D3.1.18 (HL)—Placenta role
The placenta exchanges materials between maternal and fetal blood, prevents blood mixing and secretes hormones that help maintain pregnancy in mammals.
- Syllabus
- First assessment 2025
- Objective
- D3.1.18
- Level
- HL
Exam analysis
Chance of appearing4%of analysed past papers
Latest appearanceMay 2023
Most common paperPaper1
Typical marks1–8
Common command terms
- Explain
- Identify
Recent exam appearances
May 2023Paper1 ["HL"] · TZ240[ 1 ]D3.1.18 (HL)—Placenta role
May 2017Paper1 ["HL"] · TZ140[ 1 ]D3.1.18 (HL)—Placenta role
November 2014Paper2 ["HL"] · TZ08(c)[ 8 ]D3.1.18 (HL)—Placenta role
May 2013Paper2 ["HL"] · TZ28(c)[ 8 ]D3.1.18 (HL)—Placenta role
Practice this objective
Coverage 2013–2023 · Updated 16 Jul 2026
Concept essentials
- Placental villi increase surface area for maternal-fetal exchange.
- Maternal and fetal blood flow close together but do not normally mix.
- The placenta secretes hormones that help maintain pregnancy.