There are various kinds of skeletons in animals. Such are hydrostatic, exoskeleton and endoskeleton. The skeleton is the frame-work or base on which the body is made of. The various functions of the skeleton in animals comprise: support, protection and locomotion. The skeletal material in mammals is the bone and the skeleton is classified into axial and appendicular skeletons that as well comprise of specialized junctions termed as joints. The relationship among the skeleton and muscles brings about movement (that is, locomotion) in mammals.
Types of Skeletons:
There are mainly three kinds of skeleton as follows:
1) Hydrostatic skeleton: It is located in invertebrates like earthworm. It comprises of body fluid secreted through the body wall into the coelom. The fluid, in combination with the circular and longitudinal muscles of earthworm, functions as the hydrostatic skeleton. The functions of the hydrostatic skeleton comprise: protection, support and movement.
2) Exoskeleton: It is situated externally on the animal. It is basically a protector against dryness. It might cover the whole body surface just similar to the shells of snails, turtle and tortoise. Insects and arthropods as well encompass an exoskeleton.
3) Endoskeleton: It is build up of hard structures, found within the body of animals. The structures are mostly the bones and the soft portions of the body are built on bones. Presence of the endoskeleton is a main feature of the vertebrates.
There are three main kinds of skeletal materials which are:
a) Chitin: This is a main component of the exoskeleton of arthropods. It is a protein-carbohydrate mineral compound identical to cellulose. It is hard, light and flexible.
b) Cartilage: It is a hard elastic tissue which consists of neither blood vessels nor nerves. Its major functions comprise: preventing friction among the two bones, absorbing shock, supporting the protruding portions of the nose and ear, forming main components of the bronchi and trachea.
c) Bone: It comprises of organic (that is, gelatinous) and inorganic (such as magnesium, phosphorus and calcium) materials. The bone is stronger and more firm than cartilage. Shape and size of bone based on its position and function. For illustration the bones of the limbs are long and big, whereas such of the ear (that is, malleus, incus and stapes) are the smallest size bones of the body.
The Mammalian Skeleton:
The human skeleton is comprised of cartilage and bones. There are in all 206 bones. It is classified into two functional portions:
The axial skeleton comprises of bones of the neck, head and vertebral column and rib cage that is in all 80 bones. The axial skeleton protects and supports organs in the dorsal (that is, posterior) and ventral (that is, anterior) body cavities. It gives surface area for the attachment of muscle.
On the other hand, the appendicular skeleton comprises of the bones of the upper and lower limb, comprising the pectoral (shoulder) and pelvic girdles. It gives movement and is 126 bones in all.
Functions of the Skeleton:
1) Support: The skeleton is basically the frame-work of the body and it supports the softer tissues and gives points of attachment for nearly all skeletal muscles.
2) Protection: The skeleton gives mechanical safety for most of the internal organs of the body, decreasing risk of injury to them.
3) Support in Movement: Skeletal muscles are joined to bones, thus when the related muscles contract they cause bones to move.
4) Storage of Minerals: Bone tissues store quite a few minerals, comprising calcium (Ca) and phosphorus (P). Whenever needed, bone releases minerals to the blood - facilitating the balance of minerals into the body.
5) Production of Blood Cells: The red bone marrow within many bigger bones blood cells is produced.
6) Storage of Chemical Energy: With growing age a few bone marrow modifies from red bone marrow to yellow bone marrow. Yellow bone marrow comprises mostly of adipose cells and a few blood cells. It is an important chemical energy reserve.
The place or area where two or more bones meet up is termed as joint. Joints consent to movement. Joints arc held altogether by ligaments. A typical moveable joint consists of:
a) Bones - Which give frame of the joint.
b) Cartilage - Is smooth and rigid, generally present at the end of bone. Cartilage prevents bone from wearing out by decreasing friction among the two bones.
c) Ligaments - It is a strong tissue which holds the bones altogether and prevents them from dislocating.
d) Synovial membrane - It is found on the inner surface of joints and it secretes synovial fluid which lubricates joints.
Types of joints:
1) Hinge joint: It is located at the elbow and knee. It allows angular movement in one direction
2) Ball and socket joint: It is located at the shoulder and hip and it allows multi-directional movement at the shoulder, the head of the humerus (that is, ball-like) fits into the glenoid cavity (that is, socket) of the scapula. Likewise, at the hip, the head of the femur comes into the acetabulum of the pelvis.
3) Pivot joint: It is located among the atlas and axis and it permits only rotational movement, it acts as pivot and consents to head to rotate.
4) Gliding and Sliding joint: It is situated at the wrist and ankle which lets the sliding of bones over one other permits movement of hand and foot up and down and to rotate to some extent.
Movement at the Joints:
1) Locomotion or movement of bones at the joints is caused through muscles.
2) Muscles are involuntary example: cardiac and smooth muscles.
3) It is the skeletal muscles which bring on the subject of movement.
4) Muscles are attached to bones through tendons.
5) Ligaments join bones to bones.
6) Muscles are generally joined to two bones.
7) A pair of muscles is generally antagonistic at the joints.
8) If one contracts then the other loosens up.
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