Disclaimer: Due to unforeseen difficulties, we have had to take down the images on this notes page. They will be replaced shortly. We apologise for the inconvenience, but hope that the new images will provide you with an even better learning experience.

 

  1. Identify on diagrams of the male reproductive system: the testes, scrotum, sperm ducts, prostate gland, urethra and penis, and state the functions of these parts.

 

The vas deferens is the sperm duct. Also, testis is singular, while testes is plural.

Functions:

  • The testes: The glands in which sperm and testosterone are produced.
  • Scrotum: Protect testes and keep them at several degrees lower than the normal body temperature.
  • Sperm ducts: A duct through which the sperm pass in order to be transported from the testes to the outside of the male body. The duct does this by peristalsis using the muscles in the duct walls because sperm are not yet mobile at this stage. It also facilitates the maturation of sperm cells (the sperm cells mature inside the duct).
  • Prostate gland: Secretes prostate fluid (one of the fluids that make up semen). The mixture of sperm and the fluid in which it is transported is called semen. The muscles of the prostate gland also help push the seminal fluid through the urethra and into the female reproductive organ during ejaculation.
  • Urethra: A tube that carries urine or semen. It continues from the sperm duct.
  • Penis: The primary male sex organ – used in sexual intercourse. Ejaculates semen and is also used to discharge urine. When a male is aroused, the blood vessels in the penis expand, allowing more blood to flow into the penis. Blood flow out of the penis is restricted, and thus the penis becomes hard. This is important for sexual intercourse to happen, or else the penis cannot penetrate the vaginal opening.
  1. Compare male and female gametes in terms of size, numbers and mobility.

 

  1. Identify on diagrams of the female reproductive system: the ovaries, oviducts, uterus, cervix and vagina, and state the functions of these parts.

 

Functions:

  • Ovaries: produce oocytes (undeveloped ovum’s) for fertilisation, and also produce and secrete the reproductive hormones oestrogen and progesterone. These two hormones help regulate the menstrual cycle.
  • Oviducts (also known as Fallopian, Uterine or Ovarian tubes): allows the transmission of the ovulated oocyte from an ovary to the uterus. Also provides the necessary environment for fertilisation (the fusion of the sperm and egg nuclei), and the maturation of the oocyte into an ovum.
  • Uterus: nurtures the fertilised ovum that develops into a foetus and holds the baby until it is mature enough for birth. The fertilized ovum is implanted into the endometrium and it receives nourishment from the blood vessels developed for this purpose.
  • Cervix: allows the flow of menstrual blood from the uterus into the vagina, and directs the sperm into the uterus during sexual intercourse. The opening of the cervix is usually very narrow but widens to about 10cm during labour. A loose cervical opening can often lead to miscarriages.
  • Vagina: Receives the penis during sexual intercourse and serves as the conduit for menstrual blood from the uterus. During labour, the baby passes out through the vagina
  1. Describe the menstrual cycle in terms of changes in the uterus and ovaries.

The menstrual cycle is a hormone-regulated cycle.  On average, it lasts 28 – 35 days. It should also be noted that inside each ovary contains numerous follicle.

A follicle is a fluid-filled sac that contains an oocyte (an immature egg).

 

There are two main phases of each menstrual cycle: The follicular phase – which lasts approximately 2 weeks, and the luteal phase, which lasts another two weeks.

Menstruation marks the beginning of each cycle, and thus, the first part of the follicular phase. This is when the endometrium lining sheds. If you’re a girl who’s hit puberty, you’ll know that this is the messiest part.

Washing out blood stains is absolute torture, and don’t even get me started on the cramps.

You don’t need to know this, but those cramps are caused by muscle contractions – similar to the ones you experience during labour, but usually much less intense.

How long the menstrual phase lasts varies from girl to girl – it spans 3 to 9 days, depending on the person.

During menstruation, follicles start to develop, and along with them, the oocytes they carry. The Endometrium lining starts getting repaired. The dominant follicle – i.e. the one that will release the egg in ovulation, will only finish developing after the end of menstruation.

Next is Ovulation. This marks the transition from the follicular phase to the luteal phase. In ovulation, the dominant follicle bursts and turns into a corpus luteum, and the oocyte is released into the oviduct. The luteal phase has begun.

The hormones produced by the corpus luteum ensure that the thickness of the endometrium is maintained.

The egg is moved slowly down the oviduct by fluids and the muscles in the oviduct walls.

If the egg is fertilised while in the oviduct, it will form a zygote, which then forms an embryo, a foetus, and finally, a baby. The uterus wall (endometrium) thickness will be maintained until birth.

If the egg is not fertilised, it will die in the fallopian tube and dissolve. The hormones maintaining the endometrium stop being produced and the endometrium starts to break down.

This causes menstruation and marks the start of the next cycle.

  1. Describe fertilisation in terms of the joining of the nuclei of the male gamete (sperm) and the female gamete (egg).

During sexual intercourse, an erect penis is inserted into the vagina.

Semen is then ejaculated, and millions of sperm are released into the neck of the vagina. Out of these millions, numerous sperm will find the egg – as shown in the animated picture above the sperm vs. ovum table – but only one will penetrate.

A fertilisation membrane is secreted around the egg once one sperm penetrates, preventing the penetration of numerous sperm.

Finally, the sperm nucleus and egg nucleus fuse to form a zygote. This is fertilisation.

  1. Outline the early development of the zygote simply in terms of the formation of a ball of cells that becomes implanted in the wall of the uterus.

First, ovulation – a mature follicle bursts, releasing an egg into the oviduct.

While in the oviduct, fertilisation occurs and the oocyte develops into an ovum. The fertilisation causes the formation of the zygote. The zygote then undergoes cellular division.

It divides into two cells, then four, then eight and so on.

After a few hours, a ball is formed.

The cells in the ball, which is now called an embryo, carry on dividing as it travels down the oviduct.

Once the embryo reaches the uterus, it sinks into the soft lining of the uterus – this is implantation. By this stage, the placenta will have begun to form.

  1. Indicate the functions of the amniotic sac and amniotic fluid.

This is a picture of the amniotic sac and fluid. The amniotic sac is the thin membrane (which is formed from cells of the embryo). You can also see the human embryo, at 7-8 weeks.

The white cord extending from approximately the baby’s belly button towards the red mass is the umbilical cord. The red mass is a portion of the placenta. The fluid that the embryo is suspended in is called the amniotic fluid.

Just to give you guys an idea of the positioning of the amniotic sac, I’ve included this diagram. Note that in normal pregnancy, foetuses and babies will change position several times but should always be upside down for the last stages and during birth.

The function of the amniotic sac is enclosing the amniotic fluid and preventing the entry of bacteria.

The function of amniotic fluid is supporting the foetus and protecting it from physical damage. It also absorbs excretory materials (urine) release by the foetus.

  1. Describe the function of the placenta and umbilical cord in relation to the exchange of dissolved nutrients, gases and excretory products (no structural details are required).

 

The placenta (which carries the mother’s blood) and the foetal blood vessels that branch out into capillaries close to the villi walls bring the foetal blood and maternal blood very close but don’t allow them to mix.

This is very important because the foetus may have a different blood group to the mother, and mixing blood groups will cause blood clotting. Also, the mother’s blood pressure is much higher, and this could damage the foetal organs.

Blood from the foetus is passed through the umbilical cord in the umbilical artery (red) to the placenta and returned in the umbilical vein (blue), which also passes through the umbilical cord.

The proximity of the maternal and foetal blood allow substances from one’s blood to diffuse across into the other’s blood.

  1. Describe the advantages and disadvantages of breastfeeding compared with bottle-feeding using formula milk.

Advantages of breastfeeding:

  • There are antibodies present in breast milk. This protects the baby against infection.
  • Nutrients are present in breast milk in the correct proportions.
  • There are no additives and preservatives in breast milk.
  • Breastfeeding builds a bond between mother and baby.
  • Breast milk does not require sterilisation because there is no bacteria present that could cause intestinal disease.
  • Formula milk is much more expensive than breast milk – which costs nothing.

Advantages of bottle feeding

  • Someone else can feed the mother’s baby.
  • This can also help the father bond with the baby.
  • Some diseases, such as HIV/ AIDS won’t be able to be spread to the baby from the infected mother.

The disadvantages of bottle-feeding are basically all the negative of the advantages of breastfeeding (it doesn’t contain antibiotics, there are additives and preservatives, etc.)

The disadvantages of breastfeeding are the negative of the advantages of bottle feeding (no one else can feed the baby, the father can’t bond, etc.)

  1. Describe the methods of transmission of human immunodeficiency virus (HIV), and the ways in which HIV/ AIDS can be prevented from spreading.

Note that HIV is primarily spread through the transfer of body fluids.

Transmission:

  • From infected mother to foetus across placenta
  • Feeding a baby milk from an infected mother
  • Unprotected sexual intercourse with an infected person
  • Transfusion with unscreened blood
  • Use of unsterilized surgical instruments
  • Sharing hypodermic needles when taking drugs

Methods of preventing the spread of HIV/ AID:

  • Abstinence from sex
  • Using formula milk to feed the baby when the mother is infected
  • Having only one sexual partner
  • Screening blood used for transfusions
  • Use of sterilised surgical instruments
  • Use of sterilised needles for drug injections
  1. Outline how HIV affects the immune system in a person with HIV/ AIDS.

There is a certain type of white blood cell called lymphocytes present in the bloodstream. Thes produce antibodies.

The HIV virus attacks a certain type of lymphocyte, so these antibodies are no longer produced. The immune system is weakened, and thus the person develops AIDS (Acquired Immune Deficiency Syndrome). This makes the person become more vulnerable to infections such as pneumonia, tuberculosis, etc. These diseases that arise because of this person’s weakened immune system are called ‘opportunistic diseases’.

Someone with AIDS usually dies of a collection of opportunistic diseases.

 

 

Notes submitted by Sarah.

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