Human Anatomy and Physiology

Skeleton, Joints, and Muscles

The musculoskeletal system is a term used to describe the bones, as well as the adjoining ligaments, tendons, and muscles. The following section will provide an overview of the names and locations of different bones; however, you are not expected to demonstrate a complete knowledge of all the bones listed.

It is recommended that you become familiar with the following section, as it will assist you in understanding medical terminology, and give you a greater knowledge base as a first aider in which to understand and communicate effectively.

The skeletal system is made up of 206 bones that provide structure to our bodies and protects our internal organs from damage. Muscles, ligaments, and tendons are closely linked with this system and all play vital roles in allowing movement and function of limbs and body parts.

The bones of the skeleton have 4 main functions:

1. To give shape to the body
2. To produce blood cells
3. Support muscles to allow movement
4. Protect vital organs

Upper Limb Bones – Medically, the term arm refers to the part of your arm that lies between your shoulder and elbow. The bone in the arm is called the humerus. The length of your arm below your elbow has actually termed the forearm, which includes the radius (the bone on the thumb side of the arm) and ulna (the bone on the side of your little finger).

The bones in the wrist are called carpal bones (there are 8). In the hand, the next group of bones which are between your wrist and fingers is called the metacarpals. The fingers are referred to as digits, and the bones in the digits are called phalanges (singular = phalanx).

Lower Limb Bones – The part of the leg that lies between your hip and knee is called the thigh, and the bone commonly known as the ‘thigh-bone’ is called the femur. It can be confusing to note that whilst the term arm refers to the ‘upper’ part of your arm, the term leg medically refers to the part of the leg between your knee and ankle. The leg contains the tibia (the bone on the inside of your leg) and the fibula (the bone on the outside). The correct term for the kneecap is the patella. The main bone in the ankle which connects to the leg is called the talus. Your heel bone is called the calcaneus.

The bones in the part of the foot closest to the ankle are called tarsals, the long bones of the forefoot are called metatarsals, and the toes are digits with the toe bones being called phalanges. (Note the foot terminology is very similar to the hand).

The following is a brief list outlining some of the specific medical terms relating to different commonly known names for bones. Again, you do not need to memorise this list, but it is recommended that you read through it so you recognise these terms.

The Spine

The levels of the spine are referred to by their area and level, such as C5, or L2. C5 refers to the 5th cervical vertebra. L2 refers to the 2nd lumbar vertebra.

The disc spaces are named according to the levels they lie between, for example, C7/T1 is the disc between the 7th cervical vertebra and the 1st thoracic vertebra.

Joints

Human joints occur where two bones come together. The joints hold the bones together, allowing the skeleton to be flexible so that movement of the skeleton can happen. Ligaments and muscles provide movement and stability.

Joints are classified into categories based on the range of movement. Some of the joints are fixed and immovable like those in the skull. Other joints allow for some movement such as those found between the vertebrae of the spine.

Most of our joints are free-moving synovial joints which contain synovial fluid as lubrication to help the joints move freely.

Types of Movable Joints

1. Hinge joints: allows movement in one direction only, similar to the functionality of a door hinge. Located at: knees and elbows
2. Pivot joints: allows for spinning, rotating, or twisting motion, e.g. the head moving from side to side. Located at: the neck and the radius part of an elbow
3. Ball-and-socket joints: allows for a wide range of rotation and freeness of movement. Located at: hips and shoulders

Hip Bones: Image by Stephen Woods (Own work) [CC BY-SA 3.0]

Cartilage

Cartilage is a tough, flexible, fibrous connective tissue that is less flexible and stiffer than muscle yet is less rigid and hard as a bone. It helps to provide cushioning for joints.

Cartilage is found in many parts of the body:

• Moving joints between bones: knees, ankles, elbows
• Nose and ears
• Between the vertebrae of the spine
• Trachea, parts of the larynx, and smaller respiratory tubes
• Ends of ribs

As cartilage does not contain blood vessels, it repairs and grows more slowly than other tissues.

Ligaments

Ligaments are tough fibrous stretchy bands of connective tissue that, in most cases, hold one bone to another at a joint. Ligaments should not be confused with tendons that connect bones to muscles.

As ligaments play a vital role in stabilising the joints, they are quite susceptible to injury due to overuse or sudden movement.

Ligaments of the Right Knee: Image by Mysid

Muscular System

The main role of the muscular system is the movement of the human body but it also aids in maintaining posture and circulating blood and other substances throughout the body. Over 650 muscles are attached to the bones of the skeletal system with the ability to contract and therefore move the parts of the body. Muscle movement can be classified as being either voluntary or involuntary.

The muscular system can be categorized into 3 sections:

1. Skeletal Muscle
2. Visceral or Smooth Muscle
3. Cardiac Muscle

Anterior View of Muscles: Image by OpenStax College

Skeletal Muscle

• Skeletal muscle is a voluntary muscle as it is controlled consciously
• Most skeletal muscles are attached to bones anchored by tendons
• They work in pairs. One muscle moves the bone in one direction and the other moves it back again
• Contractions can be long, short, or single

Skeletal Muscle Fiber: Image by Blausen.com staff. “Blausen gallery 2014”. Wikiversity Journal of Medicine (Own work) [CC BY 3.0]

Visceral or Smooth Muscle

• Visceral/smooth muscle is an involuntary muscle as it cannot be controlled consciously
• Visceral muscle is found inside organs like the oesophagus, stomach, intestines, bladder, the uterus (females), respiratory system, and blood vessels
• The weakest of all muscle tissues
• Visceral muscle moves substances through an organ by making the organ contract, e.g. digesting food
• When viewed under a microscope, has a very smooth, uniform appearance

Cardiac Muscle

• Cardiac muscle is an involuntary muscle as it cannot be controlled consciously
• Is only found in the walls of the heart
• Responsible for pumping blood
• Cardiac muscle stimulates itself to contract, while hormones and signals from the brain adjust the rate of contraction

Issues with Bones, Joints, and Muscles

Though bones are strong, they can break or fracture.

• Closed fracture
• Open Fracture
• Complicated fracture

Fractures take around four to eight weeks to heal. This depends on the type of break and the health and age of the casualty.

Muscles can become strained, torn, pulled, or weakened. Joints, tendons, ligaments, and cartilage can be harmed by injury or disease.

Each situation requires its own first aid process and treatment

Levels of Consciousness

As per ANZCOR Guideline 3 – Recognition and First Aid Management of the Unconscious Person

Causes of Unconsciousness

The causes of unconsciousness can be classified into four broad groups:

• Low brain oxygen levels
• Heart and circulation problems (e.g., Fainting, abnormal heart rhythms)
• Metabolic problems (e.g., Overdose, intoxication, low blood sugar)
• Brain problems (e.g., Head injury, stroke, tumour, epilepsy).

Combinations of different causes may be present in an unconscious person e.g., a head injury due to the influence of alcohol.

The medical term “Level of Consciousness” (LOC) identifies the level of a person’s cognitive function (mental processes involved in gaining knowledge and comprehension). It involves their awareness of their surroundings and the potential to be aroused. A person’s responsiveness to stimulation will help to determine their level of consciousness.

Consciousness: The state in which a person is awake, aware, fully alert, and responsive to stimuli and to the environment.

Unconsciousness: The state in which a person is unaware of self and environment, unrousable and unresponsive to stimuli, e.g. C.O.W.S.

There are a number of levels of consciousness between the two main states. These range from being alert to being in a coma.

A person who fails to respond or shows only a minor response, such as groaning without eye-opening, should be managed as if unconscious.