what are the 4 stages of gametogenesis? [4]
- extraembryonic origin of germ cells and migration to gonads
- increase in germ cell number by mitosis
- reduction in chromosome number by meiosis
- structural and functional maturation into eggs and sperm
where do germ cells originate in the embryo? [1]
where do germ cells migrate to? [1]
where do germ cells originate in the embryo? [1]
epiblast
where do germ cells migrate to? [1]
genital ridge (areas responsible for creation of m / f reproductive system)
what happens when germ cells migrate to the genital ridge? [1]
what happens when germ cells migrate to the genital ridge? [1]
- germ cells become surroundered by proliferating epithelial cells
- they extended into gonad to form primitive sex cords
how does the formation of the seminiferous tubules occur?
- primitive sex cords lose connection to surface of gonad
- SRY gene causes primitive cords to proliferate and penetrate deep into medulla: form testis
- at the surface: epithelium thickens to form tunica alubignea
- cords: become seminferous tubules
explain the process of spermatogenesis :)
- spermatogonial stem cells (SSC) (from primordial germinal cells) undergoes mitosis: 2 daughter cells
- one daughter = stays as SSC
- other daughter = causes mitotic amplification = distinct spermatogonia type A & B
- testosterone level increasse which initiates meiosis I
- primary spermatocyte –> two secondary spermatocytes & undergo meisois II –> 4 spermatids (haploid)
- spermatids mature into spermatozoa
when does spermatogenesis start? [1]
during puberty
which hormones stimulate spermatogenesis? [3]
- Gonadotropin releasing hormone (GnRH) stimulates FSH & LH from AP
- LH stimulates testosterone production by Leydig cells
- Main target of testosterone and pituitary FSH are Sertoli cells
- Sertoli cells then secrete androgen binding protein (ABP) and tubular fluid
- ABP binds to testosterone & carries it to area of seminiferous tubule where it stimulates spermatogenesis
which structural changes occur from spermatid to spermatozoa? [3]
which structural changes occur from spermatid to spermatozoa?
developed acrosome: covers half the nuclear surface & contains enzymes to assist penetration of egg
condensation of nucleus
formation of middle piece and tale
Golgi apparatus condenses to form acrosome, which as digestive enzymes to break down the egg wall
Reduction in nuclear size
what is the difference in location of cells during spermatogenesis? (i.e. where do you find spermatogonia –> mature sperm?)
The development of the germ cells:
spermatogonia at the periphery of the seminiferous tubule
advances towards the lumen during which time they become 1ary spermatocytes, 2ary spermatocytes, spermatids and finally mature sperm.
what is capacitation?
The final step of sperm maturation, takes place within the female genital tract and requires contact with the secretions of the oviduct.
It is part of a series of physiological processes which allows the sperm to fertilise the egg, removal of the glycoprotein coat.
** what are the 6 essential stages that need to be functioning for fertilisation to occur? [6] **
- Functioning hypothalamic-pituitary-gonadal axis
- Normal oogenesis & spermatogenesis
- Normal structure and function of reproductive tract
- Trouble free transport of gametes
- Gamete fusion
- Trouble free transport of embryo
what changes to the cervix mucuous occur during ovulation? [2]
sperm hostile to sperm friendly: mucus less viscous and alkaline –> highly viscous & acidic
the sperm acrosome is formed which organelle?
nucleus
ribosome
SER
golgi apparatus
lysosome
the sperm acrosome is formed which organelle?
nucleus
ribosome
SER
golgi apparatus
lysosome
label 1-8 of the seminiferous tubule
why cant sperm taken form a lumen of a seminiferous tubule fertilise an egg? [1]
why cant sperm taken form a lumen of a seminiferous tubule fertilise an egg? [1]
it hasnt undergone capacitation in female yet
sperm deposition and transport:
- where is sperm depositied in the female? [1]
- what characterisitc of female genital tract assists sperm movement? [1]
- how long goes sperm transport to uterus take? [1]
- what happens to sperm during transport to uterus? [2]
sperm deposition and transport:
- where is sperm depositied in the female? [1]
- *cervical os**
- what characterisitc of female genital tract assists sperm movement? [1]
- *ciliated surface of cervical os**
- how long goes sperm transport to uterus take? [1]
- *2-7 hrs**
- what happens to sperm during transport to uterus? [2]
capacitation;
sperm become hyperactive and sensitive to surrounding signals
label 1-3 of oocyte that has just left the ovary [3]
1 centre of oocyte
2. corona radiate
3 head of spermatozoon
explain the mechanism of how an egg is fertilised [7]
- Sperm finds egg
- Sperm recognises egg.
- Sperm has acrosome reaction to penetrate extracellular layer
- Sperm cell membrane fuses with egg cell membrane and triggers Ca2+ wave in egg.
- Polyspermy is blocked.
- Fertilisation cone forms around sperm head.
- Movement and fusion of pronuclei.
explain mechanism of acrosome reaction & egg / sperm fusion
The acrosome membrane fuses with the overlying plasma membrane
Enzymes released that degrade ZP and allow passage through zona pellucida
Sperm nucleus is now exposed - but only the head can pass through
Sperm finishes its journey between the zona pellucida and the oocyte membrane (oolemma)
Sperm becomes enveloped, Fusion occurs - mechanism unknown
Large increase in intracellular Ca2+ which forms a wave across the egg (mechanism uncertain – few candidates)
_How do the egg and sperm find each other? [2]
How do the cells fuse with each other in a species-specific way?_
How do the egg and sperm find each other? [2]
Sperm attracted to egg via chemotaxis
Only found in mature eggs and sperm
How do the cells fuse with each other in a species-specific way?
In mammals:
- A glycoprotein called ZP3
- Found in the zona pellucida
- Binds to β1, 4 galactosyl transferase receptor on the sperm plasma membrane
- Capacitated sperm are species-specific in their binding to ZP3
- Binding triggers changes in Ca2+ and pH in sperm and acrosome reaction
How is the number of cells fusing restricted?
Production of second messengers on sperm/egg binding triggers polyspermy blocking.
Slow block: release of calcium in a wave that occurs on fertilisation.
- Calcium triggers **cortical granule
- Release and activation of cell division**
where does the Fertilised ovum travel to? [1]
what processes are happening during this transport? [1]
Process of gestation:
where does the Fertilised ovum travel to? [1]
to fallopian tube/ oviduct
what processes are happening during this transport? [1]
fertilised oocyte becomes a zygote: starts to divide. cleaves to form 2 cells
during zygote division:
what is the name for the cells and what happens at 16-32 cell stage? [2]
what is the name for the cells and what happens at 32-64 cell stage? [3]
during zygote division:
what happens at 16-32 cell stage? [2]
- *is called a morula:**
- outer cells form one populaton and are trophoblastic precursors
- inner cells are pluriblast cells
what happens at 32-64 cell stage? [2]
- *is called a blastocyte:**
- cell types start differentiating
- at day 5 blastocyte frees itself from zona pellucida: hatching
how many days after ovulation does blastocyte attach to uterine wall?
7-9 days
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OOGENESIS AND THE HISTOLOGY OF THE FEMALE REPRODUCTIVE SYSTEM5
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Spermatogenesis36
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Histology of male reproductive system - testis21
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Anatomy 137
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Implantation & placental function33
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Endocrinology of the placenta7
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The development and sexual differentiation of the reproductive system40
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Contraception41
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Physiological adaptations in pregnancy30
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Congenital defects and human embryology28
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HD SM notes99
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Anatomy 287
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Reproductive endocrinology and menstrual21
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Labour14
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Development of abilities in children14
