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This 10 page Class Notes was uploaded by Jess Graff on Monday May 2, 2016. The Class Notes belongs to BMS 508 at University of New Hampshire taught by Mary Katherine Lockwood, PhD in Spring 2016. Since its upload, it has received 5 views. For similar materials see Human Anatomy and Physiology II in Biological Sciences at University of New Hampshire.
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Date Created: 05/02/16
BMS 508.03 3/23/2016 Chapter 23 (cont) Respiration (cont) The Lungs • The Lungs • Left and right lungs • In left and right pleural cavities • The base • Inferior portion of each lung rests on superior surface of diaphragm • Lobes of the lungs • Lungs have lobes separated by deep fissures • Lobes and Surfaces of the Lungs • The right lung has 3 lobes • Superior, middle, and inferior • Separated by horizontal and oblique fissures • The left lung has 2 lobes • Superior and inferior • Separated by an oblique fissure • Lung Shape • Right lung • Wider • Displaced upward by liver • Left lung • Longer • Displaced leftward by the heart forming the cardiac notch • The Bronchi • The Bronchial Tree • Formed by the primary bronchi and their branches • Extrapulmonary Bronchi • The left and right bronchi branches outside the lungs • Intrapulmonary Bronchi • Branches within the lungs • A Primary Bronchus • Branches to form secondary bronchi (lobar bronchi) • 1 secondary bronchus goes to each lobe • Secondary Bronchi • Branch to form tertiary bronchi (segmental bronchi) • Each segmental bronchus • Supplies air to a single bronchopulmonary segment • Bronchopulmonary Segments • The right lung has 10 • The left lung has 8 or 9 • Bronchial Structure • The walls of primary, secondary, and tertiary bronchi • Contain progressively less cartilage and more smooth muscle • Increased smooth muscle tension affects airway constriction and resistance • Bronchitis • Inflammation of bronchial walls • Causes constriction and breathing difficulty • The Bronchioles • Each tertiary bronchus branches into multiple bronchioles • Bronchioles branch into terminal bronchioles • 1 tertiary bronchus forms about 6500 terminal bronchioles • Bronchiole Structure • Bronchioles • No cartilage • Dominated by smooth muscle • Autonomic Control • Regulates smooth muscle • Controls diameter of bronchioles • Controls airflow and resistance in lungs • Bronchodilation • Dilation of bronchial airways • Caused by sympathetic ANS activation • Reduces resistance • Bronchoconstriction • Constricts bronchi • Caused by: • Parasympathetic ANS activation • Histamine release (allergic reactions) • Asthma • Excessive stimulation and bronchoconstriction • Stimulation severely restricts airflow • Pulmonary Lobules • Trabeculae • Fibrous connective tissue partitions from root of lung • Contain supportive tissues and lymphatic vessels • Branch repeatedly • Divide lobes into increasingly smaller compartments • Pulmonary lobules are divided by the smallest trabecular partitions (interlobular septa) • Each terminal bronchiole delivers air to a single pulmonary lobule • Each pulmonary lobule is supplied by pulmonary arteries and veins • Each terminal bronchiole branches to form several respiratory bronchioles, where gas exchange takes place • Alveolar Ducts and Alveoli • Respiratory bronchioles are connected to alveoli along alveolar ducts • Alveolar ducts end at alveolar sacs • Common chambers connected to many individual alveoli • Each alveolus has an extensive network of capillaries • Surrounded by elastic fibers • Alveolar Epithelium • Consists of simple squamous epithelium • Consists of thin, delicate type I pneumocytes patrolled by alveolar macrophages (dust cells) • Contains type II pneumocytes (septal cells) that produce surfactant • Surfactant • An oily secretion • Contains phospholipids and proteins • Coats alveolar surfaces and reduces surface tension • Respiratory Distress Syndrome • Difficult respiration • Due to alveolar collapse • Caused when type II pneumocytes do not produce enough surfactant • Respiratory Membrane • The thin membrane of alveoli where gas exchange takes place • Three Layers of the Respiratory Membrane • Squamous epithelial cells lining the alveolus • Endothelial cells lining an adjacent capillary • Fused basement membranes between the alveolar and endothelial cells • Diffusion • Across respiratory membrane is very rapid • Because distance is short • Gases (O an2 CO ) are2lipid soluble • Inflammation of Lobules • Also called pneumonia • Causes fluid to leak into alveoli • Compromises function of respiratory membrane • Blood Supply to the Lungs • Respiratory exchange surfaces receive blood • From arteries of pulmonary circuit • A capillary network surrounds each alveolus • As part of the respiratory membrane • Blood from alveolar capillaries • Passes through pulmonary venules and veins • Returns to left atrium • Also site of angiotensin-converting enzyme (ACE) • Capillaries supplied by bronchial arteries • Provide oxygen and nutrients to tissues of conducting passageways of lung • Venous blood bypasses the systemic circuit and flows into pulmonary veins • Blood Pressure • In pulmonary circuit is low (30 mm Hg) • Pulmonary vessels are easily blocked by blood clots, fat, or air bubbles • Causing pulmonary embolism • The Pleural Cavities and Pleural Membranes • 2 pleural cavities • Separated by the mediastinum • Each pleural cavity: • Holds a lung • Lined with a serous membrane (the pleura) • The Pleura • Consists of two layers • Parietal pleura • Visceral pleura • Pleural fluid • Lubricates space between 2 layers Introduction to Gas Exchange • Respiration • Refers to two integrated processes 1. External respiration • Includes all processes involved in exchanging O and CO 2 2 with the environment 2. Internal respiration • Result of cellular respiration • Involves the uptake of O and 2roduction of CO within 2 individual cells • Three Processes of External Respiration • Pulmonary ventilation (breathing) • Gas diffusion 1. Across membranes and capillaries • Transport of O an2 CO 2 1. Between alveolar capillaries 2. Between capillary beds in other tissues • Abnormal External Respiration Is Dangerous • Hypoxia 1. Low tissue oxygen levels • Anoxia 1. Complete lack of oxygen Pulmonary Ventilation • Pulmonary Ventilation • The physical movement of air in and out of respiratory tract • Provides alveolar ventilation • The Movement of Air • Atmospheric pressure • The weight of air • Has several important physiological effects • Gas Pressure and Volume • Boyle’s Law • Defines the relationship between gas pressure and volume P = 1/V • In a contained gas: • External pressure forces molecules closer together • Movement of gas molecules exerts pressure on container • Pressure and Airflow to the Lungs • Air flows from area of higher pressure to area of lower pressure • A Respiratory Cycle • Consists of: • An inspiration (inhalation) • An expiration (exhalation) • Pulmonary Ventilation • Causes volume changes that create changes in pressure • Volume of thoracic cavity changes • With expansion or contraction of diaphragm or rib cage • Compliance • An indicator of expandability • Low compliance requires greater force • High compliance requires less force • Factors That Affect Compliance • Connective tissue structure of the lungs • Level of surfactant production • Mobility of the thoracic cage • Pressure Changes during Inhalation and Exhalation • Can be measured inside or outside the lungs • Normal atmospheric pressure • 1 atm = 760 mm Hg • The Intrapulmonary Pressure • Also called intra-alveolar pressure • Is relative to atmospheric pressure • In relaxed breathing, the difference between atmospheric pressure and intrapulmonary pressure is small • About 1 mm Hg on inhalation or 1 mm Hg on exhalation • Maximum Intrapulmonary Pressure • Maximum straining, a dangerous activity, can increase range • From 30 mm Hg to 100 mm Hg • The Intrapleural Pressure • Pressure in space between parietal and visceral pleura • Averages 4 mm Hg • Maximum of 18 mm Hg • Remains below atmospheric pressure throughout respiratory cycle • The Respiratory Cycle • Cyclical changes in intrapleural pressure operate the respiratory pump • Which aids in venous return to heart • Tidal Volume (V ) T • Amount of air moved in and out of lungs in a single respiratory cycle • Injury to the Chest Wall • Pneumothorax allows air into pleural cavity • Atelectasis (also called a collapsed lung) is a result of pneumothorax • The Respiratory Muscles • Most important are: • The diaphragm • External intercostal muscles of the ribs • Accessory respiratory muscles • Activated when respiration increases significantly • The Mechanics of Breathing • Inhalation • Always active • Exhalation • Active or passive
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