cranial cavity

The cranial cavity, also known as intracranial space, is the space within the skull that accommodates the brain. The skull minus the mandible is called the ''cranium''. The cavity is formed by eight cranial bones known as the neurocranium that in humans includes the skull cap and forms the protective case around the brain. The remainder of the skull is called the facial skeleton. Meninges are protective membranes that surround the brain to minimize damage of the brain when there is head trauma. Meningitis is the inflammation of meninges caused by bacterial or viral infections.

Structure

The capacity of an adult human cranial cavity is 1,200–1,700 cm³.

The spaces between meninges and the brain are filled with a clear cerebrospinal fluid, increasing the protection of the brain. Facial bones of the skull are not included in the cranial cavity. There are only eight cranial bones: The occipital, sphenoid, frontal, ethmoid, two parietal, and two temporal bones are fused together by the ossification of fixed fibrous sutures. The frontal and sphenoid bones are towards the front middle of the skull and in front of the temporal bone. The ethmoid bone is the bone at the roof of the nose that separates the naval cavity from the brain. It is a part of the dorsal cavity the cranial cavity and the spinal cord. The occipital bone is at the back of the skull. The dorsal cavity is lined by the three meninges. The three meninges are the three membranes that envelop the brain and spinal cord, in which the central nervous system developed, which are the pia mater, and the dura mater. The latter is the thickest and outermost of the three membrane layers; it contains the most collagen, and it is derived from the mesoderm - the middle germ layer or the primary layer of the cells formed in embryogenic development via epigenetic effects induced by developmental cues, in the early embryo. Also there are the two parietal bones and the two temporal bones, which are a part of the dorsal cavity located on the posterior of the body. The occipital bone found in the rear of the skull is thicker to limit fractures caused by blows to the back of the head. The eight bones are blended together to form the cranial cavity. The pituitary gland is also found in the make up of the cranial cavity. It plays a major role in the body, creating and secreting many bodily hormones. The gland secretes different fluids that are important for the body to function. The body's temperature, physical, and sexual functions are regulated by this gland. One of the major glands are controlled through this cavity.

The cerebrum is the most anterior part of the brain, located in the top half of the skull, consisting of two hemispheres separated by a fissure and connected by the corpus callosum. It is responsible for integrating complex sensory and neural functions, and subsequently initiating and coordinating voluntary activity in the body.

The cortex is the outer layer of the cerebrum, composed of folded grey matter. Its neuron cell bodies, dendrites, synapses, axons, and axon terminals play a crucial role in consciousness. The two hemispheres are divided into four lobes, distinct sections of the organ: the frontal lobe, parietal lobe, temporal lobe, and occipital lobe. Our understanding of the specific functions of the cerebral cortex are based on the theories of localisation and lateralisation. Localisation is the theory that specific areas of the brain are associated with/responsible for particular physical and psychological functions. Lateralisation is the theory that one hemisphere is dominant over the other/responsible for particular physical and psychological functions.

The meninges are the three membranes that line the skull and vertebral canal, and enclose the brain and spinal cord. The Cerebrospinal Fluid serves a vital function in the cerebral autoregulation of cerebral blood flow. Cerebrospinal Fluid occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord.

Neurocranium

Intracranial pressure

Paranasal sinuses

Function

There are twelve cranial nerves that are responsible for controlling the cranial cavity. These nerves are responsible for providing necessary sensory information for things such as smell, taste, hearing, and sight. The ability to sleep and chew is also a part of one of the things the cranial cavities in charge of. In order for the cranial cavity to be able to do all these functions it has to have the organs to be able to control those systems. The cranial cavity houses the Brain, Meninges, and the Cerebrospinal Fluid. The primary function of the brain is supplying information to the rest of the body and to help it function as whole. It helps supply some of the cranial nerves from the face to the feet and also to help get the body performing critical bodily functions.

The cranial cavity includes eight cranial bones and they are collectively combined to form this area. A gland that is found in this cavity is called the pituitary gland which secretes different fluids that are necessary for different parts of the body to function. There are many things that are regulated by this gland such as body temperature, physical growth, and sexual functions. The pituitary gland also controls the thyroid gland.

The cranial cavity has a variety of spinal and cranial nerves residing in it. The cranial nerves are responsible for storing sensory information needed for taste, smell, sight and the ability to hear. The spinal nerves allow for the sensory and motor signals to be received, which provide a normal feeling and function for the arms and legs.

Clinical significance

In the event that the brain strikes the inside of the skull, there is a risk of a minor traumatic brain injury (concussion). This type of injury can alter brain function, cause memory loss, headaches and/or nausea. A minor traumatic brain injury can be followed by post concussion syndrome. As there are a number of structures in the cranial cavity, a traumatic injury to the head can potentially cause major damage to the brain. This is why it is recommended to get medical attention following a head injury.

The cranial cavity houses the meninges, as well as other necessary organs, and these membranes surround the central nervous system. If an infection forms, it can lead to a disease called meningitis which can be potentially fatal.

Martini R, Ober W, Garrison C, Welch K, and Hutchings RT. 2001. ''Fundamentals of Anatomy and Physiology'', 5th ed. Prentice Hall, New Jersey. p. 195.

References

External links

Anatomy of cranial cavity.

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Skull