Upper Appendicular Skeleton

Appendicular Skeleton

• The appendicular skeleton consists of 126 bones.

• It is divided into two groups:

• Bones making up the limbs (upper limb and lower limb)

  • Upper limb: bones in the arm, forearm, and hand.

  • Lower limb: bones in the thigh, leg, and foot.

• Bones attaching the limbs to the axial skeleton:

  • Pectoral Girdle: bones attaching the upper limb to the axial skeleton.

  • Pelvic Girdle: bones attaching the lower limb to the axial skeleton.

Upper Limb Bones

• The upper limb consists of the arm, forearm, and hand.

  • Arm: Between the shoulder and the elbow. It consists of the humerus.

  • Forearm: Between the elbow and the wrist. It comprises the radius and ulna.\

  • Hand: Contains carpal bones, metacarpal bones, and phalanges.

Humerus Bone (Arm)

• The humerus is the longest and largest bone of the upper limb.

• The humerus bone has several key features:

  • Proximal end: Head, anatomical neck, surgical neck, greater tubercle, lesser tubercle, intertubercular groove (bicipital groove, bicipital sulcus).

  • Shaft: Deltoid tuberosity.

  • Distal end: Radial fossa, coronoid fossa, capitulum, trochlea, medial epicondyle, lateral epicondyle, olecranon fossa.

Humerus Proximal End (Humerus/Arm)

• Head: Smooth rounded surface that faces medially to articulate with the glenoid fossa of the scapula and form the glenohumeral joint (shoulder joint).

• Anatomical neck: Located below the head.

• Surgical neck: Common site for fractures.

• Greater and Lesser tubercles: Sites for muscle attachment.

• Intertubercular groove (bicipital groove): Passage for the tendon of the biceps brachii muscle.

Humerus Shaft (Humerus/Arm)

• Deltoid Tuberosity: Located in the lateral aspect of the humerus. It is the attachment site for the deltoid muscle.

Humerus Distal End (Humerus/Arm)

• Trochlea: Condyle (smooth, rounded surface) that articulates with the ulna, specifically with the trochlear notch of the ulna. The trochlea is medial to the capitulum.

• Capitulum: Condyle (smooth, rounded surface) that articulates with the radius, specifically with the head of the radius. The capitulum is lateral to the trochlea.

• Medial epicondyle: Site for muscle attachment on the medial aspect of the humerus.

• Lateral epicondyle: Site for muscle attachment on the lateral aspect of the humerus.

• Olecranon fossa: Big indentation found the posterior aspect of the humerus. It receives the olecranon process of the ulna during forearm extension.

• Coronoid fossa: An indentation located above the trochlea. It receives the coronoid process of the ulna during forearm flexion.

• Radial fossa: An indentation located above the capitulum. It receives the head of the radius during forearm flexion.

Radius Bone (Forearm)

• The radius is the most lateral bone in the forearm. The ulna is the most medial one.

• The radius bone has several key features.

  • Proximal end: Head, neck.

  • Shaft: Radial tuberosity.

  • Distal end: Styloid process, ulnar notch.

Radius Proximal End (Radius Bone/Forearm)

• Head: Smooth rounded surface that articulates with the capitulum of the humerus.

Radius Shaft (Radius Bone/Forearm)

• Radial Tuberosity: Attachment site for the biceps brachii muscle.

Radius Distal End (Radius Bone/Forearm)

• Styloid Process: Prominent bony projection.

• Ulnar Notch: A small indentation that articulates with the head of the ulna.

Ulna Bone (Forearm)

• The ulna is the most medial bone in the forearm. The radius is the most lateral one.

• The ulna bone has several key features.

  • Proximal end: Olecranon process (olecranon), trochlear notch, coronoid process, radial notch.

  • Distal end: Head, styloid process.

Ulna Proximal End (Ulna Bone/Forearm)

• Olecranon process (olecranon): A bony protuberance that moves into the olecranon fossa of the humerus during extension and moves out of the olecranon fossa during flexion.

• Trochlear notch: An indentation in the ulna bone (the inside of the U of the ulna bone) that articulates with the trochlea of the humerus bone.

• Coronoid process: A bony protuberance that moves into the coronoid fossa of the humerus during flexion and moves out of the coronoid fossa during extension.

• Radial notch: A small indentation that articulates with the head of the radius.

Ulna Distal End (Ulan Bone/Forearm)

• Head: Smooth rounded surface that articulates with the ulnar notch of the radius.

• Styloid process: Prominent bony projection.

Radius and Ulna Bones Articulation

• Interosscous membrane, proximal radio-ulnar joints, and distal radio-ulnar joints

• These articulations allow pronation and supination of the forearm

• Interosseous membrane

  • Between the shafts of the radius and ulna bones there is an interosseous membrane

• Proximal and Distal Radio-Unar Joint

  • Proximal radio-ulnar joint: head of the radius articulates with the radial notch of the ulna.

  • Distal radio-ulnar joint: head of the ulna articulates with the ulnar notch of the radius.

Humerus, Radius and Ulna Bones Articulation

• These bones articulation form our elbow joint.

• Allow flexion and extension of the forearm.

During Flexion and Extension

• The head of radius articulates with the capitulum of humerus.

• The trochlear notch of ulna articulates with the trochlea of humerus.

Flexion

• The head of radius goes into the radial fossa of humerus.

• The coronoid process of ulna goes into the coronoid fossa of humerus. Consequently, the olecranon process exits the olecranon fossa of the humerus.

Extension

• The head of radius exits the radial fossa of humerus.

• The coronoid process of ulna exits the coronoid fossa of humerus, as the olecranon process goes into the olecranon fossa of the humerus.

Hand Bones

• Carpals: 8 short bones in the wrist, organized into two rows

• Metacarpals: 5 long bones in the palm.

• Phalanges: 14 long bones in fingers and thumb.

Carpals (Hand Bones)

• Bones that form our wrist

• Scaphoid, Lunate, Triquetrum, Pisiform (close to wrist;proximal)

• Trapezium, Trapezoid, Capitate, Hamate (close to fingers;distal)

Metacarpals (Hand Bones)

• Bones that form the palm of our hand.

• Five metacarpal bones numbered one to five starting with the thumb (pollex) side.

  • Metacarpal I: Under the thumb.

  • Metacarpal Il: Under the index finger.

  • Metacarpal III: Under the middle finger.

  • Metacarpal IV: Under the ring finger.

  • Metacarpal V: Under the pinky.

Phalanges

• Bones that form our fingers (and toes).

• Each hand has 14 phalanges: 2 in the thumb (pollex), 3 in each of the other fingers.

• Phalanges: plural; Phalanx: singular.

  • Distal phalanx: The most distant from the torso. Hence, it is at the tip of the fingers.

  • Proximal phalanx: The most proximal to the torso. Hence, it is the phalanx closest to the metacarpal.

  • Middle phalanx: In the middle, between the distal and proximal phalanges.

• The thumb (pollex has only proximal phalanx and distal phalanx.

• Other fingers have proximal phalanx, middle phalanx, and distal phalanx.

Pectoral Girdle

• The pectoral girdle attaches the upper limbs to the axial skeleton.

• The pectoral girdle consists of the scapula and the clavicle.

• The clavicle and the scapula move as a unit!

  • Clavicle is the only bone attaching to the axial skeleton. In other words, the sternoclavicular joint (described below) is the only bony articulation between pectoral girdle and axial skeleton.

  • The single point of attachment of the pectoral girdle with the axial skeleton allows extensive mobility in the shoulder joint - allows great mobility with upper limbs.

Scapula

e scapula is a flat bone with a triangular sha

• Articulates with the humerus via the glenoid fossa and with the clavicle via the acromion process.

The scapula has several key features: spine, supraspinous fossa, infraspinous fossa, subscapular fossa, suprascapular notch, acromion process, coracoid process, glenoid fossa

Scapula Features

• Spine: A ridge in the posterior aspect of the scapula

• Acromion process: A bony protuberance in the lateral aspect of the scapula. The acromiion process articulates with the acromial end of the clavicle

• Supraspinous fossa: A fossa superior to the spine.

• Infraspinous fossa: A fossa inferior to the spine.

• Subscapular fossa: A fossa in the anterior aspect of the scapula.

• Suprascapular notch: A notch at the superior border of the scapula.

• Coracoid process: attachment point for the coracobrachialis muscle.

• Glenoid fossa: A shallow, smooth indentation that faces laterally and articulates with the head of the humerus, forming the conveniently named glenohumeral joint

  • the shoulder joint.

Clavicle

• The clavicle is a long bone, S-shaped, with medial and lateral ends and a shaft.

• The clavicle has two very important features: the sternal end and the acromial end

  • Sternal end: The medial end of the clavicle articulates with the sternum. That is why the medial end of the clavicle receives the anatomical name of stemal end.
    The sternal end of the clavicle and the sternum articulate and form the, conveniently named, sternoclavicular joint.

  • Acromial end: The lateral end of the clavicle articulates with the acromion of the scapula. That is why the lateral end of the clavicle receives the anatomical name of acromial end. The acromial end of the clavicle and the acromion of the scapula articulate and form the, conveniently named, acromioclavicular joint.

Articulations of the Pectoral Girdle

• Glenohumeral joint (shoulder joint): Between the head of the humerus and the glenoid fossa of the scapula.

• Acromioclavicular joint: Between the acromial end of the clavicle and the acromion process of the scapula.

• Sternoclavicular joint: Between the sternal end of the clavicle and the sternum.

• The steroclavicular joint is the only bony articulation between the pectoral girdle and the axial skeleton.