Human Anatomy & Physiology: Skeletal, Muscular, Cardiovascular Systems
Skeletal & Articular System
Anatomical Position
Standing upright, facing forward, feet flat, slightly apart, toes forward, arms at sides, palms facing forward, thumbs pointing away. This position is the reference point for describing movement.
Terms to Describe Movement
- Flexion: Decrease joint angle
- Extension: Increase joint angle
- Abduction: Movement away from midline
- Adduction: Movement toward midline
- Plantar flexion: Pointing toes downward
- Dorsiflexion: Bringing toes upward
- Supination: Palm up
- Pronation: Palm down
- Inversion: Sole of foot inward
- Eversion: Sole of foot outward
- Internal rotation: Toward midline
- External rotation: Away from midline
- Elevation: Upward movement
- Depression: Downward movement
- Circumduction: Combination of flexion, extension, abduction, adduction
Planes & Axes
Planes:
- Sagittal: Divides body left/right → flexion & extension
- Frontal (Coronal): Divides body front/back → abduction & adduction
- Transverse: Divides body top/bottom → rotation
Axes:
- Horizontal axis: Movement in the sagittal plane
- Anterior–posterior axis: Movement in the frontal plane
- Longitudinal axis: Movement in the transverse plane
Functions of the Skeleton
- Support: Framework for the body
- Movement: Levers for muscles
- Protection: Organs (e.g., skull, ribs)
- Mineral storage: Calcium & phosphorus
- Blood cell production: Red marrow produces RBCs & platelets
Axial vs Appendicular Skeleton
Axial: Skull, spine, ribs. Appendicular: Arms, legs, shoulder & pelvic girdles.
Types of Bones
- Long: Femur, humerus
- Short: Carpals, tarsals
- Flat: Sternum, ribs, scapula
- Irregular: Vertebrae, pelvis
- Sesamoid: Patella
Composition & Anatomy of a Long Bone
- Diaphysis: Shaft
- Epiphysis: Ends
- Articular cartilage: Smooth joint movement
- Periosteum: Outer protective layer
- Compact bone: Dense strength
- Cancellous (spongy) bone: Light, marrow-filled
- Medullary cavity: Contains marrow
Types of Bone Cells
- Osteoblasts: Build bone
- Osteoclasts: Break down bone
- Osteocytes: Maintain bone
Bone Injuries & Diseases
Fracture types: Simple fracture: bone cracked; compound fracture: bone breaks skin; comminuted: bone shattered; stress fracture: overuse.
Osteoporosis
Loss of bone density, higher fracture risk. Prevention: weight-bearing exercise, calcium, vitamin D.
Types of Synovial Joints
- Hinge: Knee, elbow
- Ball & socket: Shoulder, hip
- Pivot: Atlas–axis
- Saddle: Thumb
- Gliding: Wrist
- Ellipsoid: Wrist (flex/extend + abduct/adduct)
Shoulder (Detailed)
Ball & socket joint. Very mobile, less stable.
Common injuries: Dislocation, rotator cuff tear, biceps tendinitis, AC joint separation.
Knee (Detailed — Study This Too)
Hinge joint. Very stable, less mobile.
Structures & injuries:
- ACL: Prevents forward tibial movement; ACL tear
- PCL: Prevents backward tibial movement
- MCL / LCL: Side-to-side stability
- Meniscus: Shock absorption; meniscus tear
- Patellar tendinitis
Muscular & Nervous System
Types of Muscle
- Skeletal: Voluntary
- Smooth: Involuntary
- Cardiac: Heart only
Muscle Fibre Types
- Slow twitch (Type I): Endurance, aerobic
- Fast twitch (Type II): Power, anaerobic
Training Types
- Isotonic: Movement through ROM
- Isometric: No movement
- Isokinetic: Constant speed, machine-based
Somatotypes
- Ectomorph: Lean, endurance
- Mesomorph: Muscular, athletic
- Endomorph: Stocky, strength
Muscle Pairs
Agonist: Prime mover. Antagonist: Opposes movement.
Origin & Insertion
Origin: Fixed point. Insertion: Moving point.
Types of Muscle Contraction
- Concentric: Shortening
- Eccentric: Lengthening
- Isometric: No length change
Anatomy of Skeletal Muscle
Muscle → fascicle → fibre → myofibril → sarcomere. Actin (thin) & myosin (thick).
Sliding Filament Theory
Brain sends signal, calcium released, myosin binds actin, power stroke using ATP, filaments slide, muscle shortens.
Motor Unit
One motor neuron + muscle fibres. Smaller motor unit = more precision. All-or-none principle.
Reflex Arc (Exam Favorite)
Receptor, sensory neuron, interneuron, motor neuron, effector. Purpose: fast protection.
Deformation Curve
- Elastic region: Returns to normal
- Yield point: Transition
- Plastic region: Permanent damage
- Failure point: Rupture
Soft Tissue Injuries
Strain: Muscle/tendon. Sprain: Ligament.
Grades:
- Grade 1: Stretch
- Grade 2: Partial tear
- Grade 3: Complete tear
RICE vs METH
RICE (acute):
- Rest
- Ice
- Compression
- Elevation
METH (recovery):
- Movement
- Elevation
- Traction
- Heat
Cardiovascular & Respiratory System
Blood Pressure
Systolic: Heart contracts. Diastolic: Heart relaxes.
ECG & Electrical Pathway
SA node: Pacemaker; AV node, Bundle of His, Purkinje fibres.
ECG waves:
- P wave: Atrial contraction
- QRS: Ventricular contraction
- T wave: Ventricular relaxation
Cardiovascular Dynamics
- Stroke volume (SV): Blood per beat
- Heart rate (HR): Beats per minute
- Cardiac output (CO): CO = HR × SV
- Cardiovascular drift: HR increases to maintain CO
- EPOC: Excess post-exercise oxygen consumption
Effects of Exercise
- Lower resting HR
- Increased SV & CO
- Stronger heart
- Improved oxygen delivery
Respiratory System
Functions:
- Oxygen intake
- CO₂ removal
Zones:
- Conductive: Nose → bronchi
- Respiratory: Alveoli (gas exchange)
Altitude Training (Long Answer Ready)
Lower oxygen availability. Body adapts by increasing RBCs & hemoglobin. Improves oxygen transport. Enhances endurance at sea level.
Reflex Arc: Rapid Automatic Response
A reflex arc is a rapid, automatic, involuntary response to a stimulus that bypasses the brain to protect the body from injury.
Steps (in order):
- Receptor: Detects stimulus
- Sensory neuron: Carries signal to spinal cord
- Interneuron: Processes information
- Motor neuron: Sends signal to muscle
- Effector: (muscle or gland) responds
Why important:
- Provides fast protection and reduces injury risk