Research On Human Triceps Brachii About The Muscle Architecture, The Distribution Of Intramuscular Nerves, Muscle Spindles And The Nerve-entering Points

Objective: To provide a detailed morphologic data for further studying the physiological function and clinical application of triceps brachii by researching into those muscles' architecture, the distribution of intramuscular nerves, nerve-entering points and muscle spindles.Methods : 1 .To obtain bilateral triceps brachii completely from 11 adult cadavers which have been fixed by formalin . First to observe the shape, enthesis and arrangement form of muscle bundles of triceps brachii. And then to study the muscle architecture of the muscles.2. To obtain bilateral triceps brachii completely from 3 child cadavers and 2 adult cadavers which had been fixed by formalin. To deal with those muscles with modified Sihler's staining technique and then observe the distribution of triceps brachii's intramuscular nerve branches.3.To draw the materials of triceps brachii'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 triceps brachii4.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 perpendicular which passes greater tubercle.Results: 1. Gross-anatomy: Triceps brachii was a kind of bipennate muscle which was composed of short fascicle and intramuscular tendon plate. Intramuscular tendon plate was seen on the longitudinal section and transverse section, located caput laterale musculi tricipitis brachii superficial surface arid caput longum musculi tricipitis brachii profound surface. Besides caput mediale musculi tricipitis brachii had 2 intramuscular tendon plate .Superficial view: triceps brachii was divided medial head,long head and lateral head from wall to lateral. Profound View: medial head was at profound of long head, especially inferior extremity. Triceps muscle bundle was arranged into layers.2. The architectural feature of Triceps brachii: The muscle weight of the long head,medial head,lateral head of triceps brachii muscle were (163.30±35.19) g, (109.05±27.27) g, (104.83±20.67) g; their fiber lengths were (7.40±1.17) cm, (5.76±0.52) cm, (5.89±0.83) cm; their Cross Sectional Areas were (19.53±1.45) cm~2, (19.45+4.31) cm~2, (16.92 + 2.12) cm~2. 3. The distribution of intramuscular nerves: The triceps brachii muscle was demonstrated by radial nerve which subdivided three main branches when it enter into muscle. The long head was demonstrated by long head branche which subdivided two smaller branches . The lateral branch was the biggest one. The medial head was demonstrated by medial head branche which subdivided two smaller branches .The inferior branch is the biggest one .The lateral head was demonstrated by lateral head branche which subdivided two smaller branches which were superficial and profundus branch. Three main branches subdivided more smaller branches which interweaved with each other on middle of the triceps brachii .The medial head branche subdivided more smaller branches which interweaved with each other on the inferior extremity of the medial head 4.The average muscle spindle density of the middle of muscle belly: the long head of triceps brachii was 17.14±2.53/cm~3, the medial head was21.41±2.87/cm~3, the lateral head was 17.41±2.71/cm~35 The fixing of muscles' nerve entering points: The long head of triceps brachii had one nerve entering point and it's corresponding measurements were 19. 68±2. 12cm, 6. 65±0. 84cm; The medial head also had only one nerve entering point and it's corresponding measurements were 15. 81±3. 40cm, 5. 67±1. 32cm; The lateral head also had only one nerve entering point and it's corresponding measurements were 18.27±2. 90cm, 4. 8±1.39cm.Conclusions: 1. The long and lateral head of triceps brachii which had a lamellar tendon board respectively are short bipennate muscle. The medial head which had 2 intramuscular tendon board was also a kind of bipennate muscle.2. The long head of the triceps brachii was for greater displacement and velocity while the medial and lateral head were designed mainly for greater tension production.3.The intramuscular nerve branches mainly distributed in the profound part or two sides of intramuscular tendon board .Three main never branches subdivided more smaller branches which interweaved with each other on middle of the triceps brachii 4. The average muscle spindle density of the medial head was the highest among the three muscles, and that hinted the medial head was more sensitive than the long and lateral head during the movement of elbow. 5. The triceps brachii had 3 nerve entering points, all of these points localize in a scope which was 4-6cm interior of Y-axis and 15-19cm above X-axis.