Cerebral circulation

Definitions & Key takeaways

The cerebral circulation is responsible for delivering oxygen and nutrients to the brain and removing carbon dioxide and other waste products. To ensure an uninterrupted blood supply to the brain, cerebral circulation consists of anterior and posterior parts. These two circulations, together, form a network of vessels known as the arterial circle of Willis. The anterior circulation consists of the internal carotid arteries and branches, which are the middle and anterior cerebral arteries. The anterior communicating artery connects the two anterior cerebral arteries.

The posterior circulation comes from the two vertebral arteries, which merge into the basilar artery and split into posterior cerebral arteries. Posterior cerebral arteries give off the left and right posterior communicating arteries, which then merge with the internal carotid arteries. Venous blood drains into the dural sinuses, which empty into the jugular veins and return to the heart through the superior vena cava.

Chapters:

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Introduction0:00–0:46

With cerebral circulation, cerebral stands for "brain," and circulation, refers to “blood flow.” So, cerebral circulation is the movement of blood through the vessels that supply the brain and surrounding structures.
Our brain is responsible for complex functions such as thinking, feeling, memory, movement, vision, and speech. Therefore, some of the devastating effects of oxygen deprivation to the brain include strokes, seizures, coma, and even death.
As a result, the brain requires a very efficient cerebral circulation to provide oxygen and nutrients, and remove carbon dioxide and wastes.

Arterial Circulation0:46–1:52

Now, like any other organ in the body, the blood supply to the brain, originates from the aorta. Arising from the heart’s left ventricle, it goes on to form the aortic arch.
Here, the brachiocephalic artery, originates first. This branch gives off the right subclavian artery and the right common carotid artery.
Then a bit further along the aortic arch, the left common carotid artery arises, followed by the left subclavian artery.
The subclavian arteries give off right and left vertebral arteries, which ascend through the intervertebral feramina up to the brain.
Because the consequences of hypoxia to the brain are so devastating, the brain is safeguarded by having a dual circulation, an anterior circulation, originating from the carotids, and a posterior circulation, originating from the vertebral arteries.
The two circulations eventually meet up, creating what’s known as the circle of Willis. Alright, the anterior circulation starts in the neck, where the common carotid splits into the external and internal branches, The internal carotid arteries, passes through the carotid canal of the temporal bone of the skull and into the cranial cavity to supply the brain.

Anterior Circulation1:52–2:40

Once, it enters the cranial cavity, the internal carotid artery gives off branches. First are the middle cerebral arteries that supply blood to the temporal and parietal lobes.
Second are the anterior cerebral arteries, which provide to the midline portions of the frontal lobes and superior medial parietal lobes of the brain.
Both anterior cerebral arteries are connected through the anterior communicating artery, forming the anterior portion of the circle of willis.

Posterior Circulation2:40–3:50

The posterior circulation starts with the vertebral arteries,which head up towards the cranium through the transverse foramina of the cervical vertebrae and then through the foramen magnum into the cranial cavity.
First, the vertebral arteries give off a branch called the posterior inferior cerebellar artery, or PICA, which supplies the medulla and part of the cerebellum.
Then, at the base of the medulla, both vertebral arteries go on to unite into a single artery called the basilar artery..
As the basilar artery ascends, it first gives off the anterior inferior cerebellar artery, or AICA, which supplies the lateral pons and part of the cerebellum.
Then, the basilar artery sends small branches called pontine arteries to supply the mid-pons. Going up towards the midbrain, the basilar artery gives off the right and left posterior cerebral arteries, which supply the occipital lobe of the brain.
Both of these arteries give the left and right posterior communicating arteries, which merge with the internal carotid arteries, thereby closing the posterior portion of the Circle of Willis.

Venous circulation3:50–4:34

After blood passes through the brain, it returns to the systemic circulation through a series of small superficial veins that feed into dural sinuses, which are venous channels located between the two layers of dura mater - the endosteal layer and meningeal layer..
The superior sagittal sinus runs along the longitudinal fissure, where it absorbs cerebrospinal fluid from the meninges.
It drains to the confluence of sinuses, along with the straight sinus and occipital sinuses. Which then empties into the transverse sinuses.
The transverse sinuses drain to the sigmoid sinuses, which then drain to the jugular veins, ultimately returning to the heart.

Review4:34–5:43

Alright, as a quick recap, cerebral circulation is the movement of blood throughout the vessels that supply the brain and surrounding structures.
To safeguard the brain from hypoxia, the brain has a dual circulation, an anterior and posterior circulation, forming the circle of Willis.
The anterior circulation is made of the internal carotid arteries and their branches - the middle cerebral arteries and anterior cerebral arteries.
Both anterior cerebral arteries connected via the anterior communicating artery. The posterior circulation arises from the vertebral arteries which join to form the basilar artery..
The basilar artery goes up to the midbrain, where it gives off the posterior cerebral arteries, which in turn give off the left and right posterior communicating arteries.
The left and right posterior communicating arteries then merge with the internal carotid arteries. Blood returns from the brain to the systemic circulation through a series of venous channels called dural sinuses, which eventually empty into the jugular veins and back to the heart.