Human Anatomy and Physiology: The Respiratory System PDF

Human Anatomy and Physiology Elaine N. Marieb and Suzanne M. Keller The Respiratory System  Learning Outcomes 1. Describe the structure and function of each component of the respiratory system 2. List the competing pressures involved in respiration, and describe how thes...

Human Anatomy and Physiology Elaine N. Marieb and Suzanne M. Keller The Respiratory System  Learning Outcomes 1. Describe the structure and function of each component of the respiratory system 2. List the competing pressures involved in respiration, and describe how these pressure gradients are created 3. Describe the mechanics of breathing and how ventilation is related to changes in pressure 4. Describe how respiration can be assessed, Lung Volumes and Capacities, and predict the effects of disease states upon respiratory function 5. Describe and Explain how O2 and CO2 are transported in blood 6. Explain the neuronal mechanisms by which the body controls breathing, and the factors that modulate these processes Breathing and Respiration Respiration is the exchange of gases between the atmosphere, blood, and cells Combination of 4 processes is required: Ventilation (breathing) External (pulmonary) respiration Transport of respiratory gases Internal (tissue) respiration The cardiovascular system assists the respiratory system by transporting gases Components of the Respiratory System Structurally, the components of the respiratory system are divided into 2 parts: Upper respiratory system Lower respiratory system Functionally, the components of the respiratory system are divided into 2 functional zones: Conducting zone Respiratory zone https://sketchfab.com/3d-models/human-respiratory-system-review- 250911151757489da1cf5501b791f363 Structures of the Respiratory System The upper respiratory system consists of the nose, pharynx, larynx, and associated structures The lower respiratory system consists of the trachea, bronchi, and lungs The Respiratory System – Functional Zones Conducting Zone Respiratory Zone No gas exchange Site of gas exchange Provides rigid conduits (ducts) for air Consists of respiratory bronchioles, to reach the sites of gas exchange alveolar ducts, and alveoli (Inside the (passageway for air to move in and lung) out the lung) These thin-walled structures allow Consist of the nose, nasal cavity, inhaled oxygen (O2) to diffuse into the pharynx, larynx, trachea, bronchi, and lung capillaries in exchange for carbon terminal bronchiole dioxide (CO2)  Anatomy of the Nose and Nasal Cavity The Nose is the usual passageway for air into and out of the respiratory tract The air passes through the two nostrils Hair inside the nostrils helps block the entry of the dust and other large particles carried in the air Nasal cavity & Nasal septum The nasal cavity is the hollow space behind the nose Within the skull, there are two nasal cavities that are separated by the nasal septum Anatomy of the Nose and Nasal Cavity Paranasal Sinuses are air-filled cavities that open into the nasal cavities, maxillary sinus, ethmoidal sinus and frontal sinus and sphenoid sinus Their functions are: lighten the skull provide resonance for the voice Pharynx The pharynx is the space behind the oral cavity (mouth), nasal cavity, and larynx. It is also known as the throat, a common passageway for both food and air, provides a resonating chamber for speech sounds, and houses the tonsils Divided into three regions: 1. Nasopharynx: area at the back of the nasal cavity 2. Oropharynx: area at the back of the oral cavity 3. Laryngopharynx: area at the back of the larynx Nasopharynx Continuous with the lining of the nose and consists of strictly an air passageway, Lined with pseudo-stratified columnar ciliated epithelium with goblet cells It closes during swallowing to prevent food from entering the nasal cavity (Strictly air passageway) The pharyngo-tympanic or Eustachian (auditory) tubes open into the lateral walls (Link pharynx with middle ear) Oropharynx & Laryngopharynx Oropharynx, lined by stratified squamous epithelium Extends inferiorly from the level of the soft palate to the epiglottis Opens to the oral cavity via an archway called the Isthmus of the fauces (back of the mouth) A common passageway for food and air Laryngopharynx, formed by stratified squamous epithelium Extends from the oropharynx above and continues as the esophagus below, with the larynx lying anteriorly  Larynx The larynx (voice box) is a passageway that connects the pharynx and trachea Made up of muscles and cartilages surrounded by elastic tissue The larynx contains vocal folds, which produce sound when they vibrate Composed of irregularly shaped cartilages attached by ligaments: thyroid cartilage (Largest one, Adams apple) Hyaline cricoid cartilage Cartilage arytenoid cartilages epiglottis Elastic Fibrocartilage Cuneiform cartilages Elastic Cartilage Structures of Voice Production The vocal ligaments attach the arytenoid cartilage to the thyroid cartilage in the larynx. The vocal ligament is composed of elastic fibers that form mucosal folds called true vocal cords (mucous membrane) The medial opening between them is the glottis (between vocal cords) The false vocal cords (Thick mucous membranes), mucosal fold are superior to the true vocal cords and have no part in the sound production Larynx The functions of the larynx are Production of sounds: determined by length, tightness, and vibrations of the vocal cords Protection of the lower respiratory tract: during swallowing, the epiglottis closes, ensuring food moves down the esophagus and not the trachea Passageway for air: connects the pharynx to the trachea Humidifying, filtering & warming: these continue as inspired air travels through the larynx Conducting Zone: Trachea Trachea (windpipe) is a flexible and mobile tube extending from the larynx to the primary bronchi. Composed of three layers Mucosa: made up of goblet cells and ciliated epithelium Submucosa: connective tissue deep to the mucosa containing seromucous glands Adventitia: outermost layer made of C- shaped rings of hyaline cartilage Conducting Zone: Bronchi and Subdivisions (bronchial tree) At the superior border of the 5th thoracic vertebra, the trachea branches into a right primary bronchus that enters the right lung and a left primary bronchus that enters the left lung As conducting tubes become smaller, structural changes occur: Cartilage support structures change Epithelium types change Amount of smooth muscle increases Conducting Zone: Bronchi and Subdivisions (bronchial tree) Upon entering the lungs, the primary bronchi further divide to form smaller and smaller diameter branches. The terminal bronchioles are the end of the conducting zone Terminal bronchioles: Consist of cuboidal epithelium Have a complete layer of circular smooth muscle Lack cartilage support and mucus- producing cells Conducting and Respiratory Zones Respiratory Zone: Bronchi and Subdivisions Defined by the presence of alveoli; begins as terminal bronchioles feed into respiratory bronchioles 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 It provides tremendous surface area for gas exchange Alveolar Cells There are two types of alveolar cells A single layer of type I epithelial cells, Permit gas exchange by simple diffusion Type II cells secrete surfactant (Mix of lipid and protein, reduce surface tension of fluids in lung, and help air sac(spaces) in alveoli stable and not collapse during exhale) Respiratory Membrane This air-blood barrier is composed of: 1. A layer of type I and type II alveolar cells and associated alveolar macrophages that constitute the alveolar wall 2. An epithelial basement membrane underlying the alveolar wall 3. A capillary basement membrane that is often fused to the epithelial basement membrane 4. The capillary endothelium Lungs Lungs occupy all of the thoracic cavity except the mediastinum. The lungs are enclosed and protected by the pleural membrane. Root (hilum): site of vascular and bronchial attachments Costal surface: anterior, lateral, and posterior surfaces in contact with the ribs Lobes and Fissures of the Lungs Blood Supply to the Lungs Blood enters the lungs via the pulmonary arteries (pulmonary circulation) and the bronchial arteries (systemic circulation) Blood exits the lungs via the pulmonary veins and the bronchial veins. Bronchial arteries supply all lung tissue except the alveoli (alveoli get deoxygenated blood from the pulmonary artery) Ventilation-perfusion coupling (the ratio of alveolar ventilation, VA, to pulmonary blood flow, Q) Vasoconstriction in response to hypoxia diverts blood from poorly ventilated areas to well-ventilated areas. Pulmonary Ventilation (breathing) In pulmonary ventilation, air flows between the atmosphere and the alveoli of the lungs because of alternating pressure differences created by the contraction and relaxation of respiratory muscles Inhalation Exhalation Pressure changes that drive inhalation and exhalation are governed, in part, by Boyle’s Law  The volume of a gas varies inversely with its pressure Pressure Changes in Pulmonary Ventilation Negative respiratory pressure is less than Patm Positive respiratory pressure is greater than Patm Intrapulmonary pressure (Palv): pressure within the alveoli Intra-pleural pressure (Pip): pressure within the pleural cavity Pneumothorax (the presence of air or gas in the cavity between the lungs and the chest wall) Normal  Inhalation/ Inspiration Inhalation is the movement of air from the external environment, through the airways, and into the alveoli 1. Inhalation begins with the onset of contraction of the diaphragm 2. The External intercostal muscles contract and pull the rib cage upward 3. Size of the thorax increases 4. Volume of the lung increased 5. The pressure in the lungs decreases and drops below atmospheric pressure 6. Air rushes in to fill the lungs until pressure is balanced Exhalation/Expiration Exhalation is the movement of air out of the lungs, through the airways, to the external environment during breathing The diaphragm muscle relaxes and returns to its domed shape The external intercostal muscles that relax. The internal intercostal muscles are contracted during exhalation Size of the thorax decreases Volume of the lungs decreased Pressure in the lungs increased Exhaled air is rich in carbon dioxide  Lung Volumes and Capacities FEV1/VC (~ 80%) is the percentage of VC exhaled in 1 sec COPD (Emphysema and Chronic Bronchitis) COPD is the irreversible decrease in the ability to force air out of the lungs; features in common: More than 80% of patients are smokers Dyspnea (Shortness of Breath), which gets worse Coughing and frequent infections Most develop respiratory failure: hypoventilation + acidosis + hypoxemia Emphysema: permanent enlargement of the alveoli and destruction of their walls; ↑ resistance Chronic Bronchitis: airways become inflamed with excessive mucus production + frequent infections Asthma Asthma is a reversible obstructive airway disease characterized by episodes of coughing, dyspnea, wheezing, chest tightness, inflammation, inflated alveoli, and excess mucus production. Allergic asthma: inflammation with an immune component (subset of T lymphocyte) Inflamed and thickened airways aggravated by bronchospasm (↓ air flow) Treatment: bronchodilators and inhaled steroids External and Internal Respiration During external respiration, oxygen will diffuse from the alveoli into the pulmonary capillaries CO2 moves in the opposite direction During internal respiration, oxygen will diffuse from the systemic capillaries into the tissue CO2 moves in the opposite direction  Gas Exchange Interactions Animation: Gas Exchange Transport of Oxygen and Carbon Dioxide Oxygen: 1.5% of the O2 is dissolved in the plasma 98.5% of the O2 is carried by hemoglobin (Hb) Carbon dioxide: 10% of the CO2 is dissolved in the plasma 20% of the CO2 is carried by Hb inside red blood cells as carbaminohemoglobin 70% of the CO2 is transported as bicarbonate ions (HCO3)  Transport of Oxygen and Carbon Dioxide Interactions Animation: Gas Transport Factors Affecting the Affinity of Hb for O2 The rate in which hemoglobin binds and releases oxygen is regulated by: PO2 pH Temperature 1 2 BPG 3 Type of Hb Oxygen-hemoglobin dissociation curve showing the relationship between hemoglobin saturation (percent) and PO2, at normal body temperature Summary of Chemical Reactions During Gas Exchange Control of Breathing – Respiratory Centers Medullary Respiratory Center 1. Neurons of the dorsal respiratory group (DRG) primarily fire during inspiration Inspiratory neurons stimulate the phrenic nerve and the diaphragm contracts – thoracic volume increases – inspiration 2. The ventral respiratory group (VRG) of the medulla oblongata has expiratory and inspiratory actions – The respiratory rhythm generator is located in the pre-Botzinger complex. (VRG: “rhythmicity area”) have intrinsic pacemaker activity – set the basal respiratory rate Control of Breathing – Respiratory Center 3. Pontine Respiratory Group (PRG): Influence and modify the activity of the medullary neurons; modify and fine- tune breathing rhythms generated by VRG – smooth out the transition between inspiration and expiration Regulation of the Respiratory Center Cortical influences: allow conscious control of respiration that may be needed to avoid inhaling noxious gases or water Chemoreceptor: central and peripheral chemoreceptors monitor levels of O2 and CO2 and provide input to the respiratory center Proprioceptor: rate and depth of breathing change during movements of joints and muscles The inflation reflex: stretching of the bronchi and bronchioles, stimulating the vagus, sending impulses to DRG which inhibits the diaphragm and external intercostal muscles Other factors: limbic system stimulation, pain, blood pressure and temperature.