(i) The contraction of diaphragm initiates inspiration,as it increases the volume of the thoracic chamber in the antero-posterior axis .
(ii) Hence, the intra-pulmonary air pressure decreases to less than the atmospheric pressure; hence, air from outside moves into the lungs

(i) The conducting part transports the air into alveoli.
(ii) It clears the inspired air from foreign particles.
(iii) It brings the air to the body temperature.
(iv) It moistenslhumidifies the air.

For shock absorption and expansion / contraction while breathing in / out.

Combines with carbon dioxide to form carbamino-haemoglobin.

A cigarette smoker is more likelihood to suffer from emphysema. This will reduce his total lung capacity.

During asthmatic attacks there is sudden spasm or contraction of bronchi. This leads to reduced breathing capacity and the person feels a sense of breathlessness.

External and internal intercostal muscles, situated between ribs.

During inspiration the pO₂ in alveoli is more than pO₂ in blood capillaries.

Marine mammals (e.g, seals and whales) can make long underwater dives as they have
(i) more blood per kg of body weight
(ii) can store more oxygen in blood and muscles
(iii) have a large spleen with blood
(iv) can reduce O₂ consumption rate when underwater

Haemoglobin consists of a protein globin and pigment haem. The four portions of iron in haem combine with molecule of oxygen. It is an easy reversible reaction to form oxyhaemoglobin
\(Hb+O_{ 2 }\rightleftharpoons HbO_{ 2 }\) 
Whereas, the complex formed by the reaction of carbon monoxide and haemoglobin is incredibly strong
Hv +CO \(\rightarrow\) HbCO
(Haemoglobin)   (Carboxy haemoglobin)
As a rsult of this strong bonding between the haemoglobin and carbon monoxide, the haemoglobin looses its affinity to oxygen thus, may lead to choking or even death.

Difference between oxyhaemoglobin and carbaminohaemoglobin are

Haldane effects states that binding of oxygen with haemoglobin tends to displace CO₂ from the blood.It is quantitatively moe important in promoting CO₂ transport than the Bohr effect in O₂ transport.Thus, Haldane effect and Bohr effect complement each other.

Larynx is often called as Adam's apple. It is more prominent in males than females.

Increase in pCO₂ tension in blood brings rightward shift of the oxygen-dissociation curve of haemoglobin thereby decreasing the affinity of Hb for O₂ .this effect is called Bohr's effect.
It plays a crucial role in enhancing oxygenation of the blood in the lungs and in the release of O₂ in the tissues.

Vital capacity is the maximum amount of air a person can breathe in after a forced expiration or breathe out after a forced inspiration.It represents the maximum amount of air one can renew in the respiratory system during a single respiration.Thus, the greater the VC, more is the energy available to the body.

Nearly 70% of CO₂ enters the RBSc and reacts with water to form carbonic acid in the presence of enzyme carbonic anhydrase.This dissociates to form bicarbonate ions, which are circulated by plasma

Partial blocking of upper respiratory tract by tongue leading to turbulence of airflow causes a rough rattling inspiratory noise called snoring

Nasal breathing is advisable because it is healthier as the air inhaled gets filtered through the hairs present inside the nose, so cleaner air reaches to the lungs.

Mammals use negative pressure to suck air in. The diaphragm contracts and move down, the intercostal muscles contract and move up and out. This causes the lungs to expand. The pressure inside the lungs drops.

(i) Thin squamous epithelium of alveoli.
(ii) Endothelium of alveolar capillaries.
(iii) Basement substance in between