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Lab.17 Rabbit practical biology * External features for rabbit: 1- Note that there is an almost complete covering of hairs on the outer surface of the body. 2- Divisions of the body are the head, neck, trunk, with two pairs of limbs, and tail. 3- In the head, note the anterior mouth bounded by two mobile lips (characteristic of mammals); the upper lips is divided by a median cleft which connects the mouth with the external nostrils which are lie on the tip of a mobile nose (characteristic of mammals). Two large eyes, each guarded by two eyelids, an upper and a lower fringed by eyelashes, and a third or nictitating membranes attached to the anterior angle of the eye. On the anterior of facial region of the head are a few tactile hairs, the vibrissae, which are greatly enlarged. The pinnae are parts of the external ears, and are freely movable (mammalian feature). 4- On the two sides of the urinogenital aperture in both sexes are two hairs less inguinal depressions on to which open the ducts of perineal glands (scent glands). They secrete a substance which gives the rabbit it is characteristic odour by means of which it can distinguish it is own kind by smell. 5- A long the ventral surface of the thorax and abdomen are 4-5 pairs of teats on the tips of which open the ducts of mammary glands in the female. 6- The limbs are built up on the same plan as in the other tetrapods, the hand has 5, and the foot only 4 digits which terminate in strong curved claws. Note that the hind limbs are longer than the fore-limbs (adaptation of leaping). * Digestive system: 1- Mouth cavity: is containing on teeth and internal nares which lies above a beyond the soft palate. The tongue is an elongated movable muscular mass, free in front and attached behind to the floor of the mouth by the frenulum linguae. 2- The esophagus, which extend in the neck region dorsal to the trachea and passes backwards into thoracic cavity and pierces the diaphragm and open into the stomach. 3- The stomach (a large sac) is consisting of wider portion, cardiac region and pyloric portion. 4- The small intestine follows from the pyloric portion of the stomach. The duodenum (U-shape), then jejunum, and ileum. 5- The large intestine consists of caecum, colon, and rectum. The cecum ends by vermiform appendix. The rectum is end by anus. 6- The pancreas is lie between the two limbs of the duodenal loop. 7- The liver is very large, dark red in color. It is consist of 5 lobes. The right and left central, the left lateral, the caudate, and the small spigelian lobes. The right central lobe is grooved for the reception of the gall-bladder. 1 * The respiratory system: consists of: 1- External nostrils which are lie on the tip of a mobile nose, and nasal passages. 2- The larynx: box-like structure, and opening into the pharynx by the glottis and epiglottis. 3- The trachea: This is recognized by its cartilaginous incomplete rings. 4- Two bronchi each passes into a lung. Note that the right lung is formed of 4, the left of 2 lobes. 5- The muscular diaphragm which plays an important role in breathing. * Skeletal system: 1- The skull 2- The vertebral column: is divided into (cervical, thoracic, lumber, sacral, and caudal vertebrae. 3- The ribs and sternum. 4- The pectoral consists of scapula (triangular plate), clavicle and coracoid bones. 5- The for-limb is consist of humerus, radius & ulna, carpus (9 pieces), metacarpus (5 metacarpalia) 6- The pelvic girdle is consisting of antero-dorsal large ilium, postero-dorsal ischium, and ventral small pubis. 7- The hind-limb is consisting of femur, tibia & fibula, tarsus (6 pieces), metatarsus (4 metatarsalia). 2