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By the end of this section, you will be able to:
  • Classify the different types of joints on the basis of structure
  • Explain the role of joints in skeletal movement

The point at which two or more bones meet is called a joint    , or articulation    . Joints are responsible for movement, such as the movement of limbs, and stability, such as the stability found in the bones of the skull.

Classification of joints on the basis of structure

There are two ways to classify joints: on the basis of their structure or on the basis of their function. The structural classification divides joints into bony, fibrous, cartilaginous, and synovial joints depending on the material composing the joint and the presence or absence of a cavity in the joint.

Fibrous joints

The bones of fibrous joints are held together by fibrous connective tissue. There is no cavity, or space, present between the bones and so most fibrous joints do not move at all, or are only capable of minor movements. There are three types of fibrous joints: sutures, syndesmoses, and gomphoses. Sutures are found only in the skull and possess short fibers of connective tissue that hold the skull bones tightly in place ( [link] ).

Illustration shows sutures that knit the back part of the skull together with the front and lower parts.
Sutures are fibrous joints found only in the skull.

Syndesmoses are joints in which the bones are connected by a band of connective tissue, allowing for more movement than in a suture. An example of a syndesmosis is the joint of the tibia and fibula in the ankle. The amount of movement in these types of joints is determined by the length of the connective tissue fibers. Gomphoses occur between teeth and their sockets; the term refers to the way the tooth fits into the socket like a peg ( [link] ). The tooth is connected to the socket by a connective tissue referred to as the periodontal ligament.

Illustration shows a gomphosis connecting a tooth to the jaw. The gomphoses have a porous appearance.
Gomphoses are fibrous joints between the teeth and their sockets. (credit: modification of work by Gray's Anatomy)

Cartilaginous joints

Cartilaginous joints are joints in which the bones are connected by cartilage. There are two types of cartilaginous joints: synchondroses and symphyses. In a synchondrosis    , the bones are joined by hyaline cartilage. Synchondroses are found in the epiphyseal plates of growing bones in children. In symphyses , hyaline cartilage covers the end of the bone but the connection between bones occurs through fibrocartilage. Symphyses are found at the joints between vertebrae. Either type of cartilaginous joint allows for very little movement.

Synovial joints

Synovial joints are the only joints that have a space between the adjoining bones ( [link] ). This space is referred to as the synovial (or joint) cavity and is filled with synovial fluid. Synovial fluid lubricates the joint, reducing friction between the bones and allowing for greater movement. The ends of the bones are covered with articular cartilage, a hyaline cartilage, and the entire joint is surrounded by an articular capsule composed of connective tissue that allows movement of the joint while resisting dislocation. Articular capsules may also possess ligaments that hold the bones together. Synovial joints are capable of the greatest movement of the three structural joint types; however, the more mobile a joint, the weaker the joint. Knees, elbows, and shoulders are examples of synovial joints.

Questions & Answers

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Bernard
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Mahmud Reply
Plasma membrane or Cell membrane is the outer layer of tissue surrounding the whole or part of an organ. in addition, it is the outer flexible or semi-flexible covering or waterproofing whose primary function is to exclude water.(usually in plants and animals).
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h20
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Skeleton is the structural frame work of the body
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Skeleton is the internal bony framework of the body of living organisms.
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As the bladder fills up .. the signals are sent to the brain specifying that its filling up and should be emptied and the fuller it gets, the more signals/ alerts are sent to brain ...leading to the urge to urinate .... to go pee
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photosynthesis is the process where by Green manufacture their own food with the help of energy from the sun
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also known as syngamy
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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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