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Upper respiratory tract
 
 
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The upper respiratory tract refers to the following parts of the respiratory system
Respiratory system

A respiratory system?s function is to allow gas exchange. The space between the alveoli and the capillaries, the anatomy or structure of the exchange system, and the precise physiological uses of the exchanged gases vary depending on the organism....
:



The upper respiratory tract begins with the nose
Nose

Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for Respiration in conjunction with the mouth....
 and oral cavity, and ends at the branching of the trachea into two bronchi. The upper respiratory tract is part of the conducting zone
Conducting zone

The conducting zone of the respiratory system is made up of the vertebrate trachea, bronchi, bronchioles, and terminal bronchioles. It is composed of the 1st through the 16th division of the respiratory tract....
.

Upper respiratory tract infections are amongst the most common infections in the world.

Role in Respiration
Unlike the trachea
Trachea

Trachea is a common term for 'Wind Pipe' an airway through which respiratory air passes in organisms. In vertebrates, it is held open by up to 20 C-shaped rings of cartilage....
 and bronchi, the upper airway is a collapsible, compliant tube.






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Encyclopedia


The upper respiratory tract refers to the following parts of the respiratory system
Respiratory system

A respiratory system?s function is to allow gas exchange. The space between the alveoli and the capillaries, the anatomy or structure of the exchange system, and the precise physiological uses of the exchanged gases vary depending on the organism....
:

  • nose
    Nose

    Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for Respiration in conjunction with the mouth....
     and paranasal sinuses
  • oral cavity (also part of the digestive system)
  • throat
    Throat

    In anatomy, the throat is the anterior part of the neck, in front of the vertebrae. It consists of the pharynx and larynx. An important feature of the throat is the epiglottis, a flap which separates the esophagus from the vertebrate trachea and prevents inhalation of food or drink....
    • pharynx
      Pharynx

      FunctionsThe pharynx is part of the digestive system and respiratory system of many organisms.Because both food and Earth's atmosphere pass through the pharynx, a flap of connective tissue called the epiglottis closes over the trachea when food is swallowed to prevent choking or Pulmonary aspiration....
      • genioglossus
        Genioglossus

        The genioglossus is a muscle of the human body which runs from the chin to the tongue....
         (tongue)
      • hyoid muscles
    • larynx
      Larynx

      The larynx , colloquially known as the voicebox, is an organ in the neck of mammals involved in protection of the vertebrate trachea and sound production....
    • trachea
      Trachea

      Trachea is a common term for 'Wind Pipe' an airway through which respiratory air passes in organisms. In vertebrates, it is held open by up to 20 C-shaped rings of cartilage....


The upper respiratory tract begins with the nose
Nose

Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for Respiration in conjunction with the mouth....
 and oral cavity, and ends at the branching of the trachea into two bronchi. The upper respiratory tract is part of the conducting zone
Conducting zone

The conducting zone of the respiratory system is made up of the vertebrate trachea, bronchi, bronchioles, and terminal bronchioles. It is composed of the 1st through the 16th division of the respiratory tract....
.

Upper respiratory tract infections are amongst the most common infections in the world.

Role in Respiration


Unlike the trachea
Trachea

Trachea is a common term for 'Wind Pipe' an airway through which respiratory air passes in organisms. In vertebrates, it is held open by up to 20 C-shaped rings of cartilage....
 and bronchi, the upper airway is a collapsible, compliant tube. As such, it has to be able to withstand suction pressures generated by the rhythmic contraction of the diaphragm that sucks air into the lungs. This is accomplished by the rhythmic contraction of upper airway muscles, such as the genioglossus
Genioglossus

The genioglossus is a muscle of the human body which runs from the chin to the tongue....
 (tongue) and the hyoid muscles. In addition to rhythmic innervation from the respiratory center
Respiratory center

Respiratory center is located in the medulla oblongata which is the lowermost part of the brain stem. RC receives controlling signals of neural, chemical and hormonal natures and controls the rate and depth of respiratory movements of the diaphragm and other respiratory muscles....
 in the medulla
Medulla

Medulla refers to the middle of something, and derives from the Latin word for 'marrow' .In medicine it refers to either bone marrow, the spinal cord, or more generally, the middle part of a structure ....
, the motoneurons controlling the muscles also receive tonic innervation that sets a baseline level of stiffness and size.

The Upper Airway during Sleep

During non-REM sleep, the tonic drive to most respiratory muscles of the upper airway is inhibited. This has two consequences: 1. The upper airway becomes more floppy. 2. The rhythmic innervation results in weaker muscle contraction
Muscle contraction

Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may #Eccentric contraction, #Concentric contraction or #Isometric contraction....
s because the intracellular calcium levels are lowered, as the removal of tonic innervation hyperpolarizes motoneurons, and consequently, muscle cells.

However, because the diaphragm is largely driven by the autonomous system, it is relatively spared of non-REM inhibition. As such, the suction pressures it generates stay the same. This narrows the upper airway during sleep, increasing resistance and making airflow through the upper airway turbulent and noisy. For example, one way to determine whether a person is sleeping it to listen to their breathing - once the person falls asleep, their breathing becomes noticeably louder. Not surprisingly, the increased tendency of the upper airway to collapse during breathing in sleep can lead to snoring
Snoring

Snoring is the vibration of respiratory structures and the resulting sound, due to obstructed air movement during breathing while sleeping. In some cases the sound may be soft, but in other cases, it can be rather loud and quite unpleasant....
, a vibration of the tissues in the upper airway. This problem is exacerbated in overweight
Overweight

Overweight is often used interchangeable with pre-obese and is generally defined as having more Adipose tissue than is optimally healthy....
 people when sleeping on the back, as extra fat tissue may weigh down on the airway, closing it. This can lead to sleep apnea
Sleep apnea

Sleep apnea is a sleep disorder characterized by pauses in breathing during sleep. Each episode, called an apnea , lasts long enough so that one or more breaths are missed, and such episodes occur repeatedly throughout sleep....
.