Structure of tongue

Introduction

Tongue is a flexible muscular sheet essential for speech and mastication. Tongue is the only muscle in human body that works without the help of skeleton. It also helps in secreting some of the hormones involving in the digestion of food. Furthermore, it is essential for producing saliva that help in the softening of food as well as the digestion of carbohydrates. Saliva contains an enzyme called salivary amylase; it helps in the digestion of simple sugars. The human tongue is a wonderful muscular organ possessing many structural variations.  The tongue found in a few reptiles function as sensory organs, whereas some mammals such as cats use their tongue for grooming and cleaning. Few other animals( mammals), they  use it for breastfeeding and sucking by creating negative pressure within the oral cavity. This post is devised to explain the anatomy and physiology of the human tongue.

 

Anatomy and physiology of the human tongue

The tongue forms the floor of the oral cavity. The lingual septum is a cleft that divides the tongue into the left and right sides. Anatomically, the human tongue is divided into anterior and posterior parts. The anterior (frontal)  part is the visible part located on the front side of the mouth. Anterior teeth make up about 2/3 of the total length of the tongue. Tongue is supported by hyoid bone found deep inside the throat. Human tongue is closely associated with its surrounding parts such as the vestibular space of the mouth, teeth, oropharynx and laryngopharynx. Our tongue is supplied by a rich blood supply as well as the nerve supply.

 

Surfaces of tongue

The upper surface of the tongue 

The upper surface is called the dorsum,  divided by a groove forming  2 symmetrical halves along the median sulcus. The end of the division is ,where foramen caecum is found, which is about 2.5 cm from the root of the tongue. The terminal sulcus is a shallow groove runs forward in a V-shape from the foramen caecum. The groove helps to move the tongue forward and outwards. The pharyngeal part innervated by the glossopharyngeal nerve and the oral part of the tongue is supplied by the lingual nerve. Different surfaces of the tongue contain a variety of taste buds. Taste buds are also called the papillae, bud-like projections help in the perception of taste. There are 4 major types of taste buds, Fungiform papillae, foliate papillae, Fungiform papillae and the Filiform papillae. Circumvallate papillae are located mostly at the dorsal surface precisely on the sides of the tongue. Foliate papillae are found at the posterior and lateral surface of the tongue. Circumvallate papillae are found at the back of the tongue and are innervated by the glossopharyngeal nerve. Filiform papillae are found in many numbers, but they do not contain taste buds as they have keratinized surface. 

Taste buds-Image from Wikipedia

 

The lower surface of the tongue

The lower side of the tongue has a mucous membrane called frenulum into which many oral glands are linked. Frenulum appears flat, reddish and opens up into the major salivary glands, as well as the submandibular glands. Tonge is made up of 2 types of muscles, intrinsic and the extrinsic muscles. The tongue receives its blood supply through the lingual artery- branched out of an external carotid artery. The lingual veins are well-connected with the internal jugular vein to drain the deoxygenated blood. The tongue is innervated with motor fibres and a specialized sensory fibre that help in the perception of taste. Motor supply of the oral cavity is from the cranial nerve-12 (hypoglossal nerve).  The tip of the tongue drains to the submental nodes. The left and right halves of the anterior two-thirds of the tongue drains to submandibular lymph nodes, while the posterior one-third of the tongue drains to the jugulo-omohyoid nodes.

 

Functions of the tongue

  1. Tongue is a flexible structure assisting in speech as it is flexible and closely coordinated with the vocal cords.

  2. Tongue assist in the taste perception through papillae ( fungiform papillae,   Foliate papillae, Fungiform papillae and the  Filiform papilla)

  3. Tongue provides a place for many salivary glands and the enzymes released from saliva aid in digestive function.

 

Role of tongue in health 

Tongue plays a significant role in the health. It helps in diagnosing many diseases in advance. A normal and healthy tongue is pinkish, moistened, and no signs of bleeding and irritation. As a part of clinical examination of many disease conditions, tongue is screened for some of the signs. White patches on the tongue is an indication of fungal infections requiring instant interventions. Dry and coated tongue is the clear suggestion of the patient suffering from fever and dehydration. In many anaemic patients, tongue looks dull, whitish and sometimes changes in the taste is evident. Additionally, examination of tongue for congenital defects provides clue for many systemic diseases.

 

Related topics

1.     

Structure and functions of nose

2.

Structure of respiratory system

3.

Structure of human teeth

4.

Anatomy and physiology of stomach

 

Questions

  1. Name the enzymes present in the saliva.

  2. What is the role of tongue in digestion of food?

  3. Explain the different types of taste buds.

  4. Explain briefly about the structure of tongue.

 

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