Why are capillaries only one cell thick?

Related questions

• Why does the narrowing of the arteries decrease blood flow but increase blood pressure?
• People who smoke often have cold hands and feet. What might explain this condition in terms of...
• Is the vertebral artery a branch of the aortic arch?
• What conditions contribute to elevated blood levels of alkaline phosphatase?
• Are lymphocytes produced in the bone marrow and then migrate to the thymus gland and lymph nodes...
• What is heart disease? What is the primary cause of heart disease and what symptoms does it...
• How does blood flow back to the heart from the lower extremities, since it is fighting against gravity?
• In a heart transplant, if the vagus nerve is not re-transplanted, how is the heart rate kept in check?
• Is heart disease hereditary? Can a person who subscribes to a very healthy lifestyle suffer a...
• What is the difference between congestive heart failure and coronary artery disease?