Gametogenesis & Fertilization Flashcards
What are primordial germ cells
Precursors of gametes that are recognizable by 4th week of gestation. They dev in the endoderm of the yolk sac and migrate to genital ridges about week 6. They associate with somatic cells to form primitive gonads. PGC’s divide by standard mitosis.
Both male/female gametes mature via ____ influences which release ___ which releases ___ and _____in pituitary. Males acquire testosterone and females aquire estrogen and progesterone
hypothalmic/pituitary
GnRH; LH and FSH.
Each oogonium is the central cell in a dev _____. By week 12, meiosis I is initiated & primary oocytes begin to dev and aquire layer of epithelial cells called ___ ____. Follicular cells secrete ______; arrest at prophase 1 (dictyotene). Only 400 primary oocytes will ever mature.
follicle; primordial follicles.oocyte maturation inhibitor (OMI)
____initiates puberty.
Leptin; have better nutrition and pack on pounds earlier. Once process begins start recruiting oocytes in continuum of ooocyte growth and eventually ovulation.
____ surge is hormone that triggers ovulation (release of egg from ovary) and reinitiation of meiosis.
LH
Throughout all processes we are still primary oocyte. Features of follicle change but oocyte is still locked in meosis I through out all processes until ______
ovulation
Leftoever follicle is called
corpus leteum
____maintains lining of uterus to give fertilized egg a chance to implant. If implantation doesnt happen, corpus luteum degenerates.
Progesterone
___ ___ has 3 primary glycoproteins attached that serves as a barrier. Changes in zona pellucida occur after fertilization that prevent second sperm from coming in. Only want one sperm!
zona pellucida; glycoproteins are called ZP1, 2, 3
___ stimulates follicle maturation. ____ stimulates ovulation. _____ sec by follicular cells, stimulates maturation. _____ is secreted by corpus luteum
FSH; LH; Estrogen; Progesterone
what is the cyclic dev of oocytes
- oocytes arrested as primary follicles = primary oocyte + single columnar layer of epithelial cells.
- Progresses to secondary follicle (NOT secondary oocyte) during menstrual cycle = primary oocyte + zona pellucida + multi layer epithelial cells
epithelial layer differentiates into ___ ____: interna and externa
theca folliculi
___ is the fluid filled cavity in center of follicle
antrum
What is LH doing?
Triggers the proteolytic breakdown of ovarian wall by granulosa secreted enzymes. Theca cells produce inhibitors to limit enzymatic breakdown.
LH activates _____ which activates plasmin which activates ____ which activates collegenase and then the follicule ruptures
plasminogen; procollagenase
Oocyte doesnt have any ___receptors but follicular cells around it do which activate the ____ pathway
LH; PKC
What is up in unstimulated egg that is locked in dictyolene stage? How does this occur?
cAMP and PKA;
LH surge causes increase in IP3 & Ca++ in granulosa cells which is transmitted via gap junctions to oocyte which increases cAMP phosphodiesterase and causes cAMP and PKA to lose activation and OMI no longer functions.
OMI is maintained via ___ and cAMP. Signaling changes from PKA mediated to ___ mediated. Meiosis resumes just prior to____
PKA; PKC; ovulation
PKC targets ____ an oocyte specific kinase, which increases ___ activity (made via cyclin B +CDK1) which targets nuclear lamins and many other proteins and triggers germinal vesicle breakdown and completion of meosis I.
c-mos; MPF
____ synthesis regulates onset of meiosis I
cyclin B
What are cortical granules
At fertilization, they change the zona pellucida and block anymore sperm from coming in
At birth we have a primary oocyte; division of meiosis becomes arrested in prophase I as the primary oocyte grows. Each month after puberty, prior to ovulation, the zona ____ and ____granules form and you get further dev of primary oocyte and maturation in response to ____ and estrogen . ____surge triggers completion of division 1 of meiosis & ovulation and you get a secondary oocyte and first polar body. The secondary oocyte enters meiosis II and arrests at ____ unless there is _____ than you form a second polar body and develop a _____
pellucida; coricol; FSH; LH; metphase II fertilization; zygote
Spermatagonia are located as dormant cells in testicular seminiferous tubules and mature at puberty. Primary spermatocytes enter ____ and then become secondary spermatocytes which then undergo meiosis II and develop ___spermatids where they remain attached via cytoplasmic bridges as they mature into _____
meiosis I; 4; spermatazoa
____ stimulates Sertoli cell secretion of androgen binding protein (ABP) and inhibin which_____. What does inhibin do?
FSH; maintains testosterone at high levels.
Goes back to pituitary and serves as feedback inhibitor so you dont get too much FSH or LH.
___ stimulates Leydig cell secretion of testosterone
LH
____ and ____stimulate final steps of spermatogenesis
testosterone and DHT (dihydrotestosterone)
Spermatagonia divide by ____
mitosis
In nuclear reorganization in sperm, histones are replaced by ____; intensive condensation. Golgi builds an _____. _____organizes in flagella. These events require a _____ genome
protoamines; acrosomal cap which is full of enzymes.
Axoneme. diploid
Differentiation process converting spermatids to mature sperms takes about ____ days total. ____ million sperm mature each day
64 (about 2 months) 300
What is the diff be male sperm and female egg?
Male:
- Have small sperm
- Motile
- no “accessory cells”
- sparse cytoplasm
- 2 types: 23X, 23 Y
Female:
- Have huge egg
- immotile
- have “accessory cells”
- lots of cytoplasm
- 1 type: 23 X
oocyte and follicular fluid are “swept” into fallopian tube via ___ and mucosal cell cilia.
fimbriae
Emission is when sperm is delivered to posterior urethra via peristalsis of ___ ____
ductus deferens. Semen is Stored in epidymis and needs to travel through vas deferens to the urethra.
Semen gets packed up with stuff in the following areas:
seminal vesicle, prostrate and bulbourethral glands
Seminal vesicles provide:
provide fructose, prostaglandins, unique clotting proteins.
How is semen expelled through urethra
bulbospongiosus muscle contraction
Fluid components come from 3 major glands:
- seminal vesicles- 60%
- prostate-25%
- bulbourethral- 10%
What nutrients get packed in prostate? what about bulbourethral gland?
citrate, prostate specific antigen; buffer, mucous
Whats going on during capacitation
- acrosome is cleared of glycoprotein coat and seminal proteins
- sperm become more actively motile
- calcium dependent
- takes 7-10 hours
During fertilization sperm binds to ___ which inc calcium and causes release of acrosomal enzymes which allow allow penetration through ____. When membranes fuse, egg cell membrane depolarizes and causes cortical reaction.
ZP3, Zona Pelucida;
The first calcium spike triggers ____ rxn. _____ is involved in producing perforations in acrosome and fusion of sperm cell membrane with external acrosomal membrane. Hyaluronidase and acrosin released from acrosome to break down the zona pellucida
acrosome; ACE (angiotensin converting enzyme)
The second calcium spike triggers ____ to empty cortical granules .
oocyte
Enzymes in cortical granules cause changes in zona pellucida such as:
- shortening of ZP2, & ZP3; tighter matrix and “hardens” the zona
- changes in ZP3 may render it ineffective as receptor…creating polyspermy.
What happens post fertilization/
- oocyte completes second meiotic div and female pronucleus forms.
- male pronucleus forms
- sperm tail, etc degrades.
- Pronuclei breakdown
- mitotic spindle organizes using centriole components from sperm tail; chromosomes arrange on spindle.
- onset of mitosis
What are some techniques that use assisted fertilization
- IVF
- GIFT: gamete intrafallopian transfer
- ICSI: intracytoplasmic sperm injection; when sperm cant produce enzymes to break down zona pellucida
what factors can lead to male infertility
- sperm count less than 20 million
- sperm motility
- sperm morphologoy
What are ways to tease off single cell from morula and do genetic testing?
Preimplantation genetic diagnosis (PGD)
what can test the ability of human sperm to penetrate zona free hamster egg?
manster test
