The Respiratory System Chapter 18

Operations Pulmonary ventilation External respiration Moving air in & out External respiration Gas exchange between alveoli & blood Internal respiration Gas exchange between blood & cells Helps pH control

Anatomical Components Upper respiratory tract nose, pharynx Lower Respiratory System Trachea, larynx & bronchi & lungs Conducting zone = tubing Respiratory Zone= Gas exchange Bronchioles, alveolar sacs & alveoli

Figure 18.1

Nose Nose: external nares nasal cavity internal nares Nasal septum splits in two Nasal conchae swirl air over mucus membrane Designed to: Filter, Warm, Humidify Trap dust and infectious agents Detect olfactory stimuli Modify vocal sounds

Pharynx Funnel shaped tube from internal nares to larynx = “throat” Upper = naso pharynx Middle = oropharynx Between uvula & top of epiglottis lower = laryngeal pharynx Connects with both esophagus & larynx Thus both air & food & drink

Figure 18.2

Larynx Short tube of cartilage Thyroid cartilage- anterior = “Adam's apple” Epiglottis – upper leaf-shaped piece During swallowing larynx moves up and epiglottis covers opening to trachea Cricoid cartilage- forms inferior wall Paired arytenoids- above cricoid attach to vocal cords & pharyngeal muscles

Figure 18.3

Voice Production Mucous membrane of larynx  two pairs of folds Upper = false vocal cords Lower = true vocal cords Contain elastic ligaments stretched between cartilage Move out into air way and vibrate Pitch adjusted by tension and diameter of ligaments

Trachea Trachea- larynx  upper part of T5 vertebra R. & L. primary bronchus Lined with pseudostratified ciliated mucous membrane  dust protection – move toward pharynx C-shaped cartilage rings keep lumen open

Bronchi & Bronchioles Bronchi also contain cartilage rings Primary bronchi enter the lungs Blood vessels, lymphatic vessels & nerves enter lungs with bronchi In lungs branch secondary bronchi one for each lobe of lung  tertiary bronchi  terminal bronchi Smaller bronchi have less cartilage and more smooth muscle ANS can adjust diameter = resistance to flow

Lungs Two organs (R. & L) Surrounded by pleural membrane Parietal pleura attached to diaphragm & thoracic wall Visceral pleura attached to lungs Between is pleural cavity filled with fluid Broad bottom = base; Pointy top = apex Right lung has 3 lobes Left lung has 3 lobes & cardiac notch

Lung Lobes Divided in lobules fed by tertiary bronchus Further divisions terminal bronchiole  respiratory bronchiole Lined with non-ciliated cuboidal epithelium  alveolar ducts  alveolar sacs 

Figure 18.4

Alveoli Cup-shaped out pouch of sac Lined with thin alveolar cells (simple squamous) Scattered surfactant secreting cells Lowers surface tension & humidifies Alveolar macrophages- “cleaners” Gases diffuse across combined epithelia of alveolus & capillary Combination called: Respiratory Membrane

Figure 18.5

Figure 18.6

Pulmonary Ventilation Air flows between atmosphere & lungs due to difference in pressure Caused by respiratory muscles Inhalation: diaphragm & external intercostals Diaphragm contracts  lung volume Lung moves due to seal between parietal & visceral plura

Exhalation Resting exhalation due to muscle relaxation= passive process Diaphragm rises & ribs fall   lung volume Can be active using internal intercostals & abdominal muscles Push diaphragm up & pull ribs in  More  lung volume

Figure 18.7a

Figure 18.7b

Pressure Changes  lung volume   alveolar pressure Atmospheric pressure is constant Atmospheric > alveolar inhalation During exhalation   lung rises Alveolar> Atmospheric  exhalation

Figure 18.8

Air Flow Terms Frequency (f) = breaths per minute Normal ~12 breaths per min Tidal volume (TV) = volume moved in one breath Normal ~ 500 ml Minute Ventilation (MV) = f x TV ~ 70% of TV reaches alveoli (350 ml) Only this involved in gas exchange 30% in airways = Anatomic Dead Space

Lung Volumes Inspiration beyond resting = Inspiratory reserve volume Expiration beyond resting (active) = Expiratory reserve volume Air left after a maximum expiration = residual volume

Lung Capacities Inspiratory capacity= Functional residual capacity = TV + inspiratory reserve Functional residual capacity = Residual volume + expiratory reserve Vital capacity (VC) = Expiratory reserve + TV + Inspiratory reserve Total lung capacity = VC + residual

Figure 18.9

Breathing Patterns Eupnea = normal breathing Highly variable in pattern Special modifications for speech and emotional responses Also variations fro coughing & sneezing to clear airways See table 18.1

Nature of Air Mixture of gases (N2, O2,, CO2, H2O & others) Each gas has own partial pressure (Px) Each gas diffuses down partial pressure gradient Total = sum of partial pressures = atmospheric pressure

Pulmonary Gas Exchange: External Respiration O2 diffuses from air (PO2 ~105mm Hg)  incoming blood (PO2 ~40mm Hg) Continues until equilibrium (PO2 ~105mm Hg) Some unexchanged mixture in out flow so Arterial blood is ~100 mmHg Meanwhile blood (PCO2 ~45) diffuses to alveolar air (PCO2 ~40) Again to equilibrium

Systemic Gas Exchange: Internal Respiration Occurs throughout body O2 diffuses from blood to cells PO2 lower in cells because of use Meanwhile CO2 diffuses in opposite direction

Figure 18.10

Transport of Oxygen O2 dissolves poorly 98.5% bound to hemoglobin in RBCs Binding depends on PO2 High at lung and lower at tissue PO2s Tissue release of O2 increased by: High CO2 Acidity Higher temperatures

Transport of Carbon Dioxide As comes in to blood from cells Some dissolved (7%) Bound to proteins including Hemoglobin (23%) Becomes bicarbonate ions (70%) CO2 + H2O <=> H+ + HCO3- Process reverses at lungs

Figure 18.11

Control of Respiration Medullary respiratory area in medulla Contains both inspiratory & expiratory areas Quiet breathing: inspiratory area nerve signals to inspiratory muscles for ~2 sec inspiration Then becomes inactive & muscles relax Expiration Expiratory centre active only during forceful breathing Area in pons adjusts length of inspiratory stimulation

Figure 18.12a

Figure 18.12b

Regulation of Respiratory Center Cortical input: voluntary adjustment of patterns Protection & talking Chemoreceptor input will override breath-hold Chemoreceptor input Central receptors in medulla Peripheral receptors in arch of aorta respond to increased H+ or PCO2 increased ventilation Thus negative feedback loop to maintain blood & brain pH Significant falls in PO2 also stimulates breathing

Figure 18.13

Other Regulatory Factors Limbic system- anticipation of activity or emotion can stimulate Proprioception stimulates on start of activity Temperature  warming increases Pain- Sudden pain  apnea Prolonged somatic pain can increase rate Airway irritation cough or sneeze Inflation reflex- bronchi wall stretch receptors inhibit inspiration Prevents overinflation

Aging Everything becomes less elastic  Decrease in Vital capacity Can decrease blood O2 level Decreased exercise capacity Decreased macrophage activity Increased susceptibility to pulmonary disease