The main parts of the brain include:
The cerebrum. This is divided into the right hemisphere (right side) which controls the left side of the body, and the left hemisphere which controls the right side of the body. Each hemisphere is divided into various sub sections, the main divisions being the frontal lobe, temporal lobe, parietal lobe and occipital lobe. The cerebrum is also where you 'think' and store your memory.
The cerebellum. This lies behind and below the cerebrum. One of it's main functions is to help control balance and co-ordination.
The brain stem. This helps to control basic bodily functions such as the heartbeat, breathing, blood pressure, etc. Nerves from the cerebrum also pass through the brain stem to the spinal cord.
The meninges. These are thin layers of tissue which separate the skull from the brain. The outer layer next to the skull is called the dura. The next
layer is called the arachnoid. Under the arachnoid tissue is the cerebrospinal fluid (CSF) which bathes the brain and spinal cord.
The pituitary gland. This releases various hormones into the bloodstream.
The main type of cell in the brain is called a neurone. There are millions of neurones in the brain. Neurones have long thin nerve fibres which enable them to send messages to other parts of the brain, and down the spinal cord to all parts of the body. The brain also contains cells called glial cells. These provide support, nourishment and protection for neurones. There are various types of glial cells including astrocytes, oligodendrocytes and ependymal cells.
What are tumours and what are brain tumours?
A tumour is a 'lump' or 'growth' of tissue made up from abnormal cells. Tumours are divided into two types - benign and malignant (cancerous).
Benign tumours - general
Benign tumours may form in various parts of the body. Benign tumours grow slowly, and do not spread or invade into other tissues. They are not 'cancerous' and are not usually life-threatening. They often do no harm if they are left alone. However, some benign tumours can cause problems. For example, some grow quite large and may cause local pressure symptoms (especially in the brain), or look unsightly. Also, some benign tumours which arise from cells in hormone glands can make too much hormone which can cause unwanted effects.
Benign brain tumours
Some types of tumours in the brain are benign. The cells of a benign brain tumour do not infiltrate and grow into brain tissue. However, a benign brain tumour can cause symptoms and problems as it gets bigger. This is because it can increase the pressure inside the skull, and press on the delicate brain tissue. Also, some benign pituitary tumours release large amounts of hormones into the bloodstream which can cause various problems. Therefore, unlike many other types of benign tumour, a benign brain tumour often needs treatment to ease symptoms.
Malignant tumours - general
A malignant tumour is a cancerous growth. Cancer is a disease of the cells in the body. There are many different types of cell in the body, and many different types of cancer which arise from different types of cell. What all types of cancer have in common is that the cancer cells are abnormal and multiply 'out of control'. However, there are often great differences between different types of cancer. For example:
So, cancer is not just one condition. In each case it is important to know exactly what type of cancer has developed, how large it has become, whether it has spread, and how well the particular type of cancer responds to various treatments. This will enable you to get reliable information on treatment options and outlook.
The original site where a tumour first develops is called a primary tumour. Malignant tumours may also spread to other parts of the body to form 'secondary' tumours (metastases). These secondary tumours may then grow, invade and damage nearby tissues, and spread again.医学全在线www.med126.com
Malignant brain tumours - primary malignant brain tumours
A primary malignant brain tumour is a cancer which arises from a cell within the brain. The cells of the tumour grow into and damage normal brain tissue. Also, like benign brain tumours, they can increase the pressure inside the skull. However, unlike most other types of malignant tumours, primary brain tumours rarely spread (metastasize) to other parts of the body.
There are various types of primary malignant brain tumour. The different types develop from different types of cell in the brain. As a general guide, each type is graded on a scale 1-4. Grade 1 and 2 tumours are said to be 'low grade' and grade 3 and 4 'high grade'. The higher the grade, the more 'aggressive' the tumour tends to be and the faster it tends to grow. The treatment options and outlook (prognosis) can vary depending on the type and grade of the tumour.
Malignant brain tumours - secondary malignant brain tumours
A secondary malignant brain tumour means that a cancer which started in another part of the body has spread to the brain. Many types of cancer can spread ('metastasise') to the brain. The most common are cancers of the breast, lung, colon, kidney, and melanoma of the skin.
More on the different types of brain tumour
There are many types of benign brain tumour and primary malignant brain tumour. Many are very rare. The following is a brief description of the main types.
Meningioma
Meningioma's are usually benign. They arise from cells in the meninges (the tissues that surround the brain).
Medulloblastoma
These arise in the cerebellum and are always high grade malignant tumours. They are uncommon in adults, but are one of the two most common brain tumours in children (the other being an astrocytoma in the cerebellum).
Gliomas
These are malignant primary brain tumours that arise from glial cells. There are various types, depending on the cell of origin. For example:
Primitive neuroectodermal tumours (PNETs)
These are very similar to medulloblastomas and mainly occur in children.
Pituitary tumours
There are various types of tumour which arise from the different cells in the pituitary gland. They tend to be benign, but the cells of the tumour may produce large quantities of hormones which can cause various symptoms. As they grow, they may also cause pressure symptoms. The optic nerves (the nerves of sight) are near to the pituitary and so a growing pituitary gland tumour may press on an optic nerve and affect vision.
Acoustic neuroma (schwannoma)
This is a benign tumour which arises from schwann cells which cover the nerve that goes to the ear. Symptoms of an acoustic neuroma can include deafness on the affected side, and vertigo.
Other
There are various other rare types of benign and primary malignant brain tumours.
How common are brain tumours?
Benign brain tumours and malignant primary brain tumours are uncommon. Overall, one occurs in about 14 in 100,000 people each year. The most common types in adults are benign meningioma and a glioma called glioblastoma multiforme. Some types are very rare. Brain tumours can occur at any age. Some types (such as medulloblastoma) are more common in children, and some are more common in adults. Generally, the tumours that tend to occur in adults become more common with increasing age.
Secondary ('metastatic') brain tumours are more common than benign brain tumours and malignant primary brain tumours.
