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Human Phys
Mechanics of breathing
| Question | Answer |
|---|---|
| ATP needed for metabolism: cellular vs external | Cellular: O2 + glucose = CO2, water, ATP - oxygen needed for cellular respiration, CO2 a byproduct External: respiratory and cardiovascular systems collaborate to deliver oxygen to tissues, and transport CO2 to lungs for elimiation |
| External respiration | - movement of gases between environment and 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 cells |
| Functions of respiratory system | - rhythmically takes in and expels air - homeostatic regulation of body pH - filters pathogens and irritants - vocalisation/smell - BP regulation - megakarocyte productions - blood and lymph flow down pressure gradient (diaphragm) |
| Overview of respiratory physiology | - upper respiratory (head and nose) - lower respiratory (lungs and diaphragm) - lungs: bronchi, bronchioles, alveoli - conducting system – airways - respiratory zone - Alveoli - bones and muscles – chest cavity |
| Upper respiratory in detail: Nose | Bone and cartilage Vestibule lined with: - Stratified squamous epithelium Mucous membrane: - Ciliated Pseudo-stratified columnar epithelium - Goblet cells: mucus - warms, humidifies air, odour, voice, foreign matter trapped in mucus |
| Nasopharynx | Lined with: - Ciliated Psuedo-stratified columnar epithelium - Only air passes |
| Oropharynx | Space between soft palate and epiglotis |
| Laryngopharynx | Air and food passes Lined with more abrasion resistant cells: - stratified squamous epithelial cell |
| Larynx | Cartilaginous chamber Keeps food/drink out of airway Sound production |
| Lower respiratory tract: trachea | Anterior to the oesophagus 16-20 rings of hyaline cartilage (support) Lined by pseudostratified columnar epithelia composed mainly of mucous goblet cells and ciliated cells Cilia beat upward to remove debris - laden mucous (Mucociliary escalator) |
| Lungs and bronchial tree | Branching system of tubes Main bronchi supported by cartilage All lined with ciliated pseudostratified columnar epithelium Elastic connective tissue, smooth muscle - apex (top of lung) - base (bottom of lung) |
| Bronchial tree | - Each lung: branching system of air tubes (bronchial tree) First subdivision produces two bronchi (R L) Further divide into secondary bronchi Smallest subdivision is the bronchiole Main bronchus has 65,000 terminal bronchioles |
| Bronchioles | Lack cartilage Regulated by smooth muscle Under control of autonomic nervous system Ciliated cuboidal epithelium and smooth muscle Each bronchiole divides into 50-80 terminal bronchiole 0.5mm Terminal bronchiole- branches to 2 respiratory bronchioles |
| Alveoli | - 2 alveolar ducts that end in alveolar sacs - 150 million sacs that help increase surface area for effective exchange - intricate blood vessels critical to function |
| Airway epithelium | - mucociliary escalator: cleans and protects lung alveolar from foreign bodies - goblet cells secrete mucus to catch these, then cells beat upwards out of lungs - cilia need an aqueous saline environment, not just mucus |
| CFTR controls ASL (airway surface liquid) hydration | Lungs produce Mucin Removes particles/ bacteria from lungs Needs to be aqueous environment for the cilia to beat |
| CFTR channel | CFTR channel open Cl- moves out by diffusion H2O moves by osmosis Keeps the mucus aqueous and free flowing |
| Cystic fibrosis | CFTR channel ineffective Cl- ions cannot leave cell, H20 flows into cell Causes mucus to become thick/sticky, blocking lungs and increasing infections |
| Alveoli cells | - squamous type 1 cells: covers most area, thinness allows rapid diffusion - cuboid great type 2 cells: repairs alveolar epithelium, secretes surfactant preventing bronchioles collapsing - alveolar macrophages : clears away pathogens, dust |
| Alveolar-capillary | - Each alveoli surrounded by a web of capillaries supplied by small branches of the pulmonary artery - Barrier between them is the respiratory membrane - Low pressure, higher flow system designed to make the exchange of gases as efficient as possible |
| 4 compartments that oxygen must cross | 1) Dissolve in the water surface layer inside the lungs 2) Pass through the Alveoli cells 3) Shared basement membrane 4) Endothelial cells of the capillaries |
| Pleura and pleural cavity | Pleural lining has two layers: visceral (inner) layer is next to the lung parietal (outer) layer lines chest wall - The pleura produces fluid that lubricates space between the layers - allows the two layers to slide over each other as we breathe |
| Pneumothorax | Sub-atmospheric pressure in the pleural cavity helps keep the lungs inflated Pneumothorax: Air flows in, lung collapses |
| Respiratory muscles | The only muscles they contain 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 | |
| Breathing in and out | Main muscles: diaphragm and intercostal muscles - contracts: tenses, drops, enlarges thoracic cavity, low pressure air moves in - relaxed: pressed upward into lungs, lungs are at minimal volume, higher pressure-air moves out |
| NORMAL EXPIRATION is an energy saving passive process achieved by the elasticity of the lungs and thoracic cage Breathing, controlled by: - Heart rate increase, more gas exchange - Respiratory muscle, breath faster, more gas exchange | |
| What controls our breathing? | - regulated by pCO2, pO2 and H+ concentration - 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 |
| Under control of negative feedback - The rate of ventilation is controlled by the respiratory control centre in the MEDULLA OBLONGATA - During exercise, the rate of ventilation changes in response to the amount of CO2 in the blood | |
| Neural control of respiratory centres | Control at two levels of the brain: 1) Unconscious and automatic 2) Cerebral and conscious- enabling breathing at will - Important in speaking, singing, holding your breath - Control originates in the motor cortex of the cerebrum |
| MEDULLA OBLONGATA: The ventral respiratory group (VRG) Dorsal respiratory group (DRG) PONS Pontine respiratory group (PRG) | |
| Ventral respiratory group - VGR | - primary rhythm generator - Inspiratory/ expiratory neurons Quiet breathing inspiratory neurons fire for 2 seconds sends signal to the diaphragm and intercostal muscles. Inhibits Expiratory neurons Contraction of muscle enlarges the thoracic cage |
| Inspiratory neurons stop firing, expiratory neurons fire and inspiratory muscles relax Breathing- oscillating pattern of neurons firing 12 breathes per minute | |
| Dorsal respiratory group - DRG | Modifies the basic rhythm Receives input from several sources: - PRG - Chemosensitive areas in a) medulla oblongata b) major arteries - Stretch receptors in the airway - Higher brainstem-emotional influences on breathing |
| Pontine respiratory group - PRG | - receives input from higher brain Hypothalamus Limbic system Cerebral cortex - Hastens or delays the transition from expiration to inspiration: Breath- shorter and shallower OR Breath- longer and deeper - voluntary control |
| Regulation of CO2 in blood | - normal CO2: activity increases, respiration and CO2 increases, medulla oblongata stimulated, sends impulses - heart: rate increases, CO2 blood returned fast to lungs, levels drop - breathing: rate increases, CO2 expelled faster |
| Gas laws | Boyle's: double volume, half pressure, half volume. double pressure Charles': heating causes gas to expand Dalton's: The total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual gases |
| Henry's 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, airflow | - volume increases – lung pressure decreases - Intrapulmonary pressure falls below atmospheric pressure - Air flows down pressure gradient into the lungs - volume decreases- lung pressure increases - Air flows down pressure gradient out of the lungs |
| Resistance | Affecting factors: bronchioles resistance Pulmonary compliance High compliance means lungs and thoracic wall expand easily Low compliance means expansion resistance - limitation to compliance is film of water on respiratory system ST/compliance |
| Effect of surface tension on compliance | SURFACTANT in the lungs is able to disrupt the hydrogen bonds and reduce the surface tension They are hydrophobic so spread across the surface of the water film in the lungs |
| The Pleura | Pleural cavity bounded by double layered membrane called pleura - inner visceral and outer parietal layer - serous fluid held within: Reduction of friction Creation of a gradient pressure Compartmentalisation |
| Lung volumes and capacities | Measured by spirometry 1) Tidal volume: normal breathing 2) Inspiratory reserve volume: Inspire with maximum effort (~3L) 3) Expiratory reserve volume: Expire maximally (1.1L) 4) Residual volume: Lungs never get completely empty (1.2L) |
| Anatomical dead space | Air that enters the alveoli is available for gas exchange Not all air makes it that far There is always still about 150ml air in the conducting airway - If a person breathes in 500ml air and 150ml is dead space, 350ml ventilates the alveoli |
Created by:
reub8n
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