The Human reproduction Chapter-3 Class-12

Human reproduction is any form of sexual reproduction resulting in human fertilization. It typically involves sexual intercourse between a man and a woman. During sexual intercourse, the interaction between the male and female reproductive systems results in fertilization of the woman's ovum by the man's sperm.

1. H U M A N R E P R O D U C T I V E SYSTEM AJAY KUMAR GAUTAM

2. INTRODUCTION Humans are sexually reproducing and viviparous organisms. Human beings are unisexual i.e. sexes are separate. Organs involved in reproduction are called reproductive organs which together form reproductive system. Organs of reproductive system of human being are divided into the essential and accessory organ. The essential sex organs or gonads include testes in males and ovaries in females. These are concerned with the formation of gametes and the secretion of hormones which control the activities of accessory sex organs and maintain the secondary sexual character. The secondary sexual character includes voice, body hair distribution and facial patterns. The accessory organs include the structures required for transmission and transfer of gametes such as genital ducts, glands and copulatory organs.

3. M A L E R E P R O D U C T I V E S Y S T E M : In man, the reproductive organs consists of paired Testis and paired as well as unpaired accessory organs. The paired accessory organs include: Male genital ducts Epididymis Seminal vesicle Ejaculatory ducts B u l bour e t hr a l g la nds The unpaired accessory organs include: Scrotum, Prostate gland Urethra penis .

4. Hence the male reproductive system consists of : Scrotum Testis Epididymis Vas deferens Ejaculatory duct Urethra Seminal vesicles Prostate glands Bulbourethral glands Penis

5. 1 . SCROTUM : Sac like structure having 2 lobes and each lobe has a testis . Scrotum is made up of thick pigmented skin . In the beginning testis is present in the abdominal cavity . During 7 month of pregnancy the testis descend down into the scrotum by the help of Inguinal Canal. If the testis is not descended, the abnormality is called Cryptorchidism . If the inguinal canal is not closed completely, it results Inguinal Hernia . Scrotum provides ( 2 - 2 . 5 ) °C less temperature than the normal body temperature which is required for the liability of the sperm . The testis is connected with the scrotum by the help of Gubernaculum . The testis is intra-abdominal in in elephant. The cavity of scrotum is connected with the abdominal cavity by inguinal canal. This canal gets closed after the testes have descended down, separating the abdominal cavity from the scrotal cavities. There is a connective tissue cord extending between the testis and abdominal wall known as Spermatic cord.

6. 2. TESTIS: The structural and functional unit of testis is Seminiferous tubules . Testis consists of three coverings, i . e . Tunica Vaginalis (Outermost) Tunica albuginea ( Middle ) Tunica Vasculosa ( Innermost ) It is divided into a number of small compartments or lobes called as Testicular Lobules ( about 250 ) Each lobule has 3 - 4 highly coiled structure called seminiferous tubules 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. T . S . o f T e s t i s : It is lined internally by Germinal epithelium and Basement Membrane provide support . The spermatogonium develops from the germinal epithelium, grows in size and derive nourishment from the Sertoli cells / Nurse cells / Sostentacular cells . The primary spermatocyte is divided by Meiosis to form Secondary spermatocyte . In between the seminiferous tubules, Leydig cells are present. Leydig Cells / Interstitial cells produce the hormone Testosterone . Testosterone is responsible for development of secondary sex organ, maintenance of accessory organs and muscular development in male individuals.

8. 3. 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 stores sperm. Epididymis serves as a duct for the passage of sperms from testis to vas deferens. Testis and epididymis together constitute the testicle.

9. 4. 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. It is a muscular tube that arises from the lower end of the cauda epididymis. Cutting or tying of vasa deferentia, called vasectomy. 5. EJACULATORY DUCT: It is a short duct formed by the union of vas deferens and the duct of seminal vesicle They enter into the prostate gland and finally open into urethra.

10. ACCESSORY GLANDS: There are 3 accessory glands present . Seminal Vesicle : Secreted fluid is alkaline in nature and called as seminal plasma which mainly constitute Fructose, clotting proteins and prostaglandins . This secretion helps to neutralize the acidity of male urethra and later on female reproductive system . Prostate Gland : The prostate is a gland that produces some of the fluid that carries sperm during ejaculation. The prostate gland surrounds the urethra, the tube through which urine passes out of the body. Secretion of prostate gland is acidic and contain certain enzymes like Acid Phosphatases . It is located below the urinary bladder . It helps in the nourishment of sperms .

11. Bulbourethral Gland / Cowper ’ s gland : These are small paired pea-sized bodies lying on either side of urethra at its termination. Bulbourethral glands are also known as Cowper glands, provide mucus proteins that lubricate the urethra and counteract the acidity of any urine leftover in the urethra. Secretion of this gland helps in lubrication of penis during sexual intercourse .

12. 6. URETHRA: Urinary bladder opens into urethra which further, runs through prostate gland and then through the center of penis to open out at its tip by urethral orifice or urinary meatus. The urethra is a common passage for both urine and semen. It has 4 parts i . e . Prostatic urethra Membranous urethra Bulbous Urethra Penile urethra

13. P e n i s: It is a cylindrical male copulatory organ. It is formed of three cylindrical mass of erectile tissues which are Two corpora cavernosa One corpus spongiosum. Urethra passes through corpus spongiosum and serves as passes for urine and semen. The enlarged tip of the penis is called the glans penis which is covered by a fold of skin is called prepuce.

14. At the time of sexual excitement erection of Penis occurs. It is caused by the dilation of blood vessels carrying blood to the sinuses of erectile tissues and the penis becomes rigid. Coitus: It is the sexual intercourse during which erected penis is inserted into the vagina of woman. Orgasm: It is the period in which the excitement is at the peak with increased heart rate, fast breathing rate, high blood pressure, dilation of blood vessels of skin. Ejaculation: It is the discharge of seminal fluid or semen from the urethra of male into the vagina of female at the end of sexual intercourse. It is also known as insemination. Semen : A copulating man discharges about ( 3 - 4 ) ml of semen in one ejaculation that contains about ( 200 - 300 ) millions sperms . Semen is an alkaline viscous fluid, formed of a mixture of sperms and secretions of vas deferens, seminal vesicles, prostate glands and Cowper’s gland.

15. S e m e n Secretions of seminal Vesicle + Prostate Gland + Cowper ’ s Gland + Sperm from Testis + Vas Deferens Sperm Path : Sperm from Testis-- Rete testis--Vasa efferentia–Epididymis-- Vas deferens--Ampulla--Ejaculatory --Urethra--Vagina of Female.

16. HORMONAL CONTROL AND REGULATION OF MALE REPRODUCTIVE SYSTEM : - Puberty: Puberty is the time in life when a boy or girl becomes sexually mature. It is a process that usually happens between ages 10 and 14 for girls and ages 12 and 16 for boys. It causes physical changes, and affects boys and girls differently. At the onset of puberty, GnRH is produced from hypothalamus that stimulates the anterior pituitary to secrete FSH and I CSH . LH stimulates Leydig cells to produce testosterone that leads to the development of secondary sexual character . FSH stimulates the Sertoli cells that helps in spermatogenesis as well as produces Inhibin hormone that works as negative feedback and stops GnRH secretion from Hypothalamus . GnRH: Gonadotrophin Releasing Hormone FSH: Follicle Stimulating Hormone ICSH: interstitial Cell Stimulating Hormone.

17. GAMETOGENESIS: Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis. Gametogenesis is divided into two types. 1. Spermatogenesis- Production of male gamete sperm. 2. Oogenesis- Production of female gamete ovum.

18. What are Gametes ? Gametes are an organism's reproductive cells. They are also referred to as sex cells. Female gametes are called ova or egg cells, and male gametes are called sperm. Gametes are haploid cells, and each cell carries only one copy of each chromosome.

19. SPERMATOGENESIS: Greek word: Sperma - Sperm/seed, Genesis - Formation Formation of male gamete i.e. sperm is called spermatogenesis. It occurs in the testis of male. Mitosis and meiosis process are involved in spermatogenesis. Spermatogenesis involved two steps: 1. Spermatidogenesis (Formation of spermatids) 2. Spermiogenesis/Spermatoleosis (Conversion of non motile oval spermatid to long motile sperm)

20. A. SPERMATIDOGENESIS: It includes three stages. i. Phase of Multiplication: In this phase, the primordial germ cells divide by mitosis to form Primary Spermatogonium. These cells contain diploid(2n) no. of chromosomes. • ii. Phase of growth: During this phase, a limited growth of spermatogonia takes place and increased in volume forming Primary spermatocyte. Primary spermatocyte is diploid(2n) in nature.

21. iii. Phase of maturation: This involves two divisions: Meiosis-I and Meiosis-II a. Meiosis-I: It is reductional in nature and reduces the no. of chromosomes from diploid to haploid Here, from one primary spermatocyte(2n), 2 secondary spermatocyte(n) are formed. b. Meiosis-II: It is equational division and hence no further change in chromosome number. Here from two secondary spermatocyte(n), 4 spermatids are formed. Spermatids are non-motile, oval in shape.

22. Stages of Spermatogenesis

23. B. SPERMIOGENESIS/SPERMATOLEOSIS: The conversion of spermatids into long, motile sperms is called spermatoleosis. Changes during Spermiogenesis: Condensation of nucleus occurs. It loses the RNA and acidic proteins and retains the DNA and basic proteins. Nucleus changes its shapes and becomes pointed. Golgi bodies changes into 2 fragments and the larger fragment forms Acrosome and the smaller fragment forms GOLGI NEST. The two centrioles are arranged one behind another as proximal and distal centrioles. Cytoplasm gets reduced and only remains in the tail region. Shape of mitochondria changes into spiral form. N o t e : F r o m o n e s p e r m a t o g o n i u m ( 2 n ) , 4 s p e r m s ( n ) a r e f o r m e d

24. S t r u c t u r e o f S p e r m s o f d i ff e r e n t m a mm a l s .

25. Ultrastructure of sperm: Sperms are generally tiny, microscopic, active, motile, and generally thread like in appearance. Sperm or spermatozoon (Pl. spermatozoa) is the male gamete containing haploid number of chromosomes. The sperm was first discovered by Leeuwenhock in man and other mammals. The general structure of spermatozoa in different animals is essentially similar but the shape and size varies from animal to animal. A typical mammalian spermatozoon consists of mainly 4 parts. Sperm ----- 1. Head (a. Acrosome and b. Nucleus) Neck Middle piece Tail HEAD: The anterior part of sperm is called head and consists of a prominent nucleus and an acrosome. In man, the head is flat, oval and spoon shaped.

26. The acrosome located at the tip of the head develops from the Golgi body and its from a double membranous sheath on the outer surface of the nucleus. Acrosome contains different enzymes which dissolves the egg membrane before fertilization. e.g. 1 . Hyaluronidase , 2. Corona dissolving zone lysin . Nucleus contains only DNA which acts as the genetic material. It helps in transmission of genetic characters from male parent. NECK: It consists of two centrioles i.e. Proximal Centriole -It is located at near a small depression on the nuclear surface and helps to initiate cleavage in the zygote. Distal Centriole- It is present in neck and helps to form the axial filament or tail of the sperm.

27. MI DD L E P I E C E : I t i s c y li nd r i c a l i n s h a p e . It contains a spiral mitochondrion that provides energy for swimming. It also contains a Ring Centriole (Annulus) with unknown function. Th entire middle piece is surrounded by a layer of cytoplasm is called Manchette. TAIL: It is the longest part of sperm having axial filament. It helps in swimming(locomotion). T h e t e r m i n a l p ar t i s n a k e d a n d c a ll e d e n d p i e c e . The axial filament is surrounded by a mall amount of cytoplasm covered over by a cell membrane. Locomotion of sperm occurs in liquid medium by lashing or undulating movement of tail.

28. F E M A L E R E P R O D U C T I V E S Y S T E M : Female reproductive system is more complex than male reproductive system. The female reproductive tract is located within the pelvis. This area provides support for the intestines and also contains the bladder and reproductive organs.

29. Parts of female Reproductive System: Pair of Ovaries Pair of oviduct/ Fallopian tube Uterus/Womb/Hystera/Metra Vagina Vulva/ External Genitalia . Mons Pubis . Labia majora . Labia Minora . Perineum Glands . Bartholin Gland . Mammary Gland/Breast

30. O v a r i e s: Human ovaries are a pair of almond-shaped structures, one on either side of the vertebral column in the abdominal cavity. Each ovary is about 1.5 to 3 cm long and 8 mm thick and is attached to the dorsal abdominal wall through mesovarium and abdominal wall. The ovary shows an outer cortex and inner medulla. In mature ovary, the cortex contains the follicles and corpus lutea. The medulla contains only large blood vessels and nerves. Ovary is internally lined by Germinal epithelium and Visceral Peritoneum surrounds it. The cells of germinal epithelium divide repeatedly to produce a ball of cells. One of these cells grow into a oogonium and the remaining cells surrounding it provide nourishment to the oogonium. This primary or young follicle go inside the ovary and changes into a matured graafian follicle.

31. Ovarian follicles are found in different stages. Primary Follicles Secondary Follicles Tertiary Follicles Mature Graafian Follicle

32. The ovaries are located within the pelvic cavity, and are supported by the mesovarium, an extension of the peritoneum that connects the ovaries to the broad ligament. Release of secondary oocyte or mature ovum by the matured graafian follicle is called ovulation. After rupturing, the degenerated Graafian follicle forms Corpus Lutem , it contains a yellow protein called lutein It secretes Progesterone hormone. If fertilization occurs this structure remains throughout gestation period. In absence of fertilization corpus luteum degenerate to form a white scar like structure called Corpus Albicans.

33. Structure of Graafian follicle: It is the matured ovarian follicle which in externally covered by : Theca Externa Theca interna Just beneath the theca interna, Membrane Granulosa membrane is present. Inside it, a fluid filled space present called Antrum filled with a fluid Liquor Folliculi apex(anterior) part of antrum is called as Cumulus ovaricus. In the center secondary oocyte is present which is covered by a non-cellular layer Zona Pellucida.