Histology of the Respiratory System

The respiratory system consists of 3 principle regions: conducting portion, consisting of the nasal cavity, nasopharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles. respiratory portion, consisting of respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli. 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

Conducting Portion Details of organization: presence of hyaline cartilage in the larynx, trachea, extrapulmonary and intrapulmonary bronchi. elasticity of the lungs. 3. Ciliated cells and goblet cells in the epithelium 4. Changes in the epithelium from the nasal cavity to the alveoli of the lungs: Pseudostratified Columnar => Simple Columnar =>Simple Cuboidal => Simple Squamous.

Larynx Mucosa 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

Trachea 20 C-shaped hyaline cartilages Mucosa has pseudostratified columnar epithelium with cilia and goblet cells Submucosa has mixed glands 20 C-shaped hyaline cartilages

Low Magnification of a Cross Section Through the Trachea 1. Lumen 2. Pseudostratified ciliated columnar epithelium 3. Submucosa 4. Hyalin cartilage 5. Perichondrium 6. Adventitia 7. Mixed glands 8. Secretory duct

Epithelium of the Trachea 1. Lumen 2. Cilia 3. Columnar epithelial cells 4. Prominent thick basal membrane 5. Lamina propria 6. Basal cell layer 7. Goblet cell

Bronchi anatomy: 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 cells Smooth muscle - between mucosa and cartilage Mixed glands lie between muscle layer and cartilagous plates Cartilage - Irregular shaped cartilaginous plates

Three-dimensional Representation of an Intrapulmonary Bronchus Bronchi Three-dimensional Representation of an Intrapulmonary Bronchus cartilage plate lamina 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

Bronchioles No glands or cartilage are present

Representation of the Cells of Clara Bronchioles Three-dimensional Representation of a Preterminal Bronchiole Schematic Representation of the Cells of Clara mucosa simple columnar epithelium lamina propria cells 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

Schematic Representation of a Lung Lobule 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 muscle respiratory bronchiole alveolar ducts alveoli interalveolar septum sacculus alveolaris

Respiratory Bronchiole 1. High cuboidal epithelium 2. Alveolus 3. Interalveolar septum 4. 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 sacs 2. Alveoli 3. Interalveolar septa

Epithelium of Alveoli Has two types of cells Pneumocyte (or alveolocytes) type I (Simple squamous alveolar epithelium) 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 particles 2. 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

Structure of the Interalveolar Septa secretory cell basal lamina of endothelium basale lamina of epithelium endothelium aveolar macrophage epithelium capillary endothelium alveolus surfactant diffusie van CO2 endothelial cell diffusie van CO2 simple squamous alveolar epithelial cell red blood cell Connective tissue cell alveolus

Blood Vessels Branches of pulmonary artery form capillaries in interalveolar septa (carry deoxygenated blood) Bronchial arteries supply walls of bronchi and connective tissue

Terminal Part of the Lungs

Lymphatic Drainage Run in connective tissue of the lungs ( Visceral pleura, interlobular septa and dense connective tissue surrounding the bronchi and bronchioles, arteries and veins Vessels not present in the interalveolar septa

Acinus is Structural and Functional Unit of the Lung

Lymphatic Drainage Epithelium Lamina propria Smooth muscle Cartilage Glands Lymphatic and blood vessels

Control questions Name, group Topic of the lecture Air-conducting structures – general plane of organization: -- epithelium – cells? ----another layers ?