Zoology MCQs for NEET — Practice Questions with Answers

Oxygen-containing blood is transported from the lungs to the heart by the pulmonary veins. Unlike most veins that carry deoxygenated blood, the pulmonary veins carry oxygen-rich blood from the lungs to the left atrium of the heart, where it is then pumped to the rest of the body.

Approximately 97% of oxygen is transported to tissues through red blood cells (RBCs). Hemoglobin in the RBCs binds to oxygen molecules and carries them to various tissues in the body.

The metal ion present in hemoglobin is iron (Fe). Iron is crucial for the ability of hemoglobin to bind to oxygen and transport it throughout the body.

About 20% of carbon dioxide (CO₂) is transported in the form of carbamino compounds, which are formed when CO₂ binds to the amino groups of hemoglobin and other proteins.

The largest amount of CO₂ in the blood is transported as bicarbonates. CO₂ reacts with water in the red blood cells to form carbonic acid, which quickly dissociates into bicarbonate ions and hydrogen ions. This process is catalyzed by the enzyme carbonic anhydrase. About 70-75% of CO₂ is transported in this form, making it the predominant method of CO₂ transport in the blood.

Flattening of alveolar ducts can lead to emphysema. Emphysema is a chronic lung condition characterized by the destruction of the alveoli (air sacs) in the lungs, leading to reduced surface area for gas exchange and difficulty in breathing. The alveolar ducts may become flattened or distorted, contributing to the symptoms of emphysema.

The trachea terminates in the bronchi. The trachea, also known as the windpipe, divides into two main bronchi (right and left) at its lower end. These bronchi further branch into smaller bronchioles and eventually lead to alveoli where gas exchange occurs.

Pneumonia is an infection that inflames the air sacs in one or both lungs, which can fill with fluid. It is caused by bacteria, viruses, or fungi, and not by specific gases, chemicals, or suspended particulate matter in the air. Silicosis, asbestosis, and fibrosis are all lung conditions caused by inhalation of harmful substances.

Crocodiles are reptiles, and they respire through lungs. Fish respire through gills, cockroaches through tracheae, and earthworms through their skin. Understanding the respiratory systems of different organisms is crucial for NEET biology.

The human lungs are located in the thoracic cavity, which is the chamber of the body of vertebrates that is protected by the thoracic wall (rib cage and associated muscles). This is a fundamental concept in human anatomy for NEET students.