MICROANATOMY

Detailed explanation-1: -Most capillaries are only about 8 to 10 micrometers in diameter (a micrometer is 0.001 mm). They’re so tiny that red blood cells have to pass through in a single file line.

Detailed explanation-2: -Capillary walls are only one cell thick, allowing exchange of gases, nutrients, and wastes. Capillaries are so fine that red blood cells must line up single-file to go through them.

Detailed explanation-3: -Red blood cells squeeze through narrow capillaries in single file. Haemoglobin molecules inside red blood cells pick up and carry the oxygen. These oxygen-rich cells travel in the blood vessels from the lungs to the left side of the heart. The blood is then pumped around the body.

Detailed explanation-4: -Capillaries: Arteries and veins are connected by blood capillaries, microscopically small tubes which form a network, the capillary bed in different tissues. The blood capillaries are so small that red blood cells can only move in single file through it. The exchange of all substances takes place in these capillaries.

Detailed explanation-5: -Endothelial cells form a single cell layer that lines all blood vessels and regulates exchanges between the bloodstream and the surrounding tissues. Signals from endothelial cells organize the growth and development of connective tissue cells that form the surrounding layers of the blood-vessel wall.