Respiratory System

trachea

A C-shaped structure attached inferiorly to the larynx by the cricoid cartilage that connects the pharynx and larynx to the lungs, allowing the passage of air. It is lined with ciliated, mucous membrane. The cilia sweep debris craniad towards the pharynx.

uvula

A conic projection from the posterior edge of the middle of the soft palate, composed of connective tissue and some muscular fibers. Involved in speech formation, coughing, and swallowing. Associated with vagus nerve.

epiglottis

A flap made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. It stands open during breathing, allowing air into the larynx. During swallowing, it closes to prevent aspiration, forcing the swallowed liquids or food to go down the esophagus instead. It is thus the valve that diverts passage to either the trachea or the esophagus.

surfactant

A lipoprotein that lowers the surface tension in the alveoli, reduces the amount of pressure needed to inflate the alveoli, and decreases the tendency of the alveoli to collapse.

nasal concha (turbinates)

A long, narrow, curled shelf of laminar bone that protrudes into the nasal cavity. They divide the nasal airway into 4 groove-like air passages, and are responsible for forcing inhaled air to flow in a steady, regular pattern around the largest possible surface area of nasal mucosa. Superior, middle, and inferior, on each side of the septum.

palatine tonsils

A mass of lymphatic tissue situated on the left and right sides at the back of the pharynx.

adenoid tonsils

A mass of lymphatic tissue situated posterior to the nasal cavity in the roof of the nasopharynx. Also known as a pharyngeal tonsil, it is the superior-most of the tonsils.

tongue

A muscular organ on the floor of the mouth that manipulates food for mastication. It is the primary organ of taste and phonetic articulation.

corniculate cartilages

A pair of horn-like pieces of elastic cartilage located at the apex of each arytenoid cartilage.

arytenoid cartilages

A pair of small three-sided pyramids which form part of the larynx, to which the vocal cords are attached. These allow and aid in the vocal cords' movement. An important landmark in intubation.

cuneiform cartilages

A pair of wedge-shaped elastic cartilages anterior to the corniculate cartilages that support the vocal cords and lateral aspects of the epiglottis.

Alpha-1 antitrypsin (A1AT)

A protease inhibitor that protects tissues from enzymes of inflammatory cells.

alveolus (alveoli)

A spherical structure found in the lungs at the terminal ends of the respiratory tree. CO2 rich blood is pumped from the rest of the body into the alveolar blood vessels where, through diffusion, it releases its CO2 and absorbs O2. Elastin fibers allow the alveoli to expand.

hard palate

A thin horizontal bony plate of the skull, located in the roof of the mouth. Important for feeding and speech. Contains palatine rugae.

mesothelium (mesothelial membrane)

A thin, clear, tough membrane that forms the lining of several body cavities: the pleura (thoracic cavity), peritoneum (abdominal cavity including the mesentery), mediastinum and pericardium (heart sac). It produces a lubricating fluid that is released between layers, providing a slippery, non-adhesive, and protective surface to facilitate movement.

pleural fluid

Acts as a lubricant between the lung and chest wall.

larynx

An organ that is a collection of structures that make up the voice box including the thyroid cartilage and vocal cords. It is involved in breathing, sound production, and protecting the trachea against food aspiration.

respiratory bronchioles

At the ends of the terminal bronchioles, they are the narrowest airways of the lungs and contain a small number of alveoli. The start of the respiratory zone.

alveolar duct

Branches of the respiratory bronchioles that lead directly to the alveoli.

buffer formula

CO2 + H2O (Respiration), H2CO3 (carbonic acid, in the blood), H+ + HCO3- (bicarbonate, metabolic)

mucociliary elevator

Ciliated mucous lining of the trachea, bronchi, and bronchioles that sweeps foreign particles craniad to the pharynx and away from the lungs.

alveolar sac

Clusters of individual alveoli that share a common duct or opening.

conducting zone

Consists of a series of interconnecting cavities and tubes both outside and within the lungs that function to filter, warm, and moisten air and conduct it into the lungs. Includes everything from the nose through the terminal bronchioles.

respiratory zone

Consists of tissues within the lungs where gas exchange occurs, including the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

sphenoid sinus

Found deep within the skull behind the Ethmoid sinuses. They are a pair (left and right) of small cavities approximately the size of a large grape. They are separated by a thin plate of bone (septum).

palatine rugae

Irregular ridges in the mucous membrane of the hard palate that help facilitate the movement of food backwards towards the pharynx.

cricothyroid ligament (membrane)

It connects the front parts of the contiguous margins of the cricoid and thyroid cartilages. Its main purpose is to keep the cricoid and thyroid from traveling too far. It is cut during emergency cricothyrotomy.

mainstem bronchus

One of the two branches formed by division of the trachea after the carina. Right mainstem is larger than the left.

expiration (exhalation)

Passive action, relaxed state (under normal circumstances).

carina

Point at which the trachea bifurcates into the left and right mainstem bronchi. Loaded with lots of sensory nerves that can slow the heart if irritated.

glottis (glottic opening)

Potential space between the vocal cords. Divider between upper and lower airway and also sterile and non-sterile.

vallecula

Potential space between tongue and epiglottis.

Pores of Kohn

Present in the alveolar walls and permit airflow between adjacent alveoli preventing over-inflation (intra alveolar pores).

hilus (hilum)

The "root" of the lung. The only location where the lung is attached to the body. It includes the mainstem bronchus, bronchial veins/arteries, and pulmonary veins/arteries. It is located more posterior than anterior.

thyroid cartilage

The cartilage structure in and around the trachea that contains the larynx. It does not completely encircle the larynx. It protects the vocal cords and serves as an attachment for several muscles. "Adam's Apple"

laryngopharynx

The caudal part of the pharynx that is part of the throat that connects to the esophagus. It contains the epiglottis. It is a passageway for air and liquid/food.

nasal cavity

The cavity in the upper airway that contains the inferior turbinates and hard/soft palates. It is ciliated and contains mucus-producing membranes.

visceral pleura

The delicate serous (watery) membrane that covers the surface of each lung and dips into the fissures between the lobes.

Inspiration (inhalation)

The diaphragm contracts, moving down and creating space in the thoracic cavity for the lungs to expand. Several other muscles involved as well to expand the cavity in all directions. Expanding this cavity creates a vacuum for atmospheric air to enter the lungs.

oropharynx

The lower part of the pharynx that extends from the uvula to the level of the hyoid bone. It contains the base of the tongue and the vallecula. It is a passageway for air and liquid/food.

terminal bronchioles

The most distal segment of the conducting zone, branching off the lesser bronchioles. They further divide to form respiratory bronchioles which contain a small number of alveoli. They contain a limited number of ciliated cells.

nasal vestibule

The nasal opening and the first 4 mm of the nasal cavity, containing no mucus but many hairs. "Entrance way"

cricoid cartilage (cricoid ring)

The only complete ring of cartilage around the trachea. It forms the back part of the larynx and functions as an attachment site for muscles, cartilages, and ligaments involved in opening and closing the airway and in producing speech. Strongest structure in the airway.

parietal pleura

The outer membrane of the lung which is attached to the inner surface of the thoracic cavity. It also separates the pleural cavity from the mediastinum (central compartment of the thoracic cavity).

pharynx

The part of the throat situated immediately posterior to the nasal cavity, posterior to the mouth, and superior to the esophagus and larynx. It is divided into three sections: the nasopharynx, the oropharynx, and the laryngopharynx. It is important in vocalization and respiration.

partial carbon dioxide (pCO2)

The partial pressure of CO2 in arterial blood. It indicates the effectiveness of alveolar ventilation, given the diffusing capacity of the gas. It is a good indicator of respiratory function and reflects the amount of acid in the blood (without lactic acid). Its normal values are in the range 35-45 mmHg. Hyperventilation is less than 35 and Hypoventilation is greater than 45.

conducting bronchioles

The passageways by which air passes from the mainstem bronchi to the alveoli, in which branches no longer contain cartilage or glands in their submucosa. They are branches of the bronchi, and are part of the conducting zone of the respiratory system.

lungs

The primary organs of respiration located in the thoracic cavity that extract O2 from the atmosphere and transfer it into the bloodstream, and release CO2 from the bloodstream into the atmosphere, in a process of gas exchange. Right lung has 3 lobes and is larger than the 2-lobed left lung. They are enclosed within the pleural sac which allows the inner and outer walls to slide over each other during respiration with little friction.

pyriform fossa

The recess on either side of the laryngeal orifice that are involved in speech. They are the weakest part of the airway and can be pierced by an ET tube.

soft palate

The soft tissue constituting the back of the roof of the mouth. Consists of muscle fibers sheathed in mucous membrane. Continuous with the hard palate but distinguishable in that it does not contain bone. It is responsible for closing off the nasal passages during the act of swallowing, and also for closing off the airway.

pleural cavity

The thin fluid-filled space between the two pulmonary pleurae (visceral and parietal) of each lung.

nasopharynx

The upper portion of the pharynx that extends from the base of the skull to the upper surface of the soft palate. It includes the space between the internal nares and the soft palate and is separated from the oropharynx by the hard and soft palates.

pulmonary stretch receptors

They send impulses to the medulla oblongata giving information about the state of the lungs. When the lung expands, the receptors reduce the respiratory rate.

vocal cords (vocal folds)

Twin infoldings of mucous membrane stretched horizontally, posterior to anterior, across the larynx. They vibrate, modulating the flow of air being expelled from the lungs during phonation. They are controlled via the vagus nerve. Landmark for ET tube placement.

maxillary sinus

largest paranasal sinus; pyramidal; on cheek bone lateral to nasal bone

frontal sinus

sinus located in the anterior of the cranium