List the structures that comprise the respiratory systemDescribe how the respiratory mechanism processes oxygen and also CO2Compare and also contrast the features of top respiratory tract v the lower respiratory tract

Respiration – the exchange of oxygen and also carbon dioxide between the atmosphere and also the body cells.

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Events the Respiration:

Pulmonary ventilation- motion of air into and also out of the lungsExternal respiration- exchange that gases between the air and the blood in the lungs….oxygen diffuses right into the blood, carbon dioxide diffuses right into the lungs.Transport- motion of gases from the lung to the body cells and back, completed by the cardiovascular system.internal respiration- exchange the gases between the blood and body cells…. Oxygen diffuses into the cells and carbon dioxide moves right into the blood.


Organs of the Respiratory device (pathway that air)

Upper: Lower:

Nose (nasal cavity) 1. Lower part of the tracheaPharynx 2. Bronchial treeLarynx 3. LungsUpper component of trachea

The significant organs that the respiratory system role primarily to provide oxygen to body tissues for cellular respiration, eliminate the waste product carbon dioxide, and help to preserve acid-base balance. Parts of the respiratory device are likewise used for non-vital functions, such as sensing odors, speech production, and for straining, such as throughout childbirth or coughing.

Figure 1. The major respiratory structures expectations the nasal cavity to the diaphragm.

Functionally, the respiratory tract system deserve to be separated into a conducting zone and also a respiratory tract zone. The conducting zone that the respiratory tract system consists of the organs and structures not directly involved in gas exchange. The gas exchange wake up in the respiratory zone.

Conducting Zone

The major functions that the conducting zone space to carry out a route for incoming and also outgoing air, eliminate debris and also pathogens from the incoming air, and warm and humidify the just arrive air. Numerous structures within the conducting zone do other functions as well. The epithelium the the nasal passages, because that example, is vital to sensing odors, and the bronchial epithelium the lines the lungs can metabolize some airborne carcinogens.

The Nose and its nearby Structures

The major entrance and exit for the respiratory system is v the nose. When mentioning the nose, it is valuable to division it into two significant sections: the exterior nose, and the nasal cavity or internal nose.

The outside nose is composed of the surface and also skeletal frameworks that result in the outside appearance of the nose and also contribute come its numerous functions. The root is the region of the sleep located between the eyebrows. The bridge is the part of the sleep that connects the root to the remainder of the nose. The dorsum nasi is the size of the nose. The apex is the tip of the nose. ~ above either next of the apex, the nose are formed by the alae (singular = ala). An ala is a cartilaginous framework that develops the lateral side of each naris (plural = nares), or nose opening. The philtrum is the concave surface that associate the apex that the nose to the upper lip.

Figure 2. This illustration shows functions of the outside nose (top) and skeletal attributes of the nose (bottom).

Underneath the thin skin that the nose space its bones features. While the root and bridge that the sleep consist of bone, the protruding section of the sleep is created of cartilage. Together a result, when looking at a skull, the nose is missing. The sleep bone is just one of a pair that bones the lies under the root and also bridge the the nose. The nasal bone articulates superiorly with the frontal bone and also laterally through the maxillary bones. Septal cartilage is functional hyaline cartilage connected to the sleep bone, forming the dorsum nasi. The alar cartilage is composed of the apex of the nose; it surrounding the naris.

Figure 3. Upper Airway

The nares open right into the nasal cavity, i beg your pardon is separated right into left and also right part by the nasal septum. The nasal septum is created anteriorly through a part of the septal cartilage (the flexible portion you have the right to touch with your fingers) and posteriorly by the perpendicular bowl of the ethmoid bone (a cranial bone located simply posterior to the nasal bones) and the slim vomer skeleton (whose name describes its plough shape). Every lateral wall of the sleep cavity has actually three bony projections, referred to as the superior, middle, and also inferior nasal conchae. The inferior conchae are separate bones, whereas the superior and middle conchae are parts of the ethmoid bone. Conchae offer to rise the surface area of the sleep cavity and to disrupt the flow of air as it beginning the nose, resulting in air come bounce along the epithelium, where it is cleaned and also warmed. The conchae and meatuses additionally conserve water and also prevent dehydration that the sleep epithelium by trapping water during exhalation. The floor the the sleep cavity is composed of the palate. The tough palate at the anterior region of the sleep cavity is written of bone. The soft palate at the posterior section of the sleep cavity is composed of muscle tissue. Air exit the nasal cavities via the inner nares and moves into the pharynx.

Several bones the help form the wall surfaces of the sleep cavity have air-containing spaces called the paranasal sinuses, which offer to warm and also humidify just arrived air. Sinuses space lined through a mucosa. Every paranasal sinus is named for its connected bone: frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus. The sinuses create mucus and lighten the weight of the skull.

The nares and also anterior portion of the nasal cavities are lined with mucous membranes, containing sebaceous glands and also hair follicles that serve to avoid the passage of huge debris, such as dirt, through the nasal cavity. An olfactory epithelium provided to finding odors is found deeper in the sleep cavity.

The conchae, meatuses, and also paranasal sinuses are lined by respiratory tract epithelium written of pseudostratified ciliated columnar epithelium. The epithelium has goblet cells, one of the specialized, columnar epithelial cells that develop mucus to trap debris. The cilia of the respiratory tract epithelium help remove the mucus and debris indigenous the sleep cavity with a consistent beating motion, sweeping products towards the neck to be swallowed. Interestingly, cold air slows the activity of the cilia, result in build-up of mucus that may in turn lead come a runny nose throughout cold weather. This moist epithelium functions to warm and also humidify just arrived air. Capillaries located just beneath the sleep epithelium warmth the wait by convection. Serous and also mucus-producing cells likewise secrete the lysozyme enzyme and proteins dubbed defensins, which have antibacterial properties. Immune cells that patrol the connective organization deep come the respiratory epithelium provide added protection.


Pharynx (Throat) – muscular passage from nasal cavity come larynx

Three areas of the pharynx

Nasopharynx – superior region behind sleep cavityOropharynx – middle region behind mouthLaryngopharynx – inferior an ar that connects come larynx


Auditory pipe (Eustacian tube) – open right into the nasopharynxTonsils that the pharynxPharyngeal tonsils (adenoids) – in the nasopharynxPalatine tonsils – every side of the the oropharynxLingual tonsils – at the base of the tongue

The pharynx is a tube developed by bones muscle and lined through mucous membrane the is consistent with the of the nasal cavities. The pharynx is divided into three major regions: the nasopharynx, the oropharynx, and also the laryngopharynx.

Figure 5. The pharynx is separated into three regions: the nasopharynx, the oropharynx, and also the laryngopharynx.

The nasopharynx is flanked through the conchae of the sleep cavity, and it serves only as an airway. At the optimal of the nasopharynx space the pharyngeal tonsils. A pharyngeal tonsil, also called an adenoid, is an accumulation of lymphoid reticular tissue comparable to a lymph node the lies at the superior section of the nasopharynx. The duty of the pharyngeal tonsil is no well understood, but it includes a affluent supply of lymphocytes and also is covered with ciliated epithelium the traps and also destroys invading pathogens the enter throughout inhalation. The pharyngeal tonsils are large in children, however interestingly, often tend to regress v age and may even disappear. The uvula is a small bulbous, teardrop-shaped structure located at the apex of the soft palate. Both the uvula and soft palate relocate like a pendulum throughout swallowing, swinging upward to close off the nasopharynx to avoid ingested materials from beginning the nasal cavity. In addition, auditory (Eustachian) tube that connect to each center ear cavity open into the nasopharynx. This connection is why colds often lead come ear infections.

The oropharynx is a passageway because that both air and also food. The oropharynx is bordered superiorly through the nasopharynx and anteriorly by the dental cavity. The fauces is the opening at the connection between the dental cavity and also the oropharynx. As the nasopharynx becomes the oropharynx, the epithelium changes from pseudostratified ciliated columnar epithelium to stratified squamous epithelium. The oropharynx includes two unique sets that tonsils, the palatine and also lingual tonsils. A palatine tonsil is one of a pair that structures located laterally in the oropharynx in the area of the fauces. The lingual tonsil is located at the basic of the tongue. Similar to the pharyngeal tonsil, the palatine and also lingual tonsils are composed of lymphoid tissue, and trap and also destroy pathogens start the body with the dental or nasal cavities.

The laryngopharynx is worse to the oropharynx and also posterior come the larynx. It proceeds the course for ingested material and air till its worse end, wherein the digestive and also respiratory solution diverge. The stratified squamous epithelium the the oropharynx is constant with the laryngopharynx. Anteriorly, the laryngopharynx opens into the larynx, whereas posteriorly, that enters the esophagus.


Larynx (Voice Box) – cartilaginous framework that paths air and food into suitable channels; functions in speech

Thyroid cartilage – biggest of the hyaline cartilages, protrudes anteriorly and is commonly called the Adam’s appleCricoid cartilage – develops the attachment to tracheaEpiglottis – flap the elastic cartilage the guards the entrance right into the larynx; when we are breathing the flap is open, as soon as we swallow, the larynx is traction upward and the epiglottis closesVocal cords (vocal folds) – folds within the larynx that vibrate through expelled airGlottis – slit-like opening in between the vocal folds that leads come the trachea


The larynx is a cartilaginous structure inferior to the laryngopharynx the connects the pharynx come the trachea and helps manage the volume that air that enters and leaves the lungs. The structure of the larynx is formed by several pieces the cartilage. Three big cartilage pieces—the thyroid cartilage (anterior), epiglottis (superior), and cricoid cartilage (inferior)—form the significant structure that the larynx. The thyroid cartilage is the largest piece the cartilage that makes up the larynx. The thyroid cartilage consists of the laryngeal prominence, or “Adam’s apple,” which often tends to be more prominent in males. The thick cricoid cartilage forms a ring, with a wide posterior region and a diluent anterior region. Three smaller, paired cartilages—the arytenoids, corniculates, and cuneiforms—attach to the epiglottis and the vocal cords and muscle that assist move the vocal cords to develop speech.

Figure 6. The larynx extends native the laryngopharynx and also the hyoid bone come the trachea.

Figure 7. The true vocal cords and vestibular folds of the larynx are viewed inferiorly indigenous the laryngopharynx.

The epiglottis, attached come the thyroid cartilage, is a really flexible item of elastic cartilage that covers the opening of the trachea. Once in the “closed” position, the unattached end of the epiglottis rests ~ above the glottis. The glottis is written of the vestibular folds, the true vocal cords, and also the room between these folds. A vestibular fold, or false vocal cord, is one of a pair of folded sections of mucous membrane. A true vocal cord is among the white, membranous crease attached by muscle to the thyroid and also arytenoid cartilages of the larynx ~ above their outer edges. The inner edge of the true vocal cords space free, enabling oscillation to produce sound. The dimension of the membranous wrinkle of the true vocal cords differs in between individuals, creating voices with different pitch ranges. Wrinkle in males often tend to be larger than those in females, which produce a depths voice. The act of swallowing causes the pharynx and also larynx to lift upward, enabling the pharynx come expand and the epiglottis the the larynx to swing downward, closing the opened to the trachea. These movements produce a larger area because that food to pass through, while avoiding food and beverages from entering the trachea.

Continuous v the laryngopharynx, the superior portion of the larynx is lined v stratified squamous epithelium, transitioning into pseudostratified ciliated columnar epithelium that contains goblet cells. Comparable to the sleep cavity and also nasopharynx, this dedicated epithelium produces rubber to catch debris and also pathogens together they get in the trachea. The cilia to win the mucus upward towards the laryngopharynx, wherein it have the right to be swallowed under the esophagus.


The trachea (windpipe) extends indigenous the larynx toward the lungs. The trachea is developed by 16 to 20 stacked, C-shaped pieces of hyaline cartilage the are associated by dense connective tissue. The trachealis muscle and also elastic connective tissue together type the fibroelastic membrane, a functional membrane the closes the posterior surface ar of the trachea, connecting the C-shaped cartilages. The fibroelastic membrane allows the trachea come stretch and also expand slightly throughout inhalation and also exhalation, conversely, the ring of cartilage administer structural support and also prevent the trachea indigenous collapsing. In addition, the trachealis muscle deserve to be contracted to pressure air through the trachea during exhalation. The trachea is lined v pseudostratified ciliated columnar epithelium, which is constant with the larynx. The esophagus borders the trachea posteriorly.

Bronchial Tree

Primary bronchi – right and also left branches the the trachea that go into the lungsSecondary bronchi – branches the the main that get in each lobe of the lungsTertiary bronchi – more branches that the secondary bronchiBronchioles – smallest branches in ~ the lungsAlveolar ducts – microscopic branches that the bronchiolesAlveoli – terminal air sacs where gas exchange takes place (anatomy resembles a bunch of grapes)Surfactant – mixture the lipoproteins the reduces the attraction in between water molecules in the alveoli; it avoids collapse that the alveoli

The trachea branches into the right and also left major bronchi at the carina. These bronchi are likewise lined through pseudostratified ciliated columnar epithelium comprise mucus-producing goblet cells. The carina is a elevated structure that contains specialized nervous organization that cause violent coughing if a international body, such as food, is present. Rings of cartilage, comparable to those the the trachea, support the framework of the bronchi and prevent their collapse. The main bronchi get in the lung at the hilum, a concave region where blood vessels, lymphatic vessels, and nerves also enter the lungs. The bronchi continue to branch right into bronchial a tree. A bronchial tree (or respiratory tree) is the collective term used for these multiple-branched bronchi. The main duty of the bronchi, like other conducting ar structures, is to provide a passageway because that air to move into and also out of each lung. In addition, the mucous membrane traps debris and also pathogens.

A bronchiole branches native the tertiary bronchi. Bronchioles, i m sorry are around 1 mm in diameter, additional branch until they become the small terminal bronchioles, which bring about the structures of gas exchange. Over there are an ext than 1000 terminal bronchioles in each lung. The muscular wall surfaces of the bronchioles execute not save on computer cartilage like those that the bronchi. This muscular wall can adjust the dimension of the tube to increase or decrease airflow with the tube.


Each lung is divided into lobes through fissures – deep groovesLeft lung – 2 lobesRight lung – 3 lobes


Coverings that the lungs (Pleura – serous membranes)Visceral pleura – within layer the covers the surface ar of each lungParietal pleura – outer layer that lines the thoracic cavity and also mediastinumo Pleural fluid – serous fluid between the 2 layers the reduces friction

Respiratory Zone

In comparison to the conducting zone, the respiratory tract zone contains structures that room directly affiliated in gas exchange. The respiratory tract zone starts where the terminal bronchioles join a respiratory tract bronchiole, the smallest kind of bronchiole, which climate leads come an alveolar duct, opening right into a swarm of alveoli.

Figure 9. Bronchioles cause alveolar sacs in the respiratory tract zone, where gas exchange occurs.


An alveolar duct is a tube written of smooth muscle and also connective tissue, i m sorry opens right into a swarm of alveoli. One alveolus is one of the numerous small, grape-like bag that are attached come the alveolar ducts.

An alveolar sac is a cluster of countless individual alveoli that are responsible because that gas exchange. One alveolus is around 200 mm in diameter with elastic walls that allow the alveolus come stretch throughout air intake, which substantially increases the surface ar area accessible for gas exchange. Alveoli are connected to their next-door neighbors by alveolar pores, which assist maintain same air press throughout the alveoli and lung.

The alveolar wall surface consists of three significant cell types: form I alveolar cells, type II alveolar cells, and also alveolar macrophages. A form I alveolar cabinet is a squamous epithelial cell of the alveoli, i m sorry constitute up to 97 percent the the alveolar surface area. This cells are around 25 nm thick and are very permeable come gases. A form II alveolar cell is interspersed amongst the form I cells and secretes pulmonary surfactant, a substance composed of phospholipids and also proteins the reduces the surface anxiety of the alveoli. Roaming about the alveolar wall surface is the alveolar macrophage, a phagocytic cell of the immune mechanism that gets rid of debris and also pathogens that have reached the alveoli.

The simple squamous epithelium created by type I alveolar cells is attached come a thin, elastic basement membrane. This epithelium is exceptionally thin and borders the endothelial membrane that capillaries. Take away together, the alveoli and capillary membranes form a respiratory membrane that is approximately 0.5 mm thick. The respiratory tract membrane enables gases to cross by an easy diffusion, enabling oxygen come be picked up by the blood for transport and also CO2 to be released right into the waiting of the alveoli.



 BREATHING – PULMONARY VENTILATION – process that exchanges air between the atmosphere and also the alveoli of the lungs

Two phasesInspiration – circulation of air into the lungsExpiration – air leaving the lungsThere space 3 pressures vital in breathing:Atmospheric pressure – pressure of air exterior the body; at sea level is 760mmHg, decreases with greater elevationsIntra-alveolar (intrapulmonary) pressure – air pressure within the lungs; fluctuates between being reduced and greater than atmospheric push as we breathIntrapleural push – push within the pleural cavity (outside lungs within thoracic cavity); around 756mmHg…slightly lower than atmospheric pressure; must always be lower that atmospheric press to keep lungs inflated. If the intrapleural pressure were to same atmospheric pressure, the lungs would certainly collapse and be nonfunctional


**Rule that thumb** – Volume alters lead to pressure changes, which leader to the flow of gases to equalize the pressure.


Inspiration – active procedure (requires energy)Diaphragm and also external intercostals muscle contractThe size of the thoracic cavity increasesThe boost in volume of the lung lowers intra-alveolar pressureExternal wait is pulled into the lungs – greater atmospheric press pushes air right into the reduced pressured lungs (intra-alveolar pressure)


Expiration – passive procedure (no energy since muscles room relaxing)Diaphragm and intercostals muscle relaxThe dimension of the thoracic cavity decreasesThe decrease in volume that the lung raises intra-alveolar pressureAir is forced out – greater intra-alveolar pressure pressures air out to the lower atmospheric pressure


Expiration can come to be an active process if the respiratory tract passageways space narrowed by spasms as in asthma or clogged with mucus together in bronchitis or pneumonia. If this occurs, expiration is recognized as required expiration and involves activating the inner intercostals muscle and ab muscles to pressure air indigenous the lungs.Pneumothorax – presence of air in the pleural cavity that outcomes in lung collapse; the lung is nonfunctional; treatment entails removing the intrapleural waiting to regain normal pressure


Respiratory Volumes and Capacities

Tidal volume (TV) – lot of air relocating in and out of the lungs through each breath (about 500ml top top average…age, size, sex, and also physical problem can reason variation)Inspiratory make reservation volume (IRV) – lot of wait that have the right to be take away in forcibly end the tidal volumeExpiratory make reservation volume (ERV) – amount of air that have the right to be forcibly exhaled end tidal volumeResidual volume – quantity of wait that always remains in the lungs; it can not be exhaled; Residual volume is important because it permits gas exchange to occur between breaths and helps save the alveoli inflatedVital volume – maximum amount of air that have the right to be forcefully exchanged; VC = TV+IRV+ERVTotal lung capacity = VC+RV

Control the Respiration

Respiration is controlled by the respiratory center in the brain stem in solution to CO2 levelsMedulla oblongata – sets simple rhythm of breath (pacemaker)Pons – smooths the end respiratory rate and also influences depth and length of inspiration


Factors influencing BreathingChemical – carbon dioxide, hydrogen ions and oxygen levels space the most important components that control respirationChemoreceptors – sensory receptors that detect CO2, H+, and O2 level in the blood; situated in the respiratory tract center, the carotid arteries and also aorta…CO2 levels space the main influence, oxygen levels only affect breathing when dangerously lowIf CO2 level increase, the respiratory facility (medulla and pons) is engendered to boost the rate and also depth that breathing. This boosts the price of CO2 removal and returns concentrations to normal resting levels.Inflation reflex – stretch receptor in the visceral pleurae room sensitive to the degree of stretching by the lungs. This is to prevent excessively deep inspirations the may damages the lungsHigher mind Centers – the cerebrum enables voluntary transforming of breathing, however these capabilities space limited. One can select to organize their breath because that a period of time, however eventually the respiratory center will take over together the CO2 levels increase.Body Temperature – boost in human body temp such as during exercise or fever increases respiration


Gas Exchange

Alveolar air has a greater concentration of oxygen therefore it easily diffuses into the bordering capillariesThe capillaries have a greater concentration that carbon dioxide for this reason it easily diffuses into the alveoli.

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Transport of respiratory tract Gases

Oxygen diffusing right into the capillaries combines through hemoglobin to type oxyhemoglobin. Upon reaching body cells, oxygen is released (some constantly stays attached come hemoglobin)Carbon dioxide travels in the blood v 3 pathways:7% in plasma23% in hemoglobin (carbon dioxide binds at a various site ~ above hemoglobin so the doesn’t impact oxygen transport)70% as carbonic acid in RBCs and also this quickly breaks down right into bicarbonate ions.