Life Sciences Glossary: Functions of Skeleton, Type of Bone and Joints

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Functions of Skeleton

  • Support: The skeleton provides definite shape to the body and gives support to various body organs.
  • Facilitation of movement: The skeleton provides site for attachment of muscular tendons and it aids in locomotion.
  • Hemopoiesis: Formation of blood cells in the bone marrow by a process called hemopoiesis.
  • Protection: As examples, protection of the brain by skull, and heat and lungs by the bones of thorax.
  • Storage: Storage of minerals such as calcium and phosphorus.
  • Weight Bearing: Transfer of body weight.
  • Detoxification: Detoxification or removal of certain poisonous substances.
  • Other Functions: Helps in hearing, e. g. , car icicles. Bones are classified according to their shape, size and tissue of origin.

On the basis of tissue of origin, the types of bones in vertebrates are:

  • Cartilaginous bones or replacing bones
  • Membrane bones (investing bones or dermal bones) and
  • Seaside bones formed by ossification of tendons.

Ends of long bones are covered with hyaline cartilage. Function of long bones in mammals is to provide support and to produce RBCs and WBCs. Epiphyseal plates at the extremities of long bones help in the elongation of bones. Bones formed by ossification of a tendon is called seamed bones.

Type of Bone Example

  • Long bones Hummers, Radius, Ulna, Femur, Tibia, Fibula.
  • Short bones Carpals and tarsals
  • Flat bones Shull bones, stem urn and ribs
  • Irregular bones Ear fossils (malleus, incus, stapes) and vertebrae.
  • Seaside bones patella (Kneecap) , flabellate and pisiform.

Types of Joints

An articulation or joint is a union between two or move bones in the skeleton. Joints are classified based upon their structure and the kinds of movements which they permit.

Three main types of joints are:

  • Perfect movable joints (Diarthroses)
  • Imperfect movable joints (Amphiarthroses)
  • Immovable joints (Synarthroses)

Perfect Movable Joints

Movable joints are called synovial joints. Synovial joints has a synovial or joint cavity, a space between articulating bones. Articular cartilage covers the surface of articulating bones. The articular cartilage of synovial joint is hyaline cartilage. Synovial joints are also surrounded by a tubular articular capsule. The articular capsule consists of two layers, outer fibrous capsule and inner synovial membrane. The synovial membrane secretes synovial fluid which lubricates and provides nourishment to articular cartilage. In old age, stiffness of joints is due to the decrease in synovial fluid.

Imperfect Movable Joints

  • With or without joint cavities, permits a small amount of movement. Fibrocartilage is placed between the bones. These joints are also called cartilaginous joints.
  • E. g. Between bodies of the vertebrae.
  • Between the manubrium and body of the sternum,
  • Between bones of the public syphilis, Sacroiliac joints in frog.

Immovable Joints

No joints cavity, no movement possible.

These joints include:

  • Sutures: Found between skull bones, Stores are fixed or fibrous joints՚, articulating bones are held together by white fibrous tissue.
  • Composes: Teeth in mandibles, present in premaxillary and maxillary bones.
  • Shindylases: Ethnocide bone in voter (one bone fits into slit in another) .

Classification of Synovial Joints

  • Synovial joints are further classified according to the movements they permit. The main types are ball and socket joints, hinge joints, gliding joints, pivot joint, saddle joints, ellipsoid joints etc.
  • Movements are produced at joints by contractions of skeletal muscles inserted into the articulating bones.

Common Ailments

Fractures

A fracture is any break in a bone. The principle types of fractures are given below:

  • Partial: The break across the bone is incomplete.
  • Complete: The break occurs across the entire bone. The bone is completely broken into two pieces.
  • Closed or Simple: The fractured bone does not break through the skin.
  • Open or Compound: The broken ends of the fractured bone protrude through the skin.
  • Comminuted: The bone is splintered at the site of impact and smaller fragments of bone are found between the two main fragments.
  • Greenstick: A partial fracture in which one side of the bone is broken and the other side bends; it occurs only in children.
  • Spiral: The bone is usually twisted apart.
  • Transverse: A fracture at right angles to the long axis of the bone.
  • Impacted: A fracture is which one fragment is firmly driven into the other.
  • Potty՚s: A fracture of the distal end of the fibula, with serious injury of the distal tibia articulation.
  • Collis: A fracture of the distal end of radius in which the distal fragment is displaced posterior.
  • Displaced: A fracture in which the anatomical alignment of the bone fragment is not preserved.
  • Non- displaced: A fracture in which the anatomical alignment of the bone fragments has not been disrupted.