Musculoskeletal System

• Locomotion


  Capacity to move on your own from one place to another
• Types of organisms based on locomotion

  • Motile (most animals and many protists)
  • Stationary (sessile) (plants, some aquatic animals like corals, sponges, barnacles)
• Stationary (sessile) organisms


  • Protists
  • Corals
  • Sponges
  • Barnacles
• Advantages of locomotion


  • Opportunity to obtain food
  • To find suitable places to live
  • To move from harmful conditions
  • To escape from enemies / to seek shelter
  • To find mate and reproduce
• Locomotion involves muscles and skeleton
• Exoskeleton


  Found in some protozoans and many invertebrates
• Endoskeleton


  Found in vertebrates (fish, amphibians, reptiles, birds and mammals)
• Adaptations for locomotion


  • In single-celled organisms (like protozoa), locomotion may involve pseudopods or various cell structures
  • In multicellular animals, locomotion always involves specialized muscle tissue
  • Whatever the method of locomotion, the basis is contractile proteins; proteins that have the capacity to change in length
• Some protists lack any means of locomotion, while others are highly motile (pseudopods, cilia or flagella)
• Locomotion in Hydra


  1. Looping: Bends over and attaches its tentacles, then pulls its base closer

  2. Somersaulting: It can move rapidly by somersaulting its base completely over its tentacles
• Although Hydra tends to be sessile, primitive muscle cells contract, mucus-secreting and ameboid cells enable it to glide
• Locomotion in Earthworm


  When circular muscles contract, the worm lengthens and becomes thinner, when longitudinal muscles contract, it becomes shorter and thicker. The fluid inside acts as a skeleton
• Locomotion in Grasshopper


  It's covered with exoskeleton of chitin, divided into plates separated by flexible joints. This arrangement allows it to walk, jump and fly
• Bones and Cartilage


  • Bones serve as sites of attachment for skeletal muscles, and they serve as levers that produce movement when these muscles contract
  • Bones give the body its shape and they support body structures
  • Bones protect delicate structures (brain, spinal cord, heart, lungs)
  • Bones serve as a storage site for minerals (calcium and phosphorus)
• Bone formation


  Osteoblasts (bone cells) secrete collagen molecules and polysaccharites. Collagen molecules form fibers, then bound with polysaccharides (cement). Calcium and phosphate ions from the body fluids combine (calcium phosphate) and precipitate within fibers and cement
• Haversian canal


  Cavity in the center of the bone that contains blood vessels and nerves
• Periosteum


  Tough membrane covering the outside of the bone (except at its ends). Its main function is the production of new bone for growth and repair. It also serves as a point of attachment for muscles to bones
• Types of boney tissue

  • Compact (more dense and strong)
  • Spongy (more porous)
• Red marrow


  Found in vertebrae, ribs, breastbone, cranium, long bones. Produces red blood cells, platelets and some types of white blood cells
• Yellow marrow


  Consists of fat cells, found in long bones
• Cartilage


  Type of connective tissue that is more flexible than bone. Found at the end of ribs, at joints, in the nose and outer ear. Provides support, flexibility and cushions against impacts
• Ossification


  As embryo develops, minerals are deposited and thus the cartilage gradually changes into bone
• Divisions of the human skeleton

  • Axial (skull, vertebrae, ribs, breastbone)
  • Appendicular (arms, legs, pectoral girdle, pelvic girdle)
• Types of joints


  • Immovable (bones tightly fitted together, like in the cranium)
  • Hinge (back and forth motion, like elbow and knee)
  • Ball-and-socket (widest range of movement, like shoulder and hip)
  • Pivot (rotation of the skull)
  • Gliding (limited flexibility, like vertebrae)
• Ligaments


  Tough, fibrous bands of connective tissue that hold bones together at movable joints
• Synovial fluid


  Fluid secreted into movable joints by the surrounding membranes, acts as a lubricant and reduces friction at the joint
• Tendons


  Strong fibers of connective tissue that attach skeletal muscles to bones
• Skeletal muscle


  • Attached to the bones of the skeleton and is involved in locomotion and all other voluntary movement
  • All voluntary movement is originated and coordinated by impulses from the brain and the spinal cord
  • Muscles can pull when they contract, but they can not push, thus they should work in antagonistic pairs
  • They are never completely relaxed (muscle tone)
• Smooth muscle


  Muscle that operates without conscious control, found in the walls of the digestive organs, arteries and veins, diaphragm and other internal organs
• Cardiac muscle


  Type of muscle found only in the heart