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for this image give 3 mark question for spotting

Reading File
The image clearly shows a placenta specimen (labelled) in a glass container - with the villous tissue (fluffy, shaggy fetal surface) and the umbilical cord visible.
Here are 3-mark spotting questions for this specimen:

Spotting: Placenta

Q1. Identify this specimen and describe its surfaces. (3 marks)
Answer:
  • Identification: Placenta (1 mark)
  • Fetal surface (Chorionic plate): Smooth, shiny, covered by amnion; umbilical cord attaches at the centre (usually); fetal vessels (chorionic vessels) radiate from the cord insertion (1 mark)
  • Maternal surface (Basal plate): Dull, rough, divided into 15-20 cotyledons by septa arising from the decidua basalis (1 mark)
Q2. Name the specimen. What is the type of placenta seen in humans and mention its components? (3 marks)
Answer:
  • Specimen: Placenta (0.5 mark)
  • Type: Haemochorial placenta - maternal blood directly bathes the chorionic villi (0.5 mark)
  • Components: (2 marks)
    1. Fetal part - Chorion frondosum (villous chorion) with stem villi, branching villi
    2. Maternal part - Decidua basalis
    3. Umbilical cord - containing 2 umbilical arteries and 1 umbilical vein (AVA rule: "2 arteries, 1 vein")
Q3. Identify this specimen. Enumerate the functions of this organ. (3 marks)
Answer:
  • Identification: Placenta (1 mark)
  • Functions (any 4 = 2 marks):
    1. Nutrition - transfer of glucose, amino acids, fatty acids to the fetus
    2. Respiration - O2/CO2 exchange (acts as fetal "lung")
    3. Excretion - removal of fetal waste products (urea, bilirubin)
    4. Endocrine - secretes hCG, hPL (human placental lactogen), progesterone, oestrogens
    5. Immunological - passive transfer of maternal IgG antibodies to fetus
    6. Barrier function - prevents passage of most bacteria (though viruses and some drugs cross)
Tips for spotting viva:
  • The shaggy/fluffy appearance seen in the image = chorionic villi (fetal side)
  • The cord visible = umbilical cord (note: 2 arteries carry deoxygenated blood, 1 vein carries oxygenated blood - opposite to systemic circulation)
  • In a full-term placenta: weight ~500g, diameter ~20cm, thickness ~2.5cm
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