The Concept of the Systems, Tissues and Organs of the Human Body

To correctly make a preliminary diagnosis, one needs to know what systems the human body is made up of.

For a deep understanding of the pathological processes that may develop in the body as a result of various types of injury, a basic grounding in human anatomy and physiology is of exceptional importance. Human anatomy and physiology are fundamental disciplines in medicine.
Anatomy is the science that studies the form and structure of the organism, its organs and tissues, in the course of their evolution
Physiology is the science of vital processes, the activity of individual organs and their systems, and of the organism as a whole.
The organism is a formed system that unites all anatomical-physiological systems; it constantly interacts with the external environment and exists in a state of dynamic equilibrium.
An organ system is a set of organs of common origin that share common structural features, are connected anatomically and topographically, and perform the same function.
The following organ systems are distinguished:

• - the musculoskeletal system;
• - the digestive system;
• - the respiratory system;
• - the excretory system;
• - the genital system;
• - the circulatory (cardiovascular) system;
• - the lymphatic system;
• - the sensory organ system;
• -the nervous system.

To precisely describe the position of body parts, organs and other anatomical structures in space and relative to one another, human anatomy uses the following terms:

• Medial – structures lying closer to the median plane;
• Lateral – structures lying further from the median line (side structures);

For the limbs the following are used:

• - proximal - for the point closer to the trunk,
• - distal – for the more distant point. The same terms for internal organs

denote distance from the point of origin of the given organ (for example: «the distal segment of the jejunum»).

1. The nervous system

Functions: control of the body, perception and transmission of signals, thought, consciousness.
Organs: the brain, spinal cord, nerves, sensory organs.

The human nervous system directs all the processes of the body. The structural unit of the system is the neurocyte – a special cell that connects with other neurocytes by means of special processes. Nerve impulses constantly travel along them, carrying information about sensations of pain, temperature, touch and so on to the «centre» and the corresponding response reaction to the «periphery». The human nervous system consists of the central (brain and spinal cord) and peripheral (nerves) divisions. The nervous system perceives information (stimulation) from both external and internal stimuli. In response to stimulation it produces a nerve impulse – a response to the stimulus (dilation or constriction of blood vessels, bronchi, etc., contraction or relaxation of muscles, increase or decrease in the pH of internal fluids, production of enzymes and hormones, etc.). This is the essence of the main function of the human nervous system.

2. The cardiovascular (circulatory) system

Functions: transport of oxygen, nutrients, hormones, and removal of metabolic waste products.
Organs: heart, arteries, veins, capillaries, blood, bone marrow

3. The respiratory system

Functions: gas exchange — supplying the body with oxygen and removing carbon dioxide.
Organs: nose, larynx, trachea, bronchi, lungs.

The respiratory system includes the nose, nasal cavity, nasopharynx, larynx, trachea, bronchi and lungs. All the organs listed above are divided into the upper respiratory tract (from the nose to the larynx) and the lower respiratory tract (from the larynx to the bronchi).

4. The digestive system

Functions: digestion of food, absorption of nutrients, elimination of residues.
Organs: mouth, oesophagus, stomach, intestine (small and large), liver, pancreas, gallbladder.

Fig. the digestive system

5. The excretory system

Functions: removal of waste and excess substances.
Organs: kidneys, ureters, urinary bladder, urethra, skin, lungs (partially).

6. The musculoskeletal system

Functions: movement, maintaining body shape, protecting organs.
Organs: bones, joints, muscles, ligaments, tendons.

The human musculoskeletal system (fig. 4) consists of bones, muscles and the connecting apparatus (ligaments, cartilage, joints).
The skeleton is divided into:
- the skeleton of the head (skull);
- the skeleton of the trunk (vertebral column, ribs, sternum);
- the skeleton of the limbs (upper and lower): a) the limb girdle; b) the free part of the limb.

The bones of the human skeleton are joined to one another by:
a) ligaments – immovable joints;
b) symphyses – semi-movable joints;
c) joints – movable connections.

The human muscular system is made up of striated
muscles, whose main activity is the conscious movement of parts of our body, maintaining posture and the relative position of the parts of the human body to one another.
Skeletal muscles are built from striated fibres that form the muscle belly. At their ends these have strong tendons for attachment. to the bones, and on the outside are covered by special fasciae that separate groups
of muscles.

7. The immune system

Functions: protection against infections, recognition and destruction of foreign bodies.
Organs: lymph nodes, spleen, bone marrow, thymus, leukocytes.

8. The lymphatic system

Functions: transport of lymph, participation in immune defence.
Organs: lymphatic vessels, lymph nodes, spleen, thymus, tonsils.

9. The endocrine system

Functions: hormonal regulation of all processes in the body.
Organs: pituitary gland, thyroid and parathyroid glands, adrenal glands, pancreas (islets of Langerhans), ovaries, testes.

10. The reproductive system

Functions: reproduction, sexual development.
Male: testes, seminal vesicles, prostate, penis.
Female: ovaries, uterus, fallopian tubes, vagina.

11. The integumentary system

Functions: protecting the body, thermoregulation, sensory function.
Organs: skin, hair, nails, sebaceous and sweat glands.