iGCSE Biology Section 3 lesson 2

1. iGCSE Biology Section 3 lesson 2

2. Content Section 3 Reproduction and Inheritance • Reproduction • - Flowering plants • - Humans • b) Inheritance

3. Content Lesson 2 a) Reproduction – Humans Humans 3.8 describe the structure and explain the function of the male and female reproductive systems 3.9 understand the roles of oestrogen and progesterone in the menstrual cycle 3.10 describe the role of the placenta in the nutrition of the developing embryo 3.11 understand how the developing embryo is protected by amniotic fluid 3.12 understand the roles of oestrogen and testosterone in the development of secondary sexual characteristics

4. Human gametes (sex cells)

5. Human gametes (sex cells) Male sex cell = sperm

6. Human gametes (sex cells) Male sex cell = sperm

7. Human gametes (sex cells) Male sex cell = sperm The chromosomes (genetic information) are tightly packed together in the nucleus Head Tail

8. Human gametes (sex cells) Male sex cell = sperm The chromosomes (genetic information) are tightly packed together in the nucleus Head The tail lashes from side to side and propels the sperm forwards Tail

9. Human gametes (sex cells) Male sex cell = sperm The chromosomes (genetic information) are tightly packed together in the nucleus Head The tail lashes from side to side and propels the sperm forwards Tail A single ejaculate may be about 4cm3 of fluid and may contain up to 500 million sperms

10. Human gametes (sex cells) Female sex cell = egg (ovum) Membrane Nucleus containing chromosomes Cytoplasm Jelly coat

11. Summary of sexual development

12. Summary of sexual development

13. Summary of sexual development

14. Summary of sexual development

15. Male and female reproductive systems

16. Male and female reproductive systems

17. Male and female reproductive systems

18. Male reproductive system TESTES (singular testis). Sperms are manufactured here. The testes are slightly cooler than the rest of the body.

19. Male reproductive system SCROTAL SAC (or scrotum). Alters position to maintain the optimum temperature for the testes.

20. Male reproductive system SPERM TUBULES – where the sperm are actually made. Combined length of over 500 metres!

21. Male reproductive system EPIDIDYMIS – coiled tube where the sperm are stored

22. Male reproductive system URETHRA – tube which runs down the centre of the penis – dual function, carrying both urine and sperms

23. Male reproductive system PENIS – male reproductive organ. During intercourse it fills with blood to become stiff and erect. Tip of the penis, the GLANS, is protected by the foreskin.

24. Male reproductive system SEMINAL VESICLE and PROSTATE GLAND – these glands produce a fluid which keeps the sperm alive and swimming vigorously. Sperm + fluid = semen

25. Female reproductive system OVARIES (singular ovary). Two, on either side of the abdomen. Every 28 days or so an egg is released.

26. Female reproductive system OVIDUCTS (also known as the Fallopian tubes) carry the eggs from the ovaries to the uterus. Fertilisation occurs here.

27. Female reproductive system UTERUS – if the egg is fertilised by the sperm, then it develops here into the baby during which time it is known as the womb)

28. Female reproductive system CERVIX – the neck of the uterus. Becomes dilated (opens up) just prior to the birth of the baby.

29. Female reproductive system VAGINA – the birth canal. Like the lining of the uterus, the vagina secretes a lot of mucus.

30. Female reproductive system CLITORIS – the female equivalent of the penis, can become erect during sexual intercourse

31. Sexual intercourse The erect penis is inserted into the vagina. Drops of fluid, secreted by the male’s glands, emerge from the tip of the penis and serve as a lubricant, as does the mucus lining of the vagina.

32. Sexual intercourse Rhythmical movement of the penis eventually results in ejaculation – semen is forcibly expelled from the penis into the vagina. The feelings experienced during ejaculation are known as orgasm. Female orgasm is usually brought about by stimulation of the clitoris.

33. Fertilisation Once inside the vagina,the sperm swim up through the uterus and in to the oviducts. If an egg is present in the oviduct then one sperm will enter the egg and fuse with the female nucleus – this is known as fertilisation. www.patient.co.uk

34. Fertilisation Once inside the vagina,the sperm swim up through the uterus and in to the oviducts. If an egg is present in the oviduct then one sperm will enter the egg and fuse with the female nucleus – this is known as fertilisation. www.patient.co.uk

35. Fertilisation Once inside the vagina,the sperm swim up through the uterus and in to the oviducts. If an egg is present in the oviduct then one sperm will enter the egg and fuse with the female nucleus – this is known as fertilisation.

36. Fertilisation After fertilisation has occurred, the egg divides repeatedly into a ball of cells which moves down the oviduct to the uterus. It now sinks into the soft lining of the uterus and becomes implanted. The woman is now pregnant. www.patient.co.uk

37. Content Lesson 2 a) Reproduction – Humans Humans 3.8 describe the structure and explain the function of the male and female reproductive systems 3.9 understand the roles of oestrogen and progesterone in the menstrual cycle 3.10 describe the role of the placenta in the nutrition of the developing embryo 3.11 understand how the developing embryo is protected by amniotic fluid 3.12 understand the roles of oestrogen and testosterone in the development of secondary sexual characteristics

38. Content Lesson 2 a) Reproduction – Humans Humans 3.8 describe the structure and explain the function of the male and female reproductive systems 3.9 understand the roles of oestrogen and progesterone in the menstrual cycle 3.10 describe the role of the placenta in the nutrition of the developing embryo 3.11 understand how the developing embryo is protected by amniotic fluid 3.12 understand the roles of oestrogen and testosterone in the development of secondary sexual characteristics

39. “Approximately once a month from puberty to the menopause, the human female experiences a menstrual cycle. This is part of a cycle of events which occurs inside her body”

40. The Menstrual Cycle

41. The Menstrual Cycle

42. The Menstrual Cycle The cycle starts with menstruation. During this time the uterus lining breaks down and passes out through the vagina. This is known as menstrual bleeding, or having a ‘period’.

43. The Menstrual Cycle

44. The Menstrual Cycle Thousands of immature eggs are present in the ovaries. Following menstruation, one develops within a protective structure called the Graafian follicle. Development takes about 14 days.

45. The Menstrual Cycle

46. The Menstrual Cycle After about 14 days the follicle moves to the edge of the ovary and the mature egg pops out into the oviduct. This process is called ovulation.

47. The Menstrual Cycle

48. The Menstrual Cycle During the time the lining of the uterus has been thickening, with many blood vessels. If the egg has been fertilised then it will become embedded in the lining and the pregnancy will continue. If not, then menstruation occurs ….

49. The Menstrual Cycle The whole menstrual cycle is controlled by hormones (special chemical messengers in the blood).

50. The Menstrual Cycle The pituitary gland, at the base of the brain, releases a hormone (FSH, or follicle stimulating hormone), which causes the follicle to develop in the ovary.