BIOL1410 Lecture #14 PDF

Lecture #14 The Respiratory Tract Textbook Chapter 23  The Respiratory System The primary functions of the respiratory system include: 1. The movement of air into and out of the body 2. The exchange of gases between the blood and: Lungs to the blood and cells...

Lecture #14 The Respiratory Tract Textbook Chapter 23  The Respiratory System The primary functions of the respiratory system include: 1. The movement of air into and out of the body 2. The exchange of gases between the blood and: Lungs to the blood and cells Cells to the blood to the lungs The upper respiratory tract includes: The nose The nasal cavity The pharynx The lower respiratory tract includes: The larynx The trachea The bronchial tree The lungs  The Nose The nose is the only external portion of the respiratory tract The nasal cavity functions to: 1. Provide an opening for respiration 2. Moisten and warm incoming air 3. Filter incoming air, removing dust and dirt particles 4. Olfaction (smell) 5. Speech The external portion of the nose is composed of: Bone and hyaline cartilage The exterior portion is composed of skin and muscle The nostrils are the exterior openings that transport air into the nasal cavity Called the external nares  The Nose The interior portion of the nose is called the nasal cavity The nasal septum divides the nose into the right and left half The anterior portion of the nasal cavity is composed of hyaline cartilage The posterior portion of the nasal cavity is formed by the vomer, maxillae, and palatine bone in addition to a small portion of the ethmoid bone  The Nose There are four main nasal cavity divisions: 1. The right and the left sides of the cavity Divided by the nasal septum and bordered by the ethmoid bones, the vomer and cartilage 2. The anterior vestibule: Skin that is lined with coarse hairs 3. The olfactory mucosa: Bordered by the roof of the nasal cavity Contains receptors used for smellà olfactory receptors Pseudostratified columnar epithelium containing neurons, does not contain goblet cells The lamina propria contains glands that secrete fluid to moisten incoming air 4. The respiratory mucosa: Mucosaà lined with mucous membrane Epithelial layer is pseudostratified columnar, ciliated and contains mucous secreting goblet cells Lamina propria forms the connective tissue component  The Nose On the lateral walls of the nasal cavity there are nasal conchae Divided by meatusesà passageways for incoming air to travel along Three nasal conchae and three meatuses Superior Composed of the ethmoid bone Middle Inferior: composed of a separate bone The conchae and meatuses function to generate turbulence and warm incoming air The lacrimal duct (teat duct) opens into the nasal cavity inferior to the nasal conchae  The Nose Openings associated with the nasal cavity include: External naris Internal naris Lacrimal ducts Paranasal sinuses: Open into the nasal cavity Found in the frontal, sphenoid, ethmoid, and maxillary bones Lined with ciliated, pseudostratified columnar epithelium Function to warm and moisten air and to reduce the weight of the skull When the mucous membrane of the paranasal sinuses become inflamed the condition is called sinusitis  The Nose Total functions of the nose and the nasal cavity are: Mucous production Warming of incoming air Filtering of incoming air Moistening of incoming air Facilitate proper speech Olfaction (smell)  The Pharynx The pharynx wall contains skeletal muscles Lined with mucous membrane Constitutes what is commonly known as the throat Begins past the internal nares and the posterior part of the mouth Divided into three main portions: The nasopharynx The oropharynx The laryngopharynx  The Pharynx 1. The nasopharynx: Located posterior to the nasal cavityà functions only in respiration Formed from ciliated, pseudostratified columnar epithelium Contains the pharyngeal tonsils (the adenoid)à located on the posterior wall of the nasopharynx The uvula (hangy ball) at the back of the throat is located here Together with the soft palate the uvula moves superiorly to block off the nasal cavityà prevents food from entering the nasal cavity Forms a passageway for air The two internal nares and the two eustachian tubes open into the nasopharynx  The Pharynx 2. The oropharynx: The area of the pharynx that we refer to as the throat The oropharynx is located posterior to the oral cavity/mouth The mucosa is lined with stratified squamous epithelium to resist abrasion Extends from the soft palate to the tip of the epiglottis Epiglottis blocks the airway/tracheal opening during swallowingà prevents food from entering the lungs/choking Serves as a dual passageway for air and food The lingual (at the base of the tongue) and the palatine (removed during tonsillectomy) tonsils are located in the oropharynx  The Pharynx 3. The laryngopharynx: Stretches from the epiglottis to the tip of the thyroid cartilage Opens into the larynx and the esophagus Lined with stratified squamous epithelium Functions to transport both food and air  The Larynx The larynx is the voice box Composed primarily of hyaline cartilage Serves as a connection between the pharynx and the trachea Only moves airà no food Laryngitis is the inflammation of the larynx mucosa Consists of: 1. Paired cartilage 2. Unpaired cartilage  The Larynx 1. Unpaired cartilage: a. Thyroidà made of hyaline cartilage Located on the anterior wall of the larynx Commonly known as the Adam’s apple Male Adam’s apple is more pronounced than in females because of differing testosterone levels b. Cricoidà ring of hyaline cartilage c. Epiglottisà formed from elastic cartilage Functions to cover and protect the glottis during swallowing 2. Paired cartilage: There are three All made from hyaline cartilage Arytenoidà functions to attach the vocal cords  The Larynx The vocal cords: Ligaments composed of elastic fibers Folds that form the vocal cords Either true or false 1. False vocal cords: Formed from the superior fold of the membraneà called the vestibular fold Helps you to hold your breath Closes the larynx 2. True vocal cords: Formed from inferior folds of the mucous membrane Pearl white in color because they do not contain blood vessels Produce sound by vibrating Prevents food and liquids from entering the trachea Glottis consists of true vocal cords AND the opening  The Trachea The trachea is located anterior to the esophagus Transports food to the stomach Connects the larynx to the right and left primary bronchi Consists of 20 C-shaped pieces of hyaline cartilage The open portion of the C faces the esophagus allowing for esophageal expansion during swallowing The C itself faces the anterior portion of the trachea and protects against tracheal collapse Composed of ciliated, pseudostratified columnar epithelium Contains goblet cells for mucus secretion  The Bronchial Tree The stretches from the primary bronchi to the alveolar ducts There is decreasing quantities of cartilage as you move from the trachea to the inner lung There is also an increasing quantity of smooth muscle There are two primary bronchi, right and left that contain incomplete rings of hyaline cartilage The primary bronchi each branch into secondary (lobar) bronchi that have plates of hyaline cartilage There are three secondary bronchi in the right lung and two secondary bronchi in the left lung The number of secondary bronchi do not match between the two lungs because there is one per lobe of each lung  The Bronchial Tree The secondary bronchi then branch into many tertiary (segmental) bronchi Contain irregular plates of cartilage The tertiary bronchi then branch into a number of bronchioles The bronchioles branch further becoming terminal bronchioles Terminal bronchioles then branch into respiratory bronchioles Do not contain cartilageà only smooth muscle and elastin Respiratory bronchioles then move into alveolar ducts Do not contain cartilageà only smooth muscle and elastin  Alveoli Alveolar ducts terminate as alveolar sacs Each alveolar sac is composed of multiple alveoli (alveolus: singular) Alveoli are the sites of gas exchange ~300 million alveoli per lung Increase the surface area for gas exchange O2 gas enters into the blood and CO2 exits the blood, entering the lung to go on and exit the body  Respiratory Epithelium There is a change in the type of mucosal epithelium as you progress from the primary bronchi to the alveoli Primary bronchi: ciliated pseudostratified columnar epithelium with goblet cells Large bronchioles: ciliated simple columnar epithelium with goblet cells Small bronchioles: ciliated simple cuboidal epithelium without goblet cells Terminal bronchioles: non-ciliated simple cuboidal epithelium Alveolar ducts: non-ciliated simple squamous epithelium The bulk of the respiratory tract is lined with ciliated pseudostratified columnar epithelium  The Lungs The right and the left lung are separated from one another by the mediastinum The left lung contains two lobes: Superior lobe Inferior lobe Also contains the cardiac notch which is an indent where the heart lies The right lung contains three lobes: Superior lobe Middle lobe Inferior lobe  The Lungs The lungs are surrounded by pleura A serous membrane The visceral pleura contacts the surface of the lung The parietal pleura lines the wall of the thoracic cavity Lines the superior surface of the diaphragm and runs along the mediastinum The pleural cavity is the area between the two pleura membranes Contains serous fluid Prevents the visceral and the parietal pleura from sticking to one another Reduces friction Also holds the lungs to the wall of the thoracic cavity The lungs are innervated by the autonomic nervous system  The Respiratory Membranes The respiratory membranes are moist, thin (0.0005mm) and highly vascular This is the primary site of gas exchange between the lung and the blood O2 is loaded into the blood from the lung and CO2 is unloaded from the blood into the lung The respiratory membrane is composed of four layers 2 epithelial layers each fused to a basement membrane Composed of: 1. The wall of the alveolus and the alveolar basement membrane 2. The wall of the capillary and the capillary basement membrane  The Respiratory Membranes 1. The wall of the alveolus: Composed of simple epithelium with three cell types a. Type I alveolar cells: Composed of simple squamous epithelium The site of O2 and CO2 exchange b. Type II alveolar cells: Composed of simple cuboidal epithelium Secrete an alveolar fluid containing surfactantà composed of lipoprotein and phospholipids that serves to reduce surface tension on the alveolar surface The exposed/free surface of the alveoli contains microvilli that will increase the surface area c. Macrophages: Remove dust, pollen and debris from incoming air No cilia in this part of the lung Able to move freely across the alveolar surface 2. Elastic epithelial basement membrane  The Respiratory Membranes 3. The capillary basement membrane: Fused to the alveolar basement membrane 4. The wall of the capillaryà capillary endothelium: Composed of endothelial cells that form a simple squamous epithelial layer Infection with Mycobacterium tuberculosis The causative agent of tuberculosis Infection thickens the respiratory membrane Membrane tissue is replaced with fibrous connective tissueà scar tissue Decreases the elasticity of the lung Decreased capacity for gas exchange  Blood Supply to the Lungs Pulmonary circulation Blood moves from the right ventricle of the heart to the pulmonary arteries From the pulmonary arteries blood moves to the lungs From the lungs blood returns through the pulmonary veins to the left atrium of the heart Systemic circulation Blood moves from the left atrium to the left ventricle to the aorta From the aorta blood moves to the bronchial arteries The bronchial arteries deliver blood to the cells that form the walls of the bronchi and the bronchiolesà provide a meal and O2 to keep these cells alive From the cells of the lung blood returns to the bronchial vein The bronchial vein returns blood to superior vena cava where it enters the right atrium  Blood Supply to the Lungs Bronchial arteries: Branch off of the descending aorta which is delivering blood into systemic circulation These arteries carry oxygenated, nutrient rich blood to the respiratory tissues These tissues have no other source of O2 and nutrients Pulmonary tissues are not able to exchange gases with the blood that they are carrying Blood returns to the bronchial vein which empties into the right atrium This is a small proportion of the blood that enters into the right atrium Most of the blood from the lungs enters the left atrium via the pulmonary veins https://www.pediagenosis.com/2018/10/arteries-of-esophagus-anatomy.html  Muscles of Respiration All of the respiratory muscles are skeletal muscles Inhalation: The intake of air During regular inhalation the diaphragm and the external intercostal muscles contract During forced inhalation the diaphragm, the external intercostals, the pectoralis minor, the scalene and the sternocleidomastoids contract Exhalation: The movement of air from the lungs to the atmosphere During regular exhalation the diaphragm and the external intercostal muscles relax During forced exhalation the internal intercostals and the abdominal muscles contract Respiration is controlled by the brain and the concentration of CO2 in the blood  Clinical Applications 1. Pulmonary edema: This is the accumulation of fluid in the interstitial space and the alveoli 2. Pulmonary embolism: This is caused by a blockage in the pulmonary circulatory route Usually caused by: a blood clot that has broken free, fat, air This can cause death 3. Pneumothorax: This is caused by entry of air into the pleural cavity Causes the lung to collapse 4. Emphysema: Caused by the enlargement and the destruction of the alveolar wall Due to the inability to inhibit proteases in the lungs Smoking leads to an accumulation of neutrophilsà release proteases Smoking also inhibits protease inhibitors Results in larger alveoli with decreased elasticityà breathing/recoil more difficult