Wednesday, August 27, 2014

Ventral and dorsal side of the frog's Heart

The heart of frog is a muscular and conical organ located in the body cavity between the oesophagus and sternum. it is enclosed in a membrane called pericardium. it contracts and expands continuosly thrughout the life. This contraction and expansion of heart is called heartbeat due to which blood keeps circulation in the body. The heart of frog consists of three chambers:
1. Right Auricle or Atrium
2. Left Auricle or Atrium
3. Ventricle
The two thin walled atria from the broader anterior part of the heart. Right atrium is larger than the left atrium. Ventricle forms the conical , thick, uneven walled, posterior part of the heart.
A broad vessel, truncus arteriosus originates from the ventral side of ventricle and triangular sac called sinus venosus opens into the right atrium. Each brand divides into three arches (arteries). A thin walled triangular sac called sinus venosus opens into the right atrium. Both the truncus arteriosus and sinus venosus are not true chambers of the heart but often called accessory chambers. However, some biologists consider them as chambers of heart which beat in a rhythmic manner. First of all sunus venosus contracts then the two atria followed by the contraction of the ventricle and in the end truncus arteriosus contracts. Deoxygenated blood from the whole body except lungs is carried to the sinus venous by two precavals and one postcaval . Sinus venosus opens through an aperture into the right atrium. Oxygenated blood from lungs is carried to the left atrium by two pulmonary veins. Both the atria open jointly by and aperture guarded bya valve into the ventricle. 
The two atria, the right one with deoxygenated blood and the left one with oxygenated blood contract simultaneously to push their blood whereas on the two sides the blood remains unmixed as the bloaod passes very fast from the ventricle. Ventricle contracts to push the blooad into truncus arteriosus through an aperture guarded by a value . From truncus arteriosus the blood enter the Pulmonary arteries which carry the blood to lungs for oxygenation and , The systematic arteries which supply the pure blood to all parts of the body and , the carotid arteries which supply blood to the brain. 

Sunday, August 24, 2014

Disorders of Respiratory system and Health Risk Associated with Cigarette Smoking

According to world health Organization (WHO) smoking could become the world's biggest killer by the year 2020, causing more deaths than any other diseases.

1. Smoking :
Smoking affects the lungs . Heavy smoking can also damage the heart and blood vessels. Non-smokers are also effected if they spend much time in the a room with people who are smoking. Cigarette smoke contains three main ingredients . These are nicotine , tar and carbon mono-oxide. Each of these has its own effects on the body.
Nicotine is addictive. Once the body gets used to it, it is very hard to do without it .  it increases the heart beat and blood pressure and causes hear diseases . Tar increases the chances of getting lung cancer. where as carbon mono oxide is poisonous.
2. Bronchitis:
it is the inflammation of the bronchial tubes , which may be caused by smoking or by bacterial infection. when a person smokes , tiny particles in the smoke get caught on the lining of the trachea and bronchial tubes . Extra mucus is produced and the cilia stop beating. The mucus collects in the bronchial tubes and this gives rise to the 'smokers cough'. if the tubes become infected, the person may get chronic bronchitis chronic means long lasting so the disease persists.

3. Tuberculosis:
it is another disease of the lungs caused by bacteria (Mycobacterium tuberculosis) which destroy the lung tissues. it can be diagnosed by chest X-ray and sputum test. At one time T.B. was one of the most common causes of death, but modern medicine has now nearly cured it.

4. Lung Cancer:
To day lung cancer has taken over from T.B as the major killer. in luing cancer a growth develops in the wall of the bronchial tubes . This blocks them, so breating becomes more and more difficult . The lung Cancer can be detected by chest X-ray. If a growth is visible , it is removed by surgery ir may be destroyed by radiation therapy. 
Other Common respiratory Diseases are: 
Laryngitis------------ inflammation of the larynx
Pneumonia-----------servers inflammation of the luings, caused by a type of bacteria (Pheumococcus).