EMBRYO Flashcards
Fetal landmarks Day 0
Fertilization by sperm, initiating embryogenesis
Fetal landmarks Within week 1
Implantation (as a blastocyst)
Fetal landmarks Within week 2
Bilaminar disk (epiblast:hypoblast).
Fetal landmarks Within week 3
Gastrulation. Primitive streak, notochord, and neural plate begin to form
Fetal landmarks Weeks 3–8 wk
Neural tube formed. Organogenesis. Extremely susceptible to teratogens.
Fetal landmarks Week 4
Heart begins to beat: 4 chambers in week 4. Upper and lower limb buds begin to form.
Fetal landmarks Week 8
Fetal movement; fetus looks like a baby.
Fetal landmarks Week 10
Genitalia have male/female characteristics.
Fetal landmarks plates with functions
Alar plate - Sensory Basal plate - Motor
Embryologic derivatives Neural crest
ANS, dorsal root ganglia, melanocytes, chromaffin cells of adrenal medulla, enterochromaffin cells, pia and arachnoid, celiac ganglion, Schwann cells, odontoblasts, parafollicular (C) cells of thyroid, laryngeal cartilage, bones of the skull
Embryologic derivatives Endoderm
Gut tube epithelium and derivatives (e.g., lungs, liver, pancreas, thymus, parathyroid, thyroid follicular cells).
Fetal landmarks first week
Fertilization - day 1 Zygote - day 2 Morula - day 3 blastocyst - day 5 implantation - day 6
Embryologic derivatives Mesoderm
Dura mater, connective tissue, muscle, bone, cardiovascular structures, lymphatics, blood urogenital structures, serous linings of body cavities (e.g., peritoneal), spleen, adrenal cortex, kidneys.
Embryologic derivatives Notochord
Induces ectoderm to form neuroectoderm (neural plate). Its only postnatal derivative is the nucleus pulposus of the intervertebral disk.
Teratogens effect/cause Alcohol
Birth defects and mental retardation (leading cause); fetal alcohol syndrome
Teratogens effect/cause ACE inhibitors
Renal damage
Teratogens effect/cause
Abnormal fetal development and fetal addiction
Cocaine
Teratogens effect/cause Diethylstilbestrol (DES)
Vaginal clear cell adenocarcinoma
Teratogens effect/cause Iodide
Congenital goiter or hypothyroidism
Teratogens effect/cause 13-cis-retinoic acid
Extremely high risk for birth defects (hearing and visual impairment, missing earlobes, facial dysmorphism, and mental retardation)
Tetarogens effect/cause Thalidomide
Limb defects (“flipper” limbs)
Teratogens effect/cause
Tobacco
Preterm labor, placental problems, attention-deficit hyperactivity disorder (ADHD)
Teratogens effect/cause Warfarin
multiple
Teratogens effect/cause anticonvulsants
multiple
Teratogens effect/cause Xrays
multiple
FAS
what are the defects
craniofacial abnormalities microcephaly
limb dislocation heart and lung fistulas
FAS mech
unknown, but may include inhibition of cell migration
Rule of 2’s for 2nd week
- -2 germ layers (bilaminar disk): epiblast, hypoblast. –2 cavities: amniotic cavity, yolk sac.
- -2 components to placenta: cytotrophoblast, syncytiotrophoblast.
The epiblast
precursor to what and what it does/forms
(precursor to ectoderm) invaginates to form primitive streak. Cells from the primitive streak give rise to both intraembryonic mesoderm and endoderm.
Rule of 3’s for 3rd week
3 germ layers (gastrula): ectoderm, mesoderm, endoderm.
Embryologic derivatives Neuroectoderm
Neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland.
Embryologic derivatives Surface ectoderm
Adenohypophysis; lens of eye; epithelial linings of skin, ear, eye, and nose; epidermis.
Branchial apparatus
different parts and what they are from
Branchial clefts are derived from ectoderm. Branchial arches are derived from mesoderm and neural crests. Branchial pouches are derived from endoderm.
Branchial apparatus aka/s
Branchial apparatus is also called pharyngeal apparatus. Clefts are also called grooves
Branchial apparatus layers
CAP covers outside from inside
Clefts = ectoderm, Arches = mesoderm, Pouches = endoderm
Branchial arch 1 derivatives cartilage
Meckel’s cartilage, Mandible,
Malleus, incus, sphenoMandibular ligament.
Branchial arch 1 derivatives muscles
Muscles: Muscles of Mastication (temporalis, Masseter, lateral and Medial pterygoids) Mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini, anterior 2⁄3 of tongue.
Branchial arch 1 derivatives nerves
Nerve: CN V2 and CN V3
Branchial arch 2 derivatives cartilage
Reichert’s cartilage: Stapes, Styloid process, lesser horn of hyoid, Stylohyoid ligament.
Branchial arch 2 derivatives muscle
Muscles: muscles of facial expression, Stapedius, Stylohyoid, posterior belly of digastric.
Branchial arch 2 derivatives nerves
Nerve: CN VII.
Branchial arch 3 derivatives cartilage
Cartilage: greater horn of hyoid.
Branchial arch 3 derivatives muscle
Muscle: stylopharyngeus.
Branchial arch 3 derivatives nerves
Nerve: CN IX
Branchial arch 4,6 derivatives cartilages
Cartilages: thyroid, cricoid, arytenoids, corniculate, cuneiform.
Branchial arch 4 derivatives muscle
Muscles (4th arch): most pharyngeal constrictors, cricothyroid, levator veli palatini.
Branchial arch 4 derivatives nerves
Nerve: 4th arch––CN X (superior laryngeal branch);
Branchial arch 6 derivatives muscles
Muscles (6th arch): all intrinsic muscles of larynx except cricothyroid.
Branchial arch 6 derivatives nerves
6th arch––CN X (recurrent laryngeal branch).
Which Branchial arch
form posterior 1/3 of tongue.
Arches 3 and 4
which Branchial arch
makes no major developmental contributions.
Arch 5
Branchial arch innervation and implications
Arch 1 – CN V2 and V3. Arch 2 – CN VII. Arch 3 – CN IX. Arch 4 and 6 –CN X.
with the exception of V2(no motor) these are the only CN’s that have both sensory and motor components
Branchial cleft derivatives 1st
1st cleft develops into external auditory meatus.
Branchial cleft derivatives 2nd-4th
2nd through 4th clefts form temporary cervical sinuses which are obliterated by proliferation of 2nd arch mesenchyme.
Persistent cervical sinus can lead to
what and where
a branchial cyst in the lateral neck.
Thyroglossal duct cyst in midline neck.
Ear development Bones
Malleus/incus–– 1st arch Stapes––2nd arch
Ear development Muscles
Tensor tyMpani (V3)––1st arch Stapedius (VII)––2nd arch
Branchial pouch derivatives 1st pouch
middle ear cavity, eustachian tube, mastoid air cells.
Branchial pouch derivatives 2nd pouch
develops into epithelial lining of palatine tonsil.
Branchial pouch derivatives 3rd pouch
3rd pouch (dorsal wings) develops into inferior parathyroids. 3rd pouch (ventral wings) develops into thymus
Branchial pouch derivatives develops into thymus.
3rd pouch (ventral wings)
Branchial pouch derivatives
develops into superior parathyroids.
4th pouch
Branchial pouch Aberrant development of 3rd
and 4th pouches →
DiGeorge syndrome
Cleft lip
failure of fusion of the maxillary and medial nasal processes (formation of 1° palate).
failure of fusion of the maxillary and medial nasal processes (formation of 1° palate).
Cleft lip
Cleft palate
failure of fusion of the lateral palatine processes, the nasal septum, and/or the median palatine process (formation of 2° palate).
failure of fusion of the lateral palatine processes, the nasal septum, and/or the median palatine process (formation of 2° palate).
Cleft palate
Increase in AFP
Neural Tube defect and omphocele
Decrease in AFP
Down Syndrome
