 This video will cover the following objective from the respiratory system, identify the major structures of the conducting zone and the respiratory zone. The mucous membrane lining the majority of the upper respiratory tract as well as the trachea is known as the respiratory mucous membrane that has a ciliated pseudo-stratified columnar epithelium that contains goblet cells which secrete mucus to help lubricate the surface and the mucus will trap particles that are inhaled and then the cilia can beat back and forth the function as the mucociliary escalator mechanism that will transport inhaled particles of dust along with mucus out of the respiratory tract the nasal cavity as well as the nasopharynx the region of the throat that connects to the nasal cavity are lined with the respiratory mucosa the mucous membrane that has a ciliated pseudo-stratified columnar epithelium then the larynx the trachea and the bronchi also are lined with the respiratory mucosa that has a ciliated pseudo-stratified columnar epithelium the region of the throat known as the oral pharynx and laryngeal pharynx that connect to the oral cavity are lined with a stratified squamous epithelium in order to resist abrasion from food that passes through those regions into the esophagus um then in the lower respiratory tract after the bronchi branch into smaller airways known as the bronchioles the mucous membrane lining the airway transitions to a simple cuboidal epithelium and then in the smallest bronchioles known as the respiratory bronchioles there's simple squamous epithelium similarly down in the the air sacs the eliolae the lining is a simple squamous epithelium air enters the nasal cavity through the external nairs also known as the nostrils into the anterior region known as the nasal vestibule then air flows through the nasal mietises which are tube shaped passageways just inferior to the nasal conchi as air flows through the mietises the pattern of airflow is turbulent which helps to increase the humidity and warm the air as it's entering the nasal cavity the superior surface of the nasal cavity is the olfactory epithelium that contains the olfactory receptors to detect odorants for the sense of smell the nasal cavity also opens into the paranasal sinuses within the sphenoid bone frontal bone ethmoid bone and maxillary bones the paranasal sinuses function to decrease the weight of the skull they also resonate vibrating air to influence the quality of our voice and they're lined with the respiratory mucous membrane of a ciliated pseudostratified columnar epithelium the nasal cavity opens into the nasopharynx through the internal nares within the nasopharynx the posterior wall of the nasopharynx contains the pharyngeal tonsil that's a mucosa associated lymphoid tissue that helps to protect against infection coming in from the nasal cavity the opening of the auditory tube is also known as the opening of the eustachian tube the auditory tube or eustachian tube is a flexible passageway of elastic cartilage that connects from the nasopharynx to the middle ear to allow the equilibration of the air pressure in the middle ear with the atmospheric air pressure the uvula is a fold of the soft palate that can move superiorly to close off the nasopharynx from the oropharynx the oropharynx is the region of the throat that connects to the oral cavity so during swallowing the uvula folds superiorly to prevent any food or drink from entering the nasopharynx and nasal cavity the palatine tonsils are found in the lateral walls of the oropharynx and our mucosa associated lymphoid tissue that helps to defend against any infection coming in from the oral cavity similarly the lingual tonsil is guarding the entrance to the oropharynx and is found in the base of the tongue the the oropharynx then connects inferior to the laryngeal pharynx the oropharynx and the laryngeal pharynx are lined with the stratified squamous epithelium to protect against the abrasion from food that passes through the oropharynx and laryngeal pharynx into the esophagus but but air will flow from the oropharynx into the laryngeal pharynx then down into the larynx so the larynx is commonly referred to as the voice box and the opening of the larynx is the glottis and so on either side of the glottis are the vocal folds or vocal cords that vibrate to produce sound for speech air will then flow from the larynx down into the trachea and so the larynx is located just anterior to the esophagus and just inferior to the highway bone at about the level of the fourth through sixth cervical vertebrae this illustration shows us the three regions of the pharynx the pharynx is commonly referred to as the throat and the superior region that connects to the nasal cavity shown in green here is the nasopharynx then the blue region in the illustration is the oral pharynx that connects to the oral cavity and the purple region shown in this illustration is the laryngeal pharynx the laryngeal pharynx which connects into the larynx as well as the esophagus the larynx consists of nine segments of cartilage the thyroid cartilage is the large anterior shield shaped hyaline cartilage on the midline is the laryngeal prominence of the thyroid cartilage which is commonly referred to as the Adam's apple and is larger in men than in women and the increased growth of the larynx in men is what contributes to the lower pitch of the voice just in fear to the thyroid cartilage is the cricoid cartilage the cricoid cartilage is a complete ring that wraps around to the posterior of the larynx the thyroid cartilage is connected to the cricoid cartilage by the cricothyroid ligament in an emergency procedure known as a cricothyrodomy the cricothyroid ligament is cut to provide an emergency airway to prevent someone from suffocating if the upper respiratory tract becomes blocked and then the trachea is located just inferior to the cricoid cartilage there are several small cartilages that are located on the posterior region of the larynx that can be viewed from the lateral illustration on the bottom here so we can see the aratnoid cartilages are located just superior to the cricoid cartilage on the posterior the aratnoid cartilages are attached to the vocal cords and muscles can move the aratnoid cartilages in order to change the tension of the vocal cords to regulate the pitch of the voice just superior to the aratnoid cartilages are the horn shaped corniculate cartilages and then just anterior to the aratnoid and corniculate cartilages located in the lateral regions of the larynx embedded in the mucous membranes known as the vestibular folds are the cuneiform cartilages so the cuneiform cartilages as well as the superior large lid of the larynx known as the epiglottis are made out of elastic cartilage and are more flexible so the epiglottis is a spoon-shaped elastic cartilage flap that projects from the anterior aspect of the larynx and folds down to close over the glottis during swallowing to prevent any food or drink from entering into the lower respiratory tract here we have a superior view of the larynx where we can look down into the opening known as the glottis on either side of the glottis are the true vocal cords which are elastic ligaments that vibrate to produce the sound of our voice just lateral to the true vocal cords are the false vocal cords also known as the vestibular folds which are mucous membranes that contain irritant receptors sensory receptors that respond to any dust particles or food or drink that touch them and will stimulate a coughing reflex to help clear the airway and prevent any particles from entering the lower respiratory tract air flows from the larynx down into the trachea the trachea is reinforced with tracheal cartilages which are c-shaped rings of hyaline cartilage that help to hold open the trachea during inspiration when the pressure of the air inside of the trachea is lower than the atmospheric pressure that low pressure could be a force that would cause the airway to collapse but the hyaline cartilage helps to hold open the trachea to prevent collapsing of the airway so the lower respiratory tract starts at the larynx and continues down towards the lungs with the trachea and the larynx as well as the trachea are lined with the respiratory mucosa of a pseudostratified columnar epithelium then the trachea will branch into the main bronchi also known as the primary bronchi which will carry air towards the lungs during inspiration or carry air out from the lungs during expiration the superior tip of each lung located deep to the clavicle is known as the apex of the lung and the inferior broader region of the lung that rests on the diaphragm is known as the base of the lung there are two lungs located within the thoracic cavity on either side of the heart the right lung contains three lobes and the left lung contains two lobes so the two lobes of the left lung are the superior and inferior lobes and they're separated by the oblique fissure the medial surface of the left lung the superior lobe contours around the shape of the heart and this contour around the heart on the medial surface of the superior lobe of the left lung is known as the cardiac notch the right lung has three lobes a superior lobe is separated from the middle lobe by the horizontal fissure and then the middle lobe is separated from the inferior lobe by the oblique fissure the lungs are surrounded by the pleural membranes which are cirrus membranes consisting of a simple squamous epithelium and an areolar connective tissue that supports that epithelium there are two layers the outer layer known as the parietal pleura lines the walls of the thoracic cavity and the inner layer known as the visceral pleura is anchored to the surface of the lungs the visceral pleura and the parietal pleura are separated by a fluid filled space known as the pleural cavity the fluid inside of that pleural cavity helps to reduce friction allowing the gliding between the pleural layers as the lungs expand during inspiration and recoil during expiration there is normally a negative pressure of the pleural cavity and that meaning that the pressure inside of the pleural cavity is lower than the atmospheric pressure it's also normally lower than the intra pulmonary or intra alveolar pressure and that negative pressure helps to create a force that holds the lungs open to prevent the lungs from collapsing at the inferior end of the trachea the last segment of tracheal cartilage is known as the carina where the trachea branches to form the primary bronchi also known as the main bronchi or the right primary bronchus and left primary bronchus the right primary bronchus connects into the right lung and the left primary bronchus connects into the left lung where the primary bronchi will then branch into the secondary bronchi which connect into the lobes of the lung and then branch further into the tertiary bronchi and the tertiary bronchi then connect into smaller segments within each lobe of the lung together the primary secondary and tertiary bronchi form the bronchial tree and the inner surface of the bronchial tree is lined with the pseudo stratified columnar epithelium and the bronchial tree is reinforced with hyaline cartilage to help prevent it from collapsing under the lower pressure during inspiration when the pressure inside is lower than the atmospheric pressure the tracheal cartilage helps to reinforce the airways preventing the airways from collapsing during inspiration the bronchioles are smaller airways that branch from the tertiary bronchi the bronchioles are not reinforced with cartilage but have a thick outer layer of smooth muscle that can regulate the diameter of the airway through the bronchioles which helps to regulate airflow the smallest branches of the bronchioles are known as the respiratory bronchioles that branch from the terminal bronchioles and so while the terminal bronchioles do not participate in gas exchange the respiratory bronchioles form part of the respiratory zone of the lung so everywhere that we've covered before the respiratory bronchioles all the larger airways the terminal bronchioles the tertiary bronchi secondary bronchi primary bronchi trachea and larynx and upper respiratory tract are all the conducting zone of the respiratory tract and the conducting zone does not directly participate in gas exchange in contrast the respiratory zone is where external respiration occurs between the air within the respiratory zone and the blood within the pulmonary capillaries so the respiratory zone includes respiratory bronchioles that then branch into smaller airways known as the alveolar ducts and each alveolar duct connects into an alveolar sac and the alveolar and the alveolar sac consists of numerous small air sacs known as alveoli the respiratory bronchioles and the alveoli have a thin wall consisting of a simple squamous epithelium and the simple squamous epithelium is surrounded by pulmonary capillaries the respiratory membrane is the location of external respiration where gas exchange occurs between the air within the respiratory zone and the blood within the pulmonary capillaries the respiratory membrane consists of the simple squamous epithelium forming the wall of the alveoli or the wall of the respiratory bronchioles and the simple squamous epithelium that forms the wall of the pulmonary capillary oxygen diffuses from the air within the respiratory zone into the blood within the pulmonary capillaries and carbon dioxide diffuses from the blood within the pulmonary capillaries out to the air within the respiratory zone there are three major types of cells found in the respiratory membrane in the wall of the alveoli and respiratory bronchioles the type one alveolar cell is the most numerous cell type found in the alveoli the type one alveolar cells are forming the simple squamous epithelium but there are interspersed type two alveolar cells that function to produce secretions known as surfactant that help to reduce the surface tension of the watery mucus lining the inner surface of the alveoli and then there are macrophages as well and the macrophages are leukocytes that help to defend against infection and remove any cellular debris or dust particles that enter into the alveoli