zool skele

• Skeleton


  Supportive system that provides protection, support, and a place for muscle attachment
• Hydrostatic skeleton


  • Muscles in the body wall develop force by contracting against incompressible coelomic fluids
  • Alternate contractions of circular and longitudinal muscles of the body wall enable a worm to move forward
• Muscular hydrostats


  • Composed of incompressible tissues
  • Complex movements are a result of complex arrangements of muscles
• Muscular hydrostats


  • Elephant's trunk
  • Mammal & reptile tongues
  • Cephalopod tentacles
• Rigid skeletons


  • Contain some kind of rigid elements
• Types of rigid skeletons

  • Exoskeleton
  • Endoskeleton
• Exoskeleton


  Mostly made of chitin, found in molluscs & arthropods and some other invertebrates
• Endoskeleton


  Found in echinoderms, chordates, and some cnidarians, composed of two types of tissues (bone and cartilage)
• Vertebrate endoskeleton


  • Composed of bone and cartilage (types of connective tissue)
  • Bone provides support, protection, and serves as a reservoir for calcium and phosphorous
• Notochord


  Supportive rod found in protochordates and developing vertebrates, derived from mesoderm, except in jawless vertebrates it is replaced by the backbone
• Jawless fishes and elasmobranchs have cartilaginous skeletons - a derived feature since their ancestors had bony skeletons
• Most vertebrates have bony skeletons, with some cartilaginous parts
• Cartilage


  • Soft, pliable tissue that resists compression and is variable in form
  • Hyaline cartilage has a clear, glassy appearance with chondrocytes surrounded by a matrix, no blood vessels
  • Cartilage is often found at articulating surfaces of many bone joints, and as supporting rings of the passageways in the respiratory system
• Cartilage similar to hyaline cartilage is found in many invertebrates, such as the radula of gastropods and the lophophore of brachiopods
• Bone


  Highly vascular living tissue that contains significant deposits of inorganic calcium salts
• Types of bone


  • Endochondral (replacement) bone
  • Intramembranous bone
• Endochondral (replacement) bone


  Develops from another form of connective tissue - usually cartilage
• Intramembranous bone


  Develops directly from sheets of embryonic cells, found in the face, cranium, clavicle, and dermal bone
• Types of bone density

  • Spongy bone
  • Compact bone
• Spongy bone


  Consists of open, interlacing framework of bony tissue, oriented to give strength
• Compact bone


  Dense, the open framework of spongy bone has been filled in by additional calcium salts, composed of a calcified bone matrix arranged in sets of concentric rings - osteons
• Bone


  • Bundles of osteons interconnected with blood vessels and nerves
  • Between the rings are lacunae (cavities) filled with osteocytes (bone cells) connected by tiny passageways that distribute nutrients
• Bone remodeling


  • Osteoclasts are bone resorbing cells, osteoblasts are bone building cells, both processes occur together so that new osteons are formed as old ones are resorbed
  • Hormones (parathyroid hormone for resorption and calcitonin for deposition) are responsible for maintaining a constant calcium level in the blood
• Vertebrate skeleton


  • Axial skeleton
  • Appendicular skeleton
• Axial skeleton


  Includes the skull, vertebral column, ribs, and sternum
• Appendicular skeleton


  Includes the limbs and pectoral and pelvic girdles
• Over time, the number of skull bones has been reduced from as many as 180 in some early fishes to 35 or fewer in mammals
• Vertebral column


  Serves as the main stiffening axis, provides points for muscle attachment, provides stiffness, and preserves body shape during muscle contraction much like the notochord from which it is derived
• Most vertebrates have paired appendages
• Pectoral and pelvic fins

  In fishes, supported by the pectoral and pelvic girdles
• Tetrapods


  Have two pairs of pentadactyl limbs (although they may be highly modified through bone loss or fusion)
• Pelvic girdle


  Generally firmly attached to the axial skeleton
• Pectoral girdle


  More loosely attached to the axial skeleton
• Animal movement


  Most depends on contractile proteins which can change their shape to relax or contract, powered by ATP
• Cilia


  • Found throughout the animal kingdom (except in nematodes, rare in arthropods), uniform in diameter (.2-.5 μm) and structure, basal body similar to a centriole - 9 triplets of microtubules composed of the protein tubulin, cilium has 9 pairs surrounding two individual microtubules
• Flagellum


  A whiplike structure longer than a cilium and usually present singly, structure is the same as cilia but with a different beating pattern
• Parts of the human skeletal system

  • Bones (skeleton)
  • Joints
  • Cartilages
  • Ligaments (bone to bone)
  • Tendon (bone to muscle)
• Divisions of the human skeletal system

  • Axial skeleton
  • Appendicular skeleton
• Functions of bones


  • Protection of soft organs
  • Support of the body
  • Movement due to attached skeletal muscles
  • Storage of minerals and fats
  • Blood cell formation
• The human skeleton has 206 bones