Humans reproduce sexually and give birth to young ones, so they are viviparous. Fertilisation occurs inside the female reproductive tract. Gametes are haploid and fuse to form a diploid zygote. LH surge induces ovulation. Fertilisation occurs at the ampullary-isthmic junction, and the zygote develops into a blastocyst that implants in the uterus. The placenta connects foetal and maternal tissues for exchange.
(a) sexually (b) viviparous (c) internal (d) haploid (e) diploid (f) ovulation (g) luteinising hormone (LH) (h) fertilisation (i) ampullary-isthmic junction of the fallopian tube (j) blastocyst (k) placenta.
The male reproductive system consists of paired testes in the scrotum, ducts including rete testis, vasa efferentia, epididymis, vas deferens, ejaculatory duct and urethra, accessory glands including seminal vesicles, prostate and bulbourethral glands, and the external genitalia, the penis. These labels should be placed in their anatomical positions.
A correct labelled diagram should show testes, scrotum, epididymis, vas deferens, ejaculatory duct, urethra, penis, seminal vesicles, prostate gland, bulbourethral glands and urinary bladder.
The female reproductive system includes paired ovaries and oviducts, a uterus, cervix, vagina and external genitalia. Each fallopian tube has the infundibulum with fimbriae near the ovary, followed by ampulla and isthmus opening into the uterus. These structures should be labelled clearly.
A correct labelled diagram should show ovaries, fallopian tubes or oviducts, infundibulum, fimbriae, ampulla, isthmus, uterus, cervix, vagina and external genital region.
The gonads have gametogenic and endocrine functions. Seminiferous tubules in testes produce sperms, while Leydig cells secrete androgens. Ovaries produce female gametes and form follicles/corpus luteum that secrete hormones regulating the menstrual cycle and pregnancy.
Testes produce sperms and secrete androgens such as testosterone. Ovaries produce ova and secrete ovarian hormones such as oestrogen and progesterone.
Each testis has many seminiferous tubules. The inner lining has spermatogonia and Sertoli cells. Spermatogonia divide and differentiate through stages of spermatogenesis. Sertoli cells provide nourishment to developing germ cells. Outside the tubules are interstitial spaces with Leydig cells, blood vessels and immune cells; Leydig cells secrete androgens.
A seminiferous tubule is lined by germinal epithelium containing male germ cells and Sertoli cells. The spaces between tubules contain interstitial or Leydig cells.
Spermatogonia multiply by mitosis. Some differentiate into primary spermatocytes, which undergo the first meiotic division to form secondary spermatocytes. Secondary spermatocytes undergo the second meiotic division to form haploid spermatids. Spermatids transform into spermatozoa by spermiogenesis and are released from Sertoli cells by spermiation.
Spermatogenesis is the formation of haploid spermatozoa from diploid spermatogonia in the seminiferous tubules of testes.
GnRH from the hypothalamus stimulates the anterior pituitary to release LH and FSH. LH acts on Leydig cells to stimulate androgen secretion. FSH acts on Sertoli cells, which help spermiogenesis and secrete factors including inhibin. Androgens support spermatogenesis.
GnRH, LH, FSH, androgens and inhibin regulate spermatogenesis.
After meiosis, haploid spermatids are not yet mature sperms. They undergo structural changes to form head, acrosome, middle piece and tail; this is spermiogenesis. Mature spermatozoa are then released from their association with Sertoli cells in spermiation.
Spermiogenesis is the transformation of spermatids into spermatozoa. Spermiation is the release of spermatozoa from Sertoli cells into the lumen of seminiferous tubules.
A human sperm has a head containing the haploid nucleus and an acrosome with enzymes for ovum penetration. The middle piece contains mitochondria that provide energy. The tail provides motility. These parts should be labelled clearly.
A correct labelled diagram should show head, acrosome, nucleus, neck, middle piece with mitochondria, tail and plasma membrane.
The male accessory glands add fluids to sperms to form semen. Seminal plasma nourishes and supports sperm motility and function. NCERT lists fructose, calcium and enzymes as major components.
Seminal plasma contains secretions of the seminal vesicles, prostate and bulbourethral glands and is rich in fructose, calcium and certain enzymes.
Accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens, which conduct sperms from the testis to the urethra. Accessory glands, including seminal vesicles, prostate and bulbourethral glands, secrete fluids that nourish sperms, lubricate the tract and make semen.
Male accessory ducts transport, store and conduct sperms, while accessory glands add secretions that form seminal plasma and support sperm motility and viability.
During foetal life, oogonia multiply and enter meiosis to become primary oocytes. Each primary oocyte is surrounded by follicular cells to form a primary follicle and remains arrested in prophase I. At puberty, some follicles develop in each cycle. A primary oocyte completes meiosis I to form a secondary oocyte and first polar body. The secondary oocyte begins meiosis II and is ovulated. Meiosis II completes only after fertilisation, producing the ovum and second polar body.
Oogenesis is the formation of a mature haploid ovum from oogonia in the ovary.
The ovary has an outer cortex and inner medulla. The cortex contains follicles at different developmental stages, including primary, secondary, tertiary and Graafian follicles, and may contain corpus luteum after ovulation. These should be labelled along with surface layers and stroma.
A correct labelled section should show germinal epithelium, tunica albuginea, ovarian stroma, follicles at different stages, Graafian follicle, corpus luteum and blood vessels.
The mature Graafian follicle contains a fluid-filled antrum and the oocyte surrounded by zona pellucida and corona radiata. Granulosa cells line the follicle, and the theca layers surround it. The oocyte is attached to the follicular wall by cumulus oophorus.
A correct labelled diagram should show secondary oocyte, zona pellucida, corona radiata, antrum, granulosa cells, theca interna, theca externa and cumulus oophorus.
The corpus luteum maintains the uterine lining through progesterone. The endometrium undergoes cyclic changes and becomes receptive for implantation. The acrosome helps sperm pass through egg coverings. The tail enables sperm movement. Fimbriae sweep the ovulated oocyte into the oviduct.
(a) Corpus luteum secretes progesterone. (b) Endometrium supports implantation and pregnancy. (c) Acrosome contains enzymes that help sperm penetrate the ovum. (d) Sperm tail provides motility. (e) Fimbriae help collect the ovum after ovulation.
(a) Androgens are produced by Leydig cells, not Sertoli cells. (b) Sertoli cells nourish developing spermatozoa. (c) Leydig cells are found in the testis, not the ovary. (d) Leydig cells synthesise androgens. (e) Oogenesis occurs in the ovary, not in the corpus luteum. (f) Menstruation stops during pregnancy. (g) Hymen may be torn or stretched for reasons unrelated to sexual intercourse, so it is not a reliable indicator.
(a) False. (b) True. (c) False. (d) True. (e) False. (f) True. (g) True.
GnRH stimulates pituitary release of FSH and LH. FSH promotes follicular growth and oestrogen secretion. The LH surge causes ovulation and corpus luteum formation. The corpus luteum secretes progesterone, which maintains the endometrium. If fertilisation does not occur, falling hormone levels cause menstruation.
The menstrual cycle is the cyclic change in the female reproductive tract, especially ovaries and uterus, that prepares for pregnancy and includes menstruation if fertilisation does not occur. It is regulated by GnRH, FSH, LH, oestrogen and progesterone.
Signals from the foetus and placenta trigger mild uterine contractions called the foetal ejection reflex. This stimulates release of oxytocin from the maternal posterior pituitary. Oxytocin intensifies uterine contractions, and prostaglandins also support labour. The positive feedback continues until the baby is delivered.
Parturition is the process of childbirth. It is induced mainly by foetal ejection reflex, oxytocin and prostaglandins, with endocrine signals from the fully developed foetus and placenta.
A human female produces ova with only an X chromosome. A male produces two types of sperms: X-bearing and Y-bearing. An X-bearing sperm fertilising the ovum produces XX, a female child; a Y-bearing sperm produces XY, a male child. Therefore blaming the mother is biologically wrong.
This is not correct because the sex of a child is determined by whether the fertilising sperm carries an X or a Y chromosome, and sperms are produced by the father.
In a typical menstrual cycle, one secondary oocyte is ovulated. Identical or monozygotic twins form when one zygote splits into two embryos. Fraternal or dizygotic twins form when two separate ova are fertilised by two different sperms.
Usually one egg is released in a month. Identical twins usually arise from one fertilised egg, so one egg was released. Fraternal twins arise from two different eggs, so two eggs were released.
Dogs are multiparous and normally produce litters. Each puppy generally develops from a separate ovum fertilised by a sperm. Therefore a litter of six puppies usually indicates that six ova were ovulated and fertilised.
Six eggs were most likely released.