Nose and nasal cavity, sinuses, pharynx, larynx, trachea, lungs, bronchi,alevoli-2

The Larynx

Between the laryngopharynx and the trachea, the larynx, often known as the voice box, serves as a connection. It measures 5 cm in length and runs from the third to the sixth cervical vertebrae.

Male sex hormone accelerates the larynx's growth during puberty, making it significantly larger in men than in women. The Adam's apple is a prominent feature of the larynx. As a result, the male has a much more pronounced Adam's apple.

Structure of The Larynx

It is lined with ciliated mucus membrane and composed of numerous cartilage, muscle, and ligament pieces. The Adam's apple-shaped cartilaginous framework of it protrudes from the front of the neck. The following are the main larynx cartilages:

• Unpaired
  • Thyroid cartilage -1
  • Cricoid cartilage -1
  • Epiglottis -1
• Paired
  • Arytenoid cartilages -2
  • Corniculate cartilages-2
  • Cuneiform cartilages-2

Cricoid Cartilage

• The cricoid cartilage completely encircles the airway and is the least superior of the laryngeal cartilages. The cricoid cartilage has a broad lamina posterior to the airway and a much narrower arch circling anteriorly, giving it the appearance of a signet ring.

Thyroid Cartilage

• The thyroid cartilage, which is part of the laryngeal cartilage, is the largest. It is made up of a right and a left lamina, which are anteriorly converging and joining after being widely separated posteriorly. The laryngeal prominence, also known as Adam's apple, is the forward-facing point where the two broad, flat laminae fused. Men have a more pronounced laryngeal prominence than women because the angle between the two laminae is more acute in men (90°) than in women (120°).

Epiglottis

• The epiglottis is a leaf-shaped cartilage that projects postero-superiorly from the posterior part of the thyroid cartilage at the angle where it is connected by its stem. The thyro-epiglottic ligament is used for attachment. The epiglottis aids in preventing food from entering the rest of the respiratory system. During swallowing, the epiglottis descends and covers the opening into the larynx as the larynx moves forward and upward.

Arytenoid Cartilages

• The two arytenoid cartilages have a pyramidal shape and have three surfaces: an arytenoid base and an arytenoid apex.

Corniculate

• The bases of the two tiny corniculate cartilages, which are conical in shape, articulate with the arytenoid cartilages' apices. Their apices extend postero-medially in the direction of one another.

Cuneiform

• These two tiny, club-shaped cartilages are suspended in the area of the larynx's fibro-elastic membrane that connects the arytenoids cartilages to the lateral margin of the epiglottis. They are located anterior to the corniculate cartilages.

Vocal Cords

The upper end of the larynx has a pair of mucus membrane folds called vocal cords that are connected and used to produce sound. The larynx is also known as the voice box for this reason. The difference between the male and female voices is due to the size of the larynx; a man's voice has a lower pitch because his larynx is larger than a woman's. False vocal cords (vestibular fold) and true vocal cords are the two different kinds of vocal cords. Rima vestibularis refers to the triangle aperture between two vestibular folds, which has its anterior peak and its posterior base produced by the wall of the larynx. The real voice chords are located below the vestibular folds. Between the vocal cords, there is a triangle aperture known as the glottis or Rima glotttidis.

Associated Organs with the Larynx

• Superiorly
  • Both the tongue's root and the hyoid bone.
• Inferiorly
  • It is carried on as the trachea.
• Anteriorly
  • The neck muscles and the muscles connected to the hyoid bone.
• Posteriorly
  • The laryngo-pharynx, as well as the third through sixth cervical vertebrae.
• Laterally
  • The thyroid's lobes are described.

Blood Supply

• Both the superior and inferior laryngeal arteries supply blood to the larynx. The internal jugular vein removes the venous blood from the body.

Nerve Supply

• The larynx is supplied by vagus nerve branches.

Functions of The Larynx

• It serves as an organ for creating voice.
• It offers a clear airway.
• Additionally, it filters and moistens the air.
• The epiglottis maintains a proper pathway for the air and food by preventing food from entering the larynx and trachea.

Voice Production

The voice cords are stretched across the glottis and supported by cartilage. When the vocal chords vibrate as a result of the force of air, a sound is created. False vocal cords, the superior pair, play no part in sound creation. As air rushes up from the lungs, the inferior pair, the real vocal cords, vibrate and produce sounds.

The real vocal cords are pulled together, the arytenoids cartilages are rotated medially, and the space between the two vocal cords is reduced as the intrinsic laryngeal muscles contract. These constricted vocal cords quiver and emit noises when air is forced through them. The vocal cords are moved apart (by abduction) when the muscles relax, creating a space between them that prevents sound production.

The vocal chords' tension affects a sound's pitch; the more the tension, the higher the pitch. Lower-pitched sounds are produced when the vocal folds' muscular tension is reduced, which causes them to vibrate more slowly.

For the sound to be translated into understandable speech, more structures are required. Vocal resonance is influenced by the mouth, nasal passages, pharynx, and paranasal sinuses.

The Trachea

The trachea, which joins the larynx and bronchi, is an unpaired tube. Another name for it is a windpipe. It is 12 cm long and has a diameter of 2.5 cm. The right and left bronchi are located anterior to the esophagus, which runs from the larynx to the fifth thoracic vertebra (C6 to T5).

Structure of The Trachea

The inner mucosa, middle hyaline cartilage, and outside adventitia are the three layers of tissue that make up the tracheal wall. The same goblet cell and cilia are found in the inner mucosa. Hyaline cartilage is arranged in 16–20 incomplete, horizontal rings in the intermediate layer. The trachea is covered in these cartilages, which have a form like a small horseshoe or the letter C. Since the esophagus can protrude into this area during swallowing, all of these cartilages' open sections are at the back. The involuntary trachealis muscle, a smooth muscle connecting the ends of the rings, spans the posterior gaps in the tracheal rings. As a result, the trachea's posterior wall is flat.

The trachea's function is to transport air from the larynx to the lungs. The trachea is connected to the surrounding tissues by the outer layer.

Associated Organs with the Trachea

• Superiorly
  • The larynx
• Inferiorly
  • ​​​​​​​The right and left bronchi
• Anteriorly
  • The thyroid isthmus is in the upper part, and the aortic arch and the manubrium sterni are in the lower part.
• Posteriorly
  • ​​​​​​​The vertebral column and trachea are separated by the oesophagus.
• Laterally
  • The thyroid's lobes are described.

Functions of The Trachea

• It creates a channel via which air can enter the lungs.
• It adds more moisture to the air.
• Particles that are not filtered by the respiratory organs above it are trapped in the goblet cells.
• Mucus and other waste cannot enter the bronchi because the cilia of the trachea direct them toward the pharynx.

Blood Supply

• The branches of the inferior thyroid arteries supply the arterial blood, and the inferior thyroid vein removes the venous blood.

Nerve Supply

• The vagus nerve supplies the nerves.