Embryology Week 1 Flashcards
What is oogenesis?
formation of eggs
What is spermatogenesis?
formation of sperm
Where does spermatogenesis occur?
seminiferous tubules
What are spermatogonia?
primordial germ cells
What are the 3 major spermatogenesis steps?
- mitotic proliferation 2. meiosis 3. packaging
What happens in mitotic proliferation?
each spermatogonium duplicates to form Type A and Type B daughter spermatogonia
What are type A spermatogonia cells?
undergo self renewal and reserve stem cell
What and where does type B become what it needs to be?
pushed toward lumen where it becomes a primary spermatocyte - destined to produce 4 sperms
What does the primary spermatocyte become after it undergoes meiosis 1?
2 secondary spermatocytes - haploid cells
What does it then become after meiosis 2?
4 spermatids
What is spermiogenesis?
differentiation of newly formed spermatids to spermatozoon
What is the function of sertoli cells?
- provide nutrients for spermatds 2. help shed superfluous cytoplasmic baggage
What does the head of the sperm contain?
haploid nucleus + acrosome with hydrolytic enzymes + protamines
What does the midpiece contain?
mitochondria
What does the tail contain?
flagellum for locomotion
Explain the Kartagener Triad?
no dynein - defective movement of cilia
Effect of Kartagener Syndrome?
- recurrent chest infections - bronchial infections 2. ear/nose/throat symptons 3. heart on the right side - dextrocardia
Which sperm is less resistant to acidic condition? LY - lie
Y sperm
Which sperm is more resistant to acidic condition? MX - mix
X sperm
When does oogenesis begin?
before birth - primordial germ cells differentiate into oogonia
When does oogenesis occur?
after primordial germ cells arrive in ovary
In the 3rd week where do primordial germ cells appear?
wall of the yolk sac - close to allantois
Where do the primordial germ cells move along?
migrate along dorsal mesentry of the hindgut - to invade genital ridges
What is atresia?
the process that occurs when oogonia stops and never resumes, but cell death happens
What is fertilization? Where does it occur?
process by which male and female gametes fuse - occurs in ampullary region of uterine tube
What 2 processes occur before fertilization can occur?
- capacitation 2. acrosome reaction
What is capacitation? GASIC
period of sperm conditioning in female reproductive tract - membranes more unstable 1. glycoprotein coat + seminal plasma proteins are removed from plasma membrane on acrosomal region 2. acrosomal stabalizing factor removed 3. sperm surface proteins phosphorylated 4. ion and pH change 5. cholesterols removed from membrane
What is removed from acrosomal region from the plasma membrane?
glycoprotein coat and seminal plasma proteins
What is removed from the membrane?
cholesterols
What happens to the sperm surface proteins?
phosphorylated
Where does capacitated sperm pass through?
corona radiata
When does acrosome reaction take place?
after sperm bind to zona pellucida
What is it induced by?
zona proteins - ZP1, ZP2, ZP3
What enzymes cause this?
- acrosin 2. trypsin-like substances 3. hyaluronidase 4. acid phosphotase 5. collagenase
What are the phases of fertilization?
- penetration of corona radiata 2. penetration of zona pellucida 3. fusion of oocyte and sperm cell membranes
How do other sperm help fertilizing sperm in penetrating barriers?
help fertilizing sperm in penetrating barriers using hyaluronidase
What is Zona pellucida made out of?
glycoproteins + glycosaminoglycans
What are 2 functions of zona pellucida?
- facilitate sperm binding 2. induce acrosome reaction - release of acrosin allows sperm to penetrate zona pellucida
What changes when sperm head touches oocyte?
permeability of zona pellucida
What is released when the sperm head touches oocyte?
enzymes are released by cortical granules lining plasma membrane of oocyte
What are the 3 functions of what is released?
- alter properties of zona pellucida 2. prevent sperm penetration 3. inactivate species specific receptor sites for sperm on zona surface -ZP3
What promotes membrane fusion of sperm and oocyte?
fertilin, integrin, CRISP
What parts of the sperm enter the oocyte?
head + tail - cell membrane left behind on oocyte surface
Why does zona pellucida change its structure?
- prevent sperm binding 2. prevent sperm penetration and polspermy
What is the slow block?
cortical or zonal reaction - acid mucopolysaccharides, peroxidase crosslinks, hyaline, ZP3 modification
What is the fast block?
change of membrane electrical potential
What are the stages of resumption of second meitotic division?
- finishes second meiotic division 2. cytostatic factor arrests cell at this stage 3. fertilization leads to Ca2+ influx 4. Ca2+ activates calmodulin 5. calmodulin activates CSF degrading enzymes - leading to metabolic activation of the egg
What are the 2 parts that phospholidase C cleaves membrane lipid to?
DAG & IP3 (Di-acetyl-Glycerol & Inositol triphosphate)
Function of DAG nad IP3?
- oxygen consumption increases 2. DNA synthesis/replication begins 3. protein synthesis begins 4. rearrangement of cytoplasm - new interactions and new neighbours will activate other molecules
What are the consequences of fertilization?
- completion of meiotic division II of ovum 2. activation of egg for development 3. restoration of diploid number of chromosomes 4. determination of sex 5. initiation of cleavage
What does the zygote become?
blastula
When the morula has a cavity what is it called?
blastocele
What does inner cell mass give rise to?
embryoblast - embryo proper
What does outer cell mass give rise to?
trophoblast - contributes to placenta
What does the trophoblast differentiate into?
- cytotrophoblasts - small non-multinucleated cells : form villi that branch, mesodermal cells aline to form capillaries that go into lacuna carrying fetal blood 2. syncytiotrophoblast - multinucleated : erode endometrium forming lacuna into which maternal blood flows
By the end of week one what happens?
human zygote has passed through morula and blastocyst stages + begun implantation in uterine mucosa
Descibe implantation
- contact of trophoblast with uterine epithelium 2. apposition - adhesion - penetration - implantation 3. blastocyst is embedded in endometrium
Implantation is completed by?
end of week 2 - uteroplacental circulation is established
What are the characteristic of a receptive uterus?
- short irregular sparse microvilli on uterine epithelial cells 2. many large surface protrusions 3. few uterine folds 4. reduced surface glycocalyx 5. raised apices and flat borders 6. focal adhesions disassemble from the base of the epithelium and relocate apically
Describe placenta development?
- 6 days after fertilization blastocysts attaches to endometrium 2. trophoblastic cells proliferate and differentiate
What do trophoblastic cells differentiate into?
- cytotrophoblast - inner layer (mitotically active) 2. syncytiotrophoblast - outer mass (mitotically inactive) : invades endometrial epithelium
Function of syncytiotrophoblast?
1.erodes stroma 2. erodes maternal capillaries 3. produces human chorionic gonadotrophin - hCG
How are lacunae formed?
- Lacunae are filled with maternal blood +debris of eroded uterine glands 2. Communications between eroded endometrium capillaries and lacunae form the primordial utero-placental circulation
