53. TONGUE AND NOSE

TONGUE AND NOSE

TONGUE:

The tongue is a muscular organ in the mouth covered with a moist, pink tissue called the mucosa. It plays a vital role in licking, tasting, breathing, swallowing, and speaking. The papillae on the tongue give it a rough texture and contain taste buds that help in detecting different tastes. Several nerves transmit taste signals from the tongue to the brain, enabling taste sensation.

STRUCTURE OF THE TONGUE:

The human tongue measures about 3.3 inches in men and 3.1 inches in women. It is divided into three main parts:

  • Tip
  • Body
  • Base

Embryologically, it consists of two parts:

  • Anterior (oral/presulcal part): Attached to the floor of the oral cavity.
  • Posterior (pharyngeal/postsulcal part): Forms the ventral wall of the oropharynx.

ELEMENTS OF THE TONGUE:

  1. Epithelium:
    • Comprises papillae and taste buds.
    • Taste buds are lined by squamous epithelial cells and contain taste cells with short taste hairs that detect dissolved chemicals in saliva.
  2. Muscles:
    • The muscles of the tongue are voluntary and made up of cross-striated fibres.
  3. Glands:
    • Three types of glands are found in the tongue:
      • Mucous glands
      • Serous glands
      • Lymph nodes (lingual tonsils)

NERVE SUPPLY:

  • Glossopharyngeal nerve and chorda tympani branch of the facial nerve – for taste sensation.
  • Trigeminal nerve – for sensations of pain, touch, and temperature.

FUNCTIONS OF THE TONGUE:

  • Mastication: Helps in chewing.
  • Deglutition: Aids in swallowing food.
  • Taste: Transmits taste signals to the brain.
  • Speech: Facilitates pronunciation and articulation.
  • Secretion: Produces mucus and serous fluids that moisten the mouth.

SALIVARY GLANDS:

The tongue is associated with three pairs of major salivary glands:

  1. Parotid gland: Opens into the mouth opposite the second upper molar tooth through Stensen’s duct.
  2. Submaxillary gland: Opens on the floor of the mouth through Wharton’s duct.
  3. Sublingual gland: Opens through Rivinus ducts on the floor of the mouth.

SENSE OF TASTE (GUSTATION):

Taste buds act as chemoreceptors found mainly on the tongue papillae. They detect chemicals dissolved in saliva and send signals through the glossopharyngeal (IX), facial (VII), and vagus (X) nerves to the medulla, thalamus, and finally the parietal lobe of the cerebral cortex.

Four Basic Taste Sensations:

  • Sweet
  • Sour
  • Bitter
  • Salty
    (Additionally, umami and metallic tastes are also recognized.)

Taste and smell work closely together—loss of smell often reduces the sense of taste. Taste also triggers salivation, gastric secretion, and can initiate gag reflex when something unpleasant is consumed.

NOSE:

The nose is the prominent structure on the face responsible for breathing and smell (olfaction). Around 80% of taste perception is influenced by smell. It also helps in speech, filtration, humidification, and warming of inhaled air.

ANATOMY OF THE NOSE:

The external nose has a pyramidal shape with:

  • Root (upper part)
  • Dorsum (middle)
  • Apex (tip)
  • Nostrils (nares): Openings to the nasal cavity, separated by the nasal septum.

Bony and Cartilaginous Components:

  • Bony part: Nasal, maxilla, and frontal bones.
  • Cartilaginous part: Alar, lateral, and septal cartilages.
  • The septal cartilage connects to the ethmoid and vomer bones.

NASAL CAVITY:

The nasal cavity lies within the skull and opens:

  • Anteriorly – through the nares
  • Posteriorly – to the nasopharynx via the choanae

It has three regions:

  1. Vestibule: Contains hair follicles for filtering air.
  2. Respiratory region: Lined with respiratory epithelium.
  3. Olfactory region: Contains olfactory receptors for smell.

The cavity connects to the paranasal sinuses (frontal, maxillary, sphenoidal, ethmoidal) lined with respiratory mucosa and innervated by the trigeminal nerve.

BLOOD SUPPLY:

  • Supplied by branches of both external and internal carotid arteries:
    • External: Sphenopalatine, greater palatine, superior labial, and lateral nasal arteries.
    • Internal: Anterior and posterior ethmoidal arteries.
  • Rich anastomosis near the nasal septum causes frequent nosebleeds.

NERVE SUPPLY:

  • Olfactory nerve (CN I): For smell.
  • Trigeminal nerve (CN V): For general sensation.
  • Facial nerve (CN VII): Parasympathetic supply to mucosal glands.
  • Sympathetic fibers (T1): Control mucosal blood flow.

FUNCTIONS OF THE NOSE:

  1. Respiration:
    • Filters, warms, and humidifies inhaled air before it enters the lungs.
  2. Olfaction:
    • Detects odours through olfactory receptors connected to the olfactory bulb and cerebral cortex.
  3. Purification of Air:
    • Cilia trap dust and harmful particles.
    • Trapped particles are either swallowed or expelled through sneezing.
  4. Moisturizing of Air:
    • Mucosa adds moisture and regulates temperature for lung comfort.
  5. Taste Assistance:
    • Works with the tongue to identify flavours during eating.
  6. Speech:
    • Modifies airflow and enhances vocal resonance through paranasal sinuses.

Detailed Notes:

For PDF style full-color notes, open the complete study material below:

PATH: PHARMD/ PHARMD NOTES/ PHARMD FIRST YEAR NOTES/ HUMAN ANATOMY AND PHYSIOLOGY/ TONGUE AND NOSE.

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