Q: Describe the structure of heart of rabbit.
Draw a neat labelled diagram of L. S. of heart of rabbit.
A: Heart of rabbit lies in the region in thorax between the two lungs. It is a muscular and pulsating organ that keeps the blood in constant circulation. Heart is enclosed by a double layered pericardium. The two layers of pericardium are separated by pericardial cavity, which contains pericardial fluid. This fluid reduces friction and allows free movement of heart. Heart of rabbit is four chambered with two artria and two venticles.
External structure: Heart is a pear shaped structure, that is, broad anteriorly and the pointed apex is directed posteriorly. Atria lie anteriorly and ventricles lie posteriorly. Atria and ventricles are separated by a groove called coronary sulcus. The posterior parts of atria extend over the ventricles as auricular appendix. The two ventricles are separated externally by an oblique inter ventricular groove.
Internal structure:
1. Atria: 1. There are two artia (left and right) that form the anterior part of heart. They are separated from each other by an inter atrial septum. Walls of atria are thin.
2. Inter atrial septum has a small pore in embryonic state, known as foramen ovalis. After birth, when lungs become functional, it is closed leaving an oval mark called fossa ovalis.
3. Right atrium is larger than left one. It receives deoxygenated
blood from all parts (except lungs) through three major veins, namely, two precaval veins and a post caval vein. Near the opening of post caval vein is a vestigial valve of Eustachian.
4. Blood from muscles of heart is collected by coronary sinus. It opens into left precaval vein just before it opens into right atrium. The opening of coronary sinus into precaval vein is guarded by valve of Thebesius.
5. Left atrium receives oxygenated blood from lungs by a pair of pulmonary veins, which opens into the left atrium through a common pore.
6. Atria and ventricles are separated by an atrio ventricular septum.
7. Near the Eustachian valve, in the wall of right atrium, the pacemaker, namely, sinoatrial node is present.
2. Ventricles: 1. There are two ventricles (left and right) that form the posterior part of heart. They are separated from each other by an inter venticular septum. The walls of ventricles are thick and highly muscular.
2. Left ventricle is larger than right ventricle.
3. Right atrium opens into the right ventricle through a right atrio ventricular aperture. It is guarded by a tricuspid valve. It allows the blood to flow from right atrium to right ventricle only.
4. Left atrium, opens into left ventricle through a left atrio ventricular aperture. It is guarded by a bicuspid valve or mitral
valve. It allows the blood to flow from left atrium to left ventricle only.
5. The inner surface of ventricles is raised into muscular ridges called columnae cornae. Some of them are conical and are called papillary muscles.
6. Extending between atrio ventricular valves (that is tricuspid valve, bicuspid valve) and papillary muscles, there are tendon like cords, known as chordae tendinae. They prevent the too much bulging of atrio ventricular valves into atria.
7. In the posterior right boarder of inter atrial septum, an atrio ventricular node is present. It gives off bundle of His into inter ventricular septum.
3. Aortic arches
a. Pulmonary arch: 1. It arises from right ventricle. It supplies deoxygenated blood to lungs.
2. The opening of pulmonary arch into right ventricle is guarded by a Pulmonary valve, formed by three semi lunar cusps. (semi lunar valve) Pulmonary valve allows the blood to flow into pulmonary arch only from right ventricle.
3. Pulmonary arch and systemic arch are connected by a strand called ligamentum arteriosum (remnant of ductes Botalli).
b. Systemic arch (left only)
1. It arises from left ventricle. It supplies oxygenated blood to all parts of body
2. The opening of systemic arch into left ventricle is guarded by an aortic valve, formed by three semi lunar cusps. Aortic valve allows
the blood to flow into systemic arch only from left ventricle.
Very Short Answer Questions
Q: What is meant by diastema?
A: Due to absence of canines in rabbit, in each half of the jaws a large gap is formed between incisors and premolars. This gap is
called diastema.
Q: Which vitamin is called sun shine vitamin? What is the disease caused by the deficiency it among children?
A: i. Vitamin D is called sun shine vitamin.
ii. Due to deficiency of Vitamin D in children, Rickets is caused.
Q: Name the muscles that help in breathing movements in rabbit.
A: Muscles of diaphragm and Intercostal muscles.
Q: What is meant by chloride shift?
A: When bicarbonate ions increase in the red blood cells, they diffuse into the plasma. To maintain ionic balance in blood, for every bicarbonate ion that comes into plasma, one chloride ion diffuses into the red blood cell. This phenomenon is known as chloride shift or Hamberger’s phenomenon.