Research On Human Anterior Muscles Of Upper Arm About The Muscle Architecture, The Distribution Of Intramuscular Nerves, The Nerve-entering Points And Muscle Spindles

Objective: To provide a detailed morphologic data for further studying the physiological function and clinical application of anterior muscles of upper arm by researching into those muscles' architecture, the distribution of intramuscular nerves, nerve-entering points and muscle spindles.Methods : 1 .To obtain bilateral anterior muscles of upper arm completely from 6 adult cadavers which have been fixed by formalin . First to observe the shape, enthesis and arrangement form of muscle bundles of anterior muscles of upper arm. And then to study the muscle architecture of the muscles.2. To obtain bilateral anterior muscles of upper arm completely from 2 child cadavers and 3 adult cadavers which have been fixed by formalin. To deal with those muscles with modified Sihler's staining technique and then observe the distribution of anterior muscles of upper arm's intramuscular nerve branches.3.To choose lateral epicondyle humeri, medial epicondyle humeri and greater tubercle as survey mark and measure vertical dimension between nerve-entering point and the line between lateral epicondyle humeri and medial epicondyle humeri. To measure vertical dimension between nerve-entering point and horizontal line which passes greater tubercle.4. To draw the materials of anterior muscles of upper arm's middle part respectively. Then to deal with those materials with HE staining technique and stereology in order to further study the muscle spindle distribution of anterior muscles of upper arm.Results: 1. The architectural feature of the anterior muscles of the upper arm: Muscle Weight: the long head of biceps brachii was 81.72±23.26g, the short head was 67.20±20.43g brachialis was 158.44±34.00g and coracobrachialis was 47.93±15.16g; Fiber Length: the long head of biceps brachii was 9.32±0.77cm, the short head was 10.24±0.70cm, brachialis was 8.09±0.35cm coracobrachialis was 16.75±3.07cm; Pinnation Angle: the long head of biceps brachii, the short head and brachialis were 0, coracobrachialis was 20.8±3.06°. Cross Section Area (CSA) : the long head of biceps brachii was 9.26±1.34 cm~2, the short head was 6.93±0.37cm~2, brachialis was 20.69±1.56cm~2 and coracobrachialis was 9.41±0.79cm~2.2. The distribution of intramuscular nerves: The anterior muscles of the upper arm were demonstrated by musculocutaneous nerve and before it going through coracobrachialis, it had subdivides one branch to demonstrate coracobrachialis. During musculocutaneous nerve going through coracobrachialis, it also had some small branches which demonstrated coracobrachialis and the small branches interweaved with each other at the middle of the muscle. The long head and short head of biceps brachii had one nerve branch divided from musculocutaneous nerve respectively and they had no communicating branch. Brachialis were demonstrated by 4 main branches divided from musculocutaneous nerve. The main branches subdivide more smaller branches which interweaved with each other at the middle of the muscle.3. The fixing of muscles' nerve entering points: The long head of biceps brachii had one nerve entering point and it's corresponding measurements were l4.02±2.23cm,4.66±1.48cm.The short head also had only one nerve entering point and it's corresponding measurements were 15.44±1.76cm,6.05±1.58cm. Brachialis had 2 to 4 nerve entering points and their corresponding measurements were 6.34cm～12.99cm,2.14cm～7.17cm. Coracobrachialis had one nerve entering point and it's corresponding measurements were 23.28±2.89cm, 5.98±1.66cm.4.The average muscle spindle density of the middle of muscle belly: the long head of biceps brachii was 22.57±6.17/cm~3, the short head was 21.22±5.61/cm~3, brachialis was 28.67±8.41个/cm~3, and coracobrachialis was 36.60±9.58个/cm~3.Conclusions: 1. Biceps brachii is designed for velocity and brachialis is tend to be designed for power.2. The distribution of intramuscular nerves of anterior muscles of the upper arm was regionality. Accoding that muscles could be divided into different subdivisions. There was no communicating branches at the middle part of Biceps brachii, but brachialis and coracobrachialis had many communicating branches at the middle. 3. The anterior muscles of the upper arm had 5～7 nerve entering points, all of these points were at the upward side of X-axis and at the interior of Y-axis. The corresponding measurements were 14～23cm (except for brachiali) and 2～8cm.4. The average muscle spindle density of the middle of coracobrachialis muscle belly was the highest among the three muscles. The average muscle spindle density of the middle of brachialis muscle belly was higher than biceps brachii, and that hinted brachialis was more sensitive than biceps brachii during the movement of elbow. Coracobrachialis and pectoralis major (the long head of biceps brachii ) may compose Parallel Combinations.