General information about human organ systems
A chapter from a very significant scientific publication: "Health and dietary nutrition", a series of lectures published on the occasion of the 160th anniversary of the National Medical University for students of the course "Nutritiology", the course of information and internship "Biological supplements in rational, therapeutic and preventive nutrition" under the editorship of the head of the Department of Food Hygiene of the National Medical University, Doctor of Medical Sciences, Professor, State Prize Laureate V. I. Tsipriyan.
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GENERAL INFORMATION ABOUT HUMAN ORGANS
DIGESTIVE SYSTEM
In the process of digestion, food is converted into energy that the body needs for life. On average, about 10 liters of digested food and liquid pass through the body of an adult every day.
Already in the oral cavity, food is crushed and rubbed with teeth and abundantly moistened with saliva. Saliva irritates the endings of taste fibers and, by wetting food, helps to form a lump that is easy to swallow. Saliva also cleans the mouth.
Careful chewing of food is necessary, since as it is crushed in the oral cavity, it is mixed with digestive juices containing enzymes or enzymes. The more thoroughly the food is chewed, the more fully the digestive functions are carried out at this stage.
After the act of swallowing, the food bolus enters the esophagus. Contractions of the muscle fibers of the pharynx and esophagus allow food to be pushed towards the stomach. In the stomach, food turns into a mushy mass called chyme. Food components such as water and simple carbohydrates are immediately absorbed into the bloodstream.
From the stomach, food slurry passes through a thick muscular ring, which blocks the exit from the stomach, into the duodenum. In the small intestine, the breakdown of carbohydrates, proteins and fats is completed with the participation of digestive juices produced by the pancreas, liver and the small intestine itself.
HOW DIFFERENT NUTRIENTS ARE DIGESTED
2.
Proteins, fats and carbohydrates are very complex macromolecular compounds that are broken down in our body into simpler constituents. During digestion, complex carbohydrates are broken down into simple ones, proteins into amino acids, and fats into fatty acids and glycerol. In this form, nutrients can be absorbed by the blood.
The breakdown of carbohydrates begins in the mouth. Salivary amylase acts on complex carbohydrates and, by converting them into simple ones, makes their absorption by the blood possible. The process continues in the stomach.
The breakdown of proteins begins only in the stomach. It is made possible by the presence of hydrochloric acid and an enzyme called pepsin. Only a small amount of amino acids is absorbed into the blood through the walls of the stomach. Most of this process takes place in the small intestine, where pancreatic juices, which contain the enzymes amylase, trypsin, and lipase, act on the food slurry. Amylase breaks down starches, trypsin breaks down partially digested proteins, and lipase breaks down fats into fatty acids and glycerol.
In addition to these digestive juices, juices secreted by the intestinal walls are involved in the process, which have a similar, although somewhat less powerful effect. Bile produced by the liver enters here through a special duct, the excess of which accumulates in the gallbladder. Bile aids in the digestion of fats. The liver is not only a digestive organ that produces bile, but also a metabolic organ that stores fats, carbohydrates, proteins and vitamins. The liver also absorbs and neutralizes toxins and harmful substances.
About 90% of nutrients are absorbed into the blood through the walls of the small intestine, which are penetrated by a network of blood and lymphatic vessels. From here, nutrients are distributed throughout the body.
Factors that determine the health of the digestive tract.
There are a number of harmful effects on the digestive tract. With frequent excessive filling of the stomach, irregular eating, hasty swallowing and emotional stress, normal digestion is disturbed. In addition, with age, the amount of hydrochloric acid produced by the body, which is necessary for digestion, decreases. The decrease in the amount of hydrochloric acid produced begins at the age of 35 to 45 years. By the age of 55, almost every person has a reduced content of hydrochloric acid.
Heredity is also an important factor in determining the state of the digestive tract. Some people from the very beginning of life are predisposed to diseases of the digestive tract. In this case, any violations of a healthy eating regimen exacerbate the situation.
INTESTINAL TRACT
3.
From the small intestine, food is sent to the large intestine, 1.5-2 m long, approximately 5 cm in diameter, framing the curved small intestine. With muscle contractions of the colon, waste products move towards the rectum, which are then excreted through it.
The large intestine consists of three main parts: the ascending colon, the transverse colon, and the descending colon. Since the digestive process is largely complete by this point, the contents of the large intestine are mostly waste products in liquid form. As the colon contracts and moves along its length, most of the water and mineral salts are absorbed by the body. At the final stage, the waste products are a semi-solid mass, 60-70% of which is water, 10-30% bacteria, as well as insoluble fiber, dead cells and other waste. The intestinal dialysis/excretion process takes 12 to 24 hours. As a rule, the shorter this period, the better. Unfortunately, the diet and regimen of a modern person often leads to an increase in the duration of this period. As it increases, the stool becomes harder and more constipated. Moreover, as the body reabsorbs the liquid components of the contents of the colon, many dissolved toxins also enter the body.
Factors that determine the normal functioning of the intestine.
People who eat large amounts of highly processed foods (including sugar and flour with bleach) that are low in fiber (eg, meat, eggs, dairy products) are particularly susceptible to bowel disease. Thus, diseases of the colon and rectum are more prevalent in the US than in Africa, where the population, on average, consumes seven times more fiber-rich foods than in the US.
For optimal performance, the colon must be moderately full. Fiber, which is part of the food, serves as such a filler. Although fiber does not contain nutrients, it contributes to normal digestion by ensuring that waste products move along the colon in a timely manner. To remove some of the toxins, water would require several times more than fiber, which copes with this task. Fiber ensures the regularity of the intestines and reduces the time spent in the body of various toxins and harmful substances.
BRAIN AND NERVOUS SYSTEM
4.
The brain and nervous system are responsible for processing and storing information, thinking, sleeping, feeling pain, breathing, muscle contractions, the secretion of a number of glands, thermoregulation of the body, and so on. In short, they serve as an important means of communication between us and the outside world. This happens because the sense organs receive information from the outside and transmit it to the brain. There, this information is analyzed, synthesized and transmitted to organs, tissues and cells so that they can adapt to changing conditions.
The nervous system consists of two parts - central and peripheral. The central nervous system consists of the brain and spinal cord, which are made up of nerve fibers. The peripheral system is made up of a network of nerves covering the entire body.
Vital centers are concentrated in the medulla oblongata that regulate the activity of the heart, blood vessels, respiration, metabolism, movement of the head and cervical region, and pupil size. The cerebellum provides coordination of movements and regulation of tone. The cerebral cortex receives, processes signals and sends out a response signal.
The peripheral nervous system, like the circulatory system, permeates all tissues of the human body. It consists of 28 billion neurons, that is, nerve cells that transmit signals to organs through electrical impulses. When impulses enter the executive organ, or effector, responses to irritation occur. If the effector is a muscle, it contracts, if the gland is associated with the digestive tract, digestive enzymes are produced.
Signaling process and stress. The activity of the nervous system is built on the presence of two opposite processes - excitation and inhibition. Part of the activity does not depend on our consciousness, it is involuntary, for example, heart contractions, breathing, digestion, while part of the actions is performed at the will of a person - eating, deciding to go for a walk. The nervous system controls not only the physical functions of the body, but also its response to stress. A good example would be a reaction to an argument or an air flight. Stress is a hormonally stimulated state that prepares the body for the next test, a kind of adaptation reaction to change.
Stress is a factor in everyday life, and the degree of its negative impact is largely determined by how we respond to the stressors around us. In order for our nervous system to be able to cope with the various stresses to which we are constantly exposed, it must be supplied with good nutrition.
Even though everyday stresses may seem insignificant, the combination of them, as research by Dr. Richard Lazarus has shown, can have a stronger effect on our body than such severe impacts as a serious illness, death of loved ones, or financial difficulties.
There is an impression that the nervous system does not distinguish between physical and emotional dangers. So children's crying, criticism from superiors, unpaid bills, traffic jams, non-compliance with deadlines and many other emotional problems are perceived by the nervous system as a danger and cause a response in the body in the form of increased hormone levels, heart palpitations, etc. This defense mechanism can harm the body when it acts constantly and unnecessarily and the mobilized energy is not used for defense or flight.
Prolonged emotional stress can lead to the destruction of health. There is evidence that many of us are bad at coping with stress. In practice, it is estimated that half of the patients who seek medical help have symptoms that were initially caused by psychological stress.
Clearly, emotional stress is not the only cause of disease, and it is not necessarily the main cause. However, emotional stress is one of the risk factors for poor health.
Overcoming stress.
Psychologist Donald A. Tabesing once compared stress to a string being pulled. "To create music, a string must be stretched, but not to the point of breaking."
Fortunately, stress can be relieved and its impact reduced. Exercise, meditation and various relaxation techniques, attitude change and increased nutrition are effective ways to overcome stress.
Since stress affects metabolic processes, there may be an increased need for certain nutrients. For example, an increase in metabolic rate means an increase in carbohydrate consumption. With the consumption of an increased amount of carbohydrates, the need for thiamine and other B vitamins increases.
Stress is directly related to nutrition. The physical response to stress speeds up the metabolic process, which in turn increases the need for antioxidants and a number of vitamins - especially water-soluble ones - which need to be replenished daily. It is for this reason that antioxidants, B vitamins and vitamin C form the basis for preparations aimed at overcoming the effects of stress.
The mechanism of action of the nervous system is electrochemical. Tiny impulses, or currents, travel through the fibers without causing them to move, change color, or appear to change in any way. An electrical oscillation that lasts about one hundredth of a second is transmitted by the release of a special chemical acetylcholine that acts on the membrane of the recipient cell.
ENDOCRINE SYSTEM
5.
The human body has two types of glands - exocrine glands, which secrete special products, secrets, which are excreted into the venous blood through the excretory duct, and endocrine glands, which produce special highly active substances known as hormones. Glands of the endocrine system - pituitary gland, pineal gland, thyroid gland, parathyroid glands, thymus gland (hymus), pancreas, adrenal glands and sex glands (ovaries and testicles). The hormones produced by these glands regulate the process of growth and puberty, control body temperature, activity levels and emotions. They contribute to the restoration of damaged tissues and energy generation. Endocrine glands produce the right amount of hormones for the body. Changes in the amount of hormones produced can be a response to infection, stress, and changes in blood chemistry. The human body has a special mechanism that regulates the amount of hormones. The process may look like this: the endocrine gland produces a hormone, which is then sent to the receptors of the cells of a certain tissue or organ, as a result of which they are able to perform their function. However, in the case of an excessively high level of tissue or organ activity, a feedback occurs, due to which a command is sent to the gland to reduce the amount of hormone produced.
Factors that determine the state of the endocrine system.
The optimal function of the endocrine glands is possible in an organism with a rich content of minerals and, especially, microelements. For example, for normal metabolic processes and secretion of the thyroid gland, a large amount of iodine is needed, and for the functioning of the pancreas, which regulates blood sugar levels, chromium is needed.
The normal functioning of the endocrine glands is facilitated by the consumption of foods rich in trace elements. Unfortunately, most of the food products that form the basis of the diet of a modern person do not contain trace elements.
This is due in part to soil depletion and is a result of food processing. Thus, unrefined sugar loses 94% of chromium and 89% of manganese during processing. Similarly, when processing wheat into flour, the chromium content is reduced by 50%, and manganese by 86%.
Nutritional supplements rich in trace elements, combined with a well-balanced diet, provide the body with the nutrients necessary for the normal functioning of the endocrine glands.
THE IMMUNE SYSTEM
6.
According to one scientist, immunity is the sixth sense organ; it recognizes viruses and bacteria that the brain is unable to identify, and then converts this information into hormones that are sent to the brain in order to activate the immune process.
The immune system works in conjunction with other body defense systems. The skin, for example, forms a physical barrier to foreign matter, while the respiratory system uses the epithelium, mucus, and cough-producing mechanism to remove inhaled microbes and contaminants. In addition, acids in the stomach and protective enzymes produced by the pancreas and intestines destroy many pathogens.
If foreign substances cannot be removed by other defense mechanisms, the immune system comes into play. This system is made up of lymph nodes, blood proteins known as immunoglobulins, and special white blood cells (leukocytes), as well as the organs that produce these cells and the blood vessels through which they are transported.
Lymph nodes, or glands as they are sometimes called, are usually small oval organs about the size of a bean seed. Bundles of lymph nodes are usually located close to veins at important strategic points along the lymphatic vessels at the knee, elbow, armpit, groin, neck, chest and abdomen.
The lymph nodes filter and purify the blood and serve as a collection point for germ-destroying cells during illness. The filtration process prevents bacteria, cancer cells and other pathogenic particles from entering the bloodstream. The lymph nodes are also centers in which some of the white blood cells are produced and stored, namely, lymphocytes and monomes, which are an important part of the body's defense mechanism. When an infection enters the body, the lymph nodes that actively produce lymphocytes increase in size. All parts of the immune system must respond quickly to pathogens and their toxins. If the disease overcomes the protective barriers of the body, the overall body temperature rises, local foci of inflammation appear, and other reactions occur that are designed to resist uninvited aliens. Antibodies (immunoglobulin) play an important role in maintaining normal immunity. Antibodies bind foreign proteins into complexes that are harmless to the body. It is estimated that there are 100 million different types of antibodies in the body, each of which has a specific role to play. The body provides constant resistance to mutant cells (cancer cells). Some immunologists believe that malignant tumors are constantly present in the body, but they are usually identified and destroyed by the immune defense system.
Factors that determine the state of the immune system.
We live in a world saturated with natural and man-made poisonous substances. A polluted environment, combined with unhealthy diets and bad habits such as smoking and lack of rest, can reduce the body's resistance to disease-causing bacteria, viruses, harmful chemicals and other disease-causing factors.
Purdue University nutritionist Thomas Petro, PhD, wrote: "The point is not that immunity is affected by certain nutrients, the point is that it is affected by all nutrients." For this reason, a balanced diet seems to be the most important factor in maintaining the normal functioning of the immune defense system. In addition, it is important to remember that the body is not able to cope with the harmful effects of a lack of a number of minerals.
The role of vitamins A, C and E, which are antioxidants and protect cells from the destructive effects of processes occurring in the body, various chemicals and pollutants, and an unhealthy lifestyle, has been repeatedly emphasized. These vitamins, in combination with the trace element selenium, prevent important molecules and cell formations from reacting with oxygen, which often damages, literally burns, the cell. This process is called oxidation.
RESPIRATORY SYSTEM
7.
The main human respiratory organ is the lungs, the respiratory tract includes the nose, pharynx, larynx and trachea, or windpipe. Air enters the human body through the nose or mouth and through the larynx enters the trachea, which divides into two bronchi, each of which enters the lung. In the lungs, gas exchange occurs, and oxygen from the air sacs, called alveoli, is transferred to the blood vessels. The walls of the alveoli are very thin, they are densely braided with capillaries, which also have thin walls - through this thin barrier, oxygen from the lungs enters the blood, and carbon dioxide enters the lungs from the blood.
A person breathes rhythmically, since breathing is regulated by the respiratory center located in the medulla oblongata. On average, a person inhales and exhales 10-15 times per minute. Inhalation occurs when excitation comes from the respiratory center to the respiratory muscles, that is, to the diaphragm and intercostal muscles, as a result of which they contract, the lungs expand, and air enters them. At the same time, the nerve endings located in the lungs are irritated, excitation occurs in them, it goes to the respiratory center and slows it down - excitation ceases to flow to the respiratory muscles, they relax, exhalation occurs, the lungs subside.
Blood supplies the body's cells with both nutrients and oxygen. Oxygen is needed by cells to obtain energy by breaking down carbohydrates and fats. The by-product of this reaction is carbon dioxide, which is excreted by the lungs.
It works like this: the right side of the heart pumps blood with a high carbonic acid content to the lungs. There, gas exchange occurs and carbon dioxide is replaced by oxygen, which causes a change in the color of the blood - from dark red it becomes bright red - this change indicates that hemoglobin captures oxygen. Then the blood, enriched with oxygen, is sent to the left half of the heart and spreads throughout the body. The carbon dioxide is then expelled when you exhale. The respiratory system reacts to the amount of carbon dioxide in the blood. If its content rises, the respiratory rate increases in order to supply the body with oxygen necessary for energy metabolism.
Factors affecting the respiratory system.
Early in life, people have a pair of healthy, clear, pink lungs. Throughout life, many people, consciously or unconsciously, harm their lungs. It is difficult to overestimate the damage caused in this way. Remember, the respiratory system supplies oxygen to the blood and removes waste gases. Without oxygen, the cells of the body do not have access to energy resources and cannot function. With a decrease in the efficiency of the respiratory system, the speed of the processes occurring in the body slows down.
The main cause of lung damage is tobacco smoke. The most dangerous of the 4,000 substances that make up tobacco smoke are nicotine and carbon monoxide. It is believed that nicotine addiction turns smoking into a stable habit. The consumption of nicotine causes additional secretion of the hormone adrenaline, which in turn raises blood pressure and increases the heart rate. The presence of carbon monoxide interferes with the transport of oxygen, which can cause serious health consequences over time.
Smoking damages the lungs, bronchi, blood vessels, heart, and other organs and tissues. In addition, smoking increases the risk of the following diseases: respiratory infections, pneumonia, cerebral hemorrhage, arteriosclerosis, stomach and intestinal ulcers, cancer of the mouth, throat, esophagus, kidney, bladder and pancreas. Smoking during pregnancy increases the risk of miscarriage and fetal death. Even passive smoking has been shown to increase the chance of respiratory infections and otitis media in children and cause lung cancer and fatal heart disease.
In addition to smoking, airborne pollutants cause significant damage to the respiratory tract. Julius Comrow, a professor at the University of California, calculated that, on average, up to 20 trillion particles of foreign substances enter the respiratory tract of a city dweller per day.
Several mechanisms operate in the respiratory system to deal with such particles. Foreign particles are removed from the airways by coughing and sneezing. The hairs that cover the inside of the nostrils trap irritants and pollutants, bacteria, viruses, fungi, exhaust particles present in the air. However, not all particles are retained here.
The airways contain cells specifically designed to absorb and destroy foreign particles. These particles irritate the tissues, causing them to enlarge and produce additional mucus. The mucous membrane is irritated, swells and closes the nasal passages. If at the same time pathogenic bacteria are in the respiratory tract, diseases such as bronchitis and asthma may occur.
Since the role of oxygen in the body's energy metabolism is so great, it is necessary to take care of the lungs, reducing exposure to a polluted atmosphere as much as possible and satisfying the body's need for proper nutrition.
URINARY SYSTEM
8.
For the formation and excretion of urine in the human body, there are paired organs - the kidneys, from each of which the ureter departs, leading to the bladder. The bladder is connected to the urethra, the urethra (which is longer in men than in women), ending in an excretory opening. These organs are designed to form and excrete waste products in the form of urine, regulate its quantity, acidity and consistency of the body's total water.
The kidneys filter the blood. Every minute, 1/4 of all blood in the body enters the kidneys, which are made up of approximately 2 million microscopic filters called nephrons. Nephrons absorb nutrients, filter out toxins and waste products from the blood. In addition, the kidneys regulate other processes in the body by secreting the hormones renin, erythropoietin, and prostaglandin. Renin contributes to the regulation of blood pressure, and erythropoietin, a hematopoietic factor, stimulates the formation of red blood cells.
Prostaglandin affects not only the function of the kidneys, but also the activity of smooth muscles, helps to remove excess fluid from the body, is necessary for certain temperature disorders and pain, as well as inflammatory processes. In the kidneys, it contributes to the expansion of veins and the formation of urine.
The bladder, located in the pelvis, is designed to store urine until urination. It has three layers of involuntary muscles that provide its ability to expand and contract. Being no larger than the average prune fruit, the bladder expands considerably and is able to hold up to a pint, that is, over half a liter, of urine. The walls of a filled bladder send an impulse to the brain signaling the need to urinate.
Unfortunately, even when you get a significant amount of sodium from food, the kidneys continue to capture sodium and excrete potassium. Since it is obvious that we are not able to change the function of the kidneys, we should change the diet. Since food processing reduces potassium content, you should eat as much fresh food as possible.
Herbal supplements, vitamins and minerals provide the kidneys with the nutrients they need to carry out this challenging task of maintaining acid-base balance.
Urine is 96% water. The remaining 4% is a mixture of urea, salts, sugar, proteins, fats, vitamins and bile pigments. Urine is usually clear and yellow in color, although its color depends largely on diet and health. Urine has a characteristic ammonia smell, which arises primarily from the nitrogen-containing waste products present in it.
Factors that determine the state of the urinary system.
The kidneys are designed to purify the blood. They continuously cleanse the blood of waste products. However, like any complex mechanism, their possibilities are not unlimited. However, the lifestyle of a modern person makes us carry more and more burdens. Drinking water throughout the day helps flush out toxins from the body and may, to some extent, prevent possible complications. The cells of the body require a certain content of a number of salts. For the water balance of the body, potassium and sodium are of particular importance. More than half of the water is inside the cells. The rest of the water contains salts, being a solution, like sea water, washing the cells.
The kidneys are the main regulatory mechanism that maintains the acid-base balance. They remove excess potassium and retain sodium. In the diet of our ancestors, the potassium content significantly exceeded the sodium content. Currently, people eat a significant amount of foods high in sodium, and the amount of fresh foods containing naturally occurring potassium is not enough.
MUSCULOSKELETAL SYSTEM
9.
The human motor system includes a skeleton, i.e. a set of bones and cartilage that make up the skeleton of the body, as well as muscles and connective tissues that provide the ability of the human body to move.
A newborn child has about 350 cartilaginous bones, consisting mainly of ossein. As bones grow, they absorb calcium phosphate and become hard. This process is called calcification, or calcification. In the end, bone tissue is formed, consisting mainly of calcium phosphate, and part of the bones grows together. In the body of an adult, there are from 206 to 209 bones, depending on the presence of one or two additional ribs in the chest and an additional bone in the coccyx.
The deposition of calcium phosphate in bone tissue is carried out in two ways. It covers the outside of the bone, forming a layer called the periosteum, or periosteum. Inside the bone has a spongy structure and is filled with a porous substance. The channels and lumens of the bones are filled with bone marrow. The bone marrow, a kind of "factory" of blood, produces red and white blood cells, which are transported throughout the body by an extensive network of blood vessels.
The active process of bone growth ends at the age of 15 in the female body and 20 years in the male body. However, the process of growth and constant regeneration of bone tissue continues throughout a person's life. There are two types of bone cells: osteoblast and osteoclast. These two types of cells work together to produce new bone on the outside of the bones and remove old, unwanted tissue from the inside. To maintain this process, the body needs to constantly replenish its stores of nutrients such as calcium, phosphorus and vitamin D. When there is a lack of calcium in the blood, the body borrows it from the bone tissue without replacing it later, which ultimately makes the bones porous and weak. This can lead to serious diseases that severely limit a person's capabilities, in particular, to osteoporosis, sometimes with a fatal outcome.
10.
Joints are sometimes called a masterpiece of engineering because they provide a flexible connection for bones that do not touch each other. Joints are formed at the junction of two or more bones and have a lubricating environment that protects them and ensures their ability to function throughout a person's life, allowing him to perform a lot of complex and varied movements.
The design of the joints is varied depending on their function. As for their composition, they all have a connective tissue sheath that produces a synovial fluid that forms a joint lubricant for moving parts. Outside this sheath are ligaments that connect the bones. Ligaments protect the articular bag and control joint mobility. Articular bags and ligaments hold and protect individual parts of the skeleton.
11.
The movements of the body are controlled by the joints and tendons, however, without the muscles they would not be possible, since the muscles convert the energy of nutrients into mechanical energy.
Muscles carry out their function by contractions. The human body has 600 muscles of two main types: smooth and striated. The latter include skeletal and cardiac muscle.
Each muscle consists of muscle fibers, which in turn consist of extremely thin fibers - muscle fibrils - from one to 30 centimeters long. Neighboring fibrils move in opposite directions - this process is called contraction. Small muscles have few fibers, while large muscles can have a very high number.
Muscles are strengthened through activity. With muscular effort, the heart pumps more blood containing nutrients to the muscle. As a result, during muscle activity, the muscles are strengthened and enlarged.
Factors that determine the state of the musculoskeletal system.
For the optimal functioning of the musculoskeletal system, constant vigorous activity is necessary. If a person leads a motionless lifestyle, he does not form a sufficiently strong skeletal system. In the case of a transition from an active lifestyle to a stationary one, the skeletal system eventually undergoes changes that are unfavorable for the body.
For the musculoskeletal system, proper nutrition is very important. As already mentioned, a prolonged lack of calcium in the body can lead to the most deplorable consequences. So in the US, older people most often suffer from diseases caused by a lack of calcium. Disorders of the skeletal system usually begin at the age of 35 and have a particularly detrimental effect on women's health. As menopause approaches, skeletal system disorders intensify, which is facilitated by a decrease in the content of estrogen, hormones that support bone mass. An estimated 5 million women in the United States suffer from bone disease. Men should also be involved in the prevention of diseases of the skeletal system, although among men the number of diseases of the skeletal system is five times lower. The daily dose of calcium for an adult recommended by the US Department of Health is at least 1200 mg. Since it is difficult to obtain this amount of calcium from food, and foods that are a source of calcium often cause allergies, it is recommended to take dietary calcium supplements.
Although the skeleton of an adult weighs a little over 9 kg, it is able to withstand enormous loads. This is due to the fact that the bones that make up the skeleton are distinguished not only by hardness, but also by elasticity. The elasticity of bone tissue is 20 times greater than the elasticity of steel.
SKIN AND HAIR
The skin separates the internal organs from the external environment. The skin is the largest organ of the human body in terms of area, which is constantly exposed to the environment. The skin is a waterproof barrier that protects internal, more vulnerable organs, does not allow toxins and sources of infection to enter the body from the external environment. At the same time, the skin regulates body temperature and helps to excrete some of the body's waste products.
The skin consists of three main layers - the epidermis, the outer layer, the skin proper, or dermis, and the subcutaneous layer. The epidermis can be divided into two layers: the top layer of the epidermis is made up of dead keratinized cells and a protein called keratin; below is the layer of the epidermis containing keratin and melanin. The amount of melanin determines the color of a person's skin.
The dermis contains hair roots, blood vessels, nerve fibers, muscle tissue, sebaceous and sweat glands. The connective tissue of the dermis contains collagen, a protein substance also present in bone tissue. Collagen, together with elastin, provides tone and a healthy look.
Fats are deposited in the connective tissue of the subcutaneous layer. This allows you to regulate body temperature and protects the body from damage.
12.
Hair is an elastic fiber made up of keratin. Only the hair root, located in the dermis, is its living part. On average, there are approximately 100,000 - 200,000 hairs on a human head, and their number can vary greatly from person to person. Hair on the head grows at a rate of approximately 1 cm per month, the duration of each hair on the head is from 2 to 6 years. Then, after a period of about 3 months, the hair falls out. Eyebrow and eyelash hair grows for 10 weeks, followed by a rest period of 9 months. At any given moment, 90% of the hair on your head is in a state of growth, and 10% is resting. Usually a person loses 30-200 hairs per day. However, due to emotional stress, this number can increase to 500 per day. Hair falls out also due to the experienced state of physical or emotional stress.
Each hair consists of three layers, in the hair shaft there is a pigment that determines its color. The shape and size of the hair root determines its appearance. Straight hair has a round cross section, while curly hair has a flat or oval cut. The density of hair depends on the number of roots per square centimeter, and the width of each hair depends on whether a person's hair is thin or not.
13.
Nails on the hands and feet are keratinized cells of the epidermis, consisting of keratin. Many mistakenly believe that nails contain a lot of calcium. This is not true. In fact, keratin contains a lot of sulfur. The nail consists of three main parts: the root, the nail itself, and the tip that protrudes beyond the tip of the finger. Nails grow more slowly than hair on the head, at about 2.5 mm per month; on the hands they grow about four times faster than on the legs. It is not known why nails grow more slowly in winter, as well as in childhood and old age. Nails are considered indicators of a state of health, and strong changes in their surface, shape, color, growth rate may indicate the need to seek medical attention.
Factors affecting the condition of the skin, hair and nails.
Skin type is determined primarily by genetic factors. Some people have beautiful skin from the moment they are born, while others experience various problems all the time. However, heredity is not the only factor. Skin condition is affected by diet, exercise, rest and stress. The climate in which a person lives has a great influence on the appearance of the skin. People living in warm regions are naturally more exposed to the sun. Skin cells absorb the sun's rays and produce large amounts of vitamin D.
The result is a beautiful tan. However, it should be remembered that excess sun exposure can provoke skin cancer, especially in people with very fair skin. In addition, exposure to sunlight can cause premature aging of the skin.
Skin care starts with proper nutrition: Eat plenty of fresh fruits, vegetables, and whole grains. It is necessary to drink plenty of clean water, which helps to moisturize the skin and flush out toxins.
Obesity makes a person prone to eczema, allergies, fungal diseases, to a large extent due to excessive sweating. In this case, violations in the protective mechanisms of the body usually occur.
When falling into the other extreme, with insufficient calorie intake, the skin becomes withered, dry, coarsened, colorless. For healthy skin and hair, along with rest and physical activity, you need an adequate supply of nutrients, including B vitamins, vitamins C, A, K, fatty acids, the mineral zinc, iron and proteins. Stress is a big threat to the skin.
It is necessary to engage in daily skin care in accordance with a carefully designed scheme. The use of nourishing and protective agents, the removal of excess sebum and impurities from the surface of the skin allow you to maintain a healthy appearance of the skin.
Like the condition of the skin, the condition of the hair depends on nutrition, cleanliness and lack of stress. Proper nutrition contributes to a healthy look of hair, while hair loss can be a sign of anemia or hormonal disorders. It should be remembered that although the self-renewal cycle of the skin on the head is on average one month, sometimes this process is greatly accelerated. As a result of the death and exfoliation of the upper layers of the skin, dandruff occurs.
The nails are affected by the ingress of strong chemicals (as part of detergents), constant exposure to liquid. Nutrition is an important factor. Protein deficiency in the diet causes discoloration of the nails, iron deficiency - the formation of hollows on the nails.
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