Unit 16.3 Human Reproduction

Unit 16.4 Sexual Reproduction in Humans

This is an index

12. Sperm Cell

3. Structure of MRS

13. Checking in Question

4. Check in Question

14. Egg vs Sperm cell

5. Structure of FRS

15. Lifecycle-Sexual Reproducing Organisms

6. Check in question -FRS

7. Fertilization I

16. The Embryo

8. Fertilization II

17. Developing Fetus

9. The Haploid Gametes

18 . Amnion, Fluid & Cord

10. Nucleus of Gametes vs Nucleus of Body cells

19. Labelling

11. Egg Cell

20-22. The Placenta

Male Reproductive System

Sexual Reproduction requires the fusion of a nucleus of a male gamete with that of nucleus of female gamete.The function of the following parts of the system is:1. Testes: Male gamete, sperm cell is made here via meiosis. Male hormone, testtosterone is also made in the testes. 2. Scrotum/Scrotal sac: Holds the testes outside the body to create ideal temperature for sperm production. 3. Sperm duct: Carries the sperm cells from the testes to the urethra during ejaculation. 4. Prostate gland: Makes an alkalne fluid, seminal fluid, that mixes with sperm to create semen. 5. Urethra: Carries semen from sperm duct to tip of penis 6. Penis: Inserted into the vagin and delivers semen into FRS.

Female Reproductive Sytem

• Ovary: Site for producing the egg cell/ovum. Meiosis happens to produce the female's gamete.

• Fallopian tube/Oviduct: Site for fertilization and so formation of the diploid zygote.
• Uterus: Site for implantation as the embryo attaches to uterus lining. The muscles of uterus contracts during labour to push baby out.
• Cervix: Neck of the uterus. It relaxes and dilates to allow baby to descend into vagina during labour.
• Vagina: Receive penis during intercourse and serves as a birth canal during delivery.

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pH of vagina is acidic and this makes is inhospitable for pathogens but would also kill sperm cells. Semen is alkaline so neutralizes vagina's pH.

An egg cell (which is actually an oocyte) is released from an ovary mid way the menstrual cycle

Uterus transplant is a temporary transplant to allow for one or two pregnancies. Would you transplant your uterus?

The position and the degree of softness or hardness of the cervix changes throughout menstrual cycle

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Fun Facts!

‘In fertilization, the nucleus of the sperm cell fuses with nucleus of egg cell and a DIPLOID ZYGOTE forms’

Fertilization occurs in the oviduct in women and inside the ovule of flowering plants!

Fertilization occurs in the oviduct in women and inside the ovule of flowering plants!

Lets look closely at our gametes!

The sperm and egg cells are HAPLOID, having been formed by meiosis. They each have one (set) of each chromosome. When they fuse the nucleus of zygote now has two of each chromosome (referred to homologues here in pic. Don't learn term) and so now it is DIPLOID. By having haploid nuclei, the chromosome number did not double upon fertilization, rather the diploid chromosome number of the organism is restored. A haploid nucleus s one of the adapative features of the sperm and egg cells. You'll learn about other adaptive fetaures further along the presentaton.

The nucleus sperm and egg cells differ from the nucleus of body cells

1. Sperm and egg cells are haploid with one of each set of chromosome. Body cells are diploid as cells of the zygote ultimately gve rise to them. 2. Nucleus of sperm and egg cells are formed by meiosis. Nuclei of body cells are formed by mitosis. 3. Nucleus of sperm and egg cell each has 23 chromosomes. Nuclei of body cells have 46 chromosomes.

Adaptive Features of Egg CellChallenge: Draw a labelled Diagram of the Egg Cell

Energy/Food Store

Jelly Coat

Spherical Shape

Hardens after fertilization to prevent another sperm cell rom fusing with the egg cell

Provides energy for zygote and early embryonic stages until embryo implants and starts to derive nutrients from maternal blood.

A sperm cell can fuse with it from any point of its circumference.

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Adaptive Features of Sperm Cell

FLAGELLUM:Propels the sperm cell by allowing it to be motile/to swim. So sperm cell can move to oviduct or towards egg cell/ovum. MITOCHNDRIA: Releases or provides energy/ATP via aerobic respiration. Energy is used for swimming. ACROSOME: Contains/Releases digestive enzymes that break down a pathway through jelly coat and surrounding protein and cell layer around the egg so that the membrane of the sperm cell can fuse with that of egg cell.

How well do you know the gametes? Prove it by completing this live workheet.https://www.liveworksheets.com/node/5896931

65%

90%

is visual

Can you compare the sperm and egg cell? Go ahead under the following headings.

Motility

Their Size and Number

Their Structure

Life Cycle of a Sexually Reproducing Organism eg. Humans.

Answer these.

1. The body cell contains 24 chromosomes. How many chromosoomes will be in the egg cell made by this organism? How many chromosomes will be on nucleus of zygote when sperm and egg cells fuse?

The zygote forms a ball of cells, an embryo.

The nucleus of zygote undergoes repeated mitosis divisions leading to formation of a ball of cells called an EMBRYO. This is happening while peristalsis and ciliary action of the oviduct moves the embryo towards the uterus. Approximately 7 days after fertilization, the embryo arrives at the uterus and attaches to the lining and burrows down in it. This is called IMPLANTATION. The cells of the embryo are STEM CELLS as they are unspecialized and ultimately continue to divide and over time produce more cells that becomes specialized and carry out specific functions eg. functioning as cardiac muscle cells, as skin cells etc

Development of Foetus

Structures supporting development of foetus

Amnion/Amniotc sac

Amniotic Fluid

Umbilical Cord

1. Absorbs shock and protects foetus from physical or mechanical damage.2. Prevents fetus from drying out. 3. Minimizes temperature fluctuations. 4. Promote bone and muscle development of foetus

Its a membrane that encloses the foetus suspended in amniotic fluid. Its a protective chamber and it separates fetus from maternal tissues of th uterus

Attaches foetus to placenta. Contains umbilical arteries and umbilical vein, blood vessels that carry deoxygenated and oxygenated blood away from and towards the foetus respectively.

Label the diagram below

The Placenta

Functions:1. Faciltates exchange of oxygen nutrients eg. amino acids, glucose, vitamins, water, minerals between fetus and maternal blood 2. Facilitates exchange of carbon dioxide and other excretory products from fetus to maternal blood. 3. Allows antibodies from mother's blood to get to baby, offering passive immunity. 4. Makes and releases oestrogen and progesterone hormones. 5. Prevents some pathogens and some toxins from reaching foetus.

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The Placenta

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The Placenta

Blood Flow through Placenta:Oxygenated maternal blood with soluble, simple nutrients being carried in materal(uterine artery) leak into blood filled spaces. Oxygen diffuses out of maternal blood and into foetal blood flowing through umbilical capillares along its concentration gradient. Water is exchanged via osmosis. Nutrients diffuse and are actively absorbed into foetal blood. The oxyegenated foetal blood, with nutrients and antibodies flows in umbilical vein in the umbilical cord to the foetus Foetal blood leaving the foetus in the umbilical artery in the cord has high CO2 conc. and other excretory products so these diffuse out of foetal blood flowing through umbilical capillaries and into maternal blood. This deoxygenated maternal blood is drained from the placenta via uterine/maternal vein. The structure of the placenta is adapted for exchange as it has large surface area, rich blood supply, short diffusion distance as there is only a thin membrane separating foetal and maternal blood.

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