Embryology Flashcards
What is Embryology?
study of the origin and development of single individual
What are the first 8 weeks of prenatal period known as?
Embryonic period
What are the last 30 weeks of prenatal period known as?
Fetal period
What does the basic body plan include?
Skin – dermis and epidermis
Outer body wall – trunk muscles, ribs, vertebrae
Body cavity and digestive tube (inner tube)
Kidneys and gonads – deep to body wall
Limbs
What is a fertilized oocyte that moves toward the uterus called?
Zygote
What are Blastomeres?
daughter cells formed from zygote
What is a Morula?
solid cluster of 12–16 blastomeres Think “Mulberry”
What is a Blastocyst?
fluid-filled structure ~ 60 cells
List the stages of the fertilization and events of the first 6 days of development
Zygote -> 4-cell –> Morula -> Early blastocyst -> Late blastocyst (implants at this stage)
What are the prenatal periods?
Embryonic period Fetal period
what length in time defines each prenatal period?
Embryonic period – first 8 weeks
Fetal period – remaining 30 weeks �
What is the size of the embryo 25 days after conception? 36 days? 56 days?
3.5mm 10mm 30mm
What happens during the embryonic period?
Organs form from 3 primary germ layers
What is a major thing that happens during the fetal period?
organs grow in size and complexity
True or False most of cell proliferation occurs during the fetal period?
true. Reason: organs are growing in size by proliferation. Although cells also proliferate during the embryonic period majority of cells are differentiating during at that time.
what organ or structure allows for gas exchange between the fetus and mother?
placenta
What is teratogenesis?
something that can harms the fetus
During which week(s) are prenatal death at greatest risk?
1-2 weeks after conception
During what period can physiological defects occur?
Fetal period
What organs/systems are begining to develop when an embryo is 3.5mm?
Heart and CNS
Name the system that is at risk of defect throughout development (3weeks to 38weeks)
CNS
what does the outer body wall consist of?
trunk muscles, ribs, vertebrae �
Where does conception occur?
lateral third of the uterine tube
What are the daughter cells formed from zygote known as?
blastomeres
Define zygote
fertilized oocyte
what is Morula?
solid cluster of 12–16 blastomeres
What are the stages that occur during the first week of development?
Zygote 4-cell Morula Early blastocyst Late blastocyst (implants at this stage)
What sheets is the inner cell mass divided into?
hypoblast and epiblast
During what stage is the blastocyst cavity formed?
early blastocyst
What is formed by the extension of the hypoblast?
yolk sac
What is the structure outlined in black?
amniotic sac
what does the yolk sac form into?
digestive tube
what gives rise to earliest blood cells and blood vessels?
tissues around yolk sac
What occurs on day 6?
blastocyst implant itself into the uterus
when is the inner cell mass formed?
day 6
which part of the embryo is NOT a major source of nutrients?
yolk sac
what lines the amniotic sac cavity?
amnion
what is primitive streak?
raised groove on the dorsal surface of the epiblast
During what process are the primary germ layers formed?
gastrulation
define gastrulation
a process of invagination of epiblast cells
from bilaminar to trilaminar
where does gastrulation begin?
at the primitive streak
what cells do the germ layers derive from?
epiblast cells
Name the germ layers?
ectoderm, mesoderm, endoderm
what does the primative node give rise to?
the notochord in mesoderm layer
what happens during neurulation? and when does it occur?
ectoderm starts forming brain and spinal cord (17-22 days)
After gastrulation the epiblast is now called _______
ectoderm
what is responsible for signaling in the trilaminar embryo?
notochord
what is the folding (inward) of the ectoderm known as?
nueral groove
What is the neural plate?
ectoderm in the dorsal midline
What part of the neural tube becomes the brain?
cranial part
what originates from ectodermal cells and forms sensory nerve cells?
Neural crest
During what day of development does the ectoderm fold inward?
Day 19
What happens during the 4th week of development?
The body takes it shape by the folding of embryo laterally and at the head and tail
What is formed when the tubular part of the yolk sac enclose?
primitive gut
What does the primitive gut eventually form?
Future digestive tube and respiratory structures
what does the neural tube become?
neural tube becomes spinal chord and the brain
what does the notochord become?
nucleus pulposus within intervertebral disc
What are the parts of a differentiating mesoderm?
Paraxial (somatic) mesoderm
Intermediate mesoderm
Lateral plate mesoderm
The lateral plate forms a cavity that divides the it into what two layers?
Somatic mesoderm – apposed to the ectoderm
Splanchnic mesoderm – apposed to the endoderm
What does ectoderm go on to form?
Epidermis
hair
Nails
Glands of skin
brain
spinal cord
neural crest
What does the Neural crest consist of?
Sensory nerve cells
Some nervous structure
Pigment cells
Portion of skeleton
Blood vessels in head and neck
What is the notochord portion of mesoderm form?
Nucleus pulposus of intervertebral disc
What are the divisions that derive from the mesoderm?
Notochord
Somite (paraxial)
Intermediate
Lateral plate mesoderm
What does the somite portion of mesoderm form?
Sclerotome – vertebral and ribs
Dermatome – dermis (dosal)
Myotome – trunk and limb musculature
What does the dermis derive from?
Somite -\> Dermatome (dorsal) Somatic mesoderm (ventral)
What forms the kidney and gonads?
Intermediate mesoderm
where does parietal serosa derive from?
somatic mesoderm
where does visceral serosa derive from?
splanchnic mesoderm
what does the somatic mesoderm form?
parietal serosa
dermis (ventral)
CT of limbs
What does the splanchnic mesoderm form?
visceral serosa
WALL (musculature, CT) digestive and respiratory tracts
heart
blood vessels
what does the endoderm form?
epithelial linging and glands of digestive and respiratory tract
when does the embryo first respembles a human and has all organs in place?
week 8
When do limb buds form?
Second month of embryonic development (week 5-8)
During the 8th week of development what structure is larger than the body?
liver is disproportionally larger than the body
How is the endoderm formed?
from migrating cells that replace the hypoblast
Do cells differentiate during the fetal period?
Yes. Cells are differentiating during the first half of the fetal period
Describe some events that occur during the 8th week of development?
eyes and ear look human
neck begin to become evident
head is nearly as large as body
all major brain divisions are present
first brain waves occur in brainstem
bone formation occurs
weak muscle contraction
limbs formed, digits are webbed until end of 8 weeks
cadiovascular system is fully functional
Describe some events that occur during the 3rd month (9-12 weeks) of development?
head is still dominant but body is elongating
brain is enlarging
retina is present
R/L palate fuses together
walls of hollow organs are gaining are gaining smooth muscle
blood cell formation begins in bone marrow
notochord deternerates
can determine sex
What is the blastocyst surrounded by?
single layer of cells called trophoblast
Sucking motions of the lips begin during the 8th month of development true or false
false this occurs at 4 months
what is the name of the cavity that forms between the two lateral plate layers?
Coelom
what does the coelom become?
serous body cavities
When does the fetal heart start pumping?
4 weeks
