Quiz 7 Respiratory System

Comprehensive flashcards covering the anatomical organization, histology, cell types, transitions, and ultrastructure of the upper and lower respiratory tracts from Dr. Joel Collazo's lecture notes.

Which anatomical structures compose the upper respiratory tract?

The sphenoidal sinus, frontal sinus, nasal cavity, and pharynx.

Which anatomical structures compose the lower respiratory tract?

The larynx, trachea, bronchi, lungs (including bronchioles, respiratory bronchioles, alveolar ducts, and alveoli), pleura, and diaphragm.

Which organs make up the conducting portion of the respiratory system?

The nasal cavities, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles.

Which structures make up the respiratory portion of the respiratory system?

The respiratory bronchioles, alveolar ducts, and alveoli.

What structures and tissue cover the entrance of the nasal vestibule?

Skin from the nose containing sweat glands, sebaceous glands, and coarse, moist vibrissae.

How does the lining of the nasal vestibule change deeper in the cavity?

It transitions into non-keratinized respiratory epithelium lacking sweat or sebaceous glands, which continues into the nasal cavity.

Where is specialized olfactory epithelium located in the nasal cavity?

On the roof of the nasal cavity and the superior nasal conchae.

How does blood flow in the capillary loops of the nasal cavity lamina propria relative to inspired air?

Blood flows in the opposite direction to the flow of inspired air to warm it efficiently.

What types of glands and immune elements are present in the lamina propria of the nasal cavity?

Seromucous glands and plasma cells producing $\text{IgA}$.

What is the histological classification and basement membrane characteristic of respiratory epithelium?

It is a ciliated pseudostratified columnar epithelium supported by a very thick basement membrane.

How many cilia are typically found on the apical domain of ciliated columnar cells in respiratory epithelium?

Approximately $200\text{ to }300$ cilia.

What are the characteristic features of goblet cells in the respiratory epithelium?

They feature basal nuclei and apical granules containing mucin glycoproteins, and they lack cilia.

What are brush cells in the respiratory epithelium, and what is their role?

Less numerous columnar cells with a few apical microvilli that act as chemosensory receptors.

What are small granule (Kulchitsky) cells in the respiratory epithelium?

Dense-core-granule-containing neuroendocrine cells that are part of the DNES and do not reach the apical surface.

What is the function and apical extent of basal cells in the respiratory epithelium?

They are mitotically active stem and progenitor cells that do not reach the apical surface.

What are the three major cell types found in the olfactory epithelium?

Olfactory neurons, supporting (sustentacular) cells, and basal cells.

What is the nature and function of the secretions from the olfactory glands of Bowman?

They are serous glands in the lamina propria producing a flowing fluid that surrounds the cilia of olfactory neurons to dissolve odorant molecules.

What are the structural characteristics of olfactory receptor neurons?

They are bipolar neurons with central nuclei, an apical dendritic end with a knoblike swelling containing about a dozen basal bodies from which cilia extend, and basal axons entering the cribriform plate of the ethmoid bone.

What histological features characterize supporting cells in the olfactory epithelium?

Columnar shape with a narrow base, a broad cylindrical apex containing the nucleus, junctional complexes connecting them to olfactory neurons, and abundant ion channels in their membranes.

What are the characteristics of basal cells in the olfactory epithelium?

Small, spherical or cone-shaped stem cells located near the basal lamina.

What epithelium and connective tissue arrangement characterizes the paranasal sinuses?

Thin respiratory epithelium with few goblet cells, supported by a lamina propria with few small glands that is continuous with the periosteum.

What type of epithelium and specialized structures are found in the nasopharynx?

Respiratory epithelium, housing the pharyngeal tonsil in its mucosa and the openings of the auditory tubes.

What type of epithelium lines the oropharynx and laryngopharynx?

Stratified squamous epithelium.

Which cartilages of the larynx are composed of hyaline cartilage?

The thyroid cartilage, cricoid cartilage, and inferior arytenoids.

Which cartilages of the larynx are composed of elastic cartilage?

The epiglottis, cuneiform cartilages, corniculate cartilages, and superior arytenoids.

How do the epithelial coverings on the lingual and laryngeal surfaces of the epiglottis differ?

The upper (lingual) surface is lined by stratified squamous epithelium, while the laryngeal surface transitions to ciliated pseudostratified columnar epithelium.

What histological components are found within the vestibular folds (false vocal cords)?

Partial covering by respiratory epithelium and a lamina propria containing seromucous glands and lymphoid nodules.

What is the histological organization of the vocal folds (true vocal cords)?

Covered by non-keratinized stratified squamous epithelium, supported by dense regular CT (the vocal ligament), with large bundles of skeletal muscle (vocalis muscle) deep to the mucosa.

What are the four principal histological layers of the tracheal wall?

Mucosa, submucosa, hyaline cartilage layer (C-shaped rings), and adventitia.

What tissue components constitute the tracheal mucosa?

Respiratory epithelium, a loose CT lamina propria rich in elastic fibers, and seromucous glands.

How does tracheal submucosa differ in connective tissue density compared to typical submucosa?

It consists of loose CT (slightly denser than the lamina propria), whereas submucosa in many other organs is composed of dense CT.

What structures close the open posterior gap of the tracheal cartilage rings?

The trachealis smooth muscle and a fibroelastic connective tissue membrane.

What age-related change can occur in the C-shaped hyaline cartilages of the trachea?

Some of the hyaline cartilage may calcify and be replaced by bone tissue with advancing age.

What comprises the tracheal adventitia and what is its role?

Dense CT containing larger blood and lymphatic vessels and nerves that binds the trachea to adjacent structures.

What cell types and lymphoid elements are present in the tracheal lamina propria?

Fibroblasts, lymphocytes, plasma cells, eosinophils, mast cells, and diffuse/nodular lymphoid tissue (BALT).

What gland varieties are present in the submucosa of the trachea?

Mostly mucous glands, alongside serous and mixed glands containing mucous acini with serous demilunes.

What airway territory is supplied by each primary bronchus?

Each primary bronchus supplies one lung.

What airway territory is supplied by each secondary bronchus?

Each secondary bronchus supplies a pulmonary lobe.

What structural unit is formed by a tertiary bronchus and its branches?

A bronchopulmonary segment, each enveloped in a connective tissue capsule with its own blood supply.

What airway enters a pulmonary lobule, and what is the lobule's anatomical orientation?

A bronchiole enters each pulmonary lobule, which is delineated with CT, has a pyramidal shape, and has its apex aimed at the hilum.

What is the diameter threshold that characterizes bronchioles?

A diameter of $\le 1\,\text{mm}$.

What are the five distinct histological layers in the wall of intrapulmonary bronchi?

Mucosa, muscularis, submucosa, cartilage layer, and adventitia.

How does the muscularis layer change from intrapulmonary bronchi to bronchioles?

Bronchi have prominent spiral bands of smooth muscle crisscrossing with elastic fibers, which become a prominent complete circular band in bronchioles.

How does cartilage structure change between extrapulmonary bronchi, intrapulmonary bronchi, and bronchioles?

Extrapulmonary bronchi have circular rings of cartilage; intrapulmonary bronchi have cartilage plates; bronchioles lack cartilage entirely.

In which airway segment do submucosal glands completely disappear?

Starting in the bronchioles (bronchioles do not have glands).

Describe the epithelial transition from larger bronchioles down to terminal bronchioles.

Pseudostratified columnar with fewer goblet cells transitions to ciliated simple columnar with much fewer goblet cells, and finally to ciliated simple cuboidal with no goblet cells.

Where in the lower respiratory tract does the mucociliary escalator begin?

At the ciliated epithelium of the bronchioles.

What histological components characterize mid-sized bronchioles?

Ciliated columnar epithelium, smooth muscle associated with abundant elastic fibers, connective tissue, and abundant lymphocytes of MALT with numerous lymphoid nodules.

What characterizes the epithelial lining and muscle layer of smaller bronchioles?

Ciliated simple cuboidal epithelium, prominent layers of smooth muscle, and abundant MALT.

What epithelium lines terminal bronchioles, and what is the prominent specialized exocrine cell type?

Simple cuboidal epithelium containing Club cells with dome-shaped apical domains and secretory granules.

What are the three major functions of bronchial exocrine Club cells?

1) Secretion of surfactant lipoproteins and mucins; 2) detoxification of inhaled xenobiotic compounds by SER enzymes; 3) secretion of antimicrobial peptides and cytokines.

Which epithelial cells besides Club cells and ciliated cells are found in terminal bronchioles?

Brush cells, DNES small granular cells, and stem cells.

What histological feature marks the transition from terminal bronchioles to respiratory bronchioles?

The appearance of outpouching alveoli in their walls, marking the first part of the respiratory portion.

How do Club cell and ciliated cell numbers change distally along respiratory bronchioles?

Club cells become more numerous distally as the number of ciliated cells decreases.

What type of epithelial cells are found directly at the alveolar openings of respiratory bronchioles?

Squamous cells.

What epithelium lines alveolar ducts and what supports each alveolar opening along the duct?

Squamous epithelium lines the duct, and a thin lamina propria with a strand of smooth muscle rings the opening of each alveolus.

What defines an alveolar sac?

The terminal space at the end of an alveolar duct where clusters of alveoli open into a common central space.

What connective tissue fibers support the thin lamina propria of alveolar sacs?

Elastic fibers and reticular fibers.

What are the diameter, count per lung, and total internal surface area of alveoli as given in the lecture?

A diameter of about $200\,\text{nm}$, approximately $200\text{ million}$ alveoli per lung, and a total internal surface area of $75\,\text{m}^2$.

What elements compose the interalveolar septa separating adjacent alveoli?

Scattered fibroblasts, a sparse extracellular matrix of elastic and reticular fibers, and a rich network of continuous capillaries.

What openings connect adjacent alveoli through the interalveolar septum?

Alveolar pores.

What three structural layers constitute the respiratory membrane (blood-air barrier)?

1) Alveolar epithelium (Type I cell cytoplasm); 2) fused basement membranes of the alveolar epithelium and capillary endothelium; 3) capillary endothelium.

What percentage of the alveolar surface is lined by Type I pneumocytes, and how thick is their gas-exchange cytoplasm?

They line $95\%$ of the alveolar surface, and their cytoplasm committed to the blood-air barrier is only $25\,\text{nm}$ thick.

Which intercellular junctions join Type I alveolar cells, and what is their role?

Desmosomes and tight junctions; tight junctions prevent leakage of interstitial fluid into the alveolar lumen.

Where are organelles positioned in Type I pneumocytes, and what endocytic structure is abundant in their cytoplasm?

Organelles are concentrated perinuclearly, and the attenuated cytoplasm contains numerous pinocytic vesicles.

What percentage of the alveolar lining is made up of Type II pneumocytes, and what is their cell shape?

They constitute $5\%$ of the alveolar lining and are cuboidal cells interspersed among Type I pneumocytes.

What are lamellar bodies in Type II alveolar cells?

Membrane-bound secretory vesicles containing stacked parallel membrane lamellae composed of lipids, phospholipids, and proteins.

What substance is secreted by Type II pneumocytes, and what cells clear it continuously from the alveoli?

Pulmonary surfactant; it is continuously removed by Type I pneumocytes, Type II pneumocytes, and alveolar macrophages.

What are dust cells, where are they situated, and what is their appearance relative to Type II pneumocytes?

They are alveolar macrophages located in alveolar lumens and interalveolar septa, appearing slightly darker than Type II pneumocytes.

What are the anatomical attachments of the visceral and parietal pleura?

Visceral pleura is attached directly to lung tissue, and parietal pleura lines the inner thoracic wall; both become continuous at the hilum.

What is the histological composition of the pleural membranes?

A surface mesothelium (specialized simple squamous epithelium) supported by loose connective tissue containing collagen and elastic fibers.

What is the pleural cavity?

The potential space between the visceral and parietal pleural layers.

With which fibers in the lung parenchyma are the elastic fibers of the visceral pleura continuous?

They are continuous with the elastic fibers of the underlying lung tissue.

What musculoskeletal support is present in the vestibules of the nasal cavities?

Hyaline cartilage.

What skeletal tissues support most areas of the nasal cavity?

Bone and hyaline cartilage.

Which cranial bone provides skeletal support to the superior olfactory region of the nasal cavities?

The ethmoid bone.

What musculoskeletal support elements are present in the nasopharynx and posterior oropharynx?

Bone and skeletal muscle.

What are the two major functional roles of the larynx outlined in the summary table?

It serves as the site for phonation and provides airway closure by the epiglottis during swallowing.

Which cell type disappears first along the bronchial tree: goblet cells or ciliated cells?

Goblet cells disappear first (absent by the terminal bronchioles), whereas ciliated cells extend further into the respiratory bronchioles.

How does the distribution of elastic fibers change from the trachea to the alveoli?

Elastic fibers remain continuously present throughout the entire conducting and respiratory tree down to the alveoli.

In this histological section of the epiglottis, what central supportive structure is labeled between the pharyngeal side (Ph) and laryngeal side (La)?

The elastic cartilage core of the epiglottis ($\text{Ep}$).

In this anatomical diagram of the larynx, which large shield-shaped hyaline cartilage displays the laryngeal prominence (Adam's apple)?

The thyroid cartilage.

In this histological section, what structure is identified by non-keratinized stratified squamous epithelium overlying dense connective tissue and a vocal ligament?

A vocal fold (true vocal cord).

In this diagram of gas diffusion, what three-part structure mediates gas exchange between the capillary lumen and alveolar air?

The respiratory membrane (blood-air barrier), comprising alveolar epithelium, fused basement membranes, and capillary endothelium.

In this transmission electron micrograph of an alveolar wall cell, what cell type is identified by its lamellar bodies (L) and apical microvilli (M)?

A Type II alveolar cell (Type II pneumocyte / septal cell).