Question

RESPIRATORY SYSTEM

1.Name each organ of the mammalian respiratory system and provide its function.

2.Use Boyle’s law and the anatomy of a mammal to explain how inhalation and exhalation occurs.

3.What is “partial pressure”? Explain its role in gas exchange.

4.What is the difference between external gills and internal gills? What are the advantages/disadvantages of each?

5.Structure determines function: what features are common in different respiratory organs, and how do these features help with gas exchange?

Answer 1

1)The respiration is the process of exchange of gases . It consists of two zones -

a) Conducting zone - includes the organs and structures not directly involved in gas exchange. They provide route for passage of air in and out , humidity and warms the air and removes the pathogens.

• external Nose - It serves as pathway for passage of air the and contains olfactory nerves. It humidifies the air and blocks the entry of pathogen into the respiratory system.
• Pharynx - It is a tube formed by skeletal muscle and is divided into three parts - Nasopharynx, oropharynx and laryngopharynx. Nasopharynx serves as airway and contains tonsils whereas oropharynx is pathway for both air and food. The laryngopharynx later on seperates into larynx and oesophagus.
• Larynx - Cartilaginous structure connecting pharynx to trachea. It regulates the volume of air entering into the lungs. It has vocal cords that helps in speech.
• Trachea - It is also called as windpipe.It allows the air to enter and pass out of the body.
• Bronchial tree - The trachea branches into the right and left primary bronchi at the carina.Like other conducting zone structure bronchial tree serves as structure to passage of air in and out of lungs. It also have mucous membrane which traps debris and pathogens. The tertiary bronchi forms bronchioles.

b) Respiratory zone -It includes structures that are directly involved in gas exchange. The area from where the terminal bronchioles join to respiratory bronchiole, Leading to an alveolar duct, opening into a cluster of alveoli.

• Alveoli - It is small grape-like sac that is connected with the alveolar duct. The alveoli is responsible for gaseous exchange . It has type 2 pneumocytes which secretes pulmonary surfactant which prevents the collapse of alveoli. The alveolar macrophages remove debris and pathogens.

2) According to Boyle's law, For a given amount of gas at the constant temperature, increasing its volume decreases its pressure, and vice-versa. That is the pressure is inversely proportional to the volume of volume of gas.

During inhalation, muscles increase the size of the thoracic cavity and lungs expands. This increases chest volume, so pressure inside the lungs decreases. When pressure inside the lung decreases hence the air enters inside the lung. This way inspiration takes place.

The opposite happens during expiration the muscle decreases the size of thoracic cavity and volume of thoracic cavity reduces. This causes increase in pressure inside thoracic cavity and air moves out of the lungs. Hence expiration takes place.

3)Partial pressure of a gas is the pressure of the particular gas in the mixture of gases.

The role of partial pressure of gases in gaseous exchange is explained by Henry's law. Henry’s law depicts the behavior of gases when they come into contact with a liquid, such as blood. It states that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that particular gas. More the partial pressure of the gas, more the number of gas molecules solubility in liquid.

That means , Carbon dioxide's partial pressure is greater in the blood entering the lungs than it is in the alveolar air. And the gases move from a high to low partial pressure. The partial pressure of oxygen is lower in the blood than in alveoli, so it diffuses into the blood by this gaseous exchange takes place in the blood.

The oxygen can be delivered from lungs to bloodstream this way.