Anatomy and Physiology of the Respiratory System Notes
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NOTES NOTES ANATOMY & PHYSIOLOGY RESPIRATORY SYSTEM osms.it/respiratory-anatomy-physiology RESPIRATORY SYSTEM ▪ Upper respiratory tract ▫ Nose, pharynx, associated structures ▪ Lower respiratory tract ▫ Larynx, trachea, bronchi, lungs Respiratory system function ▪ Gas exchange between blood, atmosphere ▪ Protection against harmful particles, substances ▪ pH homeostasis ▪ Vocalization Conducting vs. respiratory zone ▪ Conducting zone ▫ Does not participate in gas exchange ▫ Nose to terminal bronchioles ▫ Function: inspire, warm, humidify, ﬁlter air before gas exchange ▫ Smooth muscle layer contains autonomic nervous system (sympathetic, parasympathetic nerves) ▫ Smooth muscle along trachea, ﬁrst few bronchial branches have beta-2adrenergic receptors ▫ Sympathetic nerves stimulate beta2-adrenergic receptors → ↑ airway diameter ▫ Parasympathetic nerves stimulate muscarinic receptors → ↓ airway diameter ▪ Respiratory zone ▫ Participates in gas exchange ▫ Lined with alveoli ▫ Terminal bronchioles–alveoli 588 OSMOSIS.ORG Figure 67.1 Respiratory system overview, categorized into upper, lower respiratory tracts.
Chapter 67 Respiratory Physiology: Anatomy & Physiology RESPIRATORY SYSTEM ANATOMY Nose ▪ Function: humidiﬁes, warms, ﬁlters inspired air; voice resonance chamber; houses olfactory receptors ▪ Nasal vibrissae (hairs) coated with mucus → traps large particles (e.g. dust, pollen) Nasal cavity ▪ Nasal cavity division ▫ Midline nasal septum: composed of septal cartilage, anteriorly ▫ Vomer bone: posteriorly ▪ Four paranasal sinuses (air-ﬁlled spaces inside bones) connected to nasal cavity ▫ Ethmoid, frontal, sphenoid, maxillary sinuses ▫ Function: warms, moistens inspired air; ampliﬁes voice; lightens skull ▪ Roof formed by ethmoid, sphenoid bones ▪ Floor formed by palate ▪ Two mucous membrane types ▫ Olfactory mucosa: olfactory epithelium containing smell receptors ▫ Respiratory mucosa: pseudostratiﬁed ciliated columnar epithelium containing goblet cells; secretes mucus containing lysozyme, defensins ▪ Nasal conchae ▫ Three mucosa-covered projections (superior, middle, inferior nasal conchae) of nasal cavity’s lateral wall ▫ Meatus: groove inferior to each conchae (superior, middle, inferior meatus) ▫ Function: ↑ turbulence inside cavity to ﬁlter, humidify inspired air; reabsorb heat, moisture during nasal expiration Palate ▪ Separates nasal cavity from oral cavity ▫ Hard palate: anterior portion supported by palatine bones ▫ Soft palate: posterior portion not supported by bones ▫ Soft palate, uvula move together; forms valve that closes nasopharynx when swallowing (prevents food from entering nasopharynx) Pharynx ▪ AKA throat ▪ Passageway connecting nasal cavity, larynx, oral cavity, esophagus ▪ Nasopharynx: region connecting nasal cavity to pharynx ▫ Posterior to nasal cavity, inferior to sphenoid bone, superior to soft palate ▫ Air-only passageway ▫ Pharyngeal tonsils (adenoids); located on posterior wall; traps, kills pathogens ▫ Pseudostratiﬁed ciliated epithelium (part of mucociliary escalator) ▪ Oropharynx: region connecting pharynx to oral cavity ▫ Posterior to oral cavity, continuous with isthmus of fauces ▫ Soft palate superior, epiglottis inferior ▫ Food, air passageway ▫ Pseudostratiﬁed columnar epithelium of nasopharynx → stratiﬁed squamous epithelium ▫ Palatine tonsils located on lateral walls ▫ Lingual tonsils cover posterior tongue ▪ Laryngopharynx: part of pharynx continuous with larynx (voice box) ▫ Food, air passageway ▫ Stratiﬁed squamous epithelium ▫ Epiglottis anterior, esophagus posterior Larynx ▪ Cartilage, connective tissue framework ▫ Connects pharynx to trachea; houses vocal cords, epiglottis (cartilage ﬂap atop larynx that seals airway off when swallowing—prevents food entering larynx) ▪ Location ▫ Third to sixth cervical vertebra ▫ Superior: hyoid bone ▫ Inferior: trachea ▪ Function ▫ Routes food, air into appropriate passageway; voice production ▪ Histology ▫ Superior portion: contacts food; stratiﬁed squamous epithelium ▫ Inferior portion: below vocal folds; pseudostratiﬁed ciliated columnar epithelium (part of mucociliary escalator) OSMOSIS.ORG 589
Figure 67.2 Anatomy of upper respiratory tract, surrounding structures. ▪ Contains nine cartilages ▫ Thyroid cartilage: large shield-shaped midline cartilage, produces laryngeal prominence (”Adam’s apple”) ▫ Cricoid cartilage: ring-shaped cartilage inferior to thyroid cartilage, superior to trachea ▫ Arytenoid, cuneiform, corniculate cartilages: form posterior, lateral larynx walls (arytenoid cartilages anchor vocal cords) ▫ Epiglottis: spoon-shaped cartilage is pulled superiorly to cover laryngeal inlet during swallowing (prevents food from passing through larynx) ▪ Vocal folds/ligaments ▫ Attach arytenoid cartilages to thyroid cartilage ▫ True vocal cords: sound production (function); composed of elastic ﬁbers; core of mucosal folds; appears white (avascularity) ▫ False vocal cords: superior to true vocal cords; does not participate in sound production; close glottis during swallowing (function) Trachea ▪ AKA windpipe ▪ Mainstem bronchi, airways ▪ Trachea ▫ Tube smooth muscle, connective tissue, C-shaped cartilage (provides support, 590 OSMOSIS.ORG maintains open passage for air) ▫ Connected by trachealis muscle ▫ Runs from larynx, divides into two main bronchi inferiorly at carina ▪ Layers (superﬁcial to deep) ▫ Mucosa: pseudostratiﬁed epithelium with goblet cells; mucociliary escalator ▫ Submucosa: connective tissue layer (supported by 16–20 C-shaped cartilage rings) ▫ Adventitia: connective tissue layer encasing cartilage rings Right & left mainstem bronchus ▪ Right mainstem bronchus ▫ Wider, more vertical ▫ Something accidentally inhaled → goes into right lung (more likely) ▪ Inside lungs ▫ Main bronchus subdivides into lobar bronchi → segmental bronchi → terminal bronchioles ▪ Trachea, ﬁrst three bronchial generations ▫ Wide, supported by cartilage rings ▪ Large airways lined by ciliated columnar cells, goblet cells (secrete mucus) ▫ Mucociliary escalator: mucus traps particles → ciliated columnar cells beat rhythmically → moves mucus, trapped particles towards pharynx → spit out/ swallowed
Chapter 67 Respiratory Physiology: Anatomy & Physiology Figure 67.3 Section of tracheal wall showing its histology. Stimulation by sympathetic nerves dilates airways, stimulation by parasympathetic nerves constricts airways. Histological changes as conducting tubes decrease ▪ Cartilage ▫ Cartilage amount ↓ while elastic ﬁbers ↑ (bronchioles contain no cartilage) ▪ Epithelium ▫ Mucosal epithelium changes from pseudostratiﬁed columnar → columnar → cuboidal ▫ Goblet cells, cilia ↓ (completely absent in bronchioles) ▪ Smooth muscle ↑ Bronchioles ▪ Narrow airways after ﬁrst three bronchial generations ▪ Terminal bronchioles: last part of terminal bronchioles, end of conducting zone ▪ Respiratory bronchioles: distal to terminal bronchioles, ﬁrst part of respiratory zone ▪ Terminal bronchiole → respiratory bronchiole → alveolar ducts → alveolar sac → alveoli Alveoli ▪ Alveolar wall ▫ Composed of a single simple squamous epithelium layer ▪ Elastic ﬁbers surround alveoli → allow lung expansion during inspiration, recoil during expiration ▫ Type I pneumocytes: primary gas exchange site; oxygen–carbon dioxide ▪ ▪ ▪ ▪ exchange occurs between alveolar gas, pulmonary capillary blood; thin walls, large alveoli surface-area maximizes gas exchange diffusion capabilities ▫ Type II pneumocytes: secrete surfactant (↓ surface tension within alveoli → eases expansion, prevents collapsing Alveolar macrophages phagocytize particles inside lungs → conducting bronchioles → mucociliary escalator Respiratory membrane ▫ Capillary, alveolar walls; basement membranes Alveolar pores connect adjacent alveoli Blood supply ▫ Pulmonary capillary networks Lungs ▪ Main respiration organs ▪ Right lung ▫ Three lobes: upper, middle, lower lobe ▪ Left lung ▫ Two lobes: upper, lower lobe ▪ Base of lungs rest on diaphragm ▪ Pleura: double-layered serosa covering lungs, pleural ﬂuid lining pleural cavity between two layers ▫ Parietal pleura: outer layer adherent to thoracic wall, superior surface of diaphragm ▫ Visceral pleura: inner layer adherent to external lung surface OSMOSIS.ORG 591
▪ Pulmonary circulation ▫ Pulmonary veins (anterior to main bronchi) bring oxygen-rich blood to lungs from heart ▫ Pulmonary arteries bring oxygen-poor systemic venous blood for oxygenation ▫ Low-pressure, high-volume circulation ▪ Bronchial circulation ▫ Bronchial arteries: provide oxygenated systemic blood to lung tissue ▫ Bronchial veins: drain deoxygenated venous blood from lungs (with pulmonary veins) ▫ High-pressure, low-volume circulation ▪ Innervation ▫ Pulmonary plexus ▫ Parasympathetic motor causes bronchoconstriction ▫ Sympathetic motor causes bronchodilation ▫ Visceral sensory ▫ Diaphragm innervated by phrenic nerve Figure 67.4 Trachea and lung anatomy. Numbered labels show sequence of airﬂow going into the airways from (trachea to alveoli). Figure 67.5 Alveolus structure. Gas exchange occurs at the blood-gas barrier. De-oxygenated blood from pulmonary arteries are oxygenated then sent to pulmonary veins. 592 OSMOSIS.ORG
Chapter 67 Respiratory Physiology: Anatomy & Physiology VENTILATION ▪ Ventilation (breathing): moving air in, out of lungs ▪ Oxygen pathway ▫ Air inhaled through nostrils → nasal cavity → pharynx → larynx → trachea → mainstem bronchus → conducting bronchioles → terminal bronchioles → respiratory bronchioles → alveolar duct → alveoli → capillary → body ▫ Carbon dioxide moves in reverse ▪ Airﬂow from atmosphere to lungs ▫ Higher pressure → lower pressure ▪ Muscle movement creates pressure gradient ▫ Primary respiration muscles: diaphragm, external intercostals, scalenes ▫ Forceful breathing: other muscles recruited ▪ Airﬂow resistance: function of respiratory passage diameter ▪ Passive inhalation: negative pressure inside body generated → moves air into lungs ▫ Diaphragm contracts downwards, chest muscles pull ribs outward → ↑ intrathoracic volume → ↓ intrathoracic pressure → air moved into lungs (air ﬂows down pressure gradient) ▪ Passive exhalation: ↑ intrathoracic pressure generated → moves air out of lungs ▫ Diaphragm relaxes (returns to resting position), external intercostal muscles relax, thoracic cage recoils → elastic lung recoil → ↓ intrathoracic volume → ↑ intrathoracic pressure → air pushed out of lungs OSMOSIS.ORG 593
Osmosis High-Yield Notes
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