The Respiratory System Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display

Breath of Fresh Air Anatomy of respiratory system Ventilation Gas exchange and transport

Respiratory System What are some functions of the respiratory system? Respiration as a process – Ventilation – External and internal respiration – Cellular respiration

Anatomy Principal organs – Nose, pharynx, larynx, trachea, bronchi, and lungs Conducting division – Function only in airflow Respiratory division – Function in gas exchange

Organs of Respiratory System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nasal cavity Nostril Hard palate Larynx Trachea Right lung Posterior nasal aperture Soft palate Pharynx Epiglottis Esophagus Left lung Left main bronchus Lobar bronchus Segmental bronchus Pleural cavity Pleura (cut) Diaphragm Figure 22.1

The Nose Functions – Warms, cleanses, and humidifies inhaled air – Detects odors – Resonating chamber for voice Nose extends from nostrils (nares), to a pair of posterior openings called the posterior nasal apertures (choanae) Facial part is shaped by bone and hyaline cartilage – superior half nasal bones and maxillae – inferior half lateral and alar cartilages – ala nasi – flared portion at the lower end of nose shaped by alar cartilages and dense connective tissue

Anatomy of Nasal Region Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (b) Nasal bone Septal nasal cartilage Lateral cartilage Minor alar cartilages Major alar cartilages Dense connective tissue © The McGraw-Hill Companies/Joe DeGrandis, photographer Figure 22.2b

Nasal Cavity Nasal fossae – right and left halves of nasal cavity – Divided by nasal septum Composed of bone and cartilage – Perpendicular plate – Vomer – Septal cartilage – Roof and floor Ethmoid and sphenoid Hard palate

Nasal Cavity Vestibule – dilated chamber inside the nares – Stratified squamus epithelium – Vibrissae Nasal Conchae (turbinates) – superior, middle, inferior – Meatus Cleanses, warms, and humidifies air Epithelium of nasal cavity – Ciliated pseudostratified columnar with goblet cells Olfactory – cilia immobile Respiratory – cilia mobile Erectile tissue – venous plexus in inferior concha – Allows one side of the nasal cavity to recover from drying out by restricting airflow in that side – Changes sides once or twice per hour

Upper Respiratory Tract Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Frontal sinus Nasal conchae: Superior Middle Inferior Guard hairs Naris (nostril) Hard palate Upper lip Tongue Lower lip Mandible Larynx (b) Superior Middle Inferior Meatuses: Sphenoid sinus Posterior nasal aperture Pharyngeal tonsil Auditory tube Soft palate Uvula Palatine tonsil Lingual tonsil Epiglottis Vestibular fold Esophagus Trachea Vestibule Vocal cord Figure 22.3b

Pharynx Pharynx (throat) – a muscular funnel extending about 13 cm (5 in.) from the choanae to the larynx Three regions – Nasopharynx Posterior to nasal apertures and above soft palate Receives auditory tubes and contains pharyngeal tonsil 90  downward turn traps large particles (>10  m) Passes only air, lined by pseudostratified columnar epithelium – Oropharynx Space between soft palate and epiglottis Contains palatine tonsils – Laryngopharynx Epiglottis to cricoid cartilage Esophagus begins at that point Oropharynx and laryngopharynx pass air, food, and drink, lined by stratified squamous epithelium Figure 22.3c The McGraw-Hill Companies

Larynx Cartilaginous chamber about 4 cm long Functions – Keep food and drink out of airway Epiglottis Vestibular folds (internal folds on each side of larynx) – Production of sound Vocal folds (second pair of internal folds on each side of larynx) Framework composed of nine cartilages – First three solitary and large Epiglotic - spoon-shaped supportive plate Thyroid – large shield-shaped, laryngeal prominence Cricoid – connects larynx to trachea, ring-like – Second three smaller and paired Corniculate – attached to arytenoid superiorly Arytenoid – posterior to thyroid Cuneiform – Supports soft tissues between arytenoids and epiglottis Fibrous ligaments – bind cartilages of larynx together and to adjacent structures – Extrinsic – thyrohyoid and cricotracheal – Intrinsic – 2 pairs of vestibular and vocal ligaments

Views of Larynx Figure 22.4 a-c Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epiglottis Hyoid bone Thyroid cartilage Laryngeal prominence Arytenoid cartilage Cricoid cartilage Trachea (a) Anterior(b) Posterior(c) Median Tracheal cartilage Epiglottic cartilage Epiglottis Cuneiform cartilage Corniculate cartilage Arytenoid cartilage Arytenoid muscle Cricoid cartilage Vocal cord Thyroid cartilage Vestibular fold Fat pad Hyoid bone Thyrohyoid ligament Cricotracheal ligament

Muscles of Larynx Intrinsic Operate vocal cords Pull on corniculate and arytenoid cartilage – Pivot and abduct or adduct vocal cords – Air forced through adducted vocal cords causes them to vibrate Produces sound Extrinsic Infrahyoid group Connect larynx to hyoid Elevate larynx during swallowing

Lower Respiratory Tract Larynx Trachea Carina Main bronchi Lobar bronchi Thyroid cartilage Cricoid cartilage Trachealis muscle Hyaline cartilage ring Lumen Mucosa Mucous gland Perichondrium (c) (a) (b) Particles of debris Cartilage Chondrocytes Mucociliary escalator Mucus Ciliated cell Segmental bronchi Epithelium: Goblet cell Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 22.7 a-c

Trachea Windpipe, rigid tube about 12 cm in length and 2.5 cm diameter – Anterior to esophgus – Supported by C-shaped rings Trachealis muscle spans opening in rings Inner lining – Ciliated pseudostratified columnar epithelium – Mucociliary escalator Carina – internal median ridge in lowermost tracheal cartilage Custom Medical Stock Photo, Inc.

Lungs Right lung – Three lobes divided by horizontal and oblique fissures Left lung – Two lobes divided by oblique fissure Pleurae – Visceral – Parietal – Pleural cavity Pleural fluid (b) Mediastinal surface, right lung Copyright © The McGraw-Hill Companies

The Bronchial Tree Right main bronchus (primary) Superior, middle, inferior lobar bronchi (secondary) Segmental bronchi (tertiary), 10 – Bronchopulmonary segment Bronchioles – Pulmonary lobules Terminal bronchioles Respiratory bronchioles Alveolar ducts Alveolar sacs – atrium Left main bronchus Superior and inferior lobar bronchi Segmental bronchi, 8 Bronchioles Terminal bronchioles Respiratory bronchioles Alveolar ducts Alveolar sacs – atrium

Alveoli ~ 150 million sacs for gas exchange – Why so many? Cells types – Squamous alveolar cells (type I) 95% of surface, thinness allows rapid gas exchange – Great alveolar cells (type II) Repair alveolar epithelium Secrete surfactant – Alveolar macrophages (dust cells) Phagocytize dust particles, bacteria, debris Respiratory membrane Copyright © The McGraw-Hill Companies

Ventilation Respiratory cycle – Inspiration – Expiration Respiratory muscles – Diaphragm – Intercostals – Accessory muscles of respiration Sternocleidomastoids, scalenes, pectoralis muscles, serratus anterior, erector spinae

Sternocleidomastoid (elevates sternum) Scalenes (fix or elevate ribs 1–2) External intercostals (elevate ribs 2–12, widen thoracic cavity) Pectoralis minor (cut) (elevates ribs 3–5) Internal intercostals, intercartilaginous part (aid in elevating ribs) Diaphragm (descends and increases depth of thoracic cavity) Inspiration Internal intercostals, interosseous part (depress ribs 1–11, narrow thoracic cavity) Diaphragm (ascends and reduces depth of thoracic cavity) Rectus abdominis (depresses lower ribs, pushes diaphragm upward by compressing abdominal organs) External abdominal oblique (same effects as rectus abdominis) Forced expiration Respiratory Muscles Figure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Neural Control of Breathing Conscious and sub-conscious control Three pairs of respiratory centers in reticular formation of medulla and pons – Ventral respiratory group (VRG) Inspiratory (I) neurons Expiratory (E) neurons – Dorsal respiratory group (DRG) External influence of VRG Integrating center – Central and peripheral chemoreceptors, stretch receptors, irritant receptors – Pontine respiratory group Integrates input from higher brain centers Influences VRG and DRG Modifies breathing to sleep, emotional responses, exercise, other special circumstances

Respiratory Control Centers Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central chemoreceptors Spinal integrating centers Glossopharyngeal n. Vagus n. Diaphragm and intercostal muscles Accessory muscles of respiration Ventral respiratory group (VRG) Dorsal respiratory group (DRG) Medulla oblongata Pontine respiratory group (PRG) Pons Output from hypothalamus, limbic system, and higher brain centers Phrenic n. Intercostal nn. Key Inputs to respiratory centers of medulla Outputs to spinal centers and respiratory muscles Figure 22.14

Taking a Breath Inspiration – Boyle’s law Pressure of a gas inversely proportional to its volume at constant temp. – Charles’s law Volume of a gas directly proportional to its temperature at constant pressure Expiration – Passive process, elastic recoil of thoracic cage Resistance to airflow – Diameter of bronchioles – Pulmonary compliance – Surface tension of alveoli

Measurements of Ventilation Spirometer Dead space – Approx. 150 ml of air remain in conductive division – Alveolar ventilation rate (AVR) – volume of air used in gas exchange X breaths/min Tidal volume (TV) – one cycle of quite breathing, about 500 ml Inspiratory reserve volume (IRV) – amount that can be inhaled beyond TV inhalation, 3000 ml Expiratory reserve volume (ERV) – amount that can be forcefully exhaled beyond TV exhalation, 1200 ml Residual volume (RV) – volume of air that remains even after maximal expiration, 1300 ml

Lung Volumes and Capacities Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lung volume (mL) 6,000 5,000 4,000 3,000 2,000 1,000 0 Maximum possible inspiration Inspiratory reserve volume Expiratory reserve volume Residual volume Maximum voluntary expiration Functional residual capacity Total lung capacity Tidal volume Inspiratory capacity Vital capacity

Spirometry Restrictive disorders – Reduce pulmonary compliance – Appear as a reduced vital capacity Obstructive disorders – Blockage or narrowing of airway – More difficult to inhale/exhale given amount of air – Measure by forced expiratory volume (FEV) Percentage of vital capacity that can be exhaled in a given time interval – 75-85% in 1 second for healthy adult

Gas Exchange Involves oxygen and carbon dioxide Composition of air – 78.6% N 2, 20.9% O 2,.04% CO 2, 0.5% H 2 O Dalton’s law – total atmospheric pressure is sum of partial pressures of individual gases Composition of gases will vary depending on where air is in the respiratory tract – Inhaled air differs from alveolar air differs from exhaled air

Driving Force Behind Alveolar Exchange Diffusion down concentration gradient – Have to consider that we are going from air to water Henry’s law – for a given temperature, at the air-water interface the amount of gas that dissolves in the water is determined by its solubility in water and its partial pressure in air Erythrocytes load O 2 and unload CO 2 Efficiency of exchange may be affected by: – Pressure gradients, solubility, membrane thickness and area, ventilation-perfusion coupling

Gas Transport Oxygen binds to hemoglobin (98.5%) – Oxyhemoglobin (HbO 2 ) Carbon dioxide – Carbonic acid (90%) – Carbamino compounds (carbaminohemoglobin, HbCO 2 ) – Dissolved gases

Systemic Gas Exchange Systemic gas exchange - the unloading of O 2 and loading of CO 2 at the systemic capillaries CO 2 loading – CO 2 diffuses into the blood – carbonic anhydrase in RBC catalyzes CO 2 + H 2 O  H 2 CO 3  HCO H + – chloride shift keeps reaction proceeding, exchanges HCO 3 - for Cl - H + binds to hemoglobin O 2 unloading – H + binding to HbO 2 reduces its affinity for O 2 tends to make hemoglobin release oxygen HbO 2 arrives at systemic capillaries 97% saturated, leaves 75% saturated – – venous reserve – oxygen remaining in the blood after it passes through the capillary beds – Utilization coefficient – given up 22% of its oxygen load

Systemic Gas Exchange Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Respiring tissueCapillary blood Dissolved CO 2 gas CO 2 + plasma protein CO 2 O2O2 Dissolved O 2 gas Carbamino compounds Cl – 7% 23% 70% 98.5% 1.5% CO 2 + Hb CO 2 + H 2 O O 2 + HHb HbO 2 + H + H 2 CO 3 HCO 3 – + H + HbCO 2 CAH Key Chloride shift CO 2 O2O2 HbCO 2 Carbaminohemoglobin Hb Hemoglobin HHb Deoxyhemoglobin CAH Carbonic anhydrase HbO 2 Oxyhemoglobin Figure 22.24

Alveolar Gas Exchange Reactions that occur in the lungs are reverse of systemic gas exchange CO 2 unloading – As Hb loads O 2 its affinity for H + decreases, H + dissociates from Hb and bind with HCO 3 - CO 2 + H 2 O  H 2 CO 3  HCO H + – Reverse chloride shift HCO 3 - diffuses back into RBC in exchange for Cl -, free CO 2 generated diffuses into alveolus to be exhaled

Alveolar Gas Exchange Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Respiratory membraneCapillary blood CO 2 O2O2 Alveolar air Carbamino compounds 7% 23% 70% 98.5% 1.5% HbCO 2 CAH Key Cl  Chloride shift CO 2 O2O2 Dissolved O 2 gas O 2 + HHb HbO 2 + H + HCO 3  + H + H 2 CO 3 CO 2 + H 2 O CO 2 + Hb CO 2 + plasma protein Dissolved CO 2 gas Hb Hemoglobin HbCO 2 Carbaminohemoglobin HbO 2 Oxyhemoglobin HHb Deoxyhemoglobin CAH Carbonic anhydrase Figure 22.25

Concentration Gradients of Gases Figure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alveolar gas exchange O 2 loading CO 2 unloading Gas transport O 2 carried from alveoli to systemic tissues CO 2 carried from systemic tissues to alveoli Systemic gas exchange O 2 unloading CO 2 loading Expired air Inspired air P O mm Hg P CO 2 32 mm Hg Alveolar air P O mm Hg P CO 2 40 mm Hg Tissue fluid P O 2 40 mm Hg P CO 2 46 mm Hg Deoxygenated blood P O 2 40 mm Hg P CO 2 46 mm Hg Oxygenated blood P O 2 95 mm Hg P CO 2 40 mm Hg P O mm Hg P CO mm Hg CO 2 Pulmonary circuit Systemic circuit CO 2 O2O2 O2O2

Adjustment to the Metabolic Needs of Individual Tissues Hemoglobin unloads O 2 to match metabolic needs of different states of activity of the tissues Four factors that adjust the rate of oxygen unloading – ambient P O 2 active tissue has  P O 2 ; O 2 is released from Hb – temperature active tissue has  temp; promotes O 2 unloading – Bohr effect active tissue has  CO 2, which lowers pH of blood ; promoting O 2 unloading – bisphosphoglycerate (BPG) RBCs produce BPG which binds to Hb; O 2 is unloaded Haldane effect – rate of CO 2 loading is also adjusted to varying needs of the tissues, low level of oxyhemoglobin enables the blood to transport more CO 2  body temp (fever), thyroxine, growth hormone, testosterone, and epinephrine all raise BPG and cause O 2 unloading  metabolic rate requires  oxygen

Blood Gases and the Respiratory Rhythm Rate and depth of breathing adjust to maintain levels of: – pH 7.35 – 7.45 – P CO 2 40 mm Hg – P O 2 95 mm Hg Brainstem respiratory centers receive input from central and peripheral chemoreceptors that monitor the composition of blood and CSF Most potent stimulus for breathing is pH, followed by CO 2, and least significant is O 2

Hydrogen Ions Acidosis – blood pH lower than 7.35 Alkalosis – blood pH higher than 7.45 Hypocapnia – P CO 2 less than 37 mm Hg (normal 37 – 43 mm Hg) most common cause of alkalosis Hypercapnia – P CO 2 greater than 43 mm Hg most common cause of acidosis

Effects of Hydrogen Ions Respiratory acidosis and respiratory alkalosis – pH imbalances resulting from a mismatch between the rate of pulmonary ventilation and the rate of CO 2 production Hyperventilation is a corrective homeostatic response to acidosis – “blowing off ” CO 2 faster than the body produces it – pushes reaction to the left CO 2 (expired) + H 2 O  H 2 CO 3  HCO  H + – reduces H + (reduces acid) raises blood pH towards normal Hypoventilation is a corrective homeostatic response to alkalosis – allows CO 2 to accumulate in the body fluids faster than we exhale it – shifts reaction to the right – CO 2 + H 2 O  H 2 CO 3  HCO H + – raising the H + concentration, lowering pH to normal

Effects of Oxygen P O 2 usually has little effect on respiration Chronic hypoxemia, P O 2 less than 60 mm Hg, can significantly stimulate ventilation – Hypoxic drive – respiration driven more by low P O 2 than by CO 2 or pH – Emphysema, pneumonia – High elevations after several days

Respiration and Exercise Causes of increased respiration during exercise 1.When the brain sends motor commands to the muscles Also sends this information to the respiratory centers Increase pulmonary ventilation in anticipation of the needs of the exercising muscles 2.Exercise stimulates proprioceptors of the muscles and joints Transmit excitatory signals to the brainstem respiratory centers Increase breathing because they are informed that the muscles have been told to move or are actually moving Increase in pulmonary ventilation keeps blood gas values at their normal levels in spite of the elevated O 2 consumption and CO 2 generation by the muscles

Effect of Smoking Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) Healthy lung, mediastinal surface(b) Smoker's lung with carcinoma Tumors a: © The McGraw-Hill Companies/Dennis Strete, photographer; b: Biophoto Associates/Photo Researchers, Inc. Figure a-b