Respiratory System PDF

RESPIRATORY SYSTEM Consist of structures used to acquire oxygen and remove carbon dioxide from the blood Oxygen is required for the body’s cells to synthesize ATP and Carbon Dioxide is the by product of ATP production Includes the following structures ○ UPPER RES...

RESPIRATORY SYSTEM Consist of structures used to acquire oxygen and remove carbon dioxide from the blood Oxygen is required for the body’s cells to synthesize ATP and Carbon Dioxide is the by product of ATP production Includes the following structures ○ UPPER RESPIRATORY TRACT External Nose Nasal Cavity Pharynx Larynx ○ LOWER RESPIRATORY TRACT Trachea Bronchi Lungs 2 REGIONS ○ UPPER RESPIRATORY TRACT – nose to the larynx ○ LOWER RESPIRATORY TRACT - trachea to the alveoli 2 ZONES ○ CONDUCTING ZONE – structures from the nose to the smallest air tubes within the lungs where ventilation happens ○ RESPIRATORY ZONE – within the lungs and includes some small air tubes and the alveoli where gas exchange occurs FUNCTIONS OF THE RESPIRATORY SYSTEM Respiration/Breathing is critical for homeostasis 2 Aspects include: ○ VENTILATION: movement of air into and out of the lungs ○ RESPIRATION: diffusion of gases across plasma membranes PULMONARY RESPIRATION (external) movement of gases between atmospheric air in the lungs and the blood SYSTEMIC RESPIRATION (internal) movement of gases between blood and the body’s cells FUNCTIONS OF THE RESPIRATORY SYSTEM REGULATION OF THE BLOOD PH – through the production and excretion of blood CO2 PRODUCTION OF CHEMICAL MEDIATORS – lungs produce ACE which is an important component for BP regulation VOICE PRODUCTION – air moving through the vocal folds makes sound and speech OLFACTION – when airborne molecules are received in the smell receptors of the nasal cavity PROTECTION- prevents MOs from entering and removing them from the respiratory surfaces NOSE AND NASAL CAVITY External nose is the visible structure that forms the prominent feature of the face ○ Composed of hyaline cartilage plates ○ Nasal bones and the extensions of the frontal and maxillary bones constitute the bridge of the nose Nasal Cavity is the open chamber inside the nose where air first enters the respiratory system ○ Nares/ nostrils – anterior external openings ○ Choanae – posterior openings into the pharynx ○ Vestibule – lines with stratified squamous epithelium, the anterior region of the nasal cavity  Hard Palate – floor of the nasal cavity that separates it from the oral cavity ○ Covered by highly vascular mucous membrane that helps warm and humidify inspired air Nasal Septum – separates the nasal cavity into left and right halves ○ Anterior - composed of cartilage ○ Posterior – vomer bone and ethmoid bone plate Conchae – 3 lateral bony ridges (like a conch) previously called turbinate bones ○ Between each concha, a meatus (tunnel) is formed: paranasal sinuses and nasolacrimal duct FUNCTIONS OF THE NASAL CAVITY Serves as passageway for air Cleans the air Humidifies and warms the air Contains the olfactory epithelium Helps determine voice sound PHARYNX Connects the nasal cavity and mouth to the larynx and esophagus inferiorly Common passageway for air, food, and drink Commonly called the throat There are 3 regions: ○ Nasopharynx: air only posterior to the choanae and superior to the soft palate soft palate separates the nasopharynx from the oropharynx ○ Oropharynx: air and food soft palate to the epiglottis ○ Laryngopharynx: primarily food and drink epiglottis to the esophagus LARYNX (VOICE BOX) Anterior part of the throat, from the base of the tongue to the trachea The three functions of the larynx are ○ Maintains an open passageway for air movements ○ Prevents swallowed materials from entering the larynx and lower respiratory tract (epiglottis –cartilage that cover the laryngeal inlet during swallowing & closure of the vocal cords) ○ Produces sound for speech ○ Protects the lower respiratory tract from foreign materials VOCAL CORDS Two pairs of ligaments False vocal cords (vestibular folds) ○ Superior mucosal folds ○ Have no part in sound production True vocal cords (vocal folds) ○ Inferior mucosal folds composed of elastic fibers ○ The medial opening between them is the glottis ○ They vibrate to produce sound as air rushes up from the lungs ○ Laryngitis: Inflammation of the vocal folds SOUND PRODUCTION Sound: Vibration of the vocal folds as air moves past them Loudness: depends on the amplitude of the vibration, which is determined by the force at which the air rushes across the vocal cords Pitch: determined by the length and tension of the vocal cords, which changes the frequency of the vibrations Sound is “shaped” into language by action of the tongue, lips, teeth, and other structures The pharynx resonates, amplifies, and enhances sound quality TRACHEA Descends from the larynx through the neck to the fifth thoracic vertebra Composed of dense regular connective tissue and smooth muscle reinforced with 15-20 C-shaped rings of hyaline cartilage, which protect the trachea and keep the airway open The mucous membrane lining the trachea is made up of goblet cells and pseudostratified ciliated columnar epithelium ○ Goblet cells produce mucus It ends by dividing into the two primary bronchi MAIN BRONCHI/ PRIMARY BRONCHI The right and left bronchi are formed by the division of the trachea Carina – a ridge of cartilage where the trachea divides into two bronchi ○ Landmark for X-rays ○ Sensitive to mechanical stimulation for a strong cough reflex Right primary bronchus is wider, shorter and more vertical than the left ○ Common site for an inhaled object to become lodged By the time that incoming air reaches the bronchi, it is warmed, cleansed and saturated with water vapor TRACHEOBRONCHIAL TREE Consists of the trachea and the network of air tubes in the lungs The smaller bronchi continue getting smaller until they terminate into microscopic tubes and sacs 4 air passageways from largest to smallest: ○ Lobar Bronchi (secondary bronchi) – with cartilage plates and ciliated columnar epithelium, enters the lobes of the lungs ○ Segmental Bronchi (tertiary bronchi) – supplies the segments within the lobes of the lungs; with more abundant smooth muscles than cartilage ○ Bronchioles – less than 1mm diameter, lines with ciliated simple columnar epithelium ○ Terminal Bronchioles – no cartilage in their walls but with prominent smooth muscles As air passageways become smaller, structural changes occur ○ Cartilage support structures decrease ○ Amount of smooth muscle increases ○ Epithelium types change Terminal bronchioles are mostly smooth muscle with no cartilage, which allows the bronchioles to alter their diameter when a change in air flow is needed (i.e. during exercise) CHANGES IN AIR PASSAGEWAY DIAMETER Bronchi and bronchioles are capable of changing diameter The smooth muscles are able to relax (bronchodilation) and contract (bronchoconstriction) The flow of air decreases when the resistance to airflow is increased ALVEOLI Terminal bronchioles divide into respiratory bronchioles, which have a few attached alveoli ○ Alveoli – small air filled chambers where gas exchange between the air and blood takes place Respiratory bronchioles lead to alveolar ducts, then to terminal clusters of alveolar sacs composed of alveoli Approximately 300 million alveoli ○ Account for most of the lungs’ volume ○ Provide tremendous surface area for gas exchange ~7 generations of branching occur from the terminal bronchioles to the alveolar ducts ALVEOLI Sites of pulmonary respiration Small, air-filled chambers where the air and blood come into close contact with each other Largest to smallest branches : ○ Respiratory bronchioles > alveolar ducts > alveolar sacs Contains elastic fibers that allow expansion during inspiration and recoil during expiration Although the alveoli and respiratory bronchioles is not ciliated, the debris from air can be removed by macrophages 2 types of cells form the alveolar wall ○ Type I Pneumocytes – thin squamous epithelial cells (90% of alveolar surface) most of the gas exchange between alveolar air and the blood takes place through these cells ○ Type II Pneumocytes – round/ cube secretory cells that produce surfactants to support alveolar expansion during inspiration THE RESPIRATORY MEMBRANE Location of pulmonary respiration The membrane is extremely thin and includes the following components: ○ Alveolar cell layer ○ Capillary endothelial layer ○ Interstitial space between the alveolar layer and the capillary layer Where gas exchange between air and blood occurs Consists of: ○ Thin layer of fluid lining the alveolus ○ Alveolar epithelium ○ Basement membrane of the alveolar epithelium ○ A thin interstitial space ○ Basement membrane of the capillary endothelium ○ The capillary endothelium THORACIC WALL AND MUSCLES OF RESPIRATION  Thoracic wall consists of: ○ Thoracic vertebrae ○ Costal cartilages ○ Sternum ○ Associated muscles LUNGS Principal organs of respiration Base rest on diaphragm and the apex extends superiorly to ~2.5 cm above the clavicle Right lung has 3 lobes, while the left has only 2 lobes BLOOD SUPPLY TO THE LUNGS Lungs are perfused by two circulations: pulmonary and bronchial ○ Pulmonary circulation Pulmonary arteries: supply deoxygenated systemic blood to be oxygenated Ultimately feed into the pulmonary capillary network surrounding the alveoli Pulmonary veins: carry oxygenated blood from lungs back to the heart ○ Bronchial circulation Bronchial arteries: provide systemic oxygenated blood to the lung tissue Supply all lung tissue except the alveoli Bronchial veins: carry the deoxygenated blood back to the heart PLEURA  Thin, double -layered serous membranes Parietal pleura ○ Covers the thoracic wall, diaphragm, and mediastinum Visceral pleura ○ Covers the external lung surface Pleural cavity ○ Negative pressure space between the parietal and visceral pleura Pleural Fluid ○ Fills the pleural cavity ○ Made by the pleural membranes ○ Serves as a lubricant ○ Holds the pleural membranes together VENTILATION Inspiration: movement of air into the lungs ○ Muscles involved are the diaphragm and those that elevate the ribs and sternum ○ As the diaphragm and other muscles of inspiration contract and the rib cage rises and thoracic volume increases Expiration: movement of air out of the lungs ○ Muscles actively involved are those that depress the ribs and sternum (usually only with forceful expiration) ○ Largely a passive process ○ Muscles of inspiration relax, the rib cage descends due to gravity and the thoracic cavity volume decreases Pressure changes in the thoracic cavity change air pressure in the lungs, which in turn causes ventilation ○ largest change in thoracic volume is due to the diaphragm MUSCLES OF RESPIRATION  Function of the muscles of respiration is to change the volume of the thoracic cavity that allows for air to flow into and out of the lungs Inspiration ○ Diaphragm ○ External Intercostals ○ Pectoralis minor ○ Scalene muscles Expiration ○ Internal intercostals ○ Transverse thoracis PRESSURE CHANGES AND AIRFLOW Physical Principles Influencing Pulmonary Ventilation Air flows from areas of higher to lower pressure ○ If pressure is higher at one end of a tube (P1) than at the other (P2), air will flow down its pressure gradient Changes in volume result in changes in pressure ○ As volume increases in a closed container the pressure decreases or as volume decreases pressure increases ○ This inverse relationship is known as Boyle’s law Changes in tube diameter result in changes in resistance ○ Poiseuille’s law: resistance (R) to airflow is proportional to the diameter (d) of a tube raised to the fourth power (d4) LUNG RECOIL  Tendency for an expanded lung to decrease in size due to ○ Elastic fibers in the connective tissue ○ Surface tension Two factors keep lungs from collapsing ○ Surfactant ○ Pleural Pressures SURFACTANT Surface acting agent Mixture of lipoprotein molecules Acts in reducing surface tension in the alveoli ○ Attraction of water molecules to each other Surfactant reduces the surface tension in alveoli by 10-fold PLEURAL PRESSURE Pressure in the pleural cavity ○ When pleural pressure is less than alveolar pressure alveoli expand Sub-atmospheric pleural pressure is caused by ○ Removal of fluid from the pleural cavity ○ Lung recoil MEASUREMENT OF LUNG FUNCTION PULMONARY VOLUMES AND CAPACITIES ○ Spirometry is the process of measuring volumes of air that move into and out of the respiratory system TIDAL VOLUME - normal volume of air inspired and expired with each breath (approx. 500mL) INSPIRATORY RESERVE VOLUME – the amount of air that can be inspired forcefully after a normal inspiration (approx. 3L at rest) EXPIRATORY RESERVE VOLUME – the amount of air that can be forcefully expired after a normal expiration (approx. 1.1L at rest) RESIDUAL VOLUME – volume of air still remaining in the respiratory passages and lungs after the most forceful expiration (approx. 1.2L) PULMONARY CAPACITIES – sum of two or more pulmonary volumes  ○ INSPIRATORY CAPACITY – tidal volume plus the inspiratory reserve volume or the amount of air a person can inspire maximally after a normal expiration (approx. 3.5L) ○ FUNCTIONAL RESIDUAL CAPACITY – expiratory reserve volume plus the residual volume or the amount of air remaining in the lungs at the end of a normal expiration (approx. 2.3L at rest) ○ VITAL CAPACITY – sum of the inspiratory reserve volume, tidal volume and the expiratory reserve volume / maximum volume of air a person can expel from the respiratory tract after a maximum inspiration (approx. 4.6L) ○ TOTAL LUNG CAPACITY – sum of inspiratory and expiratory reserve volumes plus the tidal volume and residual volume (approx. 5.8L) FORCED VITAL CAPACITY – functional measure of lung performance FORCED EXPIRATORY VOLUME in 1 SECOND (FEV1) – amount of air expired within the first second of the test ○ Lower FEV means the disease has worsened MINUTE VOLUME ○ Respiratory Rate – number of breaths per minute ○ Measure of the amount of air moved through the respiratory system per minute ○ TIDAL VOLUME X RESPIRATORY RATE MINUTE VENTILATION Minute Ventilation ○ equals tidal volume (~500mls) times respiratory rate (~12 breaths/min.) ○ Average ~ 6 L/min ○ Only measures movement of air into and out of the lungs, not amount of air available for gas exchange Dead space ○ Areas of the respiratory system where gas exchange does not take place  ○ Includes the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles (~150 mLs) ○ Nonfunctional alveoli can also contribute, but are rare in healthy individuals LUNG COMPLIANCE Measurement of the ease with which the lungs and thorax expand Volume increases for each unit of pressure change in alveolar pressure ○ Liters (volume of air)/Centimeter of H2O (pressure) In a normal person = 0.13 L/cm H2O ○ Higher than normal compliance = less resistance to lung and thorax expansion Emphysema ○ Lower than normal compliance = more resistance to lung and thorax expansion Pulmonary fibrosis, infant respiratory distress syndrome, pulmonary edema, asthma, bronchitis, and lung cancer ALVEOLAR VENTILATION Alveolar ventilation (VA) ○ volume of air available for gas exchange Slow, deep breathing increases AVR and rapid, shallow breathing decreases AVR