BLOOD VESSELS

BLOOD VESSELS

If we took all the blood vessels out of an average child and laid them out in one line, the line would stretch over 60,000  miles. An adult's would be closer to 100,000 miles long. There are three kinds of blood vessels: arteries, veins, and capillaries.



There are four main types of blood vessels:

1. Arteries

Arteries are elastic vessels that transport blood away from the heart. Pulmonary arteries carry blood from the heart to the lungs where oxygen is picked up by red blood cells. Systemic arteries deliver blood to the rest of the body.

2. Veins

Veins are elastic vessels that transport blood to the heart. Veins can be categorized into four main types: pulmonary, systemic, superficial, and deep veins.

3. Capillaries

Capillaries are extremely small vessels located within the tissues of the body that transport blood from the arteries to the veins. Fluid and gas exchange between capillaries and body tissues takes place at capillary beds.

4. Sinusoids

Sinusoids are extremely small vessels located within the liver, spleen, and bone marrow.



Function

Blood vessels function to transport blood. In general, arteries and arterioles transport oxygenated blood from the lungs to the body and its organs, and veins and venules transport deoxygenated blood from the body to the lungs. Blood vessels also circulate blood throughout the circulatory system Oxygen (bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood. In all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95–100%) with oxygen. In all veins apart from the pulmonary vein, the saturation of hemoglobin is about 75%. (The values are reversed in the pulmonary circulation.) In addition to carrying oxygen, blood also carries hormones, waste products and nutrients for cells of the body.

Blood vessels do not actively engage in the transport of blood (they have no appreciable peristalsis). Blood is propelled through arteries and arterioles through pressure generated by the heartbeat. Blood vessels also transport red blood cells which contain the oxygen necessary for daily activities. The amount of red blood cells present in your vessels has an effect on your health. Hematocrit tests can be performed to calculate the proportion of red blood cells in your blood. Higher proportions result in conditions such as dehydration or heart disease while lower proportions could lead to anemia and long-term blood loss.


Blood vessels also transport red blood cells which contain the oxygen necessary for daily activities. The amount of red blood cells present in your vessels has an effect on your health. Hematocrit tests can be performed to calculate the proportion of red blood cells in your blood. Higher proportions result in conditions such as dehydration or heart disease while lower proportions could lead to anemia and long-term blood loss.

Permeability of the endothelium is pivotal in the release of nutrients to the tissue. It is also increased in inflammation in response to histamine, prostaglandins and interleukins, which leads to most of the symptoms of inflammation (swelling, redness, warmth and pain).