Elbow + Arms

BONES

In our arms we have a total of 3 bones, per arm, which are the Humerus, Ulna and Radius. The humerus is the upper arm bone, the radius and ulna are found in the forearm. The radius runs in line with the thumb, and the ulna runs in line with the pinky. All 3 of these bones attach together via ligaments.

LIGAMENTS

There are 3 main ligaments in both our elbows which are the medial collateral ligaments, the lateral collateral ligaments and the annular ligaments. 

MUSCLES

Now lets look at the 6 major muscles in the arm, that are involved in the movement of the elbow. 

Muscles Names	Description	Picture
Biceps Brachii	This muscle is located between the shoulder and the elbow, and lies on the upper arm. This muscle is in charge of flexing the arm, and twisting the forearm in order to turn the palm upwards.
Triceps Brachii	This muscle is located at the back of the upper arm. It is in charge of extending the elbow joint (Straightening the arm out) and also helps stabilize the elbow.
Brachioradialis	This muscle is located in the forearm and is in charge of flexing the arm at the elbow.
Anconeus	This muscle is located on the posterior side of the elbow joint and is in charge of helping extend the forearm at the elbow.
Brachialis	This muscle is located in the upper arm and is in charge of helping flex the elbow joint, inwards toward the body.
Pronator Teres	This muscle is located in the forearm, on the palmar side and below the elbow. It is in charge of helping flex the elbow and it also allows pronation of the forearm.

TENDONS

If we look at the tendons in the arm, there are 4 of them. The bicep tendon, tricep tendon, medial epicondyle and lateral epicondyle.

1. Bicep Tendon: This tendon is in charge of attaching the biceps muscle to the radius, at the front of the arm. The bicep tendon allows a person to bend their elbow inwards, towards their body.                                                                                                                          
2. Tricep Tendon: This tendon is in charge of attaching the tricep muscle to the ulna, at the back of the arm. The tricep tendon allows a person to completely straighten out their elbow, away from the body.                                                                                                                           
3. Medial Epicondyle: The medial epicondyle is located at the end of the humerus, on the distal end, and on the inside. It is the medial bump above the elbow. This tendon comes together with the muscles that flex a persons wrist or fingers in order to attach to this area.                                                                                                                                                                                                                             
4. Lateral Epicondyle: The lateral epicondyle is also located at the end of the humerus, on the distal end, and on the outside. It is the lateral bump above the elbow. This tendon comes together with the muscles that extend a persons wrist or fingers in order to attach to this area.                                                                                                                                                                    

ORIGIN AND INSERTION POINTS

Anterior Origins & Insertions

Posterior Origins & Insertions 

JOINTS

Now, looking at the different types of joints, they are classified in 2 ways: Structurally and physically. Structural joints describe what type of material the joint is made up of, and physical joints describe the role of the joint.

STRUCTURAL JOINT CLASSIFICATIONS

There are 3 classifications for the structural joints, which are fibrous joints, cartilaginous joints and synovial joints.

1. Fibrous Joints: These joints are fixed and immovable that are are rich in collagen fibers, and are connected via tough and dense connective tissues. This type of joint would be found in the sutures in the skull.
2.  Cartilaginous Joints: These joints do allow movement, but not as much as synovial joints do. They're connected via hyaline cartilage/fibrocartilage. This type of joint would be found in the vertebrae. 
3. Synovial Joints: These joints are the most movable joints found in the body, which are also the most common. A synovial cavity is found in these joints, and the elbow is actually a type of synovial hinge joint. Connective tissues that are dense and irregular connect to the bones of these joints which forms an articular capsule. This articular capsule surrounds the bones' articulating surfaces. Besides being found in the elbow, this type of joint would be found in the shoulder. 

6 Types of Synovial Joints

• Plane or gliding joints
• Hinge joints
• Pivot joints
• Condyloid joints
• Saddle joints
• Ball-and-socket joints

Functional Joint Classifications

There are 3 classifications for the functional joints, which are synarthrosis joints, amphiarthrosis joints and diarthrosis joints.

1. Synarthrosis joints: These joints include fibrous joints and have limited mobility.
2. Amphiarthrosis joints: These joints include cartilaginous joints and allow a small amount of mobility.
3. Diarthrosis joints: These joints are synovial joints, which are able to move freely.

MOVEMENTS

Moving on to the types of movements that occur at the arms/elbows are flexion, extension, supination and pronation. Since the elbow is a hinge joint, it moves like a door hinge and is able to flex (decrease the angle) or extend (increase the angle). The arm is also able to supinate and pronate at the proximal radio-ulnar joint, rather than happening right at the elbow joint.

BONE MARKINGS

	What is it?	Picture
Capitulum	The capitulum is a smooth articular surface, consisting of a rounded protuberance which is located on the humerus, at the lateral portion and distal end. It articulates with the head of the radius.
Trochlea	The trochlea is the medial portion of the elbow joints articular surface. It articulates with the trochlear notch of the ulna, and by a shallow groove is separated from the capitulum of the humerus.
Lateral Epicondyle	The lateral epicondyle of the humerus, is where muscles and ligaments from the lateral side of elbow attach.
Medial Epicondyle	The medial epicondyle of the humerus, is where muscles and ligaments from the from the medial side of the elbow attach.
Oblique Cord (ligament)	Another name for the oblique cord is the oblique ligament. The oblique cord extends from the lateral side of the ulna's tubercle, at the coronoid process' base to the radius. It is a flattened band that small and extends both distally and laterally. It is a little distal to the radial tuberosity.
Tubercle (tuberosity) of Ulna/Radius	Tubercles/tuberosities are located on the surfaces of bones, which serve as the attachment points of tendons, and they're rough bumps. The brachialis muscles have an attachment point which is the ulnar tuberosity, and the oblique cord attaches to the brachialis muscle. The biceps brachii also have an attachment point which is the radial tuberosity.
Coronoid Process; Olecranon; Trochlear Notch; Radial Notch	The Coronoid process of the ulna projects forwards from proximal and anterior portion of the ulna, and is a triangular eminence. The Olecranon of the ulna projects behind the elbow and is what forms the most pointed part of the elbow. It is a curved and bony eminence. The Trochlear notch is located on the upper side of the ulna, which is a large depression. It fits the trochlea of the humerus. The Radial notch is located on the lateral side of the coronoid process and is a narrow depression of the ulna.