Anatomy of Alveoli and Lungs

Study Notes

Alveoli are small, grapelike clusters found at the end of each bronchiole, also known as air sacs
They are responsible for the exchange of oxygen and carbon dioxide
Each lung contains millions of alveoli

The lungs are the essential organs of respiration, located in the thoracic cavity
The right lung has three lobes: superior, middle, and inferior
The left lung has two lobes: superior and inferior, and is slightly smaller than the right lung due to the space taken up by the heart

The pleura is a thin, moist, and slippery membrane that covers the outer surface of the lungs

Respiration is the exchange of oxygen and carbon dioxide that is essential to life
A single respiration consists of one inhalation and one exhalation
Inhalation occurs when the diaphragm contracts and pulls downward, causing the thoracic cavity to expand and drawing air into the lungs
Exhalation occurs when the diaphragm relaxes, moving upward and causing the thoracic cavity to become narrower, forcing air out of the lungs
Respiratory rate is the number of breaths taken in one minute, with a normal rate in healthy adults being roughly 12 to 20 breaths per minute

The nasal cavity is the main route of air entry
The nostrils are the external openings of the nose
The nasal septum is a wall of cartilage that divides the nose into two equal sections
Cilia filter incoming air to remove debris
Olfactory receptors are nerve endings that act as the receptors for the sense of smell
Mucous membranes line the nose and produce mucus to moisten, warm, and filter the air as it enters

Air-filled cavities lined with mucous membrane, located in the bones of the skull
There are four nasal sinuses: maxillary, frontal, sphenoidal, and ethmoidal
Functions of the sinuses include making the bones of the skull lighter, producing sound, and producing mucus to provide lubrication for the tissues of the nasal cavity

The pharynx receives air after it passes through the nose or mouth, as well as food
It is divided into three regions: nasopharynx, oropharynx, and laryngopharynx
The nasopharynx is used only by the respiratory system for the transport of air and opens into the oropharynx
The oropharynx is shared by the respiratory and digestive systems and transports air, food, and fluids downward to the laryngopharynx
The laryngopharynx is shared by both the respiratory and digestive systems and continues downward to the openings of the esophagus and trachea

The larynx is a triangular chamber located between the pharynx and the trachea
It contains the vocal cords
During breathing, the cords are separated to let air pass
During speech, they close together, causing the cords to vibrate against each other and produce sound as air is expelled from the lungs

The trachea is the tube located directly in front of the esophagus that extends from the neck to the chest
The trachea divides into two primary bronchi, which then divide and subdivide into smaller bronchioles within the lung