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XXVII. Transverse sections through the left arm

Figs. 1-4. Transverse section through the left arm, through the middle of the lower third of the humerus, through the trochlea, and head of the radius ; male, set.

Embryology - 18 Apr 2024 Expand to Translate
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Braune W. An atlas of topographical anatomy after plane sections of frozen bodies. (1877) Trans. by Edward Bellamy. Philadelphia: Lindsay and Blakiston.

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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding. (More? Embryology History \| Historic Embryology Papers)

THE series of transverse sections from which the present and following plates were taken was made from the left arm of a man set. 40. The arteries were injected. The forearm was slightly flexed and pronated. In order to obtain bearing points for the individual laminae, a line was previously drawn passing through the middle of the biceps over the surface of the supinator longus to the thumb, and the uppermost points of each subsequent lamina lie in this line.

Fig. 1. In this instance the line of section passes through the middle of the arm, and its surface is seen from above downwards, hence we may imagine that we have the stump of an amputation of the right arm for examination, as has been before suggested in speaking of the lower extremity. The section is taken below the insertion of the deltoid, the biceps and triceps occupying the greater space. On the anterior aspect of the bone are portions of the brachialis anticus and coraco-brachialis ; in the middle, to the right of the observer, and between the flexor and extensor muscles, are the great vessels and nerves, and the musculo-spiral nerve has already commenced its tortuous course accompanied by the superior profunda artery. This position of the nerve accounts for the fact that blows or injuries from behind are capable of compressing it so directly upon the humerus that paralysis may be the result. The separation of the muscular masses of the flexors and extensors is already at this level so decided, that the intermuscular aponeurosis appears in the frontal plane. The relation of the individual muscles is so clear as hardly to demand any particular explanation.

Fig. 2 is a section of the left arm in the middle of its lower third. The flexor and extensor muscles lie on both sides of the humerus, and the intermuscular aponeuroses are here still more clearly seen than in the preceding section. In the external intermuscular septum is the musculo-spiral nerve, which has nearly terminated its half turn round the humerus, and behind it is the origin of the supinator longus. On the inner side the ulnar nerve has already become distinct from the great vessels and mass of nerves. The brachial artery is on the inner border of the biceps, accompanied by its venae comites, with the median nerve above it. Although its position is here very easily made out and its compression readily performed, there is great difficulty in isolating it and tying it unless the steps of the operation be carried out very correctly. The vessel, as the plate shows, cannot be directly cut down upon, as on account of nerves and veins which here often very freely anastomose, the operator may be much embarrassed ; and experience has shown that the vessel may be easily missed ; the surgeon must therefore make for the edge of the biceps, which is slightly in front of it, and open its sheath from the inner side, when he will come directly upon it.

The distance of the artery from the bone depends on the development of the brachialis anticus. In this instance, on account of the muscles in relation with it having become more developed, the vessel lies further from the bone than in the preceding section. Compare fig. 1 of this Plate, and also Plates X and XI, fig. 3.

Pig. 3. In this instance the plane of section passes through the lower end of the humerus and the olecranon. On the left side is the commencement of the capitellum with the end of the lateral epicondyle, on the left the trochlea with the middle epicondyle. The olecranon lies behind in the posterior supra-trochlear fossa. The extent of the cavity of the synovial membrane and capsule is indicated by a dark line.

Behind the olecranon is a large bursa between the skin and the tendon of the triceps. On the right, in the furrow between the olecranon and medial epicondyle is the ulnar nerve. To the left of the olecranon is the anconeus. The muscles of the arm are much reduced in bulk at their point of attachment. The origins, however, of the flexors and extensors of the hand and fingers, the pronator teres, and the supinator longus, the latter, on account of its high origin from the humerus, are more powerfully developed in the section. On the anterior aspect of the bones are masses of muscle, on the posterior merely ligaments and tendons, which allow of the bony prominences being clearly distinguished. This relation of the muscular masses, and the position of the vessel on the belly of the brachialis anticus, demonstrates the fact that all incisions which are intended to penetrate the joint should be arranged on its exterior aspect, as it can be here entered without fear of any considerable haemorrhage, and the ulnar nerve alone requires care in looking after.

Fig. 4 is a section of the forearm through the head of the radius, which is clearly shown with the annular ligament, and the upper extremity of the ulna the lesser sigmoid notch of which lies in articulation with the radius. The brachialis anticus is now for the most part tendinous, and attached to the ulna on the other side of its tuberosity. The tendon of the biceps is behind the tuberosity, which lies below the surface of the section, and the bursa, between it and the upper part of this tuberosity, is indicated by a black line. The brachial artery lies in the middle in front of the joint, enclosed by the origin of the flexors and extensors. Its division into radial and ulnar is evident. In front of it is the communication between the superficial and deep veins, and shows why bleeding in this region is so copious, if contraction of the muscles around the deep vein be induced ; it is, however, not possible to expose the intimate relations clearly by section. It may, however, be here explained that the "system" of the median vein does not only associate the trunks of the cephalic and basilic with each other, but also keeps up a communication with the deep veins accompanying the radial and ulnar arteries. The irregularly formed and generally small vein which lies in the bend of the elbow requires no particular note, as it possesses no further importance than the trunks which frequently approach close to the basilic and cephalic in the bend of the forearm. It is, however, worth while to designate this communication, which passes deep down, as median (it is named by Arnold, the deep median vein), and to denominate the oblique branches of communication between the basilic and cephalic as median basilic and median cephalic.

The mass of the flexor muscles is already at this level more strongly developed than in the preceding section. They predominate over the extensors, as will be still more clearly seen in the deeper section of the forearm.

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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding. (More? Embryology History \| Historic Embryology Papers)

Reference

Braune W. An atlas of topographical anatomy after plane sections of frozen bodies. (1877) Trans. by Edward Bellamy. Philadelphia: Lindsay and Blakiston.

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Cite this page: Hill, M.A. (2024, April 18) Embryology Book - An Atlas of Topographical Anatomy 27. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_An_Atlas_of_Topographical_Anatomy_27

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