Spermatogenesis Flashcards
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
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)
label 1-5 of blastocyst leaving the zona pellucida
which of the following is the gonadal ridge?
1
2
3
4
5
6
7
which of the following is the gonadal ridge?
1
2
3
4
5
6
7
which of the following is the primordial germ cells?
1
2
3
4
5
6
7
which of the following is the primordial germ cells?
1
2
3
4
5
6 red dots
7
which of the following is the primordial germ cells?
1
2
3
4
5
6
7
which of the following is the primordial germ cells?
1
2
3
4
5
6 red dots
7
which of the following is the spermatids?
A
B
C
D
E
F
which of the following is the spermatids?
A
B
C
D
E
F
which of the following is the sertoli cells?
A
B
C
D
E
F
which of the following is the sertoli cells?
A
B
C
D
E
F
which of the following is the 1ary spermatocytes?
A
B
C
D
E
F
which of the following is the 1ary spermatocytes?
A
B
C
D
E
F
which of the following is the 2ary spermatocytes?
A
B
C
D
E
F
which of the following is the 2ary spermatocytes?
A
B
C
D
E
F
which of the following is the spermatozoa?
A
B
C
D
E
F
which of the following is the spermatozoa?
A
B
C
D
E
F
