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B8 Reproduction

B8 Reproduction

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B8 Reproduction

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  1. B8 Reproduction Asexual and sexual reproduction

  2. Asexual reproduction • The process resulting in the production of genetically identical offspring from one parent. • Bacteria, fungi and some plants reproduce asexually. Sexual reproduction • The process involving the fusion of haploid nuclei to form a diploid zygote and the production of genetically dissimilar offspring

  3. B8 Reproduction Sexual reproduction in Humans

  4. Male reproductive system • Label the male reproductive system with the following organs: • Testes, scrotum, sperm ducts, prostate gland, urethra, penis • State the functions of each of the organs by completing the table provided. Sperm duct Produce the sperm Around the urethra, secrete seminal fluids Penis Passes through the penis to release urine and semen Scrotum

  5. rectum Male reproductive system bladder sperm duct (vas deferens) prostrate gland urethra penis testis scrotum

  6. Female reproductive system • Label the female reproductive system with the following organs: • Ovaries, oviducts, uterus, cervix, vagina • State the functions of each of the organs by completing the table provided. Cervix Where fertilisation occurs; transports ova to uterus Vagina Foetus develops in this muscular organ Ovaries

  7. Female reproductive system oviducts ovaries uterus cervix vagina Reproductive system

  8. Male and female gametes • The human male gamete is called a sperm cell. • The human female gamete is the ovum or egg cell. Sperm Ovum • constantly produced • 1 matures each month Both • 200 – 500 million in one ejaculation • Haploid nucleus -(1 set of single chromosomes) • Always contain X chromosome • Contain either X or Y chromosome • immotile (moves via cilia) • motile • 110μm in diameter • 50μm length

  9. The menstrual cycle • Annotate the handout using the information on the next few slides. • DO NOT copy out all the notes Uterine ling continues to thicken

  10. The menstrual cycle • Menstruation is the shedding of the uterine lining (period). • This occurs, on average, every 28 days in women who have gone through puberty. • Females are born with hundreds of immature egg cells in each ovary. • Every month, one follicle (containing an ovum) will mature. This is controlled by hormones from the pituitary gland.

  11. The menstrual cycle – the uterus • Day 1 of the 28 day cycle is the beginning of the period – the endometrium (lining of the uterus) is shed. • After menstruation is complete, the endometrium thickens to prepare for the implantation of the zygote. • If fertilisation occurs, the endometrium will remain thick to nourish the foetus. • If no fertilisation occurs, the endometrium is shed again. • All these changes are controlled by hormones.

  12. The menstrual cycle – the ovaries • During the first half of the 28 day cycle, a follicle in one ovary will mature. • On day 14, the ovum (egg) is released from the ovary and is moved down the oviduct. • The follicle in the ovary continues to make hormones in preparation for implantation. • The ovum will survive for 24h and must be fertilised in this time for pregnancy to occur • If no fertilisation occurs, the ovum is shed in the next period and a new follicle develops. Ovulation

  13. Fertilisation • The fusion of a sperm cell and an ovum • Occurs in the oviduct following ovulation • Only one sperm in the millions of sperm ejaculated will fertilise the egg • The nucleus of the sperm joins to the nucleus of the egg, giving the zygote a full set of chromosomes • Only 1 sperm can fertilise an egg fertilisation

  14. Zygote development

  15. Zygote development • The zygote is the fertilised egg • As the cell divides it is known as a blastocyst • Once it embeds in the endometrium, it is called an embryo • 8 weeks after conception: • facial features • internal organs • the brain can signal muscle movement • the heart is fully developed • external sex organs begin to form • The foetus is about 3cm long Fertilisation and early development

  16. The amniotic sac and fluid Amniotic sac Placenta Umbilical cord • The amniotic sac is filled with the amniotic fluid • The fluid supports the growing foetus and protects it from mechanical damage

  17. The placenta • Part of the embryo becomes the placenta • The placenta is embedded in the uterus • The foetus is connected to the placenta by the umbilical cord • Blood vessels from the foetus pass close to vessels of the mother in the uterus • Nutrients, gases and wastes are transported between the foetus and the mother • The placenta has a large surface area

  18. Carbon dioxide Urea Oxygen Glucose Ions and vitamins Amino acids • The umbilical cord joins the foetus to the placenta • The cord contains an artery and a vein to carry foetal blood to the placenta and back Water

  19. Breast feeding Breast feeding There is a lot of controversy as to whether a mother should breast feed, and for how long. There are a number of benefits to choosing breast feeding compared to bottle feeding with formula: • Establishes close bond between mother and baby • Baby has added immunity against infection • Breast milk contains antibodies for diseases the mother has already had • Reduce rate of SIDS (sudden infant death syndrome) • Less allergies (e.g. skin conditions and asthma) in baby • Child less likely to be overweight later • Helps woman’s uterus to shrink after birth • Helps woman to lose weight gained during pregnancy. • Can act as a birth control for the first 6 months • Convenient • Free

  20. HIV HIV – Human immunodeficiency virus • Infection with this virus can lead to AIDS – Acquired Immunodeficiency Syndrome • HIV attacks the white blood cells (lymphocytes), weakening the immune system • The body no longer produces enough antibodies against infections so it is harder to become well again • A person with AIDS often dies of diseases that a healthy person could fight off

  21. Preventing HIV The spread of HIV • HIV cannot be cured. • Its spread must be prevented: • Use condoms during sexual intercourse • Do not reuse needles • Donated blood is screened before use in blood transfusions Transmitted in blood or semen: • Unprotected sexual intercourse • Hypodermic needles • Unborn babies • At birth • Breast feeding • Blood transfusions