The question of how much a human brain weighs has occupied the minds of scientists at all times. Increased interest in this topic is associated with attempts to understand the reasons for the genius of some people and the mental retardation of others. It is logical to assume that the largest organ contains more nerve cells, which means more resources to perform diverse tasks. In the course of research, it turned out that in Homo sapiens, also known as homo sapiens, the level of mental abilities is determined not by the number of nerve cells, but by the peculiarities of the hierarchical organization of brain structures. The level of intelligence of representatives of the species Homo sapiens is influenced by the relief of the surface of the brain matter, the number of grooves and convolutions.
What is cholesterol?
Cholesterol is produced by the liver and is found in foods of animal origin.
Our body needs a certain amount of cholesterol to keep cells functioning and renewing themselves. But 80% of cholesterol is produced by the body itself and only 20% comes from food. Therefore, in order to reduce the level of this substance in the blood, you need to eliminate at least this 20%, reducing the intake of cholesterol from foods. It is important that your body receives healthy fats that do not affect cholesterol levels or reduce them (these are mainly vegetable oils). But the amount of saturated and trans fats needs to be reduced. It is the latter compounds that play a key role in disrupting fat metabolism and changing cholesterol levels.
If you're managing your cholesterol levels, it's important to know which foods may raise them.
Characteristic
The brain is the control center of the nervous system, tissue with a spongy, soft structure, protected by the bone formations of the skull; the volume of the organ is individual in a person, like other parameters of the body. Brain weight varies between children, women and men, which is associated with different body weight indicators.
Different brain volumes in people with different body sizes correlate with different distributions of neuronal structures and conductive elements, which is due to the functional characteristics of the central nervous system. In people with large bodies, the length of the conductor elements and the volume of control centers are larger, which is associated with the need to maintain the functionality of executive systems, which are large in size.
The average brain weight of a normal person is about 1270 grams in women and 1390 grams in men. For any age, an increase in brain mass of 8-15% is typical in the male group compared to the female population. The brain weight of women and men directly correlates with indicators such as body surface area and height.
Scientists explain the relationship by the need for a larger number of neuronal structures that control the movements of body parts in people with greater muscle mass and a larger volume of internal organs. In tall people, a larger than average portion of the brain matter is involved in the process of regulating the functions of the autonomic and somatic systems.
A large brain in male and female populations is equally characterized by an excess of the volume of white matter (conducting structures) over the same indicator of gray matter (neuronal structures), which is associated with an increased distance between control centers and executive organs. The human brain weighs about 1000-2200 g, exactly how much is an individual characteristic.
Red meat
Fatty steaks and ground beef can raise LDL cholesterol levels because they are high in saturated fat. Processed red meats, such as bacon and sausage, are even worse for heart health because they are high in sodium (salt), which in excess can cause high blood pressure.
While saturated animal fats are okay in moderation, you'll be better off swapping red meat for heart-healthy fish or skinless white meat poultry. If you want steak, choose lean cuts: they contain less fat than regular beef. Limit your consumption of pork: it is a fatty meat and should be eaten no more than twice a month, choosing the leanest parts of the carcass. We wrote more about meat here.
How much did the smallest brain in the world weigh?
The exact weight of GM Justus Liebig is unknown. However, as a result of research, it was confirmed that he was the owner of the smallest brain in the world, which weighed less than a kilogram, while Justus Liebig went down in history as a brilliant chemist. The scientist played a role not only in science, but also in cooking. He is credited with creating a technology for cooking meat that preserves all the juices and nutrients. Many chefs still follow the advice of the eminent scientist who studied organic chemistry.
It was Liebig who recommended that cooks fry meat, retaining the juice, and cook it in soups. Liebig's influence turned out to be so great that his diets were and are being promoted by many modern nutritionists. However, not all the ideas of one of the most brilliant scientists in the world can be called relevant today.
Justus Liebig also became famous for his study of plants and animals, made a huge contribution to the consideration of their physiology, he devoted a lot of time to organic chemistry and the design of laboratory instruments. So he proved to the whole world that a small brain is not at all a hindrance to a scientist.
Pasta with cheese
This tasty and beloved dish is a champion in fat content.
When preparing it, they use butter, fatty cheeses, plus pasta - this is also an excess of calories. If you add bacon, sausage, sausages or meat, the dish becomes even more dangerous. Research has shown that refined carbohydrates, such as white bread and pasta, can also raise LDL cholesterol. If you can't imagine life without macaroni and cheese, choose whole-grain spaghetti and low-fat milk with "light" cheese. Plus, eat this dish no more than 2-3 times a month.
The most common myths about the brain
There are many different myths about GM in the world:
- One of them concerns the convolutions. Supposedly there are more of them with age. Initially, a person has a completely smooth structure of the brain, but over time, new neurons begin to appear, which leads to the appearance of grooves and ridges. After 40 weeks, the number of gyri is approximately equal to the number of gyri of the adult brain.
- Contrary to popular belief, we do not have the largest brain in the world. In the sperm whale it can reach enormous sizes and weigh more than 8 kilograms. An elephant has about 5 kilograms. The ratio of the size of the GM to the body in humans is approximately 2%, and in the same shrew it is 10%.
- People often note that memory and thought processes deteriorate with age, and this is true. However, the reason for this is not the “fading” of the intellectual abilities of the organ itself. Rather, the problem is related to lifestyle. The brain needs nutrition and rest, as well as equally active work.
- There is an opinion that our brain is like a computer and even works the same way as it does. But in fact, even if a GM can be called a computer, the principles of its functioning will still be sharply different. The fundamental difference between a GM and a computer is the combination of memory and computing processes. And memory itself is associated with nerve cells that carry out calculations.
- An interesting fact also concerns alcohol consumption. There is a myth that alcoholic beverages can cause great harm to GM. Of course, they can cause many diseases, but so far there is no clear evidence confirming that alcohol can kill neurons.
- There is another common myth that scientists consider the most absurd. Allegedly, people use a very small fraction of the potential of GM. But this is not true at all. Each department has its own functions, all of them are active and necessary for a person, since without them he could not lead normal life activities. Even during sleep, the brain remains active and engages in important processes.
Store baked goods
Store-bought muffins, cookies, waffles, bagels, croissants and cakes combine ingredients such as butter, sugar and white flour. In addition, cheap raw materials are often used for their preparation - trans fats and palm oil. They are considered unsafe because they increase the risk of heart disease.
If you want to pamper yourself with sweets and baked goods, make all these dishes at home, choose recipes that contain the least amount of oil, and avoid those that add margarine.
What cells does the brain have?
There are two groups of cells in the human brain. Small neurons and glial cells do all the work we need to function actively.
Neurons generate nerve impulses, glial cells act as auxiliary cells. Neurons are divided into sensory and efferent, and there are also interneurons. These cells communicate with each other through synoptic transmission. With the help of their axonal processes, they transmit impulses to each other, and the axons themselves branch and form synapses. Each neuron receives impulses not only from its neighbors, but also from many other neurons. This uses chemical signaling (neurotransmitter). Processes such as the generation of current occur in the GM, which leads to excitation of the membrane or inhibits it. The famous cells that are now on everyone’s lips play an important role. They are called stems. They are the ones responsible for the reproduction of new neurons.
Thus, we realized that there is no direct dependence on the size of the GM and intellectual abilities. Our brain still hides many secrets, so scientists have yet to discover its hidden capabilities.
Egg yolks
The myth that eating cholesterol-rich egg yolks raises blood lipid levels has already been debunked. Scientists have determined that although eggs are high in cholesterol, they are healthy because they contain vitamins, lecithin, choline and proteins.
Today, scientists say that you can eat yolks even if you have high levels of “bad” cholesterol. Eggs are well saturated, and as a result, the incoming portion of fat is small if you compare it with the same fatty meat or baked goods.
Gender characteristics
In men, there is an increased volume of brain matter - white and gray. Women have smaller tonsils. Research shows the presence of gender differences in the anatomical organization of the analyzers - auditory and visual. In the male population, an excess of the neuronal resource of the visual cortex is observed. In the female group, the volume of neuronal structures of the auditory cortex was exceeded.
Similar studies served as the basis for the assertion that men perceive external information better with their eyes, and women with their ears. A number of studies have shown the presence in women of large cortical structures responsible for the formation of emotional reactions. In men, interhemispheric asymmetry is more pronounced.
Taking into account the dependence of brain mass on body mass, scientists have identified structural and morphological differences that are related to features of functioning. For example, there are some sex differences in the structure of the brain matter in the post-resuscitation period after experiencing clinical death.
During experiments on animals, it was established that in the population of males and females after resuscitation, different localization and different sizes of areas of damaged nervous tissue are revealed with the same duration of cardiac arrest. In males, a more extensive area of damage is observed, which covers the cerebellum, hippocampus, and segments of the sensorimotor cortex.
In females under similar conditions, damage to the nervous tissue is predominantly detected in the hippocampus. At the same time, females exhibit a less pronounced neurological deficit, and the process of regression of neurological symptoms occurs more quickly.
Other studies after an episode of artificial ischemia, reperfusion (impairment of blood flow) of the brain of various origins and subsequent restoration of blood supply in the medulla also confirmed higher damage to nervous tissue in males than in females.
Recommendations for correcting your diet
It's not just foods with saturated fat that are dangerous.
It has been found that sugar and refined carbohydrates increase the level of bad cholesterol in the blood, so it is important to monitor not so much the amount of fat, which is difficult to eat a lot, but the amount of carbohydrates you consume. To control cholesterol levels in your diet, follow these guidelines: • Eat no more than a couple of egg yolks per day. • Do not eat poultry skin, it contains a lot of fat. • Trim excess fat from red meat before cooking. • Limit portions of poultry and red meat to 80-100g. • Choose low-fat, part-skim cheese or cheese made with 1-2% milk. • Avoid cream-based soups. Instead, choose broth-based soups. • Use low-fat dairy products instead of full-fat cream cheese, sour cream, cottage cheese and yogurt.
Dependence of intelligence on brain size
Scientists, trying to unravel the phenomenon of genius of great people, studied brain parameters, comparing the average weight and other indicators of geniuses and the average adult. At the same time, research is being carried out on the brain of animals. The mass of the brain of animals determines the level of nervous organization; on average, this indicator is proportional to the weight of the body. However, there are exceptions.
For example, the weight of the brain of dolphins is slightly higher than the average value when taking into account the weight of the body. This organ in hippopotamuses and whales is relatively small considering the size of the body. For a sperm whale this figure is 9 kg, for an ant it is 0.00028 g. American scientists conducted an experiment involving animals of different species, for example, a donkey, a giraffe, a bear, a tiger, a hyena, and a panda. In total, representatives of 39 species of the animal world participated in the experiment.
The purpose of the study is to determine whether brain mass and size affect the mental abilities of the little brothers. The animals were faced with the task of opening the latch in a cage within 30 minutes, inside of which lay the food preferred by each species. Bears, raccoons and martens coped with the task best.
Overall, if the bears' performance is not taken into account, the smaller animals performed better on the task, confirming that there is no relationship between the success of smart mammals and brain volume. When asked whether intelligence depends on brain size in humans, scientists answer in the negative. Examples confirm the lack of relationship between these characteristics.
Research shows that brain size and intelligence are not related. For example, the weight of the writer I. Turgenev’s organ was about 2.0 kg. The outstanding theoretical physicist A. Einstein has a similar figure of about 1.2 kg. For comparison, the brain of the revolutionary and Marxist theorist V. Ulyanov (Lenin) weighs about 1.3 kg. Other examples:
- Writer A. K. Doyle - about 0.8 kg.
- Writer A. France - about 1.0 kg.
- Physicist, mathematician K. F. Gauss - about 1.4 kg.
- Poet V. Mayakovsky - about 1.7 kg.
- Composer L. van Beethoven - about 1.7 kg.
- German Chancellor O. von Bismarck - about 1.9 kg.
It is now known for certain that intelligence, talent and wisdom do not depend in any way on the size of the brain matter. The heaviest modern human brain weighed about 2200 g, and its owner was not distinguished by exceptional talents or brilliant intellectual abilities.
The level of mental abilities is influenced by the number of synaptic contacts formed. When a person learns, learns, understands and remembers new information, masters new skills, another synaptic connection is formed. More synapses mean more physical and mental capabilities.
What are unsaturated fats
They are considered the most beneficial for blood vessels and heart muscles, as they increase the level of “good” cholesterol, help reduce inflammation (a risk factor for heart disease), and improve the tone and elasticity of the vascular wall.
The main source of unsaturated fats is plant foods, especially those containing healthy oils. There are two types of fats: mono- or polyunsaturated. Monounsaturated fats are one of the healthiest fats for the human body. They should make up the majority of your daily fat intake. Useful source products will be:
• olive, rapeseed and linseed oil; • most nuts and seeds; • olives; • avocado; • sea fish.
Omega-3 fats are another type of polyunsaturated fat. They help protect against heart disease by lowering triglyceride levels and preventing abnormal heart rhythms (arrhythmia). Helps control blood pressure and reduce the risk of heart attack. To get the most benefit from these foods, eat them 2-3 times a week. The body cannot produce omega-3 fats on its own, so the only sources are foods. The best among them are sea fish: salmon, tuna, mackerel, herring, sardines. Other sources that contain lower amounts of omega-3 fats but are also beneficial:
• flaxseed; • walnuts; • rapeseed oil.
Differences between men and women
It is impossible to answer the question of exactly how much the adult brain weighs without weighing this organ, which is possible only after the death of the subject. At the same time, existing average statistical data can only give an approximate idea of this value.
So, the brain mass of an ordinary middle-aged person ranges from 1100 to 2000 g. This variation is due to various factors affecting the development of the body. It is known that the mass of the human brain depends on the gender, age and race of the individual.
Thus, men may well make fun of the weaker sex about the fact that their brains weigh 100-150 g more, however, this fact does not allow us to judge mental abilities and speaks about the structural features of the central nervous system: in men there is a connection between the perception of reality and coordination movements are better, therefore spatial and motor activity is developed, as evidenced by the development of zones responsible for performing these functions. And women have more developed intuition and associative thinking, which allows them to quickly process incoming information and find easier ways to solve problems.
Fiber and cholesterol
Everyone should have 25-35 grams of fiber in their diet every day. But, unfortunately, the diet of most people does not contain this amount. Dietary fiber is a type of carbohydrate that is not digested. As fiber passes through the digestive tract, it affects nutrient absorption. Its sufficient presence helps reduce the level of “bad” cholesterol. A fiber-rich diet helps control blood sugar levels, promote regular bowel movements, and prevent gastrointestinal diseases. It also helps you control your weight. There are two types of dietary fiber: soluble (viscous) and insoluble.
For maximum health benefits, your diet should include a variety of high-fiber foods. White bread, pasta and fast food are low in fiber. The cleaning and refining process removes the outer husk (bran) of the grain, which reduces the amount of fiber remaining. The best sources of fiber are whole grains, fruits, vegetables and legumes (dried beans, lentils, peas).
Soluble fiber (pectin) absorbs water, swells and turns into a gel. It helps lower total and bad cholesterol levels by binding to bile in the intestines and removing excess cholesterol through body waste. Soluble fiber is found in:
• oat bran and oats; • barley; • legumes (eg dried beans, lentils and peas); • flaxseed; • apples, bananas, pears and citrus fruits; • Brussels sprouts, broccoli, cabbage, sweet potatoes, zucchini. Insoluble fiber promotes bowel regularity, increases bowel volume and softness, helps regulate weight, and prevents many gastrointestinal disorders. Sources of insoluble fiber include: • wheat bran and whole grain bread; • vegetables with veins and rough skin; • nuts.
In addition, drink plenty of water, it helps fiber work, provides fluid to the body and reduces appetite.
How GM research is carried out
There are several methods for studying GM. The oldest method is ablation. This is a rather complex technique that requires a clear understanding of the actions, because its essence is to remove a specific department. By removing one section, you can harm the body and even destroy it. Even small zones contain vital centers. Similar experiments are carried out on animals.
The transcranial magnetic stimulation method allows for a stimulating effect on the brain cortex. Thanks to the small charge, this technique can be performed without fear of causing pain. Modern devices capable of stimulating the brain cortex create impulses that penetrate to a depth of 2 centimeters. TMS can be used not only for research, but also for the treatment of many diseases, including blindness, epilepsy and deafness.
Using an electrophysiological method, small electrical discharges emanating from neurons can be detected. Electrodes attached to the head can be made of metal with insulating material or glass. A special feature of the electrodes is their extremely small thickness, so they can even be inserted into a cell. This is how intracellular potentials are measured. There is also a way to record individual neurons. Sometimes this technique involves inserting electrodes into the brain to record activity over an extended period of time.
There is also a technique of electrical stimulation that allows you to study the human GM by stimulating its individual areas. The result of the research is a cortical homunculus (a map of the cerebral cortex). Moreover, there are methods of magnetic resonance therapy, single-photon emission computed tomography, ultrasound examination and others.
Structural parts of the brain
Computer tomography of the brain
Medulla
The medulla oblongata (lat. medulla oblongata) develops from the fifth cerebral vesicle (additional). The medulla oblongata is a continuation of the spinal cord with impaired segmentation. The gray matter of the medulla oblongata consists of individual nuclei of the cranial nerves. White matter is the pathways of the spinal cord and brain that extend up into the brain stem and from there into the spinal cord.
The anterior median fissure is located on the anterior surface of the medulla oblongata, flanked by thickened white fibers called pyramids. The pyramids taper downward due to the fact that part of their fibers move to the opposite side, forming an intersection of pyramids that form a lateral pyramidal path. The part of the white fibers that do not intersect form a straight pyramidal path.
Bridge
The pons (lat. pons) lies above the medulla oblongata. This is a thickened roller with transverse fibers. The main groove runs through its center, in which the main artery of the brain lies. On both sides of the furrow there are noticeable elevations formed by pyramidal tracts. The bridge consists of a large number of transverse fibers that form its white matter - nerve fibers. Between the fibers there are many accumulations of gray matter, which forms the nuclei of the bridge. Continuing to the cerebellum, the nerve fibers form its middle peduncles.
Cerebellum
The cerebellum (lat. cerebellum) lies on the posterior surface of the pons and medulla oblongata in the posterior cranial fossa. It consists of two hemispheres and a worm that connects the hemispheres to each other. The mass of the cerebellum is 120-150 g.
The cerebellum is separated from the cerebrum by a horizontal fissure, in which the dura mater forms the cerebellar tent, stretched over the posterior fossa of the skull. Each cerebellar hemisphere consists of gray and white matter.
The gray matter of the cerebellum is contained on top of the white matter in the form of the cortex. The nerve nuclei lie inside the cerebellar hemispheres, the mass of which is mainly represented by white matter. The cerebral cortex forms parallel grooves, between which there are convolutions of the same shape. The grooves divide each cerebellar hemisphere into several parts. One of the particles, a fragment adjacent to the middle cerebellar peduncles, stands out more than the others. It is phylogenetically the oldest. The flap and nodule of the worm appear already in lower vertebrates and are associated with the functioning of the vestibular apparatus.
The cerebellar cortex consists of two layers of nerve cells: outer molecular and granular. The thickness of the bark is 1-2.5 mm.
The gray matter of the cerebellum branches into the white matter (on the median section of the cerebellum you can see a branch of an evergreen thuja), which is why it is called the tree of life of the cerebellum.
The cerebellum is connected to the brain stem by three pairs of peduncles. The legs are represented by bundles of fibers. The lower (caudal) peduncles of the cerebellum go to the medulla oblongata and are also called the rope bodies. They include the posterior spinal-cerebellar tract.
The middle (pontine) cerebellar peduncles connect to the pons, through which transverse fibers pass to the neurons of the cerebral cortex. The corticopontine tract passes through the middle peduncle, through which the cerebral cortex acts on the cerebellum.
The upper cerebellar peduncles in the form of white fibers go in the direction of the midbrain, where they are located along the peduncles of the midbrain and are closely adjacent to them. The superior (cranial) peduncles of the cerebellum consist mainly of fibers of its nuclei and serve as the main pathways conducting impulses to the visual thalamus, subtuberculous area and red nuclei.
The legs are located in the front and the tire is located in the back. Between the tire and the legs lies the aqueduct of the midbrain (Aqueduct of Sylvius). It connects the fourth ventricle to the third.
The main function of the cerebellum is reflex coordination of movements and distribution of muscle tone.
Midbrain
The cover of the midbrain (lat. mesencephalon) lies above its lid and covers the aqueduct of the midbrain on top. The lid contains the tire plate (quadrigeminal). The two upper colliculi are associated with the function of the visual analyzer; they act as centers of orienting reflexes to visual stimuli, and therefore are called visual. The two lower tubercles are auditory, associated with orienting reflexes to sound stimuli. The superior colliculi are connected to the lateral geniculate bodies of the diencephalon using superior handles, and the inferior colliculi are connected to the medial geniculate bodies by inferior handles.
The spinal tract begins from the tegmental plate, which connects the brain with the spinal cord. Efferent impulses pass through it in response to visual and auditory stimuli.
Large hemispheres
The medial surface of the human cerebral cortex.
The brain has different hemispheres. The cerebral hemispheres include the lobes of the hemispheres, the cerebral cortex (cloak), the basal ganglia, the olfactory brain and the lateral ventricles. The hemispheres of the brain are separated by a longitudinal fissure, the recess of which contains the corpus callosum, which connects them. The following surfaces are distinguished on each hemisphere:
- superolateral, convex, facing the inner surface of the cranial vault;
- the lower surface, located on the inner surface of the base of the skull;
- the medial surface through which the hemispheres are connected to each other.
In each hemisphere there are parts that protrude most: in front - the frontal pole, behind - the occipital pole, on the side - the temporal pole. In addition, each cerebral hemisphere is divided into four large lobes: frontal, parietal, occipital and temporal. In the recess of the lateral fossa of the brain lies a small lobe - the insula. The hemisphere is divided into lobes by grooves. The deepest of them is the lateral, or lateral, also called the Sylvian fissure. The lateral sulcus separates the temporal lobe from the frontal and parietal lobes. From the upper edge of the hemispheres, the central sulcus, or Roland's sulcus, descends downwards. It separates the frontal lobe of the brain from the parietal lobe. The occipital lobe is separated from the parietal lobe only on the side of the medial surface of the hemispheres - the parieto-occipital sulcus.
The cerebral hemispheres are externally covered with gray matter, which forms the cerebral cortex, or cloak. There are 15 billion cells in the cortex, and if we consider that each of them has from 7 to 10 thousand connections with neighboring cells, then we can conclude that the functions of the cortex are flexible, stable and reliable. The surface of the cortex increases significantly due to grooves and convolutions. The phylogenetic cortex is the largest structure of the brain, its area is approximately 220 thousand mm2.
Age-related changes in the brain
At an early age, the difference between a boy's brain and a girl's brain is minimal; differences begin to appear between 14 and 17 years of age and increase with age.
As the body ages, the human brain “shrinks out,” losing some of its volume. In men and women, this process occurs with significant differences. Thus, in representatives of the stronger sex, the frontal and temporal lobes, the function of which is to control cognitive abilities, emotions and personal characteristics, decrease at the greatest rate. In women, the parietal lobe and the area of the hippocampus, responsible for spatial perception, vision, speech and memory, “dry out” faster. In general, men begin to lose brain volume earlier than their peers. Scientists associate this feature with the protective effect of estrogen on the brain. The most active decrease in brain size in women occurs at the age of menopause, when the production of sexual hormones sharply decreases.
In addition, a woman's brain and a man's brain are susceptible to neurodegenerative changes to varying degrees: women are more likely to develop Alzheimer's disease, and men are more likely to develop Parkinson's disease.
Meninges of the brain
The brain, like the spinal cord, is covered with three membranes: soft, arachnoid and hard.
The soft, or vascular, membrane of the brain (lat. pia mater encephali) is directly adjacent to the substance of the brain, extends into all grooves, and covers all convolutions. It consists of loose connective tissue, in which numerous blood vessels branch that feed the brain. Thin processes of connective tissue extend from the choroid and penetrate into the mass of the brain.
The arachnoid membrane of the brain (lat. arachnoidea encephali) is thin, translucent, and has no blood vessels. It fits tightly to the convolutions of the brain, but does not extend into the grooves, as a result of which subarachnoid cisterns are formed between the choroid and arachnoid membranes, filled with cerebrospinal fluid, due to which the arachnoid membrane is nourished. The largest, cerebelloblongata cistern, is located behind the fourth ventricle, into which the median foramen of the fourth ventricle opens; the cistern of the lateral fossa lies in the lateral sulcus of the cerebrum; interpeduncular - between the cerebral peduncles; cistern crossroads - at the site of the visual chiasm (crossroads).
The dura mater of the brain (lat. dura mater encephali) is the periosteum for the inner cerebral surface of the skull bones. This membrane contains the highest concentration of pain receptors in the human body, while the brain itself has no pain receptors (see Headache
).
The dura mater is built of dense connective tissue, lined from the inside with flat, moist cells, and tightly fuses with the bones of the skull in the area of its internal base. Between the hard and arachnoid membranes there is a subdural space filled with serous fluid.
