Knowledgebase
Joints #893340
Asked February 28, 2025, 1:33 PM EST
Dallas County Texas
Expert Response
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Shoulder - between humerus and shoulder blade
Elbow - between humerus and Radius/Ulna
Wrist - between Ulna/Radius and phalanges
Hip - between femur and back
Knee - between Femur and tibiotarsus
Ankle - between tibiotarsus and tarsometatarsus - also referred to as the hock
Pectoralis minor, also called deep pectoralis, supracoracoideus or subclavius, is a small and elongated muscle which elevates the wing during flight. It lies deep to the pectoralis major. It arises from the anterior part of the sternum, dorsal to the pectoralis major. Its tendon passes through the foramen triosseum, an aperture occurring in between the junction of the clavicle, scapula and coracoid; and is inserted on the dorsal side of the head of humerus.
Pectoralis minor is an elevator muscle and it causes the upstroke of the wing. When it contracts, the foramen triosseum acts like a pulley for its tendon, pulling the humerus backwards and upwards, and, thus, raising the wing during flight. In pigeon, the pectoralis minor is especially developed and causes quick takeoff of the bird during flight.
The important flexor muscles are following:
(i) Ambiens:
In some birds, an ambiens muscle arises from the ilium and passes along the inner surface of thigh. Its long tendon runs beneath the patella bone round to the outer side of the knee enclosed in a special sheath and passes to the outer side of the tibiotarsus to join the upper end of the flexor muscle of the second and third toes. This muscle has little role in perching.
(ii) Peroneus Medius:
This muscle occurs singularly on the anterior aspect of the shank, attached to the upper part of the tibiotarsus bone. Its tendon divides into three tendons, going to the three front digits.
(iii) Gastrocnemius:
It is a calf muscle mainly concerned with producing flexion of the toes in the act of perching and occurs on the back of tibiotarsus. Its tendon passes behind the ankle and trifurcate to supply the three anterior toes along with peroneus medius muscles. These tendons often act as a single unit.
(iv) Flexor Perforans:
This muscle is attached to the upper part of the tibiotarsus (above the knee). Its tendon going to the hallux and is joined by a slip with the peroneus medius. Thus, a pull up on one tendon flexes all the toes.
When a bird sits on its perch the legs are bent at the knee and the ankle, thus, the tendons are flexed and the digits are automatically closed around the perch. A pull on any tendon will close all four digits. Flexing of digits is due to a grip reflex which is inflated by a sensory receptor on the lower surface of the foot, the moment the foot touches the perch. When a bird sleeps with body relaxed, the weight of the body bends the ankles more and the tendons become tighter ensuring a firmer grip of the perch, so that a sleeping bird cannot fall. This is automatic perching mechanism.
A second perching mechanism is a locking device that holds the toes flexed. The lower surface of flexor tendon is ridged at the metatarso-phalangeal joint, where the weight of the body presses it against a branch. The upper surface of the tendon sheath is also ribbed and as the bird settles on its perch, the two sets of ridges are interlocked.
2. Extensor Muscles:
The toes are unlocked by raising of body and also by extensor muscles. In pigeon, several extensor muscles are found at the front of the tibio-tarsus. The tendon of the tibialis anterior muscle passes down in front of the intertarsal joint and then divides into three branches, to supply one branch to each anterior toe. These tendons of flexor muscles are attached to the upper surfaces of the phalanges. The contraction of tendons of extensor muscles serves to open the toes, when the bird raises its shank while taking off the perch.
3. Dermal Muscles:
The dermis of pigeon has some muscles which derive from parietal muscles and move individual feathers.
