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1. Human Reproduction Q CONCEPT INSTITUTE

2. Sexual dimorphism Male reproductive system Male external genitalia Male internal genitalia 1 Key Takeaways Pen i s Scrotum Male accessory glands and ducts Journey of sperm Semen Hormonal control in male Male sex act 2 3 4 5 6 7 8 9

3. Female reproductive system Ov ar i es Oviducts U t er us Vag i na Female external genitalia Clitoris Mammary glands Lac t at i o n Hormonal control of female reproductive system 10 11 12 13 14 15 16 17 18 19

4. Spermatogenesis Oo genes i s Ov a dev el o p m ent i n e m b ryo Folliculogenesis Spermatocytogenesis Spermiogenesis Structure of sperm Game t o genes i s Fate of graafian follicle and secondary oocyte 20 22 23 24 21

5. Fertilisation Journey of ovum Sexual intercourse Journey of sperm Cap a cit a ti o n Fusion of gametes Embryonic development Post fertilisation events Gender determination 26 25 28 27 30 29 32 31 33

6. P lac e nta Foetal ejection reflex Gast r u lati o n Gest a tion Post implantation events Pa r turition Lactation 41 43 42 45 44 47 46

7. Menstruation Ovarian cycle Uterine cycle Lack of menstruation Menstruation cycle Menstrual care 36 35 38 37 40 39 Sum mary

8. Sexual Dimorphism Distinct male and female individuals exhibiting different characteristics D i = Two M o r ph ism = F o rms Male Female Morphological dimorphism : Differences in external features Male Female Anatomical dimorphism : Differences in internal features  These internal and external features lead to behavioural changes i.e., the way men and women t h i n k , ac t , e t c.  Many of these are hormone driven .  However, some of them also depend on the society we live in and our upbringing.

9. Male reproductive system Se co n d a ry sex organs Primary sex organs (Gonads) They help in transportation, maturation and storage of gametes. They are directly involved in the process of gamete production . They also produce sex hormones. Male gonads are testes Pen i s It includes penis and scrotum . Scrotum Male Reproductive System

10. Has erectile tissue to transfer sperm into the female genital tract Has an opening called urethral meatus Has an enlarged end called glans penis C o v er ed by a s hea t h k n o w n as fore s k i n Erectile tissues surrounding the urethra in penis aid in process of penis becoming hard and erect. Gl a n s penis Ur e th ral m e a t us For e s k in Penis Conducts urine and sperm Corpus spongiosum Corpora cave rnosa Erectile tissues Corpus spongiosum Corpora cavernosa Male External Genitalia

11. Removal of the foreskin is an elective procedure called circumcision . Circumcised men have lower risk of HIV infection. F o re s k i n G l ans Uncircumcised penis Circumcised penis Did you Know?

12. Sc r o tum Scrotum Present outside the abdominal cavity Sac like structure Contains testes 2-2.5 o C lower than body temperature: Ideal for sperm production and viability Testes hang in scrotum with the help of spermatic cord Spermatic cord consists of blood vessels, lymph vessels, nerves and cremaster muscles. Male External Genitalia

13. Test i s Testes 4-5 cm long, 2-3 cm wide Function: Production of sperms and secretion of androgens (male sex hormones) Extra-abdominal in most of the mammals (because sperm production, maturation, storage and survival requires 2-2.5 ℃ lower temperature than that of body temperature) Intra-abdominal in egg laying mammals (prototherians), elephants, whales, dolphins (located in main body cavity). Male Internal Genitalia

14. Test es Surrounded by three layers called tunicae Each testes has about 250 compartments called testicular lobules Each lobule contains one to three seminiferous tubules Testes of male baby are formed during 7 th to 8 th week of pregnancy and are intra- abdominal Testes migrate to scrotum during 7 th to 8 th month of pregnancy. Polyorchidism Presence of more than two testes i s a v er y r are congenital anomaly Male Internal Genitalia Tunicae Outermost layer Middle layer Inner layer Testicular lobule Seminiferous tubules

15. Seminiferous tubules Sertoli cells Interstitial space Regions outside the seminiferous tubules Leydig cells Synthesise and secrete male sex hormones called androgens Sperma t o zoa Spermatogonia One seminiferous tubule is about 70 cm long. Male Internal Genitalia Extend from basement membrane to lumen of tubule Pr o v i d e struc t u ral su p p o rt , nutrition and protection to developing sperms They secrete Androgen binding protein (ABP) Inhibin Mullerian inhibiting substance (MIS)

16. Ur i nary b l a d der Urethra Prostate gland Vas deferens Epididymis Cowper’s gland S em inal vesic l e Ej a cu l at o ry duct Male Accessory Glands and Ducts

17. Accessory Glands of Male Reproductive System Seminal vesicle Present at the behind the bladder Alkaline secretion : To neutralize male and female tracts Secretions contribute 60% of semen Contains: Fructose and calcium Prostaglandins Inositol

18. Accessory Glands of Male Reproductive System Prostate Single gland surrounding the urethra Contains calcium, phosphate ions, clotting enzymes and fibrinolysin Contributes alkaline secretions Cowper’s glands Also called bulbourethral glands Present on either side of urethra Alkaline secretion Secretes viscous mucus to lubricate glans penis

19. Sperm is produced in the seminiferous tubules. It passes through rete testis. It reaches the vasa efferentia. Journey of Sperm

20. Epididymis leads to the vas deferens. Epididymis is located along the posterior surface of each testis. It then leaves the testes to travel through the epididymis Journey of Sperm

21. The vas deferens ascends to the abdomen. It loops over the urinary bladder. I t rece i v es a d uct from t he seminal vesicles. Journey of Sperm

22. It travels further along the urethra and exits from the external opening called urethral meatus in the penis. Sperm then reaches the ur e t hra wh i ch i s a com m o n duct for urine and semen. Here, it receives secretions from the bulbourethral glands. It travels further along and enters the ejaculatory duct, where it receives secretions from the prostate gland. Journey of Sperm

23. Seminal plasma + sperm = semen Alkaline Ejected from penis during ejaculation Seminal plasma consists of secretions from Pro s t at e g l and Seminal vesicle Bu l b o ur e t hra l g l and Se m e n

24. Failure of testes to descend into scrotum C a n b e d ue t o d ef i ci ency o f testosterone Causes sterility as the testes are not at optimum temperature 1 5 % o f cr y p t o rch i d i sm i s a b d o m i n a l , 25% inguinal and 60% cases are high scrotal Orchidopexy - Surgery performed to correct cryptorchidism. Abdominal (15%) Inguinal canal (25%) High scrotal (60%) Normal testis Cryptor c hidism Cryptorchidism Did you know?

25. L eydig ce l ls Sertoli cells Hypothalamus increases the secretion of GnRH GnRH stimulates anterior pituitary gland Sperm production generally begins at teenage when a male enters puberty . T h i s i s d ue t o a s i g n i fic a nt increase in the secretion of gonadotropin releasing hormone (GnRH). Anterior pituitary gland increases the production of ICSH and FSH Interstitial cell stimulating hormone (ICSH) or luteinising hormone (LH) Follicle stimulating hormone (FSH) Acts on Acts on Hormonal Control in Male

26. Leydig cells A ndroge n Development of secondary sex organs and accessory glands Sertoli cells Factors Stimulates spermato ge n e s is Stimulates the synthesis of Stimulates the synthesis of Androgens are sex hormones. The major sex hormone in men is testosterone which is produced mainly in the testes. Androgens stimulate the process of spermatogenesis . Sertoli cells help in the process of spermiation . Hormonal Control in Male Testoste r o n e Stimulates spermio g e n esis

27. Arterioles in the penis contract Blood flow to the penis reduces, which subsides the erection Penis discharges the sperm into the vagina by wavelike contractions At the peak of sexual stimulation orgasm occurs Rush of blood into sinuses Penis becomes stiff due to hydraulic pressure Erection of penis C o pu l at i o n Subsidence of erection Male Sex Act 1 2 3

28. Female reproductive system Secondary sex organs (Not involved in gamete formation) Primary sex organs (Gonads) (Involved in zygote formation) V a gina Uter u s Ovidu c ts Ovar i es Female Reproductive System

29. They are the primary female sex organs . They are paired structures. They are located in the upper pelvic cavity. They produce female gametes called ova . They secrete female sex hormones . Each o v ary c o ntai n s a p o i nt o f en t ry and ex i t for blood vessels and nerves known as hilum . Ov ary O v ary Ovaries

30. M e du l l a Ovarian stroma Layers and parts Germinal epithelium Each ovary is covered by the cuboidal germinal epithelium Cortex Tunica albuginea Layer of connective tissue present beneath epithelium Section of ovary Ovaries

31. Gametogenic function Involves production of gametes Endocrine function Involves production of hormones Functions C o r t ex - It i s a re g i o n i n n er t o t he t un i ca a l bug i ne a . It consists of ovarian follicles surrounded by dense, irregular connective tissue that contains collagen fibers and fibroblast-like cells known as stromal cells . M e du l l a - It i s a re g i o n i n ner t o t he o v ar i an cort e x . Medulla consists of more loosely arranged connective tissue . It also contains blood vessels, lymphatic vessels, and nerves. The border between the cortex and medulla is indistinct. Ovaries

32. Ova r ies O estroge n Steroid hormones Progesterone Relaxin Inhibin/ Activin Primary sex hormones Ovaries

33. Progesterone Hormones of the ovary E st r o gen It stimulates the development of uterine epithelium. It is also secreted by the placenta and supports pregnancy. It maintains the endometrium. Estradiol is the principal estrogen. It is responsible for development of ovaries . It also regulates the menstrual cycle. It also controls the development of secondary sexual character. Ovaries

34. Extend from the periphery of each ovary to the uterus Ciliated, muscular and tubular structures Connect ovaries to the uterus Each fal l o p i an t ube i s ab o ut 1 - 12 cm l o ng Suspended via mesosalpinx 10 - 12 cm O v iducts

35. S tr u ct u r e The funnel shaped portion of e a c h tube Close to the ovary Infundibulum - Fimbriae - Ampulla - Isthmus - Finger-like projections Terminal part of the ovary Helps in the collection of ovum The widest and longest portion that makes up about the lateral two-third of the oviduct’s length Site of fertilisation O v iducts A short, narrow, thick-walled portion that joins the uterus

36. Functions Transportation of sperms Site of fertilisation Transportation of embryo Capture of oocyte Movement of oocyte Nutrition to fertilised oocyte O v iducts

37. It is a single, hollow, muscular structure. It has the size and shape of an inverted pear. It is present in the pelvic cavity. It is supported by the ligaments attached to the pelvic wall . It is smaller in women who have not been pregnant. It is larger in females who have been pregnant, and smaller ( atrophied ) when the sex hormone levels are low. It is suspended by the mesometrium . Ut e rus Ut e rus/Womb

38. Structure Fundus It is the upper dome shaped part of the uterus which lies above the opening of fallopian tubes. Implantation occurs here. Cornua It is the upper corner from which the fallopian tubes open into the uterus. Body It is the main part of the uterus. Cervix It forms the connecting link between the uterus and the vagina . Its cavity is known as cervical canal which forms the birth canal . Ut e rus/Womb

39. Histology Perimetrium/Serosa It is the outermost thin layer . It is composed of the simple squamous epithelium and areolar connective tissue. Myometrium It is the middle layer . It consists of three layers of smooth muscle fibres. These fibers are thickest in the fundus and thinnest in the cervix. During labour and childbirth, coordinated strong contractions of the myometrium in response to oxytocin from the posterior pituitary helps expel the foetus from the uterus. Ut e rus/Womb

40. Endometrium It is highly vascularised innermost layer . It is rich in glands and undergoes cyclic changes. Endometrium has three components: An innermost layer composed of simple columnar epithelium (ciliated and secretory cells) An underlying endometrial stroma The endometrial (uterine) glands Ut e rus/Womb

41. Functions It serves as part of the pathway for sperm deposited in the vagina to reach the uterine tubes. It is also the site of : Implantation of blastocyst Development of the foetus during pregnancy Labour During reproductive cycles, when implantation does not occur, the uterus is the source of menstrual flow. It protects and nourishes the embryo. It supplements the energy needs of sperms. It protects sperms from phagocytes. It pla y s a role in c apa c it atio n. Ut e rus/Womb

42. Uterus has enough strength to bear the weight of a new life T h e ut er us o f a pregn ant women has the longest muscle fibers. It a l so has a great t ens i l e s t re n g t h that gives it the ability to not break under high tension of contraction dur i ng t he t i me o f b i r t h o f a b a b y . Did you Know?

43. Vag i na It is a tubular, 8.5 cm long, fibromuscular canal lined with mucous membrane. It extends from the exterior of the body to the uterine cervix. It stretches or expands to: Accommodate the penis during intercourse Allow the child delivery during parturition Allow menstrual flow It ac t s as a p a s s ageway for ch i l d b i r t h. It forms birth canal along with cervix. Vagi n a

44. Hymen The opening of the vagina is called vaginal orifice . The opening of the vagina is often cov er ed p a r t i a l l y by a membra n e called hymen. Hymen is perforated to allow flow of menstrual blood. After its rupture, usually following the first sexual intercourse, only remnants of the hymen remain. Vagi n a Hymen Vaginal orifice

45. It, sometimes, completely covers the orifice, a condition called imperforate hymen . Surgery may be needed to open the orifice and permit the discharge of menstrual flow. Hymenoplasty is the surgery to reconstruct ruptured hymen. Hymen It can also rupture because of: Vaginal infection Cycling Horse riding or swimming Vigorous athletic activities Vagi n a Hymen Vaginal orifice

46. It is also called vulva 04 03 02 01 Vulva/ p u den dum Mons pubis Labia majora La b i a m i n o ra Clitoris Mons pubis Labia m a j o ra Labia minora Clitoris Female External Genitalia

47. M o ns p u bis It is the anterior most part . It i s a cu s h i o n o f f at t y tissue or adipose tissue layer. It is covered by skin and coarse pubic hair . Labia majora These are two large fleshy skin folds extending from mons pubis. They form the boundary of vulva . They are covered by pubic hair (partly). They contain a b unda n t sebaceous (oil) glands Labia minora These are two smaller thin skin folds without pubic hair and fat . They lie under the labia majora . They contain numerous sebaceous glands but very few sweat glands . Female External Genitalia

48. Clitoris Clitoris The clitoris is a tiny finger-like structure which lies at the upper junction of the two labia minora, above the urethral opening. The finger-like or small cylindrical mass is composed of: Two small erectile bodies i.e. corpora cavernosa Numerous nerves and blood vessels C o v er ed by a s k i n fo l d ca l l ed prepuce Female External Genitalia

49. Gla n s cl itor is Vaginal opening Ur e th ral o p e n ing Corpus cave rnosum When sexually stimulated, the corpus cavernosum or the erectile tissue gets swollen due to blood flow in the tissue. This is similar to the erection of male penis. The exposed portion of the clitoris is called glans clitoris ; homologous to glans penis. Clitoris It contains erectile tissue . Female External Genitalia

50. Pectoralis major muscles R ib s A functional mammary gland is characteristic of all female mammals. It helps in nourishing the young ones with the milk produced by mammary gland, in lactating mothers. Each breast i s a hem i s p heric pro jec t i o n o f v ar i a b l e size lying over or anterior to the pectoralis major muscle on the front wall of the chest. Estrogen stimulates duct growth Progesterone stimulates formation of secretory alveoli Infant fe m a le Y o ung adult Ma t ure adult In females, mammary glands are undeveloped until puberty. At puberty, they begin to develop under the influence of estrogen and progesterone hormones. Mammary Glands

51. A r e ola N ipple Each breast has one pigmented projection, called the nipple . It has a s er i es o f cl o se l y spaced openings of ducts called lactiferous ducts, from where milk emerges. The circular hyperpigmented area of skin surrounding the nipple is called the areola. It appears rough because it contains modified areolar (oil) glands . External Structure of Breast

52. Lobe Ducts Lob ules Fat t y t i s s ue A l v eo l i E ach m a m m ary g l a n d has 1 5 – 20 mammary lobes or compartments separat e d by a v ar i a b l e a m o unt o f adipose tissue containing clusters of milk secreting structures – alveoli embedded in fibrous connective tissue cavities (lumen) of alveoli which store milk Glandular tissue Internal Structure of Breast

53. Fibrous (Connective) tissue It supports alveoli and ducts. Fatty (Adipose) tissue It is present between the lobes. It covers the surface of mammary glands. The fatty or adipose tissue is present in variable amounts and determines the size of breasts. Internal Structure of Breast

54. Alveo li Alveoli M ammary tubule Al v e o li M ammary tubules Lobe M ammary tubules Each alveoli opens into mammary tubules . The tubules of each lobe join to form a mammary duct . Mammary duct Lo be Mammary duct Internal Structure of Breast

55. Lac t i f e rous duct Lobule containing alveoli Lobe Lactiferous duct Mammary am p ul l a Mammary duct Mammary t ubules Several mammary ducts join to form a wi d er mamm ary am p ul l a which is connected to lactiferous duct through which milk is sucked out. Am p u l l a Mammary duct Internal Structure of Breast

56. Functions of Breast Secretion and ejection of milk As so c iat e d wi t h pregnancy and childbirth Lactation Milk production Milk ejection Prolactin An t e rio r lo be o f pituitary gland Produ c t ion of milk by breast O x y t o cin Po st e rio r lo be o f pituitary gland Ejection of milk from breast

57. Lactation is the secretion and ejection of milk from the mammary glands. A principal hormone in promoting milk synthesis and secretion is prolactin (PRL), which is secreted from the anterior pituitary gland . Even though prolactin levels increase as the pregnancy progresses, no milk secretion occurs because progesterone inhibits the effects of prolactin. After delivery, t he levels of estrogen and progesterone in the mother’s blood decrease , and the inhibition is removed . The principal stimulus in maintaining prolactin secretion during lactation is the sucking action of the infant . Lactat ion

58. Oxytocin When a d o c t o r p l ace s a newb o rn o n i t s m o t her’ s chest in the moments after birth, oxytocin is released. The mother’s body temperature rises to create a warm, comforting place for the baby to snuggle. Skin-to-skin contact calms new babies and often helps them cry less. O xy t o cin cau ses a newb o rn t o see k o ut and l at ch on to its mother’s breast. The hormone floods the body during breastfeeding. Love/Cuddle Hormone

59. Mammary glands are also present in males but only in rudimentary form Sometimes, male breast tissue swells due to reduced male hormones (testosterone) or increased female hormones (estrogen) - Gynecomastia . Normal male Male with g y necoma s t i a Male Mammary Glands

60. Pro d uc es FSH ( F olli cle - stimu l at i ng hormone) E s t ro g en Pub i c ha i r grows B o dy s h a p e rounds Pituitary gland D eve lop me n t o f ovaries Development of secondary sexual characters H i gh p i t ch voice B o dy ha i r grows Breasts develop Vu l v a dev el o ps Estrogen induces development of secondary sexual characters, including: Changes in voice Development of external genitalia and breasts, body hair, pubic hair Widening of pelvis Deposition of fat in thighs buttocks and face At the time of pub er t y Hormonal Control of Female Reproductive System

61. 1 2 FSH stimulates : Growth and development of ovarian follicles Development of the egg or oocyte Formation of estrogen Estrogen in turn stimulates the secretion of GnRH . FSH also stimulates other hormones from the anterior lobe of the pituitary gland. 1 GnRH is secreted by the hypothalamus . It stimulates anterior lobe of pituitary to secrete FSH and LH. FSH and LH stimulate the ovary . 2 Hormonal Control of Female Reproductive System

62. 3 LH stimulates the corpus luteum to secrete progesterone . 4 4 Increasing levels of progesterone inhibit the release of GnRH , which in turn inhibits the release of FSH , LH and progesterone itself. 3 Hormonal Control of Female Reproductive System

63. Gametogenesis is the process of production of male and female sex cells (gametes), which are necessary for the development of new offspring. G a me tes Male Fe male Gametoge n es i s

64. Process of formation of sperms Begins during puberty Continues till death With advancing age, the number and quality of sperms reduces Spermatogenesis Spermiogenesis Spermatocytogenesis Formation of spermatids from spermatogonia Differentiation of spermatids into sperms Spermatoge n e s is

65. Spermatoge n e s is Spermatocytogenesis  Spermatogonia or the germ cells multiply by mitotic division to form primary spermatocytes .  Each spermatogonia is diploid and contains 46 chromosomes .  Primary spermatocyte then undergoes the first meiotic division to form two haploid cells called secondary spermatocytes , which have only 23 chromosomes each.  Secondary spermatocytes undergo second meiotic division to produce four equal, haploid spermatids . At Puber t y S pe r mat o g o n ia Mitosis di ffe r e nt iat io n Primary spermato cytes Secondary sperm at ocytes 2 nd meiotic division 1 st meiotic division S pe r matids

66.  Differentiation of spermatids into spermatozoa happens next.  After spermiogenesis , sperm heads become embedded in the Sertoli cells to form specialized sperms.  These sperms are finally released from the seminiferous tubules by the process called spermiation . Spermatoge n e s is Golgi complex Acrosomal vesicle B asal body Flagellum 1) Ap pear an c e o f ac ros o mal vesicle and flagellum in spermatid 2) Growth of ac r o so me and flagellum 3) Shedding of e x c e ss c yto pl asm 4) Mature sperm H ead Axon e me Mitochondria M idpi e c e T ail N u c l e u s Spermiogenesis

67. n Plasma membrane Acrosome S pe r m n u c leu s Middle piece Neck Mitochondria Middle Part  Contains numerous mitochondria which produce energy for motility which is essential for fertilisation. S pe r m t ail Tail  Tail helps sperm to move and to travel long distance. Structure of Sperm Head Plasma membrane is the outer layer of head Acrosome is a cap like structure which contains enzymes Nucleus is haploid i.e. contains 23 chromosomes

68. Ova development in embryo It begins in females before they are even born i.e. during their embryonic life . During early foetal development, primordial germ cells migrate from the yolk sac to the ovaries. The germ cells differentiate within the ovaries into oogonia (singular is oogonium). The process of formation of a mature female gamete is called oogenesis . Migration from yolk sac to ovary 1 2 Differentiation Oogonium (2n) Primordial germ cell (2n) Oogonia (2n) M it o sis Oog e n e sis

69. Oogonia are diploid (2n) stem cells that divide mitotically to produce millions of germ cells. The gamete mother cells (oogonia) then undergo first meiotic division but get arrested at prophase - I and are called as primary oocytes . Oogonium (2n) Primary oocyte (2n) Ovary during embryonic stage Primary oocyte 1 st m e io t ic di visio n Arr e st e d in pro ph as e - I Oogenesis - Ova Development in Embryo

70. Folliculogenesis It is the process of formation of follicles in the ovary. Follicular development happens in four stages: Primary follicle Secondary follicle Tertiary follicle Graafian follicle O og e n e sis

71. These are newly formed follicles containing primary oocyte . The primary oocyte is surrounded by single layer of flattened granulosa cells . Granulosa cells guide the development of oocyte and protect it. Pr i m a ry oocyte G ranu l o sa cells Folli c uloge n e sis 1) Primordial follicle Pr i mary oocyte Pr i mary follicle G ranu l o sa cells

72. Se co n d a ry follicle W i th c on tinuing ma turation , a pr ima ry fo l li c l e d e v e l o p s i n to a s eco n d ary fo l li c l e. With maturation, an envelope or sheath of connective tissue called theca surrounds the granulosa cells.  G ra n u l osa c e l l s r e st on a ba s e men t memb ra n e a nd the surrounding stromal cells form theca folliculi . Folli c uloge n e sis 2) Secondary follicle

73.  The secondary follicles transform into t er t i ary fo l li cles by dev el o p i ng a fluid filled cavity called antrum . The presence of antrum signifies the formation of tertiary follicle. The fluid of antrum is referred to as liquor folliculi. The theca gradually organizes into: Internal – theca interna External – theca externa T e rtiary follicle An t r u m 3) Tertiary follicle Folli c uloge n e sis

74. Completes meiosis-I Primary oo c yte (2 n ) S e c o n dary oocyte F irst po lar body Secondary oo c y t e (n) F irst po lar body (n) Folli c uloge n e sis Oocyte development in tertiary follicle During puberty in females, the arrested primary oocyte starts growing and completes its first meiotic division inside tertiary follicle. This reduction division occurs unequally to form a l arge secon d ary oo cyte a t i ny first p o l ar b o dy The secondary oocyte is haploid in nature and contains rich cytoplasm of primary oocyte. The fate of first polar body is unknown. Polar body is known to have no function .

75. Its diameter is 2.5 cm . G raaf i an follicle 4) Graafian follicle Tertiary follicles further grow and become Graafian follicles . It is final mature follicle which undergoes ovulation . Folli c uloge n e sis

76. Se co n d a ry oo cyte ( n) Zona pe l l uc i da C o ro n a radiata Stages of Development of Secondary Oocyte  Inside the Graafian follicle, a membrane develops around secondary oocyte called zona pellucida .  Bef o re o v ulati o n , a l a y er o f cel l s, that provide vital proteins , develop around the oocyte and are called corona radiata .

77. Se co n d a ry oocyte Fate of Graafian Follicle and Secondary Oocyte 1) During Ovulation Graafian follicle ruptures and releases the secondary oocyte (ovum) . The process of releasing an ovum (secondary oocyte) by Graafian follicle is called ovulation .

78. Graafian follicle transforms into corpus luteum . Corpus luteum maintains the layer of uterus by secreting progesterone. The secondary oocyte undergoes meiosis-II but stops at metaphase-II . During fertilisation , it completes mei o s i s - I I t o pro duce a matu re o v um and a t i ny second po l ar b o d y . Meiosis II F e rt ili sat io n M at u r e o v u m and second polar body Corpus lute u m Secondary oocyte Fate of Graafian Follicle and Secondary Oocyte 2) Post - Ovulation

79.  Before birth, lakhs of follicles are present in both ovaries, but at puberty only 60,000-80,000 follicles are left in each ovary. Primary follicle Follicular degeneration No more oogonia are formed or added after birth. A large number of primary follicles get degenerated during development o f a g i rl ch i l d. F olli cu l ar degenera t i o n i s a genet i ca l l y programmed process. Did you Know?

80. Female gamete Male gamete F e rtilisat ion Offspring 50% of genetic material from mother 50% of genetic material from father  Fertilisation is the fusion of male and female gametes to produce a single celled zygote , which gives rise to a new organism. F e rtilisation

81. 2 3 Fusion of sperm and ovum Journey of sperm 1 G J r o o u w r n t e h y o f o vum Events of fertilisation F e rtilisation

82. O v ary Ist h m u s Amp ulla Fimbriae The secondary oocyte is picked up 2 by finger like ends of the fallopian tube called fimbriae . The secondary oocyte released 1 from the ovary is carried away towards the fallopian tube. 1 2 3 4 Journey of Ovum With the help of cilia, secondary 3 oocyte moves forward to reach ampulla region . 4 At the ampulla region, the secondary oocyte awaits sperm for fusion.

83. The penis becomes erect and stiff due to the rush of blood into the sinuses. Following this, penis is inserted into the female vagina. Sexual Intercourse S tep 1: E r ection Insertion of penis inside vagina causes stimulation. At the peak of sexual stimulation, a sensation called orgasm occurs. This is required for ejaculation to occur. Stimulation helps in releasing lubricating fluid from both penis and vagina . Step 2: S timu l ation Peak stimulation leads to ejaculation. During ejaculation, the penis discharges the sperm outside by wavelike contractions . Step 3: E jac u ation During insemination, millions of sperms are deposited in the vagina. Step 4: I nsem inat i o n

84. The sperms pass through The cervix Enter cervical canal Move towards the uterus Then enter fallopian tubes  Inside the uterus, the contractions of the uterus assist the journey of the sperms further. These motile sperms swim rapidly inside the vagina. Some of these sperms die due to following conditions in vagina: Acidic environment Mucus secretion of vagina Uterus Cervical canal Cervix Journey of Sperm

85. Capacit a t io n Plas m a M e m brane Acrosome Before reaching the fallopian tube, sperm undergoes certain modifications known as capacitation .  Capacitation refers to the modifications in sperm which increases its ability to penetrate and fertilise ovum .  During capacitation, the medium inside the uterus wears off the plasma membrane of sperm head to expose the acrosome.  The hydrolytic enzymes in the exposed acrosome helps the sperm to penetrate ovum . Capacitation Membrane of sperm head is worn off exposing the acrosome of sperm which makes it highly penetrative

86. Fertilisation normally occurs in the ampulla of uterine (Fallopian) tube within 12 t o 2 4 h o urs af t er o v u l ati on. Sperms can remain viable for about 72 hours after deposition in the vagina, although a secondary oocyte is viable for only about 24 hours after ovulation .  Pregnancy is most likely to occur if intercourse takes p l ace dur i ng a 3 - d a y wi n d o w — from 2 days before ovulation to 1 d a y a f t er o v ulati o n. Fertilisation - Fusion of Gametes

87. Monospermy occurs - Entry of only one sperm into cytoplasm. Polyspermy is avoided . F o r f e r t ili sati o n t o o ccu r, a s p er m cell must penetrate the following layers first: Granulosa cells C o ro n a rad i at a Zona pellucida Among many sperms that reach ovum, one of the sperm passes between cells of corona radiata to reach zona pellucida layer. Penetration of Oocyte

88.  Once the sperm reaches zona pellucida, it binds to receptors on the zona pellucida and undergoes an acrosomal reaction. The hydrolytic enzymes/ digestive enzymes degrade zona pellucida. This enables the sperm to penetrate zona pellucida layer and plasma membrane of ovum. Penetration of Oocyte

89.  As the sperm enter ovum cytoplasm, ovum releases chemicals.  These chemicals block the receptors on zona pellucida of ovum, thereby blocking the entry of other sperms.  The sperm’s tail and body detaches from the head and disintegrates .  The sperm head travels towards the nucleus of the oocyte. Once a sperm penetrates the ovum, all the receptor sites for sperms, on the oocyte, are blocked. This ensures that polyspermy is avoided . This is referred to as depolarisation. Penetration of Oocyte

90. Hydrolysing enzymes released by sperms Zona lysin/ Acrosin Corona penetrating enzyme H ya l u r o nidase Digests the zona pellucida Dissolves corona radiata Dissolves the hyaluronic acid Penetration of Oocyte

91.  Once a sperm cell enters a secondary oocyte, the oocyte must complete meiosis II first. I t d i v i d es i nto a l ar g er o v um a n d a smaller second polar body that fragments and disintegrates. The pronucleus of both the sperm head and the ovum fuse.  A single diploid nucleus containing 46 chromosomes is formed.  The fertilised ovum now is called a zygote . Sperm nucleus Ovum nucleus 2nd polar body 1st polar body Ovum/ootid Fusion of Gametes

92. Embryonic Development It includes cleavage, blastulation, implantation, gastrulation and organogenesis . Cleavage First cleavage is completed after 30 hours of fertilization. Meridional plane completely divides the zygote into two blastomeres, which is known as holoblastic cleavage . Second cleavage is completed after 60 hours of fertilization. Blastulation Cleavage results in a solid ball of cells called morula having 8-16 cells. As morula enters uterus, outer peripheral cells enlarge and flatten to form trophoblast or trophoectoderm . Trophoblast cells secrete a fluid into the interior creating a cavity called blastocoel . With the formation of blastocoel morula is converted into blastocyst .

93. Embryonic Development Implantation Implantation is the process by which embryo attaches to the endometrial surface of the uterus.  By day 4-5, the early blastocyst starts developing villi and implants itself into the uterus at the end of 7 th -8 th day of fertilisation.

94. Implantation causes nutrient enrichment, enlargement of cells and formation of uterine part of placenta called decidua , which has three regions: decidua basalis, decidua capsularis and decidua parietalis. During implantation, endometrium of uterus thickens to support implantation. After attachment of blastocyst, the uterine cells divide rapidly and cover the blastocyst . As a result, the blastocyst becomes embedded in the endometrium of the uterus . This completes implantation. Endometrium of uterus Trophoblast (Secretes hCG: Pregn an c y h o rmon e ) Inner cell mass Embryonic Development

95. Transformation of blastula into multilayered and multidimensional structure ( Gastrula ) is known as gastrulation. Cells of inner cell mass rearrange to form a flat embryonic or germinal disc . The latter differentiates into two layers, an outer layer epiblast and inner hypoblast . Epiblast is the source of all germ layers in the embryo. Embryonic Development G a str ulation

96. After fertilisation , rapid mitotic cell divisions of the zygote, called cleavage, takes place. Each daughter cell formed as a result of cleavage is called a blastomere . The first division of the zygote begins about 24 hours after fertilisation and is completed about 6 hours later . By the third day after fertilisation , the second cleavage is completed, and four cells are formed. By day four , 8-celled stage called morula is achieved. By the end of day 4 or day 5 beginning , morula transforms into a 16-celled structure . By this time morula also reaches the uterus. Post Fertilisation Event

97. The early blastocyst structure consists of : an inner cell mass concentrated at one end a layer of trophoblast lining the inner cell mass The early blastocyst structure then matures into the late blastocyst structure and becomes completely merged with the endometrium. Inner cell mass starts receiving nutrients from the endometrium . Post Fertilisation Events

98. G ender o f a ch i l d i s det er m i ned by the sex chromosome contributed by the father during fertilisation. Mot her , ha v i ng a p a i r o f x chromosomes, can only contribute the x chromosome to the progeny. However, father having x and y for sex chromosomes can contribute either of the two. If the father contributes y chro m o s o me, t hen a bo y i s b o rn. If the father contributes x chro m o s o me, t hen a g i rl i s b o rn. 44 + XX Oogenesis 22 + X 44 + XY Sperma t o gene s is 22 + X 22 + Y 44 + XX Fema le M a le 44 + XY Gender Determination

99. Germinal layers Inner cell mass Gastrulation Trophoblast Endometrium P l a centa The blastocyst has two types of cells: Outer trophoblast Inner cell mass or embryoblast During the post implantation event, the trophoblast along with the endometrial lining contributes to the formation of placenta. The inner cell mass further divides to give rise to the germinal layers. Inner cell mass E n d omet r i um of uterus Trophoblast Post Implantation Events

100.  It thickens due to the supply of lots of blood vessels.  After the implantation, the trophoblast gives rise to the chorionic villi that comes in contact with the maternal blood vessels of the endometrium. Maternal B l o o d V ess e l s E n d o m etrium Endometrial lining Chorionic villi  The space between the villi growing from trophoblast is known as lacuna .  The maternal blood vessels come in contact with these empty spaces.  The cells developing from the trophoblast also have the foetal blood vessel. Endometrial lining Lacuna Pri m a ry C h o ri o n ic vi ll us Ma t e rna l Blood Vessels 1 2 Post Implantation Events To nourish the embryo, the endometrium prepares itself before implantation. 1 2

101. The maternal blood vessels and the foetal blood vessels give rise to the placenta . Simultaneously, there are also changes happening to the inner cell mass. The inner cell mass eventually gives rise to the germinal layers: ectoderm, mesoderm, and endoderm . Ecto de r m M e so de r m En do de r m Lacuna in contact with Maternal blood vessel Foetal Blood Vessels Post Implantation Events 3 3

102. Placenta Umbilical cord Vi l l i Mother’s blood vessels Placental membrane I n t er v ill o us space Fe t a l b l oo d vessels The developing foetus is connected to the placenta via umbilical cord Placenta - Formation Umbilical cord Placenta

103. Mot her Placenta F o e t us N u tr i ent s N u tr i ent s O x ygen Oxygen Metabolic wastes Metabolic wastes CO 2 CO 2 Nutrients from the mother are supplied to the foetus via placenta. Mother is the source of oxygen for the developing foetus. Foetus also returns carbon dioxide and excretory products to the mother. These products are then excreted out of the mother’s body. Placenta - Function

104. Placenta - Function Placenta confers passive immunity to the foetus by transferring antibody IgG . These antibodies work against diphtheria, scarlet fever, smallpox, measles , etc. P l acenta acts as a p r o t ec t i v e b arr i e r .  It protects the foetus from germs and pathogens circulating in the mother’s blood. PI a ce nta a l so stores g l y co g en and ac t s as a fo o d re serve for the foetus. Umbilical cord Placenta

105. hC G hP L Relaxin Estrogen and P r o gest erone Human chorionic gonadotropin (hCG) promotes progesterone secretion by corpus luteum It helps in maintaining the pregnancy  Human placental lactogen (hPL) breaks down fats in mother to supply energy to the foetus Relaxin helps in relaxing the ligaments of pelvis It helps in widening of the cervix It helps in childbirth It is also produced by ovary Estrogen stimulates growth of myometrium Progesterone makes endometrium viable for implantation The placenta releases several hormones only during pregnancy. Thus, it acts as a temporary endocrine gland . Various hormones include: Placenta – Temporary Endocrine Gland

106. Trophoblast Ep ib last B las t o c yst cavity H ypo bl ast Trophoblast Inner cell mass B las t o c yst cavity While the formation of the placenta takes place, simultaneously gastrulation also takes place. The blastocysts have inner cell mass, which help in the structural changes and formation of cylindrical cells .  The cells start dividing from the bottom and separate from the top. Consequently, two types of cells are formed: Epiblast on the top Hypoblast in the bottom Epiblast + Hypoblast = Embryonic disc Gastrulation 1 2 Gastrulation is the process by which the inner cell mass gives rise to a structure called gastrula that has various germinal layers . 1 2

107. Amniotic cavity Epiblast Hypoblast Ect o derm E n d o derm M e s o derm  The fluid starts accumulating in between the epiblast, forming a cavity known as an am n i o t i c cav i t y , wh i ch i s f ill ed with a fluid known as amniotic fluid .  T h e a mn i o t i c fluid ac t s as a s h o ck a b s o rber, protects the developing foetus and prevents desiccation of foetus. The hypoblast undergoes division and gives rise to the three germinal layers. - Ectoderm, mesoderm, and endoderm The structure formed is known as gastrula . 3 4 3 4 Gastrulation

108. Skeletal muscle cells Tubule cells of the kidney Red blood cells C ardi ac m usc l e c el l s Smooth muscle cells (in gut) Skin cells of epidermis N e u r o n Pigment cells Ectoderm (external layer) Lung cells (alveolar cell) T h yroid c e lls Digestive cells (pancreatic cell) Endoderm (i n ter n a l l aye r ) Gastrulation Mesoderm (middle layer)

109. Gestation period/ Pregnancy – 40 weeks T RI M E STER M ON T H W EE K 1 st 1 - 4 2 5 - 8 3 9 - 13 2 nd 4 14 - 17 5 18 - 22 6 23 - 27 3 rd 7 28 - 31 8 32 - 35 9 36 - 40  The first four weeks of the pregnancy includes ovulation, fertilization, implantation and gastrulation .  Post gastrulation, development of different organs and organ systems in the embryo occurs. Gestation Period/ Pregnancy

110. 2 nd month 1 st trimester 8 weeks - Limbs and digits begin to develop 1 st trimester 12 weeks 3 rd month Placenta becomes fully functional and takes over hormone production External genital organs and limbs are formed 1 st month 1 s t t r i mest er 4 w e e ks Baby is about strawberry seed size Major organ systems begin to form Baby grows rapidly Heart is formed Changes in the Embryo

111. 2 nd trimester - Ability to hear develops 16 weeks 4 th month - Ability to taste develops 6 th month 2 nd trimester 24 weeks Body is covered with fine hair - Eyelids separate Grease like protective covering develops on skin - Eyelashes are formed 5 th month 2 nd trimester 20 weeks Placenta is fully developed Reproductive system is fully developed First movement is seen Hair appears on head Changes in the Embryo

112. 8 th month 3 rd trimester 32 weeks - Sleep wake cycle is regularised 7 th month 3 rd trimester 28 weeks Frequency of eye movement increases Growth of brain occurs rapidly 3 rd trimester 36 weeks 9 th month - The foetus turns upside down with its head near the cervix Changes in the Embryo

113. The foetal ejection reflex involves uterine contractions that are generated by the placenta when the foetus is fully developed. This reflex is seen during the time of parturition. The foetal ejection reflex involves the interaction between the female reproductive system and the brain . Foetal ejection reflex  T h e p a i n i s a re su l t o f a f u ll y dev el o ped f o e t us. Foetal Ejection Reflex

114. Ful l y dev el o ped foetus Pushes down into the birth canal Stretching of cervix Nerve i m p ul s es Hypothalamus Posterior Pituitary R eleases o x y t o cin i nto the blood Contraction of myometrium Parturition Female Rep r o du c tive System B r a i n Foetal Ejection Reflex

115. Positive feedback loop during Parturition

116. Parturition is the process of delivery of foetus. The delivery of foetus is followed by expulsion of placenta. It is caused as a result of foetal ejection reflex . Umbilical c ord Placenta Parturit ion

117. The mammary glands produce milk towards the end of pregnancy Breast- feeding – process of feeding the milk to the baby which is produced by the mammary glands Colostrum – milk produced in the initial days of lactation Colostrum is rich in antibodies especially IgA 3 days 5 days 6 days 2 5 day s Lactat ion

118. It is regular discharge of blood and mucosal tissue (known as menses ) from inner lining of the uterus through vagina. Menstruation

119.  In the absence of fertilisation , the uterus enters the menstrual phase. No fertilisation Sperm Ovum Menstru ati o n Menstruation

120. Menstrual phase marks the onset of a menstrual cycle. On an average, a menstrual cycle lasts 28 days . Bleeding/menstruation usually lasts around 3 to 4 days . In the span of 28 days, there are two cycles that happen simultaneously: Ovarian cycle in the ovary Uterine cycle in the uterus Besides human beings, other close primates like monkeys and apes also menstruate. Menstruation

121. Ovarian Cycle 4 - 7 days 8 - 13 days Follicular phase The secretion of FSH is stimulated by GnRH . FSH stimulates the follicular growth and the oocyte development inside the follicle. There is a gradual increase in the levels of FSH and LH during the first seven days. The growth and the development of the follicle and the oocyte continues. Graafian follicle containing the secondary oocyte matures. 1 - 3 days

122. Ovarian Cycle 14th day Ovulatory phase  A steep increase in the LH levels is known as LH surge leads to the rupture of the Graafian follicle to release the secondary oocyte ( ovulation ). An over-the-counter home test that d e t ec t s a r i s i ng le v el o f LH can b e used t o pred i ct o v ulati o n a d a y in a d v ance ( OP K s - Ovulation predictor kits). It can detect LH in urine, released due to LH surge.

123. Luteal phase After ovulation, formation of corpus luteum (yellow body) from the remnants of the follicle is stimulated by LH . Post that, there is a reduction in FSH and LH levels. FSH and LH levels further decrease . Corpus luteum degenerates in the absence of fertilisation to form corpus albicans (white body). The duration of the luteal phase is always fixed in human females and i t i s a b o ut 14 d a y s. Hence, ovulation is expected on 26 th day of the menstrual cycle . 15 - 20 days 20 - 28 days Ovarian Cycle

124. Uterine Cycle Proliferative phase Duration: From the last day of menstruation up to the 14 th day of the menstrual cycle. Hormonal levels: Rise in estrogen levels due to secretion from growing follicles Low progesterone levels The proliferation of endometrium stimulated by estrogen takes place. There is an increase in number of the uterine glands and the blood vessels with the thickening of endometrium.

125. Uterine Cycle Secretory phase Duration: 15 th - 28 th day of the menstrual cycle Corpus luteum secretes large amount of progesterone . The progesterone maintains the endometrium, preparing for future implantation. Endometrium further thickens due to estrogen also secreted by corpus luteum. Estrogen and progesterone inhibit the release of FSH and LH. In the absence of fertilisation, corpus luteum degenerates . One menstrual cycle ends and the next starts with the onset of menstruation

126. Uterine Cycle Menstrual phase Duration: 3-5 days ( 1 st -5 th day of the menstrual cycle) The disintegration of corpus luteum decreases the level of progesterone which leads to menstruation. The endometrial lining of the uterus disintegrates along with its blood vessels.

127. Lack of Menstruation There can be some underlying causes for the lack of menstruation. Weig ht chan g es Med i cati o ns E x t re me exercise M e narche Profound stress I ll ness Pre g n ancy

128. Menstruation Cycle Pre - Menarche P H A S E 1 P H A S E 2 Post – Menarche / Pre - M e n o p a use It is the onset of menstruation at p uberty i n a fe m a l e. B I R TH MENAR CHE MENOPAUSE It is the ceasing of menstruation at o l d a ge i n a fe m a l e.

129. Menstrual care Use of menstrual hygiene products Discard of used products prop er l y Taking bath Washing hands General hygiene Balanced diet Sanitary pad M e n s t rual cu p C l o th p a d Tam p o ns Menstrual Care

130. Menstrual Hygiene Tampons It is for one-time use only. It is inserted into the vagina during menstruation to absorb blood and vaginal secretions. Sanitary pad It is designed for one-time use only. It needs to be discarded every 4-5 hours. Menstrual cup It i s a re usab l e a nd ec o - friendly cup made of medical grade silicone to collect menstrual blood inside the vagina. It needs to be washed and sterilised after every use. Cloth pad It i s a re usab l e p ad made up of cloth. It is eco-friendly.

131. Male reproductive system Male external genitalia Male internal genitalia Accessory ducts and glands It includes scrotum and penis. It includes testes. It includes sperm ducts and glands. Summary

132. T e s t is S e min iferous tubules Summary Sertoli cells (Nourishes the germ cells) Spermatozoa (Mature sperm) Interstitial space (Regions outside the seminiferous tubules) B l o o d ve sse ls Im mu n e ce ll s Testes Primary sex organs in human males Associated with the production of Sperms Male sex hormones Leydig cells (synthesise and secrete male sex hormones called androgens) Spermatogonia (Immature male germ cells) Ep idid y m is

133. Vas deferens Epididymis Vasa e f f e rentia Rete testis Seminiferous tubule And re aches That leads to R e t e t es t i s Vasa e f f e rentia It leaves testes to travel through Epididymis Vas deferens Sperm produced in seminiferous tubule It passes through Movement of sperms within the testis Summary

134. Summary 1 Sperms travel from testis to the penis and eject out of it during coitus. 2 3 6 5 4

135. Stimulates sp e rmato g e n e sis GnRH Te s t o sterone Leydig cells Sertoli cells An t e rio r pi t uitary ICSH FSH Hypothalamus Fa ct o rs Hormonal control in males Stimulates sp e rmio g e n e sis Erection of penis Penis becomes stiff due to hydraulic pressure Copulation The penis discharges the sperm into the vagina by wavelike contractions called ejaculation Subsidence of erection The arterioles in the penis contract reducing blood flow to the penis, which subsides the erection Male sex act Summary 1 2 3

136. Summary Female reproductive system Fal lop i an tubes Ovaries Uterus Cervix Vagina

137. Female r ep r o du c tive system O va r y U ter us O vi d u c ts V agi n a Pro du c e s female gametes Produces ovarian h o rmon e s Co nn e c t e d t o pelvic wall and uterus by ligaments Co v e r e d by ovarian stroma Infund ib ul u m Funnel- shaped Fimbriae Help in ovum collection Amp ulla Wider part of oviduct Isthmus Joi n s ute r us Op e ns int o vagina through cervix Pe r ime t rium E x t e rnal th in layer Myometrium S moo th m u scle middle layer Endometrium Lines uterine cavity S uppo rt e d by pelvic wall ligaments Receives the penis for copulation Summary

138. It i s a fa t t y t i s s ue cov er ed by skin and hair. They are the boundary of vulva. They lie under the labia majora. It i s a t i ny fin g er li ke str uc t u r e that contains erectile tissue. Summary 04 03 02 Vulva/ p u den dum 01 Mons pubis Labia majora Labia minora Clitoris

139. Lobe Ducts Lob ules Fatt y t i s s ue A l v eo l i Milk secreting structure External structure of breast Areola It co ntains modified sebaceous (oil) glands. Nipple It has a s er i es o f cl o se l y spaced openings of ducts called lactiferous ducts. Internal structure of breast Summary

140. FSH mainly stimulates the formation of estrogen. This in turn stimulates the secretion of GnRH. LH stimulates the corpus luteum to secrete progesterone. Increasing levels of progesterone inhibits the release of GnRH, which in turn inhibits the release of FSH, LH and progesterone itself. Hormonal control of female reproductive system Summary 1 GnRH is secreted by the hypothalamus which stimulates anterior lobe of pituitary to secrete FSH and LH. 2 3 4 1 2 3 4

141. Spe rmatogene s is Spermatogonia (2n) Mitos i s Secondary spermatocytes (n) Spermat i ds Spermatozoa Spermatozoa released from seminiferous tubules Primary spermatocytes (2n) Meiosis 1 Meiosis 2 Spermatocytogenesis Spermiogenesis Spermiation Spermatogenesis Process of production of sperm in the seminiferous tubules of testes during puberty Summary

142. Folliculogenesis Primary oocyte Ant rum Primary follicle Enlarged primary oocyte surrounded by granulosa cells S e c o n d a ry fol li cl e Matured primary follicle with differentiation of theca Tertiary follicle Mature follicle having a fluid filled cavity (antrum) Graafian follicle Final mature follicle which undergoes ovulation Transformed Graafian follicle post-ovulation Secondary oocyte C or p us lu t e um Summary 1 2 3 4 6

143. P r i ma r y oocy t e ( 2 n ) 1 st meiotic division Oogonium (2n) A rr es t ed i n p r o p has e - I Secon d a r y oocy t e ( n) First polar body (n) Co m p l e tes meiosis-I F etal l i fe B i r t h C h i l d ho o d Puberty Rep r o d uc t i ve phase O vulation Secon d a r y oocy t e ( n) St o p s at metap h as e - II Starts meiosis-II Secon d a r y o o cyt e ( n ) Sperm (n) Mature ovum (n) Sperm (n) Fertilisation Rep r o d uc t i ve phase 2 nd meiotic division Zygot e ( 2 n ) Second polar b o d y ( n ) Oocyte formation and developmental stages Fusion of nuclei Summary

144. Primary spermatocyte Se co n d a ry s p er matocyte Sperma t i ds Spermatozoa Primary Oocyte Secondary Oocyte O v um Spermatogenesis vs oogenesis Spermatogenesis Oogenesis Contains five stages Contains four stages Spermatogonia Oogonia Summary

145. Spermatogenesis vs oogenesis Spermatogenesis Oogenesis Meiosis produces cells of equal size Meiosis produces unequal cells (small polar bodies and large ovum) Gametes are formed by meiosis Gametes are formed by meiosis Release of gametes begins at puberty Release of gametes begins at puberty Summary

146. Erection S t i mu l at i o n Ej a cu l at i o n Insemination Capacitation Fertilisation Ov ulati o n Fimbriae guides ovum out of the ovary Cilia of the fimbriae guide ovum into ampulla Journey of sperm Journey of ovum Summary

147. Z y g o t e 2-celled stage ( B l astomere s) 4-celled stage (Blastomeres) C l eava g e C l eava g e 8 - ce ll ed stage (Blastomeres) 16 - ce ll ed stage (Morula) 32-celled stage with trophoblast and inner cell mass C l eava g e C l ea v a ge C l eava g e Implantation Post-fertilisation events Summary

148. Sum mary Post implantation events Gastrulation F o rmat i o n o f placenta Foetal ejection reflex Par t uri t i o n Lactation

149. Menstrual phase Ov ar i an cyc l e U t er i ne cyc l e F olli cu l ar p h ase Ovulatory phase Lut eal ph a se Proliferative phase Se cr e t o ry p h ase Men s t rual ph a se Summary

150. Reasons for lack of menstruation Weig ht chan g es Pre g n ancy I ll ness Profound str ess M e narche Menstrual care G ene ral hy g i ene Balanced diet Use of menstrual hygiene products Medication Discard of used products Extreme exercise Summary