CIRCULATION OF BLOOD TO THE HEAD
AND NECK
Arterial supply to
the head and neck are from the common carotid arteries and the vertebral
arteries,both are paired.
CAROTID ARTERIES :-
The right common
carotid artery arises from the brachiocephalic artery. The left common carotid
artery arises directly from the arch of the aorta. They pass upwards on either
side of trachea, have same distribution and relations in the neck. At the level
of the upper border of thyroid cartilage,they divide into
1.
External carotid artery.
2.
Internal carotid artery.
THE CAROTID SINUSES AND CAROTID
BODIES.
The carotid sinuses are small dilatations at the point of
bifurcation of the common carotid arteries.the walls of the sinuses are thin
and contain numerous specialized nerve endings of the glossopharyngeal nerve.
They act as ‘Baroreceptors’ stimulated by any change in the blood pressure in
the carotid sinuses. The carotid bodies are small groups of specialized cells,
lying in close association at the bifurcation of common carotid artery.
They are supplied by branches of glossopharyngeal nerve.
These specialized cells are stimulated by any change in
concentration of carbon dioxide and oxygen.these cells have connection to
respiratory centre in the medulla oblongata to adjust the respiratory
movements. They are also called chemo receptors.
EXTERNAL CAROTID ARTERY:
This artery supplies
the structures in the head and neck through these branches.
1.
The superior thyroid artery supplies the thyroid
gland.
2.
The lingual artery supplies the tongue and
tonsil.
3.
The facial artery supplies,face,muscles of the
face and sub mandibular gland. One can feel the facial artery at the base of
the mandibule.
4.
The occipital artery supplies the posterior part
of the scalp.
5.
The ascending pharyngeal artery supplies the
pharynx and prevertebral muscles.
6.
The posterior auricular artery supplies the
auricular muscles of the ear.
7.
The maxillary artery supplies the muscles of
mastication.the important branch is a middle meningeal artery which enters the
head and supplies the covering of the brain and skull.
8.
The superficial temporal artery passes over the
zygomatic arch in front of the ear, and supplies the frontal,temporal and
parietal parts of the scalp. The pulse may be felt on this artery in front the
ear.
THE INTERNAL CAROTID ARTERY:
It is the major
contributor to the circle of willis which supplies the greater part of the
brain. It ascends to the base of the brain through the carotid foramen. It also
supplies the eyes,forehead and nose.
THE CIRCULUS ARTERIOSUS (CIRCLE
OF WILLIS)
It is the arterial
anastomoses channel situated at the base of the brain in subarchnoid space to
supply the brain. It is formed by four arteries. The vertebral arteries unite
to form basilar artery. This artery runs on the anterior surface of the pons to
its upper margin,where it divides into the posterior cerebral arteries. Both
the right and left anterior and middle cerebral arteries they are connected by
posterior communicating arteries to complete the circle of willis. Its branches
are
2 Anterior cerebral
arteries
1 anterior
communicating artery
2 middle cerebral arteries
2 posterior communicating arteries
2 posterior cerebral arteries.
Branches of circle of
willis namely the basilar artery and vertebral arteries supply by the brain and
spinal cord.
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