The point of this page
The soft brain is protected by hard bone and liquid named “Cerebrospinal fluid”.


      The skull

 Front part         Side part


Cross section from the top





The cerebrum and the cerebellum are in the space surrounded by bone. You can see the brain from the top and bottom in this picture.
The hole shown by the blue line is where the brain connects to the spinal cord.




The brain and the spinal cord are shown to beseparated in this animation.




As shown in below animation, the spinal cord covered by backbone starts from head and ends at 2nd or 3rd of the hip bone.


2nd and 3rd of the hip bone are shown as the red point in the left picture.













 The surface of newborn baby brain is shown in the below animation.

You can see the white soft and flabby thing here. This is ‘anterior fontanel’, the place bone is not connected.
When a fetus is born, bones are crossed to each other to make the fetus head smaller at anterior fontanel, which makes it easier for a fetus to get out from mother.

Anterior fontanel starts shrinking from around 10 months old, and it cannot be touched from 10 months old to 1 year 3 months old. It is completely closed around 2 years old and it differs between individuals. Posterior fontanel is closed around 1 month old.から引用

 The brain grows big when we are in the womb. Upper right picture from

Head circumference reflects the size of the brain. The brain size of a baby is 25% of the brain size of an adult. Head circumference is 33.5cm for a boy and 33.0cm for a girl.
Head circumference grows longer and becomes 42cm around 6 months, 46cm when 1 year old and 46cm + age cm after 1 year to 3 years old.
The brain size grows up to 80% of an adult brain till 3 years old, 90% till 7 years old. The weight becomes 90% of the adult brain at 4-5 years old.





While the brain grows up fully from a fertilized egg, the immature brain consists of 5 parts, telencephalon, diencephalon, mesencephalon, epencephalon and myelencephalon.
Each part grows as follows

  1. The telencephalon grows to the cerebrum
  2. The diencephalon grows to the thalamus, hypothalamus and hypophysis.
  3. The mesencephalon grows as the mesencephalon.
  4. The epencephalon becomes the cerebellum and the pons.
  5. The myelencephalon grows to the medulla oblongata.

The brainstem is like the trunk of the brain and is composed of 3 parts, the mesencephalon, the pons and the medulla oblongata.
A full grown brain consists of 4 parts, the cerebrum, the diencephalon, the brainstem (the mesencephalon, the pons and the medulla oblongata) and the cerebellum.

The liquid called cerebrospinal fluid protects the brain along with the head bone. The brain is floating in the cerebrospinal fluid, as if it is like a tofu in the water. Tofu cannot be broken in the water even if the surroundings shake. The brain is the same.
When you click the box besides the animation, it moves little by little. The white part is the cerebrospinal fluid, which is a clear liquid and slightly alkaline. There are few cell components in it. It weighs about 110 to 170 ml and keeps changing every 5 to 7 hours, about 3 to 5 times in a day. It keeps the brain and the spinal cord floating, protects them from impact, gives nutrition to the brain and cleans the brain.?






Yellow green is the film of the spinal cord, called dura mater.
Blue is the dura mater inside the brain and the dura maters are not inter-connected.
Yellow is the arachnoid.
White is the cerebrospinal fluid under the arachnoid.
300*294-74.5kB - the cerebrospinal fluid-from Brain Science Dictionary

Production and absorption of the cerebrospinal fluid


The cerebrospinal fluid is made from the blood at the choroid plexus which is found in the lateral ventricle, the third ventricle and the fourth ventricle. The cerebrospinal fluid exists between the arachnoid and the pia mater. It is a clear liquid and its composition is almost the same as the lymph.
From the directing arrow in the picture, we can see that the cerebrospinal fluid fills the brain and flows through the fourth ventricle, median aperture, lateral aperture and goes out to the subarachnoid space.
Some of the cerebrospinal fluid go to the upper cranium, and the rest go down along the spinal cord. The former is absorbed through arachnoid granulation at the superior sagittal sinus and the latter goes through not only the nerve fiber but also through the pia mater, arachnoid, dura mater, nerve which protect the nerve fiber and finally reaches the body tissues.から転用

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