12.02.11+-+Respiratory+System

12.02.11 - Respiratory System

Air conduction, air filtration, gas exchange. also augments speech and smell and has endocrine activity. Thoracic cage, intercostal muscles, and thoracic diaphragm augment air ventilation. thoracic cage moves outward and upward and diaphragm descends down, drawing air in lungs.
 * 1. Identify functions of the respiratory system. Name the structures that augment the ventilation process and how they work.**

nasal cavities, nasopharynx, oropharynx, larynx, trachea, bronchi, and most bronchioles
 * 2. Identify the conducting parts of the respiratory system.**

trachea, primary bronchus, secondary bronchi to bronchiole (<1mm), terminal bronchiole, respiratory bronchiole, alveolar duct, alveolar sac
 * 3. Name and describe the branches of the bronchial tree.**

ciliated columnar cell Goblet Cell Brush Cell Small Granule Cell Basal Cell
 * 4. Describe the structure and function(s) of cells forming respiratory epithelium.**
 * structure: extends full thickness of epithelium. 250 motile cilia at apical surface with ciliary basal bodies forming a dark line.
 * function: coordinating sweeping of clia removes mucus and debris toward pharynx
 * structure: extends full epithelial thickness, lacks cilia
 * function: produces mucin, a glycoprotein that hydrates to mucus. Mucus traps particulate matter and moistens the luminal surface.
 * structure: columnar brush cell with blunt microvilli covering apical surface
 * function: basal surface makes contact with afferent nerve endings - receptor cell
 * structure: small round granule sparsely scattered near basement membrane. Some are innervated
 * function: produce membrane bound dense granules containing serotonin, calcitonin, gastrin-releasing peptide or catecholamine. These are enteroendocrine (APUD) cells. (Kulchitsky cells)
 * structure: small round cell near basal lamina
 * function: reserve cell population that replaces all the other epithelial cell types


 * 5. Describe the structure and function of the larynx, trachea and bronchi.**

Larynx: the larynx is a complex space between the oropharynx and the trachea. It includes the oral surface of the epiglottis and the vestibular and vocal folds. The epithelial layer is formed by respiratory epithelium (Silly Brushes Gobble Small Bases) except for at the places of friction (the vocal folds and oral surface of the epiglottis). The lamina propria contains lots of cartilage (epiglottis, thyroid, cricoid, arytenoid, cuneiform, and cuniculate) and glands (serous and mucous, except for in the vocal folds). The larynx has 4 functions: phonation, airway protection, cough reflex and valve to protect airway.

Trachea: the tube connecting the larynx to the bronchi. Formed of the same mucosa (respiratory epithelium and lamina propria), the same submucosa (with glands and cartilage) and the same adventitial (loose CT) layers. The cartilage is C-shaped.

Bronchi: the trachea branches into a series of smaller cartilage lined tubes called bronchi. Formed of the same mucosa (respiratory epithelium and lamina propria) surrounded by a hodge-podge of glands, cartilage, smooth muscle tissue, and connective tissue. The submucosa and adventitia blur together.


 * 6. Compare and contrast structure and function of the vestibular and vocal folds.**

The vestibular folds are covered by respiratory epithelium. The vocal folds are covered by stratified squamous epithelium.

The vestibular folds have serous and mucous glands in their lamina propria. The vocal folds do not have serous or mucous glands in their lamina propria.

The vestibular folds overhang the vocal folds, but are not active in phonation. The vocal folds are active in phonation.


 * 7. Describe the structure and function of the bronchioles.**

Bronchioles are roughly divided into 4 types based on their structure and function. Smooth muscle and elastic fibers are present in decreasing amounts in all 4 types:

Large: have a few goblet cells interspersed in respiratory epithelium (ciliated pseudo stratified columnar epithelium) Small: the epithelium has switched to ciliated simple columnar Terminal: the epithelial layer is now ciliated simple cuboidal and a new domed lipoprotein secreting cell type shows up: Clara cells Respiratory: the lumen wall now is still composed of ciliated cuboidal epithelium broken by respiratory alveoli lined with simple squamous epithelium


 * 8. Compare and contrast structure and function of respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli. Describe structure and function of Clara cells.**

The respiratory portion of the respiratory system is also composed of 4 structure types. They don't have a ton of features common to all four structures:

Respiratory bronchiole: lumen wall composed of ciliated cuboidal epithelium and clara; broken by alveoli outpocketings; smooth muscle and elastic fibers present in submucosa/adventitia Alveolar ducts: lumen wall composed of simple squamous epithelium (no Clara); the ducts join in knobs that contain smooth muscle cells Alveolar sacs: lumen wall composed of attenuated simple squamous epithelium; termination of ducts; no smooth muscle Alveoli: lumen wall composed of two cell types: type I and type II (clever, right?); no smooth muscle fibers


 * 9. Describe the structure and function of the alveolus, types I and II alveolar cells and the alveolar macrophage.**

Alveolus: Type I alveolar cells: Type II alveolar cells: Alveolar Macrophage (Dust Cell):
 * Structure: lumen wall composed of two cell types: type I and type II (clever, right?); no smooth muscle fibers. Divided by septa composed of CT, capillaries, and leukocytes.
 * Function: Gas exchange
 * Structure: attenuated simple squamous epithelium joined together by zonula occludes (tight junctions)
 * Function: Gas exchange barrier and pinocytotic turnover of surfactant
 * structure: round small cells at junctions of alveoli septa. Only cover 3% of surface, but compose 40% of lung alveolar cells
 * function: stem cells for Type I and II; produce lamellar bodies which secrete surfactant through plasma membrane
 * Structure: darkly granulated, spindles, dispersed throughout lumen and interstitium
 * Function: phagocytose


 * 10. Describe the structure and function of the alveolar endothelial cell.**

Alveolar endothelial cell:
 * Structure: these are the cells on the opposite side of the intersitium. The Type I cells are on the alveoli side. The endothelial cells are on the capillary side. Share a basement membrane (the interstitium) with the alveolar cells. Pinocytotically active for gas exchange. Lots of vesicles.
 * Function: Gas exchange: lots of pinocytosis. Endothelial cells are also the cell type that produces the protease Angiotensin Converting Enzyme (ACE), the enzyme that converts Angiotensin I into Angiotensin II. That causes the increased uptake of Na+ in the kidneys and the retention of water, increasing blood volume/pressure.


 * 11. Describe the elements that compose the blood-gas diffusion barrier.**

Three layers:
 * Type I Alveolar Cells
 * Interstitium
 * Alveolar Endothelial Cells

The lungs have two blood sources, one oxygenated (bronchial), the other deoxygenated (pulmonary).
 * 12. Describe pulmonary and bronchial blood supplies.**


 * The pulmonary blood supply enters the lung at the hilum as the pulmonary artery and follows the bronchi through its branching until the three respiratory units. At the alveolar ducts, it branches into a web of capillaries to facilitate gas exchange. The capillaries then reform into pulmonary venules and return to the heart via pulmonary veins.
 * The bronchial blood supply nutrients. They either branch from the aorta or the intercostals and also follow bronchi branching patterns. They enter the same capillary bed of the lungs, providing nutrients, but there are no specific bronchial veins. The blood exits via the pulmonary veins.