Histology of Respiratory System PDF

Histology of Respiratory System Respiratory System  Respiratory System is divided into 1-Conducting portion 2-Respiratory Connects the exterior with Portion: the respiratory portion.  Its main functions Function: site for gas are:...

Histology of Respiratory System Respiratory System  Respiratory System is divided into 1-Conducting portion 2-Respiratory Connects the exterior with Portion: the respiratory portion.  Its main functions Function: site for gas are: exchange takes place 1- Conduction  It includes: 2- Conditioning of the - Respiratory inspired air (clean, moist and warm)Nasal bronchioles cavity▪ - Alveolar ducts It includes: - - Alveolar sacs Nasopharynx , larynx, trachea, bronchi and - Alveoli (sac-like terminal bronchioles structures that form the main part of the lung). Respiratory  Epithelium The epithelium that. lines most of the conducting portion of the respiratory tract is pseudostratified columnar ciliated with goblet cells.  Five cell types are recognized in this epith:- 1- Ciliated columnar cells (most abundant) (blue arrows) 2- Mucous goblet cells(next most abundant; red arrows) 3- Brush cells (sensory receptor)  Trachea  A wide flexible tube about 10cm long that extends from larynx then bifurcates into primary bronchi toward the lung  Trachea It is kept opened all the time by the presence of formed by 16 to 20 stacked, C-shaped (incomplete) rings of hyaline cartilage along its wall. Trachea Its wall is formed of 3 layers: 1-Mucosa:  Epithelium: respiratory epithelium  Lamina propria (CT corium): loose CT containing a dense layer of elastic fibers separating it from submucosa 2-Submucosa: loose CT containing seromucous glands & lymphoid nodules 3-Adventitia: fibroelastic CT containing 20 C-shaped hyaline cartilages Trachea  Bronchial Tree  Conducting Portion. of bronchial tree: I. Extra-pulmonary(primary) bronchi II. Intrapulmonary (secondary) bronchi III. Bronchioles IV. Terminal bronchioles  Respiratory Portion of bronchial tree The walls in this portion enables gas exchange I. Respiratory bronchioles II. Alveolar ducts (Many alveoli open in their walls) III. Alveolar sacs (Number of alveoli  Conducting Portion of Bronchial Tree I- Extrapulmonary bronchi: Have exactly the same structure as trachea. III. Intrapulmonary bronchi: Its wall is formed of: - Mucosa: Pseudo stratified col. Ciliated with goblet cells (Resp. epith.) CT corium rich in elastic fibers - No submucosa - Musculosa: spiral layer of smooth muscles - Adventitia: Contains irregular plates of hyaline cartilage Seromucous glands lymph follicles Conducting Portion of Bronchial Tree Intrapulmonary Bronchi Bronchioles Are small tubes with a diameter less than 1 mm Bronchiolar wall consists of: - Mucosa: Simple columnar ciliated epith. with clara cells. Cilia disappear gradually & cells become lower as bronchioles become smaller in diameter. - Musculosa: Circularly arranged SM. - Outer layer of CT: No cartilage No glands No lymphatic nodules Bronchio les  :Clara cells Description: - Tall, dome-shaped ,non-ciliated cells present in the bronchiolar wall Function: - They protect against harmful substances that are inhaled - Act as stem cells for other types of bronchiolar epithelium. Respiratory Portion of Bronchial Tree  Alveoli  The structural and functional units of gas exchange  They are separated by inter-alveolar septa  They are lined by the alveolar epithelium which is formed of 2 types of cells :type I and type II pneumocytes lveolus is responsible for gas exchange. (b) A micrograph shows the alveolar structures within l Type I pneumocytes Type II pneumocytes: The most numerous Few in number (3%). (97%) Low cuboidal cells with Flat simple squamous round nuclei and cells with flat nuclei abundant cytoplasm Function: Connected by tight - They secrete pulmonary junctions surfactant forming a Function: It provides film over the alveolar a very thin epith. membrane through - To reduces tension and which gas exchange prevents collapse occurs during expiration. - Act as stem cells for both types. pneumocytes  Inter-alveolar Septa Are the delicate partitions separating adjacent alveoli. Have abundant blood capillaries It is composed of a network of reticular fibers to support lung tissue and prevent overexpansion that may damage the delicate blood capillaries Inter-alveolar Septa Blood-Air barrier It represents the structure. through which O2 and CO2 must cross to be exchanged It comprises 4 layers: 1- A film of pulmonary surfactant 2- The cytoplasm of type I pneumocytes 3- The fused basal lamina between type I alveolar cells and capillary endothelial cells 4- Endothelial cells of blood capillaries  References Basic histology Functional histology High- yield histology https://opentextbc.ca/anatomyandphysiology/chapter/22-1-organs-an d-structures-of-the-respiratory-system/