1 Sylvia S Mader Immagini e concetti della

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Sylvia S. Mader Immagini e concetti della biologia 2 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

C 4 - Skeletal and muscular system 3 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Skeletal system Functions: • Movement and scaffolding • Protects internal organs • Assists breathing • Stores and releases calcium • Assists lymphatic and immune systems • Helps digestion 4 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Types of skeletal system in animals • Hydrostatic: fluid-filled body cavity surrounded by muscles (i. e. annelids and nematodes). 5 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Types of skeletal system in animals • Exoskeletons: rigid external skeleton to which muscles attach (i. e. mollusks and arthropods). 6 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Types of skeletal system in animals • Endoskeletons: rigid internal skeleton protected by soft tissue surrounding it (in vertebrates the endoskeleton is jointed). 7 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Axial skeleton The axial skeleton consists of the skull, vertebral column and rib cage. 8 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Axial skeleton - the skull Cranium and facial bones of the skull protect the brain. 9 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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, 2018

Axial skeleton - the rib cage The rib cage is composed by 24 ribs, costal cartilage and sternum and protects heart and lungs. 11 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. 12 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Appendicular skeleton The bones of the pectoral girdle (shoulder) and the upper limbs are connected by ligaments and flexible. 13 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Appendicular skeleton The pelvic girdle (hipbones) and lower limbs are adapted for strength and support. 14 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Osteoporosis Decreasing in bone mass weakens bone strength. Protection against osteoporosis includes assumption of adequate calcium quantities and exercise. 15 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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 16 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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 17 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Synovial joints are filled with synovial fluid, provide stability and absorb shock. 18 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Synovial joints Ball-and-socket joints allow movements in all planes, including rotation. Hinge joints allow movements in one direction only. 19 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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 20 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Skeletal muscles 21 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Skeletal muscles contract in units Muscles are attached to bones by tendons and work in antagonistic pairs. Flexion Extension 22 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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). 23 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. 24 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Muscles cell Sarcomeres contain actin and myosin filaments. 25 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Muscles contraction Muscle contraction occurs when sarcomeres shorten and actin filaments slide past myosin filaments. The process is supported by ATP. 26 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Muscles contraction Muscle contraction is activated by axon terminals at the neuromuscular junction. Neuromuscular junction 27 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Muscles contraction Muscles have three sources of ATP for contraction: 1. The creatine-phosphate (CP) pathway is simple and rapid 2. The anaerobic fermentation produces two ATP per glucose molecule 3. The cell respiration produces diverse ATP molecules in aerobic conditions 28 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Muscles fibers There are two types of muscle fibers: Fast-twitch fibers Slow-twitch fibers 29 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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 30 Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018