THE MUSCULOSKELETAL SYSTEM
The musculoskeletal system generates movement, supports the body and protects the organs. It
consists of the skeletal system and the muscular system.
1. THE SKELETAL SYSTEM
The skeletal system is made up of bones, to which muscles are attached, as well as cartilage. This
system protects organs such as the spinal cord and the brain, as well as supporting the body and
generating movement.
1.1.
BONES
Bones are hard structures made up of a protein called collagen, as well
as phosphorus and calcium salts. They consist of two types of bone tissue: compact and
spongy.
Some bones have projections called apophyses which are connected to tendons and ligaments.
Types of bones:
1. Long bones: are elongated in shape. They are found in the limbs (f.ex. the femur).
2. Short bones: are small in size. The vertebrae and the wrist bones are examples of short
bones.
3. Flat bones: are plate-like. Examples of flat bones are the bones of the skull.
Long bones
Short bones
Flat bones
Structure of a long bone:
Red Bonne Marrow
Epiphysis (spongy bone
tissue). It contains the red
bone marrow.
Diaphysis (compact bone
tissue)
Endosteum: a
layer of connective
tissue that covers
the internal cavity
of the diaphysis.
Periosteum: a
layer of connective
tissue that
surrounds the
bone.
Bones have several functions:
To provide a framework that supports the body
to provide the structures to which muscles are attached
to protect organs, such as the brain and spinal cord
to contain the red bone marrow that forms blood cells
to store calcium, which is released into the blood if required.
1.2.
CARTILAGE
Cartilage is softer than bone. It is formed of cartilaginous tissue.
Cartilage is found in the front part of the nose, in the ears, between the vertebrae (intervertebral
discs) and in the joints. Cartilage also forms the embryonic skeleton.
JOINTS
Joints are structures that connect two bones. There are three types of
joint: immovable, slightly movable and movable. Classification depends on the movement the joint
allows.
(1) IMMOVABLE JOINTS
Immovable joints are also known as sutures. They do not allow movement between the bones they
connect. The bones of the skull are an example of bones that have immovable joints between them.
(2) SLIGHTLY MOVABLE JOINTS
They allow small movements between the bones they connect. This type of joint is found between
the vertebrae in the spinal column.
(3) MOVABLE JOINTS
Movable joints allow a large range of movement between the bones. Joints of this type include the
knee, shoulder and elbow.
Movable joints usually consist of the following parts:
Ligaments. These are groups of fibres that connect the bones in the joint.
Cartilage. This is tissue that covers the bone surface and prevents friction between the
bones.
Ligaments
Cartilage
2. THE MUSCULAR SYSTEM
The muscular system consists of the skeletal muscles, the cardiac muscles and smooth muscles.
The skeletal muscles are made up of striated muscle tissue which contains long cells with several
muscle fibres.
Skeletal muscles have the following structure:
Muscle
Muscle
fibres
Muscle
fascicle
s
Bone
Tendon
A tendon is a strong structure made up of fibrous connective tissue that connects the muscle to the
bone. They transmit the muscle contraction to the bone, generating movement.
TYPES OF MUSCLE
The human body has different types of skeletal muscle. These muscles allow movement and give
support to different parts of the organism.
1. FUSIFORM Fusiform muscles are long and spindle-shaped. They are related to movement.
Examples of fusiform muscles are the triceps and biceps in the arm.
2. FLAT: Flat muscles are square or fan-shaped. They cover organs. Examples include the
pectoralis major in the chest, and the rectus abdominis found in the trunk.
3. CIRCULAR: Circular muscles are ring-shaped. They open or close ducts or cavities.
Examples of circular muscles include the orbicularis oris (lips), and the orbicularis oculi
(eye).
MUSCLE CONTRACTION
The striated muscle tissue that forms muscles contracts quickly and voluntarily. To do this, it
requires calcium, energy and oxygen. Certain stimuli cause muscle fibres to shorten (contract).
The muscles lengthen (relax) when the stimuli stop. This generates movement.
To flex the forearm, the biceps contracts and the triceps relaxes.
To extend the forearm, the triceps contracts and the biceps relaxes.
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