Answer key

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Last edited 25 days ago by Learn LoopHQ.

Chapter: 05. Human Respiratory System

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Section A: Multiple Choice Questions

c) Lungs

b) Oxygen

c) Larynx

b) It moves downwards and flattens

c) Pneumonia

Section B: Fill in the Blanks

respiration

nasal passages

trachea (or windpipe)

alveoli

mechanical, biochemical

haemoglobin

Section C: True/False Questions

False

True

False

True

Section D: Explanations of Terms

Inhalation: The process of taking in fresh air rich in oxygen into the lungs. During this, the volume of the chest cavity increases, and air rushes in.

Alveoli: Tiny, thin-walled, air-filled sacs located at the end of the bronchioles in the lungs, where the exchange of gases (oxygen and carbon dioxide) takes place.

Haemoglobin: The respiratory pigment found in red blood cells that combines with oxygen to transport it from the lungs to various body cells.

Breathing Rate: The number of times a person breathes (one inhalation and one exhalation) in one minute.

Section E: Short Answer Questions

The nasal passages filter out dust, smoke, pollen, and microbes from the air, and they also warm and moisten the air before it enters the lungs.

The C-shaped rings of cartilage support the wall of the trachea (windpipe), preventing it from collapsing and ensuring that the airway remains open for air passage.

Our breathing rate increases during fast running or heavy exercise because our body needs more energy. This higher energy demand requires more oxygen for cellular respiration and leads to a greater production of carbon dioxide, which needs to be expelled faster.

Inhaled air contains about 21% oxygen and 0.03% carbon dioxide. Exhaled air, however, has less oxygen (about 16.4%) and significantly more carbon dioxide (about 4.1%) because oxygen has been used by the body and carbon dioxide has been released.

Two common symptoms of Asthma are shortness of breath and difficulty in breathing. Another symptom is a whistling or wheezing sound while exhaling.

Section F: Diagram-Based Question

1: Nasal passage, 2: Pharynx, 3: Larynx, 4: Trachea

Section G: Differentiate Concepts

Breathing and Respiration:

Breathing is a mechanical process involving the physical movement of air into and out of the lungs. Its main outcome is to provide oxygen to the body and remove carbon dioxide.

Respiration is a biochemical process that involves both gas exchange and the breakdown of food (glucose) inside cells to release energy for life activities.

External Respiration and Internal Respiration:

External Respiration occurs in the lungs, specifically between the air in the alveoli and the blood flowing through the capillaries surrounding them.

Internal Respiration occurs throughout the body, between the blood and individual body cells.

Section H: Long Answer Questions

The mechanism of breathing involves two alternating phases: inhalation and exhalation. During inhalation, the rib muscles contract, pulling the ribs upwards and outwards. Simultaneously, the diaphragm contracts and flattens, moving downwards. These actions increase the volume of the thoracic cavity and lungs, which lowers the air pressure inside, causing fresh air to rush in. During exhalation, the rib muscles and diaphragm relax. The ribs move downwards and inwards, and the diaphragm moves upwards to its original dome shape. This decreases the volume of the thoracic cavity and lungs, increasing internal air pressure and forcing carbon dioxide-rich air out.

The lungs are the primary organs for gas exchange, which mainly takes place within tiny air sacs called alveoli. These alveoli have very thin walls and are surrounded by a dense network of blood capillaries, providing a large surface area. When we inhale, fresh, oxygen-rich air fills the alveoli. The oxygen then efficiently diffuses from the alveoli into the blood capillaries. At the same time, carbon dioxide, a waste product carried by the blood from body cells, diffuses from the blood into the alveoli, ready to be expelled during exhalation. This continuous exchange ensures the body receives vital oxygen and removes waste carbon dioxide.

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