Gaseous exchange in human

student of biological sciences at karakoram international university gilgit pakistan

1. Gaseous Exchange In Human Zakia khatoon Syyeda urooj Nelofar Hanif Diya Fatima Kainat Abbas

2. Introduction Oxygen is needed for aerobic respiration CO₂ is produce as a result of aerobic respiration. Exchange of these gases with the environment. Need Respiratory Surface

3. Respiratory Surfaces Thin Diffusion distance Speed Moist Gases dissolved in solution Large SA to volume ratio Energy demands

4. Organs of the Respiratory system Nose Pharynx Larynx Trachea Bronchi Lungs – alveoli Figure 13.1

5. Function of the Respiratory System Oversees gas exchanges between the blood and external environment Exchange of gasses takes place within the alveoli Passageways to the lungs purify, warm, and humidify the incoming air

6. The Nose The only externally visible part of the respiratory system Air enters the nose through the external nares (nostrils) The interior of the nose consists of a nasal cavity divided by a nasal septum

7. Anatomy of the Nasal Cavity Lateral walls have projections called conchae Increases surface area Increases air turbulence within the nasal cavity The nasal cavity is separated from the oral cavity by the palate Anterior hard palate (bone) Posterior soft palate (muscle )

8. Anatomy of the Nasal Cavity Olfactory receptors are located in the mucosa on the superior surface The rest of the cavity is lined with respiratory mucosa Moistens air Traps incoming foreign particles Paranasal sinuses Cavities within bones surrounding the nasal cavity

9. Pharynx (Throat) Muscular passage from nasal cavity to larynx Three regions of the pharynx Nasopharynx – superior region behind nasal cavity Oropharynx – middle region behind mouth Laryngopharynx – inferior region attached to larynx The oropharynx and laryngopharynx are common passageways for air and food

10. Structures of the Pharynx Auditory tubes enter the nasopharynx Tonsils of the pharynx Pharyngeal tonsil (adenoids) in the nasopharynx Palatine tonsils in the oropharynx Lingual tonsils at the base of the tongue

11. Larynx (Voice Box) Routes air and food into proper channels Plays a role in speech Made of eight rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage (epiglottis) Vocal cords - vibrate with expelled air to create sound (speech)

12. Structures of the Larynx Thyroid cartilage Largest hyaline cartilage Protrudes anteriorly (Adam’s apple) Epiglottis Superior opening of the larynx Routes food to the larynx and air toward the trachea Glottis opening between vocal cords

13. Trachea (Windpipe) Connects larynx with bronchi Lined with ciliated mucosa Beat continuously in the opposite direction of incoming air Expel mucus loaded with dust and other debris away from lungs Walls are reinforced with C-shaped hyaline cartilage

14. Primary Bronchi Formed by division of the trachea Enters the lung at the hilus (medial depression) Right bronchus is wider, shorter, and straighter than left Bronchi subdivide into smaller and smaller branches

15. Bronchioles Smallest branches of the bronchi All but the smallest branches have reinforcing cartilage Terminal bronchioles end in alveoli (grape like sacs). Figure 13.5a

16. Lungs Ocupy most of the thoracic cavity Apex is near the clavicle (superior portion) Each lung is divided into lobes by fissures Left lung – two lobes Right lung – three lobes

17. Lungs Figure 13.4b

18. Organs in the Respiratory System STRUCTURE FUNCTION nose / nasal cavity  warms, moistens, & filters air as it is inhaled pharynx (throat)  passageway for air, leads to trachea larynx  the voice box, where vocal chords are located trachea (windpipe)  keeps the windpipe "open"  trachea is lined with fine hairs called cilia which filter air before it reaches the lungs bronchi  two branches at the end of the trachea, each lead to a lung bronchioles  a network of smaller branches leading from the bronchi into the lung tissue & ultimately to air sacs alveoli  the functional respiratory units in the lung where gases are exchanged

19. Respiratory Disruptions Smoking Inhibit cilia movement causes ‘smoker’s cough’ Thicken bronchioles and reduce elasticity Alveoli rupture Stopping allows cilia and alveoli damage to reverse Premature birth (37 weeks or less) Surfactant production incomplete Keeps alveoli from collapsing Each breath requires large effort Emphysema Bronchi swell, tearing alveoli Reduced SA for gas exchange Pneumonia Fluid in alveoli Bronchitis inflames of bronchioles

20. Ventilation/Breathing The movement of air between the environment and the lungs via inhalation and exhalation. Mechanical ventilation : using artificial methods to assist breathing Medical ventilator : a mechanical ventilator, a machine designed to move breathable air into and out of the lungs.

21. Control of Breathing Respiratory centre Chemoreceptor pCO 2

22. Mechanism of Breathing ( Pulmonary Ventilation) Mechanical process Depends on volume changes in the thoracic cavity Volume changes lead to pressure changes, which lead to equalize pressure of flow of gases 2 phases Inspiration – flow of air into lung Expiration – air leaving lung

23. Organs Involved Diaphragm Intercostals' muscles Ribcage

24. INSPIRATION Active process Quiet inspiration Volume of ribcage increases pressure will drop air flow into the lungs.

25. . Active process Diaphragms contracts and flattens Thoracic cavity enlarges External intercostals muscles contract The ribs move up and outward and enlarges the thoracic cavity Total volume of the thoracic cavity increases Decrease in air pressure The elastic lungs expand and air flows into the lungs

26. Expiration Passive process dependent up on natural lung elasticity As muscles relax, air is pushed out of the lungs Forced expiration can occur mostly by contracting internal intercostal muscles to depress the rib cage

27. Expiration Figure 13.7b

28. Measures of Pulmonary Ventilation Respiratory volumes – values determined by using a spirometer Tidal Volume (TV ) – amount of air inhaled or exhaled with each breath under resting conditions Inspiratory Reserve Volume (IRV) – amount of air that can be inhaled during forced breathing in addition to resting tidal volume Expiratory Reserve Volume (ERV) – amount of air that can be exhaled during forced breathing in addition to tidal volume Residual Volume (RV) – Amount of air remaining in the lungs after a forced exhalation.

29. Transport of Gases The exchange of gases (O₂ & CO₂) between the alveoli & the blood occurs by simple diffusion. O₂ diffusing from the alveoli into the blood & CO₂ from the blood into the alveoli. Diffusion requires a concentration gradient. So, the concentration (or pressure) of O₂ in the alveoli must be kept at a higher level than in the blood & the concentration (or pressure) of CO₂ in the alveoli must be kept at a lower lever than in the blood.

30. Partial Pressure The partial pressure exerted by each gas in a mixture equals the total pressure times the fractional composition of the gas in the mixture. Total atmospheric pressure (at sea level) is about 760 mm Hg and, further, that air is about 21% oxygen, then the partial pressure of oxygen in the air is 0.21 times 760 mm Hg or 160 mm Hg.

31. level of the partial pressure of main gases in the human body Partial Pressures of O2 and CO2 in the body (normal, resting conditions): Alveoli PO2 = 100 mm Hg PCO2 = 40 mm Hg Alveolar capillaries Entering the alveolar capillaries PO2 = 40 mm Hg PCO2 = 45 mm Hg

32. While in the alveolar capillaries, the diffusion of gasses occurs: oxygen diffuses from the alveoli into the blood & carbon dioxide from the blood into the alveoli. Leaving the alveolar capillaries PO2 = 100 mm Hg PCO2 = 40 mm Hg Blood leaving the alveolar capillaries returns to the left atrium & is pumped by the left ventricle into the systemic circulation. This blood travels through arteries & arterioles and into the systemic, or body, capillaries. Entering the systemic capillaries PO2 = 100 mm Hg PCO2 = 40 mm Hg Body cells (resting conditions) PO2 = 40 mm Hg PCO2 = 45 mm Hg

33. Because of the differences in partial pressures of oxygen & carbon dioxide in the systemic capillaries & the body cells, oxygen diffuses from the blood & into the cells, while carbon dioxide diffuses from the cells into the blood. Leaving the systemic capillaries PO2 = 40 mm Hg PCO2 = 45 mm Hg Blood leaving the systemic capillaries returns to the heart (right atrium) via venules & veins (and no gas exchange occurs while blood is in venules & veins). This blood is then pumped to the lungs (and the alveolar capillaries) by the right ventricle.

34. Transport of CO₂ In blood Three main ways to transport CO₂ in blood from tissues to lungs As bicarbonate ions As carboxyhaemoglobin As dissolved CO₂ in plasma

35. as bicarbonate ions Most of the carbon dioxide approximately 70% is carried in blood as bicarbonate ions. CO₂ entering blood cells reacts with water and form carbonic acid in the presence of carbonic anhydrase. Carbonic acid is unstable and splits into H+ and HCO₃⁻ H+ combine with H₄bO ₂ that dissociates O₂ from Hb and diffuse into cells for aerobic respiration. The bicarbonate ion then diffuses outside the RBC in the plasma and combines with Sodium ions to from Sodium bicarbonate (NaHCO3).

36. Cont.. Loss of bicarbonate ions from RBC causes positive charge inside RBC which is balanced by diffusion of chloride (Cl-) ion from plasma into the RBC. This exchange of Cl- ion and HCO3- ion between plasma and RBC is known as chloride shift. This phenomenon of chloride shift maintains the electrical neutrality of cell.

37. O₂ hemoglobin dissociation curve The following four factors decrease the affinity, or strength of attraction, of Hb for O  2  and result in a shift of the O  2 ‐Hb dissociation curve to the right Increase in temperature. Increase in partial pressure of CO  2  (pCO  2 ). The effect of CO2 on Oxygen dissociation curve is known as Bohr effect. Increase in acidity (decrease in pH).

38. It has been found that increase in concentration of CO2 decreases the amount of oxyhaemoglobin formation. according to Bohr effect, for any particular partial pressure of Oxygen, the affinity of Haemoglobin toward Oxygen decreases and favors dissociation of oxyhaemoglobin when the partial pressure of carbondioxide increases. It means, higher CO2 concentration causes the dissociation of HbO2 releasing free O2. Increase in PCO2 shifts the O2 dissociation curve downwards. Higher PCO2 lowers the affinity of hemoglobin for O2.

39. as carbaminohaemoglobin (23%) some CO2 combines with Haemoglobin to form carbaminohaemoglobin in RBCs. CO2 +  NHbNH2————–HbNH.COOH (carbaminohaemoglobin). finally, CO2 are carried to lungs and expelled out by expiration process of breathing

40. As dissolved CO₂ in plasma some CO ₂ dissolved in the plasma to form carbonic acid carbon dioxide mixed with water of blood plasma to form carbonic acid. CO ₂ + H ₂ O——————H ₂ CO ₃

41. CO₂ Poisoning/ hypercapnia or hypercarbia Causes: breathing volcanic gas. rebreathing exhaled air (e.g., from breathing air in a bag, sleeping in a sealed tent, sleeping with a blanket over one's head)  scuba diving, hypoventilation, lung diseases. breathing in confined spaces or areas with poor air circulation, such as a sealed room, a tunnel, cargo. Symptoms: high blood pressure, flushed skin, headache and twitching muscles. At severe conditions panic, irregular heartbeat, hallucinations, vomited and potentially unconsciousness or even death.

42. Respiratory disorders Pre-term birth can lead to infants with under-developed lungs . Smoking and air pollution are two common causes of respiratory problems . Diorders include: Obstructive conditions (e.g., emphysema, bronchitis, asthma attacks) Infectious , environmental: (e.g., pneumonia, tuberculosis, asbestosis, particulate pollutants):

43. Cont… Common Respiratory Disorders Include: Swine flu , also called  swine influenza, hog flu , or  pig flu , a respiratory disease of pigs that is caused by an influenza virus. Chronic Bronchitis:  - Any irritant reaching the bronchi and bronchioles will stimulate an increased secretion of mucus. In chronic bronchitis the air passages become clogged with mucus, and this leads to a persistent cough.

44. Cont… Emphysema: The delicate walls of the alveoli break down, reducing the gas exchange area of the lungs. The condition develops slowly and is seldom a direct cause of death. Asthma: - Periodic constriction of the bronchi and bronchioles makes it more difficult to breathe. Pneumonia  :- An infection of the alveoli. It can be caused by many kinds of both bacteria and viruses. Tissue fluids accumulate in the alveoli reducing the surface area exposed to air. If enough alveoli are affected, the patient may need supplemental oxygen.