Lecture 14 Respiratory System PDF

Lecture 14: The Respiratory System  Roles of Respiratory System Movement of air into and out of the lungs Exchange of gases (O2/CO2) between the lungs and the blood Other roles include: regulation of blood pH, speaking, sense of olfaction/smell  Struct...

Lecture 14: The Respiratory System  Roles of Respiratory System Movement of air into and out of the lungs Exchange of gases (O2/CO2) between the lungs and the blood Other roles include: regulation of blood pH, speaking, sense of olfaction/smell  Structure of Respiratory System Two subdivisions i. Upper respiratory system nose, nasal cavity, pharynx ii. Lower respiratory system larynx, trachea, bronchial tree, lungs  Structure of Respiratory System Lined with mucosa (except vestibule) Majority of passageway lined with ciliated pseudostratified epithelial cells (with mucous producing goblet cells) Connective tissue layer is known as the lamina propria  The Nose Composed of the nasal bones, cartilage and connective and adipose tissue The nostrils are also known as the nares  The Nasal Cavity Roles: Warm and moisten incoming air Olfaction (sense of smell) Speech (resonance chamber) Divided in two by nasal septum Anterior region: hyaline cartilage Posterior region: different bones  The Nasal Cavity Vestibule Anterior region lined by skin with course hair (stratified squamous epithelia) Respiratory region Posterior region lined with mucosa (ciliated pseudostratified epithelial cells)  The Nasal Cavity Contains the nasal conchae and mucus membrane-lined meatuses (grooves) Increase surface area and cause incoming air to swirl Warms and moistens incoming air  The Nasal Cavity Contains the nasal conchae and mucus membrane-lined meatuses (grooves) Increase surface area and cause incoming air to swirl Warms and moistens incoming air  The Nasal Cavity Lacrimal duct drains into the cavity below the inferior nasal conchae Tears drain into the nasal cavity  The Olfactory Area Located in the roof of the nasal cavity Involved in the sense of smell Contains neurons which act as olfactory receptors  The Paranasal Sinuses Eight air filled spaces in skull bones Open into nasal cavity Serve to warm and moisten air (and lighten the skull)  The Paranasal Sinuses Two each in the following bones: Frontal Sphenoid Ethmoid Maxillae Sinusitis = inflammation of mucous membranes of the sinuses  The Pharynx Extends from the internal nares to the top of the larynx Serves as a passageway for food and air and a resonating chamber Includes: Nasopharynx Oropharynx Laryngopharynx  The Nasopharynx Located posterior to the nasal cavity/internal nares Contains the openings to the nasal apertures and the auditory/eustachian tubes Contains the pharyngeal tonsil (adenoid)  The Oropharynx Located posterior to the oral cavity (between soft palate and top of epiglottis) Lined with stratified squamous epithelial cells  The Oropharynx Passageway for air and food Contains the palatine and lingual tonsils  The Laryngopharynx Located between the epiglottis and the opening of the larynx Lined with stratified squamous epithelial cells Passageway for air and food  The Larynx Passageway for air composed of 9 pieces of cartilage (all are composed of hyaline cartilage except the epiglottis) Thyroid cartilage – anterior wall – forms Adam’s apple Cricoid cartilage – forms complete ring  The Larynx Epiglottis – covers glottis during swallowing (composed of elastic cartilage) Arytenoid cartilages (2) – attached to the vocal cords (Also 2 cuneiform, 2 corniculate cartilages)  The Vocal Cords Two pairs of folds in the mucosa i. The vestibular folds (false vocal cords) ii. The true vocal cords (produce sound) The true vocal cords are located in an opening known as the glottis (covered by epiglottis during swallowing)  The Vocal Cords Inflammation of the vocal cords is known as laryngitis  The Trachea Connects larynx to the main bronchi Located anterior to the esophagus Consists of 20 C-shaped pieces of hyaline cartilage (opening faces the esophagus)  The Bronchial Tree Leads from the main bronchi to the alveolar ducts  The Bronchial Tree Leads from the main bronchi to the alveolar ducts  The Bronchial Tree In the lower bronchi, cartilage is replaced by smooth muscle and elastic fibers There are 2 main bronchi. These are called primary (1) bronchi.1 bronchus goes to each lung. So, the trachea splits into two primary bronchi: The right main bronchus goes to the right lung. The left main bronchus goes to the left lung. The trachea splits into two main bronchi (one for each lung).Each main bronchus then splits into lobar bronchi: There are 5 lobar bronchi in total. The right lung has 3 lobar bronchi (one for each of its three lobes).The left lung has 2 lobar bronchi (one for each of its two lobes).  The Bronchial Tree Epithelial cells in the upper bronchi are ciliated and pseudostratified Epithelial cells in the lower bronchi are non-ciliated and squamous  The Lungs Right and left lungs are separated by the mediastinum (containing the heart) Right lung: three lobes (superior, middle and inferior lobes) Left lung: two lobes (superior and inferior)/ cardiac notch where heart is  The Pleural Membrane Each lung is enclosed by its own double-layered pleural membrane Visceral pleural membrane – covers surface of the lung Parietal pleural membrane – attached to inner thoracic wall, diaphragm and mediastinum  The Pleural Membrane Pleural cavity – contains pleural fluid which reduces friction – holds lungs to the walls of the thoracic cavity  The Conduction Zone The region from the nasal cavity to the terminal bronchioles is known as the conduction zone Conducts air from the environment to the respiratory zone  The Respiratory Zone The region from the respiratory bronchioles to the alveoli is known as the respiratory zone Responsible for the exchange of gasses (O2/CO2) between the blood and the lungs  The Respiratory Zone The region from the respiratory bronchioles to the alveoli is known as the respiratory zone Responsible for the exchange of gasses (O2/CO2) between the blood and the lungs  The Respiratory Membrane Consists of the walls of the alveoli and the blood vessels Walls of blood vessels are composed of simple squamous epithelial cells and a basement membrane Walls of alveoli are composed of type I and type II alveolar cells and a basement membrane  The Respiratory Membrane Type I alveolar cells are simple squamous epithelial cells that allow for gas diffusion Type II alveolar cells are simple cuboidal cells that secrete surfactant Surfactant decreases the surface tension of the alveolar fluid  The Respiratory Membrane Alveolar macrophages move across the surface of type I cells removing foreign matter Alveolar pores allow for air movement between the alveoli  Blood Supply to the Lungs: Pulmonary Circulation Deoxygenated blood is pumped from right ventricle to pulmonary trunk then to pulmonary arteries Blood is oxygenated in respiratory capillaries in lungs Oxygenated blood returns to left atrium via pulmonary veins  Blood Supply to the Lungs: Systemic Circulation Oxygenated blood is pumped from left ventricle to bronchial arteries Blood becomes deoxygenated as it passes through lung tissue Deoxygenated blood enters bronchial veins and returns to right atrium via vena cava  Clinical Applications Pulmonary edema (Pneumonia) Tuberculosis Pulmonary embolism Pneumothorax Emphysema  Pulmonary Edema Accumulation of fluid in the lungs (in interstitial spaces and alveoli) Typically caused by heart failure (congestive heart failure)  Pneumonia Inflammation of alveoli due to infection (bacterial or viral) Immune response to infection results in damage to alveoli and the accumulation of fluid  Tuberculosis Caused by infection with the bacterium Mycobacterium tuberculosis Results in the thickening of respiratory membrane → replaced with fibrous connective tissue (scar tissue) Decreases lung elasticity and gas exchange area  Pulmonary Embolism Blockage of pulmonary blood vessels Caused by blood clots, arteriosclerosis (hardening of the arteries) or air bubbles in the blood vessels Inhibits oxygenation of blood  Pneumothorax Entry of air into the pleural cavity (between lung and chest wall) Can be caused by injury or disease Air in pleural cavity/cavities causes the lung(s) to collapse  Emphysema Breakdown of the alveolar walls due to smoking, air pollution or the inhalation of chemical fumes or dust Results in: i. larger alveoli (decreased surface area), ii. decreased elasticity (harder to breathe) and iii. decreased recoil (less air out during exhalation)  Ventilation/Breathing Requires two separate events i. Inspiration/inhalation – intake of air into the lungs ii. Expiration/exhalation – movement of air out of the lungs  Inspiration/Inhalation Contraction of the diaphragm is responsible for 75% of air entering the lungs during normal breathing  Inspiration/Inhalation Contraction of external intercostals is responsible for 25% of air entering the lungs during normal breathing Accessory muscles are used for deep, forceful inhalation  Expiration/Exhalation Normally a passive process (active during forceful breathing) External intercostals and diaphragm relax causing the lungs to contract