Functions of Part 2 (Placenta) : 1. It helps to transfer oxygen and nutrients from mothers blood to foetus by diffusion. 2. It acts as an organ of excretion i.e. transfer $\mathrm{CO}_2$ and other metabolic wastes from foetus to mother's blood by diffusion. 3. Placenta also acts as an endocrine gland and produces the female sex hormones like oesterogen and progesterone.