SKELETAL SYSTEM-BIOLOGY- TNPSC,TET,RRB,SSC SCIENCE (GK) STUDY MATERIAL

SKELETAL SYSTEM

  • Skeletal system constitutes hard internal or
    external living or non-living parts that form
    the supporting framework of body.
  • It is divided into 2 parts.
  • Exoskeleton: Which is produced by
    ectoderm. It is present on the outside of the
    body (made of either dead tissues or
    biochemical secretion). Found in both
    invertebrates and vertebrates
  • Endoskeleton: Which is produced by
    mesoderm. It occurs inside the body and is
    made of cartilages and bones.
    HUMAN ENDOSKELETON
  • Divided into two main parts: Axial Skeleton
    and Appendicular Skeleton.
    A. AXIAL SKELETON (Total 80 bones) SKULL
  • Skull consists of two main parts cranium and
    face.
  • Cranium (brain box) is formed by 8 bones
    and provides a bony protection for the brain.
  • Face: There are 14 bones which form the
    skeleton of face.
  • There are also present 6 ear ossicles in the
    skull.
  • Another bone is hyoid.
    VERTEBRAL COLUMN
  • It is made up of 33 vertebrae in which 26
    bones are visible because five sacral
    vertebrae are fused to form one sacrum and
    four coccygeal vertebrae are fused to form
    one coccyx
    RIBS
  • Ribs are 12 pairs (12 x 2) of bony bars which
    form the sides of chest cage. They protect the
    delicate organs (heart, lungs, etc)
    STERNUM or Breast Bone
  • It is a narrow, elongated and flattened
  • structure, present just under the skin in the
    middle front of the chest.
    B. Appendicular Skeleton (Total 126 bones)
  • This skeleton lies laterally and is attached to
    axial skeleton at an angle. It is made up of
    girdles (pectoral and pelvic) and limb bones
    (forelimb and hindlimb)
    PECTORAL GIRDLE
  • Shoulder girdle
  • Has 4 bones (two in each pectoral girdle)
    LIMB BONES:
  • Forelimbs – Consists of 60 bones.
  • Hindlimbs – Consists of 60 bones.
    Femur (2) – Thigh (longest bone in the
    body)
    Fibula (2) – Shank (thinnest bone)
    PELVIC GIRDLE – Has 2 hip bones
    DISEASES OF SKELETAL SYSTEM:
  • Gout:Accumulation of uric acid crystals in joints
    leading to painful movement.
  • Dislocation: In this case, the bones at the joints
    are dislodged from their positions e.g., the ball of
    one bone may slip out of the socket.
  • Hard tissue deposits over articular cartilage along
    with higher secretion of synovial fluid causing pain
    and stiffness lead to rheumatoid arthritis.
  • Tearing of articular cartilage nd development of
    bony lumps at places causing pain, stiffness and
    permanent bending lead to osteoarthritis.
  • Bursitis is inflammation of the bursae present
    within synovial joint as small membrane bound
    pockets which stores synovial fluid.
  • Osteitis is inflammation of bone.
  • Osteoporosis is loss of bone density due to
    excessive absorption of calcium and phosphorus
    from the bone.
  • Osteomyeliltis is infection of bone.
  • Osteopetrosisis a hereditary disease marked by
    abnormally dense bone, and by the common
    occurrence of fractures of affected bone.
    ARTICULATION OF BONES – THE JOINTS
  • A bone joint or articulation may be defined
    as the junction of two bones. The study of
    such joints is known as arthrology.
    Note:
  • Femur (in hind limbs) is the longest bone
    and stapes (in middle ear) is the smallest
    bone of the body.
  • Sternum is absent in fish.
  • Fibulla – thinnest bone
  • Osteology is study of skeleton.
  • Chondrology is study of cartilages.
  • Arthrology is study of joints.
  • Masseters of jaw is the strongest muscle.
  • Birds have spongy bones with air filled
    spaces, called pneumatic bones.
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