Respiratory physiology

Functions of respiratory system  Respiratory function.  Protective functions.

Functions of the Respiratory System: Exchange O 2 Exchange O 2 Air to blood Air to blood Blood to cells Blood to cells Exchange CO 2 Exchange CO 2 Cells to blood Cells to blood Blood to air Blood to air Regulate blood pH Regulate blood pH Vocalizations Vocalizations Protect alveoli Protect alveoli Figure 17-1: Overview of external and cellular respiration

Protective functions A. Air conditioning. B. Trapping & elimination of foreign particles. C. Protective reflexes:  Cough reflex.  Sneeze reflex.

Respiration & Ventilation Four Stages: 1. Pulmonary ventilation; air into lungs 2. External respiration; gas exchange from lungs to blood 3. Internal respiration; exchange of gas from blood to cells 4. Cellular respiration; utilization of oxygen by cells to produce energy

Respiratory System Divisions

Airways

Respiratory Airways (Respiratory tract or Air passages) Anatomically: Upper respiratory tract. Upper respiratory tract. Lower respiratory tract. Lower respiratory tract.Functionally: Conducting zone (no gas exchange = dead space). Conducting zone (no gas exchange = dead space). Respiratory zone (Gas exchange). Respiratory zone (Gas exchange).

Nasal Cavity and Pharynx

Nose and Pharynx Nose Nose External nose External nose Nasal cavity Nasal cavity Functions Functions Passageway for air Passageway for air Cleans the air Cleans the air Humidifies, warms air Humidifies, warms air Smell Smell Along with paranasal sinuses are resonating chambers for speech Along with paranasal sinuses are resonating chambers for speech Pharynx Common opening for digestive and respiratory systems Three regions Nasopharynx Oropharynx Laryngopharynx

Functions Maintain an open passageway for air movement Epiglottis and vestibular folds prevent swallowed material from moving into larynx Vocal folds are primary source of sound productionLarynx

Respiratory zone Respiratory bronchioles, alveolar ducts, atria, alveolar sacs & alveoli. Respiratory bronchioles, alveolar ducts, atria, alveolar sacs & alveoli. Gas exchange. Gas exchange.

Conducting zone Nose, pharynx, larynx, trachea, bronchi, bronchioles & terminal bronchioles. Nose, pharynx, larynx, trachea, bronchi, bronchioles & terminal bronchioles. Cartilaginous rings, smooth muscles, columnar ciliated epithelium (escalator) & mucous glands. Cartilaginous rings, smooth muscles, columnar ciliated epithelium (escalator) & mucous glands. Warms and humidifies inspired air. Warms and humidifies inspired air. Filters and cleans: Filters and cleans: Mucus secreted to trap particles in the inspired air. Mucus secreted to trap particles in the inspired air. Mucus moved by cilia to be expectorated Mucus moved by cilia to be expectorated

Pleura 2 layers (visceral & parietal). 2 layers (visceral & parietal). Thin layer of fluid (lubricant). Thin layer of fluid (lubricant). Pressure difference across the wall of the lung to expand lung Pressure difference across the wall of the lung to expand lung Positive air pressure = MORE than 760 mmHg Positive air pressure = MORE than 760 mmHg Intrapleural pressure is the pressure within the pleural sac which surrounds the lung Intrapleural pressure is the pressure within the pleural sac which surrounds the lung Intrapulmonary pressure is the pressure within the alveoli of the lung itself Intrapulmonary pressure is the pressure within the alveoli of the lung itself

Pleura Pleural fluid produced by pleural membranes Acts as lubricant Helps hold parietal and visceral pleural membranes together

Breathing rate is breaths / minute at rest, at maximum exercise in adults Mechanical process that moves air in and out of the lungs. [O 2 ] of air is higher in the lungs than in the blood, O 2 diffuses from air to the blood. C0 2 moves from the blood to the air by diffusing down its concentration gradient. Gas exchange occurs entirely by diffusion: Diffusion is rapid because of the large surface area Breathing rate is breaths / minute at rest, at maximum exercise in adults Ventilation

Ventilation Movement of air into and out of lungs Movement of air into and out of lungs Air moves from area of higher pressure to area of lower pressure Air moves from area of higher pressure to area of lower pressure Pressure is inversely related to volume Pressure is inversely related to volume Movement of air into and out of alveoli Movement of air into and out of alveoli Inhalation: The lungs inflate with air, bringing oxygen into the body Inhalation: The lungs inflate with air, bringing oxygen into the body Exhalation: The lungs let go of air, releasing carbon dioxide out into the environment Exhalation: The lungs let go of air, releasing carbon dioxide out into the environment

Inspiration Active process. Active process. Contraction of the inspiratory muscles. Contraction of the inspiratory muscles. Diaphragm (75%) & External intercostal muscles. Diaphragm (75%) & External intercostal muscles.

Inspiration

Mechanism of inspiration 1. Contraction of the inspiratory muscles. 2.  Chest dimensions. 3.  IPP. 4. Lungs expansion. 5.  Intrapulmonary pressure. 6. Rush of 500 ml air into the lungs ( Inflation).

Expiration

Expiration A passive process A passive process No muscle contraction No muscle contraction Only relaxation of inspiratory muscles Only relaxation of inspiratory muscles

Mechanism of Expiration 1. Relaxation of the inspiratory muscles. 2.  Chest dimensions. 3.  IPP. 4. Lungs recoil. 5.  Intrapulmonary pressure. 6. Rush of 500 ml air outside the lungs ( Deflation).

Inspirato ry muscles contract Thoraci c cavity size increase I.Pulm on volume increas e Air Rush into lung I.P Decreas e than atmosph ric Inspiratory muscles Relax Thoracic cavity size Decrease I.Pulmon volume decrease Air Rush out the lung I.P inecrease than atmosphri c expiratory muscles Contract Inspiration Expiration

W Paul Segars Johns Hopkins

Alveoli 300 million. 300 million m m micron. 0.2 micron. Single layer of flat epithelium cells (Type I). Single layer of flat epithelium cells (Type I). Granular pneumocytes (Type II) → Surfactant. Granular pneumocytes (Type II) → Surfactant. Lined by thin film of fluid (surface tension ). Lined by thin film of fluid (surface tension ). Surfactant decreases the surface tension of alveolar fluid Surfactant decreases the surface tension of alveolar fluid Pulmonary Alveolar macrophages. Pulmonary Alveolar macrophages. Pulmonary Interstitial tissue (elastin & collagen). Pulmonary Interstitial tissue (elastin & collagen). Surrounded by extensive network of capillaries. Surrounded by extensive network of capillaries.

Alveolar structure Type I cells  gas exchange Type I cells  gas exchange Type II cells  secrete surfactant (lipoproteins)  decrease surface tension  allowing for easier alveoli inflation Type II cells  secrete surfactant (lipoproteins)  decrease surface tension  allowing for easier alveoli inflation Surfactants start to be secreted by the 7 th month of pregnancy  risk of lung disease in premature babies Surfactants start to be secreted by the 7 th month of pregnancy  risk of lung disease in premature babies Presence of macrophages in alveoli Presence of macrophages in alveoli

Anatomical Dead Space No gas exchange (dead space). No gas exchange (dead space). Not all of the inspired air reached the alveoli. Not all of the inspired air reached the alveoli. As fresh air is inhaled it is mixed with air in anatomical dead space. As fresh air is inhaled it is mixed with air in anatomical dead space. Conducting zone and alveoli where [0 2 ] is lower than normal and [C0 2 ] is higher than normal. Conducting zone and alveoli where [0 2 ] is lower than normal and [C0 2 ] is higher than normal. Alveolar ventilation = F x (TV- DS). Alveolar ventilation = F x (TV- DS). F = frequency (breaths/min.). F = frequency (breaths/min.). TV = tidal volume. TV = tidal volume. DS = dead space. DS = dead space.

Gas exchange at Tissue levels HOW THE BODY GET OXYGEN AND GET RIDE OF CO2 DURING RESPIRATION

Pulmonary Capillary Gas exchange at Lung levels

Co2 transport Some fraction of carbon dioxide is dissolved and carried in blood. Some reacts reversibly with Hb to form carbamino Hb. CO2 + Hb ↔ HbC02 Some carbon dioxide is converted to bicarbonate. Carbonic CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+ anhydrase The enzyme, carbonic anyhydrase, is present in erythrocytes where the reaction takes place after which the bicarbonate moves out into the plasma.

Minute and Alveolar Ventilation 1.Tidal volume:Volume of air inspired or expired during a normal inspiration or expiration=500 mL 2.Respiratory rate or frequency: Number of breaths taken per minute= Minute ventilation: Total amount of air moved into and out of respiratory system per minute =500x12=6 L 4.Anatomic dead space: Part of respiratory system where gas exchange does not take place=150 mL 5.Alveolar ventilation: How much air per minute enters the parts of the respiratory system in which gas exchange takes place=

Hypoxia O 2 deficiency at the tissue level Deficiency in either the delivery or utilization of oxygen at the tissue level, which can lead to changes in function, metabolism and even structure of the body 1) Hypoxic hypoxia 3) Stagnant hypoxia 2) Anemic hypoxia 4) Histotoxic hypoxia

Hypoxia 1.Shortness of breath 2.Restlessness 3.Headache 4.Nausea 5.Fatigue 6. Tachycardia 7. Tachypnea and Hyperpnea 8. Cyanosis 9. Coma 10. Death

I.1. Hypoxic hypoxia II. Anemic hypoxia III.3. Stagnant hypoxia IV.4. Histotoxic hypoxia types of hypoxia

Hypoxic hypoxia: It is the hypoxia in which arterial PO 2 is reduced Causes: 1. Decreased O 2 tension in the atmosphere: high altitude. 2. Defective pulmonary ventilation 3. Defective gas exchange 4. Venous-to-arterial shunts. Anemic hypoxia This is due to reduction of the amount of hemoglobin available to carry O 2. Causes: 1. All types of anemia 2. Carbon monoxide (CO) poisoning

Stagnant hypoxia: This is the hypoxia in which the blood flow to the tissues is slow, O 2 delivered to the tissues is not adequate despite a normal PO 2 and hemoglobin concentration Causes: 1. Hypotension 2. Heart failure. 2. Polycythemia. 3. V.C. on exposure to cold (localized). Histotoxic hypoxia This is the hypoxia in which tissue is unable to use O 2 due to inhibition of enzyme responsible for internal respiration. Causes: Causes: 1. Cyanide poisoning: the most common cause 2. Alcohol and barbiturate which prevent dehydrogenase enzyme.