Topographical & Surface Anatomy of the Skull, Cranial Cavity and Cranial Nerves

Surface & Functional Anatomy  Understand and explain the relevant surface and functional anatomy of the Skull, Cranial Cavity & Cranial Nerves.

Following info from Grays Anatomy for Students: The head is in the anatomical position when the inferior margins of the bony orbits and superior margins of the acoustic meatuses are in the same horizontal plane (the Frankfort Plane). In addition to the external acoustic meatus and the bony margin of the orbit, other features that are palpable are the head of the mandible, zygomatic arch, zygomatic bone, mastoid process and external occipital protuberance.

Another clinically useful feature is the vertex of the head. This is the highest point of the head in the anatomical position and marks the approximate point on the scalp where there is a transition from cervical to cranial innvervation of the scalp. Anterior to the vertex the scalp is innervated by the trigeminal nerve.

The middle meningeal artery is a branch of the maxillary artery in the infratemporal fossa. It enters the skull through the foramen spinosum and is within the dura mater lining the cavity.

o In lateral blows to the head the middle meningeal artery can be ruptured, leading to extradural haemorrhage and death if not treated.

o The anterior branch of the middle meningeal artery is the part of the vessel most often torn. This branch is in the ‘temple’ region of the head in the pterion region.

o The pterion is a small circular area enclosing the region where the sphenoid, frontal, parietal, and temporal bones in the skull come together. Lateral blows to the head can fracture this junction point, leading to possible tears in the middle meningeal artery. This can lead to a progressively larger extradural haematoma.

Major features of the faceThe major features are those related to the anterior openings of the orbit, nasal and oral cavity.

o The sphincter muscles which close the eyes are obicularis oculi, that of the mouth is obicularis oris. These are both innervated by the facial nerve (VII).

Arterial pulses can be felt at four locations in the head and neck:1. Carotid Pulse 2. Facial Pulse - the facial artery can be palpated as it crosses the inferior border of the

mandible immediately adjacent to the anterior margin of the masseter muscle3. 1st Temporal pulse - The anterior branch of the superficial temporal artery can be

palpated posterior to the zygomatic process of the frontal bone as it passes lateral to the temporal fascia and into anterolateral regions of the scalp.

4. 2nd Temporal pulse - In some individuals pulsations of the superficial temporal artery can be seen through the skin.

Eye movements and muscles responsible