1. spermatognesis Flashcards
1
Q
what are spermatogonia
A
- stem cells
- PGCs differentiate into as they enter meiosis in foetal gonad
- escape from this fate by diffusible male meiosis inhibitor produced by Sertoli cells in male gonad
- do not proceed until testosterone in puberty
- spermatogenesis proceeds throughout adult life
2
Q
semen/seminal fluid
A
- contains the spermatozoa + liquid component derived from the glands
3
Q
male gonads
A
- genital excurrent ducts
- accessory sex glands
- external genitalia
gonads are endocrine glands: hormones produced by Leydig cells in interstitial (stromal) tissue
4
Q
semiferous tubules
A
- parenchyma of testis
- surrounded by myoid cells: tubule wall
-wall: germinal epithelium: seminiferous epithelium: sertoli cells (somatic) and spermatogenic cells (germ line)
5
Q
leydig cells
A
- well developed lipid metabolism
- abundant SER, many LD, glycogen, golgi, lysosomes, occasional RER
- secrete testosterone initiating spermatogenesis
- stimulated accessory sex gland secretion, secondary sec characters, metabolism
- in embryo (2-5mo) testo required for normal gonad development: insulin-like 3 stimulates testis descent
6
Q
sperm cells
A
- adapted for delivering haploid DNA to an egg
- highly specialised cells by differentiation
7
Q
where does spermatogenesis occur?
A
in the seminiferous tubules
8
Q
sertoli cells strcucture
A
- post-mitotic after puberty
- extend through full thickness of seminiferous epithelium with extensive processes
- surround and envelope spermatogenic cells
- form tight junctions in epithelium: determine basal and luminal compartment
8
Q
spermatogenic cells
A
- undergo mitosis/meiosis,
- organised in poorly defined layers from the wall (spermatogonia) to the lumen (spermatids) of semini tubule
9
Q
sertoli cells function
A
- support gametogensis
- create a niche for germ cells
- account for the testicular immune privilge
10
Q
three phases of spermatogenesis
A
- spermatogonial phases (mitotic amplification): spermatogonia
- spermatocyte phase (meiosis): primary, secondary spermatocytes, spermatids
- spermatid phase (spermiogenesis, differentiation): golgi, cap, acrosome, maturation phase
- spermatozoon formed
11
Q
spermatogonial phases (mitotic amplification)
A
- type A dark are spermatogonial stem cells: dormant and increase in number at puberty
- type A pale are renewing stem cells
- cytoplasmic division complete only in type A dark, all other remain connected by intercellular bridges
- type B are committed to give rise to spermatocytes: not stem cells any longer
12
Q
spermatocyte phase (meiosis)
A
- spermatocytes undergo meiosis generating four spermatids
13
Q
spermatid phase (spermiogenesis)
A
- spermatids are transformed into mature sperm (differentiation
- seperate into individual spermatozoa as they are released from seminiferous epithelium
- residual bodies remain connected: phagocytosed by sertoli cells
1. acrosome formation
2. modifications of nucleus (chromatin compaction) and cell shape (cytoplasm reduction)
3. tail formation
4. release into the lumen - golgi,cap,acrosome,maturation phase
14
Q
the acrosome
A
- organelle for massive exocytosis
- cap-like saccular organelle in head
- wraps 2/3 of nucleus
- contains hyaluronidase, neuroaminidase, acid phosphatase, acrosin (trypsin-like protease)
- from golgi
