Physiological Functions

Skeleton is a frame of bones, a complex of living cells embedded in a material formed mainly form a compound calcium-phosphorus salt reinforced by protein fibres. Besides supporting the body weight, it provides rigid points for muscle attachment and for a movement of the body. The cranium of brain case encloses the cavity for the brain and extends backwards from just behind the eyes to the back of the skull. The cranium and the face in front of it are linked on either side by two cheek bones, the front or cranial end of which helps to form the socket ( orbit) for the eyeball, while the caudal end carries the joint surface for the mandible. 

The internal nasal cavity is divided into a right and left chamber by a flexible midline partition, the nasal septum, while the chambers themselves are packed with long paper-thin bones scrolls; the bone forming the floor of the chambers is also the hard plate of the mouth. The upper teeth are firmly fixed in body sockets at the junction of the hard palate and the face. The spinal column in all breeds of dog contain seven cervical ( neck) vertebrae, thirteen thoracic vertebrae, seven lumber vertebrae, the sacrum and a varying number of coccygeal ( tail) vertebrae, when all the vertebrae are aligned together, a wide central canal is formed inside the spinal column which extends from head to tail. Within this canal, runs the major nerve trunk of the body, the spinal cord. 

The region from carpus to digits is called the forepaw and contains several carpal bones, five metacarpal bones ( palm of the hand ) and five digits or fingers, the bones of which are known as phalanges. Digit one, the thumb, has two phalanges, digits two to five have three phalanges. The final phalanx on each digit carries the claw. The pelvic girdle protects the soft urinary and reproductive organs, while the pelvis itself carries the sockets for the heads of the left and right femurs or thigh bones. The patella ( knee cap) lies at the front of the lower end of the femur. Below the femur are the tibia and the fibula ( skin bones). Several tarsal bones comprise the tarsus or hock, corresponding to the ankle, above the metatarsal bones of the in step. 

The bones forming the joints are held firmly together by strong bands of white fibrous tissue known as ligaments, and each joint is enclosed in a cuff-like membrane, the joint capsule. The inner lining of this capsule produces a thick viscous fluid called synovia ( joint oil) which lubricates joint-movement. The major joints of fore and hind limb correspond with those in the human arm and leg, each foreleg being made up of the shoulder, elbow and carpal ( wrist) joints. The hind leg joints consist of the hip, stiffen ( knee) , the tar or hock ( ankle ) joints. The various joints between metacarpals, metatarsals and phalanges are equivalent to human finger and toe joints. 

Air passage ( the nose) lies dorsal to the food paste ( the mouth), but in the neck the air passage ( Larynax and trachea) lies ventral the food passage ( oesophgus or gullet) so that at the back of the throat, the region called the pharynx, the directions that food and air must take cross each other. Swallowing without food or fluid falling into the larynx is made possible by movements of the soft palate and the larynx. The soft palate is so long that its edge cannot normally be viewed; there is not vulva and mouth and nose cavities can communicate freely. The palate can be raised up to block off the rear exit from the nasal chambers during swallowing and lowered to close the back of the mouth cavity during nose-breathing. 

During quiet respiration, air is inhaled through the nostrils and is warmed and humidified in the nasal chambers. It then passes over the soft palats directly into the open larynx with the epiglottis raised on the upper side of the soft palate. At the start of swallowing, the epiglottis is pushed back over the laryngeal entrance, and the palate raises up, closing off the nasal passages and opening up the back of the mouth so that food or liquid can pass over the larynx into the opened oesophagus. Diving the thoracic cavity into right and left sides is a midline partition in which the heart and major blood vessels, and the oesophagus are found; each cavity is completely occupied by a lung, covered with pleura. 

The major function of the heart is to propel the blood round the body at sufficient velocity and pressure to ensure that all tissues constantly receive the substances they require for a efficient function, an on-going process called general circulation. The heart lies approximately between ribs three and six and a little to the left of the midline. In a slim-chested dog, like the Whippet, the heart beat can be seen as a regular movement or flutter of the chest wall where the apex of the heart touches the inside of the chest wall. The right atrium and ventricle pump blood through the pulmonary circulation, picking up oxygen on the lungs; the oxygen-rich blood is then conveyed back to the left atrium and ventricle from which it is propelled into the aorta and distributed throughout the body by a network of arteries. 

The movement of the arterial wall can be felt as the pulse. In the dog , this is best felt about half-way down on the inner surface of the thing in the midline. Arteries branch and rebranch, becoming smaller until they form a huge network of microscopic vessels or capillaries. These allow nutrients to pass through their walls to tissues, then join and region to become thin-walled vessels of increasing size, the veins, which covey blood towards the heart; they are wider and with thinner walls than the arteries. 

The dog has forty-two teeth, twenty in the upper jaw and twenty two in the lower. The right and left upper jaw each has three incisors, one canine tooth four premolars and two molars; the right and left lower jaws possess the same number of incisors, canines and premolars, but have three molars. The incisor teeth act as nippers; the canine can hold firmly on two prey because of two powerful muscles which act to close the jaws. The roots of the canine teeth are extremely long which increase their strength. Food is reduced to small lumps by the action of the tongue and teeth and lubricated by saliva produced from four pairs of salivary glands. 

The digestive juices in the stomach and small intestine contain enzymes which break food down into simple chemicals, soluble in water; the main food breakdown takes place in the small intestine, consisting of duodenum, jejunum and ileum. The large pancreas also produces digestive juices. Bile, which is involved with fat digestion is emptied from the liver into the duodenum. The liver is an important gland and processes most of the products of digestion, transforming them into chemicals used for body building and repairs. The pancreas, for example, produces the hormone insulin and also manufactures digestive juices. Two adrenal glands cranial to the kidneys produce corticosteriod and an adrenaline compound. The sex hormones from the ovaries control the female reproductive cycle in conjunction with the pituitary hormones. They are also responsible for the production of the secondary sexual characteristics in the young bitch. Male hormone produced in the testicle is responsible for the secondary sexual characteristics of the male.