upper airway
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The respiratory system facilitates the exchange of gases between the air and the blood and between the blood and the body's cells.
The respiratory system helps us to smell things and create sound.
The five key functions of the respiratory system are:
Pulmonary ventilation, which is the process of inhaling and exhaling air.
Air is inhaled through the nasal and oral cavities and moves through the pharynx, larynx, and trachea into the lungs.
Changes in volume and air pressure in the lungs trigger pulmonary ventilation.
During normal inhalation, the diaphragm and external intercostal muscles contract and the ribcage elevates.
During normal exhalation, the muscles relax, the lungs become smaller, and air is expelled.
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Oxygen is exchanged for carbon dioxide waste through the process called external respiration.
This process takes place in microscopic sacs called alveoli.
Oxygen diffuses from the alveoli into pulmonary capillaries and binds to hemoglobin molecules in red blood cells.
Carbon dioxide from deoxygenated blood diffuses from the capillaries into the alveoli and is expelled through exhalation.
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The upper respiratory system consists of the nose and nasal cavity, the pharynx, and the larynx.
These structures allow us to breathe and speak.
They warm and clean the air we inhale.
Mucous membranes lining upper respiratory structures trap foreign particles before the air travels down to the lungs.
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The nasal cavities are chambers of the internal nose.
Nostrils create openings to the outside world.
Air is inhaled through the nostrils and warmed as it moves further into the nasal cavities.
Nasal conchae, scroll-shaped bones, protrude and form spaces through which the air passes.
The conchae swirl the air around to humidify, warm, and clean it before it enters the lungs.
Epithelial cilia and a mucous membrane line the inside of the cavities, trapping unwanted particles.
Filtered, warmed air passes out of the back of the nasal cavities into the nasopharynx.
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Paranasal sinuses are air-filled cavities found inside bones of the skull.
There are four paired sinuses: frontal, ethmoidal, sphenoidal, and maxillary.
Mucosae line the paranasal sinuses and help to warm and humidify the air we inhale.
Mucus formed by the mucosae drains into the nasal cavities when air enters the sinuses.
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The pharynx conducts air between the larynx and trachea and the nasal and oral cavities.
The pharynx includes three regions: nasopharynx, oropharynx, and laryngopharynx.
The nasopharynx serves only as a passageway for air.
The oropharynx lies posterior to the oral cavity and contains the palatine tonsils.
Both air and ingested food pass through the oropharynx and laryngopharynx.
The laryngopharynx lies posterior to the epiglottis and connects to the larynx and the esophagus.
The epiglottis stays up during breathing, allowing air to pass freely between the laryngopharynx and the larynx.
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The larynx connects the lower part of the pharynx, the laryngopharynx, to the trachea.
It keeps the air passages open during breathing and digestion and is the key organ for producing sound.
The larynx is comprised of nine cartilages, including the epiglottis.
The epiglottis closes like a trap door as we swallow, steering food down the esophagus and away from the windpipe.
Inside the larynx are the vocal folds, which vibrate when air passes through them, producing sound.
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Phonation is the creation of sound by structures in the upper respiratory tract.
During exhalation, air passes from the lungs through the larynx.
Muscles in the larynx move the arytenoid cartilages, which push the vocal cords together.
When the vocal cords are pushed together, air passing between them makes them vibrate, creating sound.
Greater tension in the vocal cords creates higher-pitched sounds, while lesser tension creates lower-pitched sounds.
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The hyoid bone is located just under the chin and is important for respiratory and digestive processes.
It is the only bone in the body that doesn't touch another bone.
The hyoid is attached to the tongue and helps with swallowing at the start of digestion.
Structures that produce sound in the respiratory system depend on the hyoid.
The body and greater horns of the bone serve as attachment points for neck muscles that raise and lower the larynx during speech and swallowing.
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The process of olfaction begins with olfactory fibers in the nasal cavities.
Chemicals in the air bind to and activate nervous system receptors on the cilia.
This stimulus sends a signal to the brain through the ethmoid bone and olfactory bulbs.
The signal then travels from the olfactory bulbs, along cranial nerve 1, to the olfactory area of the cerebral cortex.
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The upper airway is structurally divided into the nose, nasal cavity, pharynx, and larynx.
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The lower airway consists of the larynx, trachea, bronchioles, lungs, bronchi, and alveoli.
The larynx is a hollow tube that allows air to pass from the throat to the trachea and contains the vocal cords.
The trachea is a long, U-shaped tube that connects the larynx to the lungs.
Bronchioles are the gas-exchanging units of the lung.
Lungs are spongy, air-filled organs that bring oxygen into the body and remove carbon dioxide.
Bronchi are the passage ways that connect the windpipe to the lungs.
Alveoli are tiny air sacs where gas exchange takes place.
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The conducting zone includes the nose, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and respiratory bronchioles.
These structures transport, cleanse, warm, and humidify incoming air but are not involved in gas exchange.
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The respiratory alveolar ducts zone functions in gas exchange through the alveoli.
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The functions of the respiratory system are:
Oxygen supplier.
Elimination of carbon dioxide.
Gas exchange between the blood and the external environment.
Passageways for air to reach the lungs.
Purification, humidification, and warming of incoming air.
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The upper airway functions include heating or cooling inspired gases, filtering inspired gases, humidifying inspired gases, olfaction, phonation, and conduction.
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The nose is a rigid structure of cartilage and bone.
It is divided into three regions: vestibular, olfactory, and respiratory.
The nostrils are the external openings of the nose.
The nasal fossa contains nasal hairs and sebaceous glands.
The pharynx is a hollow muscular structure that produces vowel sounds and serves as a common passageway for ventilatory gases, food, and liquid.
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The pharynx is lined with epithelium and has major functions in producing vowel sounds and serving as a common passageway.
The pharynx is about 5 inches long and extends from the internal nares to the esophagus.
The sections of the pharynx are the nasopharynx, oropharynx, and laryngopharynx.
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Nostrils:
Air enters the nose through the nostrils or nares.
Nasal cavity:
The interior of the nose is divided by a midline nasal septum.
Olfactory receptors:
Olfactory receptors for the sense of smell are located in the mucosa in the superior part of the nasal cavity, beneath the ethmoid bone.
Respiratory mucosa:
The rest of the mucosal lining, called the respiratory mucosa, warms the air as it flows past.
Mucus:
Sticky mucus produced by the mucosa's glands moistens the air and traps incoming bacteria and debris.
Ciliated cells:
Ciliated cells in the nasal mucosa move contaminated mucus towards the throat, where it is swallowed and digested.
Conchae:
The lateral walls of the nasal cavity have three mucosa-covered projections called conchae, which increase the surface area of the mucosa exposed to the air and increase air turbulence.
Palate:
The nasal cavity is separated from the oral cavity by the palate, with the anterior part supported by bone called the hard palate and the posterior part called the soft palate.
Paranasal sinuses:
The nasal cavity is surrounded by paranasal sinuses located in the frontal, sphenoid, ethmoid, and maxillary bones, which lighten the skull and act as a resonance chamber for speech.
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Larynx:
The larynx or voice box routes air and food into the proper channels and plays a role in speech.
Structure:
The larynx is formed by eight rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage called the epiglottis.
Thyroid cartilage:
The largest hyaline cartilage in the larynx is the shield-shaped thyroid cartilage, commonly known as Adam's apple.
Epiglottis:
The epiglottis protects the superior opening of the larynx and is sometimes referred to as the "guardian of the airways."
Vocal folds:
The mucous membrane of the larynx forms a pair of folds called the vocal folds or true vocal cords, which vibrate with expelled air and allow us to speak.
Glottis:
The slit-like passageway between the vocal folds is called the glottis.
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Trachea:
Air entering the trachea from the larynx travels down its length to the level of the fifth thoracic vertebra, approximately midchest.
Structure:
The trachea has walls reinforced with C-shaped rings of hyaline cartilage, which keep it open despite pressure changes during breathing.
Cilia:
The trachea is lined with ciliated mucosa that continuously beat in the opposite direction of incoming air, propelling mucus loaded with dust particles and debris away from the lungs.
Main bronchi:
The right and left main bronchi are formed by the division of the trachea.
Location:
Each main bronchus runs obliquely before plunging into the medial depression of the lung on its own side.
Size:
The right main bronchus is wider, shorter, and straight