Encyclopedia of Family Medicine

Chapter 1 Human Body and Nutrition (1)
Life is divided into nine periods
A person's life is divided into the following periods:
Fetal period: more than 9 months from conception to delivery.

Neonatal period: from birth to 1 month.It is a period of adaptation for children to transfer from the fetal environment to the external environment.The newborn should pay attention to nursing, feeding, keeping warm, and preventing disease infection.

Infant period: from full moon to 1 year old, also known as breastfeeding period.Generally, breast milk is the main food, and the growth and development are particularly fast.At the age of one year, the weight increased by 2 times compared with that at birth, and the height increased by half.Attention should be paid to feeding during infancy, and supplementary food can be added from 4 months onwards. At the same time, attention should be paid to preventing infectious diseases and cultivating hygienic habits.

Early childhood: from 1 full year old to 6 or 7 years old. 1 to 3 years old is the early childhood period, also called the nursery period.From 4 years old to 6, 7 years old is the later stage of early childhood, also called kindergarten or preschool.Children in early childhood should pay attention to nutrition, take part in more outdoor activities, prevent infectious diseases, prevent accidental injuries, and cultivate hygiene habits.For preschool children, we should actively inspire and induce them according to their lively, curious and imitative characteristics, do more group games and outdoor activities, and encourage them to participate in physical exercise to prepare for school.

Primary school childhood: from 6, 7 years old to 12, 13 years old.During this period, children should reasonably arrange study, labor, cultural and sports activities, etc., so that they can gradually adapt to the intense and rhythmic life inside and outside the school.

Adolescence: From 12, 13 years old to 15, 16 years old, also known as puberty.Accelerated growth and development, attention should be paid to strengthening health education.

Adolescence: From 15, 16 to 23, 24 years old.It is the stage of transition from teenage to adulthood.Various physiological functions gradually mature.

Middle age: from 25 to 60 years old.

Old age: over 60 years old.

The human body is made up of 25 elements

What is the human body made of?Fundamentally, the human body is made of elements.Among the 107 elements found in nature, about 25 make up the human body, among which the four elements of hydrogen, oxygen, carbon, and nitrogen account for 99% of the total number of elements in the human body.Atoms of these elements are arranged in a specific way to form molecules, molecules are combined to form cells, cells are combined to form tissues, tissues form organs, and organs form systems, thus forming a highly complex human body.

The various elements that make up the human body exist in the form of compounds in the body, and these compounds are divided into two categories: inorganic compounds and organic compounds.Inorganic compounds include water and inorganic salts; organic compounds include sugars, proteins, fats, nucleic acids, and vitamins, among others.

Cells are the most basic units that make up the human body.Such as sperm cells, egg cells, muscle cells, etc., the total number of cells that make up the human body is more than one billion.

Countless cells combine to form four basic tissues in the human body: epithelial tissue, connective tissue, muscle tissue and nervous tissue.

Different fits of the four basic tissues.Constitutes various organs in the human body, such as the heart, liver and so on.Each organ has its own specific shape and function.

An organ can only perform a certain function, and many organs combine to perform a full set of functions in a certain aspect.It constitutes the organ system, referred to as the system.Such as the mouth, esophagus, stomach, intestines, liver, pancreas, etc. combine to constitute the digestive system.to complete the work of food digestion and absorption.The human body has 8 systems, namely: digestive system, nervous system, respiratory system, circulatory system, motor system, endocrine system, urinary system and reproductive system.

Under the command of the nervous system, all the tissues and organs of the whole body cooperate with each other to form a harmonious balance between the whole body and the external environment, and carry out a normal life.

The brain is the headquarters of the human body

Physically, human beings are very ordinary.Not as strong as a cow, not as good as a deer, not as sensitive as a cat, not as good as a dog, not as good at swimming as a fish, not as flying as a bird, not as productive as an insect... In a word, the human body seems to be very clumsy.However, man has become the ruler of the earth because he has an important specialized organ - the brain.

The human brain is divided into three parts: cerebrum, cerebellum, and brainstem.Subdivisions in the brainstem include the thalamus, midbrain, pons, and medulla.The brain is the highest part of the human nervous system, and it is also the most developed part of human beings beyond other animals.

The average weight of the brain is about 1374 grams. There are many wrinkles on the surface, forming many grooves (sinking parts) and gyri (protruding parts), which increase the surface area.The 2-5 mm thick layer on the surface of the brain is gray and is mainly composed of about 140 billion nerve cell bodies. This is the cerebral cortex, the highest command of the human body.Numerous nerve fibers are intricately connected among these numerous nerve cells.Someone once made an analogy: Even if everyone in the world installed a private telephone, the switchboard in this world would not have as many circuits as the human brain.Complex physiological and psychological activities such as human thinking, consciousness, emotion, and behavior are carried out in this neuronal network that is less than half a centimeter deep and less than 1/4 square meter wide.

Each hemisphere of the human brain is divided into five lobes: the largest is the frontal lobe, which is in charge of thinking, judgment, memory, personality and other functions; the lower part of the two sides is the temporal lobe, which is the storehouse of human memory and the high-level auditory center. The temporal lobe; the top part is called the parietal lobe, which is related to body sensation; the occipital lobe, which is located at the back, is in charge of vision; the deep lobe is called the insular lobe, which is smaller and is in charge of taste, gastric motility, visceral sensation and Sports and other functions.

The concept of nerve center

The various parts of the cerebral cortex work in a division of labor.The nerve cells in charge of a certain function are distributed in a relatively concentrated part, which is the nerve center.For example, the precentral gyrus located in the frontal lobe mainly manages the movement of the body and is the location of the motor center.Located in the central posterior gyrus of the parietal lobe, it mainly manages the sensation of the body and is called the sensory center.

Both hemispheres of the brain have a motor center and a sensory center, but it is worth noting that the motor and sensory centers of the left brain are in charge of the motor and sensory functions of the right body, and likewise, the right brain is in charge of the left body.

The auditory center is located in the temporal lobe of the brain.There are also olfactory centers and taste centers in the temporal lobe.

Stimuli received by the eyes are sent to the visual center in the occipital lobe of the brain.

The respiratory and circulatory centers are located in the oblongata, and these two centers are called life centers.

The language center is a center that involves a wide range of areas of the brain.Humans are the only ones who can communicate through language.Language is a complex function.If the "motor language area" of the frontal lobe is damaged, people can read and understand words, but they cannot write and speak; if the "listening language area" of the temporal lobe is damaged, people can speak, write, and understand words. But can't understand other people's conversations; damage the "visual language area" of the parietal lobe, people can listen and speak, although the eyesight is good, but can not understand the meaning of words.It can be seen that the whole set of speech functions of listening, speaking, reading and writing is completed by the synergy of various nerve centers in the cerebral cortex.

distribution of cranial nerves
Some nerve fibers are directly separated from the brain stem of the human brain and distributed to the internal organs of the head, neck and chest. These nerves are called cranial nerves, and there are 12 pairs in total: ① olfactory nerve; ② optic nerve; ③ oculomotor nerve; ④ trochlear nerve; ⑤ trigeminal Nerve; ⑥ abducens nerve; ⑦ facial nerve; ⑧ auditory nerve; ⑨ glossopharyngeal nerve; ⑩ vagus nerve; accessory nerve; hypoglossal nerve.

The distribution and functions of the 12 pairs of cranial nerves are introduced below:

(1) Olfactory nerve: The olfactory nerve is distributed in the sensory cells of the nasal mucosa. When a person has a cold, the sense of smell fails because of swelling of the nasal mucosa cells.

(2) Optic nerve: Nerve fibers are distributed in the retina of the eyeball, and the optic nerve enters the cranial cavity through the opening of the sphenoid bone, and conveys vision to the visual center of the brain.

(3) Oculomotor nerve: Together with the 4th and 6th pair of cranial nerves, it innervates eye movement, and it innervates the oculomotor minor muscle, eyelid dermatome and pupillary constrictor muscle.

(4) Trochlear nerve; innervates the superior oblique muscle of the eye.

(5) Trigeminal nerve: It is the largest pair of cranial nerves, divided into three branches: ophthalmic nerve, maxillary nerve and mandibular nerve, which manage the sensory and masticatory muscles of the head and face.Injury to the trigeminal nerve can cause severe trigeminal neuralgia.

(6) abducens nerve: innervates the lateral rectus muscle.

(7) Facial nerve.Manage facial muscles, sense of taste and saliva secretion, facial paralysis occurs when the facial nerve is damaged, and the face appears asymmetrically distorted.

(8) auditory nerve.Responsible for hearing and body balance functions.

(9) Glossopharyngeal nerve; in charge of swallowing and taste, but also regulates blood pressure and heart rate together with other nerves.

(10) VAGAL NERVE.It is the longest and most widely distributed nerve among the 12 pairs of cranial nerves, and it controls the sensation, movement and glandular secretion of the respiratory and digestive systems and the heart.

(11) Accessory nerve: Innervates neck muscle activity.

(12) Hypoglossal nerve: Innervate tongue muscle activity.

spinal cord and spinal nerves
The spinal cord is located in the spinal canal, shaped like a bright white long ribbon, and the length of the spinal cord of an adult is about 45 cm.

The spinal cord has two distinct parts:

White matter: Located around the spinal cord, mainly composed of nerve fibers.

Gray Matter: Located in the core of the spinal cord, gray matter contains the motor roots of the spinal nerves and their cell bodies, which innervate the muscles of the body.The polio virus mainly damages the polio and causes the muscles to lose motor function. Polio is also called polio.

脊髓的两边伸出神经纤维，聚集成一条条脊神经，共31对：即8对颈神经、12对胸神经、5对腰神经、5对骶神经和1对尾神经。

Sensory fibers in the spinal nerves transmit sensations from the whole body to the central nervous system, and motor fibers control the movement of glands and muscles.

The spinal nerves form the cervical plexus and the brachial plexus in the neck. The nerve fibers of these two plexuses mainly innervate the muscles of the scapula and upper limbs. The larger nerves from these two plexuses include radial nerve, median nerve and ulnar nerve. nerves etc.

The lumbosacral spinal nerves form the lumbosacral plexus, and the main nerves from this plexus are the femoral and sciatic nerves.If the femoral nerve is damaged, the knee joint cannot be straightened, the flexion of the thigh will be reduced, and the anteromedial part of the leg will lose feeling.If the sciatic nerve is damaged, the foot will sag, and the leg will be raised high to prevent falling when walking, as if walking forward, and the back of the leg and the feeling of the foot will be lost.

The role of the autonomic nervous system

The brain and spinal cord make up the central nervous system of the human body. 12 pairs of cranial nerves and 3 pairs of spinal nerves constitute the peripheral nervous system of the human body.

Most of the nerve fibers in the human peripheral nervous system belong to the involuntary nervous system. The involuntary nervous system is the autonomic nervous system, also called the autonomic nervous system. This nervous system regulates the functions of most organs in the human body.

The functions of many organs in the human body are completed automatically, which are called vegetative functions, such as the automatic peristalsis of the gastrointestinal tract to push the chyme forward, the pupils will dilate in the dark, and they will shrink when exposed to bright light, and the arterial pressure will be reduced. The regulation of glandular secretion function, and the maintenance of the main functions of life.Such as breathing, blood circulation, digestion, metabolism and so on.

Some diseases cause the human body to lose consciousness and motor functions, and only retain the vegetative functions, so that life can continue. This is what is usually called a vegetative person.

The autonomic nervous system includes two kinds of sympathetic nerves and parasympathetic nerves. The transmission substances released by these two nerves are different, and the results produced are just opposite and resist each other.

The main chemical mediator released by sympathetic nerves is norepinephrine; the main chemical mediator released by parasympathetic nerves is acetylcholine.

The sympathetic nerves of the human body are excited during mental stress and strenuous exercise, which mainly produces the following phenomena: increased arterial pressure, accelerated heartbeat and respiration, dilated pupils, erect hair, increased sweating, and inhibited gastrointestinal digestion.This is the reason why people don't want to eat when they are nervous.

When people have nothing to do and no pressure, the parasympathetic nerves are excited, and the main performance is the opposite of the above.

Adaptation of nose and sense of smell

The nose is divided into two left and right nasal cavities, separated by a nasal septum in the middle. On the outer walls of the two nasal cavities, there are three protruding parts called upper, middle and lower turbinates. The entire nasal cavity is covered by mucous membranes.

The nose is our olfactory organ, and the sense of smell is produced by the olfactory cells that transmit the sensed odor to the olfactory center of the brain through the olfactory nerve.

On the mucous membrane within about 5 square centimeters at the top of the nasal cavity, there are about 500 million olfactory cells (Schulzer cells), which are called olfactory receptor areas.

There are 2-6 olfactory cilia on each olfactory cell. The olfactory cilia extend into the mucus on the surface of the mucous membrane and feel the stimulation of chemical molecules in the air, thus producing the sense of smell.

Because the sense of smell is produced by stimulating the olfactory cells with substances in the air that can cause the sense of smell.Therefore, the substances that can cause the sense of smell must meet the following conditions: easy to volatilize; soluble in water; soluble in oil.

In a person's life, the most sensitive period of smell is 10 to 50 years old. Cell development was found to be incomplete before the age of 10.After the age of 50, the olfactory mucosa begins to shrink again, and the number of olfactory cells also begins to decrease.

When a person suffers from a cold, the mucous membrane in the olfactory receptor area swells, and it is difficult for the smell to stimulate the olfactory cells, so it is inevitable for cold patients to be unable to distinguish the smell.

The sense of smell has a characteristic, that is, it is very adaptable.We may have such an experience that when we arrive at a fragrant place, we start to feel the aroma, but after a while, we can't feel any aroma. This is called the adaptation of the sense of smell in physiology.There is a proverb in our country: "It takes a long time to enter the room of chili orchid without smelling its fragrance, and it takes a long time to enter the room of abalone without smelling its odor", which is a vivid description of the adaptive characteristics of olfactory sense.

The composition of the ear

The ear is divided into three parts from the outside to the inside: the outer ear, middle ear and inner ear.

The outer ear is the auricle and the external auditory canal that can be seen from the outside. It is an organ that gathers external sounds.The external auditory canal is 2-5 cm deep and 3 cm in diameter. There are many small hairs on the skin of the external auditory canal, and there are many sebaceous glands and cerumen glands that secrete sebum and cerumen (earwax).Cerumen can kill bacteria and inhibit the growth of mold, and it also has the effect of sticking small bugs that break into the external auditory canal.At the bottom of the external auditory canal is a membrane with an area of ​​about 0 square millimeters and a thickness of only 6/90 millimeter, which is the tympanic membrane.

From the tympanic membrane to the inside is the middle ear, which is located in the cone of the temporal bone, including a tympanic cavity and an ossicular chain composed of three ossicles, which communicate with the outside world through the Eustachian tube.The middle ear is a transfer station that transmits the sound gathered by the outer ear to the inner ear. It is composed of three smallest bones in the human body: malleus, incus and pedal bone.The outer end of the ossicular chain is connected to the tympanic membrane, and the inner end is connected to the inner ear.When the tympanic membrane is vibrated by external sound, the ossicular chain vibrates accordingly, and then transmits the vibration to the auditory cells of the inner ear, and then transmits the vibration to the auditory center of the brain through the auditory nerve.This is how the human sense of hearing is produced.

The middle ear has the Eustachian tube leading to the nasopharynx, so the middle ear is filled with air.The Eustachian tube is usually closed. When speaking, opening the mouth and swallowing, the Eustachian tube opens and the air inside and outside is connected to balance the pressure inside and outside the middle ear.

The main part of the auditory organ in the inner ear, including the cochlea, vestibule, and three semicircular canals.The cochlea is the seat of the ear nerve cells and is in charge of hearing.The vestibule and semicircular canal are responsible for the balance function, called the balance organ.The organ of balance senses relative positional movements of the head and other parts of the body, as well as changes in speed of these movements.If the balance organ is out of balance, people will feel dizzy and their hearing will be affected to some extent.

The composition and function of the tongue
The tongue functions to speak, stir food, and perceive taste.

Taste receptors are taste buds.There are about 5000 taste buds on our tongue.What is interesting is that the taste buds in different parts have a certain division of labor. The taste buds for sweet taste are mainly distributed on the tip of the tongue; the taste buds for sour taste are mainly distributed on both sides of the tongue; the taste buds for bitter taste are mainly distributed in the root of the tongue; The taste buds near the front are particularly sensitive to salty tastes.

The sense of taste is particularly sensitive in childhood. This is because not only the number of taste buds is large, but also the taste buds are widely distributed in the oral cavity. There are also a small number of taste buds on the oral mucosa and the back wall of the pharynx.As we grow older, the number of taste buds gradually decreases, and in old age, the sense of taste will inevitably become dull.

Taste buds are a specialized group of cells located under the mucosa of the tongue.There are small holes in the mucous membrane that communicate with the outside world, called taste holes.Taste cells have cilia at the top, called taste hairs.Taste hairs extend to the surface of the tongue through taste holes, and taste is produced by feeling the stimulation of chemical components in food by taste hairs.Some people use a tongue scraper to scrape the surface of the tongue after brushing their teeth, which can easily damage the taste buds.

Taste buds are capable of hundreds of different flavors.These tastes are created by combining four different original tastes: sweet, sour, salty and bitter.

舌头前面2／3的味觉由第7对脑神经——面神经向脑部传递，后面1／3由第9对脑神经——舌咽神经向脑部传递。

structure of the skin

The skin is the largest and heaviest tissue in the human body.The total area of ​​adult skin is about 1 to 5 square meters, and its weight accounts for about 2% of human body weight.

The structure of the skin is extremely complex. From outside to inside, there are epidermis, dermis and subcutaneous connective tissue containing sweat glands, sebaceous glands and nerve endings.

In addition to a variety of sensory functions, the skin plays an extremely important role in protecting the body from external damage, metabolism, and regulating body temperature.

The sensory functions of the skin mainly include touch, pain, cold and heat.When subdivided, the various senses of the skin are more complicated, for example, the sense of touch can be divided into sense of touch and sense of pressure.When an external object touches our skin, if the contact is very slight and does not cause skin deformation, the sensation produced is tactile.If the contact is heavy, causing the skin to deform, the resulting sensation is that of pressure.Hairy skin is more sensitive to touch because of the abundance of sensory nerve endings around the hair follicles.On hairless skin, the sense of touch is felt by touch receptors in the skin called haptic bodies.The most sensitive parts of the human body are the fingertips and the tip of the tongue, and the most insensitive parts are the back and calves.

Pain is also more complex.If the external stimulus is relatively mild, it will often cause itching, and if the stimulus continues to increase, it will produce pain.

(End of this chapter)