Muscular System - Extrinsic Muscles Overview

A large, superficial muscle that extends from the neck and thorax to the scapula and humerus. It helps to elevate and retract the forelimb, as well as rotate it.

A deep muscle that extends from the neck and thorax to the scapula. It helps to retract and stabilize the forelimb.

A large, broad muscle that extends from the dorsal region to the humerus. It helps to extend, adduct, and rotate the forelimb.

A deep muscle that extends from the transverse process of the atlas (first cervical vertebra) to the scapula. It helps to rotate the scapula.

A large, deep muscle that extends from the cervical and thoracic vertebrae to the ribs. It helps to protract and stabilize the forelimb, and also helps with breathing.

Superficial muscles that extend from the sternum and ribs to the humerus. They help to adduct and retract the forelimb.

A deep muscle that extends from the sternum to the humerus. It helps to adduct and retract the forelimb.

A large, superficial muscle that extends from the neck and thorax to the humerus. It helps to extend, retract, and rotate the forelimb.

A muscle that flexes the elbow joint, located on the front of the arm.

A large, three-headed muscle on the back of the upper arm responsible for extending the elbow joint.

A slender muscle that acts as a weak extensor of the elbow joint, located on the posterior side of the elbow.

This muscle is responsible for rotating the forearm outward (supination).

A large muscle that primarily helps flex the elbow, located on the front of the arm.

A muscle on the medial side of the elbow that is responsible for rotating the forearm inward (pronation).

This muscle is responsible for flexing the wrist, located on the radial side of the forearm.

A muscle that helps to extend the wrist, located on the ulnar side of the forearm.

The main group of muscles responsible for extending the stifle joint in the hindlimb.

A powerful muscle on the front of the thigh that helps to extend the stifle joint and also flexes the hip joint.

A large muscle on the outer side of the thigh that helps to extend the stifle joint.

A muscle located deep under the rectus femoris that helps to extend the stifle joint.

A muscle on the inner side of the thigh that helps to extend the stifle joint.

A group of muscles that help in flexing the stifle joint and also participate in extending the hip joint (especially in some species).

A large tendon that connects various muscles to the calcaneus (heel bone), allowing movement of the hock joint.

Muscles responsible for extending the digits.

A long, thin, and powerful muscle that extends the digits of the horse's front leg. It is located on the lateral side of the forearm and serves as a critical component of the horse's ability to extend its digits for weight-bearing and movement. It also works in synergy with other muscles to provide power and stability for the horse's gait.

A group of muscles that are responsible for flexing the hoof of the horse. These muscles are located in the back of the horse's leg, and they work together to bend the hoof at the fetlock joint. They are crucial for propelling the horse forward.

A muscle located on the back of the horse's leg that acts as the primary flexor of the hock. This muscle is responsible for bending the hock joint, which is essential for the horse's ability to extend its hindlimb for locomotion.

A large, powerful muscle located on the back of the horse's leg that functions as the primary extensor of the hock. This muscle plays a crucial role in the horse's ability to extend its hindlimb and propel itself forward. It also plays a role in supporting the weight of the body.

The thigh region in the hindlimb of the horse.

The knee region in the hindlimb of the horse.

The ankle/hock region of the horse's hindlimb.

These are the muscles in the horse's foot that aid in digit movement. This is important for bearing weight, stability, and propelling the horse forward.

The stay apparatus is a unique feature found in horses, which helps them to sleep standing up. The muscles and tendons within the stay apparatus work together to lock the hindlimb joints in extension, providing stability and preventing the horse from collapsing.

Birds have a sparse dorsal musculature due to the fused axial skeleton, requiring minimal muscle support. The muscles of the limbs and wings are also reduced, with lightweight tendons. The main muscle bulk is concentrated in the pectoral muscles, representing up to one third of the body mass.

The pectoral muscles provide the powerful downstroke of the wings, while the supracoracoid muscles elevate the wings for the upstroke, generating lift. Their strategic placement near the center of gravity provides stability during flight.

The supracoracoid muscle's tendon runs through the triosseal canal to insert on the dorsal tubercle of the humerus. This pathway allows a muscle positioned below the wing to elevate the wing, thus minimizing weight shift and maintaining flight stability.

The pectoralis muscles extend from the sternum to the humerus, providing the main force for the downstroke. The supracoracoid muscles, positioned beneath the pectoralis, also attach to the sternum and, through the triosseal canal, insert on the humerus, enabling the upward wing movement.