The Human Body

The Human Skeleton












Blood Vessel


Nervous System

The Human Skeleton

The skeleton is an anatomical structure composed of bones connected by joints using ligaments, cartilage and connective tissue.

The skeleton's role is to shape the human body, protect it and create its motion. The adult skeleton is composed of 206 bones at the end of the "ossification" process. In this process, the cartilage cells composing the baby's bones harden and become bone cells. This process ends at the second decade of our lives.

The skeletal system is divided into two parts:

Axial skeleton - skull, spine and rib-cage.

Appendicular skeleton - the shoulder belt, waist, upper limbs and lower limbs.



Bone is composed if two types of connective tissue, compact (or cortical) bone forming a stabilizing shell around the bone structure and spongy (or trabecular) bone built like a sponge but because it is composed in the same way as the dense bone tissue, it is very strong. The bone tissue contains calcium and collagen providing its strength, as well as salts and minerals. The cavity created inside the spongy tissue in the long bones contains the bone marrow which produces the blood platelets as well as the red and white blood cells.

The skeletal bones are composed of two main groups:

Long bones - carry weight and create motion. For example - femur, Humerus.

Short Bones

Flat/membranous bones - serve to protect the internal organs of the human body. For example: shoulder belt, skull, pelvis.

Irregular bones - clavicle, foot bones.

Sesamoid bones - knee cap.


The connecting area between the skeleton's bones. There are three types of joints, differing from each other in their shape and the movement capacity they allow.

Fibrous joints - Junctura fibrosa - incapable of movement, because the connective tissue between the joint is made of collagen fibers, giving strength and resilience to the connection - skull bones.

Cartilaginous joints - Junctura cartilaginea - the mobility of this joint is limited because the connective tissue between the bones is cartilage, which does not allow for much movement and absorbs shock - spinal vertebrae.

Synovial joints - Junctura synovialis - with varied movement ranges, the articular capsule typifying the synovial joint contains synovial liquid which serves to reduce friction between the joint's bones which it protects at the interface with the cartilage tissue. The limit to the joint's movement is caused by the structure of its composing bones, as well as the ligaments and tendons - the elbow joint.


The tendon is a connective tissue connecting the bone to the muscle. The tissue is mostly composed of dense collagen fibers which give it its strength, but cause a situation in which blood supply to the tendon is low so the healing process of a torn tendon takes a long time.

The inflammatory process begins when the immune system identifies an injury in the tendon tissue, whether from stress or from direct injury and its process is repairing the tissue.

Sometimes the inflammation develops in the tissue enveloping the tendons due to friction, such as in the De Quervain Syndrome in the wrist joint.

The reasons for tendon inflammations are typically connected to the way the joint is used, when stressing the joint by repeated movement and straining the tendon such as in the Tennis Elbow or Trigger Finger injuries.

The Carpal Tunnel Syndrome - CTS is another example for a tendon injury due to an improper positioning of the joint while using it in a repeated movement or direct injury of the tendon.

An inflammation of the tendon is expressed by pain, sensitivity and difficulty to move the joint.


The muscle is a connective tissue composed of muscle fibers, whose activity causes shortening, stabilization and stretching of the body's parts and limbs.

The human body has three types of muscles, each with its specific role:

Skeletal muscles - enable movement and are operated by sensors of the motor system.

Smooth muscles - are mainly found on the walls of internal human organs such as gull bladder, blood vessels, stomach.

Cardiac muscles - cause the heartbeat and the blood supply to the heart and from it.


Connective tissue connecting the joint bones, it is similar in composition to the tendon's structure, rich in collagen fibers giving it its strength. Its role is to restrict and prevent joint movement.

Ligaments tend to get injured from falling impact with "a hand stretched ahead" to block the fall.


Blood Vessel

The blood circulation system in our body. This system is composed of three groups, each with its specific role:

Arteries - their role is transporting blood  from the heart to the different organs. Blood flowing in the arteries is rich in oxygen.

Veins - their role is transporting blood from the different organs to the heart. The blood in the veins was oxygenated in a process called cellular respiration.

Capillaries - their role is transporting the blood to the body organs' cells. Thanks to their thin envelope they can transfer the materials carried by them, such as carbon dioxide, oxygen, hormones, and water to the different cells and receive the products from the cells for the purpose of ejecting it from the body.

Nervous System

The communication system transferring information between the different body cells and its role is to supervise, coordinate, process information, and cause a response of the various body parts, limbs and organs inside are body and between the body parts and the outside environment.

The nervous system is composed of three groups, each with a specific role:

Central nervous system - composed of the brain, which is the organ responsible for processing the neural information passed to it as well as the spinal cord which forms continuity and connection bridging between the brain and the peripheral nervous system.

Peripheral nervous system - is composed of the system responsible for sensing and passes the information received from inside the body and from the outside to the central nervous system as well as the motor nerves responsible for the movement or organs and limbs in our body.

Autonomic nervous system - is composed of a system responsible for the unconscious activities of the various systems of our body, such as the heart, the digestive system and the blood vessels.