Cerebral and Basilar Arteries: Anatomy and Venous System

Cerebral and Basilar Arteries

The carotid artery supplies 80% of the oxygen to the cerebral hemispheres. The two internal carotid arteries branch into the middle cerebral arteries, which provide 60% of the brain's oxygen supply. The anterior communicating artery connects the right and left middle cerebral arteries.

Two vertebral arteries (left and right) ascend along the spinal cord and merge at the base of the skull to form the basilar artery. This artery supplies the medulla, pons, and other brainstem structures.

Circle of Willis

1. Frontal lobes
2. Temporal lobes
3. Middle cerebral artery (right and left)
4. Anterior cerebral artery
5. Posterior cerebral artery
6. Basilar artery
7. Vertebral arteries (right and left)
8. Spinal cord
9. Internal carotid artery
10. Anterior communicating artery (anastomosis)

The middle cerebral artery is the most crucial, supplying 60% of the brain and areas responsible for movement, intellect, and other functions. The basilar artery supplies areas controlling vegetative functions.

Damage to the middle cerebral artery can result in hemiplegia (paralysis of one side of the body), intellectual deficits, and other impairments.

Venous System

The venous system comprises superficial and deep veins, with the deep veins being more significant due to their higher blood flow. The deep venous system closely resembles the arterial system, while the superficial system has a distinct anatomy.

Upper Limbs

The upper limbs are highly vascularized, with superficial veins prominent in some areas. The radial and ulnar veins are located at the back of the forearm. The anterior forearm features the radial, ulnar, and median veins. The upper arm has two main veins: the cephalic vein (outer edge) and the basilic vein (inner edge). The cephalic vein is well-developed and often used for catheterizations.

Lower Limbs

Two systems irrigate the lower limbs:

• Internal saphenous vein: Runs along the inside of the foot and leg, originating near the internal malleolus. It ascends through the subcutaneous tissue and joins the femoral artery in the groin via the saphenous arch.
• External saphenous vein: Covers the dorsum of the foot and ascends past the outer ankle. Connections exist between the two systems.

Venous insufficiency is more common in superficial veins (varicose veins). Leg veins have valves that prevent blood from pooling in the feet due to gravity. These valves are essential for low-pressure venous return. Valve malfunction can cause varicose veins.

Head

The external and internal jugular veins drain blood from the head. The external jugular vein collects blood from the face, while the internal jugular vein drains blood from the deep intracranial veins. The superficial venous system drains into the deep venous system.