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The cranial cavity, also known as intracranial space, is the space within the
skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
that accommodates the
brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
. The skull minus the
mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
is called the ''cranium''. The cavity is formed by eight cranial bones known as the
neurocranium In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria (skull), ...
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 The facial skeleton comprises the ''facial bones'' that may attach to build a portion of the skull. The remainder of the skull is the braincase. In human anatomy and development, the facial skeleton is sometimes called the ''membranous viscerocr ...
. 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 Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the bra ...
, 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 Pia mater ( or ),Entry "pia mater"
in
arachnoid mater The arachnoid mater (or simply arachnoid) is one of the three meninges, the protective membranes that cover the brain and spinal cord. It is so named because of its resemblance to a spider web. The arachnoid mater is a derivative of the neural c ...
, and the
dura mater In neuroanatomy, dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord. It is the outermost of the three layers of membrane called the meninges that protect the central nervous system. ...
. 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 mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical E ...
- 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 The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobe ...
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 The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental m ...
. 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 In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria (skull), ...
Intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury (mmHg) and at rest, is normally 7–15 Millimeter of mercury, mmHg ...
Paranasal sinuses Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the sphenoi ...


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.
{{Authority control Skull