Structure of tongue

Introduction

Tongue is a flexible muscular sheet essential for speech and mastication. It also helps in secreting some of the hormones involving in the digestion of food. It also plays an important role in producing saliva that help in the softening of food and carbohydrate digestion because saliva has an enzyme called salivary amylase. The human tongue is a wonderful muscular organ having many structural variations according to the different functions that it performs. Most of the vertebrates are characterised by a tongue having a similar structure and functions. The tongues in a few reptiles function as sensory organs, whereas in some mammals such as cats they use their tongue for grooming and cleaning. Some mammals use it for breastfeeding and sucking by creating negative pressure within the oral cavity. This post is designed to understand the anatomy and physiology of the human tongue.

Table of contents

1. Introduction

2. Anatomy and physiology of human tongue

    2.1 The upper surface of the tongue 

    2.2 The lower surface of the tongue

3. Functions of tongue

 

Anatomy and physiology of 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 in the front side of the mouth which makes up two-thirds the total length of the tongue. Tongue is supported by hyoid bone in the throat. The tongue is associated with its surrounding parts such as the vestibular space of the mouth, teeth, oropharynx and laryngopharynx. The posterior part of the tongue stays close to the throat. Tongue has a very rich blood supply and nerve supply.

 

The upper surface of the tongue 

The upper surface is called the dorsum. Dorsum is being divided by a groove into 2 symmetrical halves by the median sulcus. The end of the division is where foramen cecum 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 cecum, forwards and outwards to the margins of the tongue. The pharyngeal part innervated by the glossopharyngeal nerve and the oral part of the tongue is supplied by the lingual nerve. There are multiple taste buds found on the upper tongue. Taste buds are also called the papillae. Papillae are the bud-like projections distributed across the tongue to assist 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 the frenulum. This is where many oral glands are located. Frenulum is flat, reddish and opens up into the major salivary glands, and submandibular glands. There are 2 types of muscles in the tongue; intrinsic or 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- specialized sensory fibres for taste and some general sensory fibres assist in the perception of sensation. Motor supply is from cranial nerve-12 or 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 tongue

  1. Tongue is a flexible structure assisting in the movement of the tongue while speaking. The tongue is well connected with the vocal cords to produce specific words.

  2. Tongue assist taste perception through  in the function of taste through 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.

 





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