and exchange of gases contact 17

Transport and exchange of oxygen and carbon dioxide

Blood exchanges oxygen and carbon dioxide between the body and the external environment.
The exchange of gases takes place in the lungs during pulmonary circulation.
Haemoglobin present in the blood helps in the exchange of both these gases.

Oxyhaemoglobin and carbaminohemoglobin

Oxyhaemoglobin

Oxyhaemoglobin is the bright red, oxygenated form of haemoglobin in the red blood cells, in which a molecule of oxygen has attached itself reversibly to the iron atom in the haemoglobin molecule.

Oxyhaemoglobin transports oxygen from the lungs to the tissues.

Carbaminohaemoglobin

Carbaminohaemoglobin is formed when haemoglobin binds to carbon dioxide.
It carries 10 % of the total carbon dioxide in the body.
Haemoglobin has an affinity towards both oxygen and carbon dioxide. Hence after transporting oxygen to the tissues it can bind to carbon dioxide in the tissues and carry it back to the lungs.

Breathing tract or respiratory tract

The respiratory tract is a complex arrangement of organs and tissues.
Its main functions are taking in oxygen and getting rid of carbon dioxide.

Alveoli

They are structural and functional unit of lungs is alveoli.
A dense network of blood capillaries is found in alveoli.

Respiratory tree

The respiratory tree is the branching structure of airways supplying air to the lungs and includes the trachea, bronchi and bronchioles.

Bronchial tree

When trachea enters into thoracic cavity, it divides in two branches called as primary bronchus. Branches of primary bronchus upto terminal bronchioles makes bronchial tree.

Nose

Structure-

Nose is the opening that connects the environment with respiratory tract.

The external part of the nose have two nostrils.
The two nostrils opens into a pair of nasal chambers

Function-

It warms the air, while passing through it.
It adds moisture to the air.
It's mucous secretion traps dust particles.

Larynx

The hollow muscular organ forming an air passage to the lungs and holding the vocal cords in humans and other mammals.

It is also called as voice box.

Trachea

A large membranous tube reinforced by rings of cartilage, extending from the larynx to the bronchial tubes is called as trachea.
Its walls are supported by C shaped rings of cartilage.

It conveys air to and from the lungs.

Bronchi

Bronchi are the main passageway into the lungs, formed from trachea.
They are hollow tubes surrounded by cartilage rings.
They are lined with cilia and mucus secreting cells.
They carry air into the lungs.
Bronchi are further divided into smaller bronchioles.

Lungs

Lungs are composed of the bronchi, bronchioles and alveoli.
The two lungs are roughly cone shaped.
The left lung has two lobes and the right one has three lobes.
The left lung is slightly small that than the right lung.

Blood supply to the lungs

Pulmonary circulation is the portion of the cardiovascular system that carries oxygen-depleted blood away from the heart, to the lungs and returns oxygenated (oxygen-rich) blood back to the heart.
De-oxygenated blood from right ventricle is pumped to the lungs, where it releases carbon dioxide and picks up oxygen.
Oxygenated blood leaves the lungs through pulmonary veins, completing the pulmonary cycle.

Structure of nose

Nose is an olfactory organ.
It mainly helps in smelling. It has several olfactory receptors which help in olfactory sensation.
The main parts of nose include nostrils, nasal septum and olfactory receptors.
The olfactory sensation generated in the nose is carried to the brain by olfactory lobe.

Capacities of the lungs

Tidal volume- The amount of air breathed in and out in normal quiet breathing. It is about 500 ml.

Dead air space- Some of the air in the trachea and bronchi do not takes part in breathing, called as dead air space. it is about 150ml.

Alveolar air- The tidal volume contained in alveoli. It is about 350ml.

Inspiratory reserve volume- The inspiratory reserve volume (IRV), about 3,000 mL. It is the additional air that can be forcibly inhaled after the inspiration of a normal tidal volume.
Expiratory reserve volume- The expiratory reserve volume (ERV)is the additional air that can be forcibly exhaled after the expiration of a normal tidal volume. It is about 1,200 mL.
Vital capacity- The maximum amount of air a person can expel from the lungs after a maximum inhalation. It is about 4500 ml.
Residual volume- The volume of air that remains in the lungs even after maximum or forceful expiration. The average Residual Volume (RV) in healthy males is about 1200 ml. In females, the average RV is 1100 ml.
Total lung capacity- Maximum amount of air that can be held at any time in the two lungs, called as total lung capacity. It is about 6000 ml.

Inspiratory reserve volume

It is the extra amount of air that can be inspired forcibly after a normal respiration.

Diffusing capacity

Diffusing capacity is the volume of gas that diffuses though the membrane per minute for a difference of 1mm Hg.
It is 21 ml/minute/mm Hg of .

Expiratory reserve volume

The expiratory reserve volume (ERV) is the additional air that can be forcibly exhaled after the expiration of a normal tidal volume.
It is about 1,200 mL.

Residual volume

The volume of air that remains in the lungs even after maximum or forceful expiration.
Residual volume is the only lung volume that cannot be measured directly using a spirometer.
The residual volume exists because the pleural fluid stretches and holds the lungs against the ribs.
The average Residual Volume (RV) in healthy males is about 1200 ml.
In females the average RV is 1100 ml.
RV may be significantly high in obstructive lung diseases.

Inspiratory capacity

It is the total volume of air a person can inspire after a normal expiration.

Expiratory capacity

It is the total volume of air a person can expire after a normal inspiration.

Vital capacity

The maximum amount of air a person can expel from the lungs after a maximum inhalation is vital capacity.
It is about 4500 ml.

Functional residual capacity

Lung capacities are nothing but the sum of two or more lung volumes.
There are four major lung capacities that can be calculated from the summation of two or more lung volumes
Functional residual capacity equals the sum of expiratory reserve volume (ERV) and the residual volume (RV)
In other words, functional residual capacity is the amount of air that remains in the lungs of an individual at the end of normal expiration.
It is represented by the formula FRC= ERV + RV
The average FRC values in males is 2400 ml [ERV(1200 ml) + RV (1200 ml)] and in females it is 1800 ml [ERV (700 ml) + RV (1100 ml)]

Total lung capacity

Total lung capacity is the maximum amount of air that can be held at any time in the two lungs, called as total lung capacity.
It is about 6000 ml.

Inspiration

Inspiration or inhalation is the process of bringing air from outside the body into the lungs.
It is carried out by creating a pressure gradient between the lungs and the atmosphere.
When air enters the lungs, the diaphragm contracts toward the abdominal
cavity, thereby increasing the space in the thoracic cavity for accommodating the inhaled air.
The volume of the thoracic chamber in the anteroposterior axis increases with the simultaneous contraction of the external intercostal muscles.
This causes the ribs and the sternum to move out, thereby increasing the
volume of the thoracic chamber in the dorsoventral axis.
The overall increase in the thoracic volume leads to a similar increase in the pulmonary volume.
Now, as a result of this increase, the intra-pulmonary pressure becomes
lesser than the atmospheric pressure. This causes the air from outside
the body to move into the lungs.

Human respiratory system

Human respiratory system helps to inhale the respiratory gas which is distributed by all through the body and the carbon dioxide is exhaled.
The nasal cavity, larynx, trachea, alveoli and lungs are the part of human respiratory system.

Difference between inspiration and expiration

Part of respiratory system	Inspiration	Expiration
Diaphragm	Contracts and flattens downwards	Relaxes and moves upwards
External intercostal muscles Internal intercostal muscles	Muscles contract Relaxed	Muscles relax Contracts for forced expiration
Rib cage and sternum	Move upwards and outwards	Move downwards and inwards
Thoracic cavity	Increases	Decreases
Air pressure	Decrease inside thorax and lungs	Increase inside thorax and lungs
Air movement	Extreme air pressure drives air into lungs at low pressure	Air forced out of lungs by thorax compression and elastic recoil of lungs

Inspiratory muscle

Contraction of these muscles brings about inspiration.
For example, diaphragm muscle and external intercostal muscle.

Expiration

It occurs due to reverse movements of the ribs and diaphragm.
The external intercostal muscles relax and thus the ribs becomes depressed.
The diaphragm is relaxed and moves upward to its original position.
Thus the thoracic cavity becomes small and lungs are compressed, which forces air out of the lungs.

Expiration

It occurs due to reverse movements of the ribs and diaphragm.
The external intercostal muscles relax and thus the ribs becomes depressed.
The diaphragm is relaxed and moves upward to its original position.
Thus the thoracic cavity becomes small and lungs are compressed, which forces air out of the lungs.

Exchange of gases between alveoli and blood

The exchange of gases between lung alveoli and pulmonary capillaries is called external respiration.

Exchange of gases between blood and tissue cells

The exchange of gases between tissue blood capillaries and tissue cells is called internal respiration.
The partial pressure of oxygen is higher than that of the body cells and the partial pressure of carbon dioxide is lesser than that of the body cells.

Transport of oxygen in the blood

Oxygen is transported in the following manner:

As dissolved gas
As oxyhaemoglobin

Oxygen haemoglobin dissociation curve

Factors affecting oxygen hemoglobin dissociation curve

Factors affecting oxygen hemoglobin dissociation curve are as follows:

Shift to right: It indicates dissociation of oxygen from haemoglobin.
Shift to left: It indicates acceptance of oxygen by haemoglobin.

Bohr effect

An increase in carbon dioxide in the blood causes oxygen to be displaced from the haemoglobin. This is Bohr effect.

Transport of carbon dioxide

It is transported in three ways:

Transport of CO in dissolved form
Transport of CO as a bicarbonate
Transport of CO as carbaminohaemoglobin

Chloride shift

Chloride shift is a process which occurs in a cardiovascular system and refers to the exchange of bicarbonate (HCO) and chloride (Cl) across the membrane of red blood cells (RBCs).

Release of carbon dioxide in the alveoli

The pulmonary arteries carry deoxygenated blood to the lungs.
This blood contain carbon dioxide as dissolved in blood plasma, as bicarbonate and as carbaminohaemoglobin.

Haldane effect

Binding of oxygen with haemoglobin tends to displace carbon dioxide from the blood.
This is called Haldane effect.

Control of breathing movements

Breathing is mainly controlled involuntarily. Some of it is controlled voluntarily.

The respiratory centre located in the medulla oblongata controls breathing.

The centre is stimulated by .
The more in the blood, faster the breathing.

Pleuritis

Pleuritis is an inflammation of the pleura.
There are two layers; one covering the lung and the other covering the inner wall of the chest.
These two layers are lubricated by pleural fluid.
Pleurisy is frequently associated with a pleural effusion.

Mountain sickness

Physical distress from difficulty adjusting to lower oxygen pressure at high altitude.
In order to oxygenate the body effectively, breathing rate has to be increased.
The symptoms include breathlessness, headache, dizziness, nausea, vomiting, mental fatigue and bluish tinge on the skin, nails and lips.

Emphysema

Cause:

Cigarette smoking
Inhalation of toxic substance

Symptoms:

Difficulty in exhaling

Prevention:

Avoid air pollutants
Avoid cigarette smoking

Occupational respiratory disorders

Cause:

Exposure to silicosis and asbestoses

Symptoms:

Inflammation

Prevention:

Minimize exposure to harmful dust
Health workers should be regularly checked up.

Diphtheria

Cause:

Corynebacterium diphtheriae

Symptoms:

Enlarged mucous membranes of the oropharynx, nasopharynx and larynx.

Coryza

Cause:

Rhinovirus

Symptoms:

Sneezing
Excessive nasal secretion
Dry cough
Congestion

Influenza

Cause:

Influenza virus

Symptoms:

Chills
Fever
Headache
Muscular pain

Severe acute respiratory syndrome (SARS)

Cause:

Human coronavirus

Symptoms:

Hypoxia
Loss of appetite
Fever

Prevention:

Isolation

Hypercapnoea

It is the state of reduced carbon dioxide concentration in the blood.

Hypocapnoea

It is the state of reduced carbon dioxide concentration in the blood.

Anoxia

It is absence of oxygen supply to the tissues.

Dyspnoea

It is the state of discomfort due to difficulty in breathing.

Apnoea

It is the stage of stoppage of breathing temporarily.

Tcahypnoea

It is the state of fast breathing.

Bradypnoea

It is the state of slow breathing.

Eupnoea

It is the state of normal breathing. In man, the rate of normal breathing is 12-16 per minute. In infants, rate of breathing is 44 per minute. Rate of breathing is slowest while sleeping.

Hiccups

Hiccup is an involuntary spasm of the diaphragm and respiratory organs, with a sudden closure of the glottis and a characteristic gulping sound.

Sneezing

Sneezing is to make a sudden involuntary expulsion of air from the nose and mouth due to irritation of one's nostrils.

Snoring

Snoring is making a snorting or grunting sound while asleep.

Disorders of respiratory system

Disorders related to respiratory system include:

Bronchial asthma
Emphysema
Occupational respiratory disorder
Bronchitis
Pneumonia
Pulmonary tuberculosis
Diphtheria
Coryza
Influenza, etc

Class 11 science (biology) all chapter concepts .

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