Breathing and Exchange of Gases Test 8

Cyanosis is the appearance of a blue or purple colouration of the skin or mucous membranes due to the tissues near the skin surface having low oxygen saturation. Levels of 2.0 g/dL of deoxyhaemoglobin may produce cyanosis.

Solution

Correct answer is option C.
Explanation for correct option:

• Asthma attacks can be triggered by exposure to allergens, such as pollen, mould or animal dander.
• This type of asthma is known as allergic asthma.
• Seasonal allergic rhinitis occurs when a person comes in contact with an allergen or a substance that he or she is sensitive to like pollens.

When the heart is not able to pump efficiently, blood backs up into the veins that take blood through the lungs. As the pressure in these blood vessels increases, fluid is pushed into the air spaces (alveoli) in the lungs. This fluid reduces normal oxygen movement through the lungs. These two factors combine to cause shortness of breath in heart failure.

The medulla oblongata is the lower half of the brainstem, which is continuous with the spinal cord, the upper half being the pons. The medulla contains the cardiac, respiratory, vomiting and vasomotor centres and therefore deals with the autonomic (involuntary) functions of breathing, heart rate, and blood pressure.

Deep breathing rises the $$O_2$$ level of the blood. By excess formation of oxyhaemoglobin the acidity of blood increases. To control it, more of free $$CO_2$$ changes into bicarbonates and the free $$CO_2$$ level in the blood decreases. So due to lack of stimulant for inspiratory centre cessation of breathing takes place, after some time $$O_2$$ is consumed by the tissues and rise in $$CO_2$$ stimulates breathing again. So, the correct answer is 'Both too much O$$_2$$ and very little CO$$_2$$ in the blood'.

Hint: It involves the incomplete oxidation of glucose in the absence of oxygen

The right lungs of human is divided into three lobes, the superior, middle, and inferior, by two interlobular fissures. The middle lobe, the smallest lobe of the right lung, is wedge-shaped. The right lung is divided by the oblique fissure, which separates the inferior lobe from the middle and superior lobes, and the horizontal fissure, which separates the superior from the middle lobe.

• Alveoli are the air sacs of the lungs. They have thin walls surrounded by blood capillaries (another layer of simple squamous epithelium). Gas exchange occurs in the alveoli. 
• During inhalation, oxygen gas is in higher concentration in the alveoli than in the blood and so it diffuses into the blood through this thin layer of cells.
• During exhalation, carbon dioxide is in higher concentration in the blood than in the alveoli and so it diffuses into the alveoli through this thin layer of cells.
  

In humans, trachea is a straight tube extending up to the mid-thoracic cavity, which divides at the level of 5th thoracic vertebra into a right and left primary bronchi. Each bronchi undergoes repeated divisions to form the secondary and tertiary bronchi and bronchioles ending up in very thin terminal bronchioles. The tracheae, primary, secondary and tertiary bronchi, and initial bronchioles are supported by incomplete cartilaginous rings.