Human Physiology: Breathing Mechanics Lecture 2024 PDF

HUMAN PHYSIOLOGY BIO-5004A/ BIO5104 The mechanics of breathing Dr Tracey Swingler [email protected]  HUMAN PHYSIOLOGY BIO-5004A LECTURE CONTENT Major functions of the respiratory system Anatomy of the respiratory system Ventilation...

HUMAN PHYSIOLOGY BIO-5004A/ BIO5104 The mechanics of breathing Dr Tracey Swingler [email protected]  HUMAN PHYSIOLOGY BIO-5004A LECTURE CONTENT Major functions of the respiratory system Anatomy of the respiratory system Ventilation Gas laws Vanders physiology  HUMAN PHYSIOLOGY BIO-5004A/ BIO5104 LEARNING OUTCOMES Describe the anatomy of the function respiratory system Describe the muscles involved in breathing Explain the neural control of breathing Understand the Gas laws and how they are applied in physiology st of our metabolism needs ATP Cellular respiration Intracellular reaction of O2 with glucose to produce CO2, water and ATP. Need oxygen for cellular respiration Carbon dioxide produced as a by-product Carbon dioxide oxygen External respiration Respiratory system and the cardiovascular system collaborate to deliver oxygen to tissues Transport carbon dioxide to the lungs for elimination (cardio-pulmonary system) External Respiration Bulk Flow External Diffusion Respiration Movement of gases between the Bulk Flow environment and the body’s cells. 1. Exchange of air between the atmosphere and the lungs. 2. Exchange of O2 and CO2 between lungs and blood. 3. Transport of O2 and CO2 by blood. 4. Exchange of gases between blood and Diffusion cells. Functions of the respiratory system Respiratory system is an organ system that rhythmically takes in air and expels it from the body - Supply body with oxygen - Eliminate carbon dioxide 1. Exchange of gases between the atmosphere and the blood. 2. Homeostatic regulation of body pH. 3. Filters inhaled pathogens and irritating substances. 4. Vocalisation. 5. Sense of smell 6. Blood pressure regulation 7. Platelet production (megakaryocytes made in the lungs) 8. Blood and lymph flow (pressure gradient made by diaphragm) 9. Expulsion of abdominal contents Heat and Water loss! rview of the Respiratory System Conducting system – airways Respiratory zone - Alveoli Bones and muscles – chest cavity Pharynx Upper Nose respirato ry tract Larynx Trach Lower ea respirato ry tract Lung Bronchi s Gas exchange Dead-end pathway of: Bronchi Bronchioles Alveoli (tiny thin-walled air sacs) per respiratory tract Nasopharynx Lined with: Ciliated Psuedo-stratified Nose columnar epithelium Shaped by bone and Only air passes cartilage Vestibule lined with: Oropharynx Stratified squamous Space between soft palate epithelium and epiglotis Mucous membrane: Ciliated Pseudo-stratified Pharynx Nasopharynx Laryngopharynx columnar Air and food passes epithelium Oropharynx Lined with more abrasion Goblet cells - secrete resistant cells: mucus Laryngophar stratified squamous ynx Laryn epithelial cell Cleanses, warms, humidifies Larynx x air Cartilaginous chamber Detects odour Keeps food/drink out of Resonating chamber for the airway voice Sound production Inhaled foreign matter trapped in the mucus wer respiratory tract Trachea Anterior to the oesophagus 16-20 rings of hyaline cartilage 12cm long (support) Lined by pseudostratified columnar epithelia composed Apex mainly of mucous goblet cells and ciliated cells Cilia beat upward to remove debris laden mucous (Mucociliary The lung and bronchial tree escalator) Branching system of tubes Cardiac Main bronchi supported by impression cartilage All lined with ciliated pseudostratified columnar Base epithelium Elastic connective tissue, smooth muscle DIAPHRAM er respiratory tract: Bronchial tree Bronchial tree Each lung: branching system of air tubes (bronchial tree) First subdivision produces two bronchi (R L) Trache Further divide into secondary bronchi a Smallest subdivision is the bronchiole Main bronchus 65,000 terminal Superior lobar bronchioles Bronchioles Branches bronchi twice Inferior lobar bronchi Lack supportive cartilage < Regulated by smooth muscle d of the conducting zone 1mm Under control of autonomic nervous system espiratory zone gas exchange) Ciliated cuboidal epithelium and smooth muscle wer respiratory tract: Alveoli Alveoli Respiratory bronchioles have 2-10 alveolar ducts (non-ciliated simple squamous epithelium) Ducts end in alveolar sacs around a central atrium Lung-spongey mass of 150 million little Alveoli sacs Purpose to increase surface area Provides 70m2 of gas-exchange surface Surface of a squash court Alveoli- pouch approx. 02.-0.5mm in diameter Relationship between the alveoli and blood stream is critical irway epithelium Mucociliary escalator: Cleans the lung and protect alveolar from pathogens or dust. Cells lining the airway are ciliated Goblet cells secrete the mucus Critical for efficient mucus flow. Cilia constantly beating and moving upwards transporting fluid upward out of your lungs continuously, foreign particles are caried in the mucus For this to work the cilia need to be in an aqueous environment-layer of saline If they were in the mucus, they wouldn’t be able to beat Mucociliary escalator CFTR controls airway surface liquid (ASL) hydration AIRWAY LUMEN Hypertonic Cl- Cl- Cl- H2O Mucociliary escalator system Mucin CFTR ENaC Apical Cilia surface H2O Na+ Cl- Secretory Epitheli cell CFTR co-operate al cells to regulate Na+ and Cl- ion balance Baso- Cl- K+ lateral Na+ K+ surface Basement membrane Lungs produce Mucin CFTR channel open Removes particles/ bacteria from Cl- moves out by diffusion lungs H2O moves by osmosis Needs to be aqueous Keeps the mucus aqueous and free Cystic fibrosis is caused by mutation in the CFTR gene Thick sticky mucus H2 O Cilia CFTR ENaC Apical Na+ surface Secretory Cl- Cl- H2O Epithelial Cl- Cl- Na+ Na+ cell cells Hypertonic CFTR function is impaired, leads to reduced mucosal hydration via absorption of Baso- Na+ + Cl- K lateral Na+ K+ surface Basement membrane CFTR channel absent/ ineffective Cl- can no longer move out of the cell H2O moves into the cell by osmosis Mucous is thick and sticky Blocks lungs and increases infections wer respiratory tract: Alveoli Cells in the alveoli Squamous type I cells - Cover 95% area - Thinness allows rapid gas diffusion between air and blood Cuboid great type II cells - Repair alveolar epithelium Cuboid - Secrete surfactant (lipids and proteins prevents bronchioles collapsing when you exhale) Alveolar macrophages Squamous - Wander round the lumen and connective tissues - Phagocytosing dust particles, bacteria Macrophage - 100 million macrophages – ride along the mucociliary escalator- swallowed and digested eolar-capillary membrane Bronchiole Terminal Each alveoli surrounded by a web of capillaries bronchiole Respiratory bronchiole supplied by small branches of the pulmonary artery Barrier between them is the respiratory Alveolar sac membrane Capillary network Low pressure, higher flow system designed to Alveoli make the exchange of gases as efficient as possible Oxygen must travel across 4 compartments to enter the 1. Liquid 2. 1. Dissolve in the water surface layer inside the lungs 3.Interstitial space 0.5mm 2. Pass through the Alveoli cells (1/15th ) RBC 3. Shared basement membrane 4. 4. Endothelial cells of the capillaries Capillary Ventilation e Pleura and pleura cavity Pleural cavity: double layered cavity surrounding the lungs Visceral pleura: Inner membrane, covers the surface of the lungs Parietal pleural: Outer membrane lines the chest wall and diaphragm Pleural cavity contain serous fluid Functions: Pneumotho ⁻ Cushions the lungs ⁻ Sub-atmospheric pressure (negative pressure) in rax the pleural cavity helps keep the lungs inflated. Pneumothorax: Air flows into the pleural cavity disrupting the balance of pressure The pressure equalises, lungs can no longer stay expanded against the chest wall, lung collapses The respiratory muscles The only muscles inside lungs are smooth muscle in the walls of the bronchi The smooth muscle can only adjusts the diameter of the airway (ANS) Diaphragm and intercostal muscles cause change in volume and therefore pressure Air, like fluids, flows down a pressure gradient from a point of high pressure to lower The respiratory muscles: Breathing in/ out Main muscles: DIAPHRAGM and INTERCOSTAL MUSC Diaphragm responsible for moving 2/3rd of the airflow ⁻ Contracts: tenses and drops (1.5cm light inhale, 12cm deep breath) ⁻ Enlarges the thoracic cavity, lowers pressure-air moves in Relaxed: pressed upward into lungs ⁻ lungs are at minimal volume, higher pressure- Normal air expiration moves out is an energy saving passive process achieved by the elasticity of the lungs Increase and thoracic cage chest cavity Decrease Breathing, controlled by: chest cavity Diaphragm Diaphragm 1. Heart rate increase, more gas exchange contracts relaxes 2. Respiratory muscle, breath faster, more gas exchange Neural control of breathing rate? hemoreceptors Breathing is regulated by pCO2, pO2 and H+ concentration CHEMORECETORS- specialised nerve cells that sense a change in the chemical composition of the blood Central chemoreceptors in the medulla oblongata detect changes in CO2 levels Peripheral chemoreceptors in the carotid and aortic bodies also detect CO2 levels, as well as O2 levels and blood pH Information is sent to respiratory centres in the brain Central Alters the rate of ventilation changes in chemoreceptors Peripheral response to the amount of CO2 in the blood by chemoreceptors changing heart rate and breathing rate. Under the control of negative feedback ral control of breathing: Respiratory centre Heartbeat/ breathing rhythmic processes in the body Breathing depends on repetitive signals from the brain Well-orchestrated control of multiple muscles Control at two levels of the brain: 1. Unconscious ⁻ Important and automatic in speaking, singing, holding your breath 2. Cerebral and conscious- enabling ⁻ Control originates in the motor cortex breathing at of the cerebrum PRG will Pons RESPIRATORY CENTRE The respiratory 1. Pons centre: three ⁻ Pontine respiratory group (PRG) groups of neurons VRG 2. Medulla oblongata Medulla DRG ⁻ The ventral respiratory group (VRG) ⁻ Dorsal respiratory group (DRG) al control of breathing: Ventral respiratory group Pons Medulla VGR- Primary generator of rhythm 3. PRG Inspiratory/ expiratory neurons Quiet breathing inspiratory neurons fire for 2 seconds sends signal to the diaphragm and intercostal muscles. Inhibits Expiratory neurons 1.VRG Contraction of muscle enlarges the thoracic cage Inspiratory neurons stop firing, expiratory neurons 2. DRG fire and inspiratory muscles relax Breathing- oscillating pattern of neurons firing 12 breathes per minute Intercostal nerves Phrenic nerves Intercostals Diaphragm ral control of breathing: Dorsal respiratory group Pons Medulla DRG- Modifies the basic rhythm 3. PRG Receives input from several sources: 1. PRG 2. Chemosensitive areas in a) medulla oblongata b) major arteries 3. Stretch receptors in the airway 1.VRG 4. Higher brainstem-emotional influences on breathing 2. DRG The DRG feeds back information to the VRG to adapt breathing rate to conditions Intercostal nerves Phrenic nerves Intercostals Diaphragm al control of breathing: Pontine respiratory group Pons Medulla PRG- Receives input from the higher brain: 3. PRG ⁻ Hypothalamus ⁻ Limbic system ⁻ Cerebral cortex Issues output back to the DRG, VRG 1.VRG Hastens or delays the transition from expiration to 2. DRG inspiration: ⁻ Breath- shorter and shallower OR ⁻ Breath- longer and deeper Intercostal Adapts breathing to sleeping, crying, laughing nerves Pain, emotion, voluntary control Phrenic nerves Intercostals Diaphragm ulation of CO2 levels in the blood Using more O2 Sense CO2 Produces CO2 Start here  Gas Laws of physics: their relevance to Gas Laws 1. Boyles Law P α 1/V 2. Charles Law P 1 V1 = P 2 V2 3. Daltons Law Or double the Ie. Halve the volume: halve the volume: double the 4. Henrys Law pressure. pressure. 1. Boyles The pressureLaw exerted by a given mass of an ideal gas in a closed system at constant temperature, is inversely proportional to the volume it occupies. Gas Laws 1. Boyles Law V= kT or V/T=k 2. Charles Law 3. Daltons Law 4. Henrys Law 2. Charles The volume Law of a given gas is directly proportion to its absolute temperature (assuming a constant pressure) Heating a gas will cause it to expand Gas Laws 1. Boyles Law 2. Charles Law Ptotal = P1 + P2 + P3 ………. + Px 3. Daltons Law PO2 = Patm x 21% 4. Henrys Law 3. Daltons Law The total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual gases. Each gas acts independently of other gases in the same space. Gas Laws 1. Boyles Law 2. Charles Law 3. Daltons Law Solubility of gases 4. Henrys Law 4. Henrys Law At the air-water interface, the amount of gas that dissolves is determined by its solubility in water and its partial pressure in the air (assuming constant temp.). Pressure, resistance and air flow Flow α ΔP/R Respiratory air flow is governed by the same principles The pressure gradient that drives inspiration is atmospheric pressure One way to change the pressure of a gas in enclosed space is to change the volume of the container (Boyles Law) 1. Lung volume increases – lung pressure decreases 2. Intrapulmonary pressure falls below atmospheric pressure Flow is directly proportional to the 3. Air flows down the pressure gradient into pressure difference between two the lungs points P and inversely proportional to the resistance 4. Lung volume decreases- lung pressure Pressure, resistance and air flow: Pressure is one determinant of air flow The other is resistance Flow α ΔP/R 3-5% of body’s energy expended during quiet breathing. Energy needed to overcome ‘stretchability’ of lungs and resistance by airways to airflow. Two factors affect resistance: 1. Diameter of the bronchioles 2. Pulmonary compliance ⁻ High compliance means the lungs and the thoracic wall expand easily ⁻ Low compliance means they resist expansion ⁻ Major limitation to compliance is the thin film of water on the respiratory system ⁻ Surface tension/ compliance ct of Surface Tension on Compliance Major limitation to compliance is the thin film of water on the respiratory system- Surface tension The film of water is necessary for gas exchange But creates a problem for ventilation Water molecules are The surface tension in the lungs draws the attracted to each other by passageways inwards hydrogen bonds SURFACTANT in the lungs is able to disrupt the hydrogen bonds and reduce the surface tension Creates surface Composed of amphipathic proteins and tension phospholipids They are hydrophobic so spread across the surface of the water film in the lungs 1. Lowering surface tension at the air–liquid interface and thus preventing alveolar collapse at end-expiration, 2. Killing of pathogens or preventing their dissemination,  LEARNING OUTCOMES Describe the anatomy of the function respiratory system Explain how respiratory centres in the brain control ventilation Understand the Gas laws and how they are applied in physiology  Thank you Any questions