Musculoskeletal System - Bones Joints and Muscles
The Skeletal System
The human skeleton is made up of 206 bones in adults. For AQA GCSE PE, you need to know the key bones, their locations, and how they work with muscles and joints to produce movement.
Functions of the Skeleton
The skeleton performs five key functions, often remembered using the mnemonic SPMMP:
- Support — provides a rigid framework that supports the body and holds organs in place
- Protection — surrounds and shields vital organs (e.g. the cranium protects the brain, the ribcage protects the heart and lungs)
- Movement — bones act as levers, pulled by muscles at joints to create movement
- Mineral storage — bones store calcium and phosphorus, releasing them into the blood when needed
- Blood cell production — red and white blood cells are produced in the bone marrow of long bones
Key Bones You Must Know
| Body Region | Bone | Location / Notes |
|---|---|---|
| Head | Cranium | Skull — protects the brain |
| Spine | Vertebrae | 33 bones forming the spinal column |
| Upper body | Clavicle | Collarbone |
| Upper body | Scapula | Shoulder blade |
| Upper body | Sternum | Breastbone — front of ribcage |
| Upper body | Ribs | 12 pairs protecting heart and lungs |
| Upper body | Humerus | Upper arm bone |
| Upper body | Radius | Forearm (thumb side) |
| Upper body | Ulna | Forearm (little finger side) |
| Lower body | Pelvis | Hip bone |
| Lower body | Femur | Thigh bone — longest bone in the body |
| Lower body | Patella | Kneecap |
| Lower body | Tibia | Shin bone (larger lower leg bone) |
| Lower body | Fibula | Smaller lower leg bone (outer side) |
| Hands/Feet | Carpals / Tarsals | Wrist bones / Ankle bones |
| Hands/Feet | Metacarpals / Metatarsals | Hand bones / Foot bones |
| Hands/Feet | Phalanges | Finger and toe bones |
Joints
A joint is where two or more bones meet. There are three types:
Types of Joint
| Joint Type | Movement | Example |
|---|---|---|
| Fixed (fibrous) | No movement | Cranium |
| Slightly moveable (cartilaginous) | Small amount of movement | Vertebrae in the spine |
| Freely moveable (synovial) | Wide range of movement | Knee, hip, shoulder, elbow |
Synovial Joint Structure
All synovial joints share common features:
- Synovial membrane — lines the joint capsule and secretes synovial fluid
- Synovial fluid — lubricates the joint, reducing friction
- Joint capsule — surrounds and encloses the joint
- Articular (hyaline) cartilage — smooth covering on bone ends that absorbs shock and reduces friction
- Ligaments — connect bone to bone and stabilise the joint
- Tendons — connect muscle to bone, transmitting the force of muscle contraction
Types of Synovial Joint
| Synovial Joint Type | Movement Allowed | Example |
|---|---|---|
| Hinge | Flexion and extension only | Knee, elbow, ankle |
| Ball and socket | Flexion, extension, abduction, adduction, rotation | Hip, shoulder |
| Pivot | Rotation only | Neck (atlas and axis vertebrae) |
| Condyloid | Flexion, extension, abduction, adduction | Wrist |
The Muscular System
Muscles create movement by contracting (shortening) and pulling on bones across joints. For GCSE PE you must know the voluntary (skeletal) muscles.
Key Muscles
| Muscle | Location | Main Action |
|---|---|---|
| Deltoid | Shoulder | Abduction of the arm |
| Biceps | Front of upper arm | Flexion at the elbow |
| Triceps | Back of upper arm | Extension at the elbow |
| Pectorals | Chest | Horizontal flexion of the arm |
| Trapezius | Upper back / neck | Extension and rotation of the head; shoulder elevation |
| Latissimus dorsi | Lower back | Adduction and extension of the arm |
| Abdominals | Stomach | Flexion of the trunk |
| Hip flexors | Front of hip | Flexion at the hip |
| Gluteals | Buttocks | Extension and abduction at the hip |
| Quadriceps | Front of thigh | Extension at the knee |
| Hamstrings | Back of thigh | Flexion at the knee |
| Gastrocnemius | Calf | Plantar flexion at the ankle |
| Tibialis anterior | Front of shin | Dorsiflexion at the ankle |
Antagonistic Pairs
Muscles work in antagonistic pairs: when one contracts (the agonist), the opposite muscle relaxes (the antagonist). For example:
- Bicep curl — biceps = agonist (contracts), triceps = antagonist (relaxes)
- Leg extension — quadriceps = agonist, hamstrings = antagonist
- Running (knee drive) — hip flexors = agonist, gluteals = antagonist
Types of Muscle Contraction
- Isotonic contraction — the muscle changes length while producing force. This can be concentric (muscle shortens) or eccentric (muscle lengthens under tension).
- Isometric contraction — the muscle produces force but does not change length (e.g. holding a plank, wall sit).
Exam Tips
- Be ready to label diagrams of the skeleton and muscles.
- Learn antagonistic pairs with sporting examples — the exam frequently asks you to identify the agonist and antagonist during a specific action (e.g. "Identify the agonist during the upward phase of a bicep curl").
- Remember that ligaments connect bone to bone and tendons connect muscle to bone — a common mix-up.
- Use the phrase "muscles can only PULL, never push" to explain why antagonistic pairs are necessary.