What are the two functional portions of the respiratory system?
Conducting portion and Respiratory portion.
What are the components of the conducting portion?
Nasal cavity, mouth, nasopharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles.
What are the main functions of the conducting portion?
To warm, moisten, and filter the air before it reaches the respiratory portion.
What are the components of the respiratory portion?
Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.
Into which three regions is the nasal cavity divided?
Vestibular region, Respiratory region, and Olfactory region.
What is the anterior part of the nasal cavity called?
The Vestibular region.
What type of epithelium lines the anterior vestibular region?
Keratinized stratified squamous epithelium (thin skin).
What structures are found in the vestibular region to filter dust?
Hair follicles (Vibrisae) and sweat glands.
What lines the posterior part of the vestibular region?
Non-keratinized stratified squamous epithelium.
What epithelium covers the Respiratory region of the nasal cavity?
Pseudostratified ciliated columnar epithelium with goblet cells (respiratory epithelium).
What type of epithelium is found in the Olfactory region?
Olfactory epithelium (sensory epithelium for smelling).
Where is the respiratory region located in relation to the vestibule?
It is posterior to the vestibule.
What is the name of the loose connective tissue underneath the respiratory epithelium?
Lamina propria.
What does the lamina propria of the respiratory region contain?
Mucous and serous glands, blood vessels, and lymphatic vessels.
What are "swell bodies"?
Extensive venous plexuses (erectile tissue) in the lamina propria.
Where are swell bodies specifically prominent?
On the inferior turbinates and the nasal septum.
What are the five main cell types in respiratory epithelium?
Ciliated cells, Goblet cells, Brush cells, DNES cells, and Basal (short) cells.
Describe the structure and function of ciliated cells.
Columnar cells with motile cilia that beat toward the mouth.
What is the function of mature goblet cells?
They secrete mucinogen droplets to trap inhaled particles.
What are Brush cells?
Columnar cells with blunt microvilli on their apical surfaces.
What is the functional role of Brush cells?
They act as chemosensory receptors.
What does DNES stand for?
Diffuse Neuroendocrine Cells.
What is the function of DNES cells?
They synthesize different polypeptide hormones.
What is the role of Basal (short) cells?
They rest on the basal lamina and act as stem cells to divide and replace other cells.
How does the thickness of respiratory epithelium compare to olfactory epithelium?
Respiratory epithelium is thinner, while olfactory epithelium is significantly thicker (60-100 μm).
What is the difference between the cilia of respiratory and olfactory regions?
Respiratory region has motile cilia; Olfactory region has non-motile cilia (odorant receptors).
What are the four bones containing paranasal sinuses?
Frontal, maxillary, ethmoid, and sphenoid bones.
What epithelium lines the paranasal sinuses?
A thinner respiratory epithelium with few goblet cells.
What is unique about the lamina propria of paranasal sinuses?
It contains few small glands and is continuous with the periosteum.
How does mucus drain from the paranasal sinuses into the nasal cavity?
Through small openings via the activity of ciliated epithelial cells.
What structure connects the pharynx with the trachea?
The Larynx.
What parts of the larynx are NOT lined by respiratory epithelium?
The vocal cords and the anterior surface of the epiglottis.
What epithelium covers the vocal cords?
Stratified squamous epithelium.
What types of cartilage support the laryngeal wall?
Hyaline and elastic cartilages.
Which laryngeal cartilages are composed of hyaline cartilage?
Thyroid, cricoid, and most of the arytenoids.
Which laryngeal cartilages are composed of elastic cartilage?
Epiglottis, cuneiform, corniculate, and the tips of the arytenoids.
What is the characteristic shape of tracheal cartilage?
C-shape.
How many hyaline cartilage rings are typically in the trachea?
16 to 20 rings.
What are the four layers of the tracheal wall?
1. Mucosa, 2. Submucosa, 3. Cartilaginous coat, 4. Adventitia (Fibrosa).
What is found in the tracheal submucosa?
Loose connective tissue, tracheal glands (mucous and serous), and lymphoid follicles.
What joins the open ends of the C-shaped tracheal cartilage?
The trachealis muscle (smooth muscle).
What is the outermost layer of the trachea made of?
Connective tissue (Adventitia/Fibrosa).
What are extrapulmonary bronchi?
Bronchi located outside of the lung tissue.
How does the histology of extrapulmonary bronchi compare to the trachea?
Their structure is similar to that of the trachea.
What characterizes intrapulmonary bronchi?
They are inside the lung and contain plates of hyaline cartilage instead of C-shaped rings.
What does BALT stand for in the context of bronchi?
Bronchial Associated Lymphatic Tissue.
What layers are present in the intrapulmonary bronchi?
Respiratory epithelium, smooth muscle, glands, and hyaline cartilage plates.
What are the three layers of the bronchiole wall?
Mucosa, Musculosa (smooth muscle), and Fibrosa (connective tissue).
What is the maximum diameter of a bronchiole?
Less than 5 mm.
Do bronchioles contain cartilage?
No, cartilage is replaced by smooth muscle.
Do bronchioles contain glands?
No.
Do small bronchioles have goblet cells?
What epithelium lines large bronchioles?
Simple columnar ciliated epithelium with Clara cells.
What is the recent name for Clara cells?
Club cells.
What epithelium lines small bronchioles?
Simple cuboidal (non-ciliated) epithelium alternating with Clara cells.
What are terminal bronchioles?
The last part of the conducting portion.
Do terminal bronchioles have a respiratory function?
No, there is no gas exchange.
What lines the terminal bronchioles?
Partially ciliated simple columnar epithelium containing Clara cells.
What do Clara cells secrete?
A solution similar in composition to pulmonary surfactant.
What is the first part of the respiratory portion?
Respiratory bronchioles.
What is the diameter of a respiratory bronchiole?
0.5 mm.
Do respiratory bronchioles allow gas exchange?
Yes.
What epithelium lines respiratory bronchioles?
Simple cuboidal epithelium.
What are alveolar ducts?
Terminal branches of respiratory bronchioles.
What lines alveolar ducts?
Simple cuboidal cells.
Where do alveolar sacs and alveoli open?
Into the walls of alveolar ducts.
How does asthma affect the bronchioles?
Contraction of smooth muscle decreases diameter, leading to difficult expiration and mucus accumulation.
How is asthma treated histologically?
With drugs that relax bronchiolar smooth muscle and dilate air passages.
What are the structural and functional units of the respiratory system?
Alveoli.
What type of capillaries are in contact with the alveolar walls?
Pulmonary capillaries.
What is "external respiration"?
Gas exchange between air in the alveoli and RBCs in blood capillaries.
What can alveoli open into?
Alveolar sacs, alveolar ducts, or respiratory bronchioles.
How many types of cells make up the alveolar epithelium?
Two types: Type I and Type II pneumocytes.
Which cell type forms the majority of the alveolar surface?
Type I pneumocytes.
What is the shape of Type I pneumocytes?
Simple squamous flat cells.
What happens to the basal lamina of Type I pneumocytes?
It fuses with the basal lamina of nearby pulmonary capillaries.
What is the shape of Type II pneumocytes?
Rounded or cuboidal cells.
What is the primary function of Type II pneumocytes?
They are secretory cells that produce surfactant.
What is the function of surfactant?
It reduces surface tension within all alveoli.
What forces does surfactant use to reduce surface tension?
Hydrophilic and hydrophobic forces.
What is atelectasis?
Collapse of part or all of the lung.
What causes atelectasis in the context of pneumocytes?
Insufficient pulmonary surfactant in the alveoli.
What is the air-blood barrier?
The structure that separates air in the alveolar lumens from RBCs in capillaries.
What is the first layer of the air-blood barrier (from the air side)?
Surfactant.
What is the second layer of the air-blood barrier?
Type I pneumocyte.
What is the third layer of the air-blood barrier?
Type I pneumocyte basement membrane.
What is the fourth layer of the air-blood barrier?
Basement membrane of blood capillary endothelium.
What is the fifth layer of the air-blood barrier?
Endothelium of blood capillary.
Which layers of the air-blood barrier are fused?
The basement membranes of the Type I pneumocyte and the capillary endothelium.
What are "dust cells"?
Alveolar macrophages.
Where are dust cells located?
In the alveoli or in the interalveolar septa.
What do the septa between alveoli contain?
Several cell types, including capillaries (with erythrocytes and leukocytes) and macrophages.
What is the purpose of the interalveolar septum?
It is the wall between two adjacent alveoli.
Which cells line almost the entire alveolar surface for gas exchange?
Type I alveolar cells.
How do Type II cells appear in a histological section?
Large, rounded cells, often bulging into the alveolus.
What is the function of the trachealis muscle?
To join the ends of the tracheal C-shaped cartilage.
What is the main histological difference between bronchi and bronchioles?
Bronchi have cartilage and glands; bronchioles have neither.
What lines the olfactory region specifically to detect smells?
Bipolar neurons (primary cell type).
What are sustentacular cells?
Supporting cells found in the olfactory region.
What is the approximate thickness of the air-blood barrier?
0.1 to 1.5 μm.
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