What kind of blood does capillaries carry

This structure allows arteries to dilate as blood pumps through them. After the capillaries release oxygen and other substances from blood into body tissues, they feed the blood back toward the veins. First the blood enters microscopic vein branches called venules. The venules conduct the blood into the veins, which transport it back to the heart through the venae cavae.

Vein walls are thinner and less elastic than artery walls. The pressure pushing blood through them is not as great.

In fact, there are valves within the lumen of veins to prevent the backflow of blood. Capillaries are tiny vessels that branch out from arterioles to form networks around body cells. In the lungs, capillaries absorb oxygen from inhaled air into the bloodstream and release carbon dioxide for exhalation. Elsewhere in the body, oxygen and other nutrients diffuse from blood in the capillaries to the tissues they supply. The capillaries absorb carbon dioxide and other waste products from the tissues and then flow the deoxygenated blood into the veins.

The vena cava are also called the "central veins". Central venous catheters are inserted with the tip in or close to the superior of inferior vena cava.

Blood is pumped from the right side of the heart into the blood vessels of the lung. When blood enters the small capillaries of the lung called the pulmonary capillaries , fresh oxygen enters the blood and carbon dioxide is removed. This is called " gas exchange " or " respiration ". Because this is the exchange of gases between the atmosphere and the bloodstream, it is also called " external respiration ". When freshly oxygenated blood reaches the capillaries of the tissues, oxygen moves from the blood toward the tissues, and carbon dioxide moves from the tissues toward the blood.

This gas exchange that occur between the blood and the cells of the tissues and organs is called " internal respiration ". Blood vessels have a muscle layer that is able to relax or contract.

When we need to increase our blood pressure, the muscle layer contracts and makes the blood vessel diameter smaller. This is called "vasoconstriction". It is returned to the heart by the veins. The capillaries connect the two types of blood vessel arteries and veins. Molecules are exchanged between blood and cells across the capillary walls.

Arteries branch to become smaller arteries called arterioles , these arterioles branch to become capillaries. The capillaries connect the smallest branches of the arteries arterioles and the smallest branches of veins venules. Capillaries form extensive networks throughout the body so that all cells are near a capillary and the concentration gradients can be maintained for the delivery of substances and the removal of waste around cells.

Petechiae are small, round spots that appear on the skin. They happen when capillaries leak blood into the skin. But experts think it may be related to a substance in the blood that damages capillary walls. People with SCLS have recurring attacks during which their blood pressure drops very quickly. These attacks can be severe and require emergency medical attention. People with arteriovenous malformation syndrome AVM have an abnormal tangle of arteries and veins that are connected to each other without capillaries in between.

These tangles can occur anywhere in the body, but are most often found in the brain and spinal cord. This can cause lesions that interfere with blood flow and oxygen delivery.

These lesions may also cause bleeding into the surrounding tissue. However, in some cases, it can cause:. Treatment usually involves surgically removing or closing the AVM lesion. Medication can also help to manage symptoms, such as pain or headaches.

Microcephaly-capillary malformation syndrome is a rare genetic condition that starts before birth. People with this condition have smaller heads and brains. They also have widened capillaries that increase the flow of blood near the skin surface, which can cause pinkish red spots on the skin. Mutations to this gene can result in cells dying during development, affecting the entire development process.

Treatment for this condition can involve stimulation — particularly through sound and touch — bracing to maintain posture, and anticonvulsant medication therapy for management of seizures.

Capillaries are tiny blood vessels that play a big role in facilitating the exchange of various substances between your bloodstream and tissues. There are several types of capillaries, each with a slightly different structure and function. Your venous system is a network of veins that carry blood back to your heart from other organs.