Skeletal and muscular systems 22018 The Skeletal System

Skeletal and muscular systems 2/20/18

The Skeletal System • Composes the basic framework of the body • Protects vital organs from injury • Allows movement (along with muscles) • Stores minerals and produces red blood cells

The Skeletal System • Consists of 206 bones • Also includes ligaments and cartilage • Bones can be classified into 2 groups: – Axial skeleton (80 bones) – Appendicular skeleton (126 bones)

Axial skeleton • • Skull (25 bones) Spine (28 bones) Ribs (12 pairs) Sternum (3 fused bones)

Appendicular skeleton • Upper extremity (64 bones) – Shoulder/scapula – Upper arm and forearm – Hand • Lower extremity (62 bones) – Pelvic girdle – Leg – Foot

Bone classification • Long bones – Named for shape, not size. Has a shaft (diaphysis) and 2 ends (epiphysis) ex. Tibia, femur, humerus, ulna • Flat bones – Broad surface for maximal protection of vital organs Ex. Sternum, ribs • Short bones – Cube-like ex. Carpal bones of wrist

Bones cont’d • Irregular bones – Provide anchor support and protection of muscular tissue Ex. Talus (ankle bone) • Sesamoid bone – Embedded in a tendon and acts as a lever Ex. Sesamoid bones in foot, patella

Purpose of the muscular system • • Produce movement Produce heat Form posture Provide joint stability

3 types of muscle • Skeletal – Produces movement • Cardiac – Heart muscle • Smooth – Blood vessels, stomach, etc.

Characteristics of muscle • Contractibility: the ability to shorten or reduce distance between two parts • Excitability: the ability to respond to stimuli • Extensibility: the ability to lengthen and increase the distance between two parts • Elasticity: the ability to return to original forms after being stretched or compressed

Muscle attachment • Every skeletal muscle has 3 features: – Origin: the part of the muscle that is attached to the bone that moves the least during movement – Insertion: the part of the muscle that is attached to the part that moves the most – Belly: the central part of the muscle • Muscle attaches to: – Cartilage – Ligaments – Skin – Other muscles – Bones- when the muscle contracts, the bone it’s attached to moves

Muscle functions • Muscles in the body are arranged in pairs. – Agonist (primary mover): muscle that provides movement in single directions – Antagonist: the muscle whose action opposes that of the primary mover – Synergistic: muscles that help steady a movement or stabilize a joint

Muscle contractions • Isometric: very little movement is produced – there are co-contractions – Example: performing “quad sets” • Isotonic: movement occurs – Eccentric- the muscle lengthens as it contracts – Concentric- the muscle shortens as it contracts ü Think about flexion and extension at the elbow joint. What are the roles of the biceps and triceps muscles during these movements?

Muscle tone • Can be achieved through proper nutrition and resistance exercise (i. e. weight lifting). • Muscular hypertrophy: when individual muscle cells increase in size due to excessive exercise (high volume, low intensity) • Muscular atrophy: when muscle cell shrinks from disease or lack of movement.