Derivatives of Floor of Pharynx (Page 71) Dr. Sherif Fahmy
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Derivatives of Floor of Pharynx(Page 71)
Dr. Sherif Fahmy
Forebrain bulge
Pericardial bulge
Stomodeum
Bucco-pharyngeal membrane
Pharynx
Floor of pharynx
Dr. Sherif Fahmy
Dr. Sherif FahmyLaryngeo-trachial groove
Site of developing tongue, epiglottis and thyroid gland in the floor of pharynx
Dr. Sherif Fahmy
Development of Tongue(Page 71)
Sulcus terminalis
Foramen cecum
Lingual tonsil
Anterior 2/3
Posterior 1/3
Epiglottis
Dr. Sherif Fahmy
Development of Tongue• Tongue is developed at the floor of pharynx.• Mucosa of tongue is developed from
endodermal cells at floor of pharynx opposite 1st, 2nd and 3rd pharyngeal arches.
• Most of muscles of tongue are developed from mesoderm of occipital myotomes, some are devolped from mesoderm in situ.
Dr. Sherif Fahmy
A- Mucosa of Tongue• Anterior 2/3 is developed from floor of
pharynx opposite 1st pharyngeal arch from: two lingual swellings and tuberculum impar.
• Posterior 1/3 is developed from cranial ½ of hypobranchial eminence which is developed in floor of pharynx opposite 3rd pharyngeal arch.
• Sulcus terminalis separates between anterior 2/3 and posterior 1/3.
• Linguo-gingival groove partially separates between tongue and both alveolar margin and floor of oral cavity.
Dr. Sherif Fahmy
Forebrain bulge
Pericardial bulge
Stomodeum
Bucco-pharyngeal membrane
Pharynx
Floor of pharynx
Dr. Sherif Fahmy
Dr. Sherif Fahmy
2 lingual swellings
Tuberculum impar
Foramen ceacum
Copula
Hypobranchial eminence
1st
2nd
3rd
4th
Dr. Sherif Fahmy
Lingual swellings
Tuberculum impar
Foramen caecum
Hypobranchial eminence
Lingual swelling
Anterior 2/3 of tongue
Hypobranchial eminence
Posterior 1/3 of tongue
Foramen caecum
Epiglottis
Tuberculum impar
Dr. Sherif Fahmy
Dr. Sherif Fahmy
2 lingual swellings
1st arch
B- Muscles of Tongue• Lingual muscles are developed from occipital
myotomes (2nd, 3rd and 4th myotomes).• These myotomes migrate ventrally superficial
to external and internal carotid arteries.• Hypoglossal nerve follows occipital
myotomes to enter developing mucosa of tongue.
Dr. Sherif Fahmy
Bucco-pharyngeal membrane
Cloacal membrane
Cardiogenic area
Notochord
Paraxial mesoderm (somites)
Dr. Sherif Fahmy
Somites
A- Muscles of tongue
Nerve Supply of Tongue• Anterior 2/3 of mucosa: is supplied by lingual
nerve for general sensations and chorda tympani for taste.
• Posterior 1/3 of mucosa: is supplied by glossopharyngeal nerve for general sensation and taste.
• Muscles of tongue are supplied by hypoglossal nerve.
Dr. Sherif Fahmy
Anomalies of Tongue• 1- Aglossia: Complete absence of tongue.• 2- Microglossia: Small sized tongue.• 3- Macroglossia: Large sized tongue.• 4- Bifid tongue: due to failure of fusion between 2
lingual swellings.• 5- Tongue tie: short frenulum due to defective
formation of linguo-gingival groove. .
Dr. Sherif Fahmy
Bifid tongue
Tie tongue
Development of Thyroid Gland
(Page 73)
• It begins as thyroid primordium which is endodermal proliferation between tuberculum impare and hypobranchial eminence.
• Invagination of the primordium will form a bilobed diverticulum.
• Elongation of thyroid diverticulum to form thyro-glossal duct. It elongates downwards infront hyoid and thyroid cartilage. It reaches its final site by the 7th week.
• Thyroid follicles are developed from endodermal cells while ultimobranchial body gives parafollicular cells to thyroid gland. Capsule and fiberous septa are formed from mesoderm. Dr. Sherif
Fahmy
Dr. Sherif Fahmy
2 lingual swellings
Tuberculum impar
Thyroid primordium
Copula
Hypobranchial eminence
1st
2nd
3rd
4th
Dr. Sherif Fahmy
Dr. Sherif Fahmy
Foramen cecum
Thyroid diverticulum
Developing anterior 2/3 of tongue
Dr. Sherif Fahmy
Dr. Sherif Fahmy
Thyroglossal duct
Thyroid gland
Developing anterior 2/3 of tongue
Developing hyoid bone
Posterior 1/3 of tongue
Dr. Sherif Fahmy
Dr. Sherif Fahmy
Foramen cecum
Degenerating thyro-glossal duct
Hyoid bone
Thyroid cartilage
Levator glandulae thyroidaePyramidal lobe Lobe of
thyroid gland
Fate of thyroglossal duct
Dr. Sherif Fahmy
Fate of Thyro-glossal Duct• Upper end of the duct remains as foramen cecum
at apex of sulcus terminalis on dorsum of tongue.• The duct degenerates from foramen cecum and
hyoid bone.• The duct from the hyoid to divisions of the duct
form levator glandulae thyroidae and may be pyramidal lobe.
• Divisions of the duct will form lobes of thyroid gland with isthmus inbetween.
• Ultimobranchial body forms parafollicular cells of the gland.
Congenital Anomalies • Thyroid agenesis: Failure of its formation.• Lingual thyroid: Failure of thyroid descend.• Aberrant thyroid (Retrosternal goiter): over-
descend of thyroid gland in the thorax.• Thyroglossal cyst: It is persistence of a part of
the thyroglossal duct.• Thyroglossal fistula: Thyroglossal duct opens
to skin.
Dr. Sherif Fahmy
Dr. Sherif Fahmy
Dr. Sherif Fahmy
Dr. Sherif Fahmy
Development of Respiratory System
(page 75)
• Respiratory diverticulum: It begins by formation of endodermal laryngo-tracheal groove at floor of pharynx caudal to hypobranchial eminence.
• Laryngotracheal tube is separated from foregut by formation of tracheo-esophageal septum. This tube elongates till the thorax.
• Upper part of the tube forms the mucous membrane of larynx while lower part form mucus membrane of trachea and bronchi.
• The lower end of the tube will divides to form 2 bronchial buds.
• Surrounding mesoderm will form muscles and cartilages of larynx and trachea.
Dr. Sherif Fahmy
Formation of Larynx• Cartilages: Epiglottis from caudal ½ of
hypobranchial eminence. Thyroid cartilage from 4th arch, rest of laryngeal cartilages from 6th arch.
• Muscles: cricothyroid from 4th arch, rest of muscles from 6th arch.
• Mucous membrane: Supraglottic from 4th arch, infraglottic from 6th arch.
Formation of Lungs• Each bronchial bud divides into 3 branches, but on left side
one of the branches disappears. Right lung has 3 lobes, left lung has 2 lobes.
• Each branch of the bronchial bud divides repeatedly to form bronchioles and lastly alveoli (17 generations of divisions before birth and 6 after birth).
• Blood vessels fiberous tissue of the lungs are formed from surrounding mesoderm.
• Lung invades pleura from medial aspect, so pleura surrounds lung by 2 layers.
• Expansion of lung occurs after birth when the baby takes his first inspiration.
Dr. Sherif Fahmy
2 lingual swellings
Tuberculum impar
Foramen ceacum
Copula
Hypobranchial eminence
Laryngeo-trachial groove
Dr. Sherif Fahmy
Pharynx
Respiratory diverticulum
Laryngeo-tracheal tube
esophagus
Dr. Sherif Fahmy
Laryngo-tracheal duct
Foregut Tracheo-esophageal ridges
Bronchial buds
Dr. Sherif Fahmy
Congenital Anomalies• 1- Respiratory distress syndrom: Due
to absence of surfactant.• 2- Ectopic lung lobe: lung lobe that
arises from trachea or esophagus.• 3- Congenital lung cysts: Dilatation of
terminal bronchi.• 4- Esophageal atresia: with or without
tracheo-esophageal fistula
Dr. Sherif Fahmy
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