Three different arteries are conventionally known as the carotid artery. The first is the large common carotid artery and the two arteries that emerge from it, the internal carotid artery and the external carotid artery.
Common carotid artery
The arteria carotis communis, also known as “carotid artery” or carotid artery, is the common head artery. Since it runs deep in the neck and accompanies the oesophagus and windpipe from the chest towards the head, it is also called the carotid artery. Its pulse is easily palpable in the neck.
It runs in pairs on both sides of the neck and originates on the right side from the brachiocephalic trunk and on the left side mostly directly from the aortic arch. In humans it divides into an external and an internal artery in the “carotid bifurcation”. The height of the carotid bifurcation varies from person to person and can lie between the second and sixth cervical vertebrae.
In most people it is located at the level of the fourth cervical vertebra. The carotid sinus is located at the exit of the internal carotid artery. This is equipped with pressure receptors (baroreceptors) and monitors the blood pressure in the arterial system. From here, the information about the pressure is transmitted to the brain and the heart. In addition, certain chemoreceptors in this area measure the content of carbon dioxide (CO2), oxygen and the pH value in the blood.
Internal carotid artery
The internal carotid artery, also called the internal carotid artery, is one of the vessels that supply the human brain. It also supplies the human eye with oxygenated blood via the ophthalmic artery. The course of the internal carotid artery is divided into four parts.
The neck part (pars cervicalis) extends from its exit from the large arteria carotis communis to its entry into the base of the skull. At the beginning, it is usually located behind the smaller external carotid artery (Arteria carotis externa) and then continues towards the middle, where it reaches the base of the skull. In this part of the neck, the internal carotid artery does not give off any branches.
The neck part is followed by the petrous bone part (pars petrosa). It runs there in the petrous bone and initially continues upwards, before making an arc in the front wall of the tympanic cavity and then running towards the sphenoid bone body. This bow is also called the carotid knee.
The pars petrosa gives off various branches to the tympanic cavity (Arteriae caroticotympanicae) and to the canalis pterygoideus (Arteria canalis pterygoidea). In the area of the inner opening of the carotid canal, the arteria carotis interna is often only covered by the hard meninges (dura mater). Directly on the inside of the base of the skull, the carotid artery runs through the sinus cavernosus, which is why this part is called the pars cavernosus.
In this area, the artery makes another S-shaped arc from the bottom back to the top front. This is called the carotid siphon. In this part, the carotid gives off branches to the neurohypophysis (Arteria hypophysialis inferior), the trigeminal ganglion (Rami ganglionares trigeminales), the hard meninges (Rami meningeus) and the sinus cavernosus (Rami sinus cavernosi).
After breaking through the hard meninges, the carotid changes into its “brain part” (pars cerebralis). This part lies in the subarachnoid space at the base of the brain. In this section, it runs from the bottom back to the top front and immediately afterwards passes its branch to the eye (ophthalmic artery).
Usually, this part also gives rise to the Arteria communicans posterior, which is part of the Circulus arteriosus cerebri and connects the anterior and posterior current region in the brain. After delivery of the arteria choroidea anterior, which supplies various brain structures, the arteria carotis interna divides into the anterior (arteria cerebri anterior) and the middle (arteria cerebri media) cerebral artery. These two arteries supply a large part of the cerebrum.
The internal carotid artery can be divided into 4 sections: Pars cervicalis: It begins at the carotid sinus and continues through the carotid canal to the base of the skull. Pars petrosa (petrous bone): It runs up through the temporal bone and into the tympanic cavity, where it makes an arch forward, also known as the carotid knee. It lies in close proximity to the venous plexus.
Pars cavernosa: It runs along the inside of the skull base and through the sinus cavernosus. Pars cerebralis: It runs in the subarachnoid space at the base of the brain from back to front. There is also a second division according to clinical criteria.
Here, the pars cerebralis and cavernosa are additionally divided into segments C1-5. The arteria carotis externa cannot be divided into segments. – Pars cervicalis (neck part): It begins at the sinus caroticus and moves through the carotid channel into the base of the skull.
- Pars petrosa (petrous bone): It passes through the temporal bone and up into the tympanic cavity, where it makes an arch forward, also known as the carotid knee. It lies in close proximity to the venous plexus. – Pars cavernosa: It runs along the inside of the skull base and through the sinus cavernosus.
- Pars cerebralis: It runs in the subarachnoid space at the base of the brain from back to front. The A. carotis interna has 4 sections:
- The cervical pars doesn’t branch out. – The pars petrosa gives off the ramus caroticotympanicus (tympanic cavity) and the A. canalis pterygoidei (canal).
- The pars cavernosa is divided into 6 branches: the R. tentorii basalis, the R. tentorii marginalis, the R. meningeus (meninges), the R. sinus cavernosi (sinus), the A. hypophysialis inferior (pituitary) and the R. ganglionis trigeminalis (trigeminal ganglion). – The pars cerebralis also has 7 branches. The R. clivi, the A. hypophysialis superior (pituitary gland), the A. ophthalmica (eye) and the A. choroidea anterior are classical arteries.
The Arteria communicans posterior, the A. cerebri media and the A. cerebri anterior, on the other hand, form parts of the Circulus arteriosus. This is a circular anastomosis that connects the flow areas of the Aa. carotis and the Aa.
vertebralis and is intended to create a certain balance in the event of reduced blood flow. The A. carotis interna supplies large parts of the brain (A. cerebri media and anterior, Aa. hypophysialis, A. choroidea anterior). Especially the front part and gives branches to the eye (A. ophthalmica), the trigeminal ganglion, the tympanic cavity, the nose and parts of the forehead. Together with the A. vertebralis it forms the Circulus arteriosus.