Ch 23 Respiratory System Lecture Notes PDF

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A&P 103 - Ch 23 Respiratory System Lecture Notes

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Respiratory vs. conducting zone A. Structure 1. Conducting zone: all structures superior to (and including) the terminal bronchioles: bronchioles, bronchus, trachea, larynx, pharynx, nasal cavity, nose 2. Respiratory zone: respiratory bronchioles, alveolar ducts, alveoli B. Function 1. Conducting zone: bringing air into the respiratory system a) No gas exchange occurs in the conducting zone 2. Respiratory zone: site of gas exchange a) Oxygen enters red blood cells, carbon dioxide leaves red blood cells C. Epithelium and connective tissue 1. General epithelial structure of the respiratory mucosa a) Pseudostratified columnar epithelium w/ goblet cells and cilia b) Epithelium becomes progressively thinner deeper into the respiratory system (nose → alveoli; thickest epithelium → thinnest epithelium) 2. Respiratory zone: simple squamous epithelium only Anatomy of the respiratory system A. Nasal cavity 1. Nasal conchae: bony projections in the nasal cavity to increase its surface area that air encounters 2. Paranasal sinuses: holes/cavities in bones around nose, continuous w/ nasal cavity a) Frontal, ethmoidal, sphenoidal, and maxillary sinuses (4 total formed by facial bones) B. Pharynx 1. 3 subdivisions: nasopharynx, oropharynx, laryngopharynx C. Larynx (voice box) 1. Hyoid bone: point of attachment for ligaments and muscles, supports tongue, supports CT of larynx 2. Thyroid cartilage: provides structure and protection to larynx, point of attachment for muscle and ligaments a) Large butterfly shape anteriorly, wraps around laterally, absent posteriorly b) Function: keeps larynx patent (open) so air and bolus can travel through 3. Cricoid cartilage: provides support, point of attachment for ligaments and CT a) Complete ring of hyaline cartilage around the larynx, wider in the back than anteriorly b) Keeps larynx patent (open) 4. Tracheal rings: hyaline cartilage rings inferior to the cricoid cartilage to keep trachea open

a) Incomplete (absent) posteriorly 5. Epiglottis: flap of elastic cartilage at superior end of larynx a) Function: bends to cover airway when swallowing bolus of food so it does not enter windpipe (trachea) and slides into esophagus 6. Glottis: area between the vocal folds (vocal cords) that gets covered by the epiglottis when swallowing food a) Vestibular folds: tissue that protect the vocal cords, superior to the vocal cords; ‘false vocal folds’ D. Trachea (windpipe) 1. Tracheal rings: hyaline cartilage rings inferior to the cricoid cartilage to keep trachea open a) Incomplete (absent) posteriorly so food can be swallowed comfortably 2. Carina: ridge of hyaline cartilage at the bifurcation point of the trachea 3. Trachea bifurcates into 2 main bronchi (right and left bronchus) E. Bronchi 1. Bronchial tree: collective name for all subdivisions of the right and left main bronchus; all supported w/ hyaline cartilage 2. Primary bronchi: right main bronchi and left main bronchi 3. Secondary bronchi/lobar bronchi: leads to a lobe of the lung a) 3 lobar bronchi on right side, 2 lobar bronchi on left side 4. Tertiary bronchi/segmental bronchi: leads into a subdivision of a lobe of the lung, approx. 10 in each lobe 5. Smaller bronchi: hundreds-thousands of bronchi branching across the lobe 6. Bronchioles: much smaller bronchi off the smaller bronchioles; no hyaline cartilage, surrounded by thin layer of smooth muscle a) Terminal bronchioles: last part of the conducting zone of the lung b) Respiratory bronchioles: beyond the terminal bronchioles where gas exchange occurs (beginning of respiratory zone) c) Alveolar ducts: beyond the respiratory bronchioles, leading to alveolar sacs (clusters of alveoli); no smooth muscle or cartilage d) Alveoli: the individual pockets w/in alveolar sacs (1) Surrounded by pulmonary capillary beds for gas exchange (2) 3 distinct cells: (3) Alveolar type I cells (type I pneumocytes): simple squamous epithelial cells that makes up alveolar wall; forms the alveolar epithelium of the respiratory membrane (4) Alveolar macrophages: fixed or wandering immune cells that engulf debris from inhaled air (5) Alveolar type II cells (type II pneumocytes): secrete surfactant to break up surface tension between water molecules in infant alveoli and air, so alveolar sacs don’t collapse at first breath after birth

III.

Anatomy of the lungs A. Surface features 1. Base (diaphragmatic surface): inferior edge of the lung that touches the diaphragm 2. Apex: superior edge of the lung that extends above the rib 3. Costal surfaces: anterior, lateral, and posterior surfaces of the lung contained w/in the ribs 4. Mediastinal surface: medial surfaces of the lung touching/taking shape around mediastinum 5. Lobes of the right lung: superior lobe, middle lobe, inferior lobe a) Oblique fissure: division between the superior and inferior lobe b) Horizontal fissure: division between the superior lobe and middle lobe 6. Lobes of the left lung: superior lobe and inferior lobe a) Oblique fissure: division between the two lobes 7. Hilum: where certain structures enter and exit the lung, located on the posterior surface: main bronchus, pulmonary arteries and veins, nervous supply, lymphatic drainage 8. Cardiac notch: indentation on the superior lobe of the left lung that molds around the heart 9. Cardiac impression: divet in the medial surface of the superior lobe of left lung created by the heart 10. Aortic impression: divet in the medial surface of the superior lobe of left lung where ascending and descending aorta sit B. Connective tissue coverings 1. Visceral pleura: layer of CT that adheres directly to lung tissue 2. Parietal pleura: layer of CT outside of the visceral pleura, lining the ribcage 3. Pleural cavity: space between the visceral and parietal pleura, filled w/ serous fluid a) Intrapleural pressure: pressure in the pleural cavity; always slightly lower than the pressure in the alveoli

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Lung volume and capacity A. Boyle’s law 1. There is an inverse relationship between the pressure of a gas and the volume the gas is occupying a) When gas occupies a large space, there is less pressure since gaseous molecules don’t collide much (1) Volume increases → pressure decreases b) When gas occupies a small space, three is more pressure sincere gaseous molecules collide more with each other and the container they are in (1) Volume decreases → pressure increases 2. Gases move down this pressure gradient: move from an area of higher pressure to an area of lower pressure

B. Measuring volume and capacity 1. Lung volumes measured with a spirometer 2. Tidal volume: amount of air transported in and out of patient’s lungs during normal quiet breathing; adult average is 500 mL 3. Inspiratory reserve volume (IRV): extra volume of air a patient can breathe in above tidal volume during forced inhalation a) Measure of compliance of lungs; how easy it is to inhale a significant volume of air 4. Inspiratory capacity (IC): sum of the tidal volume and inspiratory reserve volume; total amount of air a patient cna bring in to their lungs 5. Expiratory reserve volume (ERV): extra volume of air a patient can exhale beyond tidal volume during forced exhalation a) Measure of elasticity of lungs; how much recoil the lungs have to exhale air 6. Vital capacity: total volume of air that can be moved in and out of the lungs; tidal + inspiratory reserve + expiratory reserve 7. Residual volume: amount of air left in the lungs after forced exhalation; can’t be measured by a spirometer, must be estimated 8. Functional residual capacity (FRC): expiratory reserve + (estimated) residual volume 9. Total lung capacity (TLC): sum of all the measurable lung capacities and residual volume 10. Forced expiratory volume (FEV): percent of vital capacity that can be exhaled in a set period of time a) FEV1: percentage expelled in one second; 75-85% in a healthy person b) Low FEV1 is seen in emphysema patients, other pts with poor expiration 11. Maximum voluntary ventilation (MVV): greatest amount of air that can be taken in and expelled from the lungs in 1 minute V.

Physiology of respiration A. Processes of respiration 1. Pulmonary ventilation: movement of gases (air) between atmosphere and alveoli; not gas exchange, just physical movement of air 2. Alveolar gas exchange (external respiration): exchange of gases between alveoli and blood, across respiratory membrane 3. Gas transport: transport of gases in the blood between lungs and systemic cells 4. Systemic gas exchange (internal respiration): exchange of gases between blood and systemic cells; delivering oxygen to body tissues B. Partial pressure and Dalton’s law 1. Partial pressure: pressure exerted by each gas within a mixture of gases a) In a mixture of many gases, partial pressure measures how much a single gas contributes to the total mixture b) Measured in mm Hg, written as P followed by gas symbol (e.g. partial pressure of oxygen = PO2)

c) Each gas moves independently down its own partial pressure gradient during gas exchange 2. Atmospheric pressure: the total pressure exerted by all the gases in the atmosphere (in the air we breath) a) 760 mm Hg at sea level 3. Dalton’s law: the total pressure in a mixture of gases is equal to the sum of the individual partial pressures a) To calculate individual partial pressure: total pressure * % of gas C. Oxygen and carbon dioxide transport 1. Oxygen a) Solubility coefficient of oxygen is low; very little oxygen dissolves in the plasma (2%) b) Hemoglobin is main mechanism of oxygen transport; 98% of O2 in blood is bound to the iron of hemoglobin (4 molecules of O2 per 1 hemoglobin) (1) HbO2: oxyhemoglobin (hemoglobin that is bound to oxygen) (2) HHb: deoxyhemoglobin (hemoglobin without bound oxygen) c) Oxygen-hemoglobin saturation curve: the changes in hemoglobin’s affinity for oxygen in certain environment conditions (1) ‘Affinity for oxygen’ = how well hemoglobin will bind to O2 (2) High affinity → hemoglobin will bind to and lock down on O2, becoming saturated w/ O2, occurs in oxygen-rich areas (3) Low affinity → hemoglobin will ‘open’ and release its O2 to the surrounding environment, occurs in oxygen-poor areas (4) Effect of temperature: as temperature rises, more oxygen is released (affinity for oxygen is lower) 2. Carbon dioxide a) CO2 dissolved in the plasma: 7% b) CO2 attached to amine group of the globin in hemoglobin: 23% (1) HbCO2: carbaminohemoglobin (hemoglobin that has CO2 bound to it) c) Bicarbonate dissolved in plasma: 70% (1) CO2 becomes bicarbonate ion after reacting with water in erythrocytes; is regenerated when blood moves through pulmonary capillaries (2) CO2 and water react in the presence of an enzyme (carbonic anhydrase) to become carbonic acid, which then dissociates (loses a proton) to become bicarbonate and a hydrogen ion: **reaction is reversible** (a) CO2 + H2O → (catalyzed by carbonic anhydrase) → H2CO3 → HCO3- + H+ (3) Chloride ion shift: for everyone bicarbonate ion that leaves a red blood cell, a chloride ion enters that red blood cell to maintain the same electric charge (and vice versa)

VI.

Neural control of respiration A. Overview 1. Medulla oblongata is respiratory center of brainstem for neural control of rate and depth of breathing a) Receives info about how well tissues are being oxygenated, sends out motor instructions to adjust depth and rate of breathing accordingly 2. Peripheral chemoreceptors: receptors in walls of blood vessels that monitor CO2, proton, and O2 levels of blood a) Sends brainstem info about concentration of gases in the blood 3. Central chemoreceptors: receptors in the brainstem that monitor CO2, proton, and O2 levels of cerebrospinal fluid 4. Irritant receptors: receptors in air passageways stimulated by particulate matter (dust, debris) 5. Baroreceptors: pressure receptors in the pleurae and bronchioles that respond to stretch 6. Proprioceptors: receptors in muscles and joints stimulated by body movements B. Medullary respiratory center groups 1. Ventral respiratory group (VRG) a) Located on anterior side of medulla oblongata b) Controls normal, relaxed, tidal breathing c) ‘2 seconds on, 3 seconds off’ (1) Action potentials are sent through the phrenic nerve to the intercostals and diaphragm for 2 second to stimulate inhalation (2) No action potentials are sent for 3 seconds to stimulate relaxation of intercostals and diaphragm, resulting in exhalation 2. Dorsal respiratory group (DRG) a) Located on the posterior side of medulla oblongata b) Responds to information sent from receptors to change rate & depth of breathing as needed 3. Medullary respiratory center controls can be changed by pontine respiratory center (aka pneumotaxic center) in the pons, which ‘supervises’ VRG and DRG...