University:
Glendale Community College
Course:
BIO160 | Introduction to Human Anatomy and Physiology
Academic year:

2022
Views:

243

Pages:

31
Author:

Peyton Russell

Lower Respiratory Tract (trachea and lungs) Trachea • Semi-rigid tube 4.5” long and 2.5” in diameter, anterior to esophagus is supported by C-shaped cartilaginous rings – Opening in rings faces posterior towards esophagus – Trachealis Muscle spans opening in rings, adjusts airflow by relaxing while breathing or contracting when coughing • Bifurcates into right and left Primary Bronchi – Carina is the extremely sensitive, bifurcated terminal segment of the trachea – Sensory epithelia ends below the carina – Right primary bronchus is more likely to contain aspirated objects because it is wider and more vertical • Larynx and trachea are lined with ciliated pseudostratified epithelium – epithelium has many goblet cells – lamina propria contains many mucous glands – functions as mucociliary escalator that sweeps mucus up to pharynx Mucociliary Escalator Lungs and Bronchial Tree Bronchial Tree • Primary Bronchi – two branches of the trachea – one goes to each lung – supported with rings of cartilage • Secondary Bronchi – one secondary bronchus for each lobe of a lung • right lung has 3 lobes • left lung has 2 lobes – supported with overlapping plates of cartilage • Tertiary Bronchi supply bronchopulmonary segments • 10 in right lung • 8 in left lung – supported by fewer plates of cartilage • Bronchioles – surrounded by smooth muscle and no supporting cartilage – divide into 50-80 terminal bronchioles Bronchial Tree and Bronchopulmonary Segments Normal Lateral Bronchography Bronchopulmonary Segments Bronchial Tree (- continued) • Terminal Bronchioles – last bronchial segment without any alveoli – have some smooth muscle – divide into respiratory bronchioles • Respiratory Bronchioles – bronchioles with a few alveoli – alveoli are pockets of thin respiratory tissue • Alveolar Ducts – short tubes with walls composed of alveoli • Alveolar Sacs – clusters of alveoli Alveolar Blood Supply Cells of the Alveoli • Type I Pneumocytes (squamous alveolar cells) – epithelial cells that line the alveoli • Type II Pneumocytes (great alveolar cells) – Secrete pulmonary surfactant (detergent-like lipoprotein) • Alveolar Macrophages – Outnumber all other cell types in the lung – 50 million a day move out of the lungs into the mucociliary escalator to be swallowed Structure of an Alveolus erythrocytes Alveolar Surface Tension • A thin film of water is necessary for gas exchange – O2 and CO2 must dissolve in water to be absorbed – Water creates a strong surface tension that can easily collapse alveoli and distal bronchioles • Pulmonary Surfactant – Produced by Type II Pneumocytes (great alveolar cells) – A protein and lipid mixture that disrupts hydrogen bonds of water,  surface tension – Develops late in fetal development – must be administered to premature infants to prevent respiratory distress syndrome Alveolar Macrophages macrophages Macrophages that have ingested carbon particles Macrophage ingesting asbestos fibers Macrophage trying to ingest a stone flake Pleurae and Pleural Fluid • Visceral Pleura – membrane attached to surface of lung tissue • Parietal Pleura – membrane attached to the inner thoracic wall • Pleural Cavity contains a thin film of Pleural Fluid • Functions of Pleurae and Pleural Fluid: – reduces friction – membranes separate areas of low pressure and high pressure • lower pressure in pleural cavity is necessary to inflate the lungs – membranes compartmentalize each lung • prevents spread of infection Thorax - Cross Section Pressure and Flow • Atmospheric pressure drives respiration – 1 atmosphere (atm) = 760 mmHg = 14.7 psi at sea level – Atmospheric pressure decreases as elevation increases – Every 33’ below water is equal to 1 atm • A diver 66’ below the surface would be under 3 atmospheres of pressure • Intrapulmonary pressure and lung volume – Boyle’s Law states that pressure is inversely proportional to volume • for a given amount of gas, as volume , pressure  • and as pressure , volume  • Pressure gradients – difference between atmospheric and intrapulmonary pressure – created by changes in volume of thoracic cavity Respiratory Pressure & Lung Ventilation Muscles Involved in Inspiration • Diaphragm (dome shaped) – contraction flattens diaphragm and increases volume of thorax • Scalenes – fix first pair of ribs • External intercostals – elevate 2 - 12 pairs • Pectoralis minor, sternocleidomastoid and erector spinae muscles – used in deep inspiration to expand thorax Muscles Involved in Inspiration Passive Expiration • During quiet breathing, expiration is achieved by elastic recoil of lungs and thoracic cage • As volume of thoracic cavity , intrapulmonary pressure  and air is expelled Forced Expiration • Internal intercostal muscles – depress the ribs • Abdominal muscles – Contraction of abdomen  intra-abdominal pressure and forces diaphragm upward which  pressure in thoracic cavity Pneumothorax • Presence of air in pleural cavity – loss of negative intrapleural pressure allows lungs to recoil and collapse • Collapse of lung can be corrected by inserting a tube into the intrapleural space and applying suction The pleura is usually not seen in CT. It may be recognized as a dense line when, with a pneumothorax, the lung retracts from the thoracic wall, as seen in this case. Measuring Air Pressure with a Mercury Manometer A) equal pressure B) low atmospheric pressure C) high atmospheric pressure Composition of Air • Air is a mixture of gases, and each gas contributes its partial pressure (at sea level 1 atm of pressure = 760 mmHg) – nitrogen constitutes 78.6% of the atmosphere, therefore PN2 = 78.6% x 760 mmHg = 597.0 mmHg – PO2 = 20.8% x 760mmHg = 159.0 mmHg – PH2O = 0.50% x 760 mmHg = 3.7 mmHg – PCO2 = 0.04% x 760 mmHg = 0.3 mmHg – ATM = 597 + 159 + 3.7 + 0.3 = 760 – All other gasses contribute an insignificant amount to the total partial pressure • Partial pressures determine rate of diffusion of gas between blood and alveolus. • Alveolar air – 100% humid, gases dissolve in water and diffuse into blood – contains: PN2 = 569, PO2 = 104, PH2O = 47, PCO2 = 40 mmHg Air-Water Interface • Gases diffuse down their concentration gradients from high concentration to low concentration • Henry’s Law: amount of gas that dissolves in water is determined by its solubility in water and its partial pressure. gas solubility in water (g/kg water) Nitrogen 0.03 Oxygen 0.07 Carbon Dioxide 3.40 Concentration Gradients of Gases