Dorothy FarrarCapillary
Capillaries are the smallest blood vessels and blood transport routes in the human body. The synonym is hair vessels, because each of these small transport routes is anatomically as fine as a hair.
Definition
Technical jargon describes capillaries as elongated cavities or tubes. Inside these cavities or tubes, the capillary forces are used. The cell layer is so thin that it enables an exchange of substances between tissue and blood .
During this exchange, oxygen flows out of the red blood cells through the walls of the vessels. This process also ensures the outflow of excess pollutants and carbon dioxide. Main capillaries regulate body temperature by causing blood on the body surface to cool when body temperature rises.
Anatomy
Capillaries form the smallest blood vessels in the human body and are involved in microcirculation. The inner wall layer is only the size of a cell. New capillaries are created during the embryonic phase by vasculogenesis, with which new blood vessels are formed. New endothelial cells form and expand into vascular channels.
With angiogenesis, new capillaries are formed by splitting and sprouting from previously formed blood vessels. The continuous capillaries are found in skeletal muscle, the CNS, heart , and lungs . This type of capillary has a closed endothelium. This means that the innermost layer of the cell is closed. Only small molecules penetrate through the vessel wall to the outside.
The second group includes the fenestrated (fenestrated) capillaries. Their designation indicates pores in the endothelium that are approximately 60 to 80 millimeters in size. At the relevant points, the lumen is only separated from its surroundings by the thin basement membrane. The pores allow the penetration of the smallest proteins . These fenestrated blood vessels are found in the endocrine glands, gastrointestinal tract and kidneys with the largest pores.
Sinusoids are dilated capillaries that are porous in both the Basel membrane and the endothelial layer. This type of pore is much larger. It has a diameter of 40 µm and allows larger proteins and blood cells to pass through. Sinusoids are found in the spleen , liver , lymph nodes , renal medulla , and bone marrow .
Function
The capillaries form the interface between the venous and the arterial system. In addition to the arteries and veins, the blood capillaries are one of the three types of vessels that ensure that the human organism runs smoothly. The capillaries act as intermediaries between the arteries and the veins.
The arteries drain blood away from the heart. They narrow to form arterioles and subsequently to capillaries with a large number of branches (capillary network). After the blood has taken this first stage, it flows back to the heart via the capillaries through the dilated venules via the veins.
Hair vessels do not function independently, but in the form of an intertwined network as a capillary bed. This can contain two different vessels. The real capillaries ensure the exchange between the cells and ensure blood circulation. The second short vessel, the vascular shunt, directly connects an arteriole to a vein. These small vessels have a diameter of between 5 and 10 µm and are 0.5 millimeters long.
With a diameter of 7 µm, the erythrocytes (red blood cells) are sometimes larger than the capillaries and have to adapt to their size in order to be able to escape. They ensure a regulated exchange of oxygen, nutrients and metabolic end products between the tissue and the bloodstream. They supply the tissue with nutrients, absorb excess pollutants and transport them away.
The human body has different types of tissue that have different levels of metabolic activity and require more or less oxygen depending on these activities. For this reason, the various types of tissue are provided with a more or less developed capillary density, depending on the requirements placed on them.
The skeletal muscles, the heart and the brain are the areas of the human body that are subject to the highest demands and have a high level of metabolic activity. For this reason, these areas are densely occupied with a large number of capillaries. Less metabolically active tissues are, for example, the cornea , the eye lens and the cartilage tissue. They therefore have few or no capillaries.
Diseases
- Capillary leak syndrome
Capillaries are sensitive to any form of injury. Bruises are often caused by impact injuries. As a result of the impact, blood leaks out and flows into the tissues. This leads to the externally visible bruise with the bluish discoloration.
Responsible for this discoloration is the hemoglobin in the drained blood, which no longer contains any oxygen. A few days later, the bruise turns green and then yellow. These colors signal the different phases of the healing process that heralds the repair of the damaged capillary. Bilirubin, a breakdown product of hemoglobin, is responsible for this discoloration.
Noticeable but harmless symptoms are reddening of the face in the area of the cheeks and nose. They are caused by minimal capillary injuries. The vessels dilate or constrict too quickly, leading to ruptures in the vessel wall.
A serious condition is capillary leak syndrome, in which unexplained changes cause blood plasma to leak through the capillary walls and into surrounding tissues or body cavities. If this process is not stopped in time, it leads to a drop in blood pressure, organ failure and thus inevitable death.
Hello and welcome to my Health Guide & Encyclopedia! My name is Dorothy Farrar, and I'm the founder and main author of this platform.
My passion for health and wellness started at a young age when I became interested in the connection between the food we eat and the way we feel. This fascination led me to study nutrition and dietetics in college, where I learned about the importance of a balanced diet and the impact of various nutrients on the body.