Gametogenesis (Exam 1) Flashcards
What are primordial germ cells
undifferentiated cells that migrate to the gonadal ridge to become either sperm or egg cells
Where do primordial germ cells originate from
epiblast
Where do primordial germ cells migrate
to the yolk sac and then back to the body cavity where they situate themselves in the thoracic region
What does the epiblast form
the layers of the trilaminar embryo
What is the area in the thoracic region where they land
genital ridge
What does the genital ridge end up forming
the ovary or teste
Where do primordial germ cells originate from
epiblast
Where will trilaminar embryo be formed
from cells of the epiblast
What are primitive sex cords
cells surrounding primordial germ cells that originate from genital ridge
What is formed in males from sex cord cells
sertoli cells
What is formed females from sex cord cells
follicular cells
What are Sertoli cells
supporting cells to forming sperm
What are Follicular cells
surround oocyte
When will primordial germ cells come out of dormant state in males
puberty
What is the role of Leydig cells in male gametogenesis
produce testosterone
What does testosterone production do
stimulate sertoli cells and sperm generating cells to start producing sperm
What type of cells are contained within the seminiferous tubules
sertoli and sperm-forming cells
Where will mature cells be seen in the seminiferous tubules
towards the center
Where will immature cells be seen in the seminiferous tubules
on the outside (they move in as they mature)
What is the summary of meiosis in males
Spermatogonia Primary spermatogonia 2 Secondary spermatogonia 4 Spermatids Mature Sperm
Where does meiosis occur in males
in the male reproductive tract
How many types of spermatogonia are there
two
What is spermiogenesis
formation of sperm from spermatids
What occurs during spermiogenesis
formation of acrosome
formation of tail and neck
condenses DNA material
gits rid of cytoplasm and extraorganelles
What is the function of the acrosome
to help sperm cross zona pellucida and plasma membrane in oocytes
Why is the cytoplasm shed in spermiogenesis
to make the sperm more streamlined to swim
What is capacitation
shedding of glycoproteins on the outside of the sperm
Where does capacitation occur
in the female reproductive tract in response to uterine fluids
In females how are oogonia produced
female germ cells undergo a series of mitotic divisions after being invested by the sex cords and differentiate into oogonia
When does meiosis start for oogonia
week 12 of development
What occurs during meiosis for oogonia
it is halted and becomes dormant until puberty
What forms a primordial follicle
single, flat layer of cells that form around a primary oocyte
How is oocyte division arrested
follicle cells produce hormone OMI
What does OMI hormone stand for
oocyte maturation inhibitor
What does OMI do
stop the oocyte from finishing division
What is the corpus albicans
degenerated corpus luteum, a scar tissue in the ovary that is the remnant of the follicle
What is the key feature in identifying a graafian follicle
antrum
What is a key feature of a primary follicle
cuboidal follicle cells
Where will immature follicles be seen in an ovary
less mature are on the outside of the ovary
What are the hormones involved in ovulation
LH
FSH
What is FSH released in response to
GnRH
What does FSH do
stimulate follicles to grow
When does FSH production occur
during the follicular phase it increases and is highest just prior to ovulation
What does FSH causes the production of
estrogen
When does LH rise
during the follicular phase
What does LH stimulate the production of
progesterone
What does progesterone do
prepare the uterus for implantation
What are the two stages of the ovarian cycle
follicular phase
luteal phase
How will changes in LH and FSH levels affect follicles in the ovary
cause 5-12 primordial follicles to multiply and increase in size and become primary follicles
What is the zona pellucida
a glycoprotein coat produced by the oocyte and follicular cells
What is important about the zona pellucida for fertilization
sperm must penetrate this layer via the acrosome
What type of follicle will have an antrum
Graafian follicle
What are the two connective tissue layers found on a graafian follicle
theca externa
theca interna
What is the function of the theca interna
secrete steroids (estrogen and progesterone
What is the function of the theca externa
connective tissue layer with little function
How many primary follicles will develop into graafian follicles
1
What occurs to the rest of the primary follicles that do not develop into graafian follicles
they degenerate
When will the oocyte finish meiosis
after fertilization
What is the oocyte when it is in the ovary
a primary oocyte
When the oocyte is leaving the ovary, what is it at the time of ovulation
a secondary oocyte
When does the 2nd meiotic division occur
at the time of fertilization
How long does meiosis take for females
10-50 years
How long does meiosis take for males
9 weeks
When does oogenesis start
in utero
When does spermatogenesis start
just before puberty
How many oocytes do women have
limited number
How many spermatogonia do males have
infinite
What will happen to the corpus luteum if there is implantation
The syncytiotrophoblast secretes hCG to keep the corpus luteum alive to produce progesterone until the placenta starts producing progesterone
What will happen to the corpus luteum if no implantation occurs
degenerates and the endometrium begins to dissociate
What does the syncytiotrophoblast secrete
human chorionic gonadotrophic hormone (hCG) that keeps the corpus luteum alive
What causes down syndrome
Trisomy 21
What are the features of down syndrome
slanted eyes growth retardation varying intellectual disability, epicanthal folds flat facies small ears cardiac defects hypotonia
What are the features of trisomy 18
low-set ears, small mouth, deficient mandible, flexion of the hands, absent and or hypoplasia of the radius and ulna
Intellectual disability
Congenital heart defects
What are the features of trisomy 13
Intellectual disability
holoprosencephaly
congenital hear defects
deafness, cleft lip and palate, eye defects, microphtlamia, anophthlamia, and coloboma
What is Klinefelter syndrome
XXY in males
What are features
gynocomastia, sterility, testicular atrophy, hyalinization of the seminiferous tubules
What is the genetic composition of Turner Syndrome
X
What are the features of Turner’s Syndrome
webbed neck lymphedema short stature absence of ovaries skeletal deformities broad chest with widely spaced nipples
What are the features of Triple X syndrome
low self esteem and speech issues
often goes undiagnosed
What causes Cri du crat syndrome
deletion of short arm of chromosome 5
What are the features of Cri du crat syndrome
cat-like cry, ID, microcephaly, congenital heart disease
What causes Angelman syndrome
microdeletion of the long arm of chromosome 15 on the maternal gene
What are the features of Angelman syndrome
intellectual disability
cannot speak
poor motor development
unprovoked and prolonged periods of laughter
What causes Prader-Willi syndrome
microdeletion of long arm of chromosome 15 on the paternal gene
What are the features of Prader-Willi syndrome
obesity intellectual disability hypotonia hypogonadism undescended testes
What causes Fragile X syndrome
full mutation occurs where there are more than 200 CGG repeats on the FMR1 gene on X chromosome leading to gene inactivation
What are the features of Fragile X syndrome
intellectual disability, large ears, prominent jaw, large testes
What week of development do germ cells migrate into the yolk sac
week 2
What week of development do germ cells migrate to the abdominal wall
weeks 4-6
What are the two types of spermatogonia
Type A
Type B
What do Type A spermatogonia arise from
the stem cell population
What do Type A spermatogonia give rise to
Type A and Type B spermatogonia
How many types of Type A spermatogonia are there
two types
What are the two types of Type A spermatogonia
Dark and Pale
What are Dark Type A spermatogonia
not dividing, reserve cells
What are the Pale Type A spermatogonia
giving rise to type A and B spermatogonia
What are Type B spermatogonia giving rise to
primary spermatocytes via mitosis
What occurs during capacitation
pruning of the glycocalyx of the sperm to interact with the oocyte
Spermatogonia to primary spermatocytes occurs through what
mitosis
Primary spermatocytes to secondary spermatocytes occurs via what
meiosis I
Secondary spermatocytes to spermatids occurs via what
meiosis
spermatids to sperm occurs via what
spermiogenesis
What is a normal sperm count
100 million sperm/ mL
What is an infertile sperm count
less than 10 million/ mL
By month 5, how many oocytes are there
7 million
At birth, how many oocytes are there
600,000-800,000
At puberty how many oocytes are there
40,000
How many oocytes will be ovulated
less than 500
What secretes GnRH
hypothalamus
What does GnRH
act on the pituitary gland and stimulates the release of FSH and LH
What is a vesicular follicle
a Graafian follicle (same thing, different name)
When is the first meiotic division completed
just prior to ovulation to form a secondary oocyte and the first polar body
When does the second part of meiosis begin in the oocyte
just immediately after ovulation, but halts until fertilization to finish
What day of the menstrual cycle does GnRH get produced, LH, FSH start rising
5th day
What type of follicular cells surround a primordial follicle
simple squamous epithelium
What are the two stages of primary follicles
Unilaminar
Multilaminar
What are Unilaminar primary follicles
- simple cuboidal epithelium around
- has a zona pellucida
What are multilaminar primary follicles
epithelium is stratified
What is a vesicular follicle
has an antrum that contains liquor folliculi
When does ovulation begin and end in a females life
puberty and lasts every 30 days for 30-35 years
In the menstrual cycle, when does ovulation occur
day 14 or 15
What is released from the ovary at ovulation
secondary oocyte
fluid of Graafian follicle
cells of the cumulus oophorus
Secondary oocyte moves into the uterine tube by what
fimbria of the uterine tube and by beating cilia lining the oviduct
What does the corpus luteum function as
an endocrine organ that secretes sterois to maintain the uterine endometrium
What are the 3 endocrine events of menstrual cycle
GnRH is released by the hypothalamus
GnRH causes the anterior pituitary to release LH and FSH
LH and FSH reach the ovary and causes the release of estradiol and progesterone
What are the cyclic changes of FSH
rises during the first half of follicular phase
Peaks during ovulation
declines during luteal phase
What is the function of FSH
stimulate the development of ovarian follicles and production of estrogen
What is the cyclic changes of LH
rises during first half of follicular phase
peaks just prior to ovulation
declines during luteal phase
What is the function of LH
serves as the trigger for ovulation
stimulates the production of progesterone
What is the cyclic changes of estrogen
low in the first half of follicular phase
rises during second half of follicular phase and peaks before LH surge
declines during the beginning of luteal phase but then increases
What is the cyclic changes of Progesterone
low during follicular phase
begins to increase prior to ovulation
In pregnancy, what occurs to progesterone
levels remain high
If there is no pregnancy, what occurs to progesterone
rapidly declines
What are the 4 stages of uterine progression
menstrual
proliferative phase
secretory
ischemic phase
What occurs during the menstrual phase
lasts 4-5 days, uterine bleeding due to shedding of the endometrium
The first day of bleeding indicates what
day one of the ovarian and menstrual cycles
What occurs during the proliferative phase
period of growth, varies in duration, but typically 10 days
When does the proliferative phase end
at ovulation
What is the secretory phase
secretion by uterine endometrium that begins at ovulation
What is the ischemic phase
constriction of uterine arteries caused by decrease in progesterone
