An insight on the anatomy of the pectoral and pelvic limbs

QUE: Compare and contrast the skeletal structure of pectoral and pelvic limbs

The difference between pectoral and pelvic limb is that pelvic limb is composed of two pelvic bones that attach in the back of the sacrum and these are joined in the front at the pubic symphysis, which is composed of cartilages whereas the pectoral limb is composed of scapulae and clavicles which joins the scapula and the sternum. Pelvic limb serves to connect the legs with the pelvis compared to the pectoral limb which supports the arms. Pelvic limbs consists of deep synovial ball and socket joints surrounded by bone structure. This gives a tradeoff for security, rigidity with less flexibility due to its weight bearing role of full body weight therefore does not need muscles to hold it in place however the pectoral limb consists of shallow synovial ball and socket joint which needs muscles to hold the head of the humorous in place.

The four rotator cuff muscles perform this duty including the teres minor, infraspinatous, supraspinatus and subscapularis. This tradeoff for a shallow ball and socket joint held in by muscles allows the highest range of motion of any joint in body but there is less security and ability to bear weight thus it is common to dislocate shoulder joints but very rare to dislocate your hip joint. Each hemi-pelvis is comprised of 3 bones which are fused to form the ossa coxae or pelvic bones. These two ossa coxae are firmly attached to another at the pelvic symphysis and are joined to the sacrum of the axial skeleton by two strong sacroiliac joints. The pectoral limb has a fore arm which consist of radius and ulna which fuse together. The radius is located in front of ulna and it supports the weight of the animal compared to the pelvis limb which has the ilium that is regularly triangular with the apex at the acetabulum. The pectoral limb consists of the carpus which is a region that has two rows of small bones and carpal bones in the proximal row. These are called the radial, intermediate, and ulna, whilst in the distal row they are numbered 1 to 4 from medial to lateral.

The pelvic limb however contains the femur which is also known as the thigh bone and it extends from hip joint to the stifle and the proximal. The end of femur is circle shaped and articulates with the acetabulum of the ossa coxae to form hip joint. The distal end contains 2 condyle for articulation with fibia. Pectoral limbs include muscles like the biceps brachii, brachialis, and brachioradialis whereas pelvic limb has iliopsoas muscles, quadrate lumbar muscles and deep gluteal muscles. The pectoral limb connects the upper arms to the axial skeleton and there is no anatomical joint between the scapula and the rib cage, but a connection made up of muscle and ligament. This allows for a greater range of mobility and flexibility compared to the pelvic girdle consists of the hip bones, the sacrum and the coccyx. The pelvis has four points of articulation, which cause it to have less mobility than the pectoral girdle. The pectoral limb is slight straighter and designed for carrying weight and absorbing impact force. The pelvic limb is more angular. It is designed for propulsion. Together with the sacrum and coccyx, the pelvic limb forms a bowl‐shaped region, which protects internal reproductive organs, the urinary bladder, and the lower part of the digestive tract.

The structure of the pelvic limb

The structure of pectoral limb.

There are also similarities between pelvic and pectoral limp which include the allowance of the body to move and change positions. The pelvic and pectoral limp also carry the weight of the animal as well as sturdy the sockets for limb articulation.