Table 3b.

Origin, insertion and function of the intrinsic foot muscles of Pan paniscus

Muscles	Origin	Insertion	Form	Function
(a) Hallucal muscles
AbdH	medial side of the tuber calcanei, tuberosity of the naviculare, and plantar aponeurosis	strong, broad tendon to medial sesamoid bone and base of proximal phalanx of the hallux	thick, pennate; fused with FHBm	hallucal abduction and flexion
AddHo	plantar side of the metatarsal III base	lateral sesamoid bone of the first metatarsal	pennate; short tendon at insertion	hallucal adduction and flexion
AddHt	plantar side of the metatarsal II, III and IV heads		massive, parallel head
(b) Short flexors
FHBm	plantar side of the medial cuneiform bone	tendon to the medial sesamoid bone of the first metatarsal	thick, pennate, superficial head; fused with AbdH tendon	slight flexion of the first metatarsal
FHBl		lateral sesamoid bone of the first metatarsal	elongated, pennate, deep head; tendon at origin
FDB I	medio-plantar side of the tuber calcanei	perforated tendons to the plantar side of the middle phalanges of digits II (and III)	superficial head; unipennate (proximally fused bellies); variable distribution	flexion of digit(s) II (and III)
FDB II	from the latero-plantar side of the FT tendon	perforated tendons to the plantar side of the middle phalanges of digits (III and) IV	deep head; slender, unipennate; variable distribution	flexion of digit(s) (III and) IV; foot plantar flexion
(c) Short extensors
EHB	dorso-lateral side calcaneus; trochlea peronealis, near the sinus tarsi	tendon into the dorsal aponeuroses of digit I	bipennate; proximally fused with EDB	hallucal extension and foot supination
EDB		2–3 tendons into the dorsal aponeuroses of digits II (III) and IV	2–3 bipennate muscle bellies; proximally fused with FDB	digital extension (digits II–IV)
(d) Other
Lumbr II	medial side of the FT tendon to digit II	tendons to the dorsal side of the proximal phalanges of digit II, III, IV and V	small, unipennate	assists in flexion of digital (proximal) phalanges
Lumbr III and IV	medial side of the FF tendons to digit III and IV
Lumbr V	lateral side of the FF tendon to digit IV
AbdV	plantar side of the tuber calcanei; ligament between the tuberosity of metatarsal V and the lateral malleolus	2 tendons to the plantar base of the proximal phalanx of digit V	thick, bipennate; distally fused with FlexV	flexion and abduction of digit V
FlexV	along metatarsal V and from the AbdV belly	separate insertion onto the AbdV tendon and to the metatarso-phalangeal joint	pennate; 2 separate muscle bellies; fused with AbdV	slight flexion of digit V