BONES OF UPPER LIMB
The pectoral girdle and the bones of the free part of the upper limb make up the superior
appendicular skeleton. The superior appendicular skeleton connects to the axial skeleton only at
the sternoclavicular joint, which permits a high degree of mobility. The clavicles and scapula of
the pectoral girdle are supported, stabilized, and moved by axioappendicular muscles that
attach to the relatively fixed ribs, sternum, and vertebrae of the axial skeleton.
CLAVICLE
The clavicle (collar bone) connects the upper limb to the trunk. The shaft of the clavicle features
a double curve in the horizontal plane: the medial half curves anteriorly and ends in an
enlarged, triangular sternal end that articulates with the manubrium of the sternum at the
sternoclavicular (SC) joint. The lateral half curves anteriorly in the opposite direction and ends in
a flattened acromial end, which articulates with the acromion of the scapula at the
acromioclavicular (AC) joint. The medial two-thirds of the shaft are convex anteriorly, while the
lateral third is flattened and concave anteriorly. These curvatures enhance the clavicle’s strength
and give it the shape of an elongated “S.”
The clavicle serves several key functions:
● It acts as a moveable, crane-like strut that holds the scapula and free limb away from the
trunk, allowing for maximum range of motion. Its mobility also enables the scapula to
glide along the thoracic wall at the scapulothoracic joint, increasing limb mobility. When
fixed in an elevated position, the clavicle can assist with deep inspiration by helping to lift
the ribs.
● It forms part of the bony boundary of the cervico-axillary canal, which protects the
neurovascular structures passing between the neck and the upper limb.
● It transmits mechanical shocks from the upper limb to the axial skeleton.
Although classified as a long bone, the clavicle lacks a medullary cavity. It is composed of
spongy (trabecular) bone surrounded by a shell of compact bone. The superior surface of the
clavicle is smooth, located just beneath the skin and the platysma muscle within the
subcutaneous tissue. In contrast, the inferior surface is roughened by ligament attachments:
● Near the acromial end, the conoid tubercle provides attachment for the conoid ligament,
the medial portion of the coracoclavicular ligament, which passively suspends the upper
limb.
● Adjacent to this is the trapezoid line, where the trapezoid ligament attaches—the lateral
part of the same ligament complex.
● On the medial third of the clavicle’s shaft is the subclavian groove, the attachment site
for the subclavius muscle.
, ● Even more medially lies the impression for the costoclavicular ligament, a rough, oval
area for the ligament that connects the clavicle to the first rib, helping to limit shoulder
elevation.
SCAPULA
The scapula (shoulder blade) is a flat, triangular bone located on the posterolateral surface of
the thorax, covering the 2nd to 7th ribs. The posterior surface of the scapula is convex and
divided by a prominent ridge of bone—the spine of the scapula—into a smaller supraspinous
fossa above and a larger infraspinous fossa below. On the anterior (costal) side, the bone is
concave and forms the broad subscapular fossa. These three fossae serve as attachment sites
for various muscles.
< b/c more powerful muscles attach
The body of the scapula is thin and semi-translucent above and below the spine, while the
borders—especially the lateral one—are thicker. The spine extends laterally into the flat,
expanded acromion, which forms the bony point of the shoulder and articulates with the
acromial end of the clavicle. The deltoid tubercle on the scapular spine marks the medial
attachment of the deltoid muscle. Both the spine and the acromion act as levers for muscle
attachment, especially for the trapezius.
Since the acromion extends laterally, the acromioclavicular (AC) joint is positioned lateral to the
bulk of the scapula and its associated muscles. The glenohumeral (shoulder) joint lies almost
directly beneath the AC joint, creating a balance between the scapular mass and that of the free
limb. The coracoclavicular ligament, which helps suspend the upper limb, is located between
these two masses.
On the lateral side, the scapula features the glenoid cavity, a shallow, oval-shaped socket that
faces anterolaterally and slightly superiorly. This cavity articulates with the head of the humerus
to form the glenohumeral joint. Positioned above the glenoid cavity is the coracoid process, a
hook-like projection that extends anterolaterally and resembles a bent finger. Its "knuckle"
provides attachment for the coracoclavicular ligament, which supports the limb passively.
The scapula has three borders—medial, lateral, and superior—and three angles—superior,
lateral, and inferior. In anatomical position, the medial border lies about 5 cm lateral to the
thoracic spinous processes and is often referred to as the vertebral border. The lateral border
extends superolaterally from the inferior angle toward the axilla, hence the name axillary border.
This lateral border is reinforced by a thick bar of bone to withstand stress and ends at the lateral
angle—the thickest part of the scapula, which contains the broadened head of the bone. The
glenoid cavity is the main feature of the scapular head. A slight narrowing between the head
and body forms the neck of the scapula.
The superior border, the shortest and thinnest of the three, features the suprascapular notch
near the junction of its medial two-thirds and lateral third, where it meets the base of the
coracoid process.
, The scapula moves freely over the thoracic wall at the functional scapulothoracic joint, forming
the base for upper limb motion. These movements, which allow extensive mobility of the arm,
are discussed in more detail alongside the muscles that control scapular motion.
HUMERUS
The humerus, the largest bone of the upper limb, articulates proximally with the scapula at the
glenohumeral joint and distally with the radius and ulna at the elbow joint. At its proximal end,
the humerus features a head, anatomical and surgical necks, and greater and lesser tubercles.
The spherical head of the humerus fits into the glenoid cavity of the scapula, forming the
shoulder joint. The anatomical neck is a groove encircling the head, separating it from the
tubercles, and marking the attachment site of the glenohumeral joint capsule. The surgical neck,
located just below the head and tubercles, is a common site of fractures.
The greater and lesser tubercles mark the transition from the head and neck to the shaft of the
humerus and serve as points of attachment and leverage for scapulohumeral muscles. The
greater tubercle is located laterally, while the lesser tubercle projects anteriorly. Between them
lies the intertubercular (bicipital) groove, which provides a protected passage for the tendon of
the long head of the biceps brachii muscle.
The shaft of the humerus has two notable features: the deltoid tuberosity on its lateral surface,
where the deltoid muscle attaches, and the radial (spiral) groove on the posterior surface. The
radial groove houses the radial nerve and the deep artery of the arm as they pass between the
lateral and medial heads of the triceps brachii.
Toward its distal end, the shaft flares out into the medial and lateral supraepicondylar ridges,
which terminate in the medial and lateral epicondyles—important sites for muscle attachment.
The distal end of the humerus forms the condyle, which includes the trochlea, capitulum, and
three fossae: olecranon, coronoid, and radial.
The condyle contains two articular surfaces: the lateral capitulum, which articulates with the
head of the radius, and the medial, pulley-shaped trochlea, which articulates with the trochlear
notch of the ulna. Above the trochlea are two opposing depressions (fossae). Anteriorly, the
coronoid fossa receives the coronoid process of the ulna during elbow flexion, while posteriorly,
the olecranon fossa accommodates the olecranon of the ulna during elbow extension. Just
above the capitulum, the radial fossa receives the head of the radius when the forearm is fully
flexed.
so its the easiest to
"break" compared
neck = least supported
surgical
to the rest of the bone
The pectoral girdle and the bones of the free part of the upper limb make up the superior
appendicular skeleton. The superior appendicular skeleton connects to the axial skeleton only at
the sternoclavicular joint, which permits a high degree of mobility. The clavicles and scapula of
the pectoral girdle are supported, stabilized, and moved by axioappendicular muscles that
attach to the relatively fixed ribs, sternum, and vertebrae of the axial skeleton.
CLAVICLE
The clavicle (collar bone) connects the upper limb to the trunk. The shaft of the clavicle features
a double curve in the horizontal plane: the medial half curves anteriorly and ends in an
enlarged, triangular sternal end that articulates with the manubrium of the sternum at the
sternoclavicular (SC) joint. The lateral half curves anteriorly in the opposite direction and ends in
a flattened acromial end, which articulates with the acromion of the scapula at the
acromioclavicular (AC) joint. The medial two-thirds of the shaft are convex anteriorly, while the
lateral third is flattened and concave anteriorly. These curvatures enhance the clavicle’s strength
and give it the shape of an elongated “S.”
The clavicle serves several key functions:
● It acts as a moveable, crane-like strut that holds the scapula and free limb away from the
trunk, allowing for maximum range of motion. Its mobility also enables the scapula to
glide along the thoracic wall at the scapulothoracic joint, increasing limb mobility. When
fixed in an elevated position, the clavicle can assist with deep inspiration by helping to lift
the ribs.
● It forms part of the bony boundary of the cervico-axillary canal, which protects the
neurovascular structures passing between the neck and the upper limb.
● It transmits mechanical shocks from the upper limb to the axial skeleton.
Although classified as a long bone, the clavicle lacks a medullary cavity. It is composed of
spongy (trabecular) bone surrounded by a shell of compact bone. The superior surface of the
clavicle is smooth, located just beneath the skin and the platysma muscle within the
subcutaneous tissue. In contrast, the inferior surface is roughened by ligament attachments:
● Near the acromial end, the conoid tubercle provides attachment for the conoid ligament,
the medial portion of the coracoclavicular ligament, which passively suspends the upper
limb.
● Adjacent to this is the trapezoid line, where the trapezoid ligament attaches—the lateral
part of the same ligament complex.
● On the medial third of the clavicle’s shaft is the subclavian groove, the attachment site
for the subclavius muscle.
, ● Even more medially lies the impression for the costoclavicular ligament, a rough, oval
area for the ligament that connects the clavicle to the first rib, helping to limit shoulder
elevation.
SCAPULA
The scapula (shoulder blade) is a flat, triangular bone located on the posterolateral surface of
the thorax, covering the 2nd to 7th ribs. The posterior surface of the scapula is convex and
divided by a prominent ridge of bone—the spine of the scapula—into a smaller supraspinous
fossa above and a larger infraspinous fossa below. On the anterior (costal) side, the bone is
concave and forms the broad subscapular fossa. These three fossae serve as attachment sites
for various muscles.
< b/c more powerful muscles attach
The body of the scapula is thin and semi-translucent above and below the spine, while the
borders—especially the lateral one—are thicker. The spine extends laterally into the flat,
expanded acromion, which forms the bony point of the shoulder and articulates with the
acromial end of the clavicle. The deltoid tubercle on the scapular spine marks the medial
attachment of the deltoid muscle. Both the spine and the acromion act as levers for muscle
attachment, especially for the trapezius.
Since the acromion extends laterally, the acromioclavicular (AC) joint is positioned lateral to the
bulk of the scapula and its associated muscles. The glenohumeral (shoulder) joint lies almost
directly beneath the AC joint, creating a balance between the scapular mass and that of the free
limb. The coracoclavicular ligament, which helps suspend the upper limb, is located between
these two masses.
On the lateral side, the scapula features the glenoid cavity, a shallow, oval-shaped socket that
faces anterolaterally and slightly superiorly. This cavity articulates with the head of the humerus
to form the glenohumeral joint. Positioned above the glenoid cavity is the coracoid process, a
hook-like projection that extends anterolaterally and resembles a bent finger. Its "knuckle"
provides attachment for the coracoclavicular ligament, which supports the limb passively.
The scapula has three borders—medial, lateral, and superior—and three angles—superior,
lateral, and inferior. In anatomical position, the medial border lies about 5 cm lateral to the
thoracic spinous processes and is often referred to as the vertebral border. The lateral border
extends superolaterally from the inferior angle toward the axilla, hence the name axillary border.
This lateral border is reinforced by a thick bar of bone to withstand stress and ends at the lateral
angle—the thickest part of the scapula, which contains the broadened head of the bone. The
glenoid cavity is the main feature of the scapular head. A slight narrowing between the head
and body forms the neck of the scapula.
The superior border, the shortest and thinnest of the three, features the suprascapular notch
near the junction of its medial two-thirds and lateral third, where it meets the base of the
coracoid process.
, The scapula moves freely over the thoracic wall at the functional scapulothoracic joint, forming
the base for upper limb motion. These movements, which allow extensive mobility of the arm,
are discussed in more detail alongside the muscles that control scapular motion.
HUMERUS
The humerus, the largest bone of the upper limb, articulates proximally with the scapula at the
glenohumeral joint and distally with the radius and ulna at the elbow joint. At its proximal end,
the humerus features a head, anatomical and surgical necks, and greater and lesser tubercles.
The spherical head of the humerus fits into the glenoid cavity of the scapula, forming the
shoulder joint. The anatomical neck is a groove encircling the head, separating it from the
tubercles, and marking the attachment site of the glenohumeral joint capsule. The surgical neck,
located just below the head and tubercles, is a common site of fractures.
The greater and lesser tubercles mark the transition from the head and neck to the shaft of the
humerus and serve as points of attachment and leverage for scapulohumeral muscles. The
greater tubercle is located laterally, while the lesser tubercle projects anteriorly. Between them
lies the intertubercular (bicipital) groove, which provides a protected passage for the tendon of
the long head of the biceps brachii muscle.
The shaft of the humerus has two notable features: the deltoid tuberosity on its lateral surface,
where the deltoid muscle attaches, and the radial (spiral) groove on the posterior surface. The
radial groove houses the radial nerve and the deep artery of the arm as they pass between the
lateral and medial heads of the triceps brachii.
Toward its distal end, the shaft flares out into the medial and lateral supraepicondylar ridges,
which terminate in the medial and lateral epicondyles—important sites for muscle attachment.
The distal end of the humerus forms the condyle, which includes the trochlea, capitulum, and
three fossae: olecranon, coronoid, and radial.
The condyle contains two articular surfaces: the lateral capitulum, which articulates with the
head of the radius, and the medial, pulley-shaped trochlea, which articulates with the trochlear
notch of the ulna. Above the trochlea are two opposing depressions (fossae). Anteriorly, the
coronoid fossa receives the coronoid process of the ulna during elbow flexion, while posteriorly,
the olecranon fossa accommodates the olecranon of the ulna during elbow extension. Just
above the capitulum, the radial fossa receives the head of the radius when the forearm is fully
flexed.
so its the easiest to
"break" compared
neck = least supported
surgical
to the rest of the bone
