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Notes from Dr. Siddique's class...

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The Respiratory System Chapter 22 Because of the close relationship between respiratory and circulatory systems, these are often considered together under Cardiopulmonary system. This system is also functionally connected to the urinary system in order to maintain acid-base balance.

22.1 Anatomy of the Respiratory System Respiration: 3 meanings ventilation of lungs (breathing) exchange of gases between • air and blood • blood and tissue fluid – use of O2 in cellular metabolism (cellular respiration) – discussed in ch. 2.

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Functions of the Respiratory system: Read the first page from ch 22. Principal Organs of the Respiratory System (Fig:22.1)

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Nose, pharynx, larynx, trachea, bronchi, lungs

General Aspects of Respiratory System • Airflow in lungs – bronchi  bronchioles  alveoli (millions of them are the dead ends of airway)

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Conducting division passages serve only for airflow, nostrils to major bronchioles Respiratory division alveoli and distal gas-exchange regions Upper respiratory tract (Fig: 22.3) organs in head and neck, nose through larynx Lower respiratory tract organs of the thorax, trachea through lungs

A) The Nose • Functions – warms, cleanses, humidifies inhaled air – detects odors – resonating chamber that amplifies the voice – nose extends from nostrils (ant. or ext. nares – nerr-eez) to choanae (post. or int. nares)

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Bony and cartilaginous supports (Fig: 22.2) superior half: nasal bones medially & maxillae laterally inferior half: lateral and alar cartilages 1

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ala nasi: flared portion shaped by dense CT, forms lateral wall of each nostril

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Nasal septum divides nasal cavity into right & left chambers called nasal fossae – inferior part formed by vomer – superior part by perpendicular plate of ethmoid bone – anterior part by septal cartilage – ethmoid and sphenoid bones compose the roof, palate forms the floor – vestibule: dilated chamber inside ala nasi

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Conchae & Meatuses – superior, middle & inferior nasal conchae are 3 folds of tissue on lateral wall of nasal fossa – meatuses are narrow air passage beneath each conchae Mucosa − olfactory mucosa (for ___?____) lines roof of nasal fossa − respiratory mucosa lines rest of nasal cavity with _________________ epi. – mucus (from goblet cells) traps inhaled particles and lysozyme in mucus destroys bacteria Cilia and Erectile Tissue − cilia of respiratory epithelium drive debris-laden mucus into pharynx to be swallowed − erectile tissue (swell body) of inferior concha is a venous plexus that rhythmically engorges with blood and is the most common site for spontaneous epistaxis (nosebleed)

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B) The Pharynx • Common pathway for both food and air, muscular funnel extending from the choanae to larynx (app 13cm)

3 regions:

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Nasopharynx (pseudostratified epithelium) – posterior to choanae, dorsal to soft palate, passes air only – receives auditory tubes and contains pharyngeal tonsil

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Oropharynx (stratified squamous epithelium) – extends proximally from soft palate superiorly and root of tongue inferiorly to distally as far as the hyoid bone; anteriorly has the fauces (opening of oral cavity to pharynx) – contains palatine and lingual tonsils

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Laryngopharynx (stratified squamous epithelium) – extends from hyoid bone to cricoid cartilage (inferior end of larynx) where it joins the esophagus

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C) The Larynx

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App 1.5inches (4cm) long cartilaginous chamber that keeps the swallowed material out of airway, and it also produces sound (voice box)

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2 mechanisms that keep the swallowed material out: − glottis is the superior opening that is guarded by epiglottis (tissue flap); during swallowing, larynx is pulled up by its extrinsic muscles and epiglottis is pushed down by tongue  food & drink slides on epiglottis into the esophagus − vestibular folds on the upper interior wall closes the glottis during swallowing

Views of Larynx: (Fig: 22.3 and 22.4) Nine Cartilages of Larynx (Fig: 22.4) • Epiglottic cartilage

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Thyroid cartilage - largest, has laryngeal prominence Cricoid cartilage – ring like, connects larynx to trachea Arytenoid cartilages (2) - posterior to thyroid cartilage Corniculate cartilages (2) - attached to arytenoid cartilages like a pair of little horns Cuneiform cartilages (2) - support soft tissue between arytenoids and the epiglottis Epiglottic is of elastic cartilage, rest are all ____________ cartilage.

Walls of Larynx • Interior wall has 2 folds on each side, from thyroid to arytenoid cartilages – vestibular folds: superior pair, close glottis during swallowing – vocal cords or vocal folds: produce sound (Fig: 22.4 & 22.5)

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Intrinsic muscles - rotate corniculate and arytenoid cartilages, which adducts (tightens: high pitch sound) or abducts (loosens: low pitch sound) vocal cords (Fig: 22.6)

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Extrinsic muscles - connect larynx to hyoid bone, elevate larynx during swallowing

D) The Trachea (Figs: 22.7 and 22.8) • Rigid tube 12cm (4.5 in.) long, anterior to esophagus, called the windpipe

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Supported by 16 to 20 C-shaped cartilaginous rings – opening in rings faces posteriorly towards esophagus (allows_____________) – trachealis muscle spans opening in rings, adjusts airflow by expanding or contracting

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Inferiorly, it branches into R & L Primary Bronchi which then enters the lungs and branches out to form the bronchial tree

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Larynx, trachea, and the bronchial tree are lined with __________________________ epithelium which functions as mucociliary escalator Read the insight (22.1) on Tracheostomy

E) The Lungs and Bronchial Tree Surface Anatomy (Fig 22.9)    

Has apex; concave base rests on diaphragm Anteriorly is the broad costal surface; medially, smaller concave surface facing the heart is the mediastinal surface Mediastinal surface has a slit – the “hilum” through which blood vessels, lymph vessels, nerves etc enter the lungs; What is “root” of the lung? Left lung is little smaller and has two lobes (sup & inf) separated by a deep fissure; right lung is larger w/ three lobes (sup, middle, & inf) separated by 2 fissures See Fig 22.10 to learn about the surrounding structures of the lungs

The Bronchial Tree The spongy parenchyma of the lungs have a highly branched air conducting pathway known as the bronchial tree that extends from the primary bronchus to terminal bronchioles • 2 Primary bronchi (C-shaped rings) – arise from trachea at the angle of sternum, after 2-3 cm enter hilum of lungs

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Secondary (lobar) bronchi (overlapping plates of cartilage) – each primary bronchus branches into one secondary bronchus for each lobe (so, ____ in the left and ____ in the right)

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Tertiary (segmental) bronchi (overlapping plates of cartilage) – each secondary bronchus branches into 8 in the left and 10 in the right tertiary or segmental bronchi – bronchopulmonary segment: portion of lung supplied by each tertiary bronchi

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Bronchioles − each tertiary bronchi divides into several bronchioles (continuation of airway) – pulmonary lobule: portion ventilated by one bronchiole – have layer of smooth muscle – not cartilage – divides into 50-80 terminal bronchioles (ends conducting division) – Fig 22.12 – each terminal bronchiole gives off 2 or more respiratory bronchioles (beginning of respiratory division)

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respiratory bronchioles divide into 2-10 elongated, thin-walled passages called alveolar ducts – alveolar ducts end in alveolar sacs (grape like clusters of alveoli) – alveoli bud from respiratory bronchioles, alveolar ducts and alveolar sacs – each lung has app 150 mil alveoli (lined by S. Sq. epi. – facilitates what?) 

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Alveoli each alveolus has alveolar macrophages wandering in the lumen – for defense – each alveolus is surrounded by blood capillaries supplied by ______________ The barrier between alveolar air & blood is called the Respiratory membrane – The low blood capillary pressure and high oncotic pressure causes the osmotic uptake of water to override filtration & thus keep the alveoli fluid free

So, the airflow from the nose deep into the lung tissue is: Nostril/mouth 

F) The Pleurae

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Pleura has two layers: visceral and parietal layers Pleural cavity is filled with pleural fluid Functions of pleura and pleural Fluid – reduction of friction – creation of pressure gradient • lower pressure assists in inflation of lungs – compartmentalization by pleura and pericardium • prevents spread of infection

22.2 Pulmonary Ventilation Respiration involves inspiration and expiration that allows air to be inhaled and exhaled. Respiratory Cycle: one cycle of inspiration and expiration. This is repetitive. Define Quiet and Forced respiration: Pressure gradients (between?) cause the “flow of air” in and out of the body. The respiratory muscles help to create the pr. gradient. A) The Respiratory Muscles (Fig 22.13) • Diaphragm (dome shaped) – it flattens during its contraction  increases thoracic cavity (volume)  pressure decreases in thorax  air flow in • Scalenes - fix first pair of ribs

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External intercostals - elevate 2 - 12 pairs Accessory Respiratory muscles: (not needed for test) - Pectoralis minor, sternocleidomastoid and erector spinae muscles - used in deep inspiration. These muscles, thoracic cavity (volume)  ___ pressure  air flows ___. -

Rectus abdominis, internal intercostals, other lumbar, abdominal, and pelvic muscles – used in forced expiration. Opposite mechanism.

B) Neural Control of Breathing • Breathing depends on repetitive stimuli from brain

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Neurons in medulla oblongata and pons control unconscious breathing Voluntary control provided by the motor cortex in the frontal lobe Inspiratory (I) neurons: fire during inspiration Expiratory (E) neurons: fire during forced expiration Innervation: Fibers travel down spinal cord to lower motor neurons in cervical and thoracic region; fibers of phrenic nerve go to diaphragm and intercostal nerves go to intercostal muscles

Brainstem Respiratory Centers (Fig 22.14)

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Two respiratory nuclei in Medulla Oblongata inspiratory center (dorsal respiratory group or DRG – I neurons) more frequently they fire, more deeply you inhale – expiratory center (ventral respiratory group or VRG – has both I and E neurons) involved in forced expiration

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Pons – pneumotaxic center • sends continual inhibitory impulses to inspiratory center that controls the rate and depth – apneustic center • prolongs inspiration, role unclear Central and Peripheral Input to the Respiratory Centers (not needed for the test) • Hyperventilation: Input from limbic system and hypothalamus - effects respiration during pain and emotional outbursts

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Central & Peripheral chemoreceptors (Fig22.15): Input from Brainstem and Arteries (which ones??) - monitor blood pH, CO2 & O2 levels

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Stretch Receptors: Input from receptors at bronchi, bronchiole etc. - inflation reflex or Hering-Breuer reflex: excessive inflation/stretching triggers this reflex, inhibits I neurons & stops inspiration Irritant Receptors: response to inhaled irritants

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stimulate vagal afferents to medulla, results in bronchoconstriction, coughing

Voluntary Control of Breathing • Neural pathways Motor cortex of frontal lobe of cerebrum sends impulses down corticospinal tracts to respiratory neurons in spinal cord, bypassing brainstem – allows voluntary control of respiration

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Limitations on voluntary control When blood CO2 level rises - cause automatic respiration to take over

C) Pressure, Resistance, and Airflow Respiratory airflow is governed by the same principles of flow, pressure, and resistance as blood flow (Respiratory Cycle: Fig: 22.16) • Flow of a fluid is directly proportional to the pressure difference between two points, and the flow of a fluid is inversely proportional to resistance • Atmospheric pressure drives respiration - the weight of the air above us is 760 mm Hg at sea level = 1 atmosphere (atm)

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Boyle’s Law – at a constant temperature, the pressure of a given quantity of gas is inversely proportional to its volume • if the lungs contain a quantity of gas and the lung volume increases, their internal pressure (intrapulmonary pressure) will fall - if the pressure falls below atmospheric pressure, air moves/flows into the lungs • if the lung volume decreases, intrapulmonary pressure rises - if the pressure rises above atmospheric pressure the air flows out of the lungs

Inspiration • As the rib cage expands, parietal pleura stretched   intrapleural pressure

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Visceral pleura clings to parietal pleura  lungs expand   intrapulmonary pr Transpulmonary pressure (intrapleural minus intrapulmonary pressure) gradient causes inflation of lungs and the pressure gradient from the atmospheric air to intrapulmonary air causes air to flow in Inflation of lungs aided by warming of inhaled air (volume of air increases w/  temp – Charles’s Law) A quiet breathe flows 500 ml of air through lungs

Expiration • Inspiration is an active process, whereas, normal expiration is a passive process

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In quiet breathing, expiration is achieved by elasticity of lungs & thoracic cage As volume of thoracic cavity , intrapulmonary pressure , and air is expelled Forced Expiration is an active process Internal intercostal muscles depress the ribs &  thoracic cavity volume; and

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abdominal muscles contract &  intra-abdominal pressure forcing diaphragm upward – both actions  pressure on thoracic cavity = forceful expiration Pneumothorax - presence of air in pleural cavity. Negative intrapleural pressure is lost causing the lungs to recoil and collapse - called atelectasis

Resistance to Airflow • Airflow is inversely proportional to resistance

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Factors governing resistance and thus the air flow are: 1. Bronchiolar diameter - Bronchoconstriction - triggered by airborne irritants, cold air, parasympathetic stimulation, histamine - Bronchodilation – triggered by sympathetic nerves, epinephrine 2. Pulmonary compliance (distensibility of the lungs) - When lungs lose compliance from fibrosis of tissue from TB etc, it fails to expand even when transpulmonary pr. change.  resistance air flow 3. Alveolar Surface Tension - Surface tension of water in the alveoli and distal bronchioles, that is necessary for gas exchange, resists inspiration and promotes expiration - This surface tension would act to collapse alveoli and distal bronchioles - Pulmonary surfactant released from the great alveolar cells disrupt hydrogen bonds of water and  surface tension - As passages contract during expiration, surface tension naturally  and surfactant concentration  preventing alveolar collapse - Respiratory distress syndrome (RDS) in premature infants is due to a deficiency of surfactant – treated by administering artificial surfactant

D) Alveolar Ventilation Dead air - fills conducting division of airway, cannot exchange gases  Anatomic dead space is conducting division of airway  Physiologic dead space is sum of anatomic dead space and any pathological alveolar dead space  Alveolar ventilation rate (AVR) - air that actually ventilates alveoli X respiratory rate - directly relevant to body’s ability to exchange gases E) Spirometry – The Measurement of Pulmonary Ventilation Spirometer - device a subject breathes into that measures ventilation and determines pulmonary function Respiratory volumes: 4 measurements (Table: 22.2 and Fig: 22.17) – Tidal volume: air inhaled or exhaled in one quiet breath – Inspiratory reserve volume: air in excess of tidal inspiration that can be inhaled with maximum effort – Expiratory reserve volume: air in excess of tidal expiration that can be exhaled with maximum effort 8

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Residual volume: air remaining in lungs after maximum expiration, keeps

alveoli inflated Respiratory capacities: 4 measurements (Table: 22.2 and Fig: 22.17) − Vital capacity: amount of air that can be exhaled with maximum effort after maximum inspiration; assess strength of thoracic muscles and pulmonary function − Inspiratory capacity: maximum amount of air that can be inhaled after a normal tidal expiration − Functional residual capacity: amount of air in lungs after a normal tidal expiration − Total lung capacity: maximum amount of air lungs can contain Airflow is measured by having a subject exhale as rapidly as possible into a spirometer

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Forced expiratory volume (FEV) % of vital capacity exhaled/ time

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Peak flow

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maximum speed of exhalation

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Minute respiratory volume (MRV) – TV x Respiratory rate, at rest 500 x 12 = 6 L/min – maximum: 125 to 170 L/min after heavy exercise – this is maximum voluntary ventilation (MVV) F) Variations in the Resp Rhythm  

Eupnea: Relaxed, quiet breathing – normal breathing Variations in Resp Rhythm: Table 22.3 - memorize the important Clinical Terminologies

22.3 Gas Exchange and Transport A) Composition of Air In a mixture of gases, each contributes its partial pressure, (at sea level 1 atm. of pressure = 760 mmHg). Dalton’s Law: Look at Table 22.1. – Nitrogen constitutes 78.6% of the atmosphere, PN2 = 78.6% x 760 mmHg = 597 mmHg – PO2 = 159, PH2O = 3.7, PCO2 = 0.3 mmHg (597 + 159 + 3.7 + 0.3 = 760) Partial pressures determine rate of diffusion of gas and gas exchange between blood and alveolus Alveolar air is different from atmospheric air because it is humidified, it exchanges gases with blood, and mixes with residual air – contains: PN2 = 569, PO2 = 104, PH2O = 47, PCO2 = 40 mmHg (Table 22.4) B) Alveolar Gas Exchange

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At air-water interface, gases diffuse down their concentration gradients (Fig 22.19). Henry’s law: amount of gas that dissolves in water is determined by its solubility in water and its partial pressure in air. (See fig 22.19 and determine O2 loading & CO2 unloading) Time required for gases to equilibrate = 0.25 sec RBC transit time at rest = 0.75 sec to pass through alveolar capillary RBC transit time with vigorous exercise = 0.3 sec Factors Affecting Gas Exchange Pressure gradients of the gases (Fig: 22.20) PO2 = 104 in alveolar air versus 40 in blood (what unit?) PCO2 = 46 in blood arriving versus 40 in alveolar air Solubility of the gases – CO2 is 20 times as soluble as O2; O2 has  conc. gradient but CO2 has  solubility. As a result, equal amounts of the two gases are exchanged. Membrane thickness - only 0.5 m thick; edema, fibrosis etc would ↓ exchange Membrane surface area - 100 ml blood in alveolar capillaries, spread over 70 m2 Ventilation-perfusion coupling (Fig 22.23) - areas of poor ventilation  vasoconstriction; - areas of good ventilation  vasodilation - In other words, blood is redirected for better perfusion (Lung Disease Affects Gas Exchange: See Fig: 22.22) Perfusion Adjusts to Changes in Ventilation: blood flow matches airflow Ventilation Adjusts to Changes in Perfusion: airflow matches blood flow (Fig: 22.23)

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C) Gas Transport It is the process of carrying gas...