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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
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