Respiratory System Overview

Study Notes

The respiratory system is responsible for breathing and gas exchange.
Four key processes: ventilation (breathing), oxygen and carbon dioxide exchange between the lungs and blood, transport of these gases in the blood, and exchange of gases between blood and tissues.
Other functions: regulation of blood pH, voice production, olfaction (sense of smell), and innate immunity.

The respiratory system is divided into upper and lower respiratory tracts:
- Upper respiratory tract: nose, pharynx, and larynx.
- Lower respiratory tract: trachea, bronchi, and lungs.
The nose consists of:
- External nose: the visible part, mostly composed of hyaline cartilage.
- Nasal cavity: extends from the nares (nostrils) to the choanae (openings into the pharynx).
- Nares: external openings of the nose.
- Choanae: openings into the pharynx.
- Nasal septum: divides the nasal cavity into right and left sections.
- Hard palate: floor of the nasal cavity, separating it from the oral cavity.
- Conchae: bony ridges on each side of the nasal cavity that increase surface area, causing air to swirl and be cleansed, humidified, and warmed.
- Paranasal sinuses: air-filled spaces in the skull that open into the nasal cavity. They resonate sound, reduce skull weight, produce mucus, and influence voice quality.
- Nasolacrimal ducts: carry tears from the eyes and open into the nasal cavity.

Air cleaning:
- Coarse hairs in the nares trap large particles.
- Mucus secreted by goblet cells traps smaller particles.
- Cilia move the debris-laden mucus towards the pharynx, where it is swallowed.
Air warming: blood vessels beneath the mucous epithelium warm the air.
Air humidifying: moisture from the mucous epithelium humidifies the air.

The sneeze reflex is a physiological response to foreign substances in the nasal cavity.
Sensory receptors in the superior part of the nasal cavity detect foreign substances.
These receptors initiate the sneeze reflex through action potentials.

Ventilation or breathing is the movement of air into and out of the lungs.
The exchange of oxygen (O2) and carbon dioxide (CO2) between the air in the lungs and the blood.
The transport of O2 and CO2 in the blood.
The exchange of O2 and CO2 between the blood and tissues.

The respiratory system is divided into the upper respiratory tract (nose, pharynx, and larynx) and the lower respiratory tract (trachea, bronchi, and lungs).
Nose: The external nose is the visible structure composed mainly of hyaline cartilage. The nasal cavity extends from the nares (nostrils) to the choanae (openings into the pharynx).
- Nares/Nostrils: External openings of the nose.
- Choanae: Openings into the pharynx.
- Nasal Septum: Partition dividing the nasal cavity into right and left parts.
- Hard Palate: Floor of the nasal cavity, separating it from the oral cavity.
- Conchae: Bony ridges on each side of the nasal cavity, increasing the surface area of the nasal cavity and causing air to churn in order to be cleansed, humidified, and warmed.
- Paranasal Sinuses: Air-filled spaces within bones that open into the nasal cavity. They function as resonating chambers, reduce the weight of the skull, produce mucus, and influence the quality of voice.
- Nasolacrimal Ducts: Carry tears from the eyes and open into the nasal cavity.

Coarse hairs inside the nares and mucus produced by goblet cells trap large particles.
Cilia sweep the debris-laden mucus towards the pharynx, where it is swallowed.
Air is warmed by blood vessels underlying the mucous epithelium and humidified by moisture.