Hirnfossa

Hirnfossa, also known as the posterior cranial fossa, is the lowest part of the cranial cavity, situated at the base of the skull. It is primarily occupied by the cerebellum and the brainstem, which includes the pons and medulla oblongata. The dura mater, a tough, fibrous membrane that encloses the brain and spinal cord, forms the boundaries of the posterior cranial fossa.

The structure of the hirnfossa is defined by bony landmarks of the skull. The occipital bone forms the posterior and inferior walls, while the temporal bones contribute to the lateral walls. The superior aspect is bordered by the tentorium cerebelli, a fold of dura mater separating the cerebrum from the cerebellum. Key openings within the hirnfossa include the foramen magnum, through which the spinal cord exits the skull and the vertebral arteries enter, and the internal acoustic meatus, which transmits the vestibulocochlear and facial nerves.

The contents of the hirnfossa are vital for many basic life functions. The cerebellum plays a crucial role in coordinating voluntary movements, posture, balance, and motor learning. The brainstem connects the cerebrum and cerebellum to the spinal cord and controls essential autonomic functions such as breathing, heart rate, blood pressure, and consciousness. Due to its critical contents and relatively confined space, the hirnfossa is susceptible to damage from trauma, tumors, and vascular events, which can lead to severe neurological deficits.