Early Embryology Flashcards
When is the egg released from the ovary?
14 days into ovarian cycle
What is sperm travel from cervix to oviduct?
30 mins to 6 days
What is the egg coat called?
Zona pellucida
What is the female nucleus called?
Female pronucleus
What is the male nucleus called?
Male pronucleus
3 things that happen during fertilization
- Diploid number of chromosomes
- Gender determination
- Cleavage initiated
The sperm has to meet the egg cell within ___ hours of ovulation
24
At what point does the cell become a 2 cell stage zygote?
30 hours
What is the ball of cells called after the zygote rapidly divide?
Morula
At what point does cell become a morula?
3 days
At what point does the morula become an advanced morula?
4 days
What is the next stage after morula?
Blastocyst (fluid filled cavity)
When does the blastocyst form?
5 days post-fertilization
What mass develops in blastocyst?
Inner cell mass (embryoblast)
When does blastocyst enter uterus?
4.5-5 days
When does blastocyst implant in endometrium?
5.5-6 days
Development of embryo occurs at _____ from conception
7-8 weeks
List types of abnormal implantation *
Interstitial
Tubul (isthmus)
Tubal (ampullar)
Infundibular (ostial)
Ovarian
Peritoneal
Cervical
At week 1, what tissues are present?
Syncytiotrophoblast
Cytotrophoblast
Inner cell mass
Syncytiotrophoblast has…
Lacunae
Tissue of uterine wall is also known as
Uterine stroma
At week 2, trophoblasts differentiates into 2 layers known as…
The cytotrophoblast and Syncytiotrophoblast
At week 2, the embryoblast forms 2 layers known as
The epiblast and hypoblast
At week 2, 2 cavities form known as the
Amniotic and yolk sac cavities
At week 2, the extraembryonic mesoderm splits into
The somatic and splanchnic layers
At day 8, what parts divide?
Trophoblasts
Embryoblast
Syncytiotrophoblast region is
Multinucleated bc no cell walls
What do Syncytiotrophoblasts produce?
hCG
At day 9, what forms?
2 cavities:
Amniotic cavity
Exocoelomic cavity (primitive yolk sac)
What in the amniotic fluid is important for amniocentesis?
Sloughed off cells from embryo
What procedure do the sloughed off cells from amniotic fluid help us do?
Karyotyping
What occurs at day 12?
Extraembryonic mesoderm becomes somatic and splanchnic layers
What happens on day 13?
Extraembryonic cavity/chorionic cavity becomes huge but will quickly regress by end of second month
At 13 days, what else grows but will quickly regress later?
Yolk sac but by end of second month will regress
What part will grow beginning end of second month to end of third month?
Amniotic cavity (holds fetus)
At day 13, what could lead a woman to believe she got her period?
You might have a better trophoblastic lacunae that allow blood to come out
What occurs at week 3?
Gastrulation
What happens in gastrulation?
Converts bilaminar embryonic disc into the trilaminar embryo
What are the 3 germ layers produced by gastrulation?
- Ectoderm
- Mesoderm
- Endoderm
What’s involved in the ectoderm?
Neural system
Skin
Appendages that relate to external environment (e.g. eyes and ears)
What’s involved in the mesoderm?
Musculoskeletal tissue
Limb buds
Genitourinary system
Body wall
Membranes that line cavities
What’s involved in the endoderm?
Foregut, midgut, and hindgut
GI Tract and appendages (liver, pancreas)
Respiratory tract
Bladder
What is opposite the primitive streak on other side of epiblast?
Oropharyngeal membrane
Which side is dorsal? Epiblast or hypoblast
Epiblast is dorsal
Epiblast layers migrate through what?
Primitive node and streak
What is known as “the organizer” in gastrulation?
The Primitive Node
The body plan is redefined during what?
Gastrulation
What becomes the future mouth?
Oropharyngeal membrane
What becomes the future anus?
Cloacal membrane
Teratogenesis is associated with what?
Gastrulation
What is holoprosencephaly?
Injury to the anterior (cranial end) midline of germ disc
What 2 things are associated with holoprosencephaly?
High dose alcohol
Genetics
What is caudal dysgenesis?
Injury to the caudal aspect of the germ disc
What 2 things are associated with caudal dysgenesis?
Genetics
Environmental insults
What are sacrococcygeal tumors?
Remnant of the primitive streak
What can result in conjoined twins?
Splitting of the primitive node
List the birth defects associated with gastrulation
- Holoprosencephaly
- Cyclopia
- Caudal dysgenesis (sirenomelia)
- Sacrococcygeal tumors
- Conjoined twins (splitting of primitive node)
What type of plane divides body into left and right sections?
Sagittal plane
What type of plane divides body into front and back sections?
Coronal plane
Describe anatomical position
Standing, legs together, feet on floor
Hands at sides, palms facing anteriorly
Head held erect, facing anteriorly
what plane divides into upper and lower sections?
Transverse plane
List the 6 phases of embryology
- Gametogenesis
- Fertilization
- Cleavage
- Gastrulation
- Body plan formation
- Organogenesis
What are the migration patterns when epiblast cells migrate through primitive node and streak?
Caudal to cranial
Medial to lateral
Describe the notochord
Mesodermal derivative
Precursor to axial skeleton
Forms nucleus pulposus of intervertebral discs
Vertebral bodies form around notochord
Describe somites
Epithelial balls of cells formed in segmental pairs along the neural tube from paraxial mesoderm; differentiate into vertebrae, muscles of the back and body wall, and dermis of the skin
Can somites be used to track development?
Yes, can count somites to see how far development has proceeded
Describe the 3 step process of neurulation
- Notochord forms from mesoderm cells soon after gastrulation finishes
- Signals from notochord cause inward folding of ectoderm at neural plate
- Ends of neural plate fuse and disconnect to form an autonomous neural tube
When does fertilization begin?
At conception
When does gestational age begin?
Two weeks earlier, at beginning of last menstrual period
Embryology is used using days…
Post-fertilization
When may malformation of an embryo occur?
Between weeks 3-8 when organs are forming as it is period of max sensitivity to abnormal development
When may functional disturbance of a fetus occur?
Between weeks 8-38 during growth and maturation of organ systems
When may death of an embryo occur?
Between weeks 0-3
Define birth defect
Term for a congenital malformation
Define congenital disorder
A condition existing at birth and often before birth, or that develops during the first month of life, regardless of causation
Define teratology
The study of causes and biological processes leading to abnormal development
Define teratogen
Any agent that causes a birth defect
Define critical period
Time of increased sensitivity
What used to be used to decrease nausea/vomitting?
Thalidomide
What did thalidomide affect? What did it cause?
Blood supply to arm and forearm bones. Caused phocomelia
What are the 4 factors that make one susceptible to congenital anomalies?
Maternal age
Environmental factors
Genetic predisposition
Unknown
What happens on day 8?
- Trophoblast divides to form cytotrophoblasts and syncytiotrophoblasts
- Embryoblast divides to form hypoblast and epiblast
What happens on day 9?
Formation of amniotic cavity and exocoelomic cavity (primitive yolk sac)
What happens on day 12?
Extraembryonic mesoderm forms:
extraembryonic splanchnic mesoderm & extraembryonic somatic mesoderm
What happens on day 13?
- Extraembryonic cavity (chorionic cavity) is quite larger right now
- Yolk sac is also large right now
- Amniotic cavity is a bit smaller but will grow
- Trophoblastic lacunae may allow for blood to come out (NOT PERIOD BABES - STILL PREGGO)
