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15.1.6Reproduction

Sexually Transmitted Infections — Cambridge IGCSE Co-ordinated Sciences 0654 - Biology Revision Notes & Topical Questions

5 min read 8 parts Lesson 7 of 7

📚 Cambridge IGCSE Co-ordinated Sciences 0654 - Biology Hub / Topical Revision
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Part 1 of 6Sexually transmitted infections

STI
STI an infection transmitted through sexual contact.
  • Unprotected intercourse can pass pathogens through the exchange of body fluids.
HIV
  • HIV the human immunodeficiency virus is a pathogen that causes an STI.
AIDS
  • HIV infection may lead to acquired immunodeficiency syndrome.

Part 2 of 6Other STIs

InfectionPathogenTreatment
ChlamydiaBacteriumAntibiotics
GonorrhoeaBacteriumAntibiotics
Genital herpesVirusAntiviral drugs relieve symptoms
HIVVirusAntiretroviral drugs control it; no cure

Part 3 of 6Transmission of HIV

Sexual intercourse
  • Sexual intercourse through exchange of body fluids.
Sharing needles
  • Sharing needles with an infected person.
Blood transfusion
  • Blood transfusion with infected blood.
Mother to baby
  • Mother to baby through the placenta, and in breast milk.

Part 4 of 6How HIV affects the immune system

1
HIV enters the body and often causes mild flu-like symptoms.
2
The symptoms pass and the person may not know they are infected.
3
HIV infects a type of lymphocyte and uses its machinery to multiply.
4
HIV avoids recognition by repeatedly changing its protein coat.
5
The number of lymphocytes and the antibodies they make fall.
6
The immune system weakens and opportunistic infections occur, leading to AIDS.

Part 5 of 6Controlling the spread

MethodHow it helps
Limit the number of sexual partnersReduces exposure
Use condomsBarrier to body fluids; also prevent pregnancy
Get tested after unprotected sexAllows early treatment
Screen blood donationsRemoves infected blood
Do not share needlesStops blood transfer
Education programmesRaise awareness

Part 6 of 6More from the specification

1
Pathogen invasion of mucosal epithelial cells
  • Pathogen invasion of mucosal epithelial cells sexually transmitted bacteria and viruses adhere to and invade genital epithelial cells, triggering inflammatory responses.
2
Pituitary gland
  • The master gland whose hormones control other glands.
3
Structural adaptation
  • An adaptation of body form.
4
Pathogenesis and Impact of Human Immunodeficiency Virus (HIV) — HIV infects and progressively destroys CD4+ helper T lymphocytes, impairing the adaptive immune system and eventually leading to Acquired Immune Deficiency Syndrome (AIDS).
5
Transmission Routes of Sexually Transmitted Infections
  • Pathogens causing STIs are transmitted through unprotected sexual intercourse, exposure to contaminated blood, needle sharing,
    • and vertically from mother to foetus during childbirth or breastfeeding.
    • (such as HIV, gonorrhea, and chlamydia)
6
Prevention and Management Strategies for STIs
  • Transmission rates are effectively minimized through the consistent use of barrier contraceptives (condoms), comprehensive public screening, prophylactic antiretroviral therapies,
    • and contact tracing.
7
Hormone
  • A chemical substance produced by a gland and carried by the blood that alters the activity of specific target organs.
8
Variation
  • Differences between individuals of the same species.
9
Germination
  • The start of growth of a seed.
10
Oestrogen
  • The main female sex hormone, made in the ovaries.
11
Progesterone
  • A hormone that maintains the uterus lining.
12
Asexual reproduction
  • Reproduction from one parent giving genetically identical offspring.
13
Menstrual cycle
  • A monthly series of changes in the female reproductive system controlled by hormones.
14
Genetically identical
  • Having the same alleles
15
Pollen
  • Grains made by plants, each type with a different shape.
16
Fertilisation
  • The fusion of the nuclei of a male and a female gamete.
17
Reproduction
  • The processes that make more of the same kind of organism.
18
Gamete
  • A haploid sex cell.
19
Uterus
  • The organ in which the foetus develops.
20
Pollination
  • Transfer of pollen from an anther to a stigma.

Key terms

TermMeaning
STIAn infection passed on by sexual contact.
HIVA virus that attacks lymphocytes of the immune system.
AIDSThe late stage of HIV infection when the immune system cannot fight infections.
LymphocyteA white blood cell of the immune system.
CondomA barrier that reduces the spread of STIs.
Antiretroviral drugA drug that controls HIV infection.

Avoid these mistakes

1
Saying HIV and AIDS are the same — HIV is the virus and AIDS is the late syndrome.
2
Saying antibiotics treat HIV — antibiotics do not affect viruses.
3
Saying HIV spreads by touch or hugging — it spreads by body fluids and blood.
4
Saying treatment cures HIV — antiretroviral drugs control it.

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