Musculature Human vestigiality

1 musculature

1.1 head
1.2 face
1.3 arm
1.4 torso
1.5 leg
1.6 tongue

musculature

a number of muscles in human body thought vestigial, either virtue of being reduced in size compared homologous muscles in other species, having become principally tendonous, or being highly variable in frequency within or between populations.

head

the occipitalis minor muscle in of head joins auricular muscles of ear. muscle sporadic in frequency—always present in malays, in 56% of africans, 50% of japanese, 36% of europeans, , nonexistent in khoikhoi people of southwestern africa , in melanesians. other small muscles in head associated occipital region , post-auricular muscle complex variable in frequency.

the platysma, quadrangular (four sides) muscle in sheet-like configuration, vestigial remnant of panniculous carnosus of animals. in horses, muscle allows flick fly off back.

face

in many non-human mammals, upper lip , sinus area associated whiskers or vibrissae serve sensory function. in humans, these whiskers not exist there still sporadic cases elements of associated vibrissal capsular muscles or sinus hair muscles can found. based on histological studies of upper lips of 20 cadavers, tamatsu et al. found structures resembling such muscles present in 35% (7/20) of specimens.

arm

the palmaris longus muscle seen small tendon between flexor carpi radialis , flexor carpi ulnaris, although not present. muscle absent in 14% of population, varies ethnicity. believed muscle actively participated in arboreal locomotion of primates, has no function, because not provide more grip strength. 1 study has shown prevalence of palmaris longus agenesis in 500 indian patients 17.2% (8% bilateral , 9.2% unilateral). palmaris popular source of tendon material grafts , has prompted studies have shown absence of palmaris not have appreciable effect on grip strength.

the levator claviculae muscle in posterior triangle of neck supernumerary muscle present in 2–3% of people present in mammalian species, including gibbons , orangutans.

torso

the pyramidalis muscle of abdomen small , triangular muscle, anterior rectus abdominis, , contained in rectus sheath. absent in 20% of humans , when absent, lower end of rectus becomes proportionately increased in size. anatomical studies suggest forces generated pyramidalis muscles relatively small.

the latissimus dorsi muscle of has several sporadic variations. 1 particular variant existence of dorsoepitrochlearis or latissimocondyloideus muscle muscle passing tendon of latissimus dorsi long head of triceps brachii. notable due developed character in other apes , monkeys, important climbing muscle, namely dorsoepitrochlearis brachii. muscle found in ≈5% of humans.

leg

the plantaris muscle composed of thin muscle belly , long thin tendon. muscle belly approximately 5–10 centimetres (2–4 inches) long, , absent in 7–10% of human population. has weak functionality in moving knee , ankle considered redundant , used source of tendon grafts. long, thin tendon of plantaris humorously called freshman s nerve , mistaken nerve first-year medical students.

tongue

another intriguing example of human vestigiality occurs in tongue, chondroglossus muscle. in morphological study of 100 japanese cadavers, found 86% of fibers identified solid , bundled in appropriate way facilitate speech , mastication. other 14% of fibers short, thin , sparse – useless, , of vestigial origin.