UNSW Embryology

Beginnings, Growth and Development

© Dr Mark Hill (2009)

Acknowledgements

Practical: Embryology of the Face and Ear

5. Postnatal

Postnatal Ear

	Auditory Tube Eustachian, otopharyngeal or pharyngotympanic tube Connects middle ear cavity to nasopharynx portion of pharynx. Tube is normally closed and opened by muscles. Ventilation - pressure equalization in the middle ear Clearance - allow fluid drainage from the middle ear (More? Ear Cartoon 1 | Ear Cartoon 2)
Newborn to adult auditory tube Birth shorter (17-18 mm), narrower and runs almost horizontal Tube is opened by a single muscle, tensor palati muscle Adult longer (twice as long), wider and runs at approximately 45 degrees to the horizontal. Tube is opened by two separate muscles, tensor palati and levator palati

Hearing

The incidence of significant permanent hearing loss is approximately 1-3/1000 newborns. Neonatal hearing screening is carried out in several countries including the USA, UK and in Australia. In NSW the Statewide Infant Screening Hearing Program (SWISH) was introduced in 2002. There is also a general guide giving a timetable for a number of simple responses that a neonate should make if hearing has developed normally (More? Neonatal Hearing Check List). The two major forms of hearing loss are conductive and sensorineural.

State Wide Infant Screening Hearing Program (SWISH) a newborn hearing testing program using an automated auditory response technology (AABR). Program was introduced in NSW Australia in 2002 across 17 area health service coordinators. It is thought that in NSW 86,000 births/year = 86-172 babies potentially born with significant permanent hearing loss.

Automated Auditory Brainstem Response (AABR) uses a stimulus which is delivered through earphones and detected by scalp electrodes. The test takes between 8 to 20 minutes and has a sensitivity 96-99%.

Pharyngeal Abnormalities

The four different types of pharyngeal abnormalities are relatively rare.

• Sinuses - a pharyngeal groove defect, when a portion of the groove persists and opens to the skin surface, located laterally on the neck.
• Fistula - a pharyngeal membrane defect, a tract extends from pharynx (tonsillar fossa) beween the carotid arteries (internal and external) to open on side of neck.
• Cysts - a cervical sinus defect, remants of the cervical sinus remains as a fluid-filled cyst lined by an epithelium.
• Vestiges - cartilaginous or bony developmental remnants lies under the skin on side of neck.

First Arch Syndrome

There are 2 major types of first arch sydndrome, Treacher Collins and Pierre Robin, both result in extensive facial abnormalites. (More? Face Abnormalities).

Links: Medline Plus - Pierre Robin Syndrome | Medline Plus - Treacher Collins Syndrome

Embryo Cleft Lip and Palate

Human embryo primary palate cleft
(Carnegie stage 16, 18 and 19, images not to scale, Kyoto collection)

Cleft lip and palate develop between the 4th and 8th week of gestation and is dominated by changes resulting in the formation of the nose. Palatal development occurs between the 7th and 12th week of gestation and is divided into the formation of the primary palate (prolabium), premaxilla and cartilaginous septum) and formation of the secondary palate (hard and soft palate).

• 300+ different abnormalities
• different cleft forms and extent
• upper lip and ant. maxilla
• hard and soft palate

(More? Information about Cleft Palate | Cleft Lip | left Lip Classification | Repair)

Fetal Cleft Ultrasound Movies

Fetal facial clefting can be detected by ultrasound scans. The scan on the right is of an 18 week fetus. A common form of facial abnormality is that of cleft lip and palate. This is associated with the way in which the maxillary processes of the first pharyngeal arch must grow and fuse. Click the image or text link opens a new page with both the movie and a more detailed text description of features.

Facial Cleft 1 Ultrasound Movie

Clefting

The way in which the upper jaw forms from fusion of the smaller upper prominence of the first pharyngeal arch leads to a common congenital defect in this region called "clefting", which may involve either the upper lip, the palate or both structures. (More? Primary Palate | Face Abnormalities).
Cleft Lip International Classification of Diseases code 749.1 for isolated cleft lip and 749.2 for cleft lip with cleft palate. Australian national rate (1982-1992) 8.1 - 9.9 /10,000 births. Of 2,465 infants 6.2% were stillborn and 7.8% liveborn died during neonatal period. rate similar in singleton and twin births.
Cleft Palate International Classification of Diseases code 749.0 Australian national rate (1982-1992) 4.8 - 6 /10,000 births. Of 1,530 infants 5.5% were stillborn and 11.5% liveborn died during neonatal period. slightly more common in twin births than singleton. (Data: Congenital Malformations Australia 1981-1992 P. Lancaster and E. Pedisich ISSN 1321-8352)

Cleft Lip and Palate Classification

• unilateral incomplete - cleft on one side of the lip that does not extend into the nose.
• unilateral complete - cleft on one side of the lip that extends into the nose.
• bilateral complete - cleft that involves both sides of the lip and extends into and involves the nose.

Unilateral cleft lip and palate	Bilateral cleft lip and palate	Cleft palate

Fetal Alcohol Syndrome (FAS) Facial Appearance

The following facial features may be associated with FAS Microcephaly - leads to small head circumference Palpebral fissure - short opening of eye Epicanthal folds - fold of skin at inside of corner of eye Midface - flat Nasal Bridge - low Philtrum - Indistinct, vertical grooves between nose and mouth Upper Lip - thin Micrognathia - small jaw Ears - curve at top part of outer ear is underdeveloped and folded over parallel to curve beneath. Gives the appearance of a "railroad track" (More? Fetal Alcohol Syndrome)

FAS facial features (image modified from Wattendorf, 2005)

Cephalic Disorders

Cephalic (Greek, kephale = head) are a group of abnormalities that relate to a wide range of skeletal (skull) and neural (brain) associated defects. Listed below are some selected skull defects.

• Acephaly (absence of head)
• Exencephaly (brain outside skull)
• Macrocephaly (large head)
• Micrencephaly (small brain)
• Otocephaly (absence of lower jaw)
• Brachycephaly (premature fusion of coronal suture)
• Oxycephaly (premature fusion of coronal suture + other)
• Plagiocephaly (premature unilateral fusion of coronal or lambdoid sutures)
• Scaphocephaly (premature fusion of sagittal suture)

Next

This is the last page in today's practical class. There is an Additional Information page, that is not part of today's practical and is provided only for your own information and self-directed learning. Note that an unedited audio version of this practical has now been uploaded and is available here Embryology Face and Ear Audio 1:15:16 34 Mb. Please also read associated recording notes.

Glossary

Use the alphabetical list below to find definitions of terms that are new to you or use the Google search window to search UNSW Embryology site.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Terms

 

AABR - acronym for Automated Auditory Brainstem Response

adontia - Term used to describe the total lack of tooth development. (More? Integumentary Development - Tooth)

anacephaly - Neral developmental abnormality, incomplete development of cerebral hemispheres and cranium. Usually related to neural tube defect at the anterior (cranial) neuropore. (More? Neural Notes | Neural Abnormalities)

anosmia - Abnormality of having no sense of smell. (More? Smell | Sensory Notes)

cerumen - The ear wax which is secreted by apocrine glands in the ear canal (external auditory meatus). (More? Hearing Notes | Head Notes)

CHARGE Syndrome - Each letter sands for an associated disorder of the syndrome: Coloboma on the eye , Heart, Atresia of choane , Retardation of growth , Genital malformations, Ear malformations and/or deafness. CHARGE syndrome has an estimated birth incidence of 1 in 12,000 and is a common cause of congenital anomalies. Most affected individuals with CHARGE syndrome have mutations involving the chromodomain helicase DNA-binding protein-7

cleft - An anatomical gap or space occuring in abnormal development in or between structures. Most commonly associated with cleft lip and cleft palate. Term is also used to describe the groove that forms between each pharyngeal arch during their formation. (More? Face - Abnormalities | Face Notes | | Head Notes | Medline Plus - Cleft Lip and Palate)

cleft lip - An abnormality of face development leading to an opening in the upper lip. Clefting of the lip and or palate occurs with 300+ different abnormalities. Depending on many factors, this cleft may extend further into the oral cavity leading to a cleft palate. In most cases clefting of the lip and palate can be repaired by surgery. (More? Face - Abnormalities | Face Notes | | Head Notes | Medline Plus - Cleft Lip and Palate)

cleft palate - An abnormality of face development leading to an opening in the palate, the roof of the oral cavity between the mouth and the nose. Clefting of the lip and or palate occurs with 300+ different abnormalities. In most cases clefting of the lip and palate can be repaired by surgery. (More? Face - Abnormalities | Face Notes | | Head Notes | Medline Plus - Cleft Lip and Palate)

conductive loss - term used to describe one of the two major classes of hearing loss involving external and middle ear abnormalities (other form is Sensorineural loss).

craniofrontonasal syndrome - (CFNS) A human X-linked developmental disorder caused by a mutation in ephrin-B1 affecting mainly females. Characterised by abnormal development of cranial and nasal bones, craniosynostosis (premature coronal suture fusion), and other extracranial anomalies (limb polydactyly and syndactyly). (More? Musculoskeletal Development - Skull Development)

craniopharyngioma - A common destructive tumorogenic lesions of the hypothalamus and pituitary gland. Can occur when remnant cells from Rathke's pouch remain forming a tumour. (More? Endocrine - Hypothalamus | Endocrine - Pituitary )

craniosynostosis - The term describing the premature closure of the skull sutures, or fusion of skull bones. May cause skull and brain abnormalities. There are at least 8 different disorders with six related to the fibroblast growth factor receptor (FGFR); Pfeiffer syndrome, Apert syndrome, Crouzon syndrome, Beare-Stevenson syndrome, FGFR2-related isolated coronal synostosis, Jackson-Weiss syndrome, Crouzon syndrome with acanthosis nigricans (AN), and Muenke syndrome. (More? Head Notes | Head Abnormalities | Bone Notes | Bookshelf - GeneReviews)

critical period - (critical period of development) The term used to describe a developmental time when exposure to a teratogen can lead to a developmental abnormality, which can be further divided into an early major and later minor developmental abnormality. The defined critical period will differ in timing and length for different systems. (More? Abnormal Development - Environmental)

cyst - The pathological term describing a fibrous capsule containing fluid.

cytomegalovirus - An infection of early embryos is fatal, infection of later fetuses can lead to blindness, deafness, cerebral palsy, and mental retardation. (More? Abnormal Development- Virus)

endochondral ossification - (Greek, endon = within) The term used to describe the process of replacement of cartilage, which forms the first embryonic body skeleton, with bone. The osteoblasts are the bone-forming cells. (More? Musculoskeletal Development - Bone)

eustacian tube - (auditory tube) A narrow canal connecting the middle ear space to the back of the oral cavity. The direct physical connection has two main functions to allow pressure equalization in, and fluid drainage from, the middle ear. In development, the canal is initially both horizontal and very narrow leading to poor drainage and easy blockage (More? Hearing Notes | Abnormal Hearing Notes)

fistula - An abnormal communication between 2 structures (organs, vessels, cavities) that do not normally connect. (More? Head Abnormalities | Respiratory Abnormalities)

fontanel - (fontanelle) A fibrous region between flat bones of developing skull. Have a role in birth allowing the cranial vault to flex and postnatally allow the skull to enlarge. In humans, there are six fontanels; an obvious anterior (bregmatic) and posterior (occipital) fontanels, as well the less noticeable lateral fontanels (two mastoid fontanels and two sphenoidal fontanels). A month or two after birth, the posterior and lateral fontanelles are lost, the anterior is not completely closed until about the 18 months. (More? Musculoskeletal Development - Skull Development)

hard palate - he bony anterior portion of the palate formed by maxillary and palatine bones. The muscular posterior portion is called the soft palate. (More? Head Notes)

head circumference - An ultrasound measurement of Head Circumference (HC) is used to determine fetal age and normal development (small/large/abnormal) parameters. Measured as an ellipse in a horizontal section at the level of the thalamus and the cavum septi pellucidi. It is one of the four typical ultrasound assessments of fetal size and age: Biparietal Diameter (BPD), Head Circumference (HC), Abdominal Circumference (AC), and Femur Length (FL). (More? Ultrasound | Head Notes) | Fetal Notes | Birth Notes)

laryngeal webs - (congenital laryngeal webs) Laryngeal abnormality due to embryonic (week 10) incomplete recanalization of the laryngotracheal tube. Rare abnormality occuring mainly at the level of the vocal folds (glottis). (More? Respiratory Abnormalities)

lateral cervical anomaly - (branchial cleft anomaly) Abnormality which can be four different types: first, second, third and fourth. (More? Head Notes - Abnormalities)

meatoplasty - A surgical technique allowing reconstructive surgery of the external ear canal, often used to treat external meatus stenosis (More? Ear Abnormalities)

medial epithelial seam - (MES) Embryonic structure formed by the fusion of the two palatal shelves, forming a two-layered medial edge epithelial seam, which is then lost with palate development. (More? Face - Abnormalities | Face Notes | | Head Notes | Medline Plus - Cleft Lip and Palate)

metopic suture - A skull fibrous joint, cranial suture between adjacent developing bones of the skull. This suture begins at nose and runs superiorly to meet sagittal suture and fuses in early childhood before all other cranial sutures. Premature fusion (synostosis) of metopic suture causes Trigoncephaly (wedge skull). (More? Skull Notes | Head Notes)

microtia - The condition of an abnormally small external ear. (More? Abnormal Ear | Microtia)

mutagen - A chemical or agent that can cause permanent damage to the deoxyribonucleic acid (DNA) in a cell. DNA damage in the human egg or sperm may lead to reduced fertility, spontaneous abortion (miscarriage), birth defects and heritable diseases.

otitis media - The fluid in the middle ear accompanied by signs and symptoms of ear infection. Common developmental problem, prolonged or repeated occurance can lead to developmental delay in learning, speech and even damage to the middle ear structures. (More? Senses Notes | Hearing Abmnormalities)

palate - The roof of the mouth (oral cavity) a structure which separates the oral from the nasal cavity. Develops as two lateral palatal shelves which grow and fuse in the midline. Initally a primary palate forms with fusion of the maxillary processes with the nasal processes in early face formation. Later the secondary palate forms the anterior hard palate which will ossify and separate the oral and nasal cavities. The posterior part of the palate is called the soft palate (velum, muscular palate) and contains no bone. Abnormalities palatal shelf fusion can lead to cleft palate. (More? Face - Abnormalities | Face Notes | Head Notes | Medline Plus - Cleft Lip and Palate)

palatogenesis - The process of palate formation. (More? Face - Abnormalities | Face Notes | Head Notes | Medline Plus - Cleft Lip and Palate)

paranasal sinuses - Air-filled cavities surrounding the nasal cavity and open into it, which combine in function to: reduce skull weight, produce mucus, and act as resonating chambers affecting voice quality. Located within in the frontal, maxilae, ethmoid, and sphenoid bones with the same name as the bones in which they are located. (More? Respiratory Notes)

perinatal - the early postnatal period relating to the birth, statistically it includes the period up to 7 days after birth. (More? Normal Development - Birth)

prenatal screening sensitivity - (detection rate) Prenatal diagnostic test term describing the probability of testing positive on a prenatal screening test if the congenital anomaly is present. (More? Prenatal Diagnosis)

prenatal screening specificity - Prenatal diagnostic test term describing the probability of testing negative on a prenatal screening test if the congenital anomaly is absent. (More? Prenatal Diagnosis)

prevalence - A statistical term used mainly in studying disease/disorders and is a measure of the proportion of a population that are disease cases at a point in time. Generally used to measure only relatively stable conditions, not suitable for acute disorders. (More? Abnormal Development)

scaphocephalus - One of several skull deformities (scaphocephaly, oxycephaly, plagiocephaly, trigoncephaly) caused by premature fusion (synostosis) of different developing skull sutures. Scaphocephaly results from premature sagittal suture synostosis. (More? Skull Notes | Head Notes)

sensorineural – Term used to describe one of the two major classes of hearing loss involving the central pathway from the cochlear (other form is conductive loss).

soft palate - (velum, muscular palate) The muscular posterior portion of the palate forming the roof of the oral cavity. The bony anterior portion of the palate is called the hard palate, formed by maxillary and palatine bones. (More? Head Notes)

SWISH - Acronym for State Wide Infant Screening Hearing program. A newborn hearing testing program using an automated auditory response technology. Program was introduced in NSW Australia in 2002 across 17 area health service coordinators. (More? Hearing Notes | Hearing Abnormalities | Child Notes - Neonatal Screening | Child Notes - Neonatal Hearing Screening)

taste - sensory neurological perception of flavour begining with the taste buds of the tongue of at least five distinct qualities: sweet, bitter, sour, salty, and umami (savoury). (More? Sensory Notes - Taste)

tensor veli palatini - A muscle which functions to open the auditory tube by pulling its lateral wall laterally and inferiorly. (More? Hearing Notes)

teratogen - (Greek, teraton = monster) Any agent that causes a structural abnormality following exposure during pregnancy. The overall effect depends on dosage and time of exposure. Absolute risk - the rate of occurrence of an abnormal phenotype among individuals exposed to the agent. (e.g. fetal alcohol syndrome) Relative risk - the ratio of the rate of the condition among the exposed and the non-exposed. (e.g. smokers risk of having a low birth weight baby compared to non-smokers) A high relative risk may indicate a low absolute risk if the condition is rare. (More? Abnormal Development)

thyroid - (Greek, thyreos = sheild , eidos = form) endocrine gland located in the neck, the origin of the name reflects the organs anatomical structure. In the fetus, the thyroid gland has a role in neurological development. (More? Endocrine Notes | Thyroid Gland | Abnormal Development - Iodine Deficiency)

thyroiditis - (Greek, thyreos = sheild , eidos = form) An inflammatory process affecting the thyroid epithelium. (More? Endocrine Notes | Thyroid Gland | Abnormal Development - Iodine Deficiency)

tonotopy – term describing the mapping along the tectorial membrane within the cochlea of the different sound frequencies.

twinning - Term for more than a single pregnancy (singleton), the two major twinning forms are monozygotic (identical, from one fertilised egg and a single spermatazoa, 3-5 per 1000 pregnancies) or dizygotic (fraternal, from two eggs fertilised by two different spermatazoa). Late monozygotic twins can result in both a shared placenta and a shared amniotic sac (monochorionic monoamniotic twins). (More? Twinning)

VATER syndrome - A developmental abnormality, acronym for V (vertebral anomalies), A (anal atresia), TE (tracheo-esophageal fistula) and R (radial dysplasia). (V and R also include vascular and renal anomalies). Note that the acronym VACTERL syndrome now used, includes C (cardiac) and the L (limb anomalies). (More? Abnormal Development)

vocal folds - Folds occuring in the larynx used in generating sounds required for speech.

Waldeyer's ring - Historical name for the anatomical "ring" of lymphoid tissue in the pharynx (adenoids, tubal tonsils, palatine tonsils, lingual tonsils). Named after Heinrich Wilhelm Gottfried von Waldeyer-Hartz (1836 - 1921) a German anatomist.

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