Making sperm Flashcards
Germ cells become enclosed by the ____________ cells
Sertoli
Sertoli cells are found ____________ the seminiferous tubules
Inside
Leydig cells are found ______________ the seminiferous tubules
Outside
Where does spermatogenesis occur?
Seminiferous tubules
How much sperm is produced daily?
150-300 million
What is the site of sperm maturation and transport?
Epididymis
What is the site of sperm transport?
Vas deferens
What is the precursor of the male reproductive tract?
Wolffian duct
Match the descriptions to either Sertoli or Leydig cells:
a) Synthesize steroids; testosterone and estrogen
b) Harbor and support developing germ cells
a) Leydig cells
b) Sertoli cells
What is the length of the seminiferous tubules?
250 m/ testis
What are the similarities between Sertoli and granulosa cells?
Derived from the same precursor cells in embryonic gonad
In direct contact with and supporting developing germ cells
Express FSH receptors
What are the similarities between Leydig and theca cells?
Derived from interstitial cells of embryonic gonad
Are not in direct contact with germ cells
Express LH receptors
Produce testosterone
Identify the following with either oogenesis or spermatogenesis
a) All germ cells produced before birth
b) Germ cells enter meiosis throughout reproductive life
c) Meiosis I before fertilization; meiosis II after
d) Growth and maturation require 3-4 months in humans
a) Oogenesis
b) Spermatogenesis
c) Oogenesis
d) Oogenesis
How many gametes are produced at the end of oogenesis and spermatogenesis?
Oogenesis: one
Spermatogenesis: four
What is SSC?
Spermatogenic stem cell that has the ability to divide
It produces one stem cell and another committed differentiating cell
How long does spermatogenesis take in mouse vs in humans?
Mouse: 35 days
Human: 75 days
What triggers meiotic division?
Retinoic acid
In spermiogenesis, spermatids are ___________
Haploid
Place the following species in order of most to least sperm output: Humans, monkeys, rodents
Monkeys, rodents, humans
Where do stem cells reside?
A niche
Where is the niche located?
Near the basement membrane of the seminiferous tubule
What factor does Leydig cells provide to SSC in the niche?
CSF1
What factors are provided for progenitor spermatogonia?
BMP1 and neuregulin 1
What factors from the Sertoli cells are provided to the SSC?
GDNF and FGF2
What is the problem of tight junctions?
Spermatocytes need to pass through the gap junctions to get to the lumen and would need to be disassembled
What is the first cell to differentiate in testis?
Sertoli cell
______-chromosome is required to make a Sertoli cell
Y
Sperm production in adults is proportional to the number of ___________ cells generated during fetal life
Sertoli
Leydig cells produce _____________ mg of testosterone per day
3-10
Leydig cells are responsible for __________% of the total testosterone production
95
What are some features of the acrosome of the mature sperm?
Covers anterior half of nucleus, derived from Golgi, outer membrane fuses with PM releasing acrosomal contents
What are the two enzymes typical of lysosomes in acrosomes?
Acrosin and hyaluronidase
What are some features of the tail of sperm?
55 micrometers long in humans, microtubules arranged in 9+2 structure typical of axonemes, outer dense fibres, mitochondria
What are some features of the nucleus of sperm?
Extremely condensed DNA, transcriptionally inactive, histones replaced by protamines (rich in arginine and cysteine)
Histones are associated with which stage of spermatogenesis?
Mitotic phase, meiosis and post-meiotic phase
Transition proteins are associated with which stage of spermatogenesis?
Post-meiotic phase and spermiogenesis
Protamines are associated with which stage of spermatogenesis?
Spermiogenesis
Chromosome pairing occurs at ________________
Pachytene
X and Y chromosomes do not ______________ over most of their length
Synapse
Why are unpaired X and Y chromosomes transcriptionally silent?
The chromatin is unpaired
What are the consequences of MSCI?
Autosomal genes encoding homologues of X-encoded genes become transcriptionally active in meiotic sperm cells
Failure of MSCI causes cell death
XXY -> synapsis of Y-chr -> expression of Y-encoded genes -> sterility
How is MSCI mediated?
BRCA1 leads to chromosome inactivation
BRCA1 activates ATR, ATR phosphorylates H2A.X which activates transcriptional silencing
