How many layers of tissue are there from the scalp to the brain? What is the organization like at ea

The human brain refers to the three major pieces of nerve fiber tissue contained in the cranial cavity: the brain, brainstem, and cerebellum. For the sake of space, I will focus on the cerebral hemispheres and prefrontal cortex regions that are directly related to human intellectual activity.

The brain of modern humans occupies almost all the vacancies in the cranial cavity (its proportion is 87%, the cerebellum is 11%, and the brainstem is 2%), and in terms of its appearance, it is quite oval, its long axis is anteroposterior, about 16 17 cm long, about 13 14 cm wide from side to side, about 12 5 13 cm high from top to bottom, and the total weight is about 995 1200 grams—about 1 40 of body weight, about 85% of brain weight (1400 grams), 40 times heavier than the brainstem (from the brain to the thalamus), and 9 times heavier than the cerebellum.

The brain is divided into two hemispheres, the left and right hemispheres, and the cerebral cortex (gray matter) covers most of each cerebral hemisphere, which is where the neuronal cell bodies are concentrated. Inside, white matter is made up of nerve fibers or myelin sheaths. Each hemisphere has three faces, the lateral surface (about 1 3 of the entire cortical area), the medial surface and the bottom surface (about 2 3 of the area); The surface of the hemisphere has many sulcus or fissures of varying depths, and the bulges between the sulcus or fissures are called back, which greatly increase the surface area of the brain; The important sulcus and fissures on the lateral surface of the brain include the lateral cerebral fissure, the parieto-occipital fissure, and the ** sulcus.

Due to the separation of the three grooves, the cerebral cortex is divided into four parts: frontal lobe, parietal lobe, temporal lobe, and occipital lobe.

The cerebral cortex (cortex) is a highly folded plate of nerve tissue with an average thickness of about 2 3 mm (** Anterior gyrus is about 4 mm thick; The occipital lobe is about 1 25 mm thick - the thickness of all mammalian cerebral cortex is almost the same, about 2 mm), the volume is about 300 cubic centimeters, the weight is about 600 grams, the surface area is about 2200 2600 square centimeters, accounting for about 40% of the entire cerebral hemisphere, if it can be the size of a newspaper, it contains a variety of different nerve cells and glial cells (glial cells play a supportive, nutritious, The number of nerve cells is about 42 billion), and the number of nerve cells is about 14 billion, of which 135 billion are occupied by the cerebral neocortex, accounting for 96%. Its specific distribution in the main functional regions of the neocortex of the brain is as follows: 3.5 billion frontal lobe symphysis areas, 2.5 billion temporal lobe symphysis areas, 2.5 billion parietal lobe symphysis areas, 800 million first-level visual areas, 0 500 million first-level auditory areas, 800 million first-level somatosensory areas, 800 million first-level motor areas, and 2.5 billion in other regions.

Gray matter is nerve tissue, and white matter is connective tissue

1) Gray matter: The layer of gray matter that covers the surface of the cerebral hemispheres is called the cerebral cortex, which is where the cell bodies of neurons are concentrated. The distribution of these neurons in the cortex has a strict hierarchy, and the paleocortex on the medial surface of the cerebral hemisphere is relatively simple, generally with only three layers:

molecular layer; pyramidal cell layer; Polymorphic cell layer.

2) The deep surface of the cortex is white matter, and there are gray matter nuclei in the white matter, which are close to the base of the brain and are called the basal nucleus (or basal ganglia). The basal nucleus is dominated by the striatum. The striatum is made up of a caudate nucleus and a lenticular nucleus.

The caudate nucleus is thick anterior and thin caudal, curved and encircling the thalamus; The lenticular nucleus is located lateral to the caudate nucleus and thalamus, and is divided into globus pallidus and putamen. The caudate nucleus and putamen appear later in phylogeny (i.e., animal evolution) and are called neostriatum, whereas globus pallidus appears earlier in phylogeny and are called old striatum. The main function of the striatum is to coordinate the movement of the muscles and maintain a certain posture of the body.

Answer one, the cerebellum hypothalamus brainstem.

Answer two, cells.

The brain is composed of three parts: the cerebral cortex (gray matter), the cerebral medulla (white matter), and the basal nucleus. Together, they complete the functions of the brain.

If your level of knowledge is high enough, it can also be said that the cerebral cortex is mainly made up of the cell bodies of nerve cells, and the cerebral medulla is mainly made up of axons of nerve cells. Together, the cell body and axons make up the "nerve cell".

To put it another way, a complete nerve cell is partly in the cerebral cortex and partly in the cerebral medulla.

The brain includes the cerebral cortex, which is the part of the brain.