Notes-Part-1-Class-12-Biology-Chapter-8-Respiration and Circulation-Maharashtra Board

Respiratory organs in different organisms :

1) Aquatic organisms :

 2) Aquatic organisms :

 3) Underwater organisms : Turtles - Respiratory surface/ organ : cloaca

• Only at the time of diving or when underwater, turtles perform cloacal respiration. There are a pair of accessory air bladders connected to the cloaca which can absorb oxygen from the water.

1) Nostrils and nasal chambers : The nostrils are external openings of the nose.

• Oxygen rich air is taken into the body through the nostrils or external nares. Carbon dioxide and water vapour are released out of the body through the nostrils.
• The internal nares open into the pharynx. The space between the external and internal nares is known as nasal chamber. The nasal chamber is lined internally by mucous membrane and ciliated epithelium.
• The nasal chamber is divided into right and left parts by a cartilage called mesethmoid.

Every nasal chamber is further divided into three regions : (i) Vestibule (ii) Respiratory part (iii) Sensory part.

• Vestibule : The anteriormost part of the nasal chamber is vestibule. Hair present in this chamber prevent the dust particles from going inside.
• Respiratory part : It is the part which is richly supplied by capillaries. Air is made warm and moist in this region.
• Sensory part : The sensory epithelium lines this region. It is concerned with the detection of smell.

3) Larynx: The larynx produces sound.

• In males, it increases in size at puberty. This is termed as Adam’s apple.
• From the pharynx air enters the larynx. The opening through which it enters is called glottis.
• The glottis has a guarding flap called epiglottis.
• The epiglottis prevents the entry of food particles into the trachea.
• The vocal cords are seen along the side of the glottis. They are made of elastic tissue. They produce sound.
• Passage of air between the vocal cords and modulations created by tongue, teeth, lips and nasal cavity produce voice.

6) Lungs :

• The lungs are principal respiratory organs located in the thoracic cavity.
• They are pinkish, soft, hollow, paired, elastic and distensible organs.
• The lung is enclosed in a pleural sac.
• The pleural sac has two membranes—an outer parietal and an inner visceral which enclose the pleural cavity.
• The pleural fluid which is present in the pleural cavity lubricates and prevents friction when pleural membranes slide on each other.
• The lungs are richly supplied with blood capillaries and hence are highly vascular organs.
• The left lung has two lobes while the right lung has three lobes.
• Each lobe has many bronchioles and alveolar sacs.

Mechanism of respiration :

The process of respiration includes breathing, external respiration, internal respiration and cellular respiration.

Breathing : Breathing is the process by which the air comes in and goes out of the lungs.

• The rate of gaseous exchange is speeded up by breathing.
• Breathing is a part of respiration and the terms breathing and respiration are not synonymous.
• Inspiration and expiration together make breathing.

(i) Inspiration: Inspiration is an active process brought about by ribs, intercostal muscles, sternum and diaphragm.

• The intercostal muscles contract and pull the ribs outwards. This increases the space in the thoracic cavity. The lower part of sternum is simultaneously raised. The diaphragm contracts and flattens, This causes further increase in the volume of thoracic cavity.
• Pressure in the lungs decreases and the volume increases due to expansion of the lungs.
• Due to pressure difference the atmospheric air rushes into the lungs through respiratory passage as a result of which air is inspired in.

(ii) Expiration : Expiration is the passive process.

• During expiration the intercostal muscles relax and the ribs are pulled inwards.
• The diaphragm is relaxed and becomes dome-shaped.
• The volume of the thoracic cavity is reduced.
• The pressure on the lungs is increased as a result of which they get compressed.
• Air is thus expelled out of lungs through the nares.

(iii) Respiratory cycle : Respiratory cycle is alternate inspiration and expiration process.

• In adult man there are 16 to 20 respiratory cycles per minute.
• The medulla oblongata in the brain controls the respiration.

External respiration/exchange of gases at the alveolar level :

• Exchange of gases between the alveolar air and the blood takes place through thin squamous epithelial layer of alveolus and similar layer of the capillary wall.
• Respiratory gases will always diffuse from an area of higher partial pressure to an area of lower partial pressure in these two regions.
• Due to difference in partial pressure, carbon dioxide diffuses from the capillaries into the alveolus whereas oxygen will diffuse from alveoli to the capillaries.

Carbon monoxide poisoning :

• Haemoglobin has affinity for oxygen. But for carbon monoxide it has about 250 times more affinity than that of oxygen.
• With carbon monoxide it forms a stable compound called carboxyhaemoglobin.
• Due to such combination, the oxygen is not transported to the tissues. The tissues thus suffer from oxygen starvation. This leads to asphyxiation and in extreme cases death.
• Treatment of carbon monoxide poisoning is given by administering oxygen-carbon dioxide mixture to make high PO₂ level to dissociate the carbon monoxide from haemoglobin.
• Carbon monoxide poisoning occurs in closed rooms with open stoves, gas burners, automobile engines or any incomplete combustion.

Pulmonary volumes and capacities (Normal values)

Lung Volumes :

• Tidal volume (T.V.) : It is the volume of air inspired or expired during normal breathing. It is 500 ml.
• Inspiratory reserve volume (IRV) : The maximum volume of air, or the extra volume of air, that is inspired during forced breathing in addition to T.V. Its value is 2000 to 3000ml.
• Expiratory reserve volume (ERV) : The maximum volume of air that is expired during forced breathing after normal expiration. Its value is 1000 to 1100ml.
• Dead space (DS) : The volume of air that is present in the respiratory tract (from nose to the terminal bronchioles), but not involved in gaseous exchange. It is 150 ml.
• Residual volume (RV) : The volume of air that remains in the lungs and the dead space even after maximum expiration. It is 1100 to 1200ml.

Lung capacities :

• Total Lung capacity : The maximum amount of air that the lungs can hold after a maximum forcefull inspiration (5200 to 5800ml).
• Vital capacity (VC) : The maximum amount of air that can be breathed out after a maximum inspiration. It is the sum total of TV, IRV and ERV and is 4100 to 4600ml

Common disorders of respiratory system (Cause, Symptoms and Treatment) :

(1) Emphysema :

• Cause : Cigarette smoking and air pollution
• Symptoms : Over inflation of the alveoli, rupture of alveolar wall.
• Treatment : Quit smoking, avoid polluted air, administer oxygen to relieve symptoms.

(2) Bronchitis :

• Cause : Certain bacterial or viral infection, also caused by smoking and air pollution.
• Symptoms : Inflammation of bronchi, regular coughing with greenish-yellow sputum.
• Treatment : Quit smoking, avoid polluted air, if possible move to warmer, drier climate

(3) Sinusitis :

• Cause : A viral infection or common cold
• Symptoms : Inflammation or swelling of the tissue lining the sinuses.
• Treatment : If bacterial, take antibiotics, decongestants, use vaporizer

(4) Laryngitis :

• Cause : Certain viruses, bacteria
• Symptoms : Hoarseness, cough, difficulty in swallowing, inflammation of larynx and vocal cords.
• Treatment :  If bacterial, take antibiotics, cough medicines, voice rest, avoid irritants like smoke.

(5) Pneumonia :

• Cause : Bacteria, viruses, mycoplasma
• Symptoms : Filling of air spaces of alveoli with fluid containing dead WBCs chest pain, shortness of breath, blood in mucous.
• Treatment : Consult physician immediately, antibiotics, cough medicines, stay warm

 (6) Asthma :

• Cause : Allergy to foreign substances like pollen, dust, certain food, food additives, animal dander, etc.
• Symptoms : Narrowing and inflammation of bronchi, bronchospasm, periodic wheezing, difficulty in breathing.
• Treatment : Use of inhalants to open passage ways, avoid irritants

(7) Occupational respiratory disorders silicosis, asbestosis :

• Cause : Long term exposure to silica and asbestos dust in the mining industry.
• Symptoms : Irritation, fibrosis causing inflammation.
• Treatment : Protective mask and gear during work.

Treatment of respiratory disorders is by taking suitable antibiotics, inhalants, vaporizers and cough medicines. Also quitting smoking, using preventive masks and staying away from polluted air is too remedy against these disorders.

• Artificial ventilation : Method of induced breathing in a person who is unable to breathe is given artificial ventilation.
• Ventilator : A machine supporting breathing when normal breathing fails.

Circulation in animals :

• Transportation by diffusion and active transport is suitable in extremely small organisms.
• Intracellular transport by cyclosis is shown by almost all living organisms e.g. Paramoecium, Amoeba, root hair cells of many plants and WBCs in animals.
• Extracellular transport : In this transport water or body fluid is circulated through body cavities as in sponges and coelenterates or moved around the viscera by contraction of body wall and muscles as in roundworms or parenchymal circulation, viz. flatworms.

(a) Single circulation : In fishes heart shows single circulation as blood passes only once through heart during one cardiac cycle.

Deoxygenated blood is pumped from heart towards gills, where it undergoes oxygenation. This oxygenated blood moves towards various body parts, gets deoxygenated and returns back to heart for next cycle.

(b) Double circulation : Human heart shows double circulation as blood passes twice through the heart during one cardiac cycle.

• The blood follows two routes, viz. pulmonary and systemic.
• Pulmonary circulation is the circulation between the heart and the lungs. The course of blood during pulmonary circulation is from the right ventricle (by pulmonary trunk) to the left atrium (by two pairs of pulmonary veins) of heart through lungs.
• Systemic circulation is the circulation between the heart and the body organs (except lungs). The course of blood during systemic circulation is from left ventricle (by systemic aorta) to all body organs and from the body back to right atrium (by vena cavae).
• Coronary circulation is circulation to the cardiac muscles of the heart. Coronary arteries supply oxygenated blood whereas coronary veins join to form coronary sinus and collect deoxygenated blood. This sinus opens into the right atrium.

Red blood corpuscles / erythrocytes :

• Circular, biconcave, enucleated cells of about 7 /mm in diameter and 2.5 /mm in thickness.
• RBC count is about 5.1 to 5.8 million RBCs/ cu mm in male and 4.3 to 5.2 million/cu mm in female. The average life span of RBC is about 120 days.
• Erythropoiesis is formation of RBCs. It occurs in liver and spleen in foetus and in red bone marrow in adults.
• The old RBCs are destroyed in liver and spleen.
• Polycythemia is increase while erythrocytopenia is decrease in number of RBCs.
• RBCs contain respiratory pigment called haemoglobin which helps in transport of oxygen and carbon dioxide.
• The normal haemoglobin content in adult male is 14 — 17 gm/100 ml of blood and 13 - 15 gm/100 ml of blood in adult female.
• Less amount of haemoglobin leads to anaemia.
• RBCs transport oxygen from lungs to tissues and carbon dioxide from tissues to lungs. They maintain blood pH as haemoglobin acts as a buffer. They also maintain the viscosity of the blood.
• RBCs also contains an enzyme, carbonic anhydrase.
• The haematocrit is the ratio of the volume of RBCs to total blood volume of blood. Its Value is different in men and women.

White blood corpuscles/Leucocytes :

• Leucocytes are colourless, nucleated, amoeboid and phagocytic cells.
• They show diapedesis, i.e. squeezing out of blood capillaries by amoeboid movement.
• The size is about 8 to 15 um.
• Total WBC count is 5000 to 11000 WBCs/ cu mm of blood.
• The average life span of WBCs is about 3 to 4 days.
• Leucopoiesis or formation of WBCs. It occurs in red bone marrow, spleen, lymph nodes, tonsils, thymus and Payer’s patches.
• Leucocytosis is increase while leucopenia is decrease in the number of WBCs.
• Leukaemia or blood cancer is a pathological increase in number of WBCs.
• The dead WBCs are destroyed by phagocytosis in blood, liver and lymph nodes.
• Leucocytes are of two types, viz., granulocytes and agranulocytes.
• Granulocytes are of three types, viz. neutrophils, eosinophils and basophils.
• Agranulocytes are of two types, viz. monocytes and lymphocytes.

Characteristics of Different Types of Leucocytes :

Granulocytes : Granulocytes are cells with granular cytoplasm and lobed nucleus.

Based on their staining properties and shape of nucleus, they are of three types, viz. neutrophils, eosinophils and basophils.

(I) Neutrophils :

• In neutrophils, the cytoplasmic granules take up neutral stains.
• Their nucleus is three to five lobed.
• It may undergo changes in structure hence they are called polymorphonuclear leucocytes or polymorphs.
• Neutrophils are about 70% of total WBCs.
• They are phagocytic in function and engulf microorganisms.

(II) Eosinophils or acidophils :

• Cytoplasmic granules of eosinophils take up acidic dyes such as eosin. They have bilobed nucleus.
• Eosinophils are about 3% of total WBCs.
• They are non-phagocytic in nature.
• Their number increases (i.e. eosinophilia) during allergic conditions.
• They have antihistamine property

(III) Basophils :

• The cytoplasmic granules of basophils take up basic stains such as methylene blue.
• They have twisted nucleus.
• In size, they are smallest and constitute about 0.5% of total WBCs.
• They too are non-phagocytic.
• Their function is to release heparin which acts as an anticoagulant and histamine that is involved in inflammatory and allergic reaction.

Agranulocytes : There are two types of agranulocytes, viz. monocytes and lymphocytes. Agranulocytes do not show cytoplasmic granules and their nucleus is not lobed. They are of two types, viz. lymphocytes and monocytes.

(I) Lymphocytes :

• Agranulocytes with a large round nucleus are called lymphocyte.
• They are about 30% of total WBCs.
• Agranulocytes are responsible for immune response of the body by producing antibodies.

(II) Monocytes :

• Largest of all WBCs having large kidney shaped nucleus are monocytes. They are about 5% of total WBCs.
• They are phagocytic in function.
• They can differentiate into macrophages for engulfing microorganisms and removing cell debris. Hence they are also called scavengers.
• At the site of infections they are seen in more enlarged form.

The event that take place during blood clotting are as follows :

• Release of thromboplastin from extrinsic source in tissue and intrinsic source in plasma at injured site through a step-Wise (cascade process) process.
• Formation of enzyme prothrombinase in the blood.
• Conversion of prothrombin into thrombin by prothrombinase.
• Conversion of fibrinogen into fibrin by thrombin.
• Formation of mesh by the fibrin fibres forming the clot.
• The normal clotting time is 2 to 8 minutes.