Knowledge base

The musculoskeletal system of the human body consists of bones, joints, muscles and tendons that work together to make the movements of the human body possible.

The skeleton is made up of 206 bones but the exact number can vary from person to person.

The skeletal system consists of two parts: the axial skeleton and the
appendicular skeleton . The axial skeleton includes, among others, the
skull, vertebral column, ribs and sternum

The appendicular skeleton includes the shoulder and shoulder bones
pelvic girdle and the bones of the limbs.

There are only minor differences between the bone systems of men and women. The bones
of men are generally larger and heavier than the same bones in women. In addition, the pelvic cavity in women is larger to allow childbirth.

A joint is a connection between bones that allows movement.

There are connective tissue joints (almost no movement possible), cartilage joints (limited movement possible) and synovial joints (a lot of movement possible).

All joints use axles. They can be classified according to the number of axes over which movement is possible:

1. Uniaxial Joints : Movement is possible in one direction such as in the elbow.

2. Biaxial Joints : Movement is possible in two directions such as in the ankle and wrist.

3. Triaxial joints : Movement is possible in 3 axes, for example in the shoulder and hip.

The vertebral column is also called backbone . It consists of 33 or 34 vertebrae with an intervertebral disc in between.

The vertebral column is made up from top to bottom of:

- 7 Cervical vertebrae at the level of the neck.

- 12 Thoracic vertebrae at the height of the shoulders and the middle of the back.

- 5 Lumbar vertebrae at the level of the low back.

- 5 Sacral vertebrae also known as the sacrum .

- 3-5 Coccygeal vertebrae also known as the coccyx .

The muscles in our musculoskeletal system cannot directly exert force on the ground or an object. Instead, they pull on bones which then move around a joint to allow for movement.

Muscles can only pull (shorten) and never push (lengthen).

Muscles are ultimately connected to the skeleton at two or more points.

When talking about trunk muscles:

Superior = Closer to the head.

Inferior = Closer to the feet.

With the muscles in the limbs we talk about:

Proximal = Closer to the trunk

Distal = Farther from the trunk.

A skeletal muscle is made up of different bundles of muscle fibers that we call muscle fiber bundles . These bundles are in turn made up of individual muscle fibers .

The skeletal muscle is surrounded by the epimysium . The muscle fiber bundles are surrounded by the perimysium and the individual muscle fibers are surrounded by the endomysium .

All three of these connective tissues are connected to the tendons. When tension is created in the muscle, this is passed on to the tendon and bone at all layers.

Muscle fibers are innervated by an impulse from motor neurons that transmit electrochemical signals from the central nervous system.

A motor neuron and all the muscle fibers it innervates are called a motor unit .

All muscle fibers of the motor unit contract at the same time upon an impulse from the motor neuron. At the same time, the contraction of the muscle fibers is not stronger with a stronger impulse. We call this the all-or-nothing principle .

The final force generated by a muscle therefore depends on the frequency of the impulses and on the number of motor units that are activated.

Proprioception is an organism's ability to perceive the position of its own body and body parts.

This mainly happens in our subconscious so that we do not need any conscious activity to, for example, stay standing.

The signals for proprioception come from different types of sensors that are found throughout the musculoskeletal system. The best known are:

1. Muscle spindles that occur in the muscles themselves and

2. Golgi bodies (Golgi tendon organs) that occur in the tendons.

The cardiovascular system is also called the cardiovascular system or the circulatory system and is responsible for the supply and removal of nutrients, waste products, oxygen, carbon dioxide, hormones, antibodies, blood cells and body heat within the body.

The heart is the pump of the cardiovascular system. It pumps oxygenated blood to the body and deoxygenated blood to the lungs.

The respiratory system is the organ system that serves for gas exchange: exchanging oxygen and carbon dioxide .

Our lungs cannot expand and contract on their own. They do this by upward and downward movement of the diaphragm (diaphragm) to increase and decrease the length of the thoracic cavity and by upward and downward movement of the ribs to increase and decrease the width (distance from back to chest) of the thoracic cavity.