CAIE A-Level Biology 8.1.4 Blood Vessel Recognition

Practise identifying arteries, veins and capillaries in micrographs from wall-to-lumen ratio, muscle, elastic tissue, valves, endothelium and red-cell arrangement.

Exam points

identify arteries from thick muscular elastic walls and relatively small regular lumens
identify veins from thinner walls, larger irregular lumens and possible valves
identify capillaries from a one-cell-thick endothelium and narrow red-cell passage

[Maximum number: 2]

Smooth muscle is a tissue composed of smooth muscle cells. The cells contain cytoplasm packed with proteins that are involved in contraction and relaxation.

Fig. 1.2 is a photomicrograph of smooth muscle tissue in the wall of the intestines. A capillary is visible in addition to smooth muscle cells.

Fig. 1.2

Outline the features that help to identify the blood vessel in Fig. 1.2 as a capillary.

any two from:

wall, of one layer/is one cell thick ;

I capillary is one cell thick

A thin wall / endothelial cells are a single layer

A endothelium is, a single layer (of cells) / one cell thick

idea that red blood cells transported in single file ;

idea that red blood cells diameter (approximately), as large / same, as capillary (lumen) ;

A if diameter (e.g. $7 \mu \mathrm{~m}$ ) stated as being similar to capillary size

idea of diameter of capillary narrower than smooth muscle cell ;

AVP ; e.g. no muscle and elastic layer

muscle fibres / elastic fibres / collagen, not present ref. to different shapes of red blood cell / red blood cell showing flexibility, to pass through (narrow) capillary

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8.1.4—Blood vessel recognition question 1