Sexual Reproduction in Humans

1. Sexual Reproduction in Humans

2. Sexual reproduction is the only method of reproduction in humans • Sexual reproduction involves the fusion of specialised sex cells (gametes):- sperm (male gamete) & egg cell (female gamete). • The fusion of the nuclei male gameteand female gameteis called fertilisation. • Fertilisation results in the formation of a zygotefrom which a new individual develops.

3. Sperm cell • Gametes contain half the normal number of chromosomes i.e. they are haploid (n) • When male and female gametes fuse, the zygote formed have the normal number of chromosomes i.e. it is diploid (2n) • Body cells in human have 46 chromosomes while gametes have 23 chromosome i.e. the diploid number of chromosome is 46 while the haploid number is 23 Egg cell (ovum)

4. Male and female gametes

5. Comparing male and female gametes Sperm cell – Male gamete Egg cell - female gamete • Millions produced after puberty often throughout life • Small in size (0.002mm diameter) • Has very little stored food – uses sugars in seminal fluid for nourishment • Swim in fluid medium using a tail that lashes from side to side • One per month after puberty till menopause • Much larger in size (0.1mm diameter) • Protein and fat stored in the cytoplasm – enough to last till implantation • Does not move by itself – moved along oviduct by cilia & peristalsis

6. Male reproductive system • Functions of the male reproductive system are: • production of male gametes (sperms) • transfer of sperm into the female reproductive system • produces male sex hormone testosterone

7. ureter urinary bladder sperm duct Seminal Vesicle Prostrate gland cowper’s gland urethra penis testiss scrotum

8. Functions of parts of male reproductive system • scrotum - • Testes - • Sperm ducts - • Prostate gland - • Urethra - • Penis - • holds testes at cooler temperature than core body temperature • produces male gametes (sperms) & sex hormone testosterone • passage of sperms travel from testes to urethra during intercourse • secretes seminal fluid in which sperm swim • passage of semen (seminal fluid + sperm)during ejaculation • inserted into vagina during intercourse where it deposits semen

9. Human Reproduction - Male

10. Female reproductive system • Functions of the female reproductive system are: • to produce the egg cells (female gametes) • to provide a safe place for fertilisation • to provide protection and nourishment for a developing foetus • to produce sex hormones (oestrogen & progesterone)

11. Female reproductive system oviduct ovary uterus cervix vagina vulva

12. Functions of parts of female reproductive system • Ovary – • Oviduct – • Uterus – • Cervix – • Vagina – • produce female gamete & sex hormones oestrogen & progesterone • site of fertilisation & movement of egg cell and (or)embryo from ovary to uterus • site of implantation of embryo, foetus development & muscular wall contracts to push out foetus during birth • directs sperm into uterus ,mucus plug during pregnancy prevents infections & dilates at the beginning of birth • site of deposition of sperm during intercourse & it’s the birth canal – it stretches during birth to allow passage of foetus out of the body

13. Menstrual cycle • It is characterised by changes in the uterus and ovaries • The cycle lasts 28 days and if implantation does not occur, the cycle repeats itself • The menstrual cycle is controlled by hormones released by pituitary gland and the ovary

16. Hormones that control menstrual cycle • FSHstarts the development of one egg in a follicle in one of the ovaries. • Oestrogen causes the repair of the lining of the uterus after the last menstruation. • LH causes ovulation and stimulates the empty follicle to produce progesterone. • Progesterone causes the lining of the uterus to get thicker ready for implantation

17. Human Reproduction - Female

18. Fertilisation • Fusion (joining) of the nuclei of male gamete (sperm) and the female gamete (egg) to form a zygote

19. Development of the zygote zygote ball of cells (blastocysts) fetus

20. Foetus in the uterus (womb) oviduct placenta umbilical cord amniotic sac foetus amniotic fluid cervix vagina

21. Functions of the placenta • it forms barrier between blood of mother and blood of foetus, thus: • mother’s blood which is at too high pressure is prevented from flowing into foetus • prevents cells and large molecules in mother’s blood crossing into foetus • allows passage of nutrients & oxygen from mother to foetus • allows passage of wastes such as urea & carbon dioxidefrom foetus to mother

22. Protection of foetus in the uterus • foetus is protected by: • placental barrier between the mother & foetus from bacterial infections & some viral infections • Lymphocytes & phagocytes of maternal immune system • amniotic fluid inside the amniotic sac protects the foetus against mechanical damage

23. Breast-feeding • Describe the advantages and disadvantages of breast-feeding compared with bottle-feeding using formula milk

26. Effects of HIV on the immune system of a person with AIDS • Acquired Immunodeficiency Syndrome (AIDS) is caused by Human Immunodeficiency Virus (HIV) • HIV+ people are more at risk from infectious diseases • HIV enters the body & destroys lymphocytes which produce antibodies • without lymphocytes there are fewer antibodies to protect the body against invading pathogens • lymphocytes also protect the body against tumours, without lymphocytes tumours thus HIV+ people are more at risk from cancers

27. Methods of transmission of human immunodeficiency virus (HIV) • Sexual intercourse with an infected person • across the placenta & to baby at birth when maternal and baby’s blood mix if the mother is infected • through breast milk when an infected mother breastfeed • sharing needles, blades & surgical instruments with an infected person • blood transfusion with infected blood • blood products such as substances required for clotting given to haemophiliacs

28. Preventing the spread of HIV/AIDS • Transmission of HIV can be prevented trough: • Abstaining from sex intercourse • Use of condoms during sexual intercourse • Careful screening of blood before transfusion • Free needle exchange program to reduce use of shared needles among drug users • Taking anti – viral drugs by HIV + ve mothers to reduce mother to child transmission

30. Any Questions? • Will all this be in our exam? • Most likely YES • THANK YOU