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Posted by Jim True on January 4, 2007 9:46 PM. Last Updated January 10, 2007 10:03 PM

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APP103: Joints & Myology

Definition of a Joint

• Articulationwhere two or more bones come together

3 Types of Joints based on Movement Allowed

1. Synarthrosis: Does not allow any movement. Immovable. Synarthrotic joints.
2. Amphiarthrosis: Some or slight movement, though it may not be visible. Amphiarthrotic joints
3. Diarthrosis: plenty of movement, MOVABLE. Most of the joints in the body are diarthrotic joints

3 Type of Joints by Structure

1. Fibrous Joints
• Suture
• Gomphosis
• Syndesmosis
2. Cartilaginous Joints
• Symphysis
• Synchondrosis
3. Synovial Joints
• Synovial Joint Definition & Structure
• Articular Cartilage
• A Joint Cavity
• Joint Capsule
• Synovial Fluid
• Ligaments

Ranges of Motion for Synovial Joints

We refer to ranges of motion in referring to the plane in which they occur and the body in anatomical position. Movement occurs at a JOINT, not at the limb. ie Knee Flexion. Must name the joint and the type of Range of Motion.

• Flexion: Bending movement in the sagittal plane that moves the bone in the anterior direction, except at the knee. Approximates the two bones (ie brings them closer together), decreasing the angle. Examples: knee flexion, elbow flexion, trunk flexion, flexion of head and neck. hip flexion.
• Extension (opposite of flexion): Return to neutral (ie anatomical position).

• Movements in the Coronal Plane
• Lateral Flexion: Movement into the frontal plane that moves a bone in the lateral direction. Restricted to the axial skeleton. lateral flexion of the head, neck and truck.
• ABduction: Taking away from the midline in the coronal plane. When talking of the fingers, movement is away from the third digit. Taking away (abduct) from the body.
• ADduction: AD, "add it to the body".
• Circumduction: Range of motion in which a cone is circumscribed or circle is created by the distal end. Combination of the movements of flexion, abduction, extension and adduction performed smoothly in succession. Pseudocircumduction (circular rotation of the knee doesn't really occur at the knee, it occurs at the hip. Knee is in flexion).
• Horizontal ABDuction & ADDuction Movement in the transverse plane when the arm or leg moves from the front to the side. Wrist movement TOWARD the ThumB is ABduction.
• Rotation: turning around an axis. Rotate the head and neck.
• Medial Rotation: anterior aspect of the limb is turning TOWARDS the midline. Also called internal rotation. Only at the shoulder and hip, moving the long bones TOWARDS the medial aspect of the body.
• Lateral Rotation: medial aspect of the limb is turning AWAY from the midline. Also called external rotation.
• Contralateral Rotation: Muscle on one side of the body creating rotation to the opposite side of the body.
• Ipsilateral Rotation: Muscle on the same side of the body creating rotation to the right side when contracting. IPSI means same.
• Upward Rotation: Special movement of only the scapula.
• Downward Rotation: Special movement of only the scapula and is the opposite of upward rotation.
• Elevation: undergoes a movement superiorly. Scapula, mandible and hip.
• Depression: undergoes a movement inferiorly. Opposite of Elevation. Opening the mouth causes depression of the mandible.
• Pronation: Movement of the forearm in which rotation of the radius occurs around the ulna. Radius undergoes medial rotation; radius and ulna are crossed.
• Supination: Palms up like a bowl of soup (soup-ination), ie Supination of the forearm.
• Inversion: Movement only occurs at the ankle. Plantar surface of the foot (the sole of the foot) is facing inward towards the midline.
• Eversion: Opposite of Inversion.
• Dorsiflexion: pulling foot forward or lifting. Dorsal surface
• Plantar Flexion: Sole of the foot in Flexion, pointing toe.
• Protraction: Protract (a long way away), pulling away from medial, ABDUCTION of the Scapula. Mandible jutting the jaw foward.
• Retraction: Retract (take something back) the scapula pulls toward the medial, ADDUCTION of the Scapula.

Types of Angular Movements for Synovial Joints

• Nonaxial Movements - slipping or sliding movements in any of three planes. No axis.
• Uniaxial Movements - joint movement in only one plane, the sagittal plane. Flexion & extension.
• Biaxial Movements - joint movement in two planes, sagittal and frontal planes. flexion, extension, abduction & adduction.
• Multiaxial Movements - joint movements in three planes, sagittal, frontal & transverse. Three dimensional joint.

Types of Synovial Joints

• Plane - nonaxial, not restricted in any plane. Intercarpal, intertarsal & intervertebral disc pads.
• Hinge - uniaxial, allow motion in sagittal plane, two cylindrical surfaces (one concave, one convex). Flexion & extension only. Knee & Elbow joints, interphalangeal joints, ankle. TMJ is a combination hinge & plane. Allows for flexion, extension and move from side to side.
• Pivot - uniaxial rotation of a bone around it's own axis. In anatomical position, rotation will be in the transverse plane. One bone has a conical end which protrudes into the sleeve or ring of the other bone. Joint between Atlas & axis, and both proximal and distal radioulnar joints.
• CondyloidBiaxial. Allows for movement in two planes. ROM's include flexion, extension, abduction & adduction. Formed by the union of two oval surfaces, one concave, one convex. Radiocarpal & metacarpophalangeal joints.
• Saddle - biaxial, both articular surfaces have concave & convex regions (like a saddle). Allow for greater movement. Carpometacarpal joint of the thumb, and sternoclavicular joint.
• Ball & Socket - multiaxial, most freely moving joints in the body. Capable of ROM's in all three axes. One surface is spherically convex (like a ball), other is spherically concave (like a socket). Shoulder & hip joints are the only ball & socket joints.

Muscle Functions & definition of Myology

• Myology - Study of the function and structure of muscles.
• Four Functions of the Muscles (formed by the contractions)
1. Movement of bones at the joints
2. Joint Stability
3. Maintenace of Posture
4. Heat generation

Muscle Structure

• Muscle is an organ because it's made of multiple tissues joined together for a common function.
• Individual muscles cells are called fibers
• Cylindrical cell shape that can be quite long
• Three Layers of connective tissue help to make fascia for the muscle (pg 113 in Memmloer's
1. Endomysium - tissue wrapper around each individual muscle cell or fiber. (like a single wrapping around a burito.
2. Perimysium - Group of fibers (in their endomysium) collected together and are wrapped by perimysium. This bundle is called a fascicle. (like a bag with a 5 pack of burrito's).
3. Epimysium - Superficial layer of connection tissue around a group of fascicles. This is the muscle or muscle belly. Epimysium forms the tendons that connect the muscle to the bone.

Muscle Attachments

• Connection to the Nervous System
• Neuromuscular Junction (pg 115 in Memmler's)
• Synaptic Cleft - the gap between the axon of the motor neuron and the muscle
• Motor Unit
• Acetylcholine - Neurotransmitter for activating motor neurons at the neuromuscular junction.
• Connections to the Bone

  Muscles are based on a lever system. Bones serve as levers and the joints serve as fulchrum. Muscles provide force for the movement; Muscles always pull; they NEVER push.. Contraction of a muscle tissues fibers shorten the length of the muscle and this causes movement by pulling upon TWO bones across their joint. One bone must remain statinoary while the other undergoes movement.

  • Origin bone that stays in place is the origin.
  • Insertion bone that undergoes is the site of insertion.

Muscle Groups

Muscle pairs in opposite.

• Prime Mover - one primary muscle that does the work of movement at a joint.
• Agonist - Two muscles performing the SAME action in a movement.
• Antagonist - Two muscles performing opposing actions in a movement.
• Synergist - Different ROM, but assisting by stabilizing the Prime Mover. Contribute to the movement of the Prime mover, or assist to stabilize the move. Stabilize a prime mover's site of origin.
• Muscle Roles

Muscle Shapes

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