Respiratory Physiology (MDSC3102) PDF

Respiratory Physiology (MDSC3102) Andre Bowers, Ph.D. Physiology Section, UWI Mona Objectives ❑ Overview of respiration ❑ Identify internal & external ventilation ❑ Gas laws ❑ Mechanisms of gas transport ❑ Pulmonary pathologies Respiratory System ❑ Consists of tubes and sacs and is responsible for t...

Respiratory Physiology (MDSC3102) Andre Bowers, Ph.D. Physiology Section, UWI Mona Objectives ❑ Overview of respiration ❑ Identify internal & external ventilation ❑ Gas laws ❑ Mechanisms of gas transport ❑ Pulmonary pathologies Respiratory System ❑ Consists of tubes and sacs and is responsible for the exchange of gases: ✓ filters incoming air and transports it into the microscopic alveoli where gases are exchanged. ❑ Endpoint: provides O2 to cells for ATP hydrolysis – Cellular respiration. ❑ Rate of respiration driven by oxygen debt: ✓ proportional to energy needs. Respiratory System ❑Principal role is the downstream flow of O2 to the lungs blood respiring tissues. ❑CO2 is transported upstream from the tissues blood lungs expired. ❑Physical barrier – separation of external and internal environs. ❑Metabolic functions in producing several substances with hormone-like functions. “Respiratory Tract” - two STRUCTURAL groups ❑ The Upper Respiratory Tract ❑ The Lower Respiratory Tract ✓ Nose ✓ Larynx ✓ Nasal cavity ✓ Trachea ✓ Sinuses ✓ Bronchial Tree ✓ Pharynx ✓ Lungs Structures of the respiratory system Bones, muscles & membranes of respiratory system. Respiratory Tract Two FUNCTIONAL groups ❑ Conducting zone – ❑ Respiratory zone interconnecting tubes and cavities ✓ Nose ✓ Pharynx ✓ Larynx ✓ Trachea ✓ Bronchi - site of gas exchange ✓ Respiratory bronchioles ✓ Alveolar Ducts ✓ Alveoli Respiratory epithelium Air – composition + partial pressure Conducting zone ❑ Begins with ventilation – air transit into and out of lungs ✓ determined by integrity of conducting airways. ✓ includes the nasopharynx, oropharynx, larynx and tracheobronchial tree ❑ Perfusion occurs constitutively – transport of blood through the lungs ✓ facilitates exchange between blood and lungs. Conducting zone The nose ❑ Two distinct segments: ✓ internal ✓ External ❑Provides entry into respiratory system. ✓ initial filter of inspired air The nose ❑External segment supported by bone and cartilage: ✓ mucous-lined membrane. ❑Internal portion - large cavity in the skull. ✓ connects anteriorly to external nose ✓ posteriorly to throat. Internal nose ✓ mucosal layers – increases surface area ✓ divided medially by the nasal septum: ▪ nasal conchae membrane – give rise to 4 air channels: ▪ mucosal surface + ‘superficial’ blood supply ▪ warms airs + preserves lung Nasal Cavity ▪ modulate air flow consistency ▪ increases SA of epithelium ▪ increases filtering efficiency ❑Trapped particles carried to pharynx: ✓ ciliary action. ✓ gastric microbe removal Paranasal Sinuses nose Paranasal Sinuses ❑Air-filled spaces within the sphenoid, ethmoid, frontal and maxillary bones. ❑Mucous membrane-lined, continuous with the nasal cavity. ❑Physiological advantage: reduce the weight of the skull: ✓ resonant chamber - affect voice quality. The Pharynx ❑ Throat – funnel-shaped tube and passageway for food and air: ✓ lies posteriorly to the nasal cavity, oral cavity and larynx ✓ anteriorly to the cervical vertebra. ❑ Divided into 3 units: ✓ nasopharynx – uppermost portion ✓ oropharynx – middle portion ✓ laryngopharynx – lowermost portion The Larynx ❑ An enlargement in the airway: ✓ superior to the trachea ✓ inferior to the pharynx. ❑ Framework of muscles and cartilage: ✓ bound by elastic tissue. ❑ Occupied by the vocal cords. ❑ Aids in keeping particles out of the trachea. The Epiglottis ❑Leaf-shaped cartilaginous projection: ✓ covered by mucous membrane. ✓ posterior to root of tongue. ✓ contains extra-lingual taste buds – laryngeal face: o potentially protective: reflexively protects airway from noxious biological + chemical agents The Epiglottis ❑ Prevents food from entering the trachea. ❑ Breathing - pointed upwards underside pharynx ❑ Swallowing – elevation & forward movement of larynx + pharynx by suprahyoid muscle. ✓ epiglottis positioned against larynx ✓ windpipe closed Epiglottis - Position and Function The Epiglottis Vocal Cords Vocal cords o Situated inside the larynx: ✓ two pairs of folds of muscle & connective tissues ✓ covered by mucous membrane. ✓ horizontally stretched, front to back across the larynx. o The upper pair is the false vocal cords. Vocal cords ❑The lower pair is the true vocal cords. ❑Produce quasi-periodic vibrations during speech: ✓ modulates air expelled from lungs. ❑Changing tension controls pitch: ✓ loudness - > force of air vibrating vocal cords. The Vocal Cords ❑ Normal breathing - abduction of the vocal cords + glottis - triangular slit. ❑ Swallowing - false vocal cords + epiglottis are closed off from the glottis. Respiratory Tree ❑Connects the external environment to the exchange portion of the lungs: ✓ similar to the vascular component ✓ larger airway - > flow volume + > velocity of flow: ▪ small cross-sectional area ✓ smaller airway - lower flow + velocity ▪ larger cross-sectional area Respiratory Tree o The Respiratory Tree: ✓ upper respiratory tract - large conductive tube ✓ lower respiratory tract - starts after larynx & divides several times over & ends in the smallest regions which form the exchange membranes Trachea Primary bronchi Secondary bronchi conductive portion Tertiary bronchi Bronchioles Terminal bronchioles Respiratory bronchioles with start of alveoli out-pouches exchange portion Alveolar ducts with out-pouchings of alveoli Trachea ❑ Tubular passageway for air, located anterior to the oesaphagus. ❑ Extends from larynx - 5th thoracic vertebra: ✓ divides into right + left bronchi ❑ Lined with ciliated mucous membrane: ✓ goblet cells - serve to trap incoming particles ❑ Tracheal wall is supported by 20 incomplete cartilaginous rings. The Trachea THE TRACHEA The Bronchi o Forms the two main air passages into the lungs. o They are composed of the: o Right primary bronchus - leads to right lung. o left primary bronchus - leads to left lung. Fig. 9 The Bronchi Bronchial Tree o Branched tubes - leads from trachea to alveoli. o Begins with two primary bronchi, each leading to a lung. o The right and left primary bronchi give rise to bronchioles: ✓ give rise to alveolar ducts. ✓ terminate in alveoli. o It is through the thin epithelial cells of the alveoli that gas exchange between the blood and air occurs. The bronchial tree & divisions of the lungs The Lungs o Paired, spongy, cone-shaped structures in thorax: ✓ separated medially by the mediastinum ✓ enclosed by the diaphragm and thoracic cage. o Enclosed by bi-layers of serous membrane, collectively known as pleural membrane: ✓ Parietal Pleura: - outer layer attached to the thoracic cavity. ✓ Visceral Pleura: - inner layer directly covers the lung. Cross- thoracic cavity Exchange portion: ❑Gaseous exchange occurs in the respiratory airways across the alveoli-capillary membrane. ❑Air transported to pulmonary circulation. ❑Determinants: perfusion pressure partial pressure of incoming air air pressure within the alveoli + conducting zones. Upper & lower respiratory tract and exchange surface Tract divisions & absorptive potential - upper + lower respiratory tract Functional anatomy_c o Anatomical arrangement creates and transmit a pressure gradient: ✓ Underscores gas flow – driven by: attachments of the muscles to ribs (and overlying tissues). attachment of the diaphragm to the base of the lungs and associated pleural membranes. cohesion of the parietal membrane to the visceral membrane. expansion & recoil of the lung and alveoli with the movement of the overlying structures. Pleural Membrane oCohesion between parietal and visceral layers is due to serous fluid in the pleural cavity: fluid creates an attraction between the two sheets of membrane – 30 mL as the parietal membrane expands due to expansion of the thoracic cavity - visceral membrane pulled with it pulls the underlying structures - expand disruption of the integrity of the pleural membrane will result in a rapid equalization of pressure and loss of ventilation function – pneumothorax (collapsed lung) Fig. 14 Influence of the diaphragm on pleural space Summary – main pulmonary functions Fig. 15 Structure of the alveoli and respiratory bronchioles Flow diagram respiratory system