Unit 2 Respiratory System Functional Anatomy

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24 Terms

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Structure of the nose/nasal cavity.

Structure

  • External nose:

    • made of hyaline cartilage and maxillary bone

    • covered externally by skin with sebaceous glands and nasal hairs

  • Nasal Vestibule:

    • lined with stratified squamous epithelium and big hairs for large particles

  • Main Nasal Cavity

    • lined with respiratory epithelium with goblet cells that secrete mucus

    • contains conchae (superior, middle and lower) that project into the cavity like shelves → increase SA and create turbulence in airflow (trappening of particles and moistening of inspired air and heat exchange)

    • has a rich vascular supply

    • Submucosa contains seromucous glands that moisten air and trap particles

  • Olfactory Region

    • found in the roof of the nasal cavity near the cribiform plate

    • contains olfactory epithelium with sensory neurons that detect smells

    • secretes mucus that dissolves odor molecules

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Function of the nose/nasal cavity

  1. Air Conduction:

    • Primary entry point for inhaled air.

    • Channels air to the pharynx and down to the lungs.

  2. Air Conditioning:

    • Warming: Through heat exchange with blood vessels.

    • Humidifying: Via moisture from mucus and serous secretions.

    • Filtering: Hairs and mucus trap dust, pathogens, and debris.

  3. Olfaction (Smell):

    • Specialized neurons in the roof of the nasal cavity detect odorants.

  4. Resonance for Phonation:

    • The nasal cavity contributes to the resonance of the voice (tone quality).

  5. Defense:

    • Mucus traps microbes; cilia sweep mucus to the pharynx to be swallowed or expelled.

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Location of Nose and Nasal Cavity

  • The external nose is located centrally on the face, projecting from the face between the eyes and above the upper lip.

  • The nasal cavity is internal, lying posterior to the external nose and extending back to the pharynx.

  • It is separated:

    • Superiorly by the cribriform plate of the ethmoid bone (just below the brain).

    • Inferiorly by the hard and soft palate, which separates it from the oral cavity.

    • Medially by the nasal septum, formed by the vomer and perpendicular plate of the ethmoid bone.

    • Laterally by bones that form ridges called conchae (turbinates).

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Paranasal Sinuses

  • boney chambers surrounding nasal cavity and lined by respiratory epithelium

  • air filled cavities in skull bones (frontal, maxillary, sphenoid, ethmoid)

  • lighten skin, add resonance to phonation and facilitate air conditioning

  • contains canals that drain mucus in the nasal cavity

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Pharynx

  • connects nasal and oral cavities to the larynx and esophagus

  • functions in air conditioning, sound resonance, and food diversion during swallowing

  • has 3 regions: nasopharynx, laryngopharynx, and oropharynx

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List the protective mechanisms of the respiratory system.

Protective Mechanisms

  • mucous and cilia

  • goblet cells that secrete mucous with defensins

  • nasal hairs

  • lysosome and enzymes in mucous

  • sneezing and coughing reflexes

  • immune surveillance

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Conducting Zone

Conducting

  • laryngopharynx → terminal bronchioles

  • contains structures involved in phonation

  • includes larynx (primary organ of phonation), trachea, bronchi and bronchioles

  • superior limit is epiglottis

  • external structures made of hyaline cartilage linked by ligaments

  • mucosa lined by epithelia in regions of high turbulence and respiratory epithelia in other regions

  • submucosa contains seromucous glands

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Respiratory Zone

  • Respiratory Bronchioles to aveoli

  • functions in gas exchange

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Larynx

  • primary organ of phonation

  • superior → epiglottis

    • made of elastic cartilage + epithelia with taste buds

    • elevation of larynx allows epiglottis to cover larynx during swallowing

  • external structures made of hyaline cartilage linked by ligaments

  • internal structures include vocalis muscles and vocal folds

    • superior: vestibular fold (false vocal cord)

    • Inferior: vocal fold (true vocal cord)

      • forms slit like opening → glottis

      • width/stiffness determines pitch (narrow - high)

      • regulated by vocalis muscle

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Trachea

  • connects the larynx to the bronchi as it goes downward

  • in front of esophagus

  • mucous lined with resp epithelia

  • submucosa contains C-shaped cartilage

    • shorten to decrease diameter during coughing

    • seromucous glands between C’s

  • inferior: carina

    • mucosa rich in sensory nerves → coughing

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Bronchi/bronchioles

  • from trachea to resp bronchioles

  • one for each lung

    • primary → secondary → tertiary → bronchioles

    • 3 for right and 2 for left

  • branching = small diameter

  • mucosal changes from trachea and bronchi → bronchioles

    • fewer mucous glands from bronchi to bronchiole

    • pseudostratified → columnar → cuboidal

    • decrease in goblet cells and cilia

  • submucosa → plates of cartilage instead of C shaped in bronchi

  • Bronchioles don’t have cartilage

    • major site for air flow/resistance

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Respiratory Membrane + its function

  • Aveolar membrane (made of type 1 alveolar cells + basement cells)

    • inner lining of the air sacs in the lungs

    • consists of Type 1: thin, flattened cells that allow for easy diffusion + the majority of the alveolar surface

    • basement membrane: thin layer of connective tissue that provides support + structure for alveolar cells

  • thin interstitial space

    • small gap between aveolar membrane + capillary endothelium that contains fluid + CT fibers

  • capillary endothelium

    • lines capillaries that surrounds the alveoli + composed of a thin layer of cells + its own basement membrane

Function

  • designed for efficient gas exchange of oxygen in blood and CO2 out of blood

  • vast surface area

  • Surfactant → reduces surface tension in alveoli → preventing them from collasping

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Respiratory Passageway Order

  • Nosenasal cavity → pharynxlarynxtracheabronchi (primary, secondary, tertiary) → bronchiolesterminal bronchioles → respiratory bronchioles → alveolar ducts → alveolar sacs → alveoli

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Lungs and Pleurae

Lungs

  • paired asymmetric organ within thoracic cavity

  • apex of lungs inferior clavicle and base rests upon diaphragm

  • bronchi,vessels and nerves penetrate lung at hilum forming lung root proximal to heart

  • right lung larger and with three lobes separated by fissures

  • left lung has two lobes with a fissure and cardiac notch

  • divided into connective tissue with bronchopulmonary segments

  • divided into lobules → main bronchiole → pulmonary artery/arteriolebranchesalveoli

  • thin connective tissue that forms capsule of organ and subdivides lobes, segments and lobules

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Pleura

  • parietal → thoracic walls → simple squamous

  • visceral → lungs surface → simple squamous

  • thin layer of serous fluid between parietal and visceral

    • maintain capillary tension to adhere lungs to thoracic walls

    • allows frictionless movement of lung within thoracic cavity

  • inflammation of pleural → pleurisy

  • too much serous fluid via leaky capillaries → pleural effusion

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Partial vacuum + importance

  • acts like a suction, preventing lung collapse and ensuring lungs expand during inhalation

  • negative pressure relative to aveolar pressure

  • during inhalation → the chest wall expands → increasing volume of thoracic cavity

  • creates a greater negative pressure + sucks lungs open → increases their volume and draws air in for gas exchange

  • Involves balance of forces → elastic recol of stroma and surface tension in aveoli + surface tension at pleura

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Boyle’s Law and inspiration/expiration

  • PV = P2V2

  • pressure inversely changes to volume

  • during inspiration → thoracic cavity volume increases → pressure drops → air flows in

  • During expiration → volume decreases → pressure increases → air flows out

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Inspiration

Inspiration

  • increase in lung volume mediated by changes in thoracic cavity volume

  • shortening of diaphragmflattens out and moves inferiorly

  • shortening of external intercostal muscle → lifts rib cage + sternum to increase the diameter of thoracic cavity → thoracic volume increase

  • decrease Ppul to -1 mm Hg

  • involves other muscles that can raise the ribs to expand the thoracic cavity

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Expiration

  • mostly passive relaxation of the inspiratory muscles and elastic recoil of lungs

  • inspiratory muscle relax → diaphragm rises, rib cage descend due to recoil of costal cartilage

  • thoracic cavity volume decreases

  • elastic lungs recoil passively → intrapulmon volume decreases

    • pressure rises

    • air flows out of the lungs and down the pressure gradient until intrapulmon pressure is 0

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Lung Volumes

  • Tidal volume → normal relaxed breathing (500 mL)

  • Inspiratory Reserveforced inhalation to maximum above TV (3100 ml)

  • Expiratory Reserveforced exhalation to minimum below TV (1200 ml)

  • Residual Volumevolume remaining after forced exhalationdead space of aveoli and conducting portion (1200 ml)

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Capacity

  • total lung capacity: TLC = TV + IVR +EVR + RV (6000 ml)

  • Vital lung capacity: VC = TV + IVR + EVR = TLC - RV (4800 ml)

  • Inspiratory capacity: IC = TV + IVR (3600 ml)

  • Functional Residual capacity: FVR = EVR + RC (2400 ml)

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Pulmonary Function Tests

  • type/effect of respiratory disease

  • classification of resp disease

  • easily measured with windmill type spirometer

    • FVC = vital capacity measured with volume spirometer

    • FEV = volume forcibly expired over a set time interval

  • diagnose obstructive and restrictive disease

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Physical Factors Affecting Ventilation

  • friction, aveolar surface tension and lung compliance

  • Flow rate = pressure diff (boyle’ law) + friction (resistance via conducting zone)

    • Resistance varies (low in trachea, max in med-sized bronchi and min at terminal bronchi)

    • bronchi + bronchioles can modified by smooth muscle + inflammation

    • local effectors and autonomic system can modulate

      • para → bronchoconstriction, sym → bronchodilation

  • Surface tension of aveoli

    • wetted surface that sticks together via capillary action

  • Lung Compliance

    • stretchiness

    • change in volume by a change in pressure

    • determined by elastin and surface tension of alveoli

    • stretchibility of lungs and thoracic cage

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