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Histology of the Respiratory System
The respiratory system consists of 3 principle regions: 1. conducting portion, consisting of the nasal cavity, nasopharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles. 2. respiratory portion, consisting of respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli.3. structures of ventilating mechanism, which creates pressure differences that move air. It includes the diaphragm, rib cage, intercostal muscles, abdominal muscles and elastic connective tissue in the lungs.
Conducting Portion
System of ducts --- conducts air to alveoli in the lungs
Function --- Conditioning of the air --- Warming, moistening and removal of particulate materials
Details of organization: 1.presence of hyaline cartilage in the larynx, trachea,
extrapulmonary and intrapulmonary bronchi. 2.elasticity of the lungs.
3. Ciliated cells and goblet cells in the epithelium4. Changes in the epithelium from the nasal cavity to
the alveoli of the lungs:Pseudostratified Columnar => Simple Columnar
=>Simple Cuboidal => Simple Squamous.
Conducting Portion
Larynx Tube kept open hyaline or elastic (Epiglottis)
cartilage Skeletal muscle surrounds cartilage on outside
and present between the cartilage and mucosa
Mucosa Pseudostratified columnar epithelium containing
cilia and goblet cells Unkeratinized stratified squamous epithelium –
only in the epiglottis and the vocal folds
Mucosa has pseudostratified columnar epithelium with cilia and goblet cells
Submucosa has mixed glands 20 C-shaped hyaline cartilages
Trachea
Low Magnification of a Cross Section Through the Trachea
1. Lumen2. Pseudostratified ciliated
columnar epithelium3. Submucosa4. Hyalin cartilage5. Perichondrium6. Adventitia7. Mixed glands8. Secretory duct
Epithelium of the Trachea
1. Lumen2. Cilia3. Columnar epithelial cells4. Prominent thick basal membrane5. Lamina propria6. Basal cell layer7. Goblet cell
Bronchianatomy:
Two main extrapulmonary bronchi -- histologically similar to the trachea
Intrapulmonary bronchi– Primary bronchi - Lobar bronchi - Secondary bronchi -- Segmental bronchi- Tertiary bronchi - interlobular bronchi
Intrapulmonary Bronchi Pseudostratified columnar epithelium
containing cilia and goblet cellsSmooth muscle - between mucosa
and cartilage Mixed glands lie between muscle
layer and cartilagous plates Cartilage - Irregular shaped
cartilaginous plates
Bronchi Three-dimensional Representation of an Intrapulmonary Bronchus
cartilage platelamina propria
pseudostratified columnar epithelium with cilia and goblet cells
smooth muscle
Bronchioles – smallest branches of bronchi:
Preterminal bronchiole penetrate lobule at its apex and enter inside the lobule, branches into terminal bronchioles
Bronchioles:Epithelium
in the larger bronchioles -- Simple columnar, in smaller bronchioles --- tall cuboidal
Goblet cells have disapeared and cells of Clara (tall, non-ciliated
secretory cells, produce surfactant) – apeare
BronchiolesNo glands or cartilage are present
Bronchioles Three-dimensional
Representation of a Preterminal
Bronchiole Schematic
Representation of the Cells of Clara
mucosasimple columnar epitheliumlamina propriacells of Clara
smooth muscle
neuro-epithelial body
cells of Clara
Respiratory Portion
Respiratory Portion
Consists of smaller ducts and sacs Lie inside lung lobules Provides exchange of gases
Lung Lobules Schematic Representation of a Lung Lobule
bronchiolus
pulmonary artery
lymphatic vessel
pulmonary vein
preterminal bronchiole
respiratory bronchioles
alveoli
visceral layer
parietal layer
Respiratory Bronchioles
Branch from terminal bronchioles and have Alveoli - thin bulging sacs - in walls
Gas exchange takes place in alveoli
Respiratory Bronchioles Schematic of the Respiratory
Portion of a Lung Lobule
Smooth musclerespiratory bronchiole
alveolar ductsalveoli
interalveolar septum
sacculus alveolaris
Respiratory Bronchiole
1. High cuboidal epithelium2. Alveolus
3. Interalveolar septum4. Lumen
Alveolar ducts -- long air passages , Alveolar sacs – round air spaces surrounded by clusters of
alveoli
Interalveolar septa – connective tisue - separate neighboring alveoli
Alveolar pores -- direct contact between 2 alveoli
The Lung Demonstrating the Basic Structures
1. Alveolar sacs2. Alveoli3. Interalveolar septa
Epithelium of Alveoli
Has two types of cells 1. Pneumocyte (or alveolocytes) type I (Simple
squamous alveolar epithelium)
2. Pneumocyte type II (Surfactant secreting cells) (NOTE: surfactant decrease surface tension in alveoli preventing their collapsing)
Alveolar macrophages (dust cells) – present in the cavity
1. Carbon particles2. Pneumocyte type II (Surfactant secreting cells)3. Pneumocyte type I
Barrier between Air and Blood
Cytoplasm of epithelium lining the alveoli Basal lamina of the epithelium Basal lamina of the capillary endothelium Cytoplasm of capillary endothelium
Blood Vessels
Branches of pulmonary artery form capillaries in interalveolar septa (carry deoxygenated blood)
Bronchial arteries supply walls of bronchi and connective tissue
Acinus is Structural and Functional Unit of the Lung
Control questions
Name, group Topic of the lecture Air-conducting structures – general plane
of organization:
-- epithelium – cells?
----another layers ?