Human Anatomy and Physiology

Key Takeaways – Skeleton, Joints, and Muscles

• The musculoskeletal system consists of bones, ligaments, tendons, and muscles, enabling movement, posture, and protection of vital organs.

• The human skeleton has 206 bones that provide shape, produce blood cells, and support muscle movement.

• Upper limb bones include the humerus (arm), radius and ulna (forearm), carpals (wrist), metacarpals (hand), and phalanges (fingers).

• Lower limb bones include the femur (thigh), tibia and fibula (leg), patella (kneecap), tarsals (ankle), metatarsals (foot), and phalanges (toes).

• Joints connect bones and allow movement, with main types being hinge (knees, elbows), pivot (neck, forearm), and ball-and-socket (hips, shoulders).

• Cartilage cushions joints, supports structures like the nose and ears, and aids smooth movement but heals slowly due to no blood supply.

• Ligaments connect bones to bones at joints, providing stability but are prone to injury from overuse or sudden movement.

• Muscular system includes skeletal (voluntary), smooth/visceral (involuntary), and cardiac muscles, each with specialised movement functions.

• Common injuries to bones, joints, and muscles include fractures, sprains, strains, and cartilage damage, each requiring specific first aid management.

• Understanding basic anatomy enhances first aid skills, improves communication with medical professionals, and supports effective emergency care.

Skeleton, Joints, and Muscles

The musculoskeletal system is a term used to describe the bones and 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.

In the following section, you should become familiar with parts of the human anatomy. This will assist you in understanding medical terminology and give you a more significant knowledge base as a first aider so that you can understand and communicate effectively.

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

The bones of the skeleton have four 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 between your shoulder and elbow. The bone in the arm is called the humerus. The length of your arm below your elbow is 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 between your wrist and fingers is called the metacarpals. The fingers are called digits, and the bones in the digits are called phalanges (singular = phalanx).

Lower Limb Bones – The part of the leg 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 inside your leg) and the fibula (the bone on the outside). The correct term for the kneecap is the patella. The prominent 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 that the foot terminology is very similar to the hand.)

The following is a brief list outlining some 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 fifth cervical vertebra, and L2 refers to the second lumbar vertebra.

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

Joints

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

Joints are classified based on their range of movement. Some joints are fixed and immovable, like those in the skull, while others allow some movement, like those between the spine’s vertebrae.

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

Types of Movable Joints

1. Hinge joints allow movement in one direction only, similar to the functionality of a door hinge. Located at the knees and elbows
2. Pivot joints: allow for spinning, rotating, or twisting motion, e.g. the head moving from side to side. Situated in the neck and the radius part of an elbow
3. Ball-and-socket joints allow for a wide range of rotation and 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 less rigid and complex than 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
• The trachea, parts of the larynx, and smaller respiratory tubes
• Ends of ribs

Cartilage does not contain blood vessels, so 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 susceptible to overuse or sudden movement injury.

Ligaments of the Right Knee: Image by Mysid

Muscular System

The muscular system’s primary role is to move 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 and can contract and, therefore, move the parts of the body. Muscle movement can be classified as either voluntary or involuntary.

The muscular system can be categorized into three 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 involuntary as it cannot be controlled consciously.
• Visceral muscle is found inside organs like the oesophagus, stomach, intestines, bladder, 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, it has a very smooth, uniform appearance

Cardiac Muscle

• The cardiac muscle is involuntary as it cannot be controlled consciously.
• It 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 four to eight weeks to heal, depending on the break type and the casualty’s health and age.

Muscles can become strained, torn, pulled, or weakened. Injury or disease can harm joints, tendons, ligaments, and cartilage.

Each situation requires its 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 determine their consciousness level.

Consciousness: The state in which a person is awake, aware, vigilant, 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 several levels of consciousness between the two primary states, ranging from alert to 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. Learning about basic anatomy and physiology can significantly help with the skills learned in first aid training.