Development<unk>  and syndrome may result from phylogenetic differences between human and non-human primates. Phylogenetically, the flexor pollicis longus and the flexor digitorum profundus both originate from a common mesodermal mass. In non-human primates, there is only one flexor muscle for all the fingers, whereas in humans, the flexor pollicis longus becomes distinct.<unk><unk><unk>  syndrome may be viewed as an evolutionary persistent structure. It is still inconclusive whether or not the connection is congenital or acquired at a later time point in life. Anatomy Multiple types of the connection between the flexor pollicis longus and the flexor digitorum profundus were described: * A tendinous connection between the flexor digitorum profundus of the index to the flexor pollicis longus * A muscle with a bifurcated (split into two) tendon for the thumb and index finger * A common muscle with five tendons for the thumb and the long fingers
Linburg–Comstock variation
Spaghetti plot
Patlak plot
Preston curve
Lewis offset
Isotropic bands
J wave
Wells curve