histology - respiratory system recording
TRANSCRIPT
What we’ll talk about…
• Histological structures of conducting airways
• Histological structures that facilitate gas exchange
• Properties of alveoli that control ventilation
• Macrophages and handling of foreign particles
Rate of gas diffusion between air and blood is related to the surface area and thickness of the interface.
·V = kA ⋅ s
a ⋅ MW(PAir − PBlood)
Air Blood
O2O2
Water
O2
Surface Area of Barrier
Thickness of Barrier
Pressure of Gas in Air
Pressure of Gas in BloodRate of Diffusion
The respiratory system comprises conducting and gas exchange segments.
Functions of Conducting Airways• Facilitate flow of air
• Condition air
• Clear air
Trachea
The trachea connects the larynx to primary bronchi and contains cartilage rings.
Glands
Cartilage
Trachealis Muscle
The wall of the trachea contains ciliated, pseudostratifed epithelium, cartilage and glands.
Epithelium
Basement Membrane
Lamina Propria
Submucosa
Cartilage
Glands
The mucosal layer of the respiratory tract consist of epithelia, basement membrane and lamina propria.
Basement Membrane
Lamina Propria
Cilia
Mucus Cells
Epithelium
The respiratory system comprises conducting and gas exchange segments.
Bronchi contain pseudostratified epithelium and cartilage plates.
Cartilage Plate
Epithelium
Smooth Muscle
Glands
Bronchioles contain simple columnar epithelium and lack cartilage plates.
Epithelium
Smooth Muscle
Alveolus
Respiratory Airways
Respiratory bronchioles and alveoli compose the gas exchange portion of the lung.
The gas exchange portion comprises respiratory bronchioles, alveolar ducts and sacs and alveoli.
Terminal Bronchiole
Alveoli
Alveolar Sac
Respiratory Bronchioles
Alveolar Duct
Alveoli
Walls of alveoli consist of pneumocytes, capillaries and connective tissue.
Capillaries
Type II Pneumocyte
Air
Air
Type I Pneumocytes
Type I Pneumocyte
Type I pneumocytes are squamous and surround capillaries; type II pneumocytes are cuboidal.
Type II Pneumocyte
Capillary
CapillaryAir
Air
Type I Pneumocyte
Type I Pneumocyte
Lamellar Body
The gas exchange barrier comprises type I pneumocyte, basement membrane and endothelium.
Type I PneumocyteAir
Air
Blood
Basement Membrane
Basement MembraneType I Pneumocyte
Endothelial Cell
Type I and type II pneumocytes absorb fluid from the lumen via vectorial transport of sodium and chloride.
Na+K+
AQP5
Na-K Pump
Na+
K+
K Channel
H2O K+
Na+
Na-K Pump K Channel
K+
ENaC
ENaC
CFTR
CFTR
Na+
Cl-
Cl-
Type I Cell
Type II Cell
Club Cell
K+
K+
Na+
Na+
ENaC CFTR
Alveolus
Alveolar macrophages (dust cells) reside in the airway and engulf particles and microorganisms.
Capillary
Alveolar Macrophage
Air
Pulmonary Circulation
Pulmonary system delivers deoxygenated blood and bronchial system delivers oxygenated blood.
Pulmonary Artery Pulmonary Vein
Blood from right ventricle
Blood to left atrium
Bronchiole Artery
Blood from left ventricle
Alveoli
Air from trachea
Bronchus
Pulmonary arterioles have thinner walls and generate less resistance than typical arterioles.
Pulmonary Arteriole Typical Arteriole
Structural arrangement of airways and rate of ventilation
Lung section reveals bronchus, bronchioles, alveoli and blow vessels.
BronchusBronchiole
Cartilage Plate
Pulmonary Vessel
Alveoli
Pulmonary Vessel
Composition and structure of alveoli determine compliance of lung.
C =ΔVΔP
Compliance
Lung Volume Change
Intrapleural Pressure Change
Factors that Affect Compliance• Alveolar surface tension• Alveolar elastic fibers• Alveolar collagen fibers
AlveoliPleural Surface
Intrapleural Fluid
Handling Inhaled Particles
The diameter of foreign particles determines their depth of penetration into lungs.
Total
Trachea
Bronchi
Bronchioles
Alveoli
Macrophages engulf inhaled foreign particles.
Macrophage
Macrophage
Take home messages…
• Trachea and bronchi have ciliated, pseudostratified epithelium and cartilage to prevent collapse
• Bronchioles lack cartilage plates
• The gas exchange barrier consists of type I pneumocytes, endothelial cells and their shared basement membrane
• Pneumocytes facilitate fluid absorption from the airway
• Surface tension and connective tissue in alveoli resist expansion and facilitate expiration
• Macrophages (dust cells) engulf foreign particles and microorganisms