Human reproduction Complete Chapter

The reproductive tissues of male and female humans develop similarly in utero until about the seventh week of gestation when a low level of the hormone testosterone is released from the gonads of the developing male. Testosterone causes the primitive gonads to differentiate into male sexual organs. When testosterone is absent, the primitive gonads develop into ovaries. Tissues that produce a penis in males produce a clitoris in females. The tissue that will become the scrotum in a male becomes the labia in a female. Thus the male and female anatomies arise from a divergence in the development of what were once common embryonic structures.

1. HUMAN REPRODUCTION Ajay Kumar Gautam

2. REPRODUCTIVE EVENTS Humans sexual reproduction, viviparous, unisexual. • Each sex has pair of gonads, reproductive duct and accessory structures. • Sex organs – Testis( paired) male , ovaries (paired) Gamete formation, hormones • Puberty 1. Gametogenesis – formation of gametes (sperms/ ova) 2. Insemination – transfer of sperms into the female genital tract 3. Fertilisation – fusion of male and female gametes leading to formation of zygote 4. Implantation – development of blastocyst and its attachment to the uterine wall 5. Gestation – embryonic development ( from conception to birth ) 6. Parturition– delivery of the baby ( child birth ).

3. THE MALE REPRODUCTIVE SYSTEM REFERENCE : NCERT DIAGRAMS

4. THE MALE REPRODUCTIVE SYSTEM Located in pelvis region . The Male reproductive system includes: A) A pair of testes. B) Accessory ducts. C) Accessory glands. D) External genitalia

5. L.S of Testes

6. LS OF TESTES Testis consists of three coverings, i. Tunica Vaginalis(Outermost)
ii. Tunica albuginea(Middle)
iii. Tunica Vasculosa (Innermost) In each testis -250 compartments called testicular lobules . Each lobule contain 1-3 convoluted (coiled) called seminiferous tubule that joined to form a network like structure called rete Testis. Rete Testis finally joined to form Vasa Efferentia and The vasa efferentia finally joined with the Epididymis.

7. Paired male gonads- sperm, hormones Oval in shape, length- 4 to 5 cm a width 2 to 3 cm Situated outside the abdominal cavity within a pouch called scrotum . Scrotum – low temp. Of the testes ( 2-2.5°C lower than the normal internal body temperature) – spermatogenesis. Testis consists of three coverings,
i. Tunica Vaginalis(Outermost)
ii. Tunica albuginea(Middle)
iii. Tunica Vasculosa (Innermost) An each testis -250 compartments called testicular lobules . Each lobule contain 1-3 convoluted (coiled) called seminiferous tubule. THE TESTES

8. Seminiferous tubule – Sperm Production Lined on its inside by two types of cells : a) Male germ cells (spermatogonia) – meiotic divisions – sperm formation. b) Sertoli cells (supporting cells) – provide nutrition to the germ cell. Regions outside the seminiferous tubules called Interstitial spaces, contain small blood vessels & interstitial cells/ Leydig cells . Leydig cells – synthesise & secrete male hormone Androgen ( testosterone) . Other immunologically competent cells are also present TS OF TESTES

9. Epididymis It is the highly coiled structure present above the testis. Epididymis leaves the scrotum and runs upward into the abdominal cavity. It has three parts i.e. Caput Epididymis Corpus Epididymis Cauda Epididymis It helps in transfer the sperm from testis. Vas Deferens The cauda Epididymis later on forms the vas deferens that enters the abdominal cavity and joins duct of seminal vesicle to form the Ejaculatory duct. Rete Testis Vasa efferentia Epididymis Vas Deferens Accessory Duct

10. Urethra https://teachmeanatomy.info/pelvis/viscera/urethra/ Male urethera provides a common pathway for the flow of urine and semen. It is much longer in female, measuring about 20 cm . Prostatic Urethera: Begins as a continuation of the bladder neck and passes through the prostate gland.
It is the widest and most dilatable portion of the urethra. Membranous Urethera: It is the second part which is situated behind the lower part o pubic symphysis and is smallest. It is the narrowest and least dilatable portion of the urethra. Penile Urethra : Penile urethera is situated in the Penis and is longest part. In the glans (head) of the penis, the urethra dilates to form the navicular fossa. Parts of Urethra

11. Penis This is the copulatory organ of man. It is cylindrical, erectile, pendulous organ suspended from pubic region in front of scrotum. It remains limp (Flaccid) but on sexual arousal, it becomes long, hard, and erect, ready for copulation ( coitus or intercourse). Erect human penis is, on average about 15-17 cm long. The penile mass is itself encased in a fibrous sheath, called Tunica albuginea. The interior of the penis if formed of three cylindrical cords of spongy, erectile (cavernous) tissues Corpora cavernosa (2) Corpus urethrae or spongiosum.

12. The penis B. Viewed from the side A. Viewed from below.

13. Accessory Glands of male Seminal vesicles: These are paired, tubular, coiled glands situated behind the urinary bladder. They secrete viscous fluid which constitute the main part of the ejaculates. Seminal fluid contains fructose, citric acid, inositol and prostaglandins. In rape cases, fructose help in diagnosis of victims. Prostate Gland: Chestnut shaped gland and is a collection of 30-40 tubuloalveolar glands which lie at the base of the bladder and surrounds the first part of the Urethra. It contributes alkaline component to the semen. ( Nutrilize acidic medium of uterus and acidic medium of urine). Bulbourethral glands or Cowper’s Gland : Two bulbourethral glands are pea-sized structures lying adjacent to the urethra at the base of penis. They secrete a viscous mucus which acts as a lubricant.

14. Semen Semen is a mixture of sperm and seminal fluid, which is the liquid portion of semen that consist of secretions of the seminferous tubule, seminal vesicles, Prostate gland and bulbourethral glands. The average volume of semen in an ejaculation is 2.5-5 ml, with sperm count of 200-300 million sperms. Semen has a slightly alkaline pH of 7.2-7.7, due to the higher pH and larger volume of fluid from the seminal vesicles. The prostatic secretion gives semen a milky appearance whereas the fluids from the seminal vesicles and bulbourethral glands give it a sticky consistency. Path of sperm through the male Body S - E - V - E - n U - P - SEMENIFEROUS TUBULE URETHRA EJACULATORY DUCT VAS DEFERENS EPIDIDYMIS RETE TESTIS VASA EFFERENTIA PENIS

15. Female Reproduction The female reproduction system is located in the pelvic region. It includes: 1. A pair of ovaries 2. A pair of oviduct. 3. Uterus 4. Cervix 5. Vagina 6. External genitalia. Oviducts, uterus, vagina – accessory ducts. A pair of the mammary glands ( nourishment of offspring) All parts are integrated structurally and functionally to support the processes of ovulation, fertilisation, pregnancy, birth and child care.

16. Female Reproductive System Female reproductive system is more complex than male reproductive system, because it has dual functions i.e. Production of Female gametes- Ova Nourishment of developing embryo(foetus) throughout the Gestation Period (38 weeks)/ 9 months + 7 days Parts of female Reproductive System: Pair of Ovaries pair of oviduct/ Fallopian tube Uterus/Womb/Hystera Vagina Vulva/ External Genitalia Mons Pubis Labia Majora Labia Minora Hymen Clitoris Glands: I Mammary Glands II. Bartholin’s Gland

17. Vulva/ External Genitalia Vulva/ External Genitalia Mons Pubis- Fatty tissue cushion covered by skin and pubic hair. Labia Major- Fleshy fold of skin & covers the surrounding of vaginal opening. Labia Minora- Paired folds of tissue in the form of lips. Hymen- Vaginal orifice is covered partially by membranous diaphragm called hymen. Clitoris – Labia minora fuse anteriorly to form a skin fold called prepuce in front of a small erectile organ, the clitoris.

18. Mammary Glands/ Breasts It is a modified sweat gland/ sebaceous gland. Shape and size of beast is totally depending upon the amount of fat (Adipose) present. There are number of mammary lobes are present which contain the mammary alveolus. The alveoli secrets milk and stores it. The alveoli open into mammary ducts and several ducts join to form ampulla which connected to the lactiferous duct through. Which milk is sucked out. At the tip of the breast a small swelling structure is found called nipple which is surrounded by a thick dark skin called areolae.

19. Hormone Control Prolactin- Milk producing hormone Oxytocin- Milk ejecting hormone

20. SPERMATOGENESIS The process of formation of haploid male gamete sperm in seminiferous tubules of testis is called spermatogenesis. The inner Wall of the Seminiferous tubule contains two types of cells as germ cells (spermatogonial cells) and sertoli cells. Germl cells divides and develops into sperms.The sertoli cell nourishes the developing sperms. The spermatogenesis takes place in two stages as spermatidgenesis and sprermiogenesis. Reference :https://www.toppr.com/ask/question/draw-a-diagram-of-the-sectional-view-of-human-seminiferous-tubule-and-label-its-parts /

21. Spermatidagenesis: It is the process of formation of spermatids. It involves 3 sub stages. Multiplication phase: The spermatogonial cells undergoes repeated mitotic division and forms large number of diploid spermatogonial cells. Growth phase: The spermatogonial cells, grow in size by cytoplasm and gets ready for maturation. Now the spermatogonial cells are called primary spermatocytes. Maturation phase: The diploid primary spermatocyte undergoes first meiosis resulting in the formation of two haploid cells called secondary spermatocyte. This later undergoes second meiotic division to produce four haploid spermiatids. SPERMATOGENESIS

22. Spermiogenesis: It is The process of formation of inactive non-matile spermiatid into active motile spermatozoa. The spermatid undergoes following structural change : The smaII vesicles of Golgi complex fuse to form a large cup like acrosome anterior to the nucleus. The distal centriole elongates to form a tail. The distal centriole elongates to form a tail. The mitochondria forms a large mass at neck region. The nucleus becomes elongated and forms a spherical shape . SPERMATOGENESIS

23. Hormonal control of the testes HYPOTHALAMUS ANTERIOR PITUITARY LH FSH Leydig Cell Sertoli Cells Testosterone Spermatogenesis Inhibin Negative Feedback STOP/ INHIBIT

24. Structure of mature Sperm Mature sperm cell consist of a head, a neck, a middle piece and a tail. A plasma membrane envelopes the whole body of sperm. The sperm head contain very little cytoplasm, a cap like structure, acrosome is present. They have a well-developed acrosome that covers 40 to 70 percent of the oval shaped head Acrosome is the product of Golgi complex and contains a number of contents such as acrosin enzyme in the acrosomal matrix. The midpiece is the central part of the sperm cell between the head and the tail. Packed mitochondria that provide the energy requires for swimming. The sperm tail is a thin, elongated structure that makes up about 80 percent of the entire length of the sperm.

25. Oogenesis The process of formation of haploid female gamete ovum in the follicles of ovary is called oogenesis.
Oogenesis starts during embryonic stage.
Germinal Epithelium of ovary divided mitotically to produce million of gamete mother cell or oogonia. No oogonia is formed or added after birth. Oogonia enters into meiosis-I , it proceeds Prophase-I , get suspended and forms primary oocytes. During puberty, the primary oocyte restarts its meiotic division.

26. Oogenesis Oogenesis takes place by three stages as follows: Multiplication Phase: The ovary is lined by germinal epithelium. These cells undergo mitotic cell division to form large number of diploid oogonia and follicle cells. Growth Phase: One of the diploid oogonia undergoes growth increasing in cytoplasm and accumulation of yolk. This enlarged oogonia is called primary oocyte. Maturation Phase: A fully grown primary oocyte undergoes 1 meiotic division results in the formation of two unequaled sized haploid cells.
The large secondary oocyte and a small sterile polocyte ( polar body) .The secondary oocyte undergoes II meiotic division to form a large ootid and a small sterile 2 polar body.
The first polar body also undergoes equal division to two cells.

27. Fertilization and implantation During copulation (coitus) semen is released by the penis into the vagina is called insemination. The motile sperms swim rapidly, pass through the cervix, enter into the uterus and finally reach the junction of the isthmus and ampulla (ampullary-isthmic junction) of the fallopian tube. Fertilisation – if the ovum and sperms are transported simultaneously to the ampullary isthmic junction. The process of fusion of a sperm with an ovum is called Fertilisation .

28. Sperm contacts with zona pellucida of ovum & induces changes in membrane that blocks entry of other sperm . Acrosome of sperm secretes lytic enzymes (hyaluronidase) helps in penetration into the ovum cytoplasm through zona pellucida & plasma membrane Meiotic division of secondary oocyte after sperm enters plasma membrane of the ovum. Second meiotic division – second polar body and ovum / ootid . Nucleus of Ovum + Sperm = Zygote . Sex of baby decided this stage Fertilization and implantation

29. https://www.britannica.com/science/fertilization-reproduction

30. Fertilization and passage of growing embryo through Fallopian Tube Fertilization and implantation Each gamete contains 23 Chromosome, the haploid (n) number. Thus, fusion of a sperm nucleus and an egg nucleus makes a zygote that have 46 chromosomes, thus restoring the diploid (2n) number. Male and female pronuclei approach each other and finally mixing up of paternal and maternal chromosomes ( Amphimixis) occurs resulting in the formation of synkaryon/zygote.

31. Sex Determination in Human

32. Sex Determination in Human Sex of the baby is decided during Fertilization. The chromosome pattern in human female is XX and that in male is XY. Therefore, all haploid gametes produced by the female (ova) have the sex chromosomes X, whereas in the male gametes (sperms) the sex chromosome could be either X or Y, hence 50 percent of sperms carry X chromosome while the other 50 percent carry the Y. After fusion of male and female gametes the zygote would carry either XX or XY depending on whether the sperm carrying X or Y has fertilized the ovum. The zygote carrying XX would develop into a female baby and XY would form a male. That’s why, scientifically it is correct to say that the sex of the baby determined by the father and not by the mother.

33. The mitotic division starts as the zygote moves through the Isthmus of the oviduct is called Cleavage. Forms 2,4,8,16 daughter cells called blastomeres. Embryo with 8-16 daughter cells called Morula. The morula continues to divide and transform into blastocyst as it moves further into the uterus. The blastomeres in the blastocyst are arranged into an outer layer called trophoblast, and inner group cells attached to the trophoblast called the inner mass cells. The trophoblast layer then gets attached to the endometrium and the inner mass cells gets differentiated as Embryo. After attachment the uterine cells divide rapidly and cover blastocyst. As a result, the blastocyst gets embedded in the endometrium of Uterus. This is called implantation and leads to pregnancy. implantation & Cleavage

34. Blastocyst Formation

35. Significance of Cleavage The distribution of the cytoplasm of the zygote, amongst the blastomeres. Increased mobility of the protoplasm. The restoration of cell size and the nucleocytoplasmic ratio characteristic of the species. Unicellular zygote is converted into multicellular embryo.

36. Pregnancy and Embryonic Development After Implantation, finger like projections appear on the trophoblast called chorionic villi, which are surrounded by the uterine tissue and maternal blood. The chorionie vill and uterine tissue become interdigtated with each other and jolntly form a structural and functional unit between developing embryo (foetus) and materal body called placenta. The placenta facilitate the supply of oxygen and nutrients to the embryo and also removal of carbon dioxide and excretory/waste material produced by the embryo. Placenta also acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG) , human placental lactogen (hPL). Estrogens, progestogens , etc. In the later phase of pregnancy. A hormone called relaxin is also secreted by the ovary. Let us remember that hCG, hPL and relaxin are produced in women only during pregnancy.

37. The antibiotics for measles, chicken pox, polIo etc , are present in the blood of mother and reach the embryo through placenta. Pathogenic viruses may also enter in embryo through placenta. If a female takes some harmful chemicals, liquor, drugs etc, during pregnancy, these may cross the placenta and on reaching into foetus may cause deformity during organogenesis. { Eg: Thalidomide, guaifenesin, Phenylephrine }. Teratogens: Agents inducing malformations are called Teratogens. Foetus after 3 months is less susceptible to Teratogens. Placenta and it’s function

38. Role of Human Chorionic Gonadotropin (hCG) The hCG maintains the ,corpus luteum and stimulate it to secrete Progesterone. Maintains the endometrium. Prevents Menstruation. Increased secretion of mucus. Forms a protective plug during pregnancy.

39. During pregnancy the levels of other hormones estrogens, progestogens, cortisol, Prolactin, thyroxine., Are increased several- folds in the maternal blood. Increased production of these hormones is essential for supporting the fetal growth, Metabolic changes in the mother and maintaince of pregnancy. Pregnancy and Embryonic Development

40. Blastocyst Formation - gastrulation Immediately after Implantation, the inner cell mass differentiate into an outer layer called ectoderm and an inner layer called endoderm. A mesoderm soon appears between These three layers gives rise to all tissues (organ) in adults. Its needs to be mentioned here that the inner cell mass contains certain cells called stem cells which have the potency to give rise to all the tissues and organs. In human beings, after one month of pregnancy. The embryo’s heart is formed. The first sign of growing foetus may be noticed by listening to the heart sound carefully through the stethoscope.

41. Parturition and Lactation The average duratíon of human pregnancy is about 9 months which is called the gestation period. Vigorous contraction of the uterus at t he end of pregnancy causes expuls i on/del iver y of the foetus. This pro ce ss of delivery of the foetus (childbirth) is called parturition . Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex. This triggers release of oxytocin from the maternal pituitary. Oxytocin acts on the uterine muscle and causes stronger uterine contractions, which in turn stimulates further secretion of oxytocin. The stimulatory reflex between the uterine contraction and oxytocin secretion continues resulting in stronger and stronger contractions. Thls leads to expulsion of the baby out of the uterus through the birth canal - Paturition . Soon after the infant is delivered, the placenta is also expelled out of the uterus.

42. The mammary glands of the female undergo differentiation during pregnancy and starts producing milk towards the end of pregnancy by the process called lactation . This helps the mother in feeding the new-born. The milk produced during the initlal few days of lactation is called colostrum which contains several antibodies absolutely essential to develop resistance for the new-born babies. Breast-feeding during the initial period of infant growth is recommended by doctors for bringing up a healthy baby. Antibodies provides passive Immunity to the child. It contains essentially the same concentrations of proteins and lactose as milk but almost no fat. Lactation