TYPES OF JOINTS - Skyline E-Learning

JOINTS. Types of joints in the skeletal system.

Most often we discuss the internal structure of living things and forget to talk about the way these things work. we shall be taking a look at the types of joints,

the way the joints work to make an 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.

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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 me 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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MOVABLE JOINTS

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 of 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 directions.

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 allows movement in one direction or one plane. An example of a hinge joint is found in the elbow and knee joints.

The elbow joint is found in 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 allow 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. The Pivot joint is found between the atlas and axis vertebrae.

The odontoid process of the axis allows or acts as a pivot which allows the rotation of the head on the vertebral column. This is 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 cartilage to reduce friction between bones that are in contact
ii. The ligaments help 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 the 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
ligaments: these are tough, partly elastic bands of tissue. They hold two bones together at a joint. They are able to accommodate movement at the joints because of their elastic nature

TENDONS:

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

ARTICULAR CARTILAGE:

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
iv.

SYNOVIAL MEMBRANE:

the synovial membrane is responsible for the secretion of the synovial fluid

SYNOVIAL FLUID:

this is the fluid that is secreted by the synovial membrane. It lubricates the joints thereby reducing shock as well as friction between two bones

CAPSULE:

capsule is the space in the form of a sac which contains the synovial fluid

HOW THE MUSCLES ACT ON BONES TO CAUSE MOVEMENT

SO WHAT ARE MUSCLES?

DEFINITION OF MUSCLE THE MOVEMENT OF THE FORE-LIMB OR ELBOW JOINT

The muscles of the upper arm on the 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 the bending and straightening of the limb

The muscles of the forelimbs 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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