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Immagini e concetti della biologia Sylvia S. Mader Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

C4 - Skeletal and muscular system Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Skeletal system Functions: Movement and scaffolding Protects internal organs Assists breathing Stores and releases calcium Assists lymphatic and immune systems Helps digestion Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Types of skeletal system in animals Hydrostatic: fluid-filled body cavity surrounded by muscles (i.e. annelids and nematodes). Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Types of skeletal system in animals Exoskeletons: rigid external skeleton to which muscles attach (i.e. mollusks and arthropods). Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Types of skeletal system in animals Endoskeletons: rigid internal skeleton protected by soft tissue surrounding it (in vertebrates the endoskeleton is jointed). Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Axial skeleton The axial skeleton consists of the skull, vertebral column and rib cage. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Axial skeleton - the skull Cranium and facial bones of the skull protect the brain. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Axial skeleton - the vertebral column The vertebral column is composed of vertebrae separated by shock-absorbing discs. It protects spinal cord and nerves and anchors all other bones. Intervertebral discs allow movement of the vertebrae. 10 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Axial skeleton - the rib cage The rib cage is composed by 24 ribs, costal cartilage and sternum and protects heart and lungs. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Appendicular skeleton The appendicular skeleton is composed by bones in the girdles and limbs. It is the part of the skeleton that is adapted to allow the body to move. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Appendicular skeleton The bones of the pectoral girdle (shoulder) and the upper limbs are connected by ligaments and flexible. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Appendicular skeleton The pelvic girdle (hipbones) and lower limbs are adapted for strength and support. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Osteoporosis Decreasing in bone mass weakens bone strength. Protection against osteoporosis includes assumption of adequate calcium quantities and exercise. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Bone tissue Bones have: a medullary cavity, containing yellow bone marrow articular cartilage covering the end of the bone a dense and hard compact bone containing osteons a spongy bone at the ends containing red bone marrow Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Joints Joints are where two bones meet. Different types of joints allow different movements. Fibrous joints are immovable Cartilaginous joints are slightly movable Synovial joints are freely movable Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Synovial joints Synovial joints are filled with synovial fluid, provide stability and absorb shock. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Synovial joints Ball-and-socket joints allow movements in all planes, including rotation. Hinge joints allow movements in one direction only. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Body movements depend on skeletal muscles Skeletal muscles have various structural and functional roles: Support the body Make bones move Help maintenance of body temperature Assist body movement in veins Protect internal organs Stabilize joints Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Skeletal muscles Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Skeletal muscles contract in units Muscles are attached to bones by tendons and work in antagonistic pairs. Extension Flexion Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Skeletal muscles contract in units A motor unit is composed of muscle fibers controlled by the same motor neuron. Motor units can be stimulated by one nerve impulse (twitch contraction) or diverse nerve impulses (tetanus contraction). Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Muscles cell A single skeletal muscle cell (or muscle fiber) contains many myofibrils, rod-like unit composed of long proteins. Myofibrils contain repeating sections of sarcomeres. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Muscles cell Sarcomeres contain actin and myosin filaments. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Muscles contraction “SLIDING FILAMENT MODEL” Muscle contraction occurs when sarcomeres shorten and actin filaments slide past myosin filaments. The process is supported by ATP. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Muscles contraction Muscle contraction is activated by axon terminals at the neuromuscular junction. Neuromuscular junction Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Muscles contraction Muscles have three sources of ATP for contraction: The creatine-phosphate (CP) pathway is simple and rapid The anaerobic fermentation produces two ATP per glucose molecule The cell respiration produces diverse ATP molecules in aerobic conditions Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Muscles fibers There are two types of muscle fibers: Fast-twitch fibers Slow-twitch fibers Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Exercise has many benefits Improves muscular strength, endurance and flexibility Improves cardiorespiratory endurance Helps prevent cancer Improves strength and density of bones Relieves depression Enhance mood Help fight diseases Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012