statement I is incorrect because the primary follicles, when surrounded by more layers of granulosa cells and a theca, are called secondary follicles. However, the secondary follicles then transform into tertiary follicles, which is characterized by a fluid-filled cavity called antrum. Therefore, the statement is not accurate as it incorrectly describes the transition from primary to secondary follicle.

Statement II is correct as the Graafian follicle does rupture to release the secondary oocyte from the ovary, a process known as ovulation.

So, the correct answer is Option B : Statement I is incorrect but Statement II is true.

The correct statements regarding the female reproductive cycle are :

A. In non-primate mammals cyclical changes during reproduction are called the oestrus cycle.

C. Lack of menstruation may be indicative of pregnancy.

D. Cyclic menstruation extends between menarche and menopause.

Statement B is incorrect because the first menstrual cycle that begins at puberty is called menarche, not menopause. Menopause is the end of the menstrual cycle and fertility in women, typically occurring in middle to old age.

So, the correct option is :

Option C : A, C and D only

Option (d) is the correct answer because one primary spermatocyte produces two secondary spermatocytes by meiosis I and one secondary spermatocyte produces two spermatozoa via meiosis 2. So, 200 million secondary spermatocytes will produce 400 million spermatozoa.

Option (d) is the correct answer because the components of mammary gland (from proximal to distal) is:

(c) $\to$ (e) $\to$ (a) $\to$ (d) $\to$ (b)

$\mathrm{Alveoli} \to \mathop {\mathrm{Mammary}}\limits_{\mathrm{tubules}} \to \mathop {\mathrm{Mammary}}\limits_{\mathrm{duct}} \to \mathop {\mathrm{Mammary}}\limits_{\mathrm{ampulla}} \to \mathop {\mathrm{Lactiferous}}\limits_{\mathrm{duct}} $

Each mammary lobule is composed of a number of alveoli which open into mammary tubules. The tubules of each lobule join to form a mammary duct. Near the nipple, mammary ducts expand to form mammary ampullae where some milk is stored before going to lactiferous duct which is present at distal end through which milk is sucked out.

Option (b) is the correct answer because thyroxine is the main hormone that increases the basal metabolic rate in our body. A high metabolic rate is required during pregnancy, so levels of thyroxine increase in pregnant females along with other hormones such as cortisol, progesterone, etc.

Option (d) is the correct answer.

$\bullet$ In both, spermatogenesis and oogenesis haploid gametes are formed. So (a) is true for both.

$\bullet$ The spermatids are transformed into spermatozoa (sperms) by the process called spermiogenesis. Hence, (b) is true for spermatogenesis only.

$\bullet$ Spermatogenesis and oogenesis both are controlled by LH and FSH secreted by the anterior pituitary. Hence, (d) is true for both.

$\bullet$ 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.

Option (c) is the correct answer because Statement II is incorrect as the transformation of spermatids into spermatozoa (sperms) are called spermiogenesis. After this, sperm head becomes embedded in the Sertoli cells and are finally released from the seminiferous tubules by the process called spermiation. Hence, Statement I is a correct statement. Spermatogenesis is the process of formation of sperms from spermatogonia.

Option (2) is the correct answer as oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells (oogonia) are formed within each foetal ovary.

No more oogonia are formed and added after birth in a human female.

At puberty only 60,000 to 80,000 primary follicles are left in each ovary, rest degenerate during the phase from birth to puberty.