Respiratory System Lecture Notes PDF

Respiratory system ‫د‬.‫ﺗﻐﺮﯾﺪ‬ ‫اﻟﺮﺳﻮل ﻋﺒﺪ‬  The function of the respiratory system : 1- Supply the body need for oxygen and give off carbon dioxide. 2- Maintaining homeostasis and a normal pH and participating in the body’s immune defense against bacterial and viral infections  An...

Respiratory system ‫د‬.‫ﺗﻐﺮﯾﺪ‬ ‫اﻟﺮﺳﻮل ﻋﺒﺪ‬  The function of the respiratory system : 1- Supply the body need for oxygen and give off carbon dioxide. 2- Maintaining homeostasis and a normal pH and participating in the body’s immune defense against bacterial and viral infections  Anatomically, the respiratory system can be divided into: An upper respiratory airway and a lower respiratory airway. Functionally, the respiratory system can be divided into : A conducting portion for the transportation of gases and a respiratory portion for gas exchange  The conducting portion : includes the upper respiratory airway and the lower respiratory airway. include the nasal cavity, pharynx, larynx, trachea ,extra pulmonary and intrapulmonary bronchi, bronchioles, and terminal bronchioles. The respiratory portion : includes the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. The respiratory muscles (skeletal muscles: external intercostal muscle and the diaphragm) play an important role in producing the movement of air into and out of the lung.  Conducting Portion Upper Respiratory Airway The upper respiratory airway functions as a part of the conducting portion, the conducting airway is composed of bone, cartilage, and fibrous tissue and is l i n e d w i t h st rat i f i e d s q u a m o u s a n d c i l i ate d pseudostratified columnar epithelia moistened with mucus and other glandular secretions. Cilia on the surface of the pseudostratified columnar epithelia sweep particles out of the respiratory airway  The nasal cavity Is the first portion of the upper respiratory airway. It can be divided into three regions based on the types of epithelial coverings. 1. The nasal vestibule is the most anterior part of the nasal cavity and is covered by a keratinized stratified squamous epithelium and stiff hairs is continuous with a mucosa of non keratinized stratified squamous epithelium. 2. The nasal mucosa is covered by pseudostratified ciliated epithelium (respiratory epithelium), and a layer of connective tissue beneath the lamina propria, which contains ciliated columnar cells, goblet cells, basal cells, and, occasionally, neuroendocrine cells.  The goblet cells manufacture mucus, which traps particles of dust and bacteria and moves them out of the nasal fossa, sinuses, and the nasopharynx, with the help of the ciliary action of the epithelium  The olfactory mucosa : is located in the roof of the nasal cavity and is covered by pseudostratified columnar epithelium, is composed of ciliated olfactory cells (olfactory receptor neurons), supporting cells, and basal cells in the epithelium, and of olfactory fila (unmyelinated axons) and Bowman glands in the lamina propria. The olfactory filaments (OFs), also known as olfactory fila, are among the most important structures in the olfactory system and play a key role in connecting peripheral olfactory neurons to the central nervous system  Bowman glands release their product onto the surface of the epithelium via ducts. It functions as a site for odorant chemoreceptor.  The larynx Conducts air from the pharynx to the trachea. It is supported by a set of cartilage and covered by a ciliated, pseudostratified respiratory epithelium. This mucosa continues from that of the pharynx and extends to the trachea. The laryngeal structures contains several structures, including the epiglottis, vocal co rd s , a n d n i n e p i e c e s o f cartilage located in its wall  The epiglottis is a thin leaf like plate structure its central cord contains a large piece of elastic cartilage. The epiglottis stands in front of the laryngeal inlet and bends posteriorly to cover the inlet of the larynx when food is swallowed. The epiglottis is covered by two types of epithelia: stratified squamous on the lingual surface facing the oropharynx( covers the apex of the epiglottis and about half of the laryngeal mucosa)  And respiratory epithelium on the laryngeal surface facing the larynx. Toward the base of the epiglottis on the laryngeal surface t h e l i n i n g s t ra t i f i e d s q u a m o u s e p i t h e l i u m c h a n g e s t o pseudostratified ciliated columnar epithelium. In elderly individuals, the elastic cartilage of the epiglottis is often reduced in size and is replaced by adipose tissue  The vocal cords (folds): which contain striated skeletal muscle and ligaments (mainly elastic fibers), are lined by thin non keratinized stratified squamous epithelium, which is firmly attached to the underlying vocal ligaments. The stratified squamous epithelium protects the vocal cords from mechanical stress. The main functions of the vocal cords are to control air flow and facilitate speaking.. Lower Respiratory Air: includes the trachea, bronchi, bronchioles, and terminal bronchioles. Each portion of the lower respiratory airway has unique tissue components, which facilitate oxygen delivery, gas exchange, and immune defense mechanisms. Individual airways decrease in diameter with continue branching  The trachea: Is a tube formed of cartilage and fibromuscular membrane extends from the larynx, at the cricoid cartilage to the bifurcation of the bronchi. The trachea is lined by pseudostratified ciliated columnar epithelium and reinforced by C-shaped hyaline cartilage rings.  It is composed of mucosa, submucosa, hyaline cartilage, and adventitia The mucosa : covers the inner surface of the trachea and contains respiratory epithelium and the lamina propria..  The submucosa: contains connective tissue, which is denser than the lamina propria. Hyaline cartilage : has a unique C-shape, and there are about 16 to 20 rings in the trachea. The adventitia is composed of connective tissue, which covers the outer surface of the cartilage and connects the trachea to the adjacent structures  A band of smooth muscle is located between the two ends of the C-shaped cartilage. The epithelium is composed of several cell types including goblet cells, ciliated columnar cells, basal cells, and, occasionally, neuroendocrine cells, which are also called diffuse neuroendocrine system (DNES) cell. Chronic irritation of the epithelium will lead to an increase in goblet cells and a transformation to a stratified squamous epithelium, known as squamous metaplasia.  Extrapulmonary bronchi : The trachea bifurcates to give rise to two primary bronchi which are also called extrapulmonary bronchi because they have not yet entered the lungs. Primary bronchi give rise to secondary bronchi and continue to divide into tertiary bronchi. They are structurally similar to the trachea, are lined by respiratory epithelium ( ps e u d o st rat i f i e d co l u m n a r epithelium) and have C-shaped hyaline cartilage  the left primary bronchus is narrower and less vertical than the right one and gives rise to two secondary (lobar) bronchi. The right primary bronchus is wider and shorter and more vertical than the left, it gives rise to three secondary (lobar) bronchi. That is the reason foreign body aspiration occurs more often to the right lung  Intrapulmonary bronchi : Are secondary and tertiary bronchi. As the primary (extrapulmonary) bronchi enter the hilus of the lungs they become the secondary (lobar) bronchi, which eventually divide into the tertiary (segmental) bronchi. They are lined by respiratory epithelium, and the bronchial glands (seromucous glands) are found in the submucosa  A band of spiral smooth muscle separates the lamina propria and submucosa ,the skeletal support for each intrapulmonary bronchi. As the bronchi continue branching, there is a decrease in airway diameter and in the amount of cartilage in their walls, the number of goblet cells, glands, and the height tissue of epithelial cells also decrease , increased amounts of smooth muscle and elastic tissues.  Bronchioles: Are smaller airways deriving from tertiary bronchi which continue to branch into terminal bronchioles. Bronchioles have no cartilage in their walls. Large bronchioles are lined with ciliated columnar epithelial cells a n d a g ra d u a l l y d e c re a s i n g number of goblet cells. Small bronchioles :are covered with ciliated cuboidal epithelial cells and with Clara cells. The number of Clara cells is greatly increased in the terminal bronchioles.  Terminal bronchioles :are the smallest and last of the conducting portion of the respiratory system and they have no gas exchange function. Terminal bronchioles give rise to respiratory bronchioles, which connect to the alveolar ducts, alveolar sacs, and alveoli.  Respiratory Portion of the lungs Includes the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. This portion of the respiratory system does not have cartilage and has gradually increasing numbers of alveoli. Respiratory Bronchioles: are lined by cuboidal epithelium and are interrupted by pouch like, thin walled structures called alveoli Alveoli function is the gas exchange. Respiratory bronchioles continue to branch to become alveolar ducts  A l ve o l a r d u c t s : A r i s e f ro m re s p i rato r y bronchioles. They have more alveoli and some cuboidal epithelium on the walls as compared to respiratory bronchioles. They terminate as blind pouches with clusters of alveolar sacs  Alveolar sac: is composed of two or more alveoli that share a common opening. alveolar ducts and alveoli are rich in capillaries which make gas exchange more efficient  Alveoli : are thin-walled pouches which provide the respiratory surface area for gas exchange. The wall of the alveolus is formed by a delicate layer of connective tissue with reticular and elastic fibers covered by type I and type II pneumocytes  The type I pneumocytes : are squamous cells and make up 95% to 97% of the alveolar wall. A small percentage of the alveolar wall is covered by type II pneumocytes.  Each type I pneumocyte has a flat, dark oval nucleus and very thin cytoplasm. These cells form the blood-air barrier together with the endothelial  The blood-air barrier : is an important structure for oxygen and carbon dioxide exchange. It is not easy to distinguish between type I pneumocytes and endothelial cells, because they are both squamous cells. Alveolar septa contain a blood-air its formed by d e l i c a te c o n n e c t i v e tissues (including fibroblasts, elastic, and reticular fibers) and capillaries between the alveoli, forming the alveolar septa.  Type II pneumocytes: also called septal cells or type II alveolar cells these are large polygonal cells cuboidal cells) with a large round n nucleus. They bulge into the air space, often sit at the corner of the alveoli (alveolar septa) and make up 3% to 5% of the alveolar wall. Have microvilli in their apical surfaces and contain lamellar bodies in the cytoplasm. which are mainly composed of phospholipids and proteins.  These components can be released by exocytosis into the alveolar lumen to form a thin film of pulmonary surfactant. The function of the pulmonary surfactant is to increase pulmonary compliance and decrease surface tension of the alveoli to prevent them from collapsing. Type II pneumocytes can divide and also regenerate both type I and II pneumocytes  Alveolar macrophages : Alveolar macrophages are also called dust cells; they can be found on the surface of the alveoli and in the connective tissue of the septa. They are derived from blood monocytes and migrate out of the capillaries to enter alveoli  Alveolar macrophages are irregular in shape and have round nuclei; they often contain phagocytized material (brown in color) in the cytoplasm of active cells. Their function is to remove dust particles, debris, and bacteria on the surface of the alveoli, and they may also play an important role in maintaining chronic inflammatory processes and regulating tissue repair and remodeling in the lung as well as excessive surfactant, out of the respiratory spaces