Each toe is made up of a proximal phalange, a middle phalange, and distal phalange (and some small bones often referred to as sesamoids. In the horse and other equines, the third toe is the only toe remaining on the front and real limbs. They have become wings for flying in birds and bats, flippers for swimming in whales, seals and porpoises, fast and efficient limbs for running in horses and arms and hands for holding and manipulating in primates (see diagram 6.8). The top of the humerus moves against (articulates with) the scapula at the shoulder joint.īy changing the number, size and shape of the various bones, fore limbs have evolved to fit different The forelimb consists of: Humerus, radius and ulna, carpals, metacarpals, digits or phalanges Birds have a large expanded sternum called the keel to which the flight muscles (the ‘breast” meat of a roast chicken) are attached. They are called floating ribs (see diagram 6.5). In dogs one pair of ribs is not attached ventrally at all. Each rib is attached ventrally either to the sternum or to the rib in front by cartilage to form the rib cage that protects the heart and lungs. Paired ribs are attached to each thoracic vertebra against which they move in breathing. On either side of this are two small, smooth rounded knobs or condyles that articulate (move against) the first or Atlas vertebra. At the base of the cranium is the foramen magnum, translated as “big hole”, through which the spinal cord passes. These are air spaces in the bones of the skull which help keep the skull as light as possible. Behind the nasal cavity and connecting with it are the sinuses. At the front of the skull is the nasal cavity, separated from the mouth by a plate of bone called the palate. It forms a joint with the skull moved by strong muscles that allow an animal to chew. The teeth are inserted into the upper and lower jaws (see Chapter 5 for more on teeth) The lower jaw is known as the mandible. The bony wall of the cranium encloses the middle and inner ears, protects the organs of smell in the nasal cavity and the eyes in sockets known as orbits. The “box “enclosing and protecting the brain is called the cranium (see diagram 6.4). The skull of mammals consists of 30 separate bones that grow together during development to form a solid case protecting the brain and sense organs. Finally there are a variable number of small bones in the tail called the coccygeal vertebrae (see diagram 6.3).ĭiagram 6.3 - The regions of the vertebral column dik The sacral vertebrae are usually fused into one solid bone called the sacrum that sits within the pelvic girdle. Lumbar vertebrae in the loin region are usually large strong vertebrae with prominent spines for the attachment of the large muscles of the lower back. Grazing animals like cows and giraffes that have to support weighty heads on long necks have extra large spines on their cervical and thoracic vertebrae for muscles to attach to.
Thoracic vertebrae in the chest region have special surfaces against which the ribs move during breathing. In the neck there are cervical vertebrae with the two top ones, the atlas and axis, being specialized to support the head and allow it to nod “Yes” and shake “No”. The shape and size of the vertebrae of mammals vary from the neck to the tail. The spinal cord passes through the hole in the middle and muscles attach to the spines making movement of the body possible (see diagram 6.2).ĭiagram 6.2 - Cross section of a lumbar vertebrae Each vertebra consists of a ring of bone with spines (spinous process) protruding dorsally from it.
#Skull and bones drawing series#
The vertebral column consists of a series of bones called vertebrae linked together to form a flexible column with the skull at one end and the tail at the other. It is joined to the spine by means of a flat, broad bone called a girdle and consists of one long upper bone, two long lower bones, several smaller bones in the wrist or ankle and five digits (see diagrams 6.1 18,19 and 20). Each of the four limbs is made to the same basic pattern. The rest of the skeleton of all these animals (except the fish) also has the same basic design with a skull that houses and protects the brain and sense organs and ribs that protect the heart and lungs and, in mammals, make breathing possible. the main bones of the fore and hind limbs, and their girdles and be able to identify them in a live cat, dog, or rabbitįish, frogs, reptiles, birds and mammals are called vertebrates, a name that comes from the bony column of vertebrae (the spine) that supports the body and head.
the difference between ‘true ribs’ and ‘floating ribs.the basic structure of a vertebrae and the regions of the vertebral column.After completing this section, you should know:
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