The document discusses embryological origins of various anatomical structures, focusing primarily on the thyroid gland and its connections to pharyngeal arches. Key points include the development of thyroid medullary cells from the ultimobranchial body and epiglottis formation from the 4th pharyngeal arch. It also includes clinical scenarios related to thyroid tissue location and developmental pathways, supported by references and sample questions from medical examinations.

1. Thyroid medullary cells that produce calcitonin develop from:
A: Ultimobranchial body
B: Floor of the primitive pharynx
C: 3rd pharyngeal arch
D: Lung buds
Correct Ans:A
Explanation
Neural crest derivatives from the ultimobranchial body give rise to thyroid medullary C cells.
It produces calcitonin. The C cells are interspersed throughout the thyroid gland.
ALSO KNOW
The ultimobranchial body arises from bilateral ventral swellings of the 4th pharyngeal
pouches and gets integrated into the thyroid where it forms the parafollicular cells or C-cells for
the production of calcitonin.
Ref: Harrison, E-18, P-2911.
Sample Previous Year Question on Embryology (Pharyngeal Arches) based on
previous Year Questions of NEET PG, USMLE,PLAB,FMGE (MCI Screening).
Please visit www.medicoapps.org for more such Quizzes
Which of the following pharyngeal arch give rise to epiglottis in embryological life?
A: 1st pharyngeal arch
B: 2nd pharyngeal arch
C: 3rd pharyngeal arch
D: 4th pharyngeal arch
Correct Ans:D
Explanation
The hypobranchial eminence, derived from the bases of the third and fourth pharyngeal
arches, forms the epiglottis. Pharyngeal and laryngeal muscles, laryngeal skeleton, cranial
nerve X are derived from fourth and sixth pharyngeal arches.
Ref: A Textbook of Neuroanatomy By Maria Patestas, Leslie P. Gartner, 2009, Page 16.

2. Sample Previous Year Question on Embryology (Pharyngeal Arches) based on
previous Year Questions of NEET PG, USMLE,PLAB,FMGE (MCI Screening).
Please visit www.medicoapps.org for more such Quizzes
A 17-year-old male is examined by a physician, who notes a mass at the back of the young
man's tongue. The physician biopsies the mass, and the pathology report comes back with a
diagnosis of normal thyroid tissue. The occasional presence of such tissue at the back of the
tongue is related to the embryonic origin of the thyroid near which of the following
structures?
A: First pharyngeal pouch
B:
Foramen
cecum
C: Nasolacrimal duct
D: Second pharyngeal arch
Correct Ans:B
Explanation
The thyroid gland originates as a mass of endodermal tissue near the foramen cecum,
which is near the tuberculum impar (which becomes the central part of the tongue). During
development, the thyroid descends in front of the pharynx, maintaining a connection to the
tongue via the thyroglossal duct.
Usually, the thyroglossal duct disappears. Uncommonly, residual ectopic thyroid tissue can
be left anywhere along the path, including at the back of the tongue. (In rare patients, all of
the thyroid tissue remains at this site, forming a mass that should not be excised, for
obvious reasons!).
The first pharyngeal pouch develops into the middle ear and eustachian tube. The
nasolacrimal ducts connect the eyes to the mouth. The second pharyngeal arch develops
into many muscles of the face and styloid process of the temporal bone.
Sample Previous Year Question on Embryology (Pharyngeal Arches) based on
previous Year Questions of NEET PG, USMLE,PLAB,FMGE (MCI Screening).
Please visit www.medicoapps.org for more such Quizzes
A 17-year-old male is examined by a physician, who notes a mass at the back of the young
man's tongue. The physician biopsies the mass, and the pathology report comes back with a
diagnosis of normal thyroid tissue. The occasional presence of such tissue at the back of the
tongue is related to the embryonic origin of the thyroid near which of the following
structures?
A: First pharyngeal pouch

3. B:
Foramen
cecum
C: Nasolacrimal duct
D: Second pharyngeal arch
Correct Ans:B
Explanation
The thyroid gland originates as a mass of endodermal tissue near the foramen cecum,
which is near the tuberculum impar (which becomes the central part of the tongue). During
development, the thyroid descends in front of the pharynx, maintaining a connection to the
tongue via the thyroglossal duct.
Usually, the thyroglossal duct disappears. Uncommonly, residual ectopic thyroid tissue can
be left anywhere along the path, including at the back of the tongue. (In rare patients, all of
the thyroid tissue remains at this site, forming a mass that should not be excised, for
obvious reasons!).
The first pharyngeal pouch develops into the middle ear and eustachian tube. The
nasolacrimal ducts connect the eyes to the mouth. The second pharyngeal arch develops
into many muscles of the face and styloid process of the temporal bone.
Sample Previous Year Question on Embryology (Pharyngeal Arches) based on
previous Year Questions of NEET PG, USMLE,PLAB,FMGE (MCI Screening).
Please visit www.medicoapps.org for more such Quizzes
Which of the following pharyngeal arches develops into epiglottis?
A: 1st pharyngeal arch
B: 2nd pharyngeal arch
C: 4th pharyngeal arch
D: 3rd pharyngeal arch
Correct Ans:C
Explanation
Pharyngeal arch Muscular contributions Skeletal contributions
1st (also called
"mandibular arch")
Muscles of mastication, anterior belly of the
digastric, mylohyoid, tensor tympani,
tensor veli palatini
Maxilla, mandible (only as a model for mandible no
formation of mandible), the incus and malleus of th
ear, also Meckel's cartilage
2nd (also called
the "hyoid arch")
Muscles of facial expression, buccinator,
platysma, stapedius, stylohyoid, posterior
belly of the digastric
Stapes, styloid process, hyoid (lesser horn and upp
body), Reichert's cartilage

4. 3rd Stylopharyngeus Hyoid (greater horn and lower part of body), thymu
parathyroids
4th Cricothyroid muscle, all intrinsic muscles of
soft palate including levator veli palatini
Thyroid cartilage, superior parathyroids, epiglottic c
6th All intrinsic muscles of larynx except the
cricothyroid muscle
Cricoid cartilage, arytenoid cartilages, corniculate c
Ref: Langman Embryology, 11 Edition, pg. 277
Sample Previous Year Question on Embryology (Pharyngeal Arches) based on
previous Year Questions of NEET PG, USMLE,PLAB,FMGE (MCI Screening).
Please visit www.medicoapps.org for more such Quizzes
Intrinsic muscles of the tongue are derived from:
A: 2nd branchial cleft
B: Pharyngeal arch mesenchyme
C: Occipital somites
D:
Cervical
somites
Correct Ans:C
Explanation
The occipital somites (four to five) give rise to muscles of the tongue. The tongue's
embryonic origin is derived from first 4 pharyngeal arches contributing different
components. Anterior 2/3rd or body of tongue is derived from 3 lingual buds the median
tongue bud (tuberculum impar) and 2 lateral lingual swellings developing at each side of
the median tongue bud. 2/3rd of the tongue originates from the first pharyngeal arch.
Sensory innervation to this area is by the mandibular branch of the trigeminal nerve. (Taste
sensation to the anterior 2/3rd of the tongue is provided by the chorda tympani branch of
the facial nerve). Post 1/3rd or root of the tongue is formed from two median elevations.
Ref: Human Embryology INDERBIR SINGH 6th Ed Page 98,156.

5. Sample Previous Year Question on Embryology (Pharyngeal Arches) based on
previous Year Questions of NEET PG, USMLE,PLAB,FMGE (MCI Screening).
Please visit www.medicoapps.org for more such Quizzes