skeletal system of Invertebrates and vertebrates
Hydrostatic
Skeleton of invertebrates:
Hydrostatic
(Hydro=water + statikos=to stand).
Skeleton of
invertebrates is a core of liquid (water or a body fluid such as blood)
surrounded by a tension resistant sheath of longitudinal or circular muscles.
It is similar to water filled balloon because the force exerted against
incompressible fluid in one region can be transmitted to their regions.
Contracting muscles push against hydrostatic skeleton and the transmitted force
generates body movements as the movement of sea anemone. Lumbricus (earth worm)
contracts its longitudinal and circular muscles alternately creating a rhythm
that moves the earthworm through the soil. In both of these examples
hydrostatic skeleton keeps the body from collapsing when its muscles contract.
Invertebrate hydrostatic skeleton can take many forms and shapes such as
gastrovascular cavity of acoelomates, a rhynchocoel in nemertines, a
pseudocoelom in aschelminthes, a coelom
in annelids or a hemocoel in molluscs.
Vertebrates:
Vertebrates have cartilage and bone.
Cartilage: It is
speciailized type of connective tissue that provides a site for muscle
attachment, aids in movement at joints and provides support. Like other
connective tissues, it consists of cells (chondrocytes), fibres and cellular
matrix.
Bone: Bone (osseous)
tissue is a specialized connective tissue that provides a point of attachment for
muscles and transmits the force of muscular contraction from one part of the
body to another during movement. In addition bones of the skeleton support the
internal organs of many annelids, store reserve calcium and phosphate and
manufacture red blood cells and some white blood cells.
Human endoskeleton
has two major parts, the axial skeleton and appendicular skeleton. The axial
skeleton is made up of skull, vertebral column, sternum and ribs. Appendicular
skeleton is composed of appendages (fore limbs and hind limbs), pectoral girdle
and Hind limbs. These girdles attach the upper and lower appendages to axial
skeleton.
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