Pharyngeal arches

Pharyngeal arches US Medical PG Question 1: A 1-year-old girl born to a 40-year-old woman is undergoing an examination by a pediatric resident in the hospital. The pregnancy was uneventful and there were no complications during the delivery. The physical examination reveals midface hypoplasia with a flat nasal bridge and upslanting palpebral fissures. She has a small mouth and chest auscultation reveals a blowing holosystolic murmur that is heard best along the sternal border. The family history is unremarkable. A karyotype analysis is ordered because the resident suspects a numerical chromosomal disorder. Which of the following phenomena leads to the infant’s condition?

• A. Meiotic non-disjunction (Correct Answer)
• B. Uniparental disomy
• C. Genomic imprinting
• D. Partial deletion
• E. Trinucleotide repeat

Pharyngeal arches Explanation: ***Meiotic non-disjunction*** - The combination of **midface hypoplasia**, **upslanting palpebral fissures**, **flat nasal bridge**, and a **holosystolic murmur** (suggesting a **ventricular septal defect**) in an infant born to an older mother is highly characteristic of **Down syndrome (Trisomy 21)**. - **Trisomy 21** is most commonly caused by **meiotic non-disjunction**, where homologous chromosomes fail to separate during meiosis I or sister chromatids fail to separate during meiosis II, resulting in a gamete with an extra chromosome 21. *Uniparental disomy* - **Uniparental disomy** occurs when an individual receives both copies of a chromosome from a single parent, rather than one from each parent. - While it can lead to various genetic disorders, it does not typically cause **Trisomy 21** or the specific constellation of features described. *Genomic imprinting* - **Genomic imprinting** is an epigenetic phenomenon where certain genes are expressed in a parent-of-origin specific manner. - While relevant to conditions like Prader-Willi or Angelman syndromes, it is not the mechanism responsible for **Trisomy 21**. *Partial deletion* - A **partial deletion** refers to the loss of a segment of a chromosome. - While chromosomal deletions cause various syndromes (e.g., Cri-du-chat syndrome), they would result in a **monosomy or partial monosomy**, not the extra chromosome seen in Trisomy 21. *Trinucleotide repeat* - **Trinucleotide repeat disorders** involve an abnormal expansion of a three-nucleotide sequence within a gene, leading to conditions like Huntington's disease or fragile X syndrome. - This mechanism is not associated with the etiology of **Down syndrome**.

Pharyngeal arches US Medical PG Question 2: A 10-year-old boy comes for a post-operative clinic visit with his ENT surgeon three months after airway reconstruction surgery and placement of a tracheostomy tube. Since the surgery, he says that he has been able to breathe better and is now getting used to tracheostomy care and tracheostomy tube changes. In addition to this surgery, he has had over twenty surgeries to implant hearing aids, reconstruct his cheekbones, and support his jaw to enable him to swallow. He was born with these abnormalities and had difficult breathing, hearing, and eating throughout his childhood. Fortunately, he is now beginning to feel better and is able to attend public school where he is one of the best students in the class. Abnormal development of which of the following structures is most likely responsible for this patient's malformations?

• A. Second branchial cleft
• B. First branchial pouch
• C. Third and fourth branchial pouches
• D. First branchial arch (Correct Answer)
• E. Second branchial arch

Pharyngeal arches Explanation: ***First branchial arch*** - The clinical presentation describes features consistent with **Treacher Collins syndrome** (TCS), also known as mandibulofacial dysostosis, which results from maldevelopment of **both the first and second branchial arches**. - However, the **predominant and most characteristic features** arise from **first branchial arch** abnormalities: **mandibular hypoplasia** (requiring jaw support for swallowing), **malar/zygomatic hypoplasia** (reconstructed cheekbones), and **maxillary hypoplasia**. - These first arch skeletal abnormalities cause the **airway obstruction** (requiring tracheostomy) and feeding difficulties. - The first branchial arch gives rise to: **mandible, maxilla, zygomatic bone, incus, malleus, muscles of mastication, and CN V** (trigeminal nerve). - While hearing issues may involve second arch structures (stapes), the **overwhelming majority** of this patient's clinical problems stem from first arch malformations. *Second branchial cleft* - The second branchial cleft typically forms the **cervical sinus**, which normally obliterates. Persistence can lead to **cervical cysts or fistulas**, presenting as neck masses. - Abnormalities of the second branchial cleft do not explain the extensive craniofacial malformations, hearing deficits, or airway compromise seen in this patient. *First branchial pouch* - The first branchial pouch gives rise to the **auditory (eustachian) tube** and the **tympanic cavity** (middle ear). - While isolated first pouch defects could contribute to hearing problems, they would **not explain** the severe facial bone malformations (mandibular and malar hypoplasia), airway obstruction, or feeding difficulties. - The pouch is distinct from the arch, which forms the skeletal and muscular structures. *Third and fourth branchial pouches* - The third branchial pouch contributes to the **inferior parathyroid glands** and the **thymus**. The fourth branchial pouch contributes to the **superior parathyroid glands** and the **ultimobranchial body** (parafollicular C cells of the thyroid). - Abnormalities in these pouches, such as in **DiGeorge syndrome (22q11.2 deletion)**, lead to **T-cell immunodeficiency, hypocalcemia, and cardiac defects** but do not account for the craniofacial and hearing abnormalities described. *Second branchial arch* - The second branchial arch gives rise to the **stapes**, **styloid process**, **lesser horn and upper body of hyoid bone**, **stapedius muscle**, and **CN VII** (facial nerve). - While Treacher Collins syndrome involves both first and second arch abnormalities, the **second arch contributions** are less prominent clinically. - Second arch defects could contribute to **conductive hearing loss** (via stapes abnormalities) and **facial nerve issues**, but these are not the predominant features in this case. - The critical skeletal malformations causing airway compromise, feeding difficulties, and facial dysmorphism are primarily **first arch** derivatives.

Pharyngeal arches US Medical PG Question 3: A child is born by routine delivery and quickly develops respiratory distress. He is noted to have epicanthal folds, low-set ears that are pressed against his head, widely set eyes, a broad, flat nose, clubbed feet, and a receding chin. The mother had one prenatal visit, at which time the routine ultrasound revealed an amniotic fluid index of 3 cm. What is the most likely underlying cause of this patient's condition?

• A. Unilateral renal agenesis
• B. An extra 18th chromosome
• C. Autosomal recessive polycystic kidney disease (ARPKD)
• D. A microdeletion in chromosome 22
• E. Bilateral renal agenesis (Correct Answer)

Pharyngeal arches Explanation: ***Bilateral renal agenesis*** - The combination of **amniotic fluid index (AFI) of 3 cm** (indicating **oligohydramnios**) and multiple facial and limb anomalies strongly suggests **Potter sequence**. - **Bilateral renal agenesis** is the most common cause of **Potter sequence**, leading to absence of fetal urine production and subsequent oligohydramnios, which restricts fetal movement and lung development. *Unilateral renal agenesis* - **Unilateral renal agenesis** typically does not cause **oligohydramnios** because the single functioning kidney can produce sufficient urine. - While it can be associated with other anomalies, the severe extent of Potter sequence features described here is unlikely with only unilateral involvement. *An extra 18th chromosome* - An extra 18th chromosome refers to **Edwards syndrome (Trisomy 18)**, which presents with severe intellectual disability, micrognathia, prominent occiput, and rocker-bottom feet. - While Edwards syndrome is associated with a variety of anomalies, including renal issues, the constellation of features (especially the clear link to oligohydramnios and respiratory distress) points more directly to Potter sequence. *Autosomal recessive polycystic kidney disease (ARPKD)* - **ARPKD** causes **enlarged, cystic kidneys** and can lead to **oligohydramnios** and respiratory distress due to renal insufficiency. - However, the description of **epicanthal folds, low-set ears, widely set eyes, and a broad, flat nose** is more characteristic of the **Potter facies** seen in severe oligohydramnios, rather than specific to ARPKD itself. *A microdeletion in chromosome 22* - A microdeletion in chromosome 22 typically refers to **22q11.2 deletion syndrome (DiGeorge syndrome)**, which is associated with **cardiac defects**, **abnormal facies**, **thymic hypoplasia**, **cleft palate**, and **hypocalcemia**. - While renal anomalies can occur in DiGeorge syndrome, the primary presentation is not characterized by the severe oligohydramnios and classic Potter sequence features described.

Pharyngeal arches US Medical PG Question 4: A 5-year-old boy is brought to the emergency department by his grandmother because of difficulty breathing. Over the past two hours, the grandmother has noticed his voice getting progressively hoarser and occasionally muffled, with persistent drooling. He has not had a cough. The child recently immigrated from Africa, and the grandmother is unsure if his immunizations are up-to-date. He appears uncomfortable and is sitting up and leaning forward with his chin hyperextended. His temperature is 39.5°C (103.1°F), pulse is 110/min, and blood pressure is 90/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 95%. Pulmonary examination shows inspiratory stridor and scattered rhonchi throughout both lung fields, along with poor air movement. Which of the following is the most appropriate next step in management?

• A. Nebulized albuterol
• B. Direct laryngoscopy and pharyngoscopy
• C. Immediate nasotracheal intubation in the emergency department
• D. Prepare for emergency airway management in the operating room with anesthesia and ENT backup (Correct Answer)
• E. Intravenous administration of antibiotics

Pharyngeal arches Explanation: ***Prepare for emergency airway management in the operating room with anesthesia and ENT backup*** - The constellation of **hoarseness**, **muffled voice**, **drooling**, **inspiratory stridor**, **fever**, and the classic **tripod position** (sitting up, leaning forward, hyperextended chin) in an unimmunized child strongly indicates **epiglottitis**. - Given the risk of **complete airway obstruction**, securing the airway in a controlled environment like the **operating room** with specialized personnel (**anesthesia**, **ENT**) is the safest and most appropriate immediate step. *Nebulized albuterol* - This medication is a **bronchodilator** primarily used for conditions like **asthma** or **bronchiolitis** that involve bronchospasm. - It would not alleviate airway obstruction caused by supraglottic swelling in epiglottitis and could potentially worsen the child's distress. *Direct laryngoscopy and pharyngoscopy* - Performing a direct laryngoscopy or pharyngoscopy in the emergency department, especially without immediate intubation capabilities, could precipitate **laryngospasm** and **complete airway obstruction** in a child with suspected epiglottitis. - Visualization of the airway should only be attempted in a controlled setting where immediate intubation or tracheostomy can be performed. *Immediate nasotracheal intubation in the emergency department* - While intubation is necessary, attempting it immediately in the emergency department without the controlled environment of an operating room and without the full support of anesthesia and ENT specialists carries significant risks. - The swelling can make intubation extremely difficult and increase the likelihood of failed attempts or trauma, further compromising the airway. *Intravenous administration of antibiotics* - Although antibiotics are a crucial part of epiglottitis treatment (typically **ceftriaxone** or **cefotaxime** to cover *Haemophilus influenzae* type b), they are not the immediate priority. - The most urgent threat is airway compromise; therefore, securing the airway takes precedence over initiating antibiotic therapy.

Pharyngeal arches US Medical PG Question 5: A 6-year-old boy is brought in for evaluation by his adopted mother due to trouble starting 1st grade. His teacher has reported that he has been having trouble focusing on tasks and has been acting out while in class. His family history is unknown as he was adopted 2 years ago. His temperature is 36.2°C (97.2°F), pulse is 80/min, respirations are 20/min, and blood pressure 110/70 mm Hg. Visual inspection of the boy's face shows a low set nasal bridge, a smooth philtrum, and small lower jaw. Which of the following findings would also likely be found on physical exam?

• A. Cataracts
• B. Congenital deafness
• C. Holosystolic murmur (Correct Answer)
• D. Limb hypoplasia
• E. Wide notched teeth

Pharyngeal arches Explanation: **Holosystolic murmur** - The child exhibits classic features of **fetal alcohol syndrome** (FAS), including the distinctive facial anomalies (low set nasal bridge, smooth philtrum, small lower jaw) and developmental/behavioral issues (trouble focusing, acting out). - Up to 50% of children with FAS develop **congenital heart defects**, with **ventricular septal defects (VSDs)** being the most common, which are characterized by a **holosystolic murmur** at the lower left sternal border. *Cataracts* - **Cataracts** are not a typical feature of fetal alcohol syndrome but are often associated with congenital infections such as **rubella** or **cytomegalovirus**. - While some genetic syndromes can include cataracts, they are not a primary finding for the constellation of symptoms observed here. *Congenital deafness* - **Congenital deafness** is not a hallmark of fetal alcohol syndrome; rather, it is commonly associated with congenital infections like **rubella**, **CMV**, or genetic syndromes such as **CHARGE syndrome**. - Children with FAS may have hearing problems due to recurrent ear infections, but not typically congenital deafness. *Limb hypoplasia* - **Limb hypoplasia** is typically seen in conditions like **thalidomide embryopathy** or certain genetic syndromes, such as **Roberts syndrome**. - While growth restriction is common in FAS, significant limb hypoplasia as described is not a characteristic feature. *Wide notched teeth* - **Wide notched teeth**, also known as **Hutchinson teeth**, are pathognomonic for **congenital syphilis**. - This finding is unrelated to fetal alcohol syndrome, and the patient's other symptoms do not suggest congenital syphilis.

Pharyngeal arches US Medical PG Question 6: A 4-year-old boy is brought to the physician because of non-fluent speech. His mother worries that his vocabulary is limited for his age and because he cannot use simple sentences to communicate. She says he enjoys playing with his peers and parents, but he has always lagged behind in his speaking and communication. His speech is frequently not understood by strangers. He physically appears normal. His height and weight are within the normal range for his age. He responds to his name, makes eye contact, and enjoys the company of his mother. Which of the following is the most appropriate next step in management?

• A. Referral to speech therapist
• B. Evaluate response to methylphenidate
• C. Psychiatric evaluation
• D. Audiology testing (Correct Answer)
• E. Thyroid-stimulating hormone

Pharyngeal arches Explanation: ***Audiology testing*** - Before initiating any therapy for speech delay, it is crucial to rule out **hearing impairment**, as **undiagnosed hearing loss** is the most common organic cause of speech and language difficulties in children. - **Standard practice guidelines** (AAP) recommend hearing assessment as the **first diagnostic step** in evaluating any child with speech or language delay. - While other developmental aspects seem intact, the inability to use simple sentences at age 4 and speech that is "frequently not understood by strangers" strongly suggests the need to assess the child's ability to **receive auditory information**. *Referral to speech therapist* - While a **speech therapist referral** is highly appropriate for a child with significant speech delay, it should typically follow an assessment to rule out underlying organic causes like **hearing loss**. - Without addressing potential hearing impairment, speech therapy may be less effective or miss the root cause of the communication difficulty. *Evaluate response to methylphenidate* - **Methylphenidate** is a stimulant medication used primarily for **attention-deficit/hyperactivity disorder (ADHD)**. - There is no indication of ADHD symptoms in this child (e.g., inattention, hyperactivity, impulsivity), and it is not a treatment for **primary speech delay**. *Psychiatric evaluation* - The child's ability to respond to his name, make eye contact, and enjoy social interaction with family and peers makes a **primary psychiatric disorder** (like autism spectrum disorder) less likely to be the sole cause of the speech delay. - Such an evaluation would typically be considered if **social communication deficits**, repetitive behaviors, or restricted interests were prominent. *Thyroid-stimulating hormone* - **Hypothyroidism** can cause developmental delays, including speech delay. - However, the child's normal physical appearance, height, and weight make **congenital or acquired hypothyroidism** less likely to be the primary cause of his isolated speech delay.

Pharyngeal arches US Medical PG Question 7: An epidemiologist is evaluating the efficacy of Noxbinle in preventing HCC deaths at the population level. A clinical trial shows that over 5 years, the mortality rate from HCC was 25% in the control group and 15% in patients treated with Noxbinle 100 mg daily. Based on this data, how many patients need to be treated with Noxbinle 100 mg to prevent, on average, one death from HCC?

• A. 20
• B. 73
• C. 10 (Correct Answer)
• D. 50
• E. 100

Pharyngeal arches Explanation: ***10*** - The **number needed to treat (NNT)** is calculated by first finding the **absolute risk reduction (ARR)**. - **ARR** = Risk in control group - Risk in treatment group = 25% - 15% = **10%** (or 0.10). - **NNT = 1 / ARR** = 1 / 0.10 = **10 patients**. - This means that **10 patients must be treated with Noxbinle to prevent one death from HCC** over 5 years. *20* - This would result from an ARR of 5% (1/0.05 = 20), which is not supported by the data. - May arise from miscalculating the risk difference or incorrectly halving the actual ARR. *73* - This value does not correspond to any standard calculation of NNT from the given mortality rates. - May result from confusion with other epidemiological measures or calculation error. *50* - This would correspond to an ARR of 2% (1/0.02 = 50), which significantly underestimates the actual risk reduction. - Could result from incorrectly calculating the difference as a proportion rather than absolute percentage points. *100* - This would correspond to an ARR of 1% (1/0.01 = 100), grossly underestimating the treatment benefit. - May result from confusing ARR with relative risk reduction or other calculation errors.

Pharyngeal arches US Medical PG Question 8: A 23-year-old man comes to the physician for evaluation of decreased hearing, dizziness, and ringing in his right ear for the past 6 months. Physical examination shows multiple soft, yellow plaques and papules on his arms, chest, and back. There is sensorineural hearing loss and weakness of facial muscles bilaterally. His gait is unsteady. An MRI of the brain shows a 3-cm mass near the right internal auditory meatus and a 2-cm mass at the left cerebellopontine angle. The abnormal cells in these masses are most likely derived from which of the following embryological structures?

• A. Surface ectoderm
• B. Neural tube
• C. Neural crest (Correct Answer)
• D. Notochord
• E. Mesoderm

Pharyngeal arches Explanation: ***Neural crest*** - The patient's symptoms (bilateral sensorineural hearing loss, facial weakness, unsteady gait, central masses) along with cutaneous lesions (soft, yellow plaques) are highly suggestive of **Neurofibromatosis type 2 (NF2)**. - NF2 is characterized by **vestibular schwannomas** (acoustic neuromas) and other CNS tumors, which are derived from **Schwann cells**. Schwann cells, along with melanocytes and other peripheral nervous system components, originate from the **neural crest**. *Surface ectoderm* - The surface ectoderm forms structures such as the **epidermis**, hair, nails, and anterior pituitary. - While the skin lesions are present, the primary tumors (schwannomas) are not derived from the surface ectoderm. *Neural tube* - The neural tube gives rise to the **central nervous system** (brain and spinal cord) and motor neurons. - While the tumors affect the brain and cranial nerves, the specific cell type forming schwannomas (Schwann cells) does not originate directly from the neural tube. *Notochord* - The notochord induces the formation of the neural tube and eventually degenerates, contributing to the **nucleus pulposus** of the intervertebral discs. - It is not involved in the pathogenesis or cellular origin of schwannomas. *Mesoderm* - The mesoderm gives rise to connective tissues, blood, bone, muscle, and most internal organs. - While some tumors can have mesodermal origins, schwannomas are neuroectodermal in origin.

Pharyngeal arches US Medical PG Question 9: A 52-year-old woman sees you in your office with a complaint of new-onset headaches over the past few weeks. On exam, you find a 2 x 2 cm dark, irregularly shaped, pigmented lesion on her back. She is concerned because her father recently passed away from skin cancer. What tissue type most directly gives rise to the lesion this patient is experiencing?

• A. Neural crest cells (Correct Answer)
• B. Endoderm
• C. Mesoderm
• D. Ectoderm
• E. Neuroectoderm

Pharyngeal arches Explanation: ***Neural crest cells*** - The suspected lesion, given its description and the patient's family history of skin cancer, is likely a **melanoma**. - Melanoma originates from **melanocytes**, which are derived from **neural crest cells** during embryonic development. *Endoderm* - The endoderm gives rise to the **lining of the gastrointestinal and respiratory tracts**, as well as organs such as the liver and pancreas. - It is not involved in the formation of melanocytes or skin lesions like melanoma. *Mesoderm* - The mesoderm forms tissues such as **muscle, bone, cartilage, connective tissue**, and the circulatory system. - It does not directly give rise to melanocytes, which are the cells of origin for melanoma. *Ectoderm* - The ectoderm gives rise to the **epidermis, nervous system**, and sensory organs. - While melanocytes are found in the epidermis, they are specifically derived from the **neural crest (a sub-population of ectoderm)**, not the general ectoderm. *Neuroectoderm* - Neuroectoderm specifically refers to the ectoderm that develops into the **nervous system**. - While neural crest cells originate from the neuroectoderm, "neural crest cells" is a more precise answer for the origin of melanocytes.

Pharyngeal arches US Medical PG Question 10: A 29-year-old man presents to the emergency room with facial weakness. He first noticed that he was having trouble smiling normally while at dinner with friends the night before. He also noticed that his food had less taste than usual during the dinner. He woke up on the day of presentation with a complete inability to move the right side of his face. He recently returned from an extended camping trip in the Appalachian Mountains, but he did not find any tick bites following the camping trip. His past medical history is notable for Achilles tendonitis and carpal tunnel syndrome. He works as a computer programmer. He smokes marijuana occasionally but does not smoke cigarettes. His temperature is 98.6°F (37°C), blood pressure is 120/75 mmHg, pulse is 80/min, and respirations are 18/min. On exam, he is well-appearing in no acute distress. There is loss of facial wrinkles along the forehead, eyelids, and nasolabial folds. He is unable to completely close his right eye, raise his eyebrows, or smile with the right side of his mouth. Sensation is intact to light touch along the forehead, maxilla, and mandible bilaterally. Where is the most likely source of this patient’s lesion?

• A. Superior orbital fissure
• B. Petrotympanic fissure
• C. Inferior orbital fissure
• D. Dorsal frontal lobe
• E. Stylomastoid foramen (Correct Answer)

Pharyngeal arches Explanation: ***Stylomastoid foramen*** - The patient presents with classic signs of **Bell's palsy**, characterized by unilateral **facial weakness affecting both the upper and lower face**, including loss of forehead wrinkles, inability to close the eye, and loss of nasolabial folds. - The **stylomastoid foramen** is the exit point of the **facial nerve (CN VII)** from the skull, and inflammation or compression at this site is the most common cause of idiopathic facial nerve paralysis (Bell's palsy). *Superior orbital fissure* - Lesions in the **superior orbital fissure** would primarily affect cranial nerves **III, IV, V1, and VI**, leading to symptoms like ophthalmoplegia, ptosis, and sensory loss in the V1 distribution of the face, not a facial nerve palsy. - While it is a bony canal, it is not the primary exit for the facial nerve. *Petrotympanic fissure* - The **petrotympanic fissure** transmits the **chorda tympani nerve**, which carries taste sensation from the anterior two-thirds of the tongue and parasympathetic fibers to the submandibular and sublingual glands. - A lesion here would cause **loss of taste** and potentially dry mouth, but would not typically explain the extensive motor deficits of the entire ipsilateral face as seen in this patient, which indicates a more proximal or complete facial nerve involvement. *Inferior orbital fissure* - The **inferior orbital fissure** transmits the **maxillary nerve (V2)**, the zygomatic nerve, and branches of the inferior ophthalmic vein, affecting sensation to the mid-face. - Damage here would result in **sensory deficits in the V2 distribution** and potentially orbital symptoms, not motor weakness of the facial muscles. *Dorsal frontal lobe* - A lesion in the **dorsal frontal lobe**, specifically involving the **motor cortex**, would cause contralateral facial weakness. However, it would typically spare the forehead and eyelid muscles due to bilateral cortical innervation of the upper facial muscles. - The patient's presentation of **forehead and entire facial weakness** is characteristic of a **lower motor neuron lesion** of the facial nerve, not a central (upper motor neuron) lesion.

Pharyngeal arches Flashcard 1 of 10

Question: Which branchial arch gives rise to the maxillary process and mandibular process? _____

Answer: 1st arch

Pharyngeal arches Flashcard 2 of 10

Question: The branchial _____ are derivates of mesoderm + neural crest

Answer: arches

Pharyngeal arches Flashcard 3 of 10

Question: What branchial arch abnormality is characterized by cleft palate, airway obstruction, micrognathia, and glossoptosis?_____

Answer: Pierre Robin sequence

Pharyngeal arches Flashcard 4 of 10

Question: stapedius

Answer: 2nd arch

Pharyngeal arches Flashcard 5 of 10

Question: muscles of facial expression

Answer: 2nd arch

Pharyngeal arches Flashcard 6 of 10

Question: lesser horn of hyoid

Answer: 2nd arch

Pharyngeal arches Flashcard 7 of 10

Question: stylohyoid ligament

Answer: 2nd arch

Pharyngeal arches Flashcard 8 of 10

Question: corniculate

Answer: 4th-6th arches

Pharyngeal arches Flashcard 9 of 10

Question: cuneform

Answer: 4th-6th arches

Pharyngeal arches Flashcard 10 of 10

Question: pharyngeal constrictor muscles

Answer: 4th arch