The skull is the term used to describe the bones of the head. In medical parlance, the skull is also called “cranium”. Thus, if a process exists “intracranially” (tumors, bleeding, etc.) according to the doctor, this means “located in the skull“.
What is the cranium?
One would think that the skull is a single, large, bony ball, inside of which is simply the brain – far from it: the skull is just about the most complicated structure that human nature has in store for the interested anatomist. A myriad of intergrown individual bones, furrows, elevations, and penetration points make the bony skull a truly difficult task for three-dimensional thinking. In the following, at least the rough structures and their correlations with diseases will be somewhat ordered for once.
Anatomy and structure
First of all, it makes sense to divide the skull into cranium and facial skull. Quite clear is the anatomy of the skullcap, sensibly belonging to the cranium: here meet the parietal bone, frontal bone, temporal bone and occipital bone and form an oval hood. At their transition points lie the so-called cranial sutures or sutures, which at birth are not yet completely fused together and thus form the famous “holes in the head“, the fontanelles, which can be felt in newborns and infants up to two years of age. The plates of the skullcap also leave passageways for small blood vessels, although the main blood supply to the skull is almost exclusively through the large neck vessels. “Calvaria,” by the way, is an old term for the skullcap that is still often used in clinical parlance today. The cranial calotte is covered by a sinewy plate, the galea aponeurotica, the adipose tissue head rind, and finally the skin with the head hair (if you have it). The anatomical structure of the base of the skull, which forms the underside of the cranial balloon, so to speak, becomes incomparably more complicated. It must, of course, hold in readiness any number of receptacles for the structures of the brain and face and any number of passage points for nerves, blood vessels and the spinal cord. Ethmoid bone, sphenoid bone as well as again frontal bone and occipital bone form the main pillars of the skull base, besides, the paired temporal bone on both sides also works here. It is the occiput that allows the spinal cord to exit into the spinal canal through a large hole at the back below, the foramen magnum. With this, however, only the brain skull would be described. The facial skull is made up of individual bones, some of which are quite complex in shape, with lots of nooks and crannies for the pharynx, oral cavity, nasal cavity, paranasal sinuses (the most important of which are the frontal sinus, two maxillary sinuses, the sphenoid sinus and the ethmoid cells) and the eye socket. The facial skull consists of two large bones, the maxilla and mandible, and six smaller bones: Zygomatic bone, Lacrimal bone, Nasal bone, Ploughshare bone, Palatine bone and Inferior turbinate bone. The description of each connecting pathway and conduit fills many pages of an anatomy book and is difficult to understand without pictures.
Functions and tasks
The function of the skull is actually quite simple: to protect the brain and everything else inside it. In this context, the protection of the brain can be compared to the protection of the occupant in a modern car, namely according to a three-stage principle: crumple zone – stable passenger cell – safety belt or airbag. These three stages can also be seen in the principle of the wrappings of the brain: The head rind is the deformable zone for light blows and bruises, the skull is the stable zone, and the cerebrospinal fluid space around the brain acts as a deceleration zone to absorb any kind of shock to the sensitive nerve tissue. The construction of the brain skull follows the lightweight principle: Wherever possible, evolution has built in air cavities (sinuses), and the bone plates are relatively thin, but optimally protected against external forces by a clever system of reinforced pillars and internal bracing. The skull is also important for the movement of the head as an attachment point for muscles of the neck. Furthermore, a myriad of mimic muscles connect the bones of the facial skull, and food intake is also difficult without the functional unit of the upper and lower jaws.
Diseases and ailments
There are a myriad of diseases and injuries that take place in the cranial region.Therefore, only a short “tour” can be made in the following. When exposed to brute force, whether by blows and blows or by falling to the ground or hard objects, the skullcap and the facial skull can be injured. Skull fractures always refer to a fracture of the skull roof, which can be open (open connection brain – outside world) and closed (outer skin still intact). A skull base fracture usually requires even greater force and is all the worse because vital connecting and conducting pathways between the inside of the skull and the rest of the body can be destroyed or squeezed off. Hemorrhage is a major problem in emergency medicine; a rough distinction is made between hematomas of the scalp (harmless) from epidural hemorrhage (over the dura, the hard lining of the brain), subdural hemorrhage (under the dura), and subarachnoid or brain mass hemorrhage. It is not the initial injury or blood loss that is the main problem with these injuries, but space: the skull is such a stable structure and so densely filled with tissue that a hemorrhage takes up massive amounts of space, displacing healthy tissue. This, in turn, squeezes vital pathways, especially the connection between the brain and the spinal cord in the foramen magnum is in danger: if the brain stem is pinched here, the circulatory and respiratory centers there are squeezed and the affected person dies within a very short time. Subdural hemorrhages in particular are treacherous, since they feed only slowly from venous bleeding after an injury and only suddenly become symptomatic with clouding of consciousness after hours or days, namely when the intracranial pressure has become too great. In addition to injuries, there are also tumor diseases of the skull, whereby mainly benign meningiomas (originating from the meninges) are observed in many autopsies without ever having caused any problems to the affected person. However, they can grow large and in turn cause intracranial pressure and headaches. Blood cancers such as multiple myeloma also often affect the skull.
