Chapter 14: Support and Movement in Humans and Animals

14.1 Types of Skeletons

• Three skeletons: exoskeleton (insects, crabs), endoskeleton (humans), hydrostatic skeleton (earthworms). (p.266)
• Skeletons maintain shape, support soft tissues, protect organs and enable movement. (p.266)

14.2 Musculoskeletal System of Humans

• Axial skeleton: skull, vertebral column, ribs, sternum. Appendicular skeleton: pectoral girdle, pelvic girdle, upper and lower limbs. (p.267)
• Thoracic vertebrae: long spinous process, facets for ribs. Lumbar: largest and strongest, short spinous process, large centrum. (p.268)
• Sacral: five fused vertebrae forming a triangle; caudal: four fused bones. (p.268)
• Cervical vertebrae: short spinous process, small centrum, wide short transverse process, pair of transverse foramina. (p.269)
• Atlas: first cervical, no centrum, articulates with skull. Axis: second cervical, odontoid process. (p.269)
• All vertebrae have spinous and transverse processes, neural canal and centrum (except atlas). (p.269)
• Joints: immovable (suture in skull), slightly moveable (cartilage discs between vertebrae), freely moveable (hinge, ball-and-socket). (p.270)
• Ball-and-socket: shoulder and hip, rotation in all directions. Hinge: knee, elbow, fingers, movement in one plane. (p.271)
• Freely moveable joint: capsule protects, cartilage cushions, synovial membrane secretes synovial fluid that lubricates. (p.271)

14.3 Movement and Locomotion

• Skeletal muscles work in antagonistic pairs; the flexor bends, the extensor straightens. (p.272)
• Tendons connect muscle to bone; ligaments connect bone to bone. (p.272)
• Arm bending: biceps contracts, triceps relaxes. Arm straightening: triceps contracts, biceps relaxes. (p.273)
• Leg: biceps femoris is the flexor; quadriceps femoris is the extensor. (p.273)
• Fish: myotome muscles contract alternately, whipping the tail and pushing water backwards. (p.274)
• Birds: pectoralis major pulls wings down, pectoralis minor pulls them up. (p.275)
• Earthworm: alternating contraction of circular and longitudinal muscles with chaetae anchoring. (p.275)
• Grasshopper: flexor folds the hind leg; extensor straightens it to leap. (p.276)

14.4 Health Issues Related to the Human Musculoskeletal System

• Osteoporosis: reduced bone density; common after menopause due to low oestrogen. (p.277)
• Osteomalacia: soft bones from lack of calcium, phosphorus or vitamin D; rickets in children. (p.278)
• Arthritis: reduced synovial fluid and worn cartilage. Scoliosis: sideways curved backbone. (p.278)
• Care: good posture, proper attire, exercise, balanced diet with calcium and vitamin D. (p.279)