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NEET PG Anatomy Notes|Upper limb|Part 1
Bones and Joints of the upper limb
Topics:-
1.Bones of the shoulder girdle
2.Bones of the arm and forearm
3.Bones of the hand
4.Joints and ligaments of the upper limb


1.BONES OF THE SHOULDER GIRDLE
(A) Clavicle (Collarbone)

■ Is a commonly fractured bone that forms the pectoral (shoulder) girdle with the scapula, which connects the upper limb to the sternum (axial skeleton), by articulating with the sternum at the sternoclavicular joint and with the acromion of the scapula at the acromioclavicular.

■ Is the first bone to begin ossification during fetal development, but it is the last one to complete ossification, at approximately 21 years of age.

■ Is the only long bone to be ossified intramembranously and forms from somatic lateral plate mesoderm.

(B) Scapula (Shoulder Blade)

1. Spine of the Scapula

■ Is a triangular-shaped process that continues laterally as the acromion.

■ Divides the posterior scapula into the upper supraspinous and lower infraspinous fossae, and also provides an origin for the deltoid and an insertion for the trapezius.

2. Acromion

■ Is the lateral end of the spine and articulates with the clavicle.

■ Provides an origin for the deltoid and an insertion for the trapezius.

3. Coracoid Process

■ Provides the origin of the coracobrachialis and short head of biceps brachii, the insertion of the pectoralis minor, and the attachment site for the coracoclavicular, coracohumeral, and coracoacromial ligaments and the costocoracoid membrane.

4.Scapular Notch

■ Is bridged by the superior transverse scapular ligament and converted into a foramen that transmits the suprascapular nerve.

5. Glenoid Cavity

Is deepened by the glenoid labrum for the head of the humerus.

6. Supraglenoid and Infraglenoid Tubercles

Provide origins for the tendons of the long heads of the biceps brachii and triceps brachii muscles, respectively.



 

2.BONES OF THE ARM AND FOREARM
(A) Humerus 

1. Head

■ Articulates with the scapula at the glenohumeral joint.

2. Anatomic Neck

■ Is an indentation distal to the head and provides an attachment for the fibrous joint capsule.

3. Greater Tubercle

■ Lies just lateral and distal to the anatomic neck and provides attachments for the supraspinatus, infraspinatus, and teres minor muscles.

4.Lesser Tubercle

■ Lies on the anterior medial side of the humerus, just distal to the anatomic neck, and provides an insertion for the subscapularis muscle.

5. Intertubercular (Bicipital) Groove

■ Lies between the greater and lesser tubercles, lodges the tendon of the long head of the biceps brachii muscle, and is bridged by the transverse humeral ligament.

■ Provides insertions for the pectoralis major on its lateral lip, the teres major on its medial lip, and the latissimus dorsi on its floor.

6. Surgical Neck

■ Is a narrow area distal to the tubercles that is a common site of fracture and is in contact with the axillary nerve and the posterior humeral circumflex artery.

7. Deltoid Tuberosity

■ Is a rough triangular elevation on the lateral aspect of the midshaft that marks the insertion of the deltoid muscle.

8. Spiral Groove

■ Contains the radial nerve, separating the origin of the lateral head of the triceps above and the origin of the medial head below.

9.Trochlea

■ Is a spool-shaped medial articular surface and articulates with the trochlear notch of the ulna.

10. Capitulum

■ Is the lateral articular surface, globular in shape, and articulates with the head of the radius.

11. Olecranon Fossa

■ Is a posterior depression above the trochlea of the humerus that houses the olecranon of the ulna on full extension of the forearm.

12. Coronoid Fossa

■ Is an anterior depression above the trochlea of the humerus that accommodates the coronoid process of the ulna on flexion of the elbow.

13. Radial Fossa

■ Is an anterior depression above the capitulum that is occupied by the head of the radius during full flexion of the elbow joint.

14. Lateral Epicondyle

■ Projects from the capitulum and provides the origin of the supinator and extensor muscles of the forearm. It is an attachment site for the radial collateral ligament.

15. Medial Epicondyle

■ Projects from the trochlea and has a groove on the back for the ulnar nerve and superior ulnar collateral artery.

■ Provides attachment sites for the ulnar collateral ligament, the pronator teres, and the common tendon of the forearm flexor muscles

(B) Radius 

■ Is shorter than the ulna and is situated lateral to the ulna.

1. Head (Proximal End)

■ Articulates with the capitulum of the humerus and the radial notch of the ulna and is surrounded by the annular ligament.

2. Neck

■ Is enclosed by the lower margin of the annular ligament, and the neck and head are free from capsular attachment and thus can rotate freely within the socket.

3. Distal End

■ Articulates with the proximal row of carpal bones, including the scaphoid, lunate, and triquetral bones but excludes the pisiform bone.

4. Radial Tuberosity

■ Is an oblong prominence just distal to the neck and provides an attachment site for the biceps brachii tendon.

5. Styloid Process

■ Is located on the distal end of the radius and is approximately 1 cm distal to that of the ulna and provides insertion of the brachioradialis muscle.

■ Can be palpated in the proximal part of the anatomic snuffbox between the extensor pollicis longus and brevis tendons.

(C) Ulna 

1.Olecranon

■ Is the curved projection on the back of the elbow that provides an attachment site for the triceps tendon.

2. Coronoid Process

■ Is located below the trochlear notch and provides an attachment site for the brachialis.

3. Trochlear Notch

■ Receives the trochlea of the humerus.

4. Ulnar Tuberosity

■ Is a roughened prominence distal to the coronoid process that provides an attachment site for the brachialis.

5. Radial Notch

■ Accommodates the head of the radius at the proximal radioulnar joint.

6. Head (Distal End)

■ Articulates with the articular disk of the distal radioulnar joint and has a styloid process.



3.BONES OF THE HAND
(A) Carpal Bones 

■ Are arranged in two rows of four (lateral to medial): scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, and hamate (mnemonic device: Sandra Likes To Pat Tom’s Two Cold Hands). (Trapezium precedes trapezoid alphabetically.)

1. Proximal Row (Lateral to Medial): Scaphoid, Lunate, Triquetrum, and Pisiform

■ Except for the pisiform, articulates with the radius and the articular disk (the ulna has no contact with the carpal bones). The pisiform is said to be a sesamoid bone contained in the flexor carpi ulnaris tendon.

2. Distal Row (Lateral to Medial): Trapezium, Trapezoid, Capitate, and Hamate

(B) Metacarpals

■ Are miniature long bones consisting of bases (proximal ends), shafts (bodies), and heads (distal ends). Heads form the knuckles of the fist.

(C) Phalanges

■ Are miniature long bones consisting of bases, shafts, and heads. The heads of the proximal and middle phalanges form the knuckles.

■ Occur in fingers (three each) and thumb (two).



4.JOINTS AND LIGAMENTS OF THE UPPER LIMB
(A) Acromioclavicular Joint

■ Is a synovial plane joint that allows a gliding movement when the scapula rotates and is reinforced by the coracoclavicular ligament, which consists of the conoid and trapezoid ligaments.

(B) Sternoclavicular Joint

■ Is a double synovial plane (gliding) joint united by the fibrous capsule.

■ Is reinforced by the anterior and posterior sternoclavicular, interclavicular, and costoclavicular ligaments.

■ Allows elevation and depression, protraction and retraction, and circumduction of the shoulder

(C) Shoulder (Glenohumeral) Joint

■ Is a synovial ball-and-socket joint between the glenoid cavity of the scapula and the head of the humerus. Both articular surfaces are covered with hyaline cartilage.

■ Is surrounded by the fibrous capsule that is attached superiorly to the margin of the glenoid cavity and inferiorly to the anatomic neck of the humerus. The capsule is reinforced by the rotator cuff, the glenohumeral ligaments, and the coracohumeral ligaments.

■ Has a cavity that is deepened by the fibrocartilaginous glenoid labrum; communicates with the subscapular bursa; and allows abduction and adduction, flexion and extension, and circumduction and rotation.

■ Is innervated by the axillary, suprascapular, and lateral pectoral nerves.

■ Receives blood from branches of the suprascapular, anterior and posterior humeral circumflex, and scapular circumflex arteries.

■ May be subject to inferior or anterior dislocation, which stretches the fibrous capsule, avulses the glenoid labrum, and may injure the axillary nerve.

1.Rotator (Musculotendinous) Cuff 

■ Is formed by the tendons of the supraspinatus, infraspinatus, teres minor, and subscapularis (SITS); fuses with the joint capsule; and provides mobility.

■ Keeps the head of the humerus in the glenoid fossa during movements and thus stabilizes the shoulder joint.

 2.Ligaments of the shoulder joint

(a) Glenohumeral Ligaments

■ Extend from the supraglenoid tubercle to the upper part of the lesser tubercle of the humerus (superior glenohumeral ligament), to the lower anatomic neck of the humerus (middle glenohumeral ligament), and to the lower part of the lesser tubercle of the humerus (inferior glenohumeral ligament).

(b) Transverse Humeral Ligament

■ Extends between the greater and lesser tubercles and holds the tendon of the long head of the biceps in the intertubercular groove.

(c) Coracohumeral Ligament

■ Extends from the coracoid process to the greater tubercle.

(d) Coracoacromial Ligament

■ Extends from the coracoid process to the acromion.

(e) Coracoclavicular Ligament

■ Extends from the coracoid process to the clavicle and consists of the trapezoid and conoid ligaments.

3. Bursae around the Shoulder

■ Form a lubricating mechanism between the rotator cuff and the coracoacromial arch during movement of the shoulder joint.

(a) Subacromial Bursa

■ Lies between the coracoacromial arch and the supraspinatus muscle, usually communicates with the subdeltoid bursa, and protects the supraspinatus tendon against friction with the acromion.

(b) Subdeltoid Bursa

■ Lies between the deltoid muscle and the shoulder joint capsule, usually communicates with the subacromial bursa, and facilitates the movement of the deltoid muscle over the joint capsule and the supraspinatus tendon.

(c) Subscapular Bursa

■ Lies between the subscapularis tendon and the neck of the scapula and communicates with the synovial cavity of the shoulder joint.

(D) Elbow Joint

■ Forms a synovial hinge joint, consisting of the humeroradial and humeroulnar joints, and allows flexion and extension. It also includes the proximal radioulnar (pivot) joint, within a common articular capsule

■ Is innervated by the musculocutaneous, median, radial, and ulnar nerves.

■ Receives blood from the anastomosis formed by branches of the brachial artery and recurrent branches of the radial and ulnar arteries.

■ Is reinforced by the following ligaments:

1. Annular Ligament

■ Is a fibrous band that is attached to the anterior and posterior margins of the radial notch of the ulna and forms nearly four-fifths of a circle around the head of the radius; the radial notch forms the remainder.

■ Encircles the head of the radius and holds it in position and fuses with the radial collateral ligament and the articular capsule.

2. Radial Collateral Ligament

■ Extends from the lateral epicondyle to the anterior and posterior margins of the radial notch of the ulna and the annular ligament of the radius.

3. Ulnar Collateral Ligament

■ Is triangular and is composed of anterior, posterior, and oblique bands.

■ Extends from the medial epicondyle to the coronoid process and the olecranon of the ulna.

E. Proximal Radioulnar Joint

■ Forms a synovial pivot joint in which the head of the radius articulates with the radial notch of the ulna and allows pronation and supination by permitting the head of radius to rotate within the encircling annular ligament.

F. Distal Radioulnar Joint

■ Forms a synovial pivot joint between the head of the ulna and the ulnar notch of the radius and allows pronation and supination.

G.Wrist (Radiocarpal) Joint

■ Is a synovial condylar joint formed superiorly by the radius and the articular disk and inferiorly by the proximal row of carpal bones (scaphoid, lunate, and rarely triquetrum).

■ Its capsule is strengthened by radial and ulnar collateral ligaments and dorsal and palmar radiocarpal ligaments, and it allows flexion and extension, abduction and adduction, and circumduction.

H. Midcarpal Joint

■ Forms a synovial plane joint between the proximal and distal rows of carpal bones and allows gliding and sliding movements.

I. Carpometacarpal Joints

■ Form synovial saddle (sellar) joints between the carpal bone (trapezium) and the first metacarpal bone, allowing flexion and extension, abduction and adduction, and circumduction.

■ Also form plane joints between the carpal bones and the medial four metacarpal bones, allowing a simple gliding movement.

J. Metacarpophalangeal Joints

■ Are condyloid joints that allow flexion and extension, and abduction and adduction.

K. Interphalangeal Joints

■ Are hinge joints that allow flexion and extension

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