Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Respiratory System 1 Recap 2 Pressure in Occluded Alveoli Caused by Surface Tension • If the air passages leading from the alveoli of the lungs are blocked, the surface tension in the alveoli tends to collapse the alveoli→ positive pressure in the alveoli → attempting to push the air out • formula: Pressure=2 X Surface Tension Radius of Alveolus • respiratory distress syndrome of the newborn 3 Pulmonary Volumes & Pulmonary Capacities 2 1 2 4 1 3 3 4 4 Values in adult male • All pulmonary volumes and capacities are about 20 to 25 per cent less in women • greater in large and athletic people than in small and asthenic people. 5 Lecture 4 6 Measurement Value Calculation Description Total lung capacity (TLC) = 5.8 L = IRV + TV + ERV + RV The volume of gas contained in the lung at the end of maximal inspiration. The total volume of the lung (i.e.: the volume of air in the lungs after maximum inspiration). Vital capacity (VC) = 4.8 L = IRV + TV + ERV The amount of air that can be forced out of the lungs after a maximal inspiration. Emphasis on completeness of expiration. The maximum volume of air that can be voluntarily moved in and out of the respiratory system Forced vital capacity (FVC) = 4.8 L measured The amount of air that can be maximally forced out of the lungs after a maximal inspiration. Emphasis on speed Tidal volume (TV) = 500 ml measured The amount of air breathed in or out during normal respiration. The volume of air an individual is normally breathing in and out. Residual volume (RV) = 1.2 L measured The amount of air left in the lungs after a maximal exhalation. The amount of air that is always in the lungs and can never be expired (i.e.: the amount of air that stays in the lungs after maximum expiration). = 1.1L measured The amount of additional air that can be breathed out after the end expiratory level of normal breathing. (At the end of a normal breath, the lungs contain the residual volume plus the expiratory reserve volume, or around 7 2.4 litres. If one then goes on and exhales as much as possible, only the residual volume of 1.2 litres remains). Expiratory reserve volume (ERV) Lung Volumes Q.Which of these can be measured with a spirometer ? Boundary Conditions TLC VT VOLUME ERV FRC RV RV TIME Answer : NONE 8 Helium Dilution Method • Determination of Functional Residual Capacity, Residual Volume, and Total Lung Capacity 9 Abbreviations and Symbols • • • • • • • • • • • Table 37-1 VT = tidal volume FRC = functional residual capacity ERV = expiratory reserve volume RV = residual volume IC = inspiratory capacity IRV = inspiratory reserve volume TLC = total lung capacity VC = vital capacity FEV1= Forced Expiratory Volume in 1st second FVC= Forced Vital Capacity 10 Minute Respiratory Volume • Respiratory Rate X Tidal Volume • total amount of new air moved into the respiratory passages each minute • 12 breaths per minute X 500 milliliters = 6 L/min 11 Alveolar Ventilation • The rate at which new air reaches gas exchange areas is called alveolar ventilation. • gas exchange areas: – where air is in proximity to the pulmonary blood – alveoli, alveolar sacs, alveolar ducts, and respiratory bronchioles. • importance of pulmonary ventilation – continually renew the air in the 12 "Dead Space" and Its Effect on Alveolar Ventilation • areas where gas exchange does not occur – nose, pharynx, and trachea, bronchi, large bronchioles • On expiration, the air in the dead space is expired first 13 Measurement of the Dead Space Volume • takes a deep breath of oxygen • expires through a rapidly recording nitrogen meter 14 Normal Dead Space Volume • 150 milliliters – ↑ slightly with age. • Anatomic Versus Physiologic Dead Space • nearly equal • nonfunctional alveoli: physiologic dead space may ↑ 15 Rate of Alveolar Ventilation • Alveolar ventilation per minute is the total volume of new air entering the alveoli and adjacent gas exchange areas each minute • = respiratory rate X amount of new air that enters these areas with each breath. • ṼA = Freq . (VT-VD) – – – – ṼA = volume of alveolar ventilation per minute Freq = frequency of respiration per minute VT = tidal volume VD = physiologic dead space volume – normal value • 12 × (500 - 150), or 4200 ml/min. • Alveolar ventilation is one of the major factors determining the concentrations of oxygen and carbon dioxide in the alveoli. 16 Functions of the Respiratory Passageways 17 Trachea, Bronchi, and Bronchioles 18 Function of Trachea, Bronchi, and Bronchioles 1.To keep Respiratory passageways open to allow easy passage of air to and from the alveoli i. Cartilages ii. Smooth Muscle (Relaxed) 2. Clear the Passageways: i. Mucus ii. Cilia 19 Smooth Muscle Smooth muscle↑ Downwards Cartilage Trachea Cartilage ↓ downwards Bronchi Bronchioles Less smooth Muscle Mainly Epithelium Terminal Bronchioles (Respiratory Bronchioles) Clinical: obstructive diseases: 1.excessive contraction of the smooth muscle 2. edema 3. mucus 20 Nervous Control of the Bronchiolar Musculature • Sympathetic: – Dilation of the Bronchioles – Direct control • relatively weak – norepinephrine and epinephrine • adrenal gland medulla – beta-adrenergic receptors V. Important • Parasympathetic – Constriction of the Bronchioles – vagus nerves – atropine • asthma • irritation of the epithelial membrane – Reflex Activation of parasympathetic nerves 21 Local Factors that Affect/Control Bronchiolar Musculature • Bronchiolar Constriction • histamine • slow reactive substance of anaphylaxis – mast cells • pollen in the air • allergic asthma 22 Cough Reflex • sensitive areas: – bronchi and trachea • light touch • larynx and carina (the point where the trachea divides into the bronchi) are especially sensitive – terminal bronchioles and even alveoli • corrosive chemical stimuli – sulfur dioxide gas – chlorine gas Contd…. 23 • Afferent nerve Cough Reflex Contd…. – Vagus • Medulla • automatic sequence – .5 liters of air are rapidly inspired – Epiglottis closes – Vocal cords shut tightly – Entrap the air within the lungs – Abdominal muscles contract forcefully – Other expiratory muscles, such as the internal intercostals, also contract forcefully – Lungs explodes outward – Velocities ranging from 75 to 100 miles per hour • Carries with it any foreign matter 24 Sneeze Reflex • much like the cough reflex • irritation in the nasal passageways • afferent impulses – fifth cranial nerve • • • • medulla reactions similar to those for the cough reflex uvula is depressed air pass rapidly through the nose 25