The structure identified by the letter F is the vertebral artery which are vertebral arteries of a pair of arteries that originate from the subclavian arteries in the neck and ascend up the spine.
The vertebral arteries provide blood to the brainstem, cerebellum, and occipital lobe of the cerebral cortex. The vertebral arteries originate from the subclavian arteries in the neck, just lateral to the first rib.
The vertebral arteries ascend up the spine, embedded in the transverse foramina of the cervical vertebrae. They pass through the foramen magnum and enter the skull base. The left and right vertebral arteries merge at the base of the brain to form the basilar artery.
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