Human Reproduction MCQ Class 12

D. All of the above. Reproduction ensures species survival, introduces genetic variation through mechanisms like sexual reproduction, and provides the raw material for evolutionary changes.

D. Regenerative reproduction. While regeneration (regrowing body parts) is a biological process, it’s generally not considered a primary mode of reproduction like sexual or asexual methods. Viviparity refers to live birth, a characteristic of reproduction, not a type itself.

B. They give birth to live young. Viviparity means the embryo develops inside the mother’s body, receiving nourishment directly from her, leading to the birth of live offspring.

C. It increases genetic variation, improving adaptability. Combining genetic material from two parents creates offspring with unique gene combinations, enhancing the species’ ability to adapt to changing environments.

A. Budding in yeast. Budding is a type of asexual reproduction where a new organism develops from an outgrowth or bud due to cell division at one particular site.

C. Pelvic cavity. The main organs of the male reproductive system, including the testes (within the scrotum extending below), accessory glands, and parts of the duct system, are primarily located in the pelvic region.

C. Testes, accessory ducts, glands, and external genitalia. This includes the testes (sperm/hormone production), ducts (sperm transport/storage), glands (semen fluid production), and external genitalia (penis and scrotum for delivery and temperature regulation).

B. Produce sperms and hormones. The testes have two primary functions: spermatogenesis (sperm production) in the seminiferous tubules and production of androgens (like testosterone) by Leydig cells.

C. To maintain a lower temperature for sperm production. Spermatogenesis requires a temperature about 2-2.5°C lower than the core body temperature, which the scrotum helps maintain.

C. 2-2.5°C lower than the normal body temperature. This slightly cooler environment is essential for the proper development and viability of sperm.

A. Testicular lobules. Each testis is divided by connective tissue septa into approximately 250 testicular lobules.

B. Seminiferous tubules. These highly coiled tubules are located within the testicular lobules and are the specific site of spermatogenesis.

C. The process of sperm production. It’s the complex process involving meiosis and differentiation where spermatogonia develop into mature spermatozoa.

B. Sertoli cells. Also known as nurse cells, Sertoli cells support, nourish, and regulate the development of sperm cells within the seminiferous tubules.

A. Leydig cells. Located in the interstitial spaces between seminiferous tubules, Leydig cells produce and secrete androgens, primarily testosterone, under the influence of LH.

C. A type of male hormone. Androgens are the group of male sex hormones, with testosterone being the most important, responsible for male characteristics and reproductive functions.

D. Bulbourethral gland. The bulbourethral glands (Cowper’s glands) are accessory glands that produce pre-ejaculate fluid, not ducts for sperm transport.

B. Store and transport sperms. The accessory ducts (rete testis, vasa efferentia, epididymis, vas deferens, ejaculatory duct, urethra) form the pathway for sperm to travel from the testes out of the body and also serve as sites for sperm maturation and storage (especially the epididymis).

C. Vas deferens. The vas deferens (or ductus deferens) transports mature sperm from the epididymis towards the urethra, joining with the duct of the seminal vesicle to form the ejaculatory duct.

C. Transport both urine and semen. The urethra serves as the terminal duct for both the urinary system (transporting urine from the bladder) and the reproductive system (transporting semen during ejaculation).

C. Facilitate insemination. The penis is the external male copulatory organ, adapted for delivering sperm into the female reproductive tract during intercourse.

D. Vas deferens. The vas deferens is an accessory duct responsible for sperm transport, not a gland producing seminal fluid.

B. Secrete seminal plasma. The seminal vesicles, prostate gland, and bulbourethral glands produce seminal plasma, the fluid component of semen that nourishes, protects, and aids the transport of sperm.

B. Fructose, calcium, and enzymes. Seminal plasma is rich in fructose (energy source for sperm), calcium, various enzymes (like PSA, clotting factors, fibrinolysin), and buffers.

A. Lubricate the penis. Secretions from the bulbourethral (Cowper’s) glands are released prior to ejaculation to lubricate the distal urethra and neutralize any acidic urine residue.

A. Provide energy for sperm motility. Fructose, primarily secreted by the seminal vesicles, serves as the main metabolic fuel for spermatozoa, powering their flagellar movement.

A. Seminal vesicles. The seminal vesicles contribute the largest volume (about 60-70%) to the seminal fluid, providing fructose and prostaglandins.

B. Secrete a milky fluid that enhances sperm motility. The prostatic fluid is slightly acidic and contains citrate (nutrient), enzymes (like PSA for liquefaction), and seminalplasmin (antibiotic), contributing to sperm activation and viability.

C. Alkaline. Semen is typically alkaline, with a pH ranging from 7.2 to 8.0.

A. To protect sperm from the acidic environment of the vagina. The alkalinity helps neutralize the natural acidity of the male urethra and the female vagina, creating a more favorable environment for sperm survival and motility.

D. Both B and C. Seminal plasma contains clotting factors (from seminal vesicles) that cause initial coagulation, and enzymes like prostate-specific antigen (PSA) (from the prostate) that later liquefy the coagulum, releasing the sperm.

B. To regulate the temperature of the testes. The cremaster muscle raises or lowers the testes in response to temperature changes and sexual stimulation to maintain optimal temperature for spermatogenesis.

B. It contracts, bringing the testes closer to the body. Contraction of the cremaster and dartos muscles pulls the testes closer to the pelvic cavity to conserve heat.

B. To regulate the temperature of the testes. The dartos muscle is smooth muscle within the scrotal wall that wrinkles the scrotal skin, reducing surface area and heat loss in cold conditions.

B. To provide structural support to the testes. The tunica albuginea is a tough, fibrous outer capsule that covers the testis and extends inward to form septa, dividing the testis into lobules.

B. To transport sperm from the seminiferous tubules to the efferent ductules. The rete testis is a network of tubules within the mediastinum testis that receives sperm from the seminiferous tubules and passes them on to the vasa efferentia.

C. Pelvic cavity. The ovaries, fallopian tubes, uterus, cervix, and vagina are primarily situated within the pelvic cavity.

C. Ovaries, oviducts, uterus, cervix, vagina, and external genitalia. This encompasses the organs responsible for egg production (ovaries), transport (oviducts), gestation (uterus), intercourse (vagina, cervix), and external structures (vulva).

A. Produce eggs and hormones. The ovaries are responsible for oogenesis (producing ova or eggs) and secreting the primary female sex hormones, estrogen and progesterone.

A. Estrogen and progesterone. These steroid hormones produced by the ovaries regulate the menstrual cycle, support pregnancy, and influence secondary sexual characteristics. FSH and LH are pituitary hormones that regulate the ovaries.

D. All of the above. Estrogen promotes the growth of reproductive organs, development of secondary sexual characteristics (like breast development, fat distribution), stimulates endometrial proliferation, and plays a role in regulating the menstrual cycle.

B. To prepare the uterus for pregnancy and maintain it during pregnancy. Progesterone, primarily secreted by the corpus luteum and later the placenta, makes the endometrium secretory (ready for implantation), maintains the uterine lining during pregnancy, and inhibits uterine contractions.

B. Fallopian tubes. Oviducts and Fallopian tubes are synonymous terms for the tubes connecting the ovaries to the uterus.

B. To transport eggs from the ovaries to the uterus. The fallopian tubes capture the ovulated egg using fimbriae and transport it via peristalsis and ciliary action towards the uterus; they are also the usual site of fertilization.

B. Oviduct (Fallopian tube). Fertilization, the fusion of sperm and egg, most commonly takes place in the ampulla, the widest section of the fallopian tube.

C. To support the developing fetus during pregnancy. The uterus (womb) is where the fertilized egg implants and develops throughout gestation, providing nourishment and protection.

A. Perimetrium, myometrium, and endometrium. From outside to inside: the perimetrium (outer serous layer), the myometrium (thick middle layer of smooth muscle), and the endometrium (inner mucosal lining that changes with the menstrual cycle).

C. Endometrium. The endometrium proliferates (grows thicker) under estrogen influence and becomes secretory under progesterone influence, preparing for implantation. If implantation doesn’t occur, most of the endometrium is shed during menstruation.

B. To connect the uterus to the vagina. The cervix is the lower, narrow, muscular part of the uterus that opens into the vagina, controlling passage between the two.

B. To receive sperm during intercourse and serve as the birth canal. The vagina is the muscular tube extending from the cervix to the outside, serving as the receptacle for the penis during coitus and the passageway for childbirth and menstrual flow.

D. Cervix. The cervix is an internal structure, part of the uterus. The female external genitalia (collectively called the vulva or pudendum) includes the mons pubis, labia majora, labia minora, hymen, and clitoris.

B. To cover the vaginal opening. The hymen is a thin membrane that partially covers the external vaginal orifice; its presence or absence is variable and not a reliable indicator of virginity.

B. To provide sexual pleasure. The clitoris is a small, highly sensitive erectile tissue located at the anterior junction of the labia minora, homologous to the male penis, and is a primary site of female sexual sensation.

B. To produce milk for the newborn. Mammary glands are specialized accessory reproductive glands present in both sexes but functional primarily in females post-partum for lactation (milk production and secretion).

A. The process of milk production. Lactation encompasses the synthesis, secretion, and ejection of milk from the mammary glands, stimulated primarily by the hormone prolactin and triggered by infant suckling.

C. The process of gamete (sperm and ovum) formation. Gametogenesis refers to the biological process by which diploid precursor cells undergo meiosis and differentiation to form mature haploid gametes (sperm in males, ova in females).

A. Spermatogenesis. This is the specific term for the production of sperm within the seminiferous tubules of the testes.

B. Testes. Specifically, sperm production occurs within the seminiferous tubules located inside the testes.

B. Oogenesis. This is the specific term for the production and development of an ovum (egg cell) within the ovary.

A. Ovaries. The development of egg cells takes place within follicles inside the ovaries.

D. All of the above. Spermatogenesis results in four equal-sized, motile sperm; it’s continuous from puberty onwards. Oogenesis yields one large, non-motile ovum and smaller polar bodies; it’s cyclical and has a finite duration ending at menopause.

B. Ovum (egg). Oogenesis results in the formation of a mature haploid female gamete, the ovum, ready for fertilization.

A. The beginning of menstruation. Menarche marks the first occurrence of menstruation in a female, typically during puberty.

B. The end of menstruation. Menopause is the natural cessation of menstrual cycles in females, usually occurring between the ages of 45 and 55, marking the end of reproductive capability.

A. Menstrual, follicular, ovulatory, and luteal. These phases describe the cyclical events: Menstrual phase (bleeding), Follicular phase (follicle growth), Ovulatory phase (egg release), and Luteal phase (corpus luteum activity). Note: Option B describes the uterine cycle phases (Proliferative, Secretory) plus ischemic phase leading to menstruation. Option A is more commonly used for the overall ovarian/hormonal cycle.

C. Follicle-stimulating hormone (FSH). FSH, released from the anterior pituitary, stimulates the growth and maturation of ovarian follicles during the follicular phase of the menstrual cycle.

D. Luteinizing hormone (LH). A surge in LH levels, typically around day 14 of the cycle, triggers the final maturation of the dominant follicle and induces ovulation (release of the egg).

A. The release of an egg from the ovary. Ovulation is the event where a mature ovarian follicle ruptures and releases the secondary oocyte (egg) into the fallopian tube.

B. The structure formed from the ruptured follicle after ovulation. After releasing the egg, the remaining follicular cells transform into the corpus luteum, a temporary endocrine gland.

D. Both B and C. The corpus luteum secretes large amounts of progesterone and some estrogen. Progesterone prepares the uterus for potential pregnancy and maintains it if implantation occurs. If no pregnancy, it degenerates.

C. The deposition of sperm into the female reproductive tract. Insemination typically occurs during sexual intercourse when semen is ejaculated into the vagina.

B. Oviduct (Fallopian tube). Fertilization, the fusion of sperm and egg, normally occurs in the ampulla of the fallopian tube.

C. Zygote. The fusion of the haploid sperm nucleus and the haploid egg nucleus results in the formation of a single diploid cell called the zygote, the first cell of the new individual.

B. By the father’s chromosomes. The mother always contributes an X chromosome (from the egg). The father contributes either an X or a Y chromosome (from the sperm). An XX combination results in a female, while an XY combination results in a male.

C. The rapid cell division of the zygote. Cleavage refers to the series of rapid mitotic cell divisions that the zygote undergoes as it travels down the fallopian tube, increasing cell number without significant overall growth.

B. A hollow ball of cells formed from the zygote. After several rounds of cleavage, the developing structure becomes a blastocyst, characterized by an inner cell mass (which forms the embryo) and an outer layer called the trophoblast (which contributes to the placenta), surrounding a fluid-filled cavity (blastocoel).

B. The attachment of the blastocyst to the uterine wall. Implantation is the process where the blastocyst embeds itself into the endometrium (the lining of the uterus), establishing pregnancy.

C. The organ that connects the developing fetus to the uterine wall. The placenta is a temporary organ formed from both fetal (trophoblast) and maternal (endometrial) tissues, facilitating exchange between mother and fetus.

D. All of the above. The placenta facilitates the transfer of nutrients, gases (O2, CO2), and antibodies; removes metabolic wastes; and acts as an endocrine organ, producing hormones like hCG, progesterone, estrogen, and hPL essential for maintaining pregnancy.

C. The organ that connects the developing fetus to the placenta. The umbilical cord is the lifeline containing umbilical arteries (carrying deoxygenated blood from fetus to placenta) and an umbilical vein (carrying oxygenated blood from placenta to fetus).

D. All of the above. Through the blood vessels within it, the umbilical cord facilitates the transport of nutrients, oxygen, and antibodies to the fetus, and the removal of waste products and carbon dioxide from the fetus, all via the placenta.

B. Progesterone. While hCG maintains the corpus luteum initially and estrogen contributes, progesterone is crucial throughout pregnancy for maintaining the uterine lining, preventing contractions, and supporting fetal development.

B. 8 weeks. The embryonic period spans from fertilization through the end of the 8th week of gestation. During this time, organogenesis (the formation of major organs and body systems) occurs.

B. 3 weeks. The primitive heart tube starts to form and beat rhythmically during the 3rd week of embryonic development (corresponding to about the 5th week since the last menstrual period).

B. 8 weeks. By the end of the embryonic period (8 weeks), the rudimentary forms of all major organs and body systems have been established. Subsequent development involves growth and maturation.

B. Fetal development. Following the embryonic period, the developing human is referred to as a fetus. The fetal period (from week 9 until birth) is characterized primarily by growth and maturation of the already formed organs.

C. 16 weeks. While some muscle contractions occur earlier, coordinated movements that might be perceptible (quickening) typically begin around the 16th to 20th week of gestation.

A. 24 weeks. Around 24 weeks, fetal viability (the potential to survive outside the womb) is often considered possible because major organs like the lungs have developed sufficiently, though they still require significant maturation. Functionality increases throughout the fetal period.

A. 9 months (40 weeks). Human gestation typically lasts about 40 weeks when calculated from the first day of the last menstrual period (LMP), or about 38 weeks from fertilization.

C. The process of childbirth. Parturition refers to the entire process of labor and delivery, involving uterine contractions, cervical dilation, and the expulsion of the fetus and placenta.

B. Hypothalamus. The hypothalamus produces oxytocin, which is stored and released by the posterior pituitary gland. Oxytocin plays a critical role in stimulating uterine contractions during labor.

C. Oxytocin. While changes in estrogen/progesterone ratios contribute, oxytocin is the primary hormone responsible for inducing and strengthening the powerful uterine contractions required for labor.

A. To stimulate uterine contractions. Oxytocin’s main role during labor is to cause strong, rhythmic contractions of the myometrium (uterine muscle), which helps dilate the cervix and push the baby out.

B. It is expelled from the uterus. Following the delivery of the baby, further uterine contractions cause the placenta to detach from the uterine wall and be expelled, known as the afterbirth or placental stage of labor.

B. The process of milk production. Lactation refers to the synthesis and secretion of milk by the mammary glands to nourish the infant after birth.

C. Prolactin. Prolactin, secreted by the anterior pituitary, stimulates the mammary glands to synthesize and produce milk. Oxytocin is responsible for milk ejection (let-down).

A. The first milk produced after childbirth. Colostrum is a yellowish, thick fluid secreted by the mammary glands during the first few days postpartum. It precedes the production of mature breast milk.

D. All of the above. Colostrum is highly nutritious, packed with maternal antibodies (especially IgA) for immune protection, easily digestible, and helps clear the newborn’s digestive tract of meconium.

D. All of the above. Breast milk offers ideal nutrition tailored to the infant’s needs, contains antibodies and immune factors reducing infection risk, and the act of breastfeeding fosters maternal-infant bonding.

D. All of the above. Breastfeeding stimulates oxytocin release, which aids uterine involution (shrinking) and reduces bleeding. It also burns calories, potentially aiding weight loss, and is associated with long-term health benefits like reduced risk of certain cancers.