higher biology unit 2

• Sperm production


  Seminiferous tubules
• Testosterone production


  Interstitial cells
• Ovaries


  Contain immature ova, which is surrounded by a follicle that protects the developing ovum and secretes hormones
• Fertilisation


  Mature ova are released into the oviduct where they may be fertilised by sperm to form a zygote
• Identifying a woman's fertile period


  • Body temperature rises by around 0.5°C
  • Cervical mucus becomes thin and watery
• Drugs that stimulate ovulation


  Drugs which prevent the negative feedback of oestrogen on FSH secretion
• Artificial insemination


  Several samples of semen are collected when the male has a low sperm count
• ICSI


  Head of sperm drawn into a needle and injected directly into the egg to achieve fertilisation
• IVF


  1. Woman is given hormone treatment to stimulate multiple ovulation

  2. Eggs removed from ovaries

  3. Eggs mixed with sperm in a culture dish

  4. Fertilised eggs incubated until at least 8 cells have formed

  5. Fertilised eggs implanted into the uterus
• Antenatal screening


  Identifies the risk of a disorder so that further tests and a prenatal diagnosis can be offered
• Dating scans


  Determine pregnancy stage and due date (8-14 weeks)
• Anomaly scans


  May detect serious physical abnormalities (18-20 weeks)
• Amniocentesis


  Small amount of amniotic fluid is withdrawn, cells cultured to produce a karyotype
• CVS


  Takes a sample of placental cells, cells are cultured and used for Karyotyping
• Benefits and risks of amniocentesis and CVS


  • Amniocentesis carries a slight risk of miscarriage, CVS has a much higher risk of miscarriage
  • CVS can be carried out earlier than amniocentesis
• Autosomal Recessive Inheritance


  Expressed relatively rarely in the offspring, affects males and females equally, may skip generations through carriers
• Autosomal Recessive Inheritance


  • Cystic Fibrosis (CF)
• Autosomal Dominant Inheritance


  Every sufferer has an affected parent, an individual cannot carry the condition without being affected, males and females equally affected
• Autosomal Dominant Inheritance

  • Huntington's Disease
• Incomplete Dominance


  Fully expressed form of the condition is rare, partly expressed form is more common
• Sex-linked Recessive Inheritance


  Males more commonly affected than females, male offspring inherit from mother, fathers cannot pass onto their sons, females can only be affected if the father has the condition and the mother is a carrier
• PKU

  A substitution mutation means that the enzyme which converts phenylalanine to tyrosine is non-functional
• Cardiovascular system


  Contains heart, blood, blood vessels
• Artery


  • Carries blood away from heart, thicker outer layer, middle layer of smooth muscle and elastic fibres
• Capillary

  • Elastic walls allow artery to recoil after each contraction, allows exchange of substances between blood and the tissues through their thin walls
• Vein

  • Carries blood into the heart, much thinner outer layer than artery, presence of valves to prevent backflow of blood
• Blood flow control


  Muscles surrounding arteries can contract causing vasoconstriction or relax causing vasodilation
• Tissue fluid vs blood plasma

  Tissue fluid is similar, just excluding proteins as they are too large to be filtered through the capillary walls
• Pressure filtration


  Causes plasma to pass through capillary walls
• Tissue fluid function


  Supplies cells with food, oxygen and other substances
• Cardiac output equation


  Cardiac Output = Heart Rate x Stroke Volume
• Cardiac cycle


  Refers to the pattern of contraction (systole) and relaxation (diastole) during one complete heart beat
• Heart sounds


  Caused by the opening and closing of AV and SL valves
• SAN/pacemaker


  Located in the wall of the right atrium, and sets the rate at which the heart contracts
• Obesity


  Characterised by excess body fat in relation to lean body tissue such as muscle
• Obesity risks