Skeleton. Structure, composition and connection of bones of the human skeleton

March 6, 2012

Joints perform several important functions at once. Find out what causes your joints to suffer and how to keep them healthy.

Joints are the junctions of two or more bones. There are an average of 206 bones in the human body. All of them, with the exception of the hyoid bone in the neck, are connected by different types of joints. Joints connect the human skeleton into a single system, allowing the body to move as a single unit. Thanks to them, a person can perform a wide variety of movements. They also protect the ends of bones from damage and act as shock absorbers for the body.

Types of joints

Flexibility test

Test how flexible your joints are with these nine flexibility tests. An expert comments.

Joints can be either
simple
- connecting just two bones (for example, the phalanx of a finger), or
complex
- combining several bones (for example, the elbow joint).
In addition, there are combinations of several joints, for example, the temporomandibular joint. All joints can be divided into three groups
: 1.
Movable joints
consist of bones, cartilage, ligaments and tendons and synovial fluid.
There are quite a lot of such joints in the human body. They provide: - rotation of the head, - rotation of the hip and shoulder, - bending of the knees and elbows, - squeezing and unclenching of the hands and grasping objects, - complex movements in the ankle and wrist. 2. Sedentary joints
.
An example is the cartilaginous joints of the bones of the vertebrae, ankle, and wrist. 3. Fixed joints
. These include places of fixed connection between bones using cartilage tissue. This is how, for example, the bones of the skull are connected.

Joints and excess weight

You can lose weight not only on the treadmill, but also on the pool track. Find out what else you can do to combat obesity without compromising your joint health.

Bones and their connections

Musculoskeletal system

We are opening a new chapter of anatomy dedicated to the musculoskeletal system. It is he who provides support for the body, maintains body parts in the required position, serves as protection for internal organs and provides locomotor function - movement.

Bones are the basis of the musculoskeletal system, which we are beginning to study. Osteology (from the Greek osteon - bone) is a branch of anatomy devoted to the study of bone tissue, individual bones and the skeleton as a whole.

In addition to what you learned about the structure of bones in the “connective tissues” section, there are a number of important points that I will draw attention to in this article.

The skeleton and joints are the passive part of the musculoskeletal system, the muscles are the active part. By contracting, the muscles change the positions of the bones - various movements occur.

Bone structure

Bone consists of organic and inorganic substances. Organic substances are represented by ossein (from the Latin os - bone), inorganic substances - calcium phosphate. The elasticity of bones is due to ossein, and the hardness is due to calcium salts. Normally, this ratio represents balance.

In children, bones are more elastic and resilient than in adults: organic substances predominate in them. In the bones of older people, the content of both the organic component and the inorganic component—calcium salts—is reduced, which is why the bones of the elderly are fragile and susceptible to fractures.

The compact substance of the bone is formed by bone plates that fit tightly to each other and form osteons (structural units of the compact substance of bone tissue). The compact substance gives bone strength.

The substantia spongiosum also contains bony plates, but they do not form osteons, making the substantia spongiosum less strong than the substantia compacta. In the spongy substance between the bone crossbars (bone beams) there is red bone marrow.

In the red bone marrow, the initial stages of development of the formed elements of blood take place: red blood cells, leukocytes, and platelets appear here.

Yellow bone marrow (adipose tissue) performs a nutritional function: nutrients - fats (lipids) - accumulate here. In case of large blood loss, yellow bone marrow can be replaced by red bone marrow cells.

Yellow bone marrow is localized in the bone marrow cavities (medullary canal) of tubular bones (in the diaphysis).

So, let's summarize. The spongy substance is the location of the red bone marrow, the central hematopoietic organ. The cavities of the tubular bones contain yellow bone marrow, which performs a nutritional function and can be replaced by red bone marrow cells in case of large blood losses.

The structural unit of the compact bone substance is the osteon, or Haversian system. The osteon canal (Haversian canal) contains blood vessels and nerves. Osteons are located in the direction of the force, which determines the mechanical strength of the bone.

The main cells of bone tissue that we studied in the section “connective tissues”: osteoblasts, osteocytes and osteoclasts. Osteocytes have a process form and are located around the Haversian canal.

Classification of bones

Bones are divided into:

Tubular

The bones are cylindrical in shape, most often their length is greater than their width. The cavity of the long bones contains yellow bone marrow.

The long tubular bones include the femur, fibula and tibia, humerus, radius and ulna. The short ones include the metatarsal and metacarpal bones, the phalanges of the fingers. When moving, the tubular bones perform functions like levers that move muscles.

Spongy

The width of the spongy bones is approximately equal to the length. Spongy bones are covered on the outside with a layer of compact substance and consist of spongy substance, which contains red bone marrow.

Spongy bones: sternum ( flat

spongy bone), ribs (
flat
spongy bones), carpal and tarsal bones. The clavicle is a spongy bone in structure, but in shape it is a tubular bone.

Mixed

These bones are characterized by a complex shape, and during development they are usually formed from several parts. These include the vertebrae (a vertebra is a mixed spongy bone), the sacrum, and the hyoid bone. By origin, the clavicle also belongs to mixed bones.

Flat (wide)

The area of flat bones significantly prevails over the width. Flat bones are similar in structure to spongy bones.

The flat bones are: parietal, frontal, temporal and occipital (bones of the cranial vault), scapula, sternum, ribs, pelvic bone.

The structure of the tubular bone

Using the example of a tubular bone, we will analyze the parts into which the bone is divided. The surface of the bone is covered with periosteum - tissue that surrounds the bone and firmly fuses with it. In the thickness of the periosteum lie blood vessels and nerves that give branches inward.

Remember that bone growth in thickness occurs precisely thanks to the periosteum: its inner layer of cells divides, and the thickness of the bone increases. Thus, the periosteum performs a number of important functions:

Protective - the outer layer is dense, protects the bone from damage
Nutritional (trophic; Greek trophe - food, nutrition) - vessels pass through the thickness of the periosteum to the bone
Nervoregulatory - nerves pass through the thickness of the periosteum
Bone formation - bone growth in thickness

Let's move directly to the structure of the bone. The diaphysis (Greek diaphýomai - to grow between) is the body of the bone, usually the diaphysis is cylindrical or triangular. The epiphysis (from the Greek epiphysis - growth, lump) is the thickened end of a long tubular bone. The area of bone between the epiphysis and diaphysis is the metaphysis (Greek meta - after, after, through).

In the diaphyses, compact bone substance predominates, in the epiphyses - spongy. These terms are easy to explain and remember with a picture, so make a diagram and you'll learn them quickly

Pay special attention to the fact that bone growth in length is due to the epiphyseal plate. It is due to this plate, located between the metaphysis and epiphysis, that the bone grows in length. The epiphyseal plate is well supplied with blood.

Bone connections

Bones can be fixedly connected to each other: pelvic bones (ilium, pubis, ischium), skull bones (except for the lower jaw), sacral vertebrae, coccyx.

Semi-movable ones include: connections of the cervical, thoracic and lumbar vertebrae, connections of the ribs with the sternum. Intervertebral discs perform a shock-absorbing function (French amortir - to weaken, soften) - they evenly distribute the load on the vertebrae, ensuring flexibility and mobility of the spine. Pay special attention to the fact that the pubic bones are semi-movably connected to each other: they form the pubic symphysis.

Joint (synovial joint - Greek sýn - together + Latin ovum - egg) is a movable connection of the bones of the skeleton. The science of joints is arthrology (Greek arthron - joint + logos - study). Ligaments - dense formations of connective tissue - strengthen the joint from the inside and outside (ligaments are intra-articular and extra-articular).

The surfaces of the bones in the joint (called articular surfaces) are covered with hyaline cartilage, which reduces friction between the bones and performs a shock-absorbing function - evenly distributing pressure.

The joint capsule (capsule) is attached to the articular surfaces or in their vicinity, surrounding the articular cavity (cleft-like space). The inside of the joint capsule is covered with a synovial membrane, which secretes synovial fluid. Synovial fluid fills the joint cavity, nourishes the joint, moisturizes it, and eliminates friction of the articular surfaces.

Movably connected in the human skeleton are: lower jaw + temporal bone, clavicle + scapula (the joint is inactive), femur + pelvic bone (hip joint), humerus + ulna + radius (elbow joint), femur + tibia + patella (knee joint) , lower leg and foot (ankle joint = tibia + fibula + talus), phalanges.

Normally, the bones can shift relative to each other in the joint, but with an injury or too sudden and strong movement, this displacement can be too strong: as a result, the contact of the articular surfaces is disrupted. In this case, they talk about the occurrence of a dislocation.

Dislocation is a displacement of the articular ends of bones, either with or without disruption of the integrity of the articular capsule.

Techniques for providing medical care for dislocations:

Immobilization (lat. immobilis - motionless) of the injured limb using scarves, splints (supporting fastenings), by bandaging the limb to a healthy part of the body
Apply cold to the affected area, give painkillers (after making sure there is no allergy)
Take the victim to a doctor or call an ambulance

Before reducing a dislocation, an x-ray should be taken to ensure there are no bone fractures, which sometimes accompany a dislocation.

Bone fractures

A bone fracture is a partial or complete disruption of the integrity of a bone resulting from a load that exceeds the strength of the injured area.

Fractures are divided into:

Open - a wound is localized above the fracture, penetrating or not penetrating to bone fragments
Closed - a fracture without damage to the skin above it

Techniques for providing medical care for fractures:

Call an ambulance
If there is bleeding, it must be stopped immediately by applying a tourniquet.
In case of damage to the skin, apply an aseptic bandage using a bandage or clean cloth.
Give the victim a painkiller, making sure he does not have allergies
Immobilize (immobilize) the injured limb with special splints, fix the joints above and below the fracture site. For immobilization, you can use available means (sticks, boards, rods, etc.)

This article was written by Yuri Sergeevich Bellevich and is his intellectual property. Copying, distribution (including by copying to other sites and resources on the Internet) or any other use of information and objects without the prior consent of the copyright holder is punishable by law. To obtain article materials and permission to use them, please contact Yuri Bellevich

How do joints absorb shock?

A healthy person can stomp his foot on the floor without pain. Most likely, it will not even occur to him that the force of the muscles can break the bones of the lower leg by hitting them against the bones of the thigh. This does not happen because the bones are protected from impact loads by joints
.
They work as shock absorbers, meaning they absorb energy transferred from one bone to another. The shock-absorbing properties of joints are due to the joint work of cartilage, which covers the heads of bones, and the fluid that fills the joint space. Intra-articular cartilage
is a tough and smooth tissue.
It consists of water, collagen and other substances. For better gliding, cartilage tissue is nourished and lubricated by synovial fluid, consisting of protein and sugars. It is produced by a layer of cells that line the inside of the joint. Synovial fluid
not only nourishes cartilage.
This molasses-thick liquid acts as a shock absorber, preventing the bone heads from colliding with each other. To keep the synovial fluid and bone heads in place, the joint is surrounded by a shell of tough connective tissue - the joint capsule
. It attaches to the bones in close proximity to the cartilage and forms the joint cavity.

Symphysis

Semi-movable bone joints are also called “symphysis”. The symphysis is a kind of transitional state between the bones of the human skeleton. And unlike other types of bone joints, it is either a cartilaginous or fibrous joint. Inside such a connection there is a fairly narrow slit-like cavity.

Unlike a joint, which has a capsule, with a semi-mobile joint of bones it does not exist. Due to its fragility, since the symphysis literally consists of cartilage, the connection can be strengthened by interosseous ligaments.

With age, they do not become stronger and do not turn into ordinary bone tissue, retaining their appearance throughout a person’s life.

How do joints help movement?

In order for the skeleton to move at the joints, the bones must be connected to each other. This joint must be both flexible and rigid to allow the bones to move freely within a strictly limited range. To meet these conditions, the bones in the joint area are connected by ligaments
.
In addition, in the area of the joint, muscles are also attached to the bone using tendons
. Ligaments and tendons are strong enough to hold the joint in place, but also flexible enough to not tear during normal movement. The placement of ligaments and tendons determines how the various joints will move. For example, the knee can only bend forward and not backward.

Head skeleton

The skeleton of the head is called the skull (Fig. 18). The skull determines the shape of the head and protects the brain, organs of vision, hearing and smell from damage. In total, the skull includes 23-25 bones. The skull is divided into the brain and facial sections. The brain section of the skull is formed by fixedly connected bones: the frontal , two parietals , two temporal , occipital, sphenoid and ethmoid . These bones form the capacious cavity of the skull in which the brain is located. 61

The bones of the medulla are pierced by numerous openings through which blood vessels and nerves pass. The largest hole is located in the occipital bone. Through it the spinal cord communicates with the brain. Large cavities are found in the temporal bones, where the organs of hearing and balance are located.

The facial section of the skull is formed by numerous paired and unpaired bones. All of them are connected to each other motionlessly, with the exception of the lower jaw

. It can move up and down and left and right.

What causes joint damage?

1. Excess weight. Excess weight puts excessive stress on joints and leads to their destruction. 2. Poor nutrition. A lack of minerals and protein in the diet prevents joint tissue from recovering. 3. Incorrect posture. A sedentary lifestyle and monotonous, monotonous movements lead to joint destruction. 4. Uncomfortable shoes. Incorrectly chosen shoes increase the load on the joints of the legs and cause their diseases. 5. Excessive physical activity. Impact loads, injuries and violations of safety regulations during sports lead to the destruction of joints. 6. In addition, joints are affected by arthritis - the consequences of inflammation or age-related destruction of joint tissue. Find out more about how to keep your joints healthy and what you can do about it right now.

Examples of symphyses

Due to their peculiarity, symphyses are not found everywhere in the human body; they have a specific location as fixed and movable bone joints.

The most famous examples of semi-movable bone joints are found in places such as:

between the bones of the skull;
pubic symphysis;
between the two halves of the lower jaw;
in the spine area, between the vertebrae, the so-called intervertebral discs;
sacrococcygeal joint;
between the manubrium and the body of the sternum.

Sacrococcygeal junction

In the human body, namely in its musculoskeletal system, the spine is very important. It is the spine that demonstrates a vivid example of what semi-movable bone joints are.

If we consider the area of the sacrum and its connection with the coccygeal vertebra, then, in addition to the symphysis in its pure form, it is also connected with the help of ligaments. Thus, there is a significant shift. In women, this occurs naturally during childbirth; the amplitude of such mobility can reach 2 cm.