Respiratory System in Pharmacy

Study Notes

The respiratory system is a complex of organs and tissues that exchange blood carbon dioxide (CO2) with air oxygen (O2).
Function: Act of breathing, which includes inhaling and exhaling air in the body; the absorption of oxygen from the air to produce energy; the discharge of carbon dioxide, which is the byproduct of the process.

The conducting airways: serve to conduct, clean, warm, and moisten the air; composed of the nose, pharynx, larynx, trachea, bronchi, and bronchioles.
The respiratory airways: facilitate gas exchange; located entirely within the lung and are represented by respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

Goblet (Mucous) Cells: present in the trachea and bronchi; contribute to mucous secretion lining the airways.
Basal (Short) Cells: found in the trachea and bronchi; do not reach the airway lumen and have nuclei close to the basal lamina, giving the epithelium a pseudostratified appearance.
Clara Cells (Bronchiolar Epithelial Cell): non-ciliated columnar epithelial cells found in bronchioles; play a major role in the metabolism of exogenous agents and act as progenitor cells for bronchiolar epithelium following lung injury.
Brush Cells: non-ciliated columnar cells found in trachea and bronchi; have a dense population of long, straight, blunt microvilli on the luminal surface and epithelioidendritic (afferent) synapses near the cell base; function is unknown, but suspected to be chemoreceptor and sensory.
Dense Core Granule Cells (Small Granule Cell, Neuroendocrine Cell): found throughout the airways; resemble endocrine cells; secrete a variety of amine and peptide products; role in regulating lung function is incompletely understood.
Serous Cells: non-ciliated secretory cells found predominantly in the trachea and bronchi; secrete glycoproteins and lysozymes; contribute to the low viscosity periciliary fluid covering the bronchial epithelium.
Intermediate Cells: non-ciliated columnar cells that are immature and replace cells cast off from the epithelium; may differentiate into mucous secreting Goblet cells or ciliated cells.

Functions: phonation (creation of sounds for speech) and control of the air pathway so that only air reaches the lower respiratory passages.
During swallowing, the larynx moves upwards and directs the food to the oesophagus.
If anything other than air enters the larynx, there is a cough reflex to prevent fluids or food entering the trachea.

Consists of ciliated epithelium, submucosal glands, and goblet cells that secrete serous and mucinous secretions.
Function: trap and expel debris that has been inhaled.
Particles above 10 microns in size do not get past the nasopharynx; particles averaging 5 to 10 microns are trapped by the mucociliary apparatus; particles 1 to 5 microns in size must be phagocytosed by macrophages in the alveoli; particles less than 1 micron remain suspended and are exhaled.

The lungs are covered by a thin tissue layer called the pleura.
The same kind of thin tissue lines the inside of the chest cavity.
A thin layer of fluid acts as a lubricant, allowing the lungs to slip smoothly as they expand and contract with each breath.