Respiratory Anatomy PDF

# Respiratory Anatomy ## Function of Respiratory System * Conducts air to the respiratory surfaces * O2 and CO2 are exchanged with the blood (circulatory system) * Conditions the air (warms, humidifies, cleans) before reaching the respiratory tissues * Important role in maintenance of body pH * Se...

# Respiratory Anatomy ## Function of Respiratory System * Conducts air to the respiratory surfaces * O2 and CO2 are exchanged with the blood (circulatory system) * Conditions the air (warms, humidifies, cleans) before reaching the respiratory tissues * Important role in maintenance of body pH * Secondary structures for olfaction and vocalization ## Functional Zones ### Conducting Zone * The various passages that convey air between the external environment and the respiratory surfaces. * Structures are lined with epithelial cells that secrete, filter, protect and actively clear debris. * Support provided by muscle, bone and cartilage. ### Respiratory Zone * The highly vascularized / perfused region where gas exchange actually takes place. * Thin moist membranes and an absence of bony or cartilaginous support structures. ## Structural Divisions ### Upper Resp. Tract * Nasal cavity, oral cavity and pharynx, larynx (boarder) * Important for warming and conditioning of air ### Lower Resp. Tract * Trachea, and multiple generations of airways (bronchial tree) * Proximal elements are cartilaginous; distal are noncartilaginous # Upper Respiratory Tract ## Nasal Cavity * The point of entry for external air. * Projects anteriorly as cartilaginous portion of the nose. * Extends posteriorly to communicate with the pharynx (respiratory and digestive). ## Paranasal Sinuses * Mucous membrane lined spaces in the skull named for the specific skull bone. * Ciliated epithelia move mucous from sinuses to nasal cavity through paranasal ducts. * Humidify/warm air, voice resonance, lighten skull bones. ## Nasal Cavity ### Nasolacrimal Ducts * Lead from orbit to the lateral walls of the nasal cavity. * Tears pass into the nasal cavity from lacrimal glands. ### Auditory (Eustachian) Tubes * Connect middle ear with lateral wall of post. pharynx. * Equalization of air pressure. ## Nasal Epithelia * Respiratory pathways are necessarily exposed to the external environment. * Epithelial tissues = high turnover (cellular regeneration) Why is this particularly important in this case? Where else are such characteristics desirable? * Mucous (specialized cells) is moved posteriorly by cilia (also produced in paranasal sinuses). ## Functions of the Nasal Cavity ### Conditioning of Inspired Air * Vascular epithelium well suited to warming. * The moist mucous helps to humidify the incoming air. * As air moves through the turbinates of the nasal conchae, particles such as dust, smoke, pollen are filtered out and trapped in the mucous. * Conditioned air ensures that gas exchange is more efficient with respiratory membranes: Warm (body temp.), humid, "clean". ### Olfaction * Nonrespiratory function of the nasal cavity. * Olfactory receptors on the roof of the nasal cavity. * Axons from receptors form olfactory nerve branches (CN(1). ### Phonation * Air exhaled through the nose lends resonance to the voice. * How do you sound when you have a cold? # Oral Cavity * Secondary respiratory passage. * Clinically important in procedures such as endotracheal intubation (Why the mouth?) * Failure of the right and left maxillary bones to fuse embryologically results in a cleft palate. * Abnormal communication between nasal and oral cavities. # Pharynx (common passageway) ## Nasopharynx (respiratory role) * Continuous with the posterior nasal cavity. * Mucous (trapped debris) moved posteriorly by cilia. * Eustachian tubes (to middle ear) located in lateral walls. * Adenoids (pharyngeal tonsils) on posterior walls. ## Oropharynx (digestive and respiratory role) * Region between the soft palate and hyoid bone containing the lingual tonsils and palatine tonsils (What do they do?) ## Laryngopharynx (distal structure of upper RT) * Marks boarder of proximal larynx where air is diverted anteriorly into trachea. * Hypopharynx? # Larynx * Located on anterior midline of the neck between C4-C6. * Flexible cartilages connected by ligaments and membranes. * Conducts air, prevents aspiration, vocalizations. * Rima glottidis - slit between vocal cords (prone to edema / obstruction) # Lower Respiratory Tract ## Trachea * Maintained by cartilage rings (incomplete posteriorly). * Lumen lined with ciliated respiratory epithelium. * Main conducting tube for air to both lungs. * Bifurcates into a right and left primary bronchi ## Tracheobronchial Tree ### Primary Bronchi * C-shaped hyaline cartilage maintains airway patency. * Right 1º bronchus is shorter, larger diameter and more vertical than left (aspirated objects?) ### Secondary Bronchi (lobar) * Connect the 1º bronchi to the lobes of the lung. * 3 on right and 2 on the left. * Supported by smaller plates of cartilage. ## Tracheobronchial Tree ### Tertiary Bronchi (segmental) * Supply bronchopulmonary segments within each lobe. * 10 on right / 8 on left. ### Subsegmental Bronchi * Last cartilaginous airways. ### Bronchioles * Noncartilaginous and <1mm diameter. * Support provided by connections to surrounding parenchyma (Explain!) * Double spirals of smooth muscle surround bronchioles (bronchomotor tone) ## Tracheobronchial Tree ### Terminal Bronchioles * Final elements of the conducting zone. * Gradual loss of cilia/mucous cells and decrease in epithelial cell thickness. ## What is an Alveolar Duct? ## Tracheobronchial Tree ## Alveoli * **Beginning of “respiratory zone”** * Terminal bronchioles give rise to respiratory bronchioles→ alveolar ducts → terminate in the alveolar sacs (note structure) * Individual alveoli consist of a very thin squamous epithelium * **Ideal for gas exchange** * 300 million alveoli organized into 130,000 acini (respiratory units) * *Extensive surface area!!* ## Alveolar Structure/Function * Network of pulmonary capillaries. * Small diffusion distance (.35µm) * *Note arrangement*. * Diameter of capillaries permits movement of red blood cells in "single file" (slow) * About 5% of alveolar surface area is composed of cells that produce pulmonary surfactant (Type II pneumocytes). * Surfactant lines the luminal surface of each alveolus and prevents collapse by reducing surface tension. # The Lung * Fissures divide lungs into lobes (3 right, 2 left) * Hilum: opening in medial surface for passage of: pulmonary vessels, bronchi, nerves, lymphatics # The Lung * Apex at level of clavicle. * Base follows diaphragm contour. * Base extends posteriorly to 11th rib/anteriorly to 6th rib. * Medial surface (mediastinal) is slightly concave. * Lateral surface slightly convex - costal impressions. # Pleura * Double membrane houses each lung (secrete fluid). * Parietal: outermost layer lining thorax/diaphragm. * Visceral: inner layer adheres to each lung. * Pleural cavity: thin fluid space between the layers. * allows layers to adhere during ventilation. * Reduces friction during ventilation (painless). # The Lung Surface * Right lung is larger than the left. * Interlobar fissures. * Visceral pleura extend into interlobar fissures # Lobes of the Lungs * Note that each lung is divided into lobes associated with the secondary (lobar) bronchi. * Left lung >> 2 lobes. * Right lung >> 3 lobes. # Bronchopulmonary Segments * Lungs are further divided into **bronchopulmonary segments**, associated with the tertiary (segmental) bronchi.