PREFINAL: RESPIRATORY SYSTEM Flashcards by Chin Lys

2 COMPONENTS OF RESPIRATORY SYSTEM

Conducting portion
Respiratory portion

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The conducting portion, which consists of the___(7)

nasal cavities, pharynx, larynx, trachea, bronchi (Gr. bronchos, windpipe), bronchioles, and terminal bronchioles

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The respiratory portion, where the system’s main function of gas exchange occurs, consisting of_____(3)

respiratory bronchioles, alveolar ducts, and alveoli

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• The left and right nasal cavities each have two components: the external,
dilated vestibule and the internal nasal cavity.
• Skin of the nose enters the nares (nostrils) partway into the vestibule and includes sweat glands, sebaceous glands, and coarse, moist vibrissae (hairs), which filter out particulate material from inspired air. Within the vestibule, the epithelium loses its keratinized nature and undergoes a transition to typical pseudostratified columnar epithelium which also lines the nasal cavities.
• The nasal cavities lie within the skull as two cavernous chambers separated by the osseous nasal septum.

NASAL CAVITIES

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The left and right nasal cavities each have two components:

the external, dilated vestibule and the internal nasal cavity.

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Extending from each lateral wall are three bony shelflike projections called

conchae, or turbinate bones

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The thin mucus layer produced by these glands and goblet cells serves to trap particulate and gaseous air impurities that are then removed. The secretions also contain immunoglobulin A (IgA) from
plasma cells in the lamina propria.

Small seromucous glands

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Small seromucous glands: The thin mucus layer produced by these glands
and goblet cells serves to trap particulate and gaseous air impurities that are then removed. The secretions also contain __________ from
plasma cells in the lamina propria.

immunoglobulin A (IgA)

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Epithelium on the middle and inferior conchae is ________ the roof of the nasal cavities and the superior conchae are covered with specialized olfactory epithelium.

respiratory epithelium

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Most of the nasal cavities and conducting portion of the system is lined with mucosa having ciliated
pseudostratified columnar epithelium commonly known as _______.

respiratory epithelium

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5 CELLS OF RESPIRATORY EPITHELIUM

Ciliated columnar cells
Goblet cells
Brush cells
Small granule cells (or Kulchitsky cells)
Basal cells

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are the most abundant, each with 250-300 cilia on its apical surface.

Ciliated columnar cells

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are also numerous and predominate in some areas with basal nuclei and apical domains filled with granules of mucin glycoproteins.

Goblet cells

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are a much less numerous, columnar cell type, in which a small apical surface bears sparse, blunt microvillus. Brush cells are chemosensory receptors resembling gustatory cells, with similar signal transduction components and synaptic contact with afferent nerve endings on their basal surfaces

Brush cells

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are difficult to distinguish in routine preparations but possess numerous dense core granules 100-300 nm in diameter. Like enteroendocrine cells of the gut, they are part of the diffuse neuroendocrine system (DNES) (see Chapter 20). Like brush cells, they represent only about 3% of the cells in respiratory epithelium.

Small granule cells (or Kulchitsky cells)

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are mitotically active stem and progenitor cells that give rise to the other epithelial cell types

Basal cells

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The olfactory chemoreceptors for the sense of smell are in the olfactory epithelium, a specialized region of
the mucous membrane covering the superior conchae at the roof of the nasal cavity.

OLFACTORY EPITHELIUM

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OLFACTORY EPITHELIUM 3 CELL MAJOR TYPES

Olfactory neurons
Supporting cells
Basal cells

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are bipolar neurons present throughout this epithelium. The axons leave the epithelium and unite in the lamina propria as very small nerves that then pass to the brain through foramina in the cribriform plate of the ethmoid bone. There they form the olfactory nerve (cranial nerve I) and eventually synapse with neurons in the olfactory bulb of the brain.

Olfactory neurons

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are columnar, with narrow bases and broad, cylindrical apexes containing the nuclei and extending microvilli into the fluid layer. The supportive role of these cells is not well understood, but they express abundant ion channels, which help maintain a microenvironment conducive to olfactory function and survival.

Supporting cells

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are small, spherical, or cone-shaped cells near the basal lamina. These are the stem cells for the other two types, replacing the olfactory neurons every 2-3 months and support cells less frequently.

Basal cells

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The loss or reduction of the ability to smell, _________, respectively, can be caused by traumatic damage to the ethmoid bone that severs olfactory nerve axons or by damage to the olfactory epithelium caused by intranasal drug use.

anosmia or hyposmia

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• are bilateral cavities in the frontal, maxillary, ethmoid, and sphenoid bones of the skull. They are lined with a thinner respiratory epithelium having fewer goblet cells.
• The lamina propria contains only a few small glands and is continuous with the underlying periosteum.
• communicate with the nasal cavities through small openings; mucus produced there is moved into the nasal passages by the activity of the ciliated epithelial cells.

PARANASAL SINUSES

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is an inflammatory process of the sinuses that may persist for long periods of time, mainly because
of obstruction of drainage orifices.

Sinusitis

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Chronic sinusitis and bronchitis are components of primary ciliary dyskinesia, or _______, an inherited genetic disorder characterized by defective ciliary action.

Kartagener syndrome

• The nasal cavities open posteriorly into the nasopharynx, the first part of the pharynx. • The nasopharynx is continuous caudally with the oropharynx (throat), the posterior part of the oral cavity leading to the larynx and esophagus. • the nasopharynx lining is respiratory epithelium, and its mucosa contains the medial pharyngeal tonsil and the openings of the two auditory tubes which connect to each middle ear cavity.

PHARYNX

• The larynx is a short (4 cm × 4 cm) passage for air between the pharynx and the trachea. • Its rigid wall is reinforced by hyaline cartilage (in the thyroid, cricoid, and the inferior arytenoid cartilages) and smaller elastic cartilages (in the epiglottis, cuneiform, corniculate, and the superior arytenoid cartilages), all of which are connected by ligaments. In addition to maintaining an open airway, movements of these cartilages by skeletal muscles participate in sound production during phonation.

LARYNX

VOICE BOX

Larynx

a flattened structure projecting from the upper rim of the larynx, serves to prevent swallowed food or fluid from entering that passage.

EPIGLOTTIS

EPIGLOTTIS Its upper, or lingual, surface has

stratified squamous epithelium

EPIGLOTTIS at variable points on its laryngeal surface this epithelium undergoes a transition to

ciliated pseudostratified columnar (respiratory) epithelium

During phonation muscles of the larynx draw the paired vocal folds together (adduction), which narrows the opening between them, the rima glottidis, and air expelled from the lungs causes the adducted vocal folds (cords) to vibrate and produce sound.

EPIGLOTTIS

Below the epiglottis and vestibule of the larynx, the mucosa projects bilaterally into the lumen with two pairs of folds separated by a narrow space or ventricle:

• The upper pair, the immovable vestibular folds, is partly covered with typical respiratory epithelium overlying numerous seromucous glands and occasional lymphoid nodules. • The lower pair of folds, the vocal folds (or cords), have features important for phonation or sound production. • Each is covered with nonkeratinized stratified squamous epithelium that protects the mucosa from abrasion and desiccation from rapid air movement. • A dense regular bundle of elastic connective tissue, the vocal ligament, supports the free edge of each vocal fold. • Deep to the mucosa are large bundles of striated fibers comprising the vocalis muscle that allow each vocal fold to be moved.

Inflammation of the larynx, or _______, is typically due to viral infection and is usually accompanied by edema or swelling of the organ’s lamina propria. This changes the shape of the vocal folds or other parts of the larynx, producing hoarseness or complete loss of voice. Croup is a similar syndrome in young children in which edema of the laryngeal mucosa is accompanied by both hoarseness and coughs that typically are loud and harsh

laryngitis

are frequent in the stratified squamous epithelium of the true vocal cords, affecting the voice.

Benign reactive polyps, called singer’s nodules

10-12 cm long in adults, is lined with typical respiratory mucosa in which the lamina propria contains numerous seromucous glands producing watery mucus.

TRACHEA

A series with about a dozen C-shaped rings of hyaline cartilage between the submucosa and adventitia reinforces the wall and keeps the tracheal lumen open.

TRACHEA

The open ends of the cartilage rings are on the posterior surface, against the esophagus, and are bridged by a bundle of smooth muscle called the trachealis muscle and a sheet of fibroelastic tissue attached to the perichondrium.

TRACHEA

WINDPIPE

TRACHEA

is a reflex action produced most often by viral infection or other irritation of the trachea or other region of the respiratory tract. A persistent dry cough, in which no mucus (phlegm) is produced, can be treated by cough suppressants that act on the brain stem and vagus nerve, while productive coughs are often treated with expectorants that help loosen mucus covering the respiratory mucosa.

Coughing

The trachea divides into two primary bronchi that enter each lung at the hilum, along with arteries, veins, and lymphatic vessels

BRONCHIAL TREE AND LUNG

After entering the lungs, the primary bronchi course downward and outward, giving rise to three secondary (lobar) bronchi in the right lung and two in the left lung each of which supplies a pulmonary lobe.

BRONCHIAL TREE AND LUNG

These lobar bronchi again divide, forming tertiary (segmental) bronchi. Each of the tertiary bronchi, together with the smaller branches it supplies, constitutes a bronchopulmonary segment— approximately 10%-12% of each lung with its own connective tissue capsule and blood supply.

BRONCHIAL TREE AND LUNG

• The tertiary bronchi give rise to smaller and smaller bronchi, whose terminal branches are called bronchioles. Each bronchiole enters a pulmonary lobule, where it branches to from five to seven terminal bronchioles. • Moving through the smaller bronchi and bronchioles toward the respiratory portion, the histological organization of both the epithelium and the underlying lamina propria gradually becomes more simplified.

BRONCHIAL TREE AND LUNG

• Each primary bronchus branches repeatedly, with each branch becoming progressively smaller until it reaches a diameter of 1-2 mm. • The mucosa of the larger bronchi is structurally like the tracheal mucosa except for the organization of cartilage and smooth muscle In the primary bronchi most cartilage rings completely encircle the lumen, but as the bronchial diameter decreases, cartilage rings are gradually replaced with smaller isolated plates of hyaline cartilage.

BRONCHI

Numerous lymphocytes are found both within the lamina propria and among the epithelial cells. Lymphatic nodules are present, especially at the branching points of the bronchial tree. Mucosa-associated lymphoid tissue (MALT) also becomes relatively more abundant as bronchi become smaller and the cartilage and other connective tissue are reduced.

BRONCHI

are the intralobular airways with diameters of 1 mm or less, formed after about the tenth generation of branching; they lack both mucosal glands and cartilage, although dense connective tissue is associated with the smooth muscle.

Bronchioles

the epithelium is still ciliated pseudostratified columnar, but this decreases in height and complexity to become ciliated simple columnar or simple cuboidal epithelium in the smallest terminal bronchioles, which are the last parts of the air conducting system The ciliated epithelial lining of bronchioles begins the mucociliary apparatus or escalator, important in clearing debris and mucus by moving it upward along the bronchial tree and trachea.

In the larger bronchioles

consists largely of club cells or bronchiolar exocrine cells (previously called Clara cells), with nonciliated, dome-shaped apical ends containing secretory granules. These exocrine cells have various functions

cuboidal epithelium of terminal bronchioles

Bronchioles constitute the air passages affected most often, especially in young children, by the measles virus or adenovirus, both of which can cause _____.

bronchiolitis

_______ is a common condition produced by chronic inflammation within the bronchial tree of the lungs. The disorder is characterized by sudden constrictions of the smooth muscle in bronchioles called bronchospasms, or bronchial spasms.

Asthma

Each terminal bronchiole subdivides into two or more respiratory bronchioles, which always include saclike alveoli and represent, therefore, the first part of this system’s respiratory region.

RESPIRATORY BRONCHIOLES

Distal ends of respiratory bronchioles branch into tubes called alveolar ducts, which are completely lined by the openings of alveoli.

ALVEOLAR DUCTS

Larger clusters of alveoli called _______ form the ends of alveolar ducts distally and occur occasionally along their length. The lamina propria is now extremely thin, consisting essentially of a web of elastic and reticular fibers that encircles the alveolar openings and closely surrounds each alveolus. Prominent in this sparse connective tissue, a network of capillaries also surrounds each alveolus.

alveolar sacs

_________ can be produced by various types of injuries to the alveolar epithelial and the capillary endothelial cells. Common causes of such injuries include viral and bacterial respiratory tract infections; inhalation of toxic gases, chemicals, or air with excessive oxygen; and fat embolism syndrome, in which adipocytes enter the blood during surgery, circulate, and later block the capillary beds. With removal of the initiating factors, normal alveolar wall components can often be restored and at least partial function restored.

Diffuse alveolar damage or adult respiratory distress syndrome

are saclike evaginations, each about 200 μm in diameter, from the respiratory bronchioles, alveolar ducts, and alveolar sacs. Along with the airways, alveoli are responsible for the spongy structure of the lungs.

ALVEOLI

3 TYPES OF ALVEOLAR CELLS

Type I alveolar cells (or type I pneumocytes) Type II alveolar cells (type II pneumocytes or septal cells) Alveolar macrophages, also called dust cells

are also extremely attenuated cells lining the alveolar surfaces. Type I cells constitute the alveolar side of the blood-air barrier and make up about 95% of the alveolar lining.

Type I alveolar cells (or type I pneumocytes)

are cuboidal cells bulging into the air space, interspersed among the type I alveolar cells, and bound to them with tight junctions and desmosomes.

Type II alveolar cells (type II pneumocytes or septal cells)

are found in alveoli and in the interalveolar septum. Tens of millions of monocytes migrate daily from the microvasculature into the lung tissue, where they phagocytose erythrocytes lost from damaged capillaries and airborne particulate matter that has penetrated as far as alveoli.

Alveolar macrophages, also called dust cells

t or f Active alveolar macrophages can often be distinguished from type II pneumocytes because they are slightly darker due to their content of dust and carbon from air and complexed iron (hemosiderin) from erythrocytes.

Filled macrophages have various fates:

1. Most migrate into bronchioles where they move up the mucociliary apparatus for removal into the esophagus. 2. Others exit the lungs in the lymphatic drainage. 3. Some remain in the interalveolar septa connective tissue for years.

Inhalation of toxic gases or similar materials can kill type I and II cells lining pulmonary alveoli. Death of alveolar cells stimulates mitotic activity in the remaining type II cells, the progeny of which become progenitors for both cell types. With increased toxic stress, stem cells are also stimulated to divide and give rise to new alveolar cell progenitors.

REGENERATION IN THE ALVEOLAR LINING

The leading cause of death in premature babies, is due to incomplete differentiation of type II alveolar cells which results in deficit of surfactant and difficulty in expanding the alveoli in breathing.

Infant respiratory distress syndrome

Treatment involves ______ to provide both continuous positive airway pressure (CPAP) and exogenous surfactant, either synthesized chemically or purified from lungs of cattle.

insertion of an endotracheal tube

the lungs become congested with blood, and erythrocytes pass into the alveoli, where they are phagocytized by alveolar macrophages.

congestive heart failure

In such cases, these macrophages are called __________ when present in the lung and sputum; they are identified by a positive histochemical reaction for iron pigment (hemosiderin)

heart failure cells

, a chronic lung disease most commonly caused by cigarette smoking, involves dilation and permanent enlargement of the bronchioles leading to pulmonary acini. Emphysema is accompanied by loss of cells in the alveoli and other parts of the airway walls, leading to an irreversible loss of respiratory function. Any type of infection in the respiratory regions of the lung produces the local inflammatory condition called pneumonia

Emphysema

• Blood circulation in the lungs includes both the pulmonary circulation, carrying O2 -depleted blood for gas exchange, and bronchial circulation, carrying O2 -rich blood. • Both parasympathetic and sympathetic autonomic fibers innervate the lungs and control reflexes regulating smooth muscle contractions which determine the diameters of the airways. General visceral afferent fibers, carrying poorly localized pain sensations, are also present. The nerves are found primarily in the connective tissue surrounding the larger elements of the bronchial tree and exit the lung at the hilum.

LUNG VASCULATURE & NERVES

The lung’s outer surface and the internal wall of the thoracic cavity are covered by a serous membrane called the ______.

pleura

The membrane attached to lung tissue is called the ____

visceral pleura

the membrane lining the thoracic walls is the _____

parietal pleura

Between the parietal and visceral layers, the narrow pleural cavity is entirely lined with the mesothelial cells producing a ________, which acts as a lubricant, facilitating the smooth sliding of one surface over the other during respiratory movements.

thin film of serous fluid

The condition _______ is a partially or completely collapsed lung caused by air trapped in the pleural cavity, typically resulting from blunt or penetrating trauma to the chest and producing shortness of breath and hypoxia.

pneumothorax

Inflammation of the pleura, a condition called either ______, is most commonly caused by an acute viral infection or pneumonia.

pleuritis or pleurisy

_______ in the pleural cavity produces shortness of breath and can be one result of inflamed pleura.

Pleural effusion or fluid buildup

______, which is closely correlated with a history of smoking, arises most often from epithelial cells of segmental bronchi.

Squamous cell carcinoma

_____, the most common lung cancer in nonsmokers, usually arises from epithelial cells more peripherally, in bronchioles and alveoli.

Adenocarcinoma

_____, a less common but highly malignant Small cell carcinoma, a less common but highly malignant form of lung cancer, develops after neoplastic transformation of small granule Kulchitsky cells in bronchial respiratory epithelium form of lung cancer, develops after neoplastic transformation of small granule Kulchitsky cells in bronchial respiratory epithelium.

Small cell carcinoma