Chapter 8: Joints

                This week I am going to go over Chapter 8 from our book which is all about joints! Joints are articulations with the bones of the skeleton and are the weakest part of the actual skeleton. The main functions of the joints are to give the skeleton mobility and also hold the skeleton together, two very important aspects in anatomy and physiology! Joints can be classified into 3 functional classes; Synarthroses, Amphiarthroses (slightly movable), and Diarthroses (freely movable). There are also three types of fibrous structural joints…

1.  Sutures- This type of joints occurs in the skill between the different bones. It is made up of interlocking junctions that is completely filled with connective tissue fiber. This connective tissue fiber helps bind these bones extremely tightly together but yet still allow growth during youth. In the middle age when the skull bones fuse together they are then called synostoses.

2. Synarthroses- these joints are when bone is connected by a fibrous tissue ligament. These types of joints are immovable. Examples of these types of joints are the tibia and fibula in your leg as well as your radius and ulna in your forearm.  The joint between the tibia and fibula don’t move the skeleton however, they still articulate together in order to support each other.

3. Gomphoses- This fibrous structural joint is better described with the name “peg-in-socket.”  An example of this joint is like a tooth and the way it articulates with the alveolar socket. Remember that the fibrous connection in this joint is the periodontal ligament.

Next, I want to discuss the differences between the two types of cartilaginous joints; synchondroses and symphyses. Synchrondroses is a plate of hyaline cartilage brings the bone together. I like to use the root word chrond- to remember that it means cartilage. An example of the synchrondroses cartilaginous joint is the epiphyseal plate of children. This joint in the bone is made of hyaline cartilage so the bone has room to grow outside of the womb. Another example is the joint between the costal cartilage of the first rib and the sternum. Next, the Symphyses cartilaginous joint is when hyaline cartilage covers the bones where they meet and is fused to an pad of fibrocartilage. An example of symphyses joint is the intervertebral joints and also the pubic symphysis of the pelvis. This type of joint is tricky to visualize, I like to picture it almost like a sandwich. You have your fibrocartilage sandwiched by two pieces of hyaline cartilage and then that is sandwiched by 2 bones.

Check back next week for review on chapter 9!

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