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Reproductive System Q-Bank
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Contraceptive oral pills used by females help in birth control by:
Oral contraceptive pills (OCPs) are one of the most effective hormonal methods of contraception. According to NCERT Biology, they contain: Progestins (synthetic progesterone) alone, or A combination of estrogen and progestin. Mechanism of Action The hormones in oral pills exert negative feedback on the hypothalamus and anterior pituitary. This leads to: Decreased secretion of FSH, preventing follicular maturation. Suppression of the LH surge, preventing ovulation. Since no ovulation occurs, no ovum is available for fertilization. Additional Actions Oral contraceptive pills also: Thicken the cervical mucus, making sperm penetration difficult. Make the endometrium less suitable for implantation. Alter tubal motility. However, the primary mechanism is prevention of ovulation.
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Labium majora of a female mammal is homologous to:
The labia majora are the outer folds of the female external genitalia (vulva). They protect the more delicate structures of the vulva, such as the labia minora, clitoris, urethral opening, and vaginal opening. Embryologically, the labia majora and the scrotum develop from the same embryonic structure, known as the labioscrotal swellings. In males, under the influence of testosterone, the labioscrotal swellings fuse to form the scrotum. In females, due to the absence of high androgen levels, they remain separate and develop into the labia majora. Because they share the same embryological origin, they are homologous structures.
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The number of days the menstrual phase of menstrual cycle lasts about:
The menstrual cycle is a series of cyclic changes that occur in the ovaries and uterus of females of reproductive age. A normal menstrual cycle lasts about 28 days (range: 21–35 days). The cycle is divided into four phases: Menstrual phase Follicular (Proliferative) phase Ovulatory phase Luteal (Secretory) phase The menstrual phase is the first phase of the menstrual cycle. During this phase: The functional layer of the endometrium is shed. Blood, mucus, and endometrial tissue are discharged through the vagina as menstrual flow. This occurs because the corpus luteum degenerates, causing a fall in oestrogen and progesterone levels. In a normal cycle, the menstrual phase lasts about 3–5 days. Remember the approximate duration of each phase in a 28-day cycle: Menstrual phase: 3–5 days Follicular (Proliferative) phase: Day 5–13 Ovulation: Around Day 14 Luteal (Secretory) phase: Day 15–28
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The cytoplasm surrounding the mitochondria found in the middle piece of the sperm is called:
During spermiogenesis (the transformation of spermatids into mature spermatozoa), the sperm undergoes extensive structural remodeling. The middle piece of the sperm contains: Numerous mitochondria arranged helically around the axial filament (axoneme). A thin layer of cytoplasm associated with these mitochondria. This cytoplasmic sheath is referred to as the manchette in many classical zoology and embryology texts used for entrance examinations. The manchette is a transient microtubular cytoplasmic structure that assists in shaping the sperm head and organizing the middle piece during spermiogenesis.
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Progesterone production fails during
Progesterone is one of the principal female sex hormones. It is secreted mainly by: Corpus luteum of the ovary after ovulation. Placenta during pregnancy. Its major functions are: Preparing the endometrium for implantation. Maintaining pregnancy. Reducing uterine contractions. Promoting the secretory phase of the menstrual cycle. For progesterone to be produced, ovulation must occur, because the corpus luteum is formed only after ovulation. Why Does Progesterone Production Fail During Menopause? Menopause is the permanent cessation of menstruation due to depletion of ovarian follicles. During menopause: Ovarian follicles are exhausted. Ovulation no longer occurs. The corpus luteum is not formed. Consequently, progesterone secretion almost completely ceases. Estrogen production also decreases significantly. Thus, progesterone production fails permanently during menopause. Memory Trick "No Ovulation → No Corpus Luteum → No Progesterone." Simply: Pregnancy → Progesterone High Menopause → Progesterone Absent
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In vitro fertilisation is a technique that involves transfer of which one of the following into the Fallopian tube?
In Vitro Fertilization (IVF) is an Assisted Reproductive Technology (ART) in which fertilization occurs outside the body under laboratory conditions. After fertilization: The zygote begins cleavage. It develops into a 2-cell, 4-cell, and then 8-cell embryo. According to NCERT Biology: Zygote or early embryo (up to 8 blastomeres) is transferred into the fallopian tube. This procedure is called ZIFT (Zygote Intrafallopian Transfer). Embryos with more than 8 blastomeres are transferred into the uterus. This procedure is called IUT (Intrauterine Transfer). Therefore, the fallopian tube receives either the zygote or an embryo up to the 8-cell stage. Remember: ZIFT → Zygote/≤8-cell embryo → Fallopian tube IUT → >8-cell embryo → Uterus Revision Points IVF = Fertilization outside the body. ZIFT → Zygote or embryo up to 8 cells. IUT → Embryo with more than 8 blastomeres. Fertilization occurs in the laboratory. Memory Trick "8 Goes to Tube, More Goes to Uterus."
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Most important component of oral contraceptive is:
Oral contraceptive pills (OCPs) are hormonal contraceptives used to prevent pregnancy. According to NCERT Biology, they contain: Progestins (synthetic progesterone) alone, or A combination of estrogen and progestin. The most important component is progestin (progesterone analogue) because it is primarily responsible for preventing ovulation. Mechanism of Action Progesterone exerts negative feedback on the hypothalamus and anterior pituitary. This results in: Decreased FSH secretion → prevents follicular maturation. Suppression of the LH surge → prevents ovulation. Additional actions include: Thickening of cervical mucus, making sperm penetration difficult. Making the endometrium less suitable for implantation. Thus, progesterone is the principal component of oral contraceptive pills.
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The immediate cause of induction of ovulation in female is the large plasma surge of:
Ovulation is the release of a secondary oocyte from the mature Graafian follicle. In a normal 28-day menstrual cycle, it occurs around the 14th day. The immediate trigger for ovulation is the mid-cycle surge of Luteinizing Hormone (LH) secreted by the anterior pituitary gland. Hormonal Mechanism of Ovulation Hypothalamus Secretes Gonadotropin-Releasing Hormone (GnRH). Anterior Pituitary GnRH stimulates the secretion of: Follicle-Stimulating Hormone (FSH) Luteinizing Hormone (LH) Developing Graafian Follicle FSH stimulates follicular growth. The growing follicle secretes increasing amounts of estradiol (estrogen). Positive Feedback of Estrogen High estradiol levels stimulate the hypothalamus and anterior pituitary. This causes a sudden LH surge. LH Surge The LH surge: Causes rupture of the mature Graafian follicle. Releases the secondary oocyte (ovulation). Initiates formation of the corpus luteum. Thus, the immediate cause of ovulation is the LH surge. Remember the sequence: FSH → Follicle growth Estradiol → Positive feedback LH surge → Ovulation Progesterone → Secretory phase Common Mistake Students often confuse estradiol with LH. Remember: Estradiol causes the LH surge. LH surge causes ovulation. Thus: Indirect cause → Estradiol Immediate cause → LH simply: "LH = Launch Hormone."
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Vaginal orifice and urethral orifice open into:
The vulva is the external female genitalia. It includes: Mons pubis Labia majora Labia minora Clitoris Vestibule of the vagina Openings of the urethra, vagina, and Bartholin's glands Both the external urethral orifice and the vaginal orifice open into the vestibule, which is part of the vulva.
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How many secondary spermatocytes are required to form 400 spermatozoa?
Spermatogenesis is the process of producing mature spermatozoa from germ cells in the seminiferous tubules of the testes. Stepwise Process The developmental sequence is: Spermatogonium (2n) ⬇️ Mitosis Primary spermatocyte (2n) ⬇️ Meiosis I 2 Secondary spermatocytes (n) ⬇️ Meiosis II 4 Spermatids (n) ⬇️ Spermiogenesis 4 Spermatozoa (n) Relationship Between Secondary Spermatocytes and Spermatozoa Each secondary spermatocyte undergoes Meiosis II and produces: 2 spermatids Each spermatid differentiates into 1 spermatozoon Therefore, 1 Secondary spermatocyte → 2 Spermatozoa
Calculation Given: 400 spermatozoa are to be formed. Since, 1 secondary spermatocyte = 2 spermatozoa Therefore, Required secondary spermatocytes = 200
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Sperm capacitation involves:
Capacitation is the final functional maturation of sperm that occurs in the female genital tract. During capacitation: Cholesterol and glycoproteins are removed from the sperm membrane. Membrane fluidity increases. Calcium influx increases. Sperm becomes hyperactive. Sperm acquires the ability to undergo the acrosomal reaction. This enables penetration of the zona pellucida. Capacitation occurs in the female genital tract. Increases membrane fluidity. Enables the acrosomal reaction. Required for fertilization.
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During oogenesis in mammals, the second meiotic division occurs:
Oogenesis is the process of formation of the female gamete (ovum) in the ovary. It involves two meiotic divisions, but unlike spermatogenesis, the second meiotic division is completed only after fertilization. Sequence of Oogenesis Oogonium (2n) Divides by mitosis during fetal life to form primary oocytes. Primary oocyte (2n) Enters Meiosis I during fetal life. Remains arrested in Prophase I (dictyotene stage) until puberty. Completion of Meiosis I Just before ovulation, the primary oocyte completes Meiosis I. It forms: One secondary oocyte (n) One first polar body (n) Secondary oocyte (n) Immediately begins Meiosis II. Becomes arrested at Metaphase II. This is the stage at which the secondary oocyte is ovulated. Fertilization When a sperm penetrates the secondary oocyte, it triggers the completion of Meiosis II. The secondary oocyte then forms: One mature ovum (n) One second polar body (n) Therefore, in mammals, the second meiotic division is completed only after fertilization. Actually: Ovulation releases a secondary oocyte, not a mature ovum. The mature ovum is formed only after fertilization, when Meiosis II is completed. Memory Trick "First before Ovulation, Second after Sperm." Meiosis I → Before ovulation Meiosis II → After fertilization Or simply: "No sperm = No completion of Meiosis II."
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Which of the following represents a condition where the motility of the sperms is highly reduced?
Asthenospermia (Asthenozoospermia) is a condition in which sperm motility is reduced. Since sperm must actively swim through the female reproductive tract to reach and fertilize the ovum, reduced motility significantly decreases male fertility. Normal sperm motility depends on: Adequate ATP production by the mitochondria in the middle piece. A normally functioning tail (flagellum). Healthy seminal fluid and normal sperm structure. If sperm motility is markedly reduced, the sperm may fail to reach the ovum, leading to subfertility or infertility. Therefore, Asthenospermia is the condition characterized by reduced sperm motility. Azoospermia → Zero sperm Oligospermia → Only a few sperm Asthenospermia → Slow-moving sperm
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The starting of menstruation in girls is:
Menarche is the first menstrual bleeding in a girl's life. It marks the beginning of the menstrual (reproductive) phaseand indicates that the ovaries have started functioning under the influence of reproductive hormones. Menarche usually occurs between 10–16 years of age, with an average age of about 12–13 years (this may vary with genetics, nutrition, and environmental factors). After menarche: The hypothalamic–pituitary–ovarian (HPO) axis becomes functional. The ovaries begin cyclical secretion of oestrogen and progesterone. Menstrual cycles begin, although the first few cycles may be anovulatory because the hormonal axis is still maturing. Thus, menarche marks the onset of menstruation and the beginning of the reproductive life of a female. Remember: Puberty is the entire developmental phase. Menarche is a single event—the first menstrual period. Remember: Menarche → First menstruation Menopause → Menstruation stops
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The head of epididymis is called:
The epididymis is a long, highly coiled duct attached to the posterior surface of each testis. It serves as the site of sperm maturation, storage, and transport before sperm enter the vas deferens. The epididymis is divided into three anatomical parts: Caput epididymis (Head) Corpus epididymis (Body) Cauda epididymis (Tail) The head (caput epididymis) is the enlarged upper portion that lies on the superior pole of the testis. It receives immature sperm from the efferent ductules, which connect the testis to the epididymis. During their passage through the epididymis (approximately 12–20 days), sperm undergo: Functional maturation Acquisition of progressive motility Ability to fertilize an ovum Thus, the head of the epididymis is called the caput epididymis.
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Erection of penis in mammals is an example of:
An erection of the penis occurs when the erectile tissues (corpora cavernosa and corpus spongiosum) become engorged with blood. This increased blood volume makes the penis rigid enough for sexual intercourse. The rigidity is produced by hydraulic (fluid) pressure, not by bones or cartilage. Therefore, it is considered an example of a hydrostatic skeleton. Mechanism of Penile Erection Sexual stimulation activates the parasympathetic nervous system. Nitric oxide (NO) is released from nerve endings and endothelial cells. NO increases cyclic GMP (cGMP), causing relaxation of smooth muscles in the penile arteries and erectile tissue. Increased arterial blood flow fills the corpora cavernosa and corpus spongiosum. Compression of venous outflow traps blood within the erectile tissue. The penis becomes enlarged and rigid (erection). Thus, the erection depends on blood pressure within erectile tissues, which is a hydrostatic mechanism.
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The testes in humans are situated outside the abdominal cavity inside a pouch called scrotum. The purpose served is for:
The testes are the primary male reproductive organs (gonads). Unlike most organs, they are located outside the abdominal cavity in a skin-covered sac called the scrotum. This unique location is essential for normal sperm production (spermatogenesis). Why Are the Testes Located in the Scrotum? The primary purpose is to maintain the testes at a temperature 2–3°C below the core body temperature. Normal body temperature: approximately 37°C Optimal testicular temperature: approximately 34–35°C This lower temperature is necessary because the enzymes involved in spermatogenesis function optimally at a slightly cooler temperature. Higher temperatures impair sperm production and reduce fertility. Importance of Lower Testicular Temperature A temperature 2–3°C below body temperature is required for: Normal spermatogenesis. Proper maturation of germ cells. Normal sperm count. Good sperm motility and fertility.
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Vasa efferentia are the ductules leading from:
The pathway of sperm is: Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra The vasa efferentia are small ductules that transport sperm from the rete testis to the head of the epididymis. Short Revision Points Sperm pathway: Seminiferous tubules Rete testis Vasa efferentia Epididymis Vas deferens Urethra
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Tubectomy, a method of population control, is performed on:
Tubectomy (tubal ligation) is a permanent female sterilization method. During the procedure: Both fallopian tubes are cut and tied. This prevents sperm from reaching the ovum. Ovulation continues normally, but fertilization cannot occur. The corresponding male sterilization procedure is vasectomy.
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Capacitation refers to changes in the:
Capacitation is the physiological maturation of sperm within the female reproductive tract before fertilization. During capacitation: Membrane cholesterol and glycoproteins are removed. Sperm motility increases. The sperm becomes capable of undergoing the acrosomal reaction. Revision Points Occurs in female genital tract. Prepares sperm for fertilization. Required for acrosomal reaction. Memory Trick: "Capacitation = Capability to Fertilize."
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