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Embryology Ch. 2-3
Embryology Ch. 2-3 (Tulane SOM 2015)
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08/04/2011

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Term
meiosis
Definition
process in which a diploid cell becomes multiple haploid cells by undergoing two subsequent divisions, the first being a reduction division; occurs in germ cells only
Term
spermiogenesis
Definition
last leg of spermatogenesis; haploid spermatids are turned into spermatozoa (in the seminiferous tubules); round spermatids are elongated, cytoplasm is lost, acrosome formed
Term
spermatogenesis
Definition
gametogenesis for sperm; the steps in which a spermatogonia (germ cell) is transformed into a spermatozoa
Term
oogenesis
Definition
gametogenesis for eggs; steps in which a oogonia is transformed into a mature oocyte
Term
primary spermatocyte
Definition
diploid stage after mitosis of spermatogonia; ready to undergo meiosis; largest germ cells in seminiferous tubules
Term
secondary spermatocyte
Definition
haploid stage of germ cells after meiosis 1
Term
chromatid
Definition
one of two genetically identical strands that make up a duplicated chromosome
Term
chromosome
Definition
organized genetic structure (DNA + proteins) that codes for many genes
Term
post‐zygotic nondisjunction
Definition
failure of normal mitosis to separate sister chromatids, resulting in an abnormal
distribution of chromosomes equaling a mosaic.
Term
mosaic
Definition
if a PZN occurs during fetal development, all daughter cells would hence be disrupted. However, all
normal cells up to that point would likewise continue to divide, so there would be a mixture, a mosaic, of normal
cells and abnormal cells, resulting in a combination of phenotypes.
Term
polar bodies
Definition
asymmetrical cell division leads to the production of nonfunctional, small polar bodies during oogenesis, which later degenerate
Term
Leptotene
Definition
during this stage, individual chromosomes begin to condense into long strands within the nucleus.
However, the two sister chromatids are still so tightly bound that they are indistinguishable from one another.
Term
Zygotene
Definition
occurs as the chromosomes approximately line up with each other into homologous chromosomes.
Term
Pachytene
Definition
contains the chromosomal crossover. Non‐sister chromatids of homologous chromosomes
randomly exchange segments of genetic information over regions of homology
Term
Diplotene
Definition
the synaptonemal complex degrades and homologous chromosomes separate from one another a
little.
Term
Diakinesis
Definition
the first point in meiosis where the four parts of the tetrads are actually visible.
Term
5 phases of prophase
Definition
1. leptotene
2. zygotene
3. pachytene
4. diplotene
5. diakinesis
Term
acrosome
Definition
cap-like saccular organelle on the head of a mature sperm filled with hydrolytic enzymes that facilitate sperm penetration of the corona radiata and zona pellucida
Term
sperm head
Definition
contains the haploid gamete nucleus of the sperm
Term
midpiece
Definition
section of mature sperm that contains the mitrochondria that are used for energy
Term
sperm tail
Definition
used for motility, microtubules; contains mitochondria for energy
Term
zona pellucida
Definition
amorphous acellular glycoprotein coat surrounding the ovum; binds to sperm during fertilization
Term
capacitation
Definition
post-ejaculation- final step of functional maturation for sperm; essentially the activation of the sperm; consists of changes in the acrosome to allow penetration of the zona pellucida
Term
zygote
Definition
single-celled embryo formed by joining of male and female pronuclei
Term
gametogenesis
Definition
gamete formation; process include meiosis and prepares the gametes for fertilization
Term
gamete
Definition
specialized generative cell (oocyte [egg] and sperm)
Term
first meiotic division
Definition
reduction division (46N --> 23N) which segregates homologous chromosome s into separate secondary gametocytes; crossing over occurs (genetic recombination)
Term
second meiotic division
Definition
separates each chromosome from its chromatid; produces "single chromatid chromosome" containing gamete cells (4)
Term
chromatid
Definition
half of a divided chromosome
Term
nondisjunction
Definition
disturbances during meiosis of gametogenesis that result in (numerical) chromosomally abnormal gametes; homologous chromosomes do not separate during meiosis 1 or chromatids do not separate in meiosis 2
Term
mature sperm
Definition
also "spermatozoa"; free-swimming, actively motile cell w/ head (acrosome, nulceus) and tail
Term
spermatogonia
Definition
dormant male gamete cells (in seminiferous tubules) pre-meiosis
Term
primary oocyte
Definition
diploid female germ cell that becomes surrounded by follicular cells and the zona pellucida
Term
secondary oocyte
Definition
Term
spermatid
Definition
pre-spermiogenesis, post-meiosis germ cells
Term
Sertoli cells
Definition
cells lining the seminiferous tubules that nuture and supprt germ cells, may regulate
Term
oogonia
Definition
cells that undergo mitotic division and enlarge to form primary oocytes during fetal development
Term
primordial follicle
Definition
primary oocyte surrounded by single layer of follicular cells
Term
primary follicle
Definition
primary oocyte surrounded by cuboidal follicular cells, later zona pellucida
Term
secondary follicle
Definition
develops when primary follicle has more than one layer of follicular cells
Term
first polar body
Definition
nonfunctional secondary female gamete cell formed after meoisis 1 division; receives little of the cytoplasm
Term
second polar body
Definition
after fertilization, nonfunctional secondary female gamete cell that degenerates; receives little of the cytoplasm
Term
3 layers of body of uterus
Definition
1. perimetrium (thin external)
2. myometrium (thick smooth muscle)
3. endometrium (thin internal)
Term
3 layers of endometrium
Definition
DURING LUTEAL PHASE
1. compact layer
2. spongy layer
3. basal layer
Term
compact layer of endometrium
Definition
thin; densely packed connective tissue around necks of uterine glands
Term
spongy layer of endometrium
Definition
thick; edematous connective tissue containing dilated, tortuous bodies of uterine glands
Term
basal layer of endometrium
Definition
thin; contains blind ends of uterine glands
Term
functional layer of endometrium
Definition
compact + spongy layers
Term
normal site of fertilization
Definition
ampulla of the uterine tube
Term
GnRH
Definition
gonadotropin-releasing hormone; synthesized in hypothalamus; stimulates release of LH and FSH in pituitary gland
Term
FSH
Definition
follicle-stimulating hormone; released by pituitary gland; stimulates development of the ovarian follicles/ production of estrogen by follicular cells
Term
LH
Definition
luteinizing hormone; released by pituitary gland; triggers ovulation, stimulates production of progesterone by follicular cells and corpus luteum
Term
theca folliculi
Definition
tissue adjacent to primary follicle that form capsule; includes theca interna and theca externa
Term
antrum
Definition
follicular fluid-containing cavity within primary follicle; presence indicates secondary follicle status
Term
cumulus oophorus
Definition
mound of follicular cells surrounding primary oocyte; basis of corona radiata
Term
stigma
Definition
small avascular spot on surface of ovary over sweeling created by growing follicle underneath; balloons to form vesicle after LH surge and ruptures to expel secondary oocyte
Term
corona radiata
Definition
layers of follicular cells radially surrounding expelled secondary oocyte and zona pellucida
Term
corpus luteum
Definition
glandular structure developed by influence of LH from walls of ovarian follicle remaining in ovary; secretes progesterone and estrogen to prevent menses
Term
hCG
Definition
human chorionic gonadotropin; prevents degeration of corpus luteum so that it can continue to produce hormones to support pregnancy; produced by syncytiotrophoblast
Term
menopause
Definition
permanent cessation of menstruation
Term
phases of menstrual cycle
Definition
1. menstrual phase
2. proliferative phase
3. luteal phase
4. ischemic phase
OR pregnancy phase
Term
ejaculate
Definition
sperms + secretions from accessory glands
Term
phases of fertilization
Definition

1. passage of sperm thru corona radiata

2. penetration of zona pellucida

3. fusion of plasma membranes

4. 2nd meiotic divsion of oocyte/ formation of female pronucleus

5. formation of male pronucleus

6. fusion of pronuclei to form zygote

Term
EPF
Definition
early pregnancy factor; protects zygote from maternal immune system; produced by trophoblastic cells
Term
blastomeres
Definition
embryonic cells after first division of zygote
Term
compaction
Definition
early stage when blastomeres change shape of tightly align themselves
Term
morula
Definition
post-12-cell stage mass of embryonic cells (~3 days post-fertlization)
Term
blastocystic cavity
Definition
fluid-filled cavity that forms inside morula producing blastocyst (forms via blastogenesis)
Term
trophoblast
Definition
thin, outer cell layer of blastocyst --->embryonic placenta
Term
embryoblast
Definition
inner cell mass of blastocyst ---> embryo proper
Term
embryonic pole
Definition
opposite abembryonic pole; pole of blastocyst next to embryoblast
Term
2 layers of trophoblast
Definition
DIFFERENTIATE POST-IMPLANTATION (~6 DAYS)
1. syncytiotrophoblast
2. cytotrophoblast
Term
cytotrophoblast
Definition
mononucleated layer of trophoblastic cells that forms new cells that migrate into syncytiotrophoblast
Term
syncytiotrophoblast
Definition
multinucleated mass of trophoblastic cells that invades endometrial epithelium, implanting conceptus; produces hCG and progesterone; establishes early uteroplacental circulation ---> placenta
Term
hypoblast
Definition
cuboidal cells; "roof" of exocoelomic cavity; --->endoderm
Term
extraembryonic structures forming during 2nd week
Definition
amniotic cavity, amnion, yolk sac, connecting stalk, chorionic sac
Term
embryonic disc
Definition
bilaminar disc composed of epiblast and hypoblast that gives rise to germ layers of embryo
Term
decidual cells
Definition
created by decidual reaction; connective tissue of the uterine endometrial epithelium around implantation that accumulate glycogen and lipids to 1. degenerate to provide nutrition 2. provide immunologically privileged site
Term
amniotic cavity
Definition
cavity that develops above epiblast
Term
amnion
Definition
lining of amniontic cavity; epiblastic cells that separate into amnioblasts or amniogenic cells (still continuous with epiblast)
Term
exocoelomic cavity
Definition
forms after blastocystic cavity lined with exocoelomic membrane (hypoblastic cells)
Term
primary yolk sac
Definition
Heuser's (exocoelomic) membrane forms from hypoblast, lines blastocystic cavity; exocoelomic membrane + hypoblast = primary yolk sac
Term
extraembryonic mesoderm
Definition
forms from yolk sac endoderm; surrounds amnion and yolk sac
Term
lacunae
Definition
isolated cavities in syncytiotrophoblast that fill with maternal blood (ruptured capillaries) and cellular debris (eroded glands); basis of primordial uteroplacental circulation
Term
closing plug
Definition
fibrinous coagulum of blood that closes hole in uterine endometrial epithelium created by embedding conceptus
Term
lacunar networks
Definition
fused lacunae; primordia of intervillous spaces of placenta
Term
extraembryonic coelomic spaces
Definition
spaces that appear in developing extraembryonic mesoderm; fuse to form ee coelom
Term
extraembryonic coelom
Definition
cavity that forms in ee mesoderm---> chorionic cavity
Term
secondary yolk sac
Definition
replacement yolk sac formed by ee endodermal cells; ---> gut
Term
primary chorionic villi
Definition
proliferation of cytotrophoblastic cells via extensions into syncytiotrophoblast
Term
extraembryonic somatic mesoderm
Definition
splits from ee coelom to line trophoblast and amnion; together w/ trophoblast layers forms chorion;--->lines body wall
Term
extraembryonic splanchnic mesoderm
Definition
splits from ee mesoderm to surround yolk sac; ---> lines gut, forms smooth muscle
Term
chorion/ chorionic cavity
Definition
chorion = lining of ee somatic meso., trophoblast layers; chorionic cavity contains embryo/ amniotic and yolk sacs; forms from ee coelom
Term
connecting stalk
Definition
connects embryo, amniotic/yolk sacs to chorion
Term
prechordal plate
Definition
tight association between columnar epiblastic and hypoblastic cells; indicates future site of mouth; organizer of head region; =prochordal plate; stays bilaminar through development of mesodermal layer;--->oropharyngeal membrane
Term
ectopic pregnancy
Definition
implantation of blastocyst outside uterus (uterine tube [tubal], pouch of Douglas or mesenteries [abdominal], cervical, ovarian)
Term
placenta previa
Definition
implantation inside the uterus at the internal os; placenta covers os causing complications
Term
epiblast
Definition
thicker layer of cells in embryonic disc; high columnar; related to amniotic cavity--->ectoderm ----->CNS, epitheliium
Term
role of maternal glands
Definition
provide lipids, glycogen, and nutrients
Term
rostral
Definition
toward the nose
Term
caudal
Definition
towards the tail
Term
amniocentesis
Definition
procedure to diagnose fetal chromosomal abnormalities; small amt. of amniotic fluid removed from amniotic cavity, contains epiblastic cells that can be analyzed
Term
trophoblastic hypoplasia
Definition
Term
trophoblastic hyperplasia
Definition

hydatidiform mole (molar pregnancy)

malignant chorioepithelioma

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