Back to: Animal Husbandry SS 2
The Pelvic Girdle
The pelvic girdle is found around the waist in mammals. It consists of two halves which are joined to each other ventrally and to the sacrum dorsally. The line of fusion of the two halves is called pubis symphysis. Each half is called innominate bone. Each half is made up of three bones which are (i) ilium (ii) ischium and (iii) pubis. They are fused together. At the top is the ilium which is the largest and the longest of the three bones. At the lower end are the fused bones-ischium and pubis. The ischium and pubis enclose an opening or a hole called obturator foramen. It is through this hole that nerves, blood vessels and muscles pass. On the other surface of each half of the girdle where the three bones meet, there is a deep hollow or depression called acetabulum where the head of the femur of the hind limb fits to form the hip joint, an example of ball and socket joint.
The Limbs
The limbs are made up of the fore limbs (bones of the hands) and the hind limbs (bones of the legs). The limbs of most vertebrates are built on the same basic plan, i.e., pentadactyl limb plan (5-digit plan). It is made up of a long bone followed by a pair of two long bones which lie side by side.
The pair of these long bones is followed by a set of nine small bones which are arranged in three rows. The nine small bones are followed by five digits. Each digit is made up of small bones called phalanges. The diagram shows a generalised fore and hind pentadactyl limbs including the names of the corresponding parts.
The Fore Limb
The fore limb of mammal (Fig. 2.34), e.g. rabbit is made up of an upper arm bone which is a long bone called humerus (Fig 2.34). It has a rounded head which fits and articulates with the glenoid cavity of the scapula of the pectoral girdle of the shoulder joint.
The lower ends of the humerus end in a grooved-pulley-like surface called trochlea. At the trochlea, the humerus articulates with radius and ulna to form the elbow joint.
The humerus is followed by the bones of the fore-arm. The fore arm bones are the radius and ulna. The radius is a long bone. It lies in front of the ulna and is slightly curved. The ulna is longer than the radius. It has a cavity called sigmoid cavity. The trochlea of the humerus fits into this cavity. The ulna also projects backwards to form a projection called olecranon process.
The radius/ulna bone is followed by bones of the wrists which are made of nine small bones arranged in three rows. These bones are called carpals. Proximally (in front), the carpals articulate with radius-ulna and dixtally with the bones of the digits. The wrist bones are followed by bones of the digits. The digit bones are five and they are called metacarpals. In man, the metacarpals are called fingers, they are referred to as phalanges. In man, each digit has three phalanges with the exception of the thumb which has two phalanges. In rabbit, the phalanges end in claws.
The Hind Limb
The hind limb of mammal (Fig. 2.36) e.g. rabbit is made up of the thigh bone called the femur (Fig 2.37). The femur is the largest and the strongest bone in the body. It is rounded at the proximal end to form a head which fits into the acetabulum of the pelvic girdle to form a hip joint. Very close to the head of the femur are three projections called trochanters. They are important for the attachment of muscles. At the distal end of the femur are two rounded nob called condyles. They articulate with tibia bon In-between the two condyles is a pulley-lik hoof. The shank is made up of two bones calle tibia and fibula but are fused in rabbit to form
The Ribs
The ribs are long semi-circular rods connecting the thoracic vertebrae to the breastbone (sternum) (Fig. 2.38a). It is found in the chest region of mammals. There are of thirteen pairs of ribs in rabbit. The bony cage formed by ribs protects the lungs and heart. It also assists in breathing.
A typical rib consists of a head (which fits between successive thoracic vertebrae), a neck and the main part, the shaft (Fig. 2.38b).
Each rib articulates with the thoracic vertebrae by two processes: the capitulum which articulates with facets of the centre of two nearby vertebrae and the tuberculum (tubercle) which articulates with a transverse process.
The first seven pairs of ribs are called the true ribs because they are connected directly with
The sternum in front (ventrally) by costal cartilages. The next five pairs of ribs are called false ribs because the eighth, ninth and tenth pair of ribs have a common connection with the sternum, each being attached to the costal cartilage of the rib above. The eleventh and twelfth and thirteeth pair are called floating ribs because they have no connection whatsoever with the sternum.
Functions of the Skeletal System The skeletal system of farm animals perform the following functions:
It gives supports and rigidity to the body.
It protects some vital organs of the body e.g the skull protects the brain, the vertebral column protects the spinal cord, the eye is protected by the sockets.
The skeletal system is used for movement i.e locomotion of animals from one place to another.
The bone marrow helps in the formation of red blood cells which helps to transport oxygen.
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