Skeleton consist of Bones, Joints and Muscles – Musculoskeletal System

from the skeleton, which consists of bones and their joints, muscles, is a system of organs of support and movement. And if the muscles are its active part, then the bones are passive. Muscles are attached to the skeleton, and the skeleton itself is made up of bones and cartilage. The human skeleton is made up of over 200 bones. Bones are paired and unpaired.

The main functions of the skeleton are:

  1. Protective: protection of the organs of the central nervous system – the brain and spinal cord – from damage; protection of vital internal organs: heart, lungs, blood vessels, organs of the reproductive and genitourinary system, etc.;
  2. Support;
  3. Motor: participation in the movements of the body and its individual parts;
  4. Hematopoietic: red bone marrow is located in the spongy substance of bones and is involved in hematopoiesis;
  5. Exchangeable: the skeleton is a storage site for magnesium, calcium salts, phosphorus and other substances.

The weight of the skeleton of an adult (living) person is about 15–20% of the total body weight.

Skeleton structure

The human skeleton consists of the following sections:

Axial skeleton. In turn, it is subdivided into:

  1. Head skeleton. This includes the skull.
  2. Torso skeleton: sternum, ribs and spinal column.

II Additional skeleton. Subdivided into:

  1. The skeleton of the upper limbs: bones of the hand, radius and ulna, humerus, clavicle and scapula.
  2. The skeleton of the lower extremities: the bones of the foot, the patella, the tibia and tibia, the femur and the pelvic bones.

Bone structure

Bone composition: bone tissue covered from the outside by the periosteum. With the help of periosteal cells, the bone grows in width and recovers after fractures.

Human bones for development are subdivided into:

  • Primary (no cartilaginous stage): anterior end of the clavicle and skull bones
  • Secondary (going through all stages: connective tissue, cartilage and bone): all remaining bones of the skeleton

The following types of bones are distinguished by shape :

  • Tubular. They consist of a diaphysis – a body and epiphyses – two thickened ends with articular surfaces. The part of the bone between the diaphysis and the pineal gland is the metaphysis. In people under the age of 22–25, metaphyseal cartilage is located at the site of the metaphysis. Due to it, the bone grows in length. The skeleton of the limbs consists of tubular bones.The long bones are composed of: tibia and fibula, femur, ulna and radius, humerus.

    The short tubular bones consist of the phalanges of the fingers on the feet and hands, the metatarsal bones (on the feet) and the metacarpal bones (on the hands).

  • Spongy. Some of the strongest and most mobile bones in the skeleton: the bones of the tarsus (on the feet) and bones of the wrist (on the hands)
  • Flat. They form body cavities – ribs and sternum, shoulder blades, pelvic bones, bones in the cerebral section of the skull. Their main function is to protect
  • Mixed. The composition of such bones includes parts that are different in structure and shape. For example: the vertebral body consists of spongy bones, processes and an arch of flat
  • Airborne. The difference in the structure of such bones is a cavity filled with air. Also, this cavity is lined with a mucous membrane. These bones consist of: the upper jaw, ethmoid bone, sphenoid and frontal bones

The bone marrow contains: cells of the spongy substance of the spongy bones and the medullary cavity of the tubular bones.

The medullary cavity of the diaphysis of the tubular bone contains yellow bone marrow, which performs a trophic function and which includes fat cells.

Bone composition

Chemical composition:

  • inorganic substances – 28%: compounds of magnesium, phosphorus, calcium, etc. (responsible for the hardness and strength of bones)
  • organic matter – 22%: osseomucoid and ossein (responsible for the elasticity and firmness of bones)
  • water – 50%

The older a person becomes, the greater the shift occurs towards an increase in mineral salts, as a result of which the bones lose their elasticity and become more susceptible to fractures.

Bone joints

Bone joints fall into two large groups:

Continuous (synarthrosis). There are no crevices, cavities and breaks in the places of such connections. In this case, one continuous connecting tissue connects the bones. The mobility of such compounds is low or absent altogether.

II Discontinuous (diarthrosis) are subdivided into:

    1. Connective tissue (fibrous) – syndesmosis: joints of the bones of the skull (sutures), the connection of processes and arches of the spine;
    2. Cartilaginous – sychondrosis: the joints of the ribs and the sternum, the joints of the vertebral bodies with each other. Such compounds, in turn, are:

 

a) temporary (they disappear at a certain age): connections in children’s sacral vertebrae;

b) permanent (remain for life): the connection of the pyramid of the temporal bone and the sphenoid and occipital bones.

  1. Bone – synostoses: connections between the sacral vertebrae of an adult.

In addition to the two indicated groups, one can also distinguish hemiarthrosis – semi- joints, the main characteristic of which is a small gap or plane between the bones and the absence of an articular bag.

Discontinuous joints are commonly referred to as joints. Due to the presence of the synovium in them, they are also called “synovial connections”. The joints are characterized by the presence of:

  1. Articular cartilage (covering the articular surfaces), the thickness of which is about 0.2–0.5 mm. The surface of the cartilage is smooth, moistened with articular fluid – synovial.
  2. An articular capsule (surrounding the joint on all sides, covering the articular cavity, like a sealant), the composition of which is dense connective tissue. Outside the capsule is fibrous tissue. Inside – the synovial membrane, which secretes synovial fluid, which helps to reduce the friction of the articular surfaces against each other.
  3. The articular cavity is the space between the joint capsule and the articular surfaces.
  4. In addition to the above signs, the joints are characterized by the following additional formations:
  5. Extracapsular ligaments;
  6. Intracapsular ligaments;
  7. Articular menisci and discs;
  8. Synovial folds.

Joints are:

  • Simple: the composition includes the articular surfaces of two bones
  • Complex: consists of the articular surfaces of three or more bones
  • Combined: when several joints are enclosed in different articular bags, but perform movement at the same time (proximal and distal radioulnar joints, intervertebral joints, temporomandibular joint)
  • Complex. Such joints are characterized by the presence of intra-articular ligaments, cartilage, discs and menisci (sternoclavicular joint, knee joint, temporomandibular joint)

Joint movements are carried out along the following axes:

  • frontal (flexion – flexion and extension – extension)
  • sagittal (abduction – abduction and adduction – adduction)
  • vertical (rotation – rotation)

Additionally, it is possible to carry out circular movements (circumduction) due to the transition from one axis of rotation to another.

Joints also differ in the shape of the articular surfaces and are distinguished by:

  • Spherical (movements on all three axes are possible, therefore they are also called triaxial). For example, the shoulder joint
  • Elliptical (movement along two axes is possible – biaxial joints). For example, the wrist joint
  • Cylindrical (movements only along one axis are possible – uniaxial joints). For example, the atlanto-axial median joint

The following types of the above articular surfaces are also distinguished:

  • Flat – triaxial. For example, intervertebral joints
  • Cup – shaped – triaxial. For example, the hip joint
  • Condylar – biaxial. For example, the knee joint
  • Saddle – biaxial. For example, the carpometacarpal joint of the 1st toe
  • Blocky – uniaxial. For example, the interphalangeal joints of the fingers
  • Helical – uniaxial. For example, the shoulder joint

Torso skeleton

The skeleton of the trunk includes: the spinal column, the sternum and 12 pairs of ribs, the joints between which are joints, cartilage, ligaments and bone tissue.

The human vertebral column comprises 33–34 vertebrae. They, in turn, are divided into departments:

  1. Cervical (consists of 7 vertebrae);
  2. Thoracic (of 12 vertebrae);
  3. Lumbar (from 5 vertebrae);
  4. Sacral (of 5 vertebrae);
  5. Coccygeal (from 4-5 vertebrae).

In an adult, the sacral vertebrae grow together and form one whole sacral bone, also with the coccyx, which subsequently forms the coccygeal bone. The sternum, ribs, and thoracic vertebrae make up the rib cage.

Vertebra structure

The vertebra includes: body, arch, paired and unpaired processes. Paired processes include transverse, upper articular and lower articular processes. Unpaired – spinous process. The arch of the vertebra grows together with its body with the help of the legs, limiting the vertebral foramen. All such vertebral foramen make up the vertebral canal, where the spinal cord is located. The vertebral arch has superior and inferior vertebral notches.

Such notches of adjacent vertebrae make up the intervertebral foramen. Blood vessels and nerves pass through these holes from the spinal canal. The structure, shape and size of the vertebrae differ depending on the functions of the spine.

Sternum and ribs

The ribs (12 pairs) and the sternum make up the thoracic region of the trunk.

The ribs are joined to the spine by the posterior ends, the anterior ends serve as a transition to the costal cartilage. The uppermost ribs, namely 7 pairs, are called true ribs (for the direct connection with the sternum by the front ends). There are also false ribs: VIII, IX, X. Between themselves they grow together with cartilages and are attached to the cartilage of the VII rib. The next 2 pairs are oscillating ribs. They are so short that they end freely in the muscle tissue of the abdominal wall.

The rib consists of a body, anterior and posterior ends. The posterior end of the rib with a thickening is the head of the rib with an articular surface divided by a comb. In front of the head there is a narrowed place – the neck of the rib, next to it there is a tubercle of the rib with an articular surface, with the help of which the rib joins the transverse process of the vertebra.

The sternum is located in the very center of the chest. It consists of three parts: the handle, the body and the xiphoid process.

The upper edge of the handle includes a jagged notch, to the right and left of which are the clavicular notches, which are connected to the clavicles. On the sides, the handle and body have rib notches for joining the true ribs.

Vertebral column

Intervertebral discs are located between the bodies of all vertebrae. They are made up of cartilage tissue. Inside the intervertebral discs, there are concentric circles of connective fibers that form a fibrous ring, inside which is the nucleus pulposus (pulposus). The intervertebral discs function as a shock absorber during active human movements: walking, jumping, running. The thickest discs are located in the lumbar region.

The anterior longitudinal ligament runs along the spinal column, from the atlas to the sacrum, connecting the vertebral bodies (along the anterior surface) with the intervertebral discs. The posterior longitudinal ligament runs inside the spinal canal , connecting the vertebral bodies along the posterior surface. The arches of the vertebrae are connected by yellow ligaments.

The yellow color is given to them by the connective tissue, which is responsible for the elasticity and firmness of the spine. The transverse and spinous processes are connected by means of the transverse and spinous ligaments. The supraspinous ligament is stretched along the entire spine , connecting the upper edges of the spinous processes. The supraspinatus ligament expands in the cervical region, attaching to the occipital bone, and is called the nuchal.

Intervertebral joints are flat joints located between the articular processes: the upper underlying vertebra and the lower overlying vertebra.

The sacrum and tailbone are connected by means of a semi-joint – cartilage with a small cavity. This connection is strengthened by ligaments on both sides. The connected vertebrae are the spinal column. The average length of the spinal column is from 70 to 75 cm. Inside the spinal column there is a spinal canal, which is the seat of the spinal cord. The upper and lower incisions of the adjacent vertebrae form the intervertebral foramen for the exit of the spinal nerves from the spinal canal.

In the cervical and lumbar spine there are forward bulge bends – lordosis; in the thoracic and sacral regions – bends with a bulge back – kyphosis; between the sacrum and the V lumbar vertebra, a protrusion is formed – a cape. These curves perform a shock-absorbing function in the spine during movement.

Head skeleton

The skull contains the brain and sensory organs and is divided into 2 sections:

  1. The cerebral skull (consists of paired bones: temporal and parietal; unpaired: frontal, ethmoid, sphenoid and occipital bones); in the cerebral skull there are:
    • vault, or roof
    • base
  2. Intraosseous, or facial (consists of paired bones: upper jaws, zygomatic, nasal, lacrimal, palatine bones and lower nasal concha; unpaired: lower jaw, vomer and hyoid bone.

The bones of the cranial vault are three-layered:

  1. Outwardly compact layer – compact plate;
  2. Middle – spongy layer;
  3. The inner one is a compact plate, it is also vitreous (since it is fragile).

The composition of the frontal bone: scales, paired orbital parts, located horizontally, and the nasal part – between the orbital.

The ethmoid bone consists of a horizontally located ethmoid plate, a perpendicular plate and an ethmoid labyrinth, consisting of air cells, closed from the side of the orbit by the orbital plate.

The sphenoid bone is made up of large and small wings, pterygoid processes.

The composition of the occipital bone: scales, lateral parts and the main part, limiting the foramen magnum.

The parietal bone is convex outward and concave inward, paired, forming the upper-lateral part of the cranial vault.

The temporal bone is composed of: a stony part, or pyramid, scaly and tympanic parts. The bone is a steam room, located between the sphenoid, parietal and occipital bones, includes the organs of balance and hearing, important vessels and nerves pass through it .

Facial skull bones

The intraosseous skull consists of three large bones: paired upper jaws and unpaired lower jaw, as well as a number of small bones that are involved in the formation of the nasal cavity and mouth and the walls of the orbit.

Paired bones of the facial skull: inferior turbinates, palatine, lacrimal, nasal and zygomatic bones.

Unpaired: hyoid bone and vomer.

The upper jaw consists of: the body, the frontal process, the palatine process and the alveolar, or alveolar process.

The palatine bone includes horizontal and perpendicular plates.

The lacrimal bone and the frontal process of the upper jaw together form a fossa of the lacrimal sac, which passes into the nasolacrimal canal, which opens into the nasal cavity.

The zygomatic bone includes three surfaces (orbital, lateral and temporal, as well as three processes (maxillary, frontal and temporal).

The nasal bone is connected to the frontal at the top, from the side – to the frontal process of the upper jaw.

Inferior turbinate. Location: in the nasal cavity, restricts the nasal passages (lower and middle) and closes the opening in front of the maxillary sinus.

Vomer – This bone is vertical. The vomer and the perpendicular plate of the ethmoid bone form the bony septum of the nose.

The lower jaw has a movable articular connection with the temporal bone. Consists of a horizontal body and vertical branches.

Limb skeleton

The skeleton of the upper limbs consists of two sections:

  1. Shoulder girdle: scapula and collarbone;
  2. Free limb skeleton:

    a) shoulder;
    b) forearm;
    c) brush.

  1. * The scapula is represented by a paired triangular bone, its lateral angle is larger and represents the glenoid cavity for connection with the humerus.

    The clavicle is an S-shaped bone located between the humeral process of the scapula and the sternum. It has two ends: sternal and acromial. There is a large articular surface at the sternum end to connect to the sternum. At the acromial end there is a small articular surface for connection with the acromial process of the scapula.

  2. * The humerus is a long, tubular bone. It consists of a body, or diaphysis, upper (proximal) and lower (distal) epiphyses.

The proximal pineal gland articulates with the scapula. On the distal epiphysis, the head and the block of the condyle of the humerus are located, with the help of which the connection with the bones of the forearm occurs.

The skeleton of the forearm consists of two bones – the ulna and the radius, which are tubular bones with epiphyses and diaphysis. The radius runs towards the thumb and the ulna runs towards the little finger.

Lower limb skeleton

The skeleton of the lower extremities consists of two sections:

  1. Department of the pelvic girdle;
  2. Section of the free lower limb.

1) * The pelvic girdle is a flat bone that connects the trunk and lower limb. In an adult, the pelvic bone is a single whole, while in children under 16, it is three separate bones that are connected by cartilaginous tissue:

a) the ilium;
b) ischial bone;
c) the pubic bone.

The pelvic bones of an adult are spliced ​​in the region of the acetabulum.

The ilium includes the body and wing.

The ischium is a body and a branch connected at an angle and bounding the obturator opening together with the pubic bone.

The pubic bone includes the body and the upper, as well as the lower branches. The medial surface of the superior branch is connected to the same surface of the bone from the opposite side, forming a symphysis — the pubic articulation.

2) * The femur is the largest tubular bone, consisting of a body (diaphysis) and two epiphyses (distal and proximal). It connects with the acetabulum by the proximal spherical epiphysis. The distal pineal gland has medial and lateral condyles with articular surfaces.

Two bones of the lower leg: the fibula and the tibia — long tubular bones with bodies and two epiphyses (proximal and distal).

The tibia is closer to the front of the thigh, and the fibula is farther away. The proximal epiphysis has a medial and lateral condyles articulating with the femoral condyles. The lower surface of the distal pineal gland and the ankle are articulated with the talus of the foot.

The fibula is shaped like a three-sided prism. It is much thinner than the tibia. The proximal pineal gland articulates with the tibia. The distal pineal gland articulates with the talus of the foot.

The patella is a sesamoid bone in the shape of a rounded triangle with the base up.

The skeleton of the foot consists of three sections:

  1. The tarsus are seven separate bones that are arranged in two rows:a) proximal (posterior): calcaneus and talus. Each of these bones has articular surfaces to connect with adjacent bones.

    b) distal (anterior): scaphoid, cuboid and three wedge-shaped bones.

  2. Metatarsus – five short tubular bones, consisting of a base, body and head. The bases of these bones are connected to the bones of the tarsus, and the heads are articulated with the phalanges of the fingers.
  3. Fingers. In addition to the thumb, each toe has a distal, middle, and proximal phalanx. The thumb consists of two – distal and proximal.

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