Early Embryology I & II Flashcards
Fertilization normally occurs in the ___ of the uterine tube
ampulla
Movement of sperm from the cervix to the uterine tube requires ___ to ___ hours
2-7
What happens to sperm motility once they reach the cervix?
sperm become less motile and stop their migration if ovulation has not taken place; if ovulation occurs, the sperm become mobile again and continue their swim to the ampulla
Sperm can only fertilize the egg after undergoing ___ and ___ reaction
capacitation; acrosome
This is a period of condition that takes place in the female reproductive tract and lasts about 7 hours. It involves an interaction between the sperm and the female reproductive tract.
capacitation
This is induced by zona proteins after the sperm binds to the zona pellucida covering the ovum. This process releases enzymes that allow the sperm to penetrate the zona pellucida
acrosomal reaction
Fertilization occurs in how many phases
6
The first phase of fertilization is passage of a sperm through the ___ _____ of the oocyte.
corona radiata
Dispersal of the follicular cells of the corona radiata results mainly from the action of the enzyme _____, which is released from the acrosome of the sperm
hyaluronidase
The second phase of fertilization is penetration of the ___ ___, which is a glycoprotein shell that surrounds the egg.
zona pellucida
The release of acrosomal enzymes allows the sperm to penetrate the zona pellucida and come in contact with the ___ ___ of the oocyte
plasma membrane
The contact releases of lysosomal enzymes from the oocyte that alters the zona pellucida and prevents what?
other sperms from penetrating it
The third phase of fertilization is the fusion of what?
the plasma cell membranes of the oocyte and sperm
True or false?
After adhesion of the sperm, the plasma membranes of the sperm and egg fuse, and sperm head and tail enter the oocyte, but the plasma membrane of the sperm remains behind
true
The fourth phase of fertilization is the completion of the ___ meiotic division of the oocyte
second
The oocyte completes the second meiotic division and forms a mature oocyte, the nucleus of which becomes the female ____ and a second ___ ___
pronucleus; polar body
The fifth phase of fertilization is formation of the male pronucleus. Within the cytoplasm of the oocyte, the nucleus of the sperm enlarges to form the male pronucleus. What happens to the tail?
degenerates
The sixth phase of fertilization is breakdown of ____ membranes and restoration of ____ number of chromosomes.
pronuclear; diploid
The combination of 23 chromosomes in each pronucleus results in a ___ with 46 chromosomes
zygote
In regards to cleavage, division of the zygote begins approximately ___ hours after fertilization
30
Zygote cells divide repeatedly - these cells are called ____, becoming smaller with each cleavage division
blastomeres
After third cleavage, cells become _____, permitting a greater cell to cell interaction
compacted
The 16-32 cell stage is known as the ___
morula
In regards to blastocyst formation, around day ___, morula enters the uterus and uterine fluid penetrates through the zona pellucida into the intercellular spaces of the inner cell mass. These fluid-filld spaces coalesce to form the ____ cavity
4; blastocystic
As fluid increases in the blastocystic cavity, the blastomeres are spearated into two parts. What are they? What do they give rise to?
inner cell mass or embryoblast: gives rise to tissues which forms the embryo proper
outer cell mass or trophoblast: contributes to formation of the placenta
Implantation of the blastocyst into the endometrial epithelium occurs approximately ___ days after fertilization
6
The trophoblast (outer cell mass) proliferates rapidly and differentiates into two layers. What are they?
inner layer of cells - cytotrophoblast
outer layer of cells - syncytiotrophoblast
note: syncytiotrophoblast cells over the embryonic pole of the blastocyst begin to penetrate the endometrial epithelium
The embryoblast (inner cell mass) differentiates to form a bilaminar embryonic disc composed of two layers. What are the layers?
Epiblast (thicker layer)
Hypoblast (thinner layer, adjacent to blastocyst activity)
A small cavity appears within epiblast, enlarges to form ___ cavity. Epiblasts adjacent to cytotrophoblast differentiate into amniogenic cells called ____
amniotic; amnioblasts
In regards to days 9-10, vacuoles form in synctium, which later fuse to form lacunae. This stage of trophoblast development = ?
lacunar stage
In regards to days 9-10, cells that are derived from hypoblast line the blastocystic cavity, which now changes its name and is known as _____ cavity
exocoelomic
In regards to days 9-10, cells derived from the hypoblast form a membrane called exocoelomic membrane or ____ membrane, which lines the internal surface of the cytotrophoblast
Heuser’s
In regards to days 9-10, the exocoelomic membrane and exocoelomic cavity are modified to form the primitive yolk sac (____ _____ ___)
primary umbilical vesicle
In regards to days 9-10, the blastocysts becomes fully embedded in the endometrium at day 10. Penetration site is closed by ___ ____
fibrin coagulum
In regards to days 11-12 (establishment of the uteroplacental circulation), lacunae appear in syncytiotrophoblast, especially at the embryonic pole. The synctiotrophoblast penetrate deeper and erodes the endothelial lining of maternal ____ and maternal blood enters the lacunar system of spaces
capillaries
In regards to days 11-12 (establishment of the uteroplacental circulation), a new population of cells derived from the yolk sac form between the inner surface of cytotrophoblast and outer surface of amnion and the exocoelomic membrane. These cells form the _____ _____
extraembryonic mesoderm
In regards to days 11-12 (establishment of the uteroplacental circulation), large cavities form in the extraembryonic mesoderm, that coalesce and form a space called the extraembryonic coelom or ____ cavity. This space surrounds the primary umbilical vesicle and amniotic cavity
chorionic
In regards to days 11-12 (establishment of the uteroplacental circulation), the extraembryonic mesoderm lining the cytotrophoblast and amnion forms the ____ ____ ____. The lining covering the umbilical vesicle forms the ____ _____ ____
extraembryonic somatic mesoderm; extraembryonic splanchnic mesoderm
In regards to days 13-14, cells of cytotrophoblast proliferate and penetrate into synctiotrophoblast, forming cellular columns that are surrounded by syncytia. Together this form ___ ___ ___.
primary chorionic villi
In regards to days 13-14, the cytotrophoblastic cells penetrate through the sanctum to reach the maternal endometrium, and through contact with other villi form an outer ____ ____
cytotrophoblast shell
note: this attaches the chorionic sac to the maternal endometrium
In regards to days 13-14, villi that extend form the cytotrophoblast shell to the maternal tissues are called ___ chorionic villi. Side branches of stem villi form ___ chorionic villi
secondary; tertiary
In regards to days 13-14, it is through the walls of branch chorionic villi that the main exchange of oxygen and nutrients between the blood of the mother and embryo takes place. True or false?
true
In regards to days 13-14, the extraembryonic somatic mesoderm and the two layers of trophoblast form the ____ which form the wall of the ___ sac
chorion, chorionic
In regards to days 13-14, the embryo, its amniotic sac and umbilical vesicle are suspended in the ___ cavity by the connecting stalk. The connecting stalk with the addition of blood vessels will become the _____ ____
chorionic; umbilical cord
In regards to days 13-14, the day 14 embryo still has bilaminar embryonic disc but a uniquely thickened circular portion of the endoderm forms called the ___ ___, a future site of mouth and an important organizer of the head region.
prechordal plate
The synctiotrophoblast produces hormones including hCG, which by the 2nd week can be ____
detected - pregnancy test
Reproductive failure is common. Only ___% of eggs that are exposed to sperm become fertilized and show initial survival
42
The following description is of what fertilization abnormality:
trophoblast forms placental membranes but there is no embryonic development. These secrete high levels of hCG and may become malignant. Most arise from fertilization of oocyte lacking uncles followed by duplication of male chromosome to restore the diploid number (entire genome is paternal)
hydatidiform mole
The following description is of what fertilization abnormality:
placenta bridges the internal os of the cervix - causes severe, life-threading bleeding gin late pregnancy and delivery
placenta previa
The following description is of what fertilization abnormality: there is abnormal adherence of the placenta to the myometrium
placenta accreta
The following description is of what fertilization abnormality: chorionic villi penetrate the myometrium all the way to perimetrium
placenta percreta
The following description is of what fertilization abnormality: implantation outside the uterus, such as uterine tube, rectouterine pouch or in the ovary itself
ectopic preganancy
In regards to the third week of human development: trilaminar germ disc, ___ is the process that establishes 3 germ layers: ectoderm, mesoderm and endoderm that will give rise to all structures in the embryo
gastrulation
In regards to the third week of human development: trilaminar germ disc, gastrulation begins with the formation of the primitive ____ - on the caudal part of the epiblast. The cephalic end terminates as an elevated area, the primitive ___ that surrounds the primitive ___
streak; node; pit
In regards to the third week of human development: trilaminar germ disc, cells of the epiblast migrate towards the primitive streak, detach, an slip underneath the epiblast in a process called ____
invagination
In regards to the third week of human development: trilaminar germ disc, some of the invaginated cells displace the hypoblast and form the embryonic ____. Other cells migrate to a position between the now-formed ___ and the epiblast to form the ____. Remaining cells of the epiblast become the ____.
endoderm; endoderm; mesoderm; ectoderm
In regards to the third week of human development, formation of the notochord, mesenchymal cells migrate cranially from the primitive node and pit, forming a median cellular cord, the ___ process. This process acquires a lumen known as the ____ ____
notochordal; notochordal canal
In regards to the third week of human development, formation of the notochord, the notochordal process goes cranially between the ectoderm and the endoderm until it reaches the ___ ____, a small circular area of endodermal cells. The fused layers of this and the overlying ectoderm form the ____ membrane
prechordal plate; oropharyngeal
In regards to the third week of human development, formation of the notochord, some cells form the primitive streak migrate cranially on each side of the notochordal processes and around the pechordal plate. They meet cranially to form the cariogenic mesoderm in the ____ area, where the primordial of the heart begins to develop at the end of the third week
cardiogenic
In regards to the third week of human development, formation of the notochord, the floor of the notochord process fuses with the underlying embryonic endoderm and the fused layers undergo degeneration, resulting in the formations in the floor of the notochord process. This temporarily interconnects what two things?
amniotic cavity and umbilical vesicle
In regards to the third week of human development, formation of the notochord, the remains of the notchordal process form a flattened, grooved ___ ___
notochordal plate
In regards to the third week of human development, formation of the notochord, beginning at the cranial end of the embryo, the notochord cells proliferate and the notochord plate in folds to form the ____
notochord
In regards to the third week of human development, formation of the notochord, the prechordal plate will be important in the development of the forebrain while the notochord will be the basis for the formation of parts of the ___ ___ and ___ ___
axial skeleton; spinal cord
In regards to the third week of human development, formation of the notochord, at the caudal end of the embryo, the cloacal membrane forms, consisting of fused ectoderm and endoderm. At this time, the posterior wall of the umbilical vesicle forms a diverticulum called the ____ that extends into the connecting stalk
allantois
In regards to the third week of human development, establishment of the body axes, anteroposterior axis is signaled by cells at the cranial margin of the embryonic disc, an area called the ___ ___ ___, which expresses genes essential for head formation
anterior visceral endoderm
In regards to the third week of human development, establishment of the body axes, the primitive streak itself is initiated and maintained by expression of ___ gene and it up regulates a number of genes that regulate the formation of dorsal and ventral structures
nodal
In regards to the third week of human development, establishment of the body axes, for left and right sidedness, the expression of nodal and ____ for left side and ___gene for right side
lefty; snail
In regards to the third week of human development, fate map of epiblast migration is established, cells that migrate inward at the ___ ____ of the primitive node become the notochord
cranial region
In regards to the third week of human development, fate map of epiblast migration is established, intraembryonic mesoderm on each side of the notochord proliferates to form a thick, longitudinal column of ____ mesoderm
paraxial
In regards to the third week of human development, fate map of epiblast migration is established, each column is continuous laterally to become intermediate mesoderm which further thins into a layer of ___ ___ mesoderm
lateral plate
In regards to the third week of human development, fate map of epiblast migration is established, ______ mesoderm that covers amnion and umbilical vesicle is continuous with lateral mesoderm
extraembryonic
In regards to the third week of human development, growth of embryonic disc, initially the embryonic disc is almost round, but with growth, it becomes elongated. As expansion of the embryo occurs mostly in the cephalic region, the cephalic region becomes ____ while the caudal region remans ____
broad; narrow
In regards to the third week of human development, growth of embryonic disc, the enlargement of the disc is due to continuous cell migration from the region of the ___ ___. This process continues until the end of the fourth week
primitive streak
In regards to the third week of human development, growth of embryonic disc, the continued supply of cells form the primitive streak until the end of the fourth week is important for the development of the embryo. While the cell layers in the ___ part of the embryo begin differentiation in the third week, differentiation of the ___ part begins at the end of the fourth week
cephalic, caudal
Around the end of the ___ week, the primitive streak recesses, shrinks, and soon disappears
fourth
The following defines what clinical correlation:
high doses of alcohol at the gastrulation stage kill cells in the anterior midline of the germ disc, producing a deficiency of the midline in craniofacial structures. Fore brain is all; the two lateral ventricles often merge into single ventricle
holoprosencephaly
The following defines what clinical correlation:
insufficient mesoderm is formed in the caudal most region of the embryo. since mesoderm contributes to formation of lower limbs, urogenital system, and lumbosacral vertebra, abnormalities in these structures ensue. condition sometimes associated with maternal diabetes
sirenomelia
The following defines what clinical correlation:
left and right organ positions are reversed
situs inversus
The following defines what clinical correlation:
proliferation of remnants of the primitive streak. forms tumors, that commonly contain tissues derived from all three germ layers. most common tumor in newborns
sacrococcygeal teratoma
In regards to the third to eight week (the embryonic period), around the fourth week, due to rapid growth, the ___ ____ forms a head fold, tail fold, and lateral folds
embryonic discs
In regards to the third to eight week (the embryonic period), derivatives of the ectoderm layer, in general, the organs that maintain contact with the outside world are formed from ectoderm layer. These include what?
CNS, PNS; sensory epithelium of eye, ear, and nose; the skin
In regards to the third to eight week (the embryonic period), derivatives of the ectoderm layer, in the third week of development, the notochord and prechordal mesoderm induce the formation of the ___ plate as a thickening of the overlying ectoderm. Cells of this make up the neuroectoderm
neural
In regards to the third to eight week (the embryonic period), derivatives of the ectoderm layer, further development takes place as the process of neurulation. By the end of week three, the neural plate forms lateral elevations called ___ ___. The ___ ____ is the depression between these.
neural folds; neural groove
In regards to the third to eight week (the embryonic period), derivatives of the ectoderm layer, with further development, the neural folds fuse, forming the __ ___. This process begins in the cervical region and proceeds both cranially and caudally. At this stage, this structure is in communication with the amniotic cavity via the cranial and caudal _____
neural tube, neuropores
In regards to the third to eight week (the embryonic period), derivatives of the ectoderm layer, between days 25 and 27 the cranial and caudal neuropores close forming a closed CNS consisting of the ___ ____ and the ___ ___
brain vesicles; spinal cord
In regards to the third to eight week (the embryonic period), derivatives of the ectoderm layer, as the neural folds fuse to form the neural tube, neuroectodermal cells at its lateral border separate to form the ____ ____ cells
neural crest
In regards to the third to eight week (the embryonic period), derivatives of the ectoderm layer, in the area of the trunk, neural crest cells migrate along a dorsal pathway to form what? in a ventral pathway to form what? and in the cranial area to form what?
dorsal pathway: melanocytes
ventral pathway: sensory, sympathetic, and enteric ganglia and schwan cells
cranial area: craniofacial skeleton, cranial nerve ganglia, and parasympathetic ganglia
In regards to the third to eight week (the embryonic period), derivativatives of the mesoderm layer, by the 17th day, the sheath of mesoderm begins to differentiate and form 3 subdivisions: the ___, ____, and ___ mesoderm
paraxial; intermediate; lateral
In regards to the third to eight week (the embryonic period), derivatives of the mesoderm layer - paraxial mesoderm, in the beginning of week 3, the paraxial mesoderm begins to become organized into segments called ____. From the occipital region and then caudally, these form ____
somatomeres; somites
In regards to the third to eight week (the embryonic period), derivatives of the mesoderm layer - paraxial mesoderm, somite formation begins around day ____ in the occipital region and progresses caudally until the end of week ___, forming occipital, cervical, thoracic, lumbar, sacral and coccygeal pairs of somites
20; 5
In regards to the third to eight week (the embryonic period), derivatives of the mesoderm layer - paraxial mesoderm, around the beginning of week 4, each somite further differentiates to form its own sclerotome, myotome, and dermatome. Describe what each of these form.
sclerotome: bones, cartilages, and tendons
myotomes: muscles
dermatomes: dermis
In regards to the third to eight week (the embryonic period), derivatives of the mesoderm layer - intermediate mesoderm will differentiate to form what?
urogenital organ components
In regards to the third to eight week (the embryonic period), derivatives of the mesoderm layer - lateral mesoderm splits into 2 layers, a parietal mesoderm that lines the ___ cavity and a visceral mesoderm that surrounds ____
intraembryonic; organs
In regards to the third to eight week (the embryonic period), derivatives of the mesoderm layer - lateral mesoderm. Mesoderm cell of the parietal layer will form thin mesothelial serous membranes that will line the ___, ___, and ___ cavities
pleural, pericardial, and peritoneal
Blood vessel formation occurs by two mechanisms; vasculogenesis and angiogenesis. Describe each
vasculogenesis: vessels form from blood islands
angiogensis: sprouting form already formed vessels
The first blood cells arise form hemangioblasts in the center of blood islands in the umbilical vesicle that form ___ ___ cells
hematopoietic sem cells
In regards to the third to eight week (the embryonic period), derivatives of the endodermal layer, the midgut communicates with the umbilical vesicle via the ___ duct
vitelline
In regards to the third to eight week (the embryonic period), derivatives of the endodermal layer, at the cephalic end, the oropharyngeal membrane ruptures week ___ while the cloacal membrane ruptures in week ___, creating continuities between the gut and the amniotic cavity
4;7
In regards to the third to eight week (the embryonic period), derivatives of the endodermal layer, as the embryonic disc forms a head fold, tail fold, and lateral fold, the allantois is partially incorporated into the embryo, where it forms the ____
cloaca
In regards to the third to eight week (the embryonic period), derivatives of the endodermal layer, with further development, the endodermal germ layer also gives rise to the epithelial lining of organs such as?
the respiratory and urinary tracts; the parenchyma of the thyroid, liver and pancreas
During the second month, the age of the embryo is no longer determined by the number of somites, but by the ______ ___, expressed in millimeters as the distance from the vertex of the skull to the midpoint between the apices of the buttocks
crown-rump length
In regard to birth defects, the third to eight week is the period of _____, as such, this is a period when most gross structural birth defects occur
organogenesis
What is the fetal period? and what is it characterized by?
9W to birth; maturation of organs and rapid growth of body
Greatest length increase in what months? greatest weight increase in what months?
length: 3,4,5
weight: 8, 9
What is the length of pregnancy in weeks after fertilization
38
external genitalia develop to the extent by week ___ that the sex of the fetus can be determined by ultrasound
12
At week 10 of the fetal period, the ___ is the major site of erythropoiesis
liver
limb movements become coordinated by the ___ week
14th
the face becomes more human looking during the ___ month
third
By ___ weeks, the ovaries are differentiated and contain primordial follicles
16
growth slows down during weeks 17-20 but the fetus still increases its CRL by approximately ___ mm
50
brown fat forms during weeks 17 and 20 and is the site of ___ ___ in newborn
heat production
In male ___ week fetuses, the testes have begun to descend
20
substantial weight gain occurs during weeks ___ to ___
21; 25
By week ____ the fetus exhibits sucking movements and can react to some sounds
24
Although a 22-25 week fetus born prematurely may survive if given intensive care, the fetus may die because its ___ system is still immature
respiratory
At weeks ___ to ___, the CNS has matured to the stage at which it can direct rhythmic breathing and control body temperature
26-29
formation of red blood cells in the spleen ends by ___ weeks, by which time the bone marrow has become the major site of this process
29
The pupillary light reflex of the eyes can be elicited by ___ weeks
30
Fetuses ___ weeks and older usually survive if born
32
By ___ weeks the circumferences of the head and the abdomen are approximately equal
36
Most fetuses have a CRL of ___cm, CHL of ____cm, and weight approximately ____ to ____ g
36; 50; 3000-3400
