Fig. 2.1 is a transmission electron micrograph of a section through a blood vessel. Fig. 2.2 is a graph showing how the blood pressure in the pulmonary artery and in the right ventricle changes during one cardiac cycle.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.

1. [3] (a) capillary; two from single celled wall / AW ; A thin wall ref. to wall composed only of one, squamous epithelial / endothelial, cell; ref. to lumen diameter approx 7 xm ; A 5–8m A ref. to similarity to dimension of red blood cell in direct contact with tissue fluid; if vein named, allow one mark for, thin wall (relative to lumen) or wide / AW, lumen (relative to wall thickness)
2. [1] (b)(i) 0.24 s / 0.25 s ;
3. [1] (b)(ii) 0.08 s / 0.09 s ; A range
4. [4] (b)(iii) four from similarity ref. to increases and decreases in pressure at same time; A description for part of the graph e.g.starts to rise at same point as RV, returns to minimum at same point as RV idea that events in cardiac cycle occur are coordinated; A described e.g. impulses pass up both ventricles at the same time, ventricles both contract at same time difference reaches higher, blood pressure / peak, (than RV); systolic pressure higher in LV (than RV) left ventricle pumps blood to (whole) body / RV only to lungs) overcome greater resistance / ora for RV walls of left ventricle, thicker / more muscular more force exerted by LV } any two ;;