1.2 - Embryology + Anamolies Flashcards
What is an Embryo?
2
The first stage of development in utero
Between fertilization and 8 weeks
What is a Fetus?
How does it differ from an embryo? (2)
In utero - between 8 weeks gestation to birth
//
Organs begin functioning
Genitalia are visible on ultrasound
How large is an embryo at 4 weeks?
2.5 mm
What are Somites on an embryo?
2
Bilaterally paired blocks of mesoderm
Gives rise to the vertebrae, rib cage, and part of the occipital bone; skeletal muscle, cartilage, tendons, and skin (of the back).
How big is a fetus at 6 weeks?
8 mm
What are the 3 Germ Layers? on an embryo
Ectoderm
Mesoderm
Endoderm
What is the Ectoderm on an embryo?
2
Outer layer
Forms central nervous system, peripheral nervous system, + epidermis
What is the Mesoderm on an embryo?
2
Middle layer
Forms connective tissue, cartilage, bone, striated + smooth muscles, heart, blood + lymph vessels, kidneys, gonads, and other organs
What is the Endoderm on an embryo?
2
Inner layer
Forms epithelial lining of organs, parenchyma of the tonsils + other organs, epithelial lining of tympanic cavity, auditory tube, and other organs
What is the Neural Tube on an embryo?
3
Tube located in middle of embryo
Precursor to Central Nervous System
Rostral end will become brain
What structures can we see on an Embryo between 3-4 weeks?
7
Frontonasal Prominence
Heart
Umbilical Cord
Pharyngeal Arches 1 + 2
Mandibular Arch already formed
Lungs
Limb Buds
What is the Frontonasal Prominence of an embryo?
When does it appear?
Two areas of thickened ectoderm under the fore-brain, one on either side
///
3rd week
What is contained in the Frontonasal Prominence of an embryo?
(3)
Olfactory pits
Nasal pits (will become nostrils)
Upper lip
How do the nasal pits/nostrils form (Frontonasal Prominence) on an embryo?
When does it appear?
Fusion of median + lateral nasal prominences
4th week
How is the upper lip formed (Frontonasal Prominence) on an embryo? (2)
When does it appear?
Fusion of maxillary + median
Merging of median nasal
//
7th week
What is the Maxillary Processes on an embryo?
When does it appear
Embryological structure which gives rise to the upper jaw elements (e.g., maxillary bone) of the developing face
4th week
How is the Maxillary Processes formed on an embryo?
3
They enlarge and grow ventrally and medially, surrounding the future oral cavity.
Grow rapidly, first meeting the lateral nasal processes, and then the lower extension of the medial nasal processes.
The lower extension will give rise to the midstructure (philtrum) of the upper lip.
What are the Mandibular Process on an embryo? (2)
What are they the first to do?
When do they appear?
Forms the lateral wall and base of the primitive mouth
Give rise to the mandible and the lower part of the face and tongue.
//
First to merge with each other at the mid line
//
7th week
How do ears appear on an embryo?
Ears appear lateral + posteriorly as low set ears
What is the Hyoid Arch on an embryo?
When does it appear?
Almost complete ring of tissue around the external auditory meatus
4th week
What comes together to form the Hard Palate on an embryo?
2
Premaxillae
2 Palatine processes (vertical orientation)
Are the Oral and Nasal Cavities separated in a embryo at 7 weeks?
(2)
No
Tongue is in both cavities
What are the Pharyngeal Arches on an embryo?
When do they appear?
Series of externally visible anterior tissue bands lying under the early brain that give rise to the structures of the head and neck
4th week
What is the Mandibular Arch?
When does it form?
First of the bronchial arches
4th week
What happens if there is an interruption to fetal development during week 6?
Cleft lip (+/- palate) will remain
What forms the Nasal Prominence in an embryo?
Fusion of the maxillary prominence
What forms the Philtrum in an embryo?
Merging of median nasal prominence along with inferior movement
What is Fusion?
Two separate processes unite and become one
What is Merging?
Underlayers “push” up epithelium to “fill in” structures
not a combining of two structures
What important structure develops during the 9th week of fetal development?
How does this occur? (3)
Palate
//
Fusion of shelves (palatine processes)
Starts anteriorly to posterior
Last thing to fuse is uvula (bifid uvula)
What kind of growth spurt occurs during the 9th week of fetal development?
What happens? (4)
Mandibular
//
Oral cavity enlarges
Tongue drops down
Palatine processes go from vertically oriented to horizontally oriented
Palatine processes head towards the midline
When can cleft be detected via ultrasound?
Around 13 weeks
What can any interruption in embryological development cause?
(1 + 6)
Major or minor malformations of the…
- Ears
- Eyes
- Tongue
- Teeth
- Jaw
- Hands/feet
What will major or minor structural malformations correlate to?
(1 + 6)
Issues with…
- Speech
- Hearing
- Resonance
- Mastication
- Vision
- Swallowing
- Etc.
What are 6 anomalies that can affect the Ears?
Aural atresia/Auditory atresia
Microtia
Preauricular pits/preauricular tags
Otitus media
Otitus media with effusion
Oorrhea (drainage)
What is Aural Atresia/Auditory Atresia?
3
Congenital abnormality
Closure of external auditory canal.
EA canal and tympanic membrane may be small or fail to develop
What is Microtia?
3
Malformation of pinna
Greater deformity of outer ear
Increased likelihood of problems with middle ear or ossicles
What are Preauricular Pits/Preauricular Tags?
2
Projection of scalp or skin tags
From ear to cheek
What are 10 anomalies that can affect the Eyes?
Epibulbar dermoid
Epicanthal folds
Exophthalmos
Hypertelorism
Coloboma
Palpebral fissures
Ptosis
Myopia
Hyperopia
Strabismus
What is Epibulbar Dermoid?
Cyst on the retina
What are Epicanthal Folds?
Skin fold of the upper eyelid covering the inner corner of the eye
What is Exophthalmos?
3
Bulging of the eyes
Protrusion of 1 or both eyes
Beyond socket d/t congenital or pathological defect
What is Hypertelorism?
2
Excessive distance between 2 organs specifically the eyes
Typically presents as widely-set eyes
What is Coloboma?
3
Congenital defect of the eye
Notch of eyelid margins
Most often affects lower lid
What is Palpebral Fissures?
2
Opening between the eyelids
Narrow palpebral fissures = Velocardiofacial Syndrome (VCFS)
What is Ptosis?
Drooping or falling of the upper eyelid
What is Myopia?
Nearsightedness
What is Hyperopia?
Farsightedness
What is Strabismus?
2
Inability of 1 eye to attain binocular vision with other
Due to imbalance of the muscles of eye
(a.k.a., “lazy eye”)
What are 5 anomalies that can affect the Tongue?
Microglossia
Macroglossia
Ankyloglossia
Glossopexy
Glossoptosis
What is Microglossia?
Small or absent tongue/genioglossus muscle
What is Macroglossia?
Enlarged tongue
What is Ankyloglossia?
4
Tongue tied
Short lingual frenulum
Anterior tongue attachment
Restricts movement of tongue tip
What is Glossopexy?
Tongue-lip adhesion
What is Glossoptosis?
2
Downward displacement or retraction of the tongue
Displacement of the tongue toward the pharynx
What are 3 anomalies that can affect the Jaw?
Micrognathia
Prognathia
Retrognathia
What is Micrognathia/Retrognathia?
What disorder is this commonly seen in?
Small or hypoplastic mandible
Pierre Robin Sequence
What is Prognathia?
Large or protrusive mandible
Caused by mandibular hyperplasia
What are 3 anomalies that can affect the Hands/Feet?
Polydactyly
Syndactyly
Brachydactyly
What is Polydactyly?
Extra fingers/toes
What is Syndactyly?
Fusion or webbing of digits
What is Brachydactyly?
Abnormally short digits
What are 5 anomalies that can affect the Cranium, Midface, and/or Palate?
Craniosynostosis
Microcephaly
Macrocephaly
Malar Hypoplasia
Cleft Palate
What is Microcephaly?
Small head circumference in comparison to age/sex matched peers
What is Macrocephaly?
Large head circumference in comparison to age/sex matched peers
What is Malar/Midface Hypoplasia?
3
Underdevelopment of the maxilla
In length (decreased midface height) or depth (retrusion of the maxilla)
In the presence of normal mandible size,
midface retrusion may give the appearance of prognathism
What is Craniosynostosis?
3
Premature fusion of cranial sutures
Growth is restricted perpendicular to
the suture that is closed prematurely.
Requires craniotomy and skull reshaping
What syndromes are associated with Craniosynostosis?
4
Seathre-Chotzen Syndrome
Crouzon Syndrome
Apert Syndrome
Pfeiffer Syndrome
