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Kin 3305 EXam 2 part 3

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created 1 year ago by denisel1995
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updated 1 year ago by denisel1995

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1

The four bones that relate to the function of the elbow and forearm complex

1) scapula

2) distal humerus

3) ulna

4) radius

2

Scapula – has three bony features that are important to the muscles of the elbow

- Coracoid process – serves as the proximal attachment for the short head of the biceps

- Supraglenoid tubercle – serves as the proximal attachment for the long head of the biceps

- Infraglenoid tubercle – marks the proximal attachment for the long head of the triceps

3

Radius – only the radius interacts with wrist joint

- The radial head is shaped like a wide disc on the proximal end of the radius

- The superior surface of the radial head consists of a shallow, cup-shaped depressed called the fovea that articulates with the capitulum of the humerus, forming the humeroradial joint

- The radial tuberosity, is an enlarged ridge of bone located on the anterior-medial aspect of the proximal radius

  • The primary distal attachment for the biceps brachii
4

Radius (cont.)

- The distal end of the radius is wide and flat with two notable structures: the styloid process and the ulnar notch

  • The styloid process is the pointed (and easily palpated) projection of bone off the distal lateral radius
  • The ulnar notch is a small depression on the medial side of the distal radius that articulates with the ulnar head, forming the distal radioulnar joint
5

Ulna

- The olecranon process is the large, blunt, proximal top of the ulna commonly referred to as the elbow bone

  • The rough posterior surface of the olecranon process is the distal attachment for the triceps muscles

- The trochlear notch is the large, jaw-like curvature of the proximal ulna that articulates with the trochlea (of the humerus), forming the humeroulnar joint

6

Ulna (cont.)

- The coronoid process strengthens the articulation of the humeroulnar joint by firmly grabbing the trochlea of the humerus

- Slightly inferior and lateral to the trochlear notch is the radial notch, which articulates with the head of the radius to form the proximal radioulnar joint

7

Ulna (cont.)

- Ulnar tuberosity – gives insertion to a part of the brachialis

- Antebrachial interosseous membrane (between bones) – fibrous sheet that connects the interosseous margins of the radius and the ulna

- Ulnar head

- Located distally, the styloid process is a pointed projection of bone that arises from the ulnar head

  • Both of these structures can be palpated on the ulnar side of the dorsum of the wrist, with the forearm fully pronated
8

Elbow joint (general features)

- The humeroulnar joint provides most of the structural stability to the elbow as a whole

- The humeroradial joint is formed by the ball-shaped capitulum of the humerus articulating with the bowl-shaped fovea of the radius

- The primary function of the collateral ligaments is to limit excessive varus and valgus deformations of the elbow

  • The medial collateral ligament is most often injured during attempts to catch oneself from a fall
9

Supporting structures of the elbow joint

- Medial collateral ligament – contains fibers that attach proximally to the medial condyle and distally to the medial aspects of the coronoid and olecranon processes

  • Provide stability primarily by resisting cubitus valgus
  • This ligament is also called the ulnar collateral ligament

- Lateral collateral ligament – originates on the lateral epicondyle and ultimately attaches to the lateral aspect of the proximal forearm

  • These fibers provide stability to the elbow by resisting cubitus varus
  • This ligament is also referred to as the radial collateral ligament
10

Elbow joint (kinematics)

- From the anatomic position, elbow flexion and extension occur in the sagittal plane about a medial-lateral axis of rotation, which courses through both epicondyles

  • The range of motion at the elbow normally spans from 5 degrees beyond extension and 145 degrees of flexion
11

Forearm (general features)

- The forearm is composed of the proximal and distal radioulnar joints

  • These joints are located at the proximal and distal ends of the forearm

- Pronation and supination occur as a result of motion at each of these two joints

  • In full supination, the radius and ulna lie parallel to one another
  • However, in full pronation, the radius crosses over the ulna

- Pronation and supination involve the radius rotating around a relatively fixed ulna

12

Supporting structures of the proximal and distal radioulnar joints

- Annular ligament – a thick circular band of CT that wraps around the radial head and attaches to either side of the radial notch of the ulna

  • This ring-like structure holds the radial head firmly against the ulna, allowing it to spin freely during supination and pronation

- Interosseous membrane – helps bind the radius to the ulna; serves as a site for muscular attachments, and as a mechanism to transmit forces proximally through the forearm

13

Forearm (kinematics)

- Supination occurs in many functional activities that require the palm to be turned up, such as feeding, washing the face, or holding a bowl of soup

- Pronation is involved with activities such as grabbing an object from a table or pushing up from a chair, which require the palm to be faced down

- Supination and pronation occur as the radius rotates around an axis of rotation that travels from the radial head to the ulnar head

  • The 0-degree or neutral position of the forearm is the thumb-up position
14

Innervation of muscles

- The musculocutaneous nerve supplies two of the elbow flexors: the biceps brachii and the brachialis

- The radial nerve supplies all of the muscles that extend the elbow and wrist, plus the supinator and the brachioradialis muscles

- The median nerve supplies all the pronators of the forearm, as well as numerous wrist flexor muscles

- The ulnar nerve innervates the flexor carpi ulnaris, as well as most of the intrinsic muscles of the hand

15

Elbow flexors

- These muscles have a line of force that passes anterior to the elbow’s axis of rotation

- The pronator teres is considered a secondary elbow flexor

- Three of the four flexors also have the potential to pronate or supinate the forearm

  • Any elbow flexor muscle that attaches distally to the radius (versus the ulna) will aso pronate or supinate the forearm
16

Biceps brachii (3 joint muscle)

(elbow flexor)

(anterior arm)

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- Proximal attachment:

  • Long head – supraglenoid tubercle of the scapula
  • Short head – coracoid process of the scapula

- Distal attachment: bicipital tuberosity of the radius

- Innervation: musculocutaneous nerve

Actions: elbow flexion, forearm supination, shoulder flexion

17

Brachialis (deep to biceps brachii) – “workhouse” of the elbow flexors

(elbow flexor)

(anterior arm)

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- Attachments: anterior aspect of the distal humerus & coronoid process of the ulna

- Innervation: musculocutaneous nerve

- Action: elbow flexion

18

Brachioradialis

(elbow flexor)

(anterior arm)

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- Attachments: lateral supracondylar of the humerus & near the styloid process of the distal radius

- Innervation: radial nerve

- Actions: elbow flexion, pronating or supinating the forearm to the neutral (thumb-up) position

19

Triceps brachii

(elbow extensor)

(posterior arm)

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- Proximal attachment

  • Long head – infraglenoid tubercle of the scapula
  • Lateral head – posterior aspect of the superior humerus, lateral to the radial groove
  • Medial head – posterior aspect of the superior humerus, medial to the radial groove

- Distal attachment: olecranon process of the ulna

- Innervation: radial nerve

- Actions: elbow extension, shoulder extension (long head only)

20

Anconeus

(elbow extensor)

(posterior arm)

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- Attachments: posterior aspect of the lateral epicondyle of the humerus & olecranon process of the ulna

- Innervation: radial nerve

- Action: elbow extension

21

Forearm supinators and pronators (radio-ulnar joint)

Muscles that supinate or pronate the forearm must meet at least two requirements:

  • 1) the muscles must originate on the humerus or the ulna, or both, and must insert on the radius or the hand
  • 2) the muscles must have a line of force that intersects (versus parallels) the axis of rotation of the forearm joints
22

Supinators of the forarm

  • The primary supinator muscles are the biceps brachii and the supinator muscle
  • Secondary supinator muscles include the extensor pollicis longus and the extensor indicis
23

Supinator

(forearm supinator)

(radio-ulnar joint)

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- Attachments: lateral epicondyle of the humerus and spinator crest of the ulna & lateral surface of the proximal radius

- Innervation: radial nerve

- Action: forearm supination

24

Pronators of the forearm

  • The primary pronator muscles are the pronator teres and the pronator quadratus
  • Secondary pronators are the flexor carpi radialis and the palmaris longus
25

Pronator teres

(forearm pronator)

(radio-ulnar joint)

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- Proximal attachment:

  • Humeral head – medial epicondyle of the humerus
  • Ulnar head – just medial to the tuberosity of the ulna

- Distal attachment: lateral surface of the mid radius

- Innervation: median nerve

- Actions: forearm pronation, elbow flexion

26

Pronator quadratus

(forearm pronator)

(radio-ulnar joint)

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- Attachments: anterior surface of the distal ulna & anterior surface of the distal radius

- Innervation: median nerve

- Action: forearm pronation


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