User:Physiotherapist1234/sandbox

The crown is the pinnacle point of the head and is also referred to as the head as a whole. The structure and anatomy of the crown vary between different organisms including humans, birds, and whales. The human crown has three layers of the scalp and bones that have ventricles that dispose of waste material within the brain. The skull also contains a range of suture, blood vessels, and cranial nerves branching towards the crown of the head.

The structure of the human crown provides a protective cavity for the brain and optimizes the crown's ability to make sure the neocortex is safe. Other organisms such as whales have their blowholes and right naris on their crown causing a dull head shape. In comparison, bird species have a crest located on their crown, used for communication, emotion, and courtship or aggressive behaviors.

The macroevolution of the human crown led to differentiating structures that are comparable between modern and archaic human species such as changes to the cranial vault. The human crown is still prone to different injuries and disorders such as cerebrospinal fluid leak which results in intense headaches and in extreme cases, fluid leaking from the individual’s ears and nose. Other diseases include meningioma, a tumor surrounding essential blood vessels, and nerves near the crown of the head causing symptoms such as memory loss.

Structure
The crown is at the top of the human skull and contains the scalp. The scalp has three distinct layers including the cutaneous layer, a subcutaneous connective tissue layer, and a muscle layer. The crown is composed of layers of bone that contain ventricles that accumulate and remove the waste products of the brain such as cerebrospinal fluid. The human head or crown is 4 and 7 millimeters thick and varies between people.

The frontal bone as well as the parietal bone is separated by a range of fibrous joints called sutures and makes up the crown of the head. The sutures are an essential part of growth and development, allowing the skull to expand as the brain increases in size. Different sutures evident within the frontal and parietal bone of the skull expand in a specific direction causing a symmetrically shaped human head. The frontal bone has two separate bone structure, joined together at the frontal suture. The different parts the frontal bone is composed of include the squamous, orbital, and nasal parts. The frontal bone connects to the parietal bone at the coronal suture to shape the crown and sides of the skull. There are two separate parietal bones are also joined at the sagittal suture thus ensuring the crown is stable.

Other structures of the human crown include the blood vessels and nerves which are essential in allocating nutrients and the transmission of information to the brain. The superficial temporal vein branches from the common external carotid artery and is able to reach different areas of the skull including the crown leading to the access of oxygenated blood from the heart. The blood vessels within the human crown also act as a barrier due to their specialised cell walls. As a result, this prevents the release of harmful chemical substances within the brain through a process known as diffusion. Another structure of the human crown includes the nerves within the central and peripheral nervous systems. The skull encompasses 12 different nerves with specific and distinct functions. The olfactory nerve within the frontal lobe is essential for the sense of smell. Other nerves contain myelin on the axon which causes a faster transfer of information to the brain.

Organisms such as whale and bird species have different crown structures and the species use them in different situations. For instance, sperm whales have their blowholes situated asymmetrically on the crown of the head to breathe, and their right naris placed on a specific part of the crown causing a dull head shape. Birds contain a crest on the crown of different bird species. The range of features make up the crest and determines the bird’s emotions and courtship or aggressive behaviors. For instance, bird species such as the northern cardinal move the crest intensely to signify dominance and communication.

Function
The main function of the crown or head is to protect the brain from specific physical injuries. The neurocranium has the frontal and parietal bones that make up the crown and protect parts of the brain including the frontal lobe as well as the parietal lobes. The structure of the human head or crown involving the three membranes of the meninges ensures stability and prevents injuries directed to these lobes. For instance, the meninges which include flexible sheets between the brain, the spinal cord, and skull aim to protect the frontal lobe, located behind the forehead. The cerebrospinal fluid within the ventricles of the skull reduce the extent of the injury by acting as a cushion. Protecting the frontal lobe allows for humans to perform motor movements and to execute functions. The parietal lobe of the neocortex contains a strip which targets the sense of touch and allows for the representation of space for action is protected due to the thick layers of the crown or head.

Injuries and Diseases
The crown or human head is subjected to a range of injuries and diseases causing the brain to be vulnerable. The extent of the injuries and diseases directed to the human crown causes additional implications to the brain hence impacting the individual’s ability to function normally. The range of injuries and disorders have specific causes, medical signs and symptoms, diagnosis methods and treatments.

Cerebrospinal fluid leak (CSF leak)
A common disease associated with the crown includes the cerebrospinal fluid leak which involves the excess removal of fluid within the meninges. The cerebrospinal fluid leak is mainly caused by a head, brain, or spinal injury which tears the meninges membrane. The excessive leakage of the cerebrospinal fluid leads to symptoms that include intense headaches. An extreme sign of this disorder includes the leakage of fluid through the patient’s ears and nose. The diagnosis of the cerebrospinal fluid leak is determined from examinations including a computerised tomography scan which involves an X-ray image of parts of the skull including the crown hence locating the leak. Health professionals offer treatments to manage the symptoms associated with the disease. For example, consuming fluids such as water aims to stop excess leakage and reduce headaches, and antibiotics are also provided if signs of infection are clear such as fever and chills.

Meningioma
Meningioma is a cranial disorder associated with the meninges and is also known as a tumor since it surrounds the blood vessels and nerves near the crown of the skull. The causes of the disorder include a rapid division of cells around the area. The patients that have meningioma develop signs and symptoms including amnesia and epileptic seizures. The direct impact to the frontal lobe of the brain causes symptoms such as weakness to the arms and legs. Diagnosis is made via imaging tests such as magnetic resonance imaging (MRI) which involves high-frequency radio waves and a strong magnetic field allowing for the measurement of protons in the water. The treatments recommended involves surgery to remove the tumor from the patient’s meninges and the extent of the surgery depends on the size and aggression of the meningioma.

Fractures
Bone fractures to the crown of the head are either linear and depressed and range in severity based on the impact to the skull. For example, the linear fracture involves a break to the skull whereas the depressed fracture results in the scatter of skull fragments. The skull fractures are mainly caused by incidents involving a vehicle, assault, or a fall. In more severe cases, penetrating skull fractures caused by an object such as a metal rod or bullet breaks through the skull completely. Based on the severity of the fracture, symptoms may include nausea, memory loss, concussion, bruise, and lethargy. Another symptom such as bleeding results in the build-up of pressure in the skull and thus pushes the brain to the brainstem opening leading to a coma. Diagnosis occurs due to a range of physical exams which identifies the extent of the injury and thus possible treatments. For example, the computerised tomography scan identifies the site of the fracture and any associated injuries to the brain, whereas magnetic resonance imaging highlights the damaged tissue. The treatments of severe skull fractures include surgery and medication to avoid infection, however, for linear fractures treatment involves rest for approximately 5 to 10 days, so that the crown can heal.

Gorham Disease
Gorham disease is a condition that targets the human musculoskeletal system including the crown of the skull. The chronic disorder involves the progressive loss of bone, although, symptoms such as intense pain are not evident during the initial stages. The cause of the Gorham disease has not been discovered, however, cells associated with the breakdown of fragile and old bones including osteoclasts are considered to be the main link towards identifying the cause. The symptoms of the disease are clear following a fracture to the crown of the skull and as a result, patients experience abnormal deformities as well as issues to the nervous system. Diagnosis occurs through physical exams such as X-rays and magnetic resonance imaging which find the decrease in bone mass (osteolysis) and deformities. Treatment of the disease involves a range of techniques to prevent spread from the skull to the spine or chest of the patient. Chemotherapy and surgery, as well as lifestyle changes such as consuming a diet of high protein, aim to minimise the severity of the disease.

Evolution
The macroevolution of the human species resulted in more bones and muscle structures that support the crown of the head, compared to primates. Modern human species have a cranial base which is more angled and a cranial vault that is rounded, compared to archaic human species. Modern human species have their temporal lobes positioned under the cranial base signifying the increase in the size of the human brain and skull.

The sagittal vaults morphology, which is the area that joins the two parietal bones together to make up the structure of the crown, has remained the same for archaic and modern human species. The cartilage embedded within the skull plays a major role in the changes of the crown between archaic and modern human species. The cartilages evident within the cranium were an essential part in defending the central nervous system, however, over time the cartilage began to shape the crown by a process known as endochondral ossification. This process involves the replacement of grown cartilage with bone to develop the bone structure of the skull.