Development of the tongue

By

Dr. Noura El Tahawy

Development of tongue

Time:

Origin:

The tongue appears in embryo of

approximately 4 weeks.

Mucous membrane:

Muscles:

Nerve supply:

Development of tongue

Mucous membrane:

1st pgaryngeal arch: gives 2 lateral

buds called lingual swellings and a

median bud called tuberculum

impar.

3rd & 4th arches: give the

hypobranchial eminence (copula)

4th arch: gives epiglottal swelling.

Development of tongue

Muscles:

Develops from 3-4 occipital

myotomes.

Nerve supply of the tongue:

Motor: Hypoglossal N. (C XII)

Sensory: general and special.

Freeing of the tongue: by forming

the alveo-lingual groove& frenulum

Formation of alveolo-lingual groove

Frenulum of tongue

To Free the

Anterior 2/3

of tongue

Innervation of the tongue

Development of the Tongue Epithelium (Mucus membrane)(endodermal)

1- The anterior two thirds:

Origin: from The 1st Pharyngeal arch (mandibular processes) two lateral lingual

processes+ one tuberculum impar meet fuse anterior 2/3 of the tongue The

site of fusion between the two lateral lingual swellings in the ant. 2/3 is indicated by the

median sulcus.

2- The pharyngeal part (posterior third):

Origin: 3rd & 4 th pharyngeal arches hypobranchial eminence four swellings

meet fuse copula of Hypobranchial eminince posterior third of the tongue.

3. Fusion of ant. 2/3 with post. 1/3 : The site of fusion between anterior 2/3 & posterior 1/3

is indicated by V- shaped sulcus terminalis.

4. Free ant . 2/3 by forming Alveolo-lingual groove: U shaped sulcus mobile tongue

leaving frenulum linguae.

Tongue Musculature:

is derived from 3-4 occipital myotomes, supplied by hypoglossal nerve.

SUMMARY OF TONGUE DEVELOPMENT

Embryological background that explains

tongue innervation

This unusual development of the tongue explains its innervation

Since the mucosa of the anterior two thirds of the tongue is

derived from the first arch, it is supplied by the fifth cranial

nerve (trigeminal nerve), whereas the mucosa of the posterior

third of the tongue, derived from the third arch, is supplied by the

ninth cranial nerve (glossopharyngeal nerve)

The epiglottis is formed from 4th arch, so it is supplied by

superior laryngeal nerve of vagus (4th arch nerve).

- Musculature is derived from occipital myotomes which

migrate to the tongue carrying with them its nerve supply: The

hypoglossal nerve.

Congenital Anomalies of the Tongue

Cause: incomplete degeneration of the cells which

connect the undersurface of the tongue to the floor of

the mouth. (Incomplete formation of alveolo-lingual

groove). Features: the frenulum may be thick and short

or it may extend to the tip of the tongue leading to

limitation of tongue protrusion. It is treated by

freneotomy.

Tongue-tie

(Ankyloglossia)

- Cyst within the tongue: remenant of thyroglossal cyst

- Persistant thyroglossal duct that remain opened

- lingual thyroid

Congenital Cyst

& fistula

Complete or partial absence of the tongue Aglossia

Abnormal small tongue Microglossia

Abnormal large tongue Macroglossia

Due to failure of complete fusion of lingual swellings Bifid tongue

Anomalies of the tongue

Ankyloglossia

(Tongue-tie) : Normal

Development of tongue

Freneotomy: Normal

Development of thyroid gland In the 4th week (at 24 days of gestation), the thyroid gland develops as a

depression and epithelial thickening in the floor of the pharynx.

(endodermal)

This appears at a point between the body and base of the tongue called

the foramen caecum.

From this point, the thyroid primordium descends in the neck as a

bilobed diverticulum to reach apiont in front of the trachea in the 7th

week.

During this migration, the gland remains connected to the floor of the

oral cavity by an epithelial cord or duct, the thyroglossal duct which later

becomes a cord of cells.

The foramen caecum remains at the site of origin.

The thyroid gland begins to function at the beginning of the 3rd month

when colloid containing follicles appear.

Adult Thyroid gland

Summary

Developmental defects of thyroid

1. Aplasia of thyroid: Failure of development of Thyroid

gland (Cretinism)

2. Ectopic Thyroid gland: Incomplete descend of thyroid

gland to become in the substance of tongue (Lingual

thyroid)

3. Aberrant thyroid: in the superior mediastinum

4. Accessory Thyroid Tissue

5. Thyroglossal Cyst : See Below

6. Thyroglossal Fistula: See below

• Thyroglossal cyst and Fistula: The cyst is due to

persistence of part of the duct with cyst formation. Fistula

means the presence of connection between the cyst & the

surface of the neck . Cysts and fistulae found in the

midline of the neck along the course of the thyroglossal

duct. But it is usually found at the level of the hyoid bone

and the thyroid cartilage. Infection of the cyst or fistula

may occur

Developmental defects of thyroid

Sites of ectopic thyroid

Thyroglossal duct Cyst

Developmental defects of thyroid

Development of Parathyroid Glands

The inferior parathyroid glands develop from

endoderm of third pharyngeal pouch, they travel

downwards during the foetal life.

In contrast, the superior parathyroid glands develop

from endoderm of fourth pharyngeal pouch. They

remain superior to the thyroid lobes.

The parathyroid hormone is produced from the 12th

week of development onwards.

Development of Parathyroid Glands

Salivary glands

Appear as epithelial buds from oral cavity.

Parotid gland: The first to appear, early in 6th week, from oral

ectoderm, near angle of stomodeum. It forms a tube, extends into

cheek’s mesoderm. (Between the mandibular&Maxillary processes)

Its Proximal part forming the parotid duct;

Its distal end breaks to form the glandular alveoli.

Capsule & connective septae develop from surrounding mesoderm.

The duct opening is carried to open inside the cheek.

Submandibular gland: Appear late in 6th week, from an

endodermal bud in floor of stomodeum (alveolo- lingual groove).

Develops in same way as parotid gland.

Sublingual gland: appear in 8th week, from multiple endodermal

buds in the alveolo-lingual groove.

Summary of Salivary glands development

• Paranasal sinuses develop during late fetal life.

• They form as outgrowths or diverticula of the walls

of the nasal cavities and become air filled extensions of the

nasal cavities in the adjacent bone.

- Frontal – 3 to 4 months of I.U

- Ethmoidal – 4 months of I.U

- Maxillary – Develops at 10 weeks of I.U

- Sphenoidal – 4 months of I.U

DEVELOPMENT OF PARANASAL SINUSES

Thanks