Capillaries are the smallest vessels in the body and have a diameter of about 7 micrometers. They are so small that a red blood cell (erythrocyte) can usually only pass through under its own deformation. These smallest tubes consist of only one cell, which makes up the complete vessel wall. On the outside of the vessel wall there are often so-called pericytes, which surround the vessel wall, can change its width by contraction and give the capillary additional stability.
Types of arteries
Arteries can be divided into different types both functionally and histologically. Functionally, we distinguish between endarteries, which are the only arterial vessels that supply a certain area with oxygen-rich blood. If the blood flow is insufficient, the tissue may be undersupplied.
Collateral arteries, which run parallel to other arteries and thus supply a certain area. If one of the two vessels is displaced here, the other, parallel running artery takes over its task. Collateral arteries, which are contracted by strong muscles in the arterial wall and thus can stop the blood flow in a certain area.
A good example is the erectile tissue of the penis. Histologically, a distinction is made above all between the elastic type and the muscular type. Arteries of the elastic type have more elastic fibers in their wall.
They are mainly found near the heart, where a large volume of blood has to be absorbed by the vessels in a short time. The aorta, for example, briefly inflates with blood after the expulsion phase of the heart and conveys this blood with continuous pressure over a longer period of time. Arteries of the muscular type have a muscular layer in their wall which can contract. This is used to regulate blood pressure. Muscular arteries are mainly found far from the heart, for example in the arms, legs or skin, where regulation of blood flow is useful (e.g. when the temperature changes).
Major arteries of the human body:
The arteria vertebralis has its origin in the arteria subclavia, which runs from the middle of the body to the shoulder behind the collarbone. The arteria vertebralis then runs laterally along the cervical spine in pairs as arteria vertebralis dextra (right) and arteria vertebralis sinistra (left). It runs in the transverse foramina, which can be described as small holes in the transverse processes of the vertebral bodies.
Here, osteophytes (bony outgrowths) can develop, which can lead to fainting if the arteries become constricted. Then the two vertebral arteries together with the spinal cord pass through the foramen magnum, a large opening on the underside of the skull bone. Here the arteria spinalis anterior is then delivered.
The two branches of the arteria vertebralis finally unite to form the arteria basilaris, which supplies the brain stem arterially via several small branches. The arteria femoralis (femoral artery) is the largest artery on the thigh. It is a continuation of the external iliac artery below the groin.
At this point, below the inguinal ligament, the pulse of the femoral artery can also be felt. In addition, this section is often used for arterial accesses, for example for contrast imaging of the coronary vessels. Important branches of the arteria femoralis are the arteria epigastrica superficialis, A. circumflexa ilium superficialis, A. profunda femoris (which supplies large parts of the thigh and hip as a strong side branch), Aa.
Pudendae externae (usually two) and A. descendens genus. In its course, the femoral artery then orients itself to the sartorius muscle, which functions as the leading muscle. The artery then runs within the adductor canal (the canal between the adductor muscles) on the inside of the thigh.
There it emerges just above the hollow of the knee, at the adductor hiatus (adductor slit). Finally, it is continued as the popliteal artery. The carotid artery is a strong artery that runs along both sides of the neck and is responsible for the arterial supply of the neck and head.
It originates on the left side directly from the aortic arch. On the right side it originates from the brachiocephalic trunk. Then the arteria carotis communis runs inside the vagina carotica, a sheath of connective tissue.
The pulse can be easily detected here at the artery by palpation at the level of the larynx and to the side of the larynx. For this reason the arteria carotis communis is also colloquially called carotid artery. The arteria carotis communis is then divided into two further arteries, the arteria carotis externa and the arteria carotis interna.
At the branching you find the so-called Glomus caroticum, which registers the oxygen and carbon dioxide pressure in the blood. It also registers the pH value, i.e. the acidity level of the blood. In addition, the sinus caroticus, which registers the blood pressure, is located at the junction of the arteria carotis communis.
With the information collected here, the body can react to fluctuations and regulate the various parameters. Finally, the external carotid artery gives off several branches to the face, larynx, throat and thyroid gland. The internal carotid artery penetrates the skull bone and is involved in the arterial supply to the eye and brain.
For this reason, a stenosis (narrowing) of the internal carotid artery is very risky. If the flow of blood is too low, the brain is undersupplied. If the constriction is only on one side, it can usually be compensated for by the other side.
The pulsating artery is known in medical terminology as the radial artery because it runs along the radius (radius). The radial artery originates from the brachial artery (upper arm artery). It then runs along the inside of the forearm, where the thumb points.
The radial artery runs along the radius and the brachioradialis muscle. This can be recognized by bending the hand towards the thumb. The radial artery is called the pulsating artery because the pulse can be optimally felt just before the wrist.
In this case, one walks from the underside of the ball of the thumb down the inside of the forearm by about 3 cm and palpates with the index fingers between the central tendons and the lateral bone. Shortly before the wrist, the radial artery releases the ramus palmaris superficialis (superficial palm arch). This is a small artery that joins with the arteria ulnaris and supplies the palm of the hand.
The remaining part of the radial artery moves to the back of the hand in front of the ball of the thumb and supplies the thumb and one side of the index finger with oxygen-rich blood. The radial artery then ends in the so-called Arcus palmaris profundus (deep palmar arch), which also short-circuits with the ulnar artery. Thus the arterial supply of the hand takes place from two sides and is thus secured.
The coronary arteries, also called coronary arteries or Arteria coronaria (Lat. Coronarius “crown-shaped”), are the so-called “Vasa privata” (own vessels) of the heart. They serve exclusively for the arterial supply of the heart and are therefore of immense importance.
In doing so, they pull from the outside of the muscle as small branches into the muscle. There are two coronary arteries, the arteria coronaria sinistra (left coronary artery) and the arteria coronaria dextra (right coronary artery). They are branches of the ascending part of the aorta, i.e. they branch off immediately after the exit of the heart.
The arteria coronaria sinistra is divided into a ramus interventricularis anterior (RIVA) and a ramus circumflexus (RCX). The ramus interventricularis anterior pulls as a branch of the left coronary artery to the apex of the heart. The circumflex ramus pulls down on the left side of the heart and supplies its underside.
The anatomy here often varies from person to person, but the described course is true in about 75% of cases. The right coronary artery curves backwards and downwards on the right side of the heart. Here it supplies, for example, the right atrium, the sinus node and the AV node, the clocks of the heartbeat.
If the right coronary artery is blocked, there is acute danger to life because the heart no longer receives impulses and therefore no longer beats. The arteria poplitea (Lat. Poples “popliteal artery”) is the continuation of the arteria femoralis (femoral artery).
It begins with the exit of the femoral artery from the hiatus adductorius (adductor slit) above the hollow of the knee. First, at the upper edge of the knee, the arteria superior medialis genus (upper central knee artery) and the arteria superior leteralis genus (upper lateral knee artery) are delivered to the inside and outside of the knee. The popliteal artery then moves into the hollow of the knee.
Here the pulse of the artery is easily palpable, as it is hardly covered by other structures. On the other hand, the artery here is also very susceptible to injury, which can lead to high blood loss. In the hollow of the knee, the popliteal artery delivers the arteria media genus (middle knee artery), which supplies the cruciate ligaments.
The popliteal artery then continues to run out of the popliteal fossa towards the lower leg and releases two more branches, the sural artery (Lat. Sura “calf”). These supply the gastrocnemius muscle, a strong two-headed calf muscle. Finally, below the hollow of the knee, the popliteal artery divides into the anterior tibial artery and the posterior tibial artery.