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Tongue

life science Maturity 9-11 Next article →

The tongue is a complex muscular organ located within the oral cavity of typical tetrapods. It functions as a muscular hydrostat, which means it moves using only its own muscle tissue without a skeletal structure for support. This organ is essential for the digestive process because it manipulates food for chewing and swallowing. Beyond digestion, the tongue serves as the primary organ for the sense of taste. It also plays a vital role in speech for humans and vocalization in many other animals. Additionally, the tongue acts as a natural tool for cleaning the teeth.

Tongue
Tongue

The surface of the tongue is highly specialized for its various roles. The upper surface, known as the dorsum, is covered by masticatory mucosa. This tissue is a keratinized stratified squamous epithelium. Embedded within this surface are numerous projections called lingual papillae. There are four types of papillae: filiform, fungiform, vallate, and foliate. While most of these house taste buds to detect flavors, the filiform papillae are unique because they are not associated with any taste buds. The underside, or ventral surface, is a smooth fold of non-keratinized epithelium. A small fold of mucous membrane called the frenulum tethers the tongue to the floor of the mouth.

Human tongue (251 09) Section
Human tongue (251 09) Section

The structure of the human tongue is divided into distinct anatomical regions. A V-shaped groove called the terminal sulcus separates the anterior oral part from the posterior pharyngeal part. The oral part makes up roughly two-thirds of the tongue's length and is the visible portion in the mouth. The pharyngeal part makes up the remaining one-third and sits closest to the throat. At the apex of the terminal sulcus lies a small mark called the foramen cecum. This mark is a remnant of the thyroglossal duct from embryonic development. Furthermore, a vertical section of fibrous tissue called the lingual septum divides the left and right sides. This septum creates a visible groove on the surface known as the median sulcus.

Foramen caecum
Foramen caecum

Movement of the tongue is controlled by eight specific muscles divided into two groups. The four intrinsic muscles are located entirely within the tongue and do not attach to bone. These include the superior longitudinal, inferior longitudinal, vertical, and transverse muscles. They work to change the tongue's shape by lengthening, shortening, curling, or flattening it. The four extrinsic muscles are anchored to bone and change the tongue's overall position. These are the genioglossus, hyoglossus, styloglossus, and palatoglossus. The genioglossus is often called the "safety muscle" because it is the only muscle that can protrude the tongue forward.

Hyoglossus
Hyoglossus
Gray1020
Gray1020

The tongue requires a robust blood and nerve supply to function. The primary blood supply comes from the lingual artery, which is a branch of the external carotid artery. The lingual veins then drain this blood into the internal jugular vein. Nerve supply is more complex because the anterior and posterior parts of the tongue develop from different embryonic structures. The anterior two-thirds receive taste signals through the chorda tympani branch of the facial nerve. General sensation in this area is handled by the lingual nerve. In contrast, the posterior one-third uses the glossopharyngeal nerve for both taste and sensation. The hypoglossal nerve provides motor instructions to almost all the tongue's muscles.

Gray559
Gray559

Developmental biology shows how the tongue forms during the fourth week of embryonic life. It begins as a median swelling called the median tongue bud from the first pharyngeal arch. During the fifth week, lateral lingual swellings expand to cover this bud and form the anterior two-thirds. The posterior part develops from the copula and the hypopharyngeal eminence, which arise from the third and fourth arches. This complex growth explains why the different parts of the tongue have different nerve supplies. Understanding these developmental stages helps scientists see how the oral cavity is organized.

Gray979
Gray979

Physical measurements of the tongue vary between individuals. The average length of a human tongue from the tip to the oropharynx is approximately 10 cm. There are also differences in average weight between sexes. In adult males, the average tongue weight is about 99g. In adult females, the average weight is approximately 79g. These measurements and the sophisticated muscle coordination allow for the precise movements required for complex human speech and efficient swallowing.

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🖼️ Images & Media (10)
File:Facies inferior linguae.JPG
Facies inferior linguae.JPG
File:Foramen caecum.png
Foramen caecum.png
File:Tongue.svg
Tongue.svg
File:Hyoglossus.png
Hyoglossus.png
File:Gray1020.png
Gray1020.png
File:Gray559.png
Gray559.png
File:Human tongue (251 09) Section.jpg
Human tongue (251 09) Section.jpg
File:Gray979.png
Gray979.png
File:Giraffe's tongue.jpg
Giraffe's tongue.jpg
File:Macroglossum stellatarum anatomy - MHNT.jpg
Macroglossum stellatarum anatomy - MHNT.jpg
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