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Why Do We Breathe?
- ATP synthesis requires oxygen and produces carbon dioxide
- Respiratory and circulatory systems work together to bring oxygen to tissues and remove carbon dioxide
- Sometimes called cardiopulmonary system
- Disorders of lungs directly affect the heart and vice versa
- Respiratory and urinary systems work together to regulate acid/base balance
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Respiratory System Functions
- Provide extensive surface for O2 and CO2 exchange
- Allow production of sounds for speaking
- Facilitates smell
- Regulates pH of bodily fluids
- Regulates blood pressure (angiotensin II)
- Pressure gradients promote venous blood flow
- Expel abdominal contents during urination, defecation, and childbirth
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Conducting Division
- Passages that serve for air flow, not gas exchange
- Nose, pharynx, larynx, trachea, bronchioles
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Respiratory division
- Gas exchange regions
- Alveoli of lungs
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Upper respiratory Tract
- In head and neck
- Nose through larynx
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Lower Respiratory Tract
- Organs of thorax
- Trachea through lungs
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Respiratory Epithelium
- Goblet cells secrete mucus
- Cilia project mucus towards pharynx, where it's swallowed into digestive tract
- Called mucociliary elevator below pharynx, where cilia beat mucus in an upward direction
- Best protection against invading pathogens, allergens, and dust
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Cystic Fibrosis
- Gene responsible for regulating components of mucus is mutated, so mucus is unusually thick
- Mucus can't be carried by cilia, so pathogens are trapped and infection is common
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Nose
- Warms, cleanses, and humidifies inhaled air
- Extends from nostrils to posterior nasal apertures
- Facial part shaped by nasal bone and cartilage
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Nasal Fossae
Right and left halves of nasal cavity; divided by septum
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Septums of the Nose
Vomer, perpendicular plate, septal cartilage
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Vestibule
- Opening of nasal cavity
- Vibrissae in vestibule block insects and debris
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Nasal Conchae
- Folds of tissue with meatus beneath each one
- Air must contact mucous membrane before continuing on
- Ensures trapping most dust
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Pharynx
- Muscular funnel between posterior nasal apertures and larynx
- Shared by respiratory and digestive systems
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Nasopharynx
- Posterior to nasal apertures
- Receives eustachian tubes from middle ears
- Houses pharyngeal tonsil
- Large particles can't make sharp turn and get caught in mucosa near tonsil
- Passes only air
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Oropharynx
- Space between soft palate and epiglottis
- Contains palatine tonsils
- Pass air, food, drink from oral cavity and nasopharynx
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Laryngopharynx
- From epiglottis to esophagus
- Lies posterior to larynx
- Passes air, food, drink
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Functions of the Larynx
- Keeps food and drink out of the airway
- Epiglottis guards superior opening of larynx
- Stands vertically at rest
- When swallowing, extrinsic muscles pull larynx upward and tongue pushes epiglottis downward to meet it and close off larynx (food goes to esophagus)
- Vestibular folds: close the larynx during swallowing
- Vocal cords/glottis: Involved in sound production (phonation)
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Vocal Cords
- Intrinsic muscles of larynx move arytenoid and corniculate cartilage
- Adducted cords create higher pitch
- Abducted cords create lower pitch
- Length and thickness of cords determine range of pitches able to be produced
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Trachea
- Supported by C-shaped rings of hyaline cartilage
- Maintains structure
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Intubation and Tracheostomy
Methods of bypassing upper respiratory system
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Right Lung
- Shorter, wider
- 3 Lobes: superior, middle, and inferior
- Horizontal and oblique fissure
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Left Lung
- Taller, narrower
- 2 Lobes: superior and inferior
- Oblique fissure
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Main (primary) Bronchi
- Each main (primary) bronchi: branches into 65,000 terminal bronchioles
- Supported by c-shaped hyaline cartilage
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Lobar (secondary) Bronchi
- Supported by cartilage plates
- One lobar bronchus to each lobe
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Segmental (tertiary) Bronchi
- Supported by cartilage plates
- 10 in right lung, 8 in left
- Each ventilates a bronchopulmonary segment
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Bronchial Tree
- All divisions have elastic connective tissue which allows for expansion during inhalation and then recoils to expel air during exhalation
- Mucosa layer has smooth muscle to allow for constriction/dilation of airway
- Sympathetic innervation: causes bronchodilation
- Parasympathetic innervation: causes bronchoconstriction
- Pulmonary artery branches follow bronchial tree to alveoli
- Bronchial artery arises from thoracic aorta to provide bronchial tree with blood
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Bronchioles
- No cartilage
- Pulmonary lobule: part of lung ventilated by one bronchiole
- Divides into 50-80 terminal bronchioles
- Each terminal bronchiole divides into two or more respiratory bronchioles
- Respiratory bronchioles have alveoli budding off of them
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Alveoli
- 150 million in each lung
- Three types of cells:
- Squamous (type 1) alveolar cells: thin, broad; allow for rapid gas diffusion between alveoli and bloodstream
- Great (type II) alveolar cells: repair epithelium, secrete pulmonary surfactant (coats alveoli to prevent them from collapsing during exhalation)
- Alveolar macrophages (dust cells): phagocytose dust particles, then ride up mucociliary escalator to be swallowed
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Pleurae
- Fluid-filled cavity surrounding lungs
- Reduces friction when lungs expand
- Create pressure gradient to assist with lung inflation
- Prevent spread of infection from one organ to another
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Pulmonary Ventilation (breathing)
- Consists of repetitive respiratory cycles: one complete inspiration, one complete expiration
- Quiet respiration: quiet, effortless
- Forced respiration: deep, rapid (exercise)
- Depends on pressure difference between lungs and external environment
- Respiratory muscles change lung volume, which changes pressure
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