Questions: Human reproduction

Q1 Describe the main parts of the male reproductive system.

Answer (English): The male system has a pair of testes, a duct system, accessory glands and the external genitalia. The testes sit in the scrotum outside the abdomen, where the temperature is about two degrees lower than body temperature. The ducts are the rete testis, vasa efferentia, epididymis, vas deferens and ejaculatory duct, leading into the urethra. The accessory glands are the seminal vesicles, prostate and bulbourethral glands, whose secretions form the seminal plasma. The penis carries the urethra and serves as the organ of insemination.

Hinglish: Male system mein testes, ducts, accessory glands aur penis aate hain. Testes scrotum mein hote hain kyunki sperm banane ke liye temperature thoda kam chahiye. Har testis mein lagbhag 250 lobules aur unme seminiferous tubules hote hain. Ducts ka rasta rete testis, vasa efferentia, epididymis, vas deferens aur ejaculatory duct hai. Seminal plasma seminal vesicles, prostate aur bulbourethral glands banate hain, aur penis insemination ka organ hai.

Q2 Describe the structure of a seminiferous tubule and the functions of its cells.

Answer (English): A seminiferous tubule is a highly coiled tube, and its wall is lined by two cell types. The spermatogonia lie near the base of the epithelium and multiply by mitosis, and their daughters become primary spermatocytes and then sperm. The Sertoli cells are tall cells that reach from the base towards the lumen, and they feed the germ cells as those develop. Maturing sperm heads rest inside the Sertoli cells until they are freed. Beyond the tubule wall sit small blood vessels and Leydig cells.

Hinglish: Seminiferous tubule ki lining mein do types ke cells hote hain. Spermatogonia mitosis se badhte hain, unki santaan meiosis se sperms banati hai, aur Sertoli cells unhe khana aur support dete hain. Sperm release se pehle Sertoli cells mein dhanste hain. Tubule ke bahar Leydig cells hote hain jo androgens banate hain. Do functions ko alag likho, Sertoli nutrition deta hai aur Leydig hormone banata hai.

Q3 What is spermatogenesis? Give the steps with chromosome numbers.

Answer (English): Spermatogenesis is the formation of sperm from spermatogonia in the seminiferous tubules, and it begins at puberty. A spermatogonium is diploid with 46 chromosomes, and it multiplies by mitosis. Some spermatogonia become primary spermatocytes, each still diploid with 46 chromosomes. The first meiotic division is a reduction division and gives two haploid secondary spermatocytes with 23 chromosomes each. The second meiotic division gives four haploid spermatids from each primary spermatocyte. Spermiogenesis remodels the spermatids into spermatozoa, and spermiation releases them from the Sertoli cells into the lumen.

Hinglish: Spermatogenesis mein spermatogonia se sperms bante hain. Spermatogonium 2n = 46 hota hai aur mitosis se badhta hai. Primary spermatocyte bhi 46 chromosomes ka hota hai; pehla meiotic division do secondary spermatocytes deta hai jinke 23 chromosomes hote hain. Doosra meiotic division chaar spermatids deta hai. Spermiogenesis se spermatid sperm ban jaata hai aur spermiation se Sertoli cells se release hota hai.

Q4 How is spermatogenesis regulated by hormones?

Answer (English): At puberty the hypothalamus increases its secretion of gonadotropin releasing hormone, GnRH. GnRH acts on the anterior pituitary, which releases luteinising hormone and follicle stimulating hormone. LH acts on the Leydig cells, which increase their output of androgens, and these hormones push spermatogenesis along. FSH works on the Sertoli cells and prompts them to release factors that assist spermiogenesis.

Hinglish: Puberty par GnRH badhta hai, jo pituitary se LH aur FSH nikalwata hai. LH Leydig cells par kaam karke androgens banata hai, aur androgens spermatogenesis chalate hain. FSH Sertoli cells par kaam karta hai aur spermiogenesis ke liye factors deta hai. Chain yaad rakho: GnRH, LH aur FSH, Leydig aur Sertoli cells, phir sperm.

Q5 Draw and describe the human sperm.

Answer (English): A sperm has a head, neck, middle piece and tail, enclosed by a plasma membrane. The head contains an elongated haploid nucleus, and a cap, the acrosome, sits over its front. That cap holds enzymes that help the sperm get into the ovum. The neck joins the head to the middle piece, which is packed with mitochondria. These mitochondria generate the energy for the tail, and the tail beats to move the sperm.

Hinglish: Sperm ke chaar parts hain: head, neck, middle piece aur tail. Head ke aage acrosome hota hai jisme enzymes hote hain, aur andar haploid nucleus hota hai. Middle piece mein mitochondria energy dete hain aur tail hilkar sperm ko aage le jaati hai. Ek ejaculation mein 200 se 300 million sperms hote hain, aur normal fertility ke liye shape aur motility ke numbers yaad rakho.

Q6 Describe oogenesis from the fetal ovary to ovulation.

Answer (English): Oogenesis begins in the fetus, when a few million oogonia form in each ovary. No new oogonia are produced after birth. These cells enter prophase I of meiosis and stop as primary oocytes, each surrounded by granulosa cells as a primary follicle. At puberty some of these become secondary follicles, then tertiary follicles with an antrum. In the tertiary follicle the primary oocyte completes its first meiotic division unequally, giving one large secondary oocyte and one small first polar body. The follicle becomes the Graafian follicle, and ovulation releases the secondary oocyte.

Hinglish: Oogenesis fetal stage mein shuru hoti hai; oogonia banti hain aur phir prophase I par ruk jaati hain. Har primary oocyte ke chaaron taraf granulosa cells aate hain aur primary follicle banta hai. Puberty tak har ovary mein 60,000 se 80,000 primary follicles bachte hain. Secondary aur tertiary follicle ke baad Graafian follicle banta hai, jisme first meiotic division unequal hota hai aur ek badi secondary oocyte aur ek chhoti polar body banti hai. Ovulation secondary oocyte ko release karta hai.

Q7 Describe the menstrual cycle and the hormones that control it.

Answer (English): The menstrual cycle repeats about every 28 or 29 days in humans. It begins with the menstrual phase of three to five days, when the endometrium breaks down and bleeding occurs. In the follicular phase the primary follicles grow into a Graafian follicle and the endometrium regenerates, while FSH and LH rise and the follicles release oestrogen. Around day 14 a surge of LH makes the Graafian follicle rupture and ovulation occurs. In the luteal phase the corpus luteum secretes progesterone, which maintains the endometrium. If fertilisation does not occur the corpus luteum degenerates, progesterone falls, the endometrium breaks down and the next cycle starts.

Hinglish: Menstrual cycle har 28 ya 29 din mein repeat hota hai. Follicular phase mein follicles badhte hain, endometrium dobara banta hai, aur FSH aur LH badhkar oestrogen dete hain. Day 14 par LH surge se ovulation hoti hai. Luteal phase mein corpus luteum progesterone deta hai jo endometrium ko banaye rakhta hai.

Q8 Explain what happens during fertilisation.

Answer (English): Fertilisation happens in the ampulla of the fallopian tube when a sperm meets the ovum. As the sperm touches the zona pellucida, the egg membrane changes and blocks the entry of any further sperm, so only one sperm fertilises the egg. The acrosomal enzymes let the sperm pass through the zona pellucida and the egg membrane. Once inside, the sperm sets off the egg's second meiotic division. That division is unequal, so a small second polar body and a large haploid ovum result. The gamete nuclei now fuse into a diploid zygote that carries 46 chromosomes.

Hinglish: Fertilisation ampulla mein hoti hai. Sperm jab zona pellucida ko touch karta hai to membrane badal jaati hai aur doosre sperm andar nahi aa sakte, isliye ek hi sperm fertilise karta hai. Acrosome ke enzymes rasta banate hain, phir secondary oocyte ka second meiotic division poora hota hai aur second polar body banti hai. Sperm aur ovum ke nuclei milte hain aur zygote 2n = 46 banta hai. Baby ka sex yahin decide hota hai, X sperm se ladki aur Y sperm se ladka.

Q9 Explain implantation and the functions of the placenta.

Answer (English): The zygote divides by cleavage as it moves towards the uterus, giving first two, four, eight and then sixteen blastomeres. The 8 to 16 cell stage is the morula, which becomes a blastocyst with an outer trophoblast and an inner cell mass. The trophoblast attaches to the endometrium, the inner cell mass becomes the embryo, and uterine cells grow over the blastocyst so that it becomes embedded in the uterine wall. This is implantation. The placenta then forms from the chorionic villi of the trophoblast and the uterine tissue. It exchanges oxygen, nutrients and waste between mother and foetus through the umbilical cord, and it acts as an endocrine gland that makes hCG, hPL, oestrogens and progestogens.

Hinglish: Zygote cleavage se morula aur phir blastocyst banta hai, jisme bahar trophoblast aur andar inner cell mass hota hai. Trophoblast endometrium se judta hai aur blastocyst uterine wall mein dhas jaata hai; ise implantation kehte hain. Uske baad placenta banta hai jo oxygen aur nutrients deta hai, waste hatata hai, aur hCG, hPL, oestrogen aur progesterone banata hai.

Q10 Explain parturition and lactation.

Answer (English): Parturition is childbirth, and it begins with mild uterine contractions triggered by the fully developed foetus and the placenta, a response called the foetal ejection reflex. This reflex makes the maternal pituitary release oxytocin, which strengthens the uterine contractions, and stronger contractions release more oxytocin. The loop continues until the baby is pushed out through the birth canal, and the placenta is expelled soon after. The mammary glands differentiate during pregnancy and begin milk production towards the end of it. The first milk, called colostrum, is rich in antibodies that give the newborn resistance to infection, and doctors recommend breastfeeding during the early months for that reason.

Hinglish: Parturition yaani delivery, foetus aur placenta se shuru hoti hai jo foetal ejection reflex se mild contractions laate hain. Isse pituitary se oxytocin nikalta hai, contractions tez hoti hain, aur zyada oxytocin bhi nikalta hai; yahi positive loop baby ko bahar laata hai. Pehla doodh colostrum kehlata hai jisme antibodies hote hain, isliye initial months mein breastfeeding zaroori hai.

That completes the ten questions. The five MCQ quiz below checks the facts board papers ask most often about the testis, ovulation and the zygote.