JOINTS. Types of joint in the skeletal system. Most often we discuss the internal structure of living things and forgetting to talk about the way these things work. we shall be taking a look at the types of joint, the way the joints work to make man effective and some terms found under this topic of joint. So first let’s look at the definition of joint.
DEFINITION OF JOINT
What is a joint?
A joint is a point, place or region where two or more bones meet or articulate. Movement of the body or body parts are made possible through the aid of joints and muscles.
So as it is, there cannot be any effective movement in vertebrates without the joints in place.
Most importantly these joints are held together by ligaments which are made of stiff, partially elastic fibres.
Ligaments join bones to bones. Suffice me to say that the amazing way the internal skeletal system is designed leaves with profound admiration for the creator even though science frowns at the mention of the name God the creator of the universe.
TYPES OF JOINTS FOUND IN THE SKELETAL SYSTEM
There are two main types of joints that can be found in the skeletal system of vertebrates. These are IMMOVABLE/FIXED JOINTS and MOVABLE JOINTS
FIXED OR IMMOVABLE JOINTS
Immovable joints are joints or regions where two or more bones are attached to one to another firmly fixed by ligaments in such a way that movement of these bones is not possible. Examples of places within the body where such joints can be found are the skull and the pelvic girdle. The immovable joints of the skull are called SUTURES
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TYPES OF MOVABLE JOINTS Majorly within the scope of this study, there are four main types of movable joints. These are
i. Ball and socket joint
ii. Hinge joint
iii. Gliding and sliding joint
iv. Pivot joints
BALL AND SOCKET JOINTS
The ball and socket joints allow movements in all planes or directions. This type joint is found in the shoulder and the hip joint. In the shoulder, the head of the humerus is a ball like structure which fits into the glenoid cavity of the scapula-pectoral girdle. This then allows for movement in all direction.
SIMILARLY, IN THE HIP JOINT, THE ROUND HEAD OF THE FEMUR FITS INTO THE ACETABULUM OF THE PELVIC GIRDLE TO FORM A FREELY ARTICULATING JOINT
THE HINGE JOINT
The hinge joint only allow movement in one direction or one plane. An example of hinge joint are found in the elbow and knee joints.
The elbow joint is found the humerus and ulna/radius.
Similarly, the knee joint is found between the femur and tibia/fibula. As the name HINGE implies, each set of bones making up the hinge joint functions like one half of a hinge used for house doors
GLIDING OR SLIDING JOINTS
The gliding joints allows the sliding of bones over one another. These joint are found at the wrist and ankle. They practically allow the hand foot to up and down or to rotate slightly
PIVOT OR ROTATING JOINTS
Pivot joints are that allow nodding or rotation of one part of the body on another. Pivot joint is found between the atlas and axis vertebrae. The odontoid process of the axis allow or acts as a pivot which allows the rotation of the head on the vertebral column. This is the seen in the atlas and the skull together rotates about the odontoid process
HOW THE STRUCTURE OF A JOINTS ADAPTS TO ITS FUNCTION
i. In movable joint, there is the presence of cartilages to reduce friction between bone that are in contact
ii. The ligaments helps to hold the bones together
iii. The SYNOVIAL MEMBRANE secretes the SYNOVIAL FLUID
iv. The synovial fluid helps to lubricate the joints thereby minimizing shock and friction which enhances smooth movement of bone of the joints
THE MAIN PARTS OF A JOINT AND ITS SETUP
The main parts of a joint consist of the following
iLIGAMENTS: these are tough, partly elastic band of tissue. They hold two bones together at a joint. They are able to accommodate movement at the joints because of their elastic nature
the tendons are an extension of connective tissues which surrounds the muscles. Unlike the ligaments, they are non-elastic in nature. They connect muscles to bones
these are found at the surface of bones at the joints. They play the role of cushioning the bones by protecting them from wear and tear during movements. They prevent the articulating surfaces from being worn out due to friction
synovial membrane is responsible for the secretion of the synovial fluid
this is the fluid that is secreted by the synovial membrane. It lubricates the joints thereby reduces shock as well as friction between two bones
capsule is the space in form of sac which contains the synovial fluid
HOW THE MUSCLES ACTS ON BONES TO CAUSE MOVEMENT
SO WHAT ARE MUSCLES?
DEFINITION OF MUSCLE THE MOVEMENT OF FORE-LIMB OR ELBOW JOINT
The muscles of the upper arm on humerus are referred to as BICEPS and TRICEPS.
The bicep muscles are found at the front of the humerus and are attached to the scapula by means of two TENDONS.
The triceps muscles are found at the back of the humerus. The contraction and the relaxation of these muscles bring about bending and straightening of the limb
The muscles of the fore limbs are antagonistic muscles, that is to say they work together in pairs in an opposing way or direction. Whenever an impulse is received from the central nervous, the biceps/flexor contracts by becoming shorter and thicker, and at the same time the extensor/triceps relax.
Now since the TENDONS do not stretch, the shortening of the biceps results in a pull of the radius and this invariably causes the arm to bend
On the other hand, when the triceps muscle/extensor contract, by becoming shorter and thicker at the same time, and the biceps/flexor relaxes, a force is exerted on the ulna and the arm is straightened as a result.
Note that energy is highly involved in the movement of limbs. The muscular energy comes from the oxidation of glycogen which is stored within the muscles also known as TISSUE RESPIRATION
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