Anatomy 534 Upper Limb 2: Anatomy of the Arm and Forearm PDF

Anatomy 534 Upper Limb 2 62 The Arm (shoulder to elbow segment of the upper limb musyeutaneous Consists of two well-defined compartments surrounding the...

Anatomy 534 Upper Limb 2 62 The Arm (shoulder to elbow segment of the upper limb musyeutaneous Consists of two well-defined compartments surrounding the Anterienon humerus: flexor (anterior) and extensor (posterior). The iEIE standoff brachial fascia that surrounds so i the arm gives off lateral and medial intermuscular septa that effectively create these I lobotomontties compartments. t Contents of the flexor (anterior) compartment: Fre on Mami if - biceps brachii - coracobrachialis then oddassseetor to - brachialis - brachial a./v. - musculocutaneous n. (motor to flexors) - median n. - proximal ulnar n. c attachment sites dontneed to know Major Muscles of the Flexor (anterior) And Compartment Turk Biceps brachii hI The biceps brachii has two heads: Y.me a long head (supraglenoid tubercle in capsule of shoulder joint) and a shorthead (tip of the coracoid process) The two bellies fuse in the lower aspect of the anterior compartment, the distal flattened tendon crossing the elbow joint to attach to the posterior aspect of the radial tuberosity. As the tendon crosses the elbow Tendon joint an aponeurotic sheet - the bicipital aponeurosis - is given off and passes sina.gg medially across the brachial a. to fuse with the deep fascia of the forearm. This fascia sifss then fuses with the periosteum over the ulna, providing a secondary attachment. Anatomy 534 Upper Limb 2 63 Both heads are supplied by the musculocutaneous n. after it pierces the coracobrachialis. The biceps is a shoulder flexor but its most powerful actions are on the bones of the forearm. It is a strong flexor at the elbow and a powerful supinator of the forearm (screwing on a lid). Contents of the extensor (posterior) compartment: - triceps brachii - terminal br. of profunda brachii - radial n. (motor to extensors) - distal ulnar n. (crosses to posterior) The median and ulnar nn. have no branches in the arm. Major Muscles of the Extensor (flexor) Compartment Triceps brachii Extendsthe arm The sole muscle in this compartment and has3 heads with all 3 bellies fusing into a common tendon that inserts into the olecranon process of the ulna. All 3 heads of the triceps are innervated by branches of the radial n. The triceps is the only effective extensor of the elbow joint (except for gravity) The triceps was used to create the quadrangular and triangular spaces of the shoulder that allowed major structures to pass posteriorly to supply the posterior compartments of the arm and forearm. The Cubital Fossa b An inverted triangular region anterior to the elbow joint. Its base is formed by an ie imaginary line through the medial and lateral epicondyle of the humerus. Its lateral boundary is formed by the brachioradialis while the medial boundary dial side is formed by the pronator teres Anatomy 534 Upper Limb 2 64 The roof of the fossa is skin, superficial fascia and the bicipital aponeurosis of the biceps brachii. The median cubital v. lies superficial to the aponeurosis while the brachial a. lies deep to it. Removal of the roof of the cubital fossa reveals the following structures starting from the lateral (radial) aspect moving medially: - the tendon of the biceps - the brachial a. that terminates I by dividing into the radial ftp.t.iith.ir and ulnar aa. iii - the median n. lies medial to the brachial a. TOO T-A-N mdk.de fiftyᵈᵈiiᵈEEE fof supination The Forearm I I nators mind Like the arm, the forearm has an anterior (flexor) compartment, and a posterior (extensor) 11H11 compartment. However, to put the forearm in the anatomical position, it must be supinated. 1111 S.rs fibrousjoint Cross Section Through Mid Forearm Anatomy 534 Upper Limb 2 65 Muscles of the Flexor Compartment The muscles of the flexor compartment of the forearm are further arranged into superficial and deep groups. The Superficial Group of flexors are innervated by the median n. except for one muscle innervated by the ulnar n. (flexor carpi ulnaris). e The Deep Group of forearm flexors lies mostly undercover of the superficial group. Are and mainly innervated by the median n. The 4 tendons of the flexor digitorum profundus pass into the hand under the flexor retinaculum. The innervation of this muscle is unusual. Its medial part is innervated by the ulnar n. while the lateral part is innervated by the median n. As the names imply, these muscles flex the wrist and digits of the hand. Braa.cat Nerves and Vessels of the yp rotund Flexor Compartment Af The brachial a. enters the forearm through the cubital fossa where it divides into the radial and ulnar aa. 4h The median and ulnar nn. traverse the flexor compartment of the forearm annulled and supply all the muscles within it. The ulnar n. is joined by the ulnar a. on the medial aspect of the compartment The radial n. enters the forearm and EEEE.at national immediately divides into superficial riddhaffy and deep branches. The deep branch de eventually enters the extensor compart- ment. The superficial branch has Esta lodge Eaterite no muscular or cutaneous br. in the Nafld forearm but is cutaneous to the dorsum of the hand. compartment Anatomy 534 Upper Limb 2 66 Muscles of the Extensor Compartment Again, the extensor (posterior) compartment musculature is divided into superficial and deep groups. The Superficial Group of muscles extend the wrist and digits. These muscles are innervated by the radial n. The Deep Group of extensors again lie beneath the superficial group. All except the supinator form long tendons that cross the wrist and enter the hand. Vessels and Nerves of the Extensor Compartment of the Forearm Arteries No major artery reaches the extensor compartment of the forearm from the arm. However, shortly after the ulnar a. is formed in the anterior (flexor) compartment, it gives off a short trunk - the common interosseous a. which then divides into anterior and posterior interosseous aa. Both these vessels supply structures in the extensor compartment. At the upper border of the pronator quadratus the two interossei aa. anastomose and continues into the wrist where it joins the dorsal carpal arch Nerves Two of the extensor mm. of the forearm - the brachioradialis and the extensor carpi radialis longus - are supplied by the radial n. before it divides at the elbow into superficial and deep branches. Palma Dorsal side The Dorsum of the Hand Except for the dorsal interosseous mm., there are no other muscles and Yi an intrinsic to the dorsum. All tendons medifferve encountered in this region arise from muscles with bellies in the ftp A extensor compartment of the forearm. a As these tendons cross the wrist joint they are surrounded by synovial had_ I sheaths and are bound to the dorsal aspect by the extensor retinaculum. Nerves in the Dorsum of the Hand No intrinsic mm. to be innervated on the dorsum so radial and ulnar nn. supply cutaneous innervation Anatomy 534 Upper Limb 2 67 The Palm Beneath the tough, stable tissue of the palm, the fatty superficial fascia is divided into loculi by fibrous septa that anchor the skin to the underlying deep fascia. In the central region of the palm, the deep fascia is continuous with a sheet of fibrous tissue - the palmar aponeurosis. This aponeurosis covers the palm between the thenar and hypothenar eminences. if by tunnel The flexor retinaculum keeps the long flexor tendons close to the wrist and palm during flexion. The retinaculum spans the concave palmar aspect of the carpus, forming an osseofibrous carpal tunnel through which the median nerve and long flexor tendons pass. A septum descends to the underling trapezium forming a separate tunnel for the tendon of the flexor carpi radialis. superficial to 7 a deep one eosteasets thumb I X-section Through the Carpal Tunnel  Anatomy 534 Upper Limb 2 68 The Thenar Eminence The raised region between the wrist and the base of the thumb composed of: - abductor pollicis brevis II ok - flexor pollicis brevis - opponens pollicis All 3 thenar mm. are supplied by the median n. The Hypothenar Eminence Region between the wrist and base of the little finger. It is much less prominent than the thenar eminence Ve and also composed of 3 muscles: THEY - abductor digiti minimi medium - flexor digiti minimi n.ua - opponens digiti minimi thenar All 3 are innervated by the ulnar n. Nerves and Vessels in the Hand The Median Nerve iii Appears from under the flexor retinaculum and gives off a muscular branch that innervates the musculature of the thenar igd.EE eminence. Within the carpal 4To tunnel it was superficial to the long flexor tendons, where pressure on it, or irritation, "carpal tunnel syndrome". Fyfield i Not only do sensory changes occur but also wasting of the thenar mm. The Ulnar Nerve on dorsal side T.IE ttdIIiI The ulnar a. and n. pass lateral to the flexor retinaculum beyond which the nerve divides into a Anatomy 534 Upper Limb 2 69 deep and superficial br. The superficial branch innervates the palmaris brevis and supplies palmar digital nn. to the remaining half of the 4th finger and both sides of the 5th finger. The deep br. of the ulnar n. is another important motor nerve that supplies the muscles of the hypothenar eminence. It also supplies the medial two lumbrical mm. and all the interossei. Both heads of the adductor pollicis are also innervated. The Radial, Ulnar Arteries and the Palmar Arches The radial a. passes from the lateral aspect of the anterior compartment onto the dorsum of the hand, through the anatomical snuff box and then back onto the palm of the hand by passing between the two heads of the adductor pollicis. Here it anastomoses with the deep palmar br. of the ulnar a. to form the deep palmar arch - lying deep to the long flexor tendons. The radial a. is said to be the major contributor to the deep palmar arch. The radial a. also gives off a superficial palmar br. before it passes onto the dorsum of the hand (in the anatomical snuff box). This branch anastomoses with the ulnar a. to help form or complete the superficial My palmar arch - lying just be- neath the palmar aponeurosis. The ulnar a. is said to be the 1 major contributor to the super- ficial palmar arch. may int if 1 deep_ superficial