Questions at the beginning of the paragraph.
Question 1. What qualities of bone ensure its lightness and strength?
Bone is the main element of the skeleton of vertebrates and humans. Bone, together with joints, ligaments and muscles, attached to bone by tendons, forms the musculoskeletal system. During life, the bone is rebuilt: old cells are destroyed, new ones develop.
Bones are hollow. This structure of long bones ensures their strength and lightness at the same time. It is known that a metal or plastic tube is almost as strong as a solid rod of the same material that is equal in length and diameter.
In addition, where, with a large volume of bone, it is necessary to maintain its lightness and strength, there is a spongy substance, which is even stronger than the tube, but is light due to its porosity.
Question 2. Why is bone tissue classified as connective tissue?
Connective tissue is tissue of a living organism that is not directly responsible for the functioning of any organ or organ system, but plays a supporting role in all organs, making up 60-90% of their mass. Performs supporting, protective and trophic functions. Connective tissue forms the supporting framework (stroma) and the outer covering (dermis) of all organs. The common properties of all connective tissues are their origin from the mesenchyme, as well as their support functions and structural similarity.
Most hard connective tissue is fibrous: composed of collagen and elastin fibers. Connective tissue includes bone, cartilage, fat and others. Connective tissue also includes blood and lymph. Therefore, connective tissue is the only tissue that is present in the body in 4 types - fibrous (ligaments), solid (bones), gel-like (cartilage) and liquid (blood, lymph, as well as intercellular, spinal and synovial and other fluids).
Questions at the end of the paragraph.
Question 1. Why are the skeleton and muscles classified as a single organ system?
The skeleton and muscles are classified as a single organ system, since they function together, determining the shape of the body, providing support, protective and motor functions.
Question 2. What are the supporting, protective and motor functions of the skeleton and muscles?
The supporting function is that the bones of the skeleton and muscles form a strong frame that determines the position of the internal organs, which prevents them from moving.
The protective function is to protect internal organs. For example, the rib cage covers the heart and lungs, Airways, esophagus and large blood vessels.
Motor function is manifested under the condition of a clear interaction between the muscles and bones of the skeleton, since the muscles set bone levers in motion.
Question 3. What is chemical composition bones? How can you find out the properties of its components?
The composition of bones includes inorganic substances (primarily mineral salts - calcium and phosphorus salts) and organic substances (proteins, fats, carbohydrates). Inorganic substances give bones hardness, and organic substances give firmness and elasticity.
The properties of inorganic and organic components of bone can be determined experimentally. If a bone is set on fire, it will turn black from the carbon left over from the combustion. organic matter. If the carbon also burns out, a white residue will be left, extremely hard but brittle. This is a bone mineral.
To determine the properties of organic substances from the bone, it is necessary to remove mineral substances using of hydrochloric acid. The bone will retain its shape. But the properties of the bone will change. It will become flexible and can be tied in a knot. Consequently, the flexibility of bone depends on the presence of organic substances, and hardness - on inorganic substances.
Question 4. Explain why bone curvatures occur more often in children, and fractures in older people.
Children's bones are rich in organic matter, so they rarely break, but are often deformed. This may be affected by incorrect posture or uneven static load. With age, the content of organic substances in the bones decreases and the proportion of mineral substances increases, as a result of which the bones become more fragile.
- Lesson on the topic:
- "Musculoskeletal system. Structure, composition and properties of bones"
The purpose of the lesson: study the composition and functions of the musculoskeletal system, chemical composition, structure and properties of bones.
Lesson objectives:
educational: to develop knowledge about the composition and functions of the musculoskeletal system; to form in students knowledge about the characteristics of the chemical composition, structure and properties of bone, ensuring the performance of the functions of the musculoskeletal system.
developing: develop the ability to analyze, compare, and draw conclusions; develop logical thinking (establish cause-and-effect relationships, confirming on given subject material the dependence of the properties of an object on its composition and structure);
educational: to foster a sense of responsibility for maintaining one’s health (to form students’ ideas about the need to monitor their posture and nutrition).
Equipment: cuts of tubular bones, microscope, ready-made microspecimen “Bone tissue”, calcined and decalcified bones, presentation for the lesson, student technological maps
- During the classes
1. Organizational moment.
2. Updating students’ knowledge, motivation.
3. Explanation of new material.
3.1.1. Composition and functions of the musculoskeletal system.
3. 2. Chemical composition of bone. Demonstration of experience.
3.3. Bone structure.
3. 3.1. Macroscopic structure of bone.
Working with saw cuts.
3.2. Microscopic structure of bone. Laboratory work “Microscopic structure of bone.”
4. Consolidation and generalization of the material covered.
5. Homework.
- 1. COMPOSITION AND FUNCTIONS OF THE MUSTOCULAR SYSTEM
Teacher.“Movement is life,” noted Voltaire. We make many different movements, move in space, run, walk, jump, swim. We perform many thousands of different straightening, bending, and turning movements. The musculoskeletal system provides all this.
8 Film screening (1 minute)
The musculoskeletal system is often called the musculoskeletal system. Why? Because the musculoskeletal system includes bones, connective tissues and muscles that connect them. The bones of the skull, torso and limbs form the skeleton (from the Greek “skeleton” - “dried”).
The bones of the skeleton make up passive
?Teacher. Guys, what does “passivity” mean?
Suggested answer. Lack of own actions
Teacher. That's right, the bones are not moved by themselves, but by the contraction of the muscles attached to them.
Muscles make up active part of the musculoskeletal system.
The skeleton and muscles function together. They determine the shape of the body, provide support, protective and motor functions.
1.Mechanical functions.
Support function
? Teacher. Guys, what is a support?
BY.Support
Teacher.What does the musculoskeletal system support?
BY.The human body
Teacher. That's right, the musculoskeletal system provides support for the body as a whole, as well as for all its parts and organs. Supportive function - manifests itself in the fact that the bones of the skeleton and muscles form a strong frame that determines the position of the internal organs and does not allow them to move.
Motor function carries out movement of the body and its parts in space. Motor function is possible only if the muscles and bones of the skeleton interact, since the muscles set bone levers in motion.
Protective function.
Skeletal bones protect organs from injury. Thus, the spinal cord and brain are located in a bone “case” - the brain is protected by the skull, - the spinal cord. The rib cage covers the heart and lungs, airways, esophagus, and major blood vessels. The organs of the abdominal cavity are protected from behind by the spine, from below - pelvic bones, in front - by the abdominal muscles.
2.Biological functions.
Along with mechanical functions, the skeletal system performs a number of biological functions. The bones contain the main supply of mineral salts: calcium, phosphorus. They are used by the body as needed, so the skeletal system takes a direct part in mineral metabolism. The bones contain red bone marrow, which is involved in hematopoietic processes.
- 2. CHEMICAL COMPOSITION OF BONE
Teacher. Everyone knows about the existence of bones in our body. Crossbones and a skull were used by pirates as a sign to scare away those who were overly inquisitive. IN fiction many skulls and skeletons. Most often they introduce an atmosphere of mystery into the story. The skeleton also works in fairy tales. The Old Slavonic word “koshch” (“kosht”) means “dry.” From him came the word “bone” and the name of the character in Russian fairy tales - Koschey the Immortal. It is not by chance that this name was given to it - bones “outlive” a person for a long time and are sometimes preserved in the ground for thousands of years, almost unchanged.
Study the data and draw a conclusion about the strength of bone tissue “how building material» human skeleton
| Material | Compressive strength | Tensile strength |
| Steel | ||
| Porcelain | ||
| BONE | ||
| Granite | ||
| Concrete |
Conclusion: Surprisingly, bone is second only to durum varieties steel and turns out to be much stronger, which have become examples of strength, granite and concrete.
Let's find out step by step what features of the chemical composition and structure give bones such unique properties.
Teacher. The substances that make up bone can be divided into two groups: organic and inorganic.
? Teacher. Remember what mineral elements make up bone?
BY.Calcium, phosphorus, magnesium
Teacher. That's right, the composition of bone mainly includes calcium and phosphorus salts.
Teacher. What organic substances can be part of bone tissue?
BY.Proteins fats carbohydrates.
Let's see which properties are given to bone by inorganic substances and which by organic substances.
Demonstration of experience
Teacher. Two days ago I placed a chicken bone in a 10% hydrochloric acid solution. It is a chicken bone, because... it is smaller than, for example, cow's milk and dissolving the salts that make up its composition will require less acid and time.
Acids affect not only inorganic, but also organic compounds, so I chose hydrochloric acid as a milder acid. So that its effect on the organic substances of bone tissue is minimal.
So, I remove the bone from a glass with a 10% hydrochloric acid solution, remove the remaining acid with filter paper, and check the properties of the bone. She is able to bend in all directions.
? Teacher.
BY. Organic substances give bones firmness and elasticity .
Teacher:Now let's solve the problem of how to remove organic matter from bone.
BY.They can be burned.
Teacher: That's right, organic matter burns well. When we studied the chemical composition of the plant organism, we said that plant remains (fallen leaves, dry branches, stems, etc.) burn well. Ash always remains at the site of the fire - these are mineral salts (i.e. inorganic substances), and all organic substances burn.
The bone was charred. Charring is a sure sign that organic matter has burned. The bone is hard but brittle. It crumbles in your hands.
? Teacher. What conclusion do the results of the experiment lead us to?
BY. Inorganic (insoluble calcium and magnesium salts) give bones hardness.
So, organic substances (proteins) give elasticity to bones, and inorganic substances (insoluble calcium and magnesium salts) give bones hardness. The combination of hardness and elasticity gives bone strength.
It is also necessary to know the proportions of organic and inorganic substances. Because if there are more inorganic substances in the bones, they will be hard but brittle. And if there is an excess of organic matter, then the guests will be too flexible.
Nature, creating the bone skeleton, found a golden mean (3:1). Therefore, human bones are strong enough to perform the functions assigned to them.
The composition of human bone tissue changes throughout a person's life.
?Teacher.How does bone chemistry change with age?
Reading a textbook. Page 47, article “Chemical composition of bones”, third paragraph
BY.With age, the content of inorganic substances in bone increases and the content of organic substances decreases.
? Teacher. Why do children often experience bone curvatures, and older people often experience fractures? Why do you need to constantly monitor your posture at your age?
BY.Children's bones contain more organic matter. Their bones are more resilient and elastic. With age, the salt content in the bones increases. In old age, bones become brittle due to the fact that their content of inorganic salts significantly exceeds the content of the elastic component.
Teacher. Children's bones are quite flexible, and incorrect posture can lead to curvature of the spine. Health is a person’s greatest wealth, and it must be protected from a young age. It has been established that moderate load on the bone increases its strength, so it is very important to exercise physical culture. Bone health depends on many factors, and a balanced diet is important.
- 3. BONE STRUCTURE
- 3.1. MACROSCOPIC BONE STRUCTURE
Teacher. Guys, here is a preparation of cutting natural bone. Look carefully at the preparation and then at Figure 18, A and B (page 46). Compare it with a preparation of cutting natural bone. On the specimen, find the periosteum, compact substance, spongy substance, and medullary cavity.
Bones are covered with dense connective tissue - periosteum.
Vessels and nerves pass through the periosteum. The periosteum takes part in the nutrition of bone and the formation of new bone tissue.
Bones can grow in length and thickness.
In length they are growing due to cartilage cell division located at its ends
Due to cell division of the inner layer of the periosteum, bones grow
in thickness and heal when fractures occur.
Each bone has a compact (dense) and spongy substance. Their quantitative ratio and distribution depends on the place of the bone in the skeleton and on its function.
Dense (compact) substance especially well developed in those bones and their parts that perform the functions of support and movement. For example, the body of long tubular bones is built from a compact substance. The bone plates are cylindrical in shape and seem to be inserted into one another. This tubular structure of the compact substance gives the bones greater strength and lightness.
Spongy substance formed by many bone plates, which are located in the directions of maximum load. It forms thickenings of the heads of long tubular bones, as well as short flat bones. Between the plates there is red bone marrow, which is a hematopoietic organ - blood cells are formed in it. The cavities of the long bones of adults are filled with yellow bone marrow, which contains fat cells.
Over the course of a person's life, the ratio of dense and spongy bone changes. These changes depend on the lifestyle a person leads, his diet, and health status. The amount of dense matter in athletes is significantly higher than in people leading sedentary image life.
- 3.2. MICROSCOPIC BONE STRUCTURE
? Teacher. Guys, what groups of tissues do you know?
BY.Epithelial, muscular, nervous, connective.
Teacher. Which group does bone tissue belong to?
BY.To connecting
Teacher. What are characteristics connective tissue
BY.The presence of a well-developed intercellular substance that determines the mechanical properties of the tissue.
The bones of the human skeleton are formed by bone tissue, a type of connective tissue. The compact substance of bone consists of microscopic cells and tubules through which numerous blood vessels and nerves pass from the periosteum into the bone.
The walls of the bone tubules are lined with rows of radially arranged bone plates. This is the intercellular substance of bone. The presence of intercellular substance is characteristic of any connective tissue. The bone cells that form these plates are located along the outer perimeter of these rings.
Guys, now we have to do laboratory work"Microscopic structure of bone"
- LABORATORY WORK
- "Microscopic structure of bone"
Equipment: microscope, permanent preparation “Bone tissue”.
Progress:
1. Examine bone tissue at low microscope magnification
2. Find the tubules through which the vessels and nerves passed. In cross section they look like a transparent circle or oval.
3. Find the bone cells that are located between the rings and look like black spiders. They secrete plates of bone substance, which are then saturated with mineral salts.
4.Fill out the observation results in technological map by signing parts of the drawing.
Answer the questions:
1. Bone cells secrete intercellular substance in the form of plates, which are located around the canals, forming concentric cylinders. How does this affect bone strength? 2. Why is the aircraft body made from duralumin tubes, and not from sheet metal?
So, we are convinced that bones are strong and light at the same time. This allows them to perform supporting, protective and motor functions as part of the skeleton. This is achieved:
1. Due to the chemical composition.
2. Due to macrostructure.
3. Due to microstructure.
Methodological development biology lesson in 10th grade
>> The importance of the musculoskeletal system, its composition. Bone structure
§ 10. The importance of the musculoskeletal system, its composition. Bone structure
What qualities of bone ensure its lightness and strength?
Why is bone tissue classified as connective tissue?
Microscopic structure of bone. The compact substance of bone consists of microscopic cells and tubules through which numerous blood vessels and nerves enter the bone from the periosteum. The walls of the bone tubules are lined with rows of radially located bone plates (Fig. 19). This is the noncellular substance of bone. The presence of noncellular substance is characteristic of any connective tissue. The bone cells that form these plates are located along the outer perimeter of these rings.
Types of bones.
Based on the type of structure, there are tubular, spongy, and flat bones.
Tubular bones have the appearance of cylinders with thickened marginal ends. They serve as long, strong levers, thanks to which a person can move in space or lift weights. The tubular bones include the bones of the shoulder, forearm, femur and tibia. Tubular bones are covered with periosteum, with the exception of the articular surfaces. Behind the periosteum is a layer of compact, dense substance. In the terminal areas of the bone, the compact substance becomes spongy, which fills the ends of the bones. In the middle part of the bone there is no spongy substance; there is a bone marrow cavity filled with yellow bone marrow. Red bone marrow is stored in the spongy substance at the end of the bone.
Tubular bones grow in thickness due to the periosteum. However, bone mass increases only slightly because the walls of the medullary cavity contain cells that dissolve bone. Thanks to the complex and coordinated work of both cells, optimal bone strength is achieved with minimal weight and material consumption.
Growth in length of tubular bones occurs due to growth zones and is completed by 20-25 years. The growth zones are located near the ends of the bones. They consist of cartilage tissue, which is replaced by bone tissue as the bone grows.
Spongy bones have a rather thin compact substance on the surface, under which there is spongy substance filled with red bone marrow. Spongy bones include the bones of the vertebral bodies, sternum, small bones of the hand and foot. Basically, spongy bones have a supporting function.
Flat bones perform a mainly protective function.
They consist of two parallel plates of a compact substance, between which a spongy substance is located crosswise, like beams. Flat bones include the bones that form the cranial vault.
Skeleton, muscles, periosteum, compact, spongy bone, medullary cavity, red bone marrow, yellow bone marrow; bone tissue, bone plates, cells that form bone and dissolve bone; types of bones: tubular, spongy, flat; growth zones of tubular bones.
Why are the skeleton and muscles classified as a single organ system?
What are the supporting, protective and motor functions of the skeleton and muscles?
What is the chemical composition of bones? How can you find out the properties of its components?
Explain why bone bends are more common in children, and fractures more common in older people.
Consider Figure 18, A, B and C. Compare it with a preparation of a cut of natural bone. Find the periosteum, compact substance, spongy substance, medullary cavity.
1. Consider Figure 18, B and C. Explain why the crossbars of the cancellous substance are oriented in the direction of the forces of compression and tension of the bone.
Laboratory work
Microscopic structure of bone
Equipment : microscope, permanent preparation “Bone tissue”.
Progress
1. Examine bone tissue at low magnification using a microscope. Using Figure 19, A and B, determine: are you considering a transverse or longitudinal section?
2. Find the tubules through which the vessels and nerves passed. In cross section they look like a transparent circle or oval.
3. Find the bone cells that are located between the rings and look like black spiders. They secrete plates of bone substance, which are then saturated with mineral salts.
4. Think about why a compact substance consists of numerous tubes with strong walls. How does this contribute to bone strength with the least amount of material and bone mass required? Why is an aircraft body made from durable duralumin tubular structures, and not from sheet metal?
Kolosov D.V. Mash R.D., Belyaev I.N. Biology 8th grade
Submitted by readers from the website
Current page: 4 (book has 24 pages total) [available reading passage: 16 pages]
§ 9. Reflex regulation
1. What is part of the central nervous system, and what is part of the peripheral nervous system?
2. What is a reflex?
3. What is a reflex arc?
Central and peripheral nervous system. The human nervous system is divided into central and peripheral based on its location in the body. TO central nervous system include the brain and spinal cord. Peripheral nervous system consist of nerves, nerve ganglia and nerve endings. The majority of all neurons are localized in the central nervous system. Their bodies, together with short processes - dendrites, form the gray matter of the brain. Depending on the manner and location of neurons, gray matter can be represented or bark on the surface of the brain (neurons are arranged in layers), or cores(accumulations within the white matter). Long processes of neurons, covered with protective membranes, form nerve fibers. In the central nervous system, collections of nerve fibers are called tracts or pathways. They form the white matter of the brain. At the periphery, bundles of nerve fibers form part of the nerves. There are sensory, executive and mixed nerves. Sensory nerves carry information from the senses to the central nervous system. Through the executive nerves, control commands from the brain go to the organs, causing a response from the body. Mixed nerves contain both executive and sensory fibers. Humans have 12 pairs of cranial (cranial) and 31 pairs of spinal nerves.
Nerve cells located on the periphery form special clusters - nerve nodes, or ganglia. Some nerve nodes, they are called sensitive, receive primary information, process it and then transmit it to the central nervous system. Other nerve nodes (vegetative) process signals coming from the central nervous system and transmit information to the internal organs.
Reflex and reflex arc. Reflex call the body's response to irritation, occurring with the participation of the central nervous system and under its control.
Humans, like animals, have many reflexes: food, defensive, orienting. Involuntarily we pull our hand away from the hot object and turn our heads in the direction of an unexpected sound. These are examples of congenital - unconditional– reflexes.
Unconditioned reflexes are the result of the evolution of the species and were preserved due to natural selection. They are the same in all people and in animals of the same sex and age belonging to the same species. Animal species differ not only in the structure and functions of their organs, but also in the set of innate reflexes, which is a species characteristic.
Reflexes acquired during life are called conditional. Depending on whether a result beneficial to the body is achieved or not, they remain, change or disappear.
The reflex begins with irritation of receptors. Receptors- these are the endings of sensory nerve fibers or special sensory cells that convert irritation into nerve impulses. Through the processes of sensory neurons, the impulses generated in the receptors reach the central nervous system. There this information is processed by interneurons. The latter are located within the central nervous system. After this, the signals are received by executive neurons, on which the response depends. They get excited and send signals, triggering the work of muscles, glands, and internal organs, thanks to which the desired effect is achieved. Clusters of neurons of the central nervous system that cause one or another reflex action, called reflex centers these reflexes. They are found in the spinal cord and in various parts of the brain.
As an example, consider the innate blink reflex. To do this, let's conduct a simple experiment. For those who wear glasses, we suggest taking them off during the experiment. The experiment can only be carried out with clean hands. The use of pencils and other objects to irritate the skin and eyelids is unacceptable.
Progress of the experiment. Gently touch the corner of the eye from the side of the nose, the side of the cheek, as well as the eyelashes and eyebrows with your hand. Mark those areas whose irritation causes involuntary blinking with a “+” sign.
The reflexogenic zone is the area where receptors are located that cause a given reflex when irritated, in our case blinking. Experience shows that there are many such receptors in the inner corner of the eye, in the skin of the eyelids and eyelashes, but almost none in the outer corner of the eye.
Irritation of the receptors causes excitation in sensory neurons. Their bodies are located in a sensitive nerve node, outside the central nervous system. The axons of these neurons go to the medulla oblongata, where the interneurons are located. Those, in turn, transmit information to the higher parts of the brain and to the areas of the medulla oblongata where the centers of the blink reflex are located. From the executive neurons, the signal goes to the orbicularis oculi muscles, and both eyes close (blink) for a short time.
Rice. 21. Scheme of the reflex arc of the blink reflex: 1 – receptor; 2 – sensitive neuron located in the nerve ganglion; 3 – interneuron; 4 – motor neuron; 5 – circular muscle of the eye, closing the eyelids
The path along which nerve impulses travel from the receptor to the working organ is called reflex arc(Fig. 21). The reflex arc is the simplest neural circuit. It includes a receptor, a sensory neuron, interneurons and executive neurons. Sensory neurons carry information to the brain. Interneurons process it within the brain, executive neurons activate working organs.
Feedback system. The presence of a reflex arc is a prerequisite for the implementation of any reflex. However, it would be wrong to assume that the reflex reaction ends with the response of the working organ. The body must evaluate how correctly and correctly this response was organized. During the response, the receptors of the working organ are excited, and from them information about the achieved result is received back to the central nervous system.
So, during the experiment, you feel a touch on the skin, blinking. Thus, the presence of feedback allows the reflex nerve center to control the accuracy of the execution of its commands and, if necessary, make urgent changes in the work of the executive organ.
CENTRAL AND PERIPHERAL NERVOUS SYSTEM, REFLEX, REFLECTOR ARC, RECEPTOR, WORKING ORGAN, REFLEXOGENIC ZONE, FEEDBACK.
Questions
1. What is a reflex and a reflex arc? Give an example of a reflex arc.
2. What is another name for congenital reflexes and reflexes acquired during life? Why do you think they got these names?
3. What properties do receptors have?
4. Where are the bodies of sensory neurons located?
5. What function do intercalary and executive neurons perform?
6. Explain the need for feedback in the nervous system.
Tasks
1. Using Figure 21, sketch the reflex arc of the blink reflex and indicate its parts.
2. Gently touch the inner corner of the eye several times. Determine how many touches the blink reflex will slow down. Analyze this phenomenon and indicate it possible reasons. Suggest what processes in the synapses of the reflex arc can cause inhibition of the reflex reaction.
3. Check whether it is possible to inhibit the blink reflex using volitional effort. If you succeeded, explain why it happened.
4. Remember how the blink reflex manifests itself when a speck gets into the eye. Analyze your behavior from the point of view of the doctrine of forward and backward connections.
5. Draw a conclusion about the meaning of the blink reflex.
The main provisions of Chapter 3
The human body consists of cells, cells form tissues, tissues form organs, organs form organ systems, and those form the body as a whole.
The environment in which the body is located is called the external environment, and the internal environment is called the environment in which the cells of the body function. Cells are diverse in shape and structure, but similar in structure. Each cell has cell membrane. The cell nucleus contains chromosomes, which contain all the hereditary information of the organism. Sections of DNA responsible for the synthesis of a specific protein and controlling certain hereditary traits are called genes. The cytoplasm of the cell contains organelles: ribosomes, mitochondria, Golgi apparatus, endoplasmic reticulum, centrioles. They ensure the vital activity of the cell. Thanks to metabolic and energy processes, a cell can perform its functions, grow, develop and divide. Significant role in metabolism enzymes play. Cells can be in a state of excitation or in a state of rest.
There are four types of tissues in the body: epithelial, connective, muscle and nervous. Epithelial tissues participate in the formation of integument and glands, connective tissues - in the formation of bones, cartilage, blood, fat and other formations. Muscle tissue is capable of contracting. They are smooth and striated. Nervous tissue specializes in receiving, processing and transmitting information. Its main elements are neurons. They consist of a body and processes: dendrites and axon. Dendrites receive information and transmit it to the neuron body. The axon carries information to other cells. Synapses are formed at the points of contact of the axon with these cells.
The functioning of the nervous system is based on the reflex principle. A reflex is the body’s response to irritation, carried out with the participation of the nervous system. The path along which a nerve impulse travels during a reflex response is called a reflex arc. From an anatomical point of view, a reflex arc is a chain nerve cells. The reflex arc begins with a sensitive structure - a receptor that perceives a certain irritation (mechanical or light, sound or temperature, etc.). The second part of the arc consists of structures that transmit signals to the central nervous system. And finally, the control signal from the central nervous system reaches the working organ (muscle or gland) through the processes of executive neurons. Reflexes are innate (unconditioned) and acquired during life (conditioned).
Reflex regulation involves the central nervous system - the spinal cord and brain and the peripheral nervous system - nerves, nerve endings and nerve ganglia.
Chapter 4. Musculoskeletal system
In this chapter you will learn
About the structure and functions of the skeleton and muscles;
On the adaptation of the body to work and upright walking;
About the nervous regulation of muscle function;
About the training effect and the dangers of physical inactivity.
You will learn
Identify significant signs of the musculoskeletal system;
Identify poor posture and the presence of flat feet;
Provide first aid for injuries to the musculoskeletal system.
§ 10. The importance of the musculoskeletal system, its composition. Bone structure
1. What qualities of bone ensure its lightness and strength?
2. Why is bone tissue classified as connective tissue?
Skeleton and muscles. Musculoskeletal system often called musculoskeletal because the skeleton and muscles function together. They determine the shape of the body, provide support, protective and motor functions.
Support the function is manifested in the fact that the bones of the skeleton and muscles form a strong frame that determines the position of the internal organs and does not allow them to move.
Skeleton bones protect organs from injuries. Thus, the spinal cord and brain are in a bone “case”: the brain is protected by the skull, the spinal cord by the spine. The rib cage covers the heart and lungs, airways, esophagus, and major blood vessels. The abdominal organs are protected from the back by the spine, from below by the pelvic bones, and in front by the abdominal muscles.
Motor the function is possible only if the muscles and bones of the skeleton interact, since the muscles set the bone levers in motion.
Most of the bones of the skeleton are movably connected through joints. The muscle is attached at one end to one bone that forms the joint, and at the other end to another bone. When a muscle contracts, it moves the bones. Thanks to the muscles of the opposite action, the bones can not only make certain movements, but also be fixed relative to each other.
Bones and muscles take part in metabolism, in particular in the metabolism of phosphorus and calcium.
Chemical composition of bones. If you burn a bone, it will turn black from the carbon left over from the combustion of organic matter. If the carbon also burns out, a white residue will be left, extremely hard but brittle. This is a bone mineral.
To determine the properties of organic bone matter, it is necessary to remove minerals using hydrochloric acid. The bone will retain its shape. But the properties of the bone will change dramatically. It will become so flexible that you can tie it in a knot. Bone flexibility depends on the presence of organic substances, hardness - on inorganic substances.
The combination of hard, although brittle, inorganic matter and elastic organic matter gives bones both strength and elasticity. Human bones are strongest in adulthood (from 20 to 40 years). In children, the proportion of organic substances in the bones is relatively large. Therefore, children's bones rarely break, but are easily deformed under the influence of incorrect posture or uneven load. In older people, the proportion of minerals in the bones increases. Therefore, their bones become more brittle.
Microscopic structure of bone. Under a microscope, it can be seen that the bone tissue is organized in the form of plates arranged in a certain way. They either intersect like metal beams of complex engineering structures, or form dense bone cylinders. This structure gives bones strength. Depending on the location of the bone plates, two types of bone substance are distinguished: compact and spongy (Fig. 22). Bone plates are the noncellular substance of bone.
Records compact substance form complex systems– osteons (Fig. 23). Osteons are several layers of thin bone plates arranged concentrically around a canal containing blood vessels and nerves. Between the bone plates are bone cells.
Rice. 22. Bone tissue: A – compact substance; B – spongy substance (micrographs)
IN spongy substance intersecting thin bone crossbars, consisting of bone plates, form many cells. The crossbars form vaulted structures oriented along compression and tension lines, which ensures uniform load distribution. The cells of the spongy substance contain red bone marrow.
Bone marrow is the tissue that fills the cavities of the bones in humans. There are two types of this fabric: red bone marrow(Fig. 24), the main function of which is the formation of blood cells, and yellow bone marrow rich in fat cells. There are no blood-forming elements in the yellow bone marrow. However, after large blood losses, hematopoietic tissue may form in place of the yellow bone marrow.
Rice. 23. Microscopic structure of compact bone substance: A – in a three-dimensional image: 1 – concentric cylinders formed by bone plates; 2 – bone cells; 3 – blood vessels passing in the bone cavities inside the cylinders; B – on a cross section
Rice. 24. Red bone marrow in the cells of the spongy substance (micrograph)
The ratio of compact and spongy substance in the bone depends on the place of the bone in the skeleton and its function.
Types of bones. Based on the type of structure, there are tubular, spongy, and flat bones.
Tubular bones They look like cylinders with thickened edge ends. The middle part of the tubular bone is called the body, the expanded ends are the heads (Fig. 25). On the outside, the body of the tubular bones is covered with a dense connective tissue plate - periosteum. It contains a large number of blood vessels and many nerve endings. The cells of the inner layer of the periosteum actively divide, ensuring the growth of the bone in thickness and its healing during a fracture. Under the periosteum there is a layer of compact substance. In the center of the bone there is a canal (medullary cavity) filled with yellow bone marrow. The walls of the medullary cavity contain cells that dissolve bone. Thanks to the complex and coordinated work of bone tissue cells, optimal bone strength is achieved with minimal weight and material consumption.
Rice. 25. Structure of the bones of the limb: A – tibia: 1 – periosteum (outer surface); 2 – compact bone substance; 3 – inner surface of the periosteum; 4 – articular cartilage; B – cut of the head of the femur: 1 – spongy substance; 2 – compact substance; 3 – bone marrow cavity; B – orientation of the spongy substance struts
The heads are formed by a spongy substance and covered with cartilage. The narrowed part between the body and the heads of the tubular bone is the neck. In childhood and adolescence, the neck consists of cartilaginous tissue. Cartilage cells actively divide, allowing bone to grow in length. With age, cartilage tissue is gradually replaced by bone. The final ossification of the necks of tubular bones ends in women by 16–18 years, and in men by 20–22 years. After this, the growth of bones in length stops.
In the human skeleton, there are two types of tubular bones: long (bones of the shoulder and forearm, thigh and lower leg) and short (bones of the metatarsus, metacarpus and phalanges of the fingers).
Spongy bones have a rather thin compact substance on the surface, under which there is a spongy substance. Spongy bones include the bones of the vertebral bodies, sternum, carpal and tarsal bones. Basically, cancellous bones are located where it is necessary to combine strength and mobility.
Flat Bones located where increased strength is needed. They consist of two parallel plates of a compact substance, between which a spongy substance is located. Flat bones include the bones that form the cranial vault, shoulder blades, and pelvic bones.
SKELETON, MUSCLES, PERIOSTE, COMPACT AND SPONGE BONES, RED BONE MARROW, YELLOW BONE MARROW; TYPES OF BONES: TUBULAR, SPONGEIOUS, FLAT.
Questions
1. Why are the skeleton and muscles classified as a single organ apparatus?
2. What are the supporting, protective and motor functions of the skeleton and muscles?
3. What is the chemical composition of bones? How can you find out the properties of its components?
4. Explain why bone curvatures occur more often in children, and fractures more often in older people.
Tasks
1. Look at Figure 25, A, B and C. Compare it with a preparation of a cut of natural bone. Find the periosteum, compact substance, spongy substance, medullary cavity.
2. Consider Figure 25, B and C. Explain why the crossbars of the cancellous substance are oriented in the direction of the forces of compression and tension of the bone.
Laboratory work
Microscopic structure of bone
Equipment: microscope, permanent preparation “Bone tissue”.
Progress
1. Examine bone tissue at low magnification using a microscope. Using Figure 23, A and B, determine whether you are considering a transverse or longitudinal section.
2. Find the tubules through which the vessels and nerves passed. In cross section they look like a transparent circle or oval.
3. Find the bone cells that are located between the rings and look like black spiders. They secrete intercellular substance, which is then impregnated with mineral salts.
4. Think about why a compact substance consists of numerous tubes with strong walls. How does this contribute to bone strength with the least amount of material and bone mass required? Why is the airframe made from durable duralumin tubular structures, and not from sheet metal?
§ 11. Human skeleton. Axial skeleton
1 . What is a skeleton?
2. What parts is it divided into?
3. Why are the skull and trunk skeleton classified as the axial skeleton?
4. How is the skeleton adapted to walking upright?
5. Why is it okay to nod and shake your head?
Skeleton called a collection of bones, cartilage and ligaments that strengthen them. They determine the shape of the body, serve as support for soft parts, and protect internal organs from mechanical damage.
Axial skeleton. In the human skeleton there are axial skeleton And accessory skeleton. The axial skeleton combines the skull and the trunk skeleton. The accessory skeleton consists of the bones of the limb girdles and the skeleton of the free limbs (Fig. 26).
Scull determines the shape of the head, protects the brain, organs of hearing, smell, taste, vision, and serves as an attachment point for muscles involved in facial expressions. In the skull there are cerebral And facial departments (Fig. 27). The upper part of the brain is formed by unpaired frontal and occipital bones and paired parietal and temporal bones. They form the cranial vault. At the base of the brain section of the skull are the sphenoid bone and the pyramidal processes of the temporal bones. In the cavities of the temporal bones there are receptors for hearing and the organ of balance. The brain is located in the cerebral part of the skull.
Rice. 26. Human skeleton: 1 – skull; 2 – shoulder girdle; 3 – ribs, together with the sternum and thoracic spine forming the chest; 4 – humerus; 5 – radius; 6 – ulna; 7 – spine (lumbar); 8 – pelvis; 9 – sacrum; 10 – femur; 11 – tibia; 12 – fibula; 13 – foot bones; 14 – hand bones
Rice. 27. Human skull: A – profile view: 1 – frontal bone; 2 – parietal bone; 3 – occipital bone; 4 – temporal bone; 5 – lower jaw; 6 – upper jaw; 7 – zygomatic bone; 8 – eye socket; B – bottom of the brain part of the skull: 1 – scales of the frontal bone; 2 – ethmoid bone; 3 – sphenoid bone; 4 – pyramidal process of the temporal bone; 5 – occipital bone; 6 – foramen magnum
Rice. 28. Spine: A – sections of the spine: 1 – cervical; 2 – chest; 3 – lumbar; 4 – sacral; 5 – coccygeal. Vertebrae: B – cervical; B – thoracic region; G – lumbar region; 1 – spinous process; 2 – vertebral body; 3 – arc; 4 – transverse processes; 5 – superior articular process
The facial part of the skull consists of 15 bones, the largest of which are the upper and lower jaws, cheekbones and nasal bones. The shape and size of the nose is determined by the nasal bones. The fibers of the olfactory nerve pass through the openings of the unpaired ethmoid bone.
The bones of the brain and facial skull are immovably connected to each other, with the exception of the lower jaw. It can move not only up and down, but also left and right, forward and backward. This allows you to chew food and speak clearly. The lower jaw is equipped with a mental protuberance, to which the muscles involved in speech are attached.
Skeleton of the body. The basis of the skeleton of the body is spine(Fig. 28, A). It is formed by separate vertebrae(Fig. 28, B, C, D). Each vertebra has body, arc And shoots. The vertebral body and arch form a ring. The vertebrae are located one below the other so that their rings form spinal canal. It contains the spinal cord (Fig. 29).
Between the vertebral bodies lie intervertebral cartilaginous discs. They give the spinal column mobility, elasticity and soften shocks when running, walking, jumping.
The human spine has four curves: cervical, thoracic, lumbar, sacral(in mammals - only cervical and sacral). Thanks to the S-shape, the spine is able to spring and act as a spring, reducing shocks when moving. This is an adaptation to walking upright.
In the spine there are departments: cervical, thoracic, lumbar, sacral, coccygeal(see Fig. 28).
Like all mammals, cervical spine The human spine has seven vertebrae. The skull articulates with the first cervical vertebra using two condyles. Thanks to this joint, you can raise and lower your head. It's interesting that the first cervical vertebra has no body: it has grown to the body of the second cervical vertebra and formed a tooth - an axis around which the first cervical vertebra together with the head rotates in the horizontal plane when we show a negative gesture (Fig. 30). A ligament of connective tissue separates the tooth from the spinal cord. It is especially fragile in infants, therefore, when holding them in an upright position, their head must be supported to avoid injury.
Rice. 29. Section of the spinal column (cartilaginous discs not shown): 1 – spinous process; 2 – vertebral body
Rice. 30. The first two cervical vertebrae: 1 – first cervical vertebra (without body); 2 – tooth of the second cervical vertebra, formed by fusion of the bodies of the first and second cervical vertebrae; 3 – ligament separating the bone tooth and the spinal cord; 4 – second cervical vertebra; 5 – articular fossa for articulation of the condyles of the skull with the first cervical vertebra
Rice. 31. Chest: 1 – thoracic spine; 2 – ribs; 3 – sternum
Rice. 32. Sacral and coccygeal sections of the spine: 1 – fifth lumbar vertebra; 2 – sacrum; 3 – coccyx
Thoracic region The spine consists of 12 vertebrae, to which are attached ribs Of these, 7 pairs of ribs are movably attached to the sternum, 3 pairs are connected through cartilage to the overlying ribs. The two lower pairs of ribs end freely. The thoracic spine, ribs and sternum form chest(Fig. 31).
Lumbar consists of 5 vertebrae, quite massive, since they have to withstand the main weight of the body.
The next section consists of 5 fused vertebrae that make up one bone - sacrum(Fig. 32). If the lumbar region has high mobility, then the sacral region is motionless and very strong. When the body is in a vertical position, a significant load falls on it.
Finally, the last section of the spine - coccyx. It consists of 4–5 fused small vertebrae.
AXIAL SKELETON, ACCESSORY SKELETON, BRAIN AND FACIAL DIVISIONS OF THE SKULL, VERTEBRATE, INTERVERTEBRAL DISC, DEPARTMENTS OF THE SPINE: CERVICAL, THORACIC, LUMBAR, SACRAL, COCCYCOUS; CHEST, RIBS, STERNUM.
Questions
1. Which parts of the skeleton are classified as the axial skeleton, and which are classified as the accessory skeleton?
2. What is the significance of intervertebral cartilaginous discs?
3. What is the significance of the fixed connection of the bones of the skull, with the exception of the lower jaw?
4. How is the skull attached to the spine? Why should a newborn's head be held?
Tasks
1. Explain the significance of the S-shaped curve of the human spine.
2. Explain the structure and functions chest.
3. Bend your head and feel at the border of the cervical and thoracic seventh cervical vertebra.
4. Using material from previous biology courses, compare the shape of the chest of a human and other mammals, such as a dog. What are their differences? What do you think is the reason for this?
5. Prince Andrei Bogolyubsky of Vladimir, who lived in the 12th century, according to contemporaries, was a proud man: he did not bow his head to anyone and did not show honor to anyone. And only 800 years later, scientists, restoring the appearance of the prince from his skeletal remains, established something that those close to the prince had no idea about. Using additional sources of information, find out why Andrei Bogolyubsky always walked with his head held high.
This is interesting. The Old Slavonic word koshch (kosht) means dry. From it comes the word bone and the name of the character in Russian fairy tales - Koschey the Immortal Material Compressive strength Tensile strength Steel 552 827 Porcelain 250 55 BONE 170 120 Granite 145 5 Oak 59 117 Concrete 21 2 Study the data and draw a conclusion about the strength of bone tissue “as a building material” material" of the human skeleton Conclusion: surprisingly, bone is second in strength only to hard grades of steel and turns out to be much stronger than granite and concrete, which have become examples of strength. Salts of calcium, phosphorus, magnesium Proteins Fats Carbohydrates Bone Presence of substances Properties of bone Inorganic Organic Calcined Decalcified ϭ. Fill out the table: Ϯ. Draw a conclusion about the role of inorganic and organic substances in bone: Inorganic substances give bones... Organic substances give bones... 1. Look at Figure ϭ8, A and B; p. 46 2. Compare it with a preparation of sawing natural bone. Find the periosteum, compact substance, spongy substance, medullary cavity. Parts of the bone Structure and location Functions Formed by connective tissue, penetrated by a large number of blood vessels and nerves. Fuses with bone. Protective function, cell nutrition, equipped with pain sensitivity receptors. Ensures bone growth in width and fusion after fractures. Located under the periosteum, it consists of plates that are located tightly adjacent to each other. They have a cylindrical shape and seem to be inserted into one another. Provides strength and lightness. The bone plates in it are located loosely in the direction of the greatest load. Provides lightness and strength Red bone marrow Yellow bone marrow Equipment: microscope, permanent preparation Bone tissue. Work progress 1. Examine bone tissue at low magnification using a microscope. 2. Find the tubules through which the vessels and nerves passed. In cross section they look like a transparent circle or oval. 3. Find the bone cells that are located between the rings and look like black spiders. They secrete plates of bone substance, which are then saturated with mineral salts. Answer the questions: 1. Bone cells secrete intercellular substance in the form of plates, which are located around the channels, forming concentric cylinders. How does this affect bone strength? 2. Why is the aircraft body made from durable duralumin tubular structures, and not from sheet metal? Present the results of your observations in a technological map, signing parts of the drawing. So, we are convinced that bones are strong and light at the same time. This allows them to perform supporting protective motor functions as part of the skeleton. This is achieved: 1. Due to the chemical composition. 2. Due to macrostructure. 3. Due to microstructure.
