Skeletal System Artlabeling Activity Figure 74a 2 of 2 5 of 49 Part a

22.1 Organs and Structures of the Respiratory System

Learning Objectives

By the cease of this section, you will exist able to:

List the structures that brand up the respiratory arrangement
Describe how the respiratory organisation processes oxygen and CO₂
Compare and contrast the functions of upper respiratory tract with the lower respiratory tract

The major organs of the respiratory organisation part primarily to provide oxygen to body tissues for cellular respiration, remove the waste production carbon dioxide, and aid to maintain acid-base of operations residuum. Portions of the respiratory system are as well used for non-vital functions, such every bit sensing odors, speech communication production, and for straining, such every bit during childbirth or cough (Effigy 22.i.one).

This figure shows the upper half of the human body. The major organs in the respiratory system are labeled. — **Figure 22.1.1 – Major Respiratory Structures:** The major respiratory structures span the nasal cavity to the diaphragm.

Functionally, the respiratory organisation tin can exist divided into a conducting zone and a respiratory zone. The conducting zone of the respiratory system includes the organs and structures not straight involved in gas substitution. The gas exchange occurs in the respiratory zone.

Conducting Zone

The major functions of the conducting zone are to provide a route for incoming and outgoing air, remove debris and pathogens from the incoming air, and warm and humidify the incoming air. Several structures within the conducting zone perform other functions also. The epithelium of the nasal passages, for example, is essential to sensing odors, and the bronchial epithelium that lines the lungs can metabolize some airborne carcinogens.

The Olfactory organ and its Next Structures

The major entrance and get out for the respiratory arrangement is through the nose. When discussing the olfactory organ, it is helpful to separate it into ii major sections: the external nose, and the nasal cavity or internal nose.

The external nose consists of the surface and skeletal structures that result in the outward appearance of the nose and contribute to its numerous functions (Effigy 22.1.2). The root is the region of the olfactory organ located between the eyebrows. The bridge is the part of the olfactory organ that connects the root to the rest of the nose. The dorsum nasi is the length of the olfactory organ. The apex is the tip of the nose. On either side of the apex, the nostrils are formed by the alae (singular = ala). An ala is a cartilaginous structure that forms the lateral side of each naris (plural = nares), or nostril opening. The philtrum is the concave surface that connects the apex of the nose to the upper lip.

This figure shows the human nose. The top left panel shows the front view, and the top right panel shows the side view. The bottom panel shows the cartilaginous components of the nose. — **Figure 22.1.ii – Nose:** This illustration shows features of the external nose (top) and skeletal features of the nose (lesser).

Underneath the sparse skin of the nose are its skeletal features (meet Figure 22.1.2, lower illustration). While the root and bridge of the olfactory organ consist of bone, the protruding portion of the olfactory organ is composed of cartilage. Equally a result, when looking at a skull, the nose is missing. The nasal bone is i of a pair of bones that lies nether the root and bridge of the nose. The nasal bone articulates superiorly with the frontal bone and laterally with the maxillary bones. Septal cartilage is flexible hyaline cartilage connected to the nasal bone, forming the back nasi. The alar cartilage consists of the apex of the nose; information technology surrounds the naris.

The nares open into the nasal cavity, which is separated into left and right sections past the nasal septum (Figure 22.one.three). The nasal septum is formed anteriorly by a portion of the septal cartilage (the flexible portion you can touch with your fingers) and posteriorly past the perpendicular plate of the ethmoid bone (a cranial bone located but posterior to the nasal basic) and the thin vomer basic (whose proper name refers to its plough shape). Each lateral wall of the nasal cavity has three bony projections, chosen the superior, heart, and inferior nasal conchae. The inferior conchae are carve up bones, whereas the superior and heart conchae are portions of the ethmoid os. Conchae serve to increment the surface expanse of the nasal cavity and to disrupt the menstruation of air as it enters the nose, causing air to bounciness along the epithelium, where it is cleaned and warmed. The conchae and meatuses also conserve water and prevent dehydration of the nasal epithelium by trapping water during exhalation. The flooring of the nasal crenel is composed of the palate. The difficult palate at the inductive region of the nasal cavity is composed of bone. The soft palate at the posterior portion of the nasal cavity consists of muscle tissue. Air exits the nasal cavities via the internal nares and moves into the pharynx.

This figure shows a cross section view of the nose and throat. The major parts are labeled. — **Figure 22.1.3** Upper Airway

Several bones that assist form the walls of the nasal cavity have air-containing spaces called the paranasal sinuses, which serve to warm and humidify incoming air. Sinuses are lined with a mucosa. Each paranasal sinus is named for its associated bone: frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus. The sinuses produce fungus and lighten the weight of the skull.

The nares and inductive portion of the nasal cavities are lined with mucous membranes, containing sebaceous glands and hair follicles that serve to forestall the passage of large debris, such as dirt, through the nasal cavity. An olfactory epithelium used to find odors is found deeper in the nasal cavity.

The conchae, meatuses, and paranasal sinuses are lined past respiratory epithelium composed of pseudostratified ciliated columnar epithelium (Effigy 22.i.4). The epithelium contains goblet cells, i of the specialized, columnar epithelial cells that produce mucus to trap droppings. The cilia of the respiratory epithelium help remove the mucus and debris from the nasal cavity with a constant beating move, sweeping materials towards the pharynx to be swallowed. Interestingly, cold air slows the movement of the cilia, resulting in accumulation of mucus that may in turn atomic number 82 to a runny nose during common cold weather. This moist epithelium functions to warm and humidify incoming air. Capillaries located just beneath the nasal epithelium warm the air past convection. Serous and mucus-producing cells also secrete the lysozyme enzyme and proteins chosen defensins, which have antibacterial properties. Allowed cells that patrol the connective tissue deep to the respiratory epithelium provide boosted protection.

This figure shows a micrograph of pseudostratified epithelium. — **Figure 22.1.4 – Pseudostratified Ciliated Columnar Epithelium:** Respiratory epithelium is pseudostratified ciliated columnar epithelium. Seromucous glands provide lubricating fungus. LM × 680. (Micrograph provided past the Regents of University of Michigan Medical Schoolhouse © 2012)

Pharynx

The pharynx is a tube formed by skeletal muscle and lined by mucous membrane that is continuous with that of the nasal cavities (see Figure 22.one.three). The pharynx is divided into three major regions: the nasopharynx, the oropharynx, and the laryngopharynx (Figure 22.1.v).

The nasopharynx is flanked past the conchae of the nasal cavity, and it serves only as an airway. At the top of the nasopharynx are the pharyngeal tonsils. A pharyngeal tonsil, also called an adenoid, is an aggregate of lymphoid reticular tissue similar to a lymph node that lies at the superior portion of the nasopharynx. The function of the pharyngeal tonsil is non well understood, but it contains a rich supply of lymphocytes and is covered with ciliated epithelium that traps and destroys invading pathogens that enter during inhalation. The pharyngeal tonsils are large in children, simply interestingly, tend to regress with historic period and may even disappear. The uvula is a modest bulbous, teardrop-shaped construction located at the noon of the soft palate. Both the uvula and soft palate motility like a pendulum during swallowing, swinging upwardly to close off the nasopharynx to forbid ingested materials from entering the nasal cavity. In addition, auditory (Eustachian) tubes that connect to each middle ear cavity open into the nasopharynx. This connection is why colds often atomic number 82 to ear infections.

The oropharynx is a passageway for both air and nutrient. The oropharynx is bordered superiorly past the nasopharynx and anteriorly past the oral crenel. The fauces is the opening at the connection between the mouth and the oropharynx. Equally the nasopharynx becomes the oropharynx, the epithelium changes from pseudostratified ciliated columnar epithelium to stratified squamous epithelium. The oropharynx contains two distinct sets of tonsils, the palatine and lingual tonsils. A palatine tonsil is i of a pair of structures located laterally in the oropharynx in the area of the fauces. The lingual tonsil is located at the base of the tongue. Similar to the pharyngeal tonsil, the palatine and lingual tonsils are composed of lymphoid tissue, and trap and destroy pathogens entering the body through the oral or nasal cavities.

The laryngopharynx is inferior to the oropharynx and posterior to the larynx. It continues the route for ingested material and air until its inferior terminate, where the digestive and respiratory systems diverge. The stratified squamous epithelium of the oropharynx is continuous with the laryngopharynx. Anteriorly, the laryngopharynx opens into the larynx, whereas posteriorly, it enters the esophagus.

Larynx

The larynx is a cartilaginous structure inferior to the laryngopharynx that connects the pharynx to the trachea and helps regulate the volume of air that enters and leaves the lungs (Figure 22.1.6). The structure of the larynx is formed by several pieces of cartilage. 3 big cartilage pieces—the thyroid cartilage (anterior), epiglottis (superior), and cricoid cartilage (inferior)—form the major structure of the larynx. The thyroid cartilage is the largest piece of cartilage that makes up the larynx. The thyroid cartilage consists of the laryngeal prominence, or "Adam'southward apple tree," which tends to exist more than prominent in males. The thick cricoid cartilage forms a ring, with a wide posterior region and a thinner inductive region. Iii smaller, paired cartilages—the arytenoids, corniculates, and cuneiforms—attach to the epiglottis and the vocal cords and muscle that help move the vocal cords to produce spoken communication.

The epiglottis, attached to the thyroid cartilage, is a very flexible slice of rubberband cartilage that covers the opening of the trachea (see Effigy 22.1.three). When in the "closed" position, the unattached end of the epiglottis rests on the glottis. The glottis is composed of the vestibular folds, the truthful vocal cords, and the infinite between these folds (Figure 22.one.7). A vestibular fold, or false vocal string, is one of a pair of folded sections of mucous membrane. A true vocal string is one of the white, membranous folds attached by musculus to the thyroid and arytenoid cartilages of the larynx on their outer edges. The inner edges of the true vocal cords are free, allowing oscillation to produce sound. The size of the membranous folds of the true vocal cords differs between individuals, producing voices with different pitch ranges. Folds in males tend to exist larger than those in females, which create a deeper voice. The act of swallowing causes the pharynx and larynx to elevator upward, allowing the pharynx to aggrandize and the epiglottis of the larynx to swing downward, closing the opening to the trachea. These movements produce a larger surface area for nutrient to laissez passer through, while preventing nutrient and beverages from entering the trachea.

This diagram shows the cross section of the larynx. The different types of cartilages are labeled. — **Figure 22.i.7 – Vocal Cords:** The true vocal cords and vestibular folds of the larynx are viewed inferiorly from the laryngopharynx.

Continuous with the laryngopharynx, the superior portion of the larynx is lined with stratified squamous epithelium, transitioning into pseudostratified ciliated columnar epithelium that contains goblet cells. Like to the nasal cavity and nasopharynx, this specialized epithelium produces fungus to trap debris and pathogens as they enter the trachea. The cilia crush the fungus upward towards the laryngopharynx, where it can be swallowed down the esophagus.

Trachea

The trachea (windpipe) extends from the larynx toward the lungs (Figure 22.i.8a). The trachea is formed by 16 to 20 stacked, C-shaped pieces of hyaline cartilage that are continued by dumbo connective tissue. The trachealis muscle and elastic connective tissue together class the fibroelastic membrane, a flexible membrane that closes the posterior surface of the trachea, connecting the C-shaped cartilages. The fibroelastic membrane allows the trachea to stretch and expand slightly during inhalation and exhalation, whereas the rings of cartilage provide structural support and preclude the trachea from collapsing. In improver, the trachealis muscle can exist contracted to force air through the trachea during exhalation. The trachea is lined with pseudostratified ciliated columnar epithelium, which is continuous with the larynx. The esophagus borders the trachea posteriorly.

Bronchial Tree

The trachea branches into the correct and left primary bronchi at the carina. These bronchi are besides lined by pseudostratified ciliated columnar epithelium containing mucus-producing goblet cells (Figure 22.one.8b). The carina is a raised structure that contains specialized nervous tissue that induces violent coughing if a foreign body, such as food, is present. Rings of cartilage, similar to those of the trachea, support the structure of the bronchi and prevent their collapse. The primary bronchi enter the lungs at the hilum, a concave region where claret vessels, lymphatic vessels, and nerves also enter the lungs. The bronchi continue to branch into bronchial a tree. A bronchial tree (or respiratory tree) is the commonage term used for these multiple-branched bronchi. The main function of the bronchi, like other conducting zone structures, is to provide a passageway for air to move into and out of each lung. In addition, the mucous membrane traps debris and pathogens.

A bronchiole branches from the tertiary bronchi. Bronchioles, which are about 1 mm in diameter, farther branch until they get the tiny final bronchioles, which pb to the structures of gas exchange. At that place are more than than 1000 last bronchioles in each lung. The muscular walls of the bronchioles do not incorporate cartilage like those of the bronchi. This muscular wall can change the size of the tubing to increase or decrease airflow through the tube.

Respiratory Zone

In dissimilarity to the conducting zone, the respiratory zone includes structures that are directly involved in gas exchange. The respiratory zone begins where the terminal bronchioles bring together a respiratory bronchiole, the smallest type of bronchiole (Effigy 22.i.nine), which then leads to an alveolar duct, opening into a cluster of alveoli.

This image shows the bronchioles and alveolar sacs in the lungs and depicts the exchange of oxygenated and deoxygenated blood in the pulmonary blood vessels. — **Figure 22.1.9 – Respiratory Zone:** Bronchioles pb to alveolar sacs in the respiratory zone, where gas exchange occurs.

Alveoli

An alveolar duct is a tube equanimous of smooth muscle and connective tissue, which opens into a cluster of alveoli. An alveolus is one of the many small, grape-like sacs that are attached to the alveolar ducts.

An alveolar sac is a cluster of many individual alveoli that are responsible for gas exchange. An alveolus is approximately 200 μm in bore with rubberband walls that let the air sac to stretch during air intake, which greatly increases the surface area available for gas substitution. Alveoli are connected to their neighbors past alveolar pores, which help maintain equal air pressure throughout the alveoli and lung (Figure 22.1.x).

This figure shows the detailed structure of the alveolus. The top panel shows the alveolar sacs and the bronchioles. The middle panel shows a magnified view of the alveolus, and the bottom panel shows a micrograph of the cross section of a bronchiole. — **Effigy 22.i.x – Structures of the Respiratory Zone:** (a) The air sac is responsible for gas exchange. (b) A micrograph shows the alveolar structures within lung tissue. LM × 178. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

The alveolar wall consists of three major jail cell types: type I alveolar cells, type Ii alveolar cells, and alveolar macrophages. A type I alveolar cell is a squamous epithelial cell of the alveoli, which constitute upwards to 97 percent of the alveolar surface surface area. These cells are about 25 nm thick and are highly permeable to gases. A type II alveolar cell is interspersed among the type I cells and secretes pulmonary surfactant, a substance composed of phospholipids and proteins that reduces the surface tension of the alveoli. Roaming effectually the alveolar wall is the alveolar macrophage, a phagocytic cell of the immune organization that removes droppings and pathogens that have reached the alveoli.

The elementary squamous epithelium formed by type I alveolar cells is fastened to a thin, rubberband basement membrane. This epithelium is extremely thin and borders the endothelial membrane of capillaries. Taken together, the alveoli and capillary membranes form a respiratory membrane that is approximately 0.5 mm thick. The respiratory membrane allows gases to cross by simple diffusion, allowing oxygen to be picked upward past the blood for send and CO₂to be released into the air of the alveoli.

Diseases of the…Respiratory System: Asthma

Asthma is common status that affects the lungs in both adults and children. Approximately viii.2 percent of adults (18.vii million) and 9.4 per centum of children (7 million) in the Us suffer from asthma. In add-on, asthma is the almost frequent cause of hospitalization in children.

Asthma is a chronic illness characterized by inflammation and edema of the airway, and bronchospasms (that is, constriction of the bronchioles), which can inhibit air from entering the lungs. In addition, excessive mucus secretion tin can occur, which further contributes to airway apoplexy (Figure 22.one.11). Cells of the immune system, such as eosinophils and mononuclear cells, may as well be involved in infiltrating the walls of the bronchi and bronchioles.

Bronchospasms occur periodically and lead to an "asthma assault." An assail may be triggered by environmental factors such as dust, pollen, pet hair, or dander, changes in the weather, mold, tobacco smoke, and respiratory infections, or past practise and stress.

The top panel of this figure shows normal lung tissue, and the bottom panel shows lung tissue inflamed by asthma. — **Effigy 22.1.11 – Normal and Bronchial Asthma Tissues:** (a) Normal lung tissue does not have the characteristics of lung tissue during (b) an asthma attack, which include thickened mucosa, increased mucus-producing goblet cells, and eosinophil infiltrates.

Symptoms of an asthma assault involve coughing, shortness of breath, wheezing, and tightness of the chest. Symptoms of a severe asthma attack that requires immediate medical attention would include difficulty breathing that results in blue (cyanotic) lips or face, defoliation, drowsiness, a rapid pulse, sweating, and severe anxiety. The severity of the condition, frequency of attacks, and identified triggers influence the type of medication that an private may require. Longer-term treatments are used for those with more severe asthma. Brusk-term, fast-acting drugs that are used to care for an asthma assault are typically administered via an inhaler. For young children or individuals who accept difficulty using an inhaler, asthma medications can be administered via a nebulizer.

In many cases, the underlying cause of the condition is unknown. Nevertheless, contempo inquiry has demonstrated that certain viruses, such as human being rhinovirus C (HRVC), and the bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae that are contracted in infancy or early babyhood, may contribute to the evolution of many cases of asthma.

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Chapter Review

The respiratory organisation is responsible for obtaining oxygen and getting rid of carbon dioxide, and aiding in speech production and in sensing odors. From a functional perspective, the respiratory system can be divided into two major areas: the conducting zone and the respiratory zone. The conducting zone consists of all of the structures that provide passageways for air to travel into and out of the lungs: the nasal cavity, throat, trachea, bronchi, and most bronchioles. The nasal passages contain the conchae and meatuses that expand the surface area of the crenel, which helps to warm and humidify incoming air, while removing debris and pathogens. The pharynx is composed of three major sections: the nasopharynx, which is continuous with the nasal cavity; the oropharynx, which borders the nasopharynx and the oral cavity; and the laryngopharynx, which borders the oropharynx, trachea, and esophagus. The respiratory zone includes the structures of the lung that are direct involved in gas exchange: the terminal bronchioles and alveoli.

The lining of the conducting zone is composed mostly of pseudostratified ciliated columnar epithelium with goblet cells. The mucus traps pathogens and debris, whereas beating cilia motility the mucus superiorly toward the pharynx, where it is swallowed. As the bronchioles go smaller and smaller, and nearer the alveoli, the epithelium thins and is simple squamous epithelium in the alveoli. The endothelium of the surrounding capillaries, together with the alveolar epithelium, forms the respiratory membrane. This is a claret-air barrier through which gas exchange occurs by elementary improvidence.

Interactive Link Questions

Visit this site to larn more well-nigh what happens during an asthma attack. What are the three changes that occur inside the airways during an asthma assail?

Inflammation and the production of a thick fungus; constriction of the airway muscles, or bronchospasm; and an increased sensitivity to allergens.

Review Questions

Critical Thinking Questions

i. Depict the three regions of the throat and their functions.

ii. If a person sustains an injury to the epiglottis, what would be the physiological effect?

iii. Compare and dissimilarity the conducting and respiratory zones.

References

Bizzintino J, Lee WM, Laing IA, Vang F, Pappas T, Zhang 1000, Martin Air-conditioning, Khoo SK, Cox DW, Geelhoed GC, et al. Association betwixt human rhinovirus C and severity of acute asthma in children. Eur Respir J [Internet]. 2010 [cited 2013 Mar 22]; 37(5):1037–1042. Available from: http://erj.ersjournals.com/gca?submit=Go&gca=erj%3B37%2F5%2F1037&allch=

Kumar V, Ramzi S, Robbins SL. Robbins Basic Pathology. 7th ed. Philadelphia (PA): Elsevier Ltd; 2005.

Martin RJ, Kraft Thousand, Chu HW, Berns, EA, Cassell GH. A link betwixt chronic asthma and chronic infection. J Allergy Clin Immunol [Internet]. 2001 [cited 2013 Mar 22]; 107(4):595-601. Available from: http://erj.ersjournals.com/gca?submit=Go&gca=erj%3B37%2F5%2F1037&allch=

Glossary

ala: (plural = alae) small, flaring structure of a nostril that forms the lateral side of the nares

alar cartilage: cartilage that supports the apex of the nose and helps shape the nares; it is connected to the septal cartilage and connective tissue of the alae

alveolar duct: small tube that leads from the concluding bronchiole to the respiratory bronchiole and is the point of attachment for alveoli

alveolar macrophage: immune organization cell of the alveolus that removes debris and pathogens

alveolar pore: opening that allows airflow between neighboring alveoli

alveolar sac: cluster of alveoli

air sac: pocket-size, grape-similar sac that performs gas exchange in the lungs

apex: tip of the external nose

bronchial tree: collective name for the multiple branches of the bronchi and bronchioles of the respiratory system

bridge: portion of the external nose that lies in the area of the nasal bones

bronchiole: branch of bronchi that are one mm or less in diameter and terminate at alveolar sacs

bronchus: tube connected to the trachea that branches into many subsidiaries and provides a passageway for air to enter and leave the lungs

conducting zone: region of the respiratory system that includes the organs and structures that provide passageways for air and are non directly involved in gas exchange

cricoid cartilage: portion of the larynx composed of a ring of cartilage with a wide posterior region and a thinner anterior region; attached to the esophagus

dorsum nasi: intermediate portion of the external nose that connects the bridge to the noon and is supported by the nasal bone

epiglottis: leaf-shaped piece of elastic cartilage that is a portion of the larynx that swings to close the trachea during swallowing

external olfactory organ: region of the nose that is easily visible to others

fauces: portion of the posterior oral crenel that connects the oral fissure to the oropharynx

fibroelastic membrane: specialized membrane that connects the ends of the C-shape cartilage in the trachea; contains smooth muscle fibers

glottis: opening betwixt the vocal folds through which air passes when producing spoken language

laryngeal prominence: region where the two lamina of the thyroid cartilage bring together, forming a protrusion known as "Adam'south apple"

laryngopharynx: portion of the pharynx bordered by the oropharynx superiorly and esophagus and trachea inferiorly; serves as a route for both air and food

larynx: cartilaginous structure that produces the vox, prevents food and beverages from entering the trachea, and regulates the volume of air that enters and leaves the lungs

lingual tonsil: lymphoid tissue located at the base of the tongue

meatus: one of three recesses (superior, center, and junior) in the nasal crenel attached to the conchae that increase the surface area of the nasal cavity

naris: (plural = nares) opening of the nostrils

nasal os: os of the skull that lies under the root and bridge of the nose and is connected to the frontal and maxillary bones

nasal septum: wall composed of bone and cartilage that separates the left and right nasal cavities

nasopharynx: portion of the pharynx flanked by the conchae and oropharynx that serves equally an airway

oropharynx: portion of the pharynx flanked past the nasopharynx, oral crenel, and laryngopharynx that is a passageway for both air and food

palatine tonsil: 1 of the paired structures composed of lymphoid tissue located inductive to the uvula at the roof of isthmus of the fauces

paranasal sinus: one of the cavities within the skull that is connected to the conchae that serve to warm and humidify incoming air, produce fungus, and lighten the weight of the skull; consists of frontal, maxillary, sphenoidal, and ethmoidal sinuses

pharyngeal tonsil: construction equanimous of lymphoid tissue located in the nasopharynx

throat: region of the conducting zone that forms a tube of skeletal muscle lined with respiratory epithelium; located between the nasal conchae and the esophagus and trachea

philtrum: concave surface of the confront that connects the apex of the nose to the top lip

pulmonary surfactant: substance composed of phospholipids and proteins that reduces the surface tension of the alveoli; made past type II alveolar cells

respiratory bronchiole: specific type of bronchiole that leads to alveolar sacs

respiratory epithelium: ciliated lining of much of the conducting zone that is specialized to remove droppings and pathogens, and produce mucus

respiratory membrane: alveolar and capillary wall together, which form an air-blood barrier that facilitates the uncomplicated diffusion of gases

respiratory zone: includes structures of the respiratory organization that are straight involved in gas exchange

root: region of the external olfactory organ between the eyebrows

thyroid cartilage: largest piece of cartilage that makes upward the larynx and consists of two lamina

trachea: tube composed of cartilaginous rings and supporting tissue that connects the lung bronchi and the larynx; provides a road for air to enter and leave the lung

trachealis muscle: smooth muscle located in the fibroelastic membrane of the trachea

true vocal cord: one of the pair of folded, white membranes that take a free inner edge that oscillates equally air passes through to produce sound

type I alveolar cell: squamous epithelial cells that are the major cell type in the alveolar wall; highly permeable to gases

type Ii alveolar cell: cuboidal epithelial cells that are the minor jail cell type in the alveolar wall; secrete pulmonary surfactant

vestibular fold: office of the folded region of the glottis composed of mucous membrane; supports the epiglottis during swallowing

Solutions

Answers for Critical Thinking Questions

The pharynx has three major regions. The showtime region is the nasopharynx, which is connected to the posterior nasal crenel and functions equally an airway. The 2d region is the oropharynx, which is continuous with the nasopharynx and is connected to the oral cavity at the fauces. The laryngopharynx is connected to the oropharynx and the esophagus and trachea. Both the oropharynx and laryngopharynx are passageways for air and nutrient and beverage.
The epiglottis is a region of the larynx that is important during the swallowing of food or drink. Every bit a person swallows, the pharynx moves upward and the epiglottis closes over the trachea, preventing nutrient or drink from entering the trachea. If a person's epiglottis were injured, this mechanism would be impaired. Equally a consequence, the person may take problems with food or drink inbound the trachea, and possibly, the lungs. Over time, this may cause infections such as pneumonia to fix in.
The conducting zone of the respiratory system includes the organs and structures that are not direct involved in gas exchange, but perform other duties such as providing a passageway for air, trapping and removing debris and pathogens, and warming and humidifying incoming air. Such structures include the nasal cavity, throat, larynx, trachea, and well-nigh of the bronchial tree. The respiratory zone includes all the organs and structures that are directly involved in gas exchange, including the respiratory bronchioles, alveolar ducts, and alveoli.

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