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The respiratory system consists of ...

Nose, pharynx, larynx, trachea, bronchi, lungs


How is the respiratory system classified structurally?

(1) The upper respiratory system includes the nose, nasal cavity, pharynx, and associated structures; (2) the lower respiratory system includes the larynx, trachea, bronchi, and lungs.


How is the respiratory system classified functionally?

(1) The conducting zone consists of a series of inter- connecting cavities and tubes both outside and within the lungs. These include the nose, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles; their function is to filter, warm, and moisten air and conduct it into the lungs.
(2) The respiratory zone consists of tubes and tissues within the lungs where gas exchange occurs. These include the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli and are the main sites of gas exchange between air and blood.


What does the external nose consist of? Describe the arrangement of bone and cartilage in the nose.

The external nose is the portion of the nose visible on the face and consists of a supporting framework of bone and hyaline cartilage covered with muscle and skin and lined by a mucous membrane. The frontal bone, nasal bones, and maxillae form the bony framework of the external nose. The cartilaginous framework of the external nose consists of several pieces of hyaline cartilage connected to each other and certain skull bones by fibrous connective tissue. The components of the cartilaginous framework are the septal nasal cartilage, which forms the anterior portion of the nasal septum; the lateral nasal cartilages inferior to the nasal bones; and the alar cartilages, which form a portion of the walls of the nostrils. Because it consists of pliable hyaline cartilage, the cartilaginous framework of the external nose is somewhat flexible. On the undersurface of the external nose are two openings called the external nares or nostrils.


What are the three functions of the interior structures of the external nose?

(1) warming, moistening, and filtering incoming air; (2) detecting olfactory stimuli; and (3) modifying speech vibrations as they pass through the large, hollow resonating chambers.


What is meant by resonance?

Resonance refers to prolonging, amplifying, or modifying a sound by vibration.


What are the functions of the paranasal sinuses?

Besides producing mucus, the paranasal sinuses serve as resonating chambers for sound as we speak or sing.


What is the purpose of the bony and cartilaginous framework of the nose?

The bony and cartilaginous framework of the nose help to keep the vestibule and nasal cavity patent, that is, open or unobstructed.


Describe the nasal cavity.

The nasal cavity is a large space in the anterior aspect of the skull that lies inferior to the nasal bone and superior to the oral cavity; it is lined with muscle and mucous membrane. A vertical partition, the nasal septum, divides the nasal cavity into right and left sides. The anterior portion of the nasal septum consists primarily of hyaline cartilage; the remainder is formed by the vomer, perpendicular plate of the ethmoid, maxillae, and palatine bones.


What is the nasal cavity divided into?

A larger, inferior respiratory region and a smaller, superior olfactory region. The respiratory region is lined with pseudostratified ciliated columnar epithelium with numerous goblet cells, which is frequently called the respiratory epithelium. The anterior portion of the nasal cavity just inside the nostrils, called the nasal vestibule, is surrounded by cartilage; the superior part of the nasal cavity is surrounded by bone.


When the air first enters the nostrils, what does it pass through?

The vestibule, which is lined by skin containing coarse hairs that filter out large dust particles.


What extends out of each lateral wall of the nasal cavity?

Three shelves formed by projections of the superior, middle, and inferior nasal conchae. The conchae, almost reaching the nasal septum, subdivide each side of the nasal cavity into a series of groovelike air passageways—the superior, middle, and inferior nasal meatuses.


What lines the nasal cavity and its shelves?

Mucous membrane lines the nasal cavity and its shelves.


What are the functions of the nasal chonchae and meatuses?

Increases surface area in the internal nose and prevents dehydration by trapping water droplets during exhalation.


What happens to the air as it whirls around the chonchae and meatuses?

It is warmed by blood in the capillaries. Mucus secreted by the goblet cells moistens the air and traps dust particles. Drainage from the nasolacrimal ducts also helps moisten the air, and is sometimes assisted by secretions from the paranasal sinuses. The cilia move the mucus and trapped dust particles toward the pharynx, at which point they can be swallowed or spit out, thus removing the particles from the respiratory tract.


What cells make up the olfactory epithelium?

The olfactory receptor cells, supporting cells, and basal cells lie in the respiratory region, which is near the superior nasal conchae and adjacent septum. It contains cilia but no goblet cells.


What is the pharynx? Where is the pharynx situated?

The pharynx, or throat, is a funnel-shaped tube about 13 cm long that starts at the internal nares and extends to the level of the cricoid cartilage, the most inferior cartilage of the larynx (voice box). The pharynx lies just posterior to the nasal and oral cavities, superior to the larynx, and just anterior to the cervical vertebrae.


What is the wall of the pharynx composed of and what is it lined with?

Its wall is composed of skeletal muscles and is lined with a mucous membrane.


Relaxed skeletal muscles help keep the pharynx __________. Contraction of the skeletal muscles assists in ___________.

Deglutition (swallowing)


What are the functions of the pharynx?

The pharynx functions as a passageway for air and food, provides a resonating chamber for speech sounds, and houses the tonsils, which participate in immunological reactions against foreign invaders.


What are the three anatomical regions of the pharynx?

(1) nasopharynx, (2) oropharynx, and (3) laryngopharynx


How are the muscles of the entire pharynx arranged?

In two layers: an outer circular layer and an inner longitudinal layer.


Where is the nasopharynx found?

The superior portion of the pharynx, called the nasopharynx, lies posterior to the nasal cavity and extends to the soft palate.


What is the soft palate?

The soft palate, which forms the posterior portion of the roof of the mouth, is an arch-shaped muscular partition between the nasopharynx and oropharynx that is lined by mucous membrane.


What are the five openings in the wall of the nasal pharynx?

Two internal nares, two openings that lead into the auditory (pharyngotympanic) tubes (commonly known as the eustachian tubes), and the opening into the oropharynx. The posterior wall also contains the pharyngeal tonsil, or adenoid.


What are the functions of the nasopharynx?

Through the internal nares, the nasopharynx receives air from the nasal cavity along with packages of dust-laden mucus. The nasopharynx is lined with pseudostratified ciliated columnar epithelium, and the cilia move the mucus down toward the most inferior part of the pharynx. The nasopharynx also exchanges small amounts of air with the auditory tubes to equalize air pressure between the middle ear and the atmosphere.


Describe the location of the oropharynx.

The intermediate portion of the pharynx, the oropharynx, lies posterior to the oral cavity and extends from the soft palate inferiorly to the level of the hyoid bone. It has only one opening into it, the fauces (throat), the opening from the mouth.


What are the functions of the oropharynx?

This portion of the pharynx has both respiratory and digestive functions, serving as a common passageway for air, food, and drink.


What is the oropharynx lined with and why? What is found in the oropharynx?

Because the oropharynx is subject to abrasion by food par- ticles, it is lined with nonkeratinized stratified squamous epithe- lium. Two pairs of tonsils, the palatine and lingual tonsils, are found in the oropharynx.


Where does the laryngopharynx begin? What does it open into?

It is the inferior portion of the larynx, which begins at the level of the hyoid bone.
At its inferior end it opens into the esophagus (food tube) posteriorly and the larynx (voice box) anteriorly.


How is the laryngopharynx similar to the oropharynx?

Both a respiratory and a digestive pathway and is lined by nonkeratinized stratified squamous epithelium.


Describe the trachea

The trachea, or windpipe, is a tubular passageway for air that is about 12 cm (5 in.) long and 2.5 cm (1 in.) in diameter. It is located anterior to the esophagus and extends from the larynx to the superior border of the fifth thoracic vertebra (T5), where it divides into right and left primary bronchi.


List the layers of the tracheal wall from deep to superficial.

1) Mucosa
2) Submucosa
3) Hyaline cartilage
4) Adventitia


What does the mucosa of the trachea consist of?

An epithelial layer of pseudostratified ciliated columnar epithelium and an underlying layer of lamina propria that contains elastic and reticular fibers. It provides the same protection against dust as the membrane lining the nasal cavity and larynx.


What does the submucosa of the trachea consist of?

Areolar connective tissue that contains seromucous glands and their ducts.


Describe how the hyaline cartilage of the trachea is organised. What are the functions of the different components?

The 16–20 incomplete, horizontal rings of hyaline cartilage resemble the letter C, are stacked one above another, and are connected by dense connective tissue. The open part of each C-shaped cartilage ring faces posteriorly toward the esophagus and is spanned by a fibromuscular membrane. Within this membrane are transverse smooth muscle fibers, called the trachealis muscle, and elastic connective tissue that allow the diameter of the trachea to change subtly during inhalation and exhalation, which is important in maintaining efficient airflow. The solid C-shaped cartilage rings provide a semirigid support to maintain patency so that the tracheal wall does not collapse inward (especially during inhalation) and obstruct the air passageway. The adventitia of the trachea consists of areolar connective tissue that joins the trachea to surrounding tissues.


How is the right main bronchus different to the left main bronchus?

The right main bronchus is more vertical, shorter, and wider than the left. As a result, an aspirated object is more likely to enter and lodge in the right main bronchus than the left


How are the main bronchi similar to the trachea?

Contain incomplete rings of cartilage and are lined by pseudostratified ciliated columnar epithelium.


What is the carina? What is the most sensitive area of the entire larynx and trachea for triggering a cough reflex? What does widening and distortion of the carina indicate?

- An internal ridge found where the trachea divides into right and left main bronchi. It is formed by a posterior and somewhat inferior projection of the last tracheal cartilage.
- The mucous membrane of the carina
- A carcinoma of the lymph nodes around the region where the trachea divides.


Describe the branching of the bronchi and bronchioles in the lungs after the main bronchi.

On entering the lungs, the main bronchi divide to form smaller bronchi—the lobar (secondary) bronchi, one for each lobe of the lung. (The right lung has three lobes; the left lung has two.) The lobar bronchi continue to branch, forming still smaller bronchi, called segmental (tertiary) bronchi, that supply the specific bronchopulmonary segments (10) within the lobes. The segmental bronchi then divide into bronchioles. Bronchioles in turn branch repeatedly, and the smallest ones branch into even smaller tubes called terminal bronchioles.


What type of cells do terminal bronchioles contain?

These bronchioles contain club (Clara) cells, columnar, nonciliated cells interspersed among the epithelial cells. Club cells may protect against harmful effects of inhaled toxins and carcinogens, produce surfactant (discussed shortly), and function as stem cells (reserve cells), which give rise to various cells of the epithelium.


What do the terminal bronchi represent?

The end of the conducting zone


Describe the structural changes that occur as branching becomes more extensive in the lungs.

1. The mucous membrane in the bronchial tree changes from pseudostratified ciliated columnar epithelium in the main bronchi, lobar bronchi, and segmental bronchi to ciliated simple columnar epithelium with some goblet cells in larger bronchioles, to mostly ciliated simple cuboidal epithelium with no goblet cells in smaller bronchioles, to mostly nonciliated simple cuboidal epithelium in terminal bronchioles.
2. Plates of cartilage gradually replace the incomplete rings of cartilage in main bronchi and finally disappear in the distal bronchioles.
3. As the amount of cartilage decreases, the amount of smooth muscle increases. Smooth muscle encircles the lumen in spiral bands and helps maintain patency. However, because there is no supporting cartilage, muscle spasms can close off the air- ways. This is what happens during an asthma attack, which can be a life-threatening situation.


What are the ways that ciliated and nonciliated epithelium removes inhaled particles.

Ciliated epithelium of the respiratory membrane removes inhaled particles in two ways. Mucus produced by goblet cells traps the particles, and the cilia move the mucus and trapped particles toward the pharynx for removal. In regions where nonciliated simple cuboidal epithelium is present, inhaled particles are removed by macrophages.


What can cause dilation and constriction of bronchioles?

During exercise, activity in the sympathetic division of the autonomic nervous system (ANS) increases and the adrenal medulla releases the hormones epinephrine and norepinephrine; both of these events cause relaxation of smooth muscle in the bronchioles, which dilates the airways. Because air reaches the alveoli more quickly, lung ventilation improves. The parasympathetic division of the ANS and mediators of allergic reactions such as histamine have the opposite effect, causing contraction of bronchiolar smooth muscle, which results in constriction of distal bronchioles.


What is a consequence of the lungs being divided into two anatomically distinct chambers by the heart and other structures of the mediastinum?

If trauma causes one lung to collapse, the other may remain expanded.


What is each lungs enclosed and protected by?

A double-layered serous membrane called the pleural membrane. The superficial layer, called the parietal pleura, lines the wall of the thoracic cavity; the deep layer, the visceral pleura, covers the lungs themselves.


What is found between the visceral and parietal pleura? What function does it serve?

Between the visceral and parietal pleurae is a small space, the pleural cavity, which contains a small amount of lubricating fluid secreted by the membranes. This pleural fluid reduces friction between the membranes, allowing them to slide easily over one another during breathing. Pleural fluid also causes the two membranes to adhere to one another just as a film of water causes two glass microscope slides to stick together, a phenomenon called surface tension.Separate pleural cavities surround the right and left lung.


What is pleuritis?

Inflammation of the pleural membrane, called pleurisy or pleuritis, may in its early stages cause pain due to friction between the parietal and visceral layers of the pleura. If the inflammation persists, excess fluid accumulates in the pleural space, a condition known as pleural effusion.


What is the position of the lungs?

The lungs extend from the diaphragm to just slightly superior to the clavicles and lie against the ribs anteriorly and posteriorly. The broad inferior portion of the lung, the base, is concave and fits over the convex area of the diaphragm. The narrow superior portion of the lung is the apex. The surface of the lung lying against the ribs, the costal surface, matches the rounded curvature of the ribs. The mediastinal (medial) surface of each lung contains a region, the hilum, through which bronchi, pulmonary blood vessels, lymphatic vessels, and nerves enter and exit. These structures are held together by the pleura and connective tissue and constitute the root of the lung. Medially, the left lung also contains a concavity, the cardiac notch, in which the apex of the heart lies.


Why is the left lung 10% smaller than the right? What else is different about the left and right side?

Due to the space occupied by the heart.
Although the right lung is thicker and broader, it is also somewhat shorter than the left lung because the diaphragm is higher on the right side, accommodating the liver that lies inferior to it.


What is thoracentesis?

Removal of excessive fluid in the pleural cavity can be accomplished without injuring lung tissue by inserting a needle anteriorly through the seventh intercostal space, a procedure called thoracentesis. The needle is passed along the superior border of the lower rib to avoid damage to the intercostal nerves and blood vessels. Inferior to the seventh intercostal space there is danger of penetrating the diaphragm.


Describe how the lungs are separated into lobes on the right and left lung

One or two fissures divide each lung into lobes. Both lungs have an oblique fissure, which extends inferiorly and anteriorly; the right lung also has a horizontal fissure. The oblique fissure in the left lung separates the superior lobe from the inferior lobe. In the right lung, the superior part of the oblique fissure separates the superior lobe from the inferior lobe; the inferior part of the oblique fissure separates the inferior lobe from the middle lobe, which is bordered superiorly by the horizontal fissure.


What is advantageous about having bronchopulmonary segments?

Disorders can be removed surgically without seriously disrupting the surrounding tissue.


What does each lobule contain and what is it wrapped in?

each lobule is wrapped in elastic connective tissue and contains a lymphatic vessel, an arteriole, a venule, and a branch from a terminal bronchiole


What do terminal bronchioles subdivide into?

Microscopic branches called respiratory bronchioles


As the respiratory bronchi- oles penetrate more deeply into the lungs, the epithelial lining changes from simple __________ to ________ squamous.



What do respiratory bronchioles subdivide into?

Alveolar ducts, which consist of simple squamous epithelium


The respiratory passages from the trachea to the alveolar ducts contain about ___ orders of branching.



What is an alveolus and alveolar sac.

An alveolus is a cup-shaped outpouching lined by simple squamous epithelium and supported by a thin elastic basement membrane; an alveolar sac consists of two or more alveoli that share a common opening


What are the two types of alveolar epithelial cells?

The more numerous type I alveolar (squamous pulmonary epithelial) cells are simple squamous epithelial cells that form a nearly continuous lining of the alveolar wall. Type II alveolar cells, also called septal cells, are fewer in number and are found between type I alveolar cells. The thin type I alveolar cells are the main sites of gas exchange. Type II alveolar cells, rounded or cuboidal epithelial cells with free surfaces containing microvilli, secrete alveolar fluid, which keeps the surface between the cells and the air moist.


What is included in the alveolar fluids? What is its function?

Surfactant, a complex mixture of phospholipids and lipoproteins. Surfactant lowers the surface tension of alveolar fluid, which reduces the tendency of alveoli to collapse and thus maintains their patency (described later).


What is associated with the alveolar wall?

Alveolar macrophages: phagocytes that remove fine dust particles and other debris from the alveolar spaces.
Also present are fibroblasts that produce reticular and elastic fibers.


What is underlying the type I alveolar cells?

An elastic basement membrane


What are the four layers of the respiratory membrane?

1. A layer of type I and type II alveolar cells and associated alveolar macrophages that constitutes the alveolar wall
2. An epithelial basement membrane underlying the alveolar wall
3. A capillary basement membrane that is often fused to the
epithelial basement membrane
4. The capillary endothelium


How thick is the respiratory membrane?

Despite having several layers, the respiratory membrane is
very thin—only 0.5 􏱌m thick, about one-sixteenth the diameter of a red blood cell—to allow rapid diffusion of gases.


The lungs receive blood via which two sets of arteries?

Pulmonary and bronchial arteries.


Describe what happens in ventilation-perfusion coupling,

A unique feature of pulmonary blood vessels is their constriction in response to localized hypoxia (low O2 level). In all other body tissues, hypoxia causes dilation of blood vessels to increase blood flow. In the lungs, however, vasoconstriction in response to hypoxia diverts pulmonary blood from poorly ventilated areas of the lungs to well-ventilated regions for more efficient gas exchange. This phenomenon is known as ventilation– perfusion coupling because the perfusion (blood flow) to each area of the lungs matches the extent of ventilation (airflow) to alveoli in that area.


What factors can compromise patency?

Crushing injuries to bone and cartilage, a deviated nasal septum, nasal polyps, inflammation of mucous membranes, spasms of smooth muscle, and a deficiency of surfactant.


What is the passive diffusion governed by? Describe what these laws are used to determine.

Dalton's Law and Henry's Law
Dalton’s law is important for understanding how gases move down their pressure gradients by diffusion, and Henry’s law helps explain how the solubility of a gas relates to its diffusion.