The following statements refer to gas carriage by blood. Choose the correct statement:

1. After leaving the lungs, each litre of blood contains about 20 ml of oxygen.

2. Haemoglobin is half saturated with oxygen when the PO₂ is about 30 mm Hg

3. As the PCO₂ rises, the affinity of haemoglobin for oxygen is increased.

4. Each litre of arterial blood contains about 50 mL of carbon dioxide.

Study the spirograph and identify the correctly matched volumes from the codes given:

         TV        IRV     ERV       RV      VITAL CAPACITY
1.       A          c         B          D              E
2.       A          B        C          D               E
3.       B          A        C          D               E
4.       C          B        A          D               E

Fibrous connective tissue builds up in the lungs causing them not to inflate properly, and actually deflating them is called:

1. chronic bronchitis

2. emphysema

3. pulmonary fibrosis

4. asthma

The C-shaped cartilaginous rings around the trachea are open posteriorly to:

(1) allow for expansion of the esophagus during swallowing 

(2) allow the vocal cords to relax

(3) prevent food from entering the nasal cavity during swallowing

(4) prevent food from entering the trachea

The trachea is lined with

1. ciliated simple squamous epithelium
2. stratified squamous epithelium
3. pseudostratified ciliated columnar epithelium
4. pseudostratified squamous epithelium

When you hold your breath which of the following gas changes in blood would first lead to the urge to breathe?

(1) Falling O₂ concentration

(2) Rising CO₂ concentration

(3) Falling CO₂ concentration

(4) Rising CO₂ and falling O₂ concentration

Lungs are made up of air-filled sacs, the alveoli. They do not collapse even after forceful expiration, because of

1. Residual Volume (RV)

2. Inspiratory Reserve Volume (IRV)

3. Tidal Volume (TV)

4. Expiratory Reserve Volume (ERV)

The partial pressure of oxygen in the alveoli of the lungs is  

(1) equal to that in the blood

(2) more than that in the blood

(3) less than that in the blood

(4) less than that of carbon dioxide

Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because

(1) there is a negative pressure in the lungs

(2) there is a negative intrapleural pressure pulling at the lung walls

(3) there is a positive intrapleural pressure

(4) pressure in the lungs in higher than the atmospheric pressure

Reduction in pH of blood will

(1) reduce the blood supply to the brain

(2) decrease the affinity of hemoglobin with oxygen

(3) release bicarbonate ions by the liver

(4) reduce the rate of heart beat