Branchial Apparatus and Aortic Arches

The branchial arches, also known as pharyngeal or visceral arches, are embryonic structures seen in the development of vertebrates that serve as precursors for many structures of the face, neck, and head. These arches are composed of a central core of mesoderm, which is covered externally by ectoderm Ectoderm The outer of the three germ layers of an embryo. Gastrulation and Neurulation and internally by endoderm Endoderm The inner of the three germ layers of an embryo. Gastrulation and Neurulation. Indentations between arches are known as the pharyngeal clefts, or grooves, externally and the pharyngeal pouches internally. Each pharyngeal arch contains cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage and muscular components, which are supplied by a cranial nerve (derived from neural crest cells), and an artery, known as a pharyngeal aortic arch. Some of these aortic arches go on to form the great vessels near the heart.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Review of Early Embryologic Development

Blastocyst and bilaminar disc

The morula (ball of cells) undergoes a process called blastulation, in which a cavity begins to form. The cells then begin differentiating into outer and inner cell masses.

  • Outer cell mass → trophoblast Trophoblast Cells lining the outside of the blastocyst. After binding to the endometrium, trophoblasts develop into two distinct layers, an inner layer of mononuclear cytotrophoblasts and an outer layer of continuous multinuclear cytoplasm, the syncytiotrophoblasts, which form the early fetal-maternal interface (placenta). Fertilization and First Week placenta Placenta The placenta consists of a fetal side and a maternal side, and it provides a vascular communication between the mother and the fetus. This communication allows the mother to provide nutrients to the fetus and allows for removal of waste products from fetal blood. Placenta, Umbilical Cord, and Amniotic Cavity and membranes
  • Inner cell mass → embryoblast → bilaminar disc:
    • Epiblast
    • Hypoblast
  • Amniotic sac: cavity of fluid that develops “above” the epiblast (between epiblast and trophoblast Trophoblast Cells lining the outside of the blastocyst. After binding to the endometrium, trophoblasts develop into two distinct layers, an inner layer of mononuclear cytotrophoblasts and an outer layer of continuous multinuclear cytoplasm, the syncytiotrophoblasts, which form the early fetal-maternal interface (placenta). Fertilization and First Week)
  • Primitive yolk sac: cavity that forms “below” the hypoblast (between hypoblast and trophoblast Trophoblast Cells lining the outside of the blastocyst. After binding to the endometrium, trophoblasts develop into two distinct layers, an inner layer of mononuclear cytotrophoblasts and an outer layer of continuous multinuclear cytoplasm, the syncytiotrophoblasts, which form the early fetal-maternal interface (placenta). Fertilization and First Week)

Trilaminar disc

The bilaminar disc undergoes a process called gastrulation Gastrulation Both gastrulation and neurulation are critical events that occur during the 3rd week of embryonic development. Gastrulation is the process by which the bilaminar disc differentiates into a trilaminar disc, made up of the 3 primary germ layers: the ectoderm, mesoderm, and endoderm. Gastrulation and Neurulation to form the trilaminar disc. Cells from the epiblast layer migrate downward, replacing the hypoblast ( endoderm Endoderm The inner of the three germ layers of an embryo. Gastrulation and Neurulation) and creating a 3rd layer in between (mesoderm). 

  • Ectoderm (dorsal layer):
    • Continuous with the amnion 
    • Formed from cells remaining in the epiblast layer
    • Ectoderm-derived structures:
      • Neural tube → brain and spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord
      • Neural crest cells → cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. Overview of the Cranial Nerves associated with the branchial arches, PNS
  • Mesoderm (middle layer) has several components:
    • Paraxial mesoderm → forms the mesodermal component of the branchial arches
    • Intermediate mesoderm → genitourinary system
    • Lateral plate mesoderm (LPM): 
      • Somatic layer of the LPM 
      • Splanchnic layer of the LPM → forms primitive heart tube and pharyngeal aortic arches
    • Extraembryonic mesoderm:
      • Surrounds the amniotic cavity → continuous with somatic LPM
      • Surrounds the yolk sac → continuous with splanchnic LPM
  • Endoderm (ventral layer):
  • Folding of the trilaminar disc (folds in 2 directions):
    • Lateral folding: 
    • Cranial–caudal folding: 
      • Creates a cranial end and a caudal end ( embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week becomes bean-shaped)
      • Forces the yolk sac farther from the body. The elongating stalk connecting the yolk sac to the gut tube is the vitelline duct.

Origin and Structure of the Branchial Apparatus

Development of the branchial apparatus

The branchial (meaning “gills”) apparatus is also known as the pharyngeal apparatus in humans.

  • Occurs in the 4th–5th embryonic week
  • In humans, 5 arch-shaped bulges or folds form off the ventral side of the foregut (part of the primitive gut tube) in the region that will become the head and neck.
    • Named branchial arches I–VI 
      • Arches I, II, III, IV, and VI exist in humans
      • Arch V does not exist in humans; it is a structure in other vertebrates (e.g., fish).
      • 4th and 6th arches fuse → results in 4 total pharyngeal arches
    • Each of the arches consists of all 3 germ layers:
      • Endoderm: internal layer
      • Mesoderm: central core
      • Ectoderm: external layer
  • Mesenchymal cells migrate downward (ventrally) from the paraxial mesoderm, surrounding the endoderm Endoderm The inner of the three germ layers of an embryo. Gastrulation and Neurulation-derived foregut:
    • Form the lateral wall of the digestive tract 
    • Continue to proliferate in the cranial portion of the tube forming the mesodermal core of the branchial arches
  • Associated with each arch is:
    • A cranial nerve (nerve supply)
    • A pharyngeal aortic arch (blood supply)
  • Arches are separated:
    • Externally by pharyngeal clefts, also called pharyngeal grooves:
    • Internally by pharyngeal pouches 
  • Different segments of the tube have different patterns of gene expression → triggers various differentiations of each groove/arch/pouch

Structure and derivatives of the branchial apparatus

  • Pharyngeal clefts (also called pharyngeal grooves): 
    • 4 indentations of ectoderm Ectoderm The outer of the three germ layers of an embryo. Gastrulation and Neurulation located on the external surface of the structure
    • Becomes external epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium 
  • Pharyngeal arches:
    • 4 cores of mesoderm located in the middle of the structure
    • Become:
      • Cartilage and connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue
      • Muscle
      • Bones
    • Also contain:
      • Nerves
      • Arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries
  • Pharyngeal pouches:
    • 4 indentations of endoderm Endoderm The inner of the three germ layers of an embryo. Gastrulation and Neurulation located on the internal surface of the structure
    • Become:
      • Internal epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium
      • Glands

Development of the Pharyngeal Arches

Development of the pharyngeal arches

The pharyngeal arches develop into key components of the head and neck.

  • Each arch contains a core of dense mesenchyme that develops into:
    • Cartilage rod → bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones via endochondral ossification
    • Muscles
    • Connective tissue
  • Somitomeres:
    • Segmented muscular tissue from paraxial mesoderm located on either side of the neural tube
    • Migrate into the developing arches
    • Associate with developing cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage there
  • Branchial nerves:
    • Derived from neural crest cells, which are originally located dorsal to the neural tube
    • Migrate with the somitomeres down into the developing mesenchymal tissue of the pharyngeal arches
    • Develop into the cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. Overview of the Cranial Nerves innervating the muscles simultaneously developing within each arch
  • Blood supply is via the associated branchial aortic arches.
Derivatives of the pharyngeal arches and associated cranial nerves

Derivatives of the pharyngeal arches and their associated cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. Overview of the Cranial Nerves (CNs)

Image by Lecturio.

Derivations and associations of each pharyngeal arch

Table: Derivations of each pharyngeal arch
Arch Cartilage element Musculature Nerve
1st
  • Temporal bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones
  • Maxillary bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones
  • Zygomatic Zygomatic Either of a pair of bones that form the prominent part of the cheek and contribute to the orbit on each side of the skull. Skull bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones
  • Mandible bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones
  • Malleus and incus (1st 2 ossicles in the inner ear)
  • Muscles of mastication
  • Digastric muscle (anterior belly)
  • Mylohyoid muscle
  • Tensor tympani muscle
  • Tensor veli palatini muscle
CN V: mandibular branch of the trigeminal nerve
2nd
  • Lesser horn and body of the hyoid
  • Stapes (3rd ossicle)
  • Styloid process
  • Stylohyoid ligament
  • Muscles of facial expression
  • Digastric muscle (posterior belly)
  • Stylohyoid muscle
  • Stapedius muscle (inner ear)
CN VII: facial nerve
3rd Greater horn of the hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones Stylopharyngeus muscle CN IX: glossopharyngeal nerve
4th/6th
  • Thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
  • Cricoid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
  • Arytenoid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage
  • Muscles of the palate Palate The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. Oral Cavity: Palate, pharynx Pharynx The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. Pharynx, and larynx Larynx The larynx, also commonly called the voice box, is a cylindrical space located in the neck at the level of the C3-C6 vertebrae. The major structures forming the framework of the larynx are the thyroid cartilage, cricoid cartilage, and epiglottis. The larynx serves to produce sound (phonation), conducts air to the trachea, and prevents large molecules from reaching the lungs. Larynx
  • Cricothyroid muscle
  • Constrictor muscle of the pharynx Pharynx The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. Pharynx
  • Levator veli palatini muscle
CN X: vagus nerve
  • 4th arch: superior laryngeal nerve
  • 6th arch: recurrent laryngeal nerve

Pharyngeal Aortic Arches

Each branchial arch has its own pair of branchial arch arteries; there are 5 aortic arches in humans.

Early development

  • Primitive heart tube forms from the splanchnic layer of the LPM in the first 3 weeks of development.
  • Vasculogenesis causes the superior portion of the primitive heart tube to split into:
    • Pulmonary trunk
    • Aortic sac
  • Pharyngeal aortic arches:
    • Originate as paired vessels from the aortic sac 
    • Wrap around the developing gut tube
    • Lead into the 2 paired dorsal aortas running longitudinally along the embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week (dorsal aortas merge caudally into the descending aorta)
  • A total of 5 pairs of arches develop in humans:
    • The most cranial arches develop 1st (and regress)
    • Caudal arches develop later

Pharyngeal aortic arch derivatives

  • 1st and 2nd aortic arches: mostly regress 
    • 1st arch → maxillary artery
    • 2nd arch → stapedial artery (often degenerates completely, persists in a minority of individuals)
  • 3rd aortic arch: common and internal carotid arteries:
  • 4th aortic arch:
    • Left → the defined aortic arch
    • Right → proximal section of the right subclavian artery
  • 5th aortic arch: does not develop in humans
  • 6th aortic arch: pulmonary arch
    • Left: 
      • Left pulmonary artery
      • Ductus arteriosus 
    • Right:
      • Pulmonary trunk 
      • Right pulmonary artery
Diagram: pharyngeal aortic arches

Diagram depicting formation, regression, and differentiation of the pharyngeal aortic arches

Image by Lecturio.

Development of the Pharyngeal Clefts and Pouches

Pharyngeal clefts (pharyngeal grooves)

The pharyngeal clefts are created by the invaginations of ectoderm Ectoderm The outer of the three germ layers of an embryo. Gastrulation and Neurulation on the external between the pharyngeal arches.

  • Only 1 of the 4 ectodermal pharyngeal clefts develops into a definite organ system.
  • 1st pharyngeal cleft becomes:
    • External auditory canal
    • External surface of the tympanic membrane
  • 2nd pharyngeal cleft:
    • Proliferates and grows caudally
    • Grows “over” the 3rd and 4th pharyngeal clefts
    • Merges with the epicardial ridge → forms the cervical sinus (lined by ectoderm Ectoderm The outer of the three germ layers of an embryo. Gastrulation and Neurulation): 
      • Later degenerates 
      • If degeneration fails, lateral branchial cleft cysts may develop.
  • 3rd and 4th pharyngeal clefts:
    • Form the medial lining of the cervical sinus
    • Ultimately degenerate
Development of the pharyngeal clefts

Development of the pharyngeal clefts

Image by Lecturio.

Development of the Pharyngeal Pouches

The pharyngeal pouches are created by the internal invaginations of endoderm Endoderm The inner of the three germ layers of an embryo. Gastrulation and Neurulation between the pharyngeal arches.

  • 1st pharyngeal pouch:
    • Tympanic cavity (i.e., middle ear cavity)
    • Auditory or eustachian tube (draining the middle ear into the nasal cavity)
  • 2nd pharyngeal pouch: tonsils
  • 3rd pharyngeal pouch: splits into dorsal and ventral components:
    • Dorsal sprout → inferior parathyroid glands Parathyroid glands The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Parathyroid Glands (start higher and move down)
    • Ventral sprout → thymus Thymus A single, unpaired primary lymphoid organ situated in the mediastinum, extending superiorly into the neck to the lower edge of the thyroid gland and inferiorly to the fourth costal cartilage. It is necessary for normal development of immunologic function early in life. By puberty, it begins to involute and much of the tissue is replaced by fat. Lymphatic Drainage System (starts in the neck and moves down into the chest)
  • 4th pharyngeal pouch: splits into dorsal and ventral components:
    • Dorsal sprout → superior parathyroid glands Parathyroid glands The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Parathyroid Glands (start lower and move up)
    • Ventral sprout → ultimobranchial body (sometimes attributed to a 5th pharyngeal pouch) → calcitonin-producing parafollicular or C cells of the thyroid gland Thyroid gland The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Thyroid Gland
Development of the pharyngeal pouches

Development of the pharyngeal pouches

Image by Lecturio.

Clinical Relevance

1st and 2nd arch syndromes

  • Treacher-Collins syndrome: underdevelopment of the jaw Jaw The jaw is made up of the mandible, which comprises the lower jaw, and the maxilla, which comprises the upper jaw. The mandible articulates with the temporal bone via the temporomandibular joint (TMJ). The 4 muscles of mastication produce the movements of the TMJ to ensure the efficient chewing of food. Jaw and Temporomandibular Joint (micrognathia) and deformity of the zygomatic bones, the ossicles, and the external ears (results in hearing problems). Genetic mutations resulting in too few neural crest cells can cause a deficiency of neural crest cells migrating to the 1st pharyngeal arch, leading to a shortage of cells required to create these structures.
  • Pierre-Robin sequences: Underdevelopment of the jaw Jaw The jaw is made up of the mandible, which comprises the lower jaw, and the maxilla, which comprises the upper jaw. The mandible articulates with the temporal bone via the temporomandibular joint (TMJ). The 4 muscles of mastication produce the movements of the TMJ to ensure the efficient chewing of food. Jaw and Temporomandibular Joint (possibly due to positioning and/or compression in utero) leads to a more posterior position of the tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Oral Cavity: Lips and Tongue, which in turn leads to an inability of the palate Palate The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. Oral Cavity: Palate to close (resulting in cleft palate cleft palate The embryological development of craniofacial structures is an intricate sequential process involving tissue growth and directed cell apoptosis. Disruption of any step in this process may result in the formation of a cleft lip alone or in combination with a cleft palate. As the most common craniofacial malformation of the newborn, the diagnosis of a cleft is clinical and usually apparent at birth. Cleft Lip and Cleft Palate).
  • Agnathia: rare condition in which the lower jaw Jaw The jaw is made up of the mandible, which comprises the lower jaw, and the maxilla, which comprises the upper jaw. The mandible articulates with the temporal bone via the temporomandibular joint (TMJ). The 4 muscles of mastication produce the movements of the TMJ to ensure the efficient chewing of food. Jaw and Temporomandibular Joint fails to form entirely.
  • Goldenhar syndrome: combined malformation of the 1st and 2nd branchial arch of unknown etiology leading to abnormalities primarily affecting the eyes, ears, and spine. Presentation is with asymmetrical facial anomalies, including malformations of the outer ear (e.g., microtia, anotia), ocular tumors or dermoids, underdeveloped facial bones and muscles, and spine abnormalities. Other anomalies of the heart, kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys, lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs, and limbs are also possible. 

3rd and/or 4th arch conditions

  • DiGeorge syndrome DiGeorge syndrome DiGeorge syndrome (DGS) is a condition caused by a microdeletion at location q11.2 of chromosome 22 (thus also called 22q11.2 syndrome). There is a defective development of the third and fourth pharyngeal pouches, leading to thymic and parathyroid hypoplasia (causing T-cell immunodeficiency and hypocalcemia, respectively). DiGeorge Syndrome: result of a 22q11.2 chromosomal microdeletion that causes abnormal formation of the 3rd and 4th pharyngeal pouches. This formation results in frequent infections from thymic hypoplasia, hypocalcemia Hypocalcemia Hypocalcemia, a serum calcium < 8.5 mg/dL, can result from various conditions. The causes may include hypoparathyroidism, drugs, disorders leading to vitamin D deficiency, and more. Calcium levels are regulated and affected by different elements such as dietary intake, parathyroid hormone (PTH), vitamin D, pH, and albumin. Presentation can range from an asymptomatic (mild deficiency) to a life-threatening condition (acute, significant deficiency). Hypocalcemia (from abnormal parathyroid development), cleft palate cleft palate The embryological development of craniofacial structures is an intricate sequential process involving tissue growth and directed cell apoptosis. Disruption of any step in this process may result in the formation of a cleft lip alone or in combination with a cleft palate. As the most common craniofacial malformation of the newborn, the diagnosis of a cleft is clinical and usually apparent at birth. Cleft Lip and Cleft Palate, abnormal facies (such as micrognathia and low-set ears), and cardiac defects (including, potentially, a tetralogy of Fallot Tetralogy of Fallot Tetralogy of Fallot is the most common cyanotic congenital heart disease. The disease is the confluence of 4 pathologic cardiac features: overriding aorta, ventricular septal defect, right ventricular outflow obstruction, and right ventricular hypertrophy. Tetralogy of Fallot, ventricular septal defect, and/or truncus arteriosus Truncus arteriosus Truncus arteriosus (TA) is a congenital heart defect characterized by the persistence of a common cardiac arterial trunk tract that fails to divide into the pulmonary artery and aorta during embryonic development. Truncus arteriosus is a rare congenital malformation with a high mortality rate within the 1st 5 weeks of life if not managed promptly. Truncus Arteriosus).
  • Lateral branchial cysts and fistulas: If the cervical sinus persists, lateral branchial cleft cysts form. These cysts are generally benign, but they can be bothersome. Fistulas can also form between these cysts, either with an external opening (usually at the anterior edge of the sternocleidomastoid muscle) and/or an internal opening (leading into the supratonsillar fossa, which may result in bad breath).

References

  1. Miles, B. (2021). Embryology, pharyngeal pouch. StatPearls. Retrieved Nov 1, 2021, from https://www.statpearls.com/articlelibrary/viewarticle/89854/ 
  2. Isaacson, G. C. (2019). Congenital anomalies of the jaw, mouth, oral cavity, and pharynx. UpToDate. Retrieved Nov 2, 2021, from https://www.uptodate.com/contents/congenital-anomalies-of-the-jaw-mouth-oral-cavity-and-pharynx

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