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ANAT 381 > Making Sperm > Flashcards

Making Sperm Flashcards

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1
Q

describe early embryonic development of testis - gen

A

early development of seminiferous tubules - 2 principle types of cells = germ cells and sertoli cells (encircled by germ cells, first cells to be specified by sry/sox9)

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2
Q

describe early embryonic development of testis - layers and specific cells

A

tunica albuginea = hard shell of testis
flcs = fetal leydig cells, outside seminiferous tubules
pmcs= peripheral myoid cells - gives structure to seminiferous tubules (elongated cells)

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3
Q

describe early embryonic development of testis - germ cells and vasculature

A

germ cells = not super organized, but see the 2 cell types
vasculature = red cells = blood vessels, around outer edge and poke down into seminiferous tubules

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4
Q

name parts of anatomy of male reproductive system

A

seminiferous tubules
epididymis
vas derens

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5
Q

describe seminiferous tubules

A

250m/testis
sperm production
150-300 mil/day
very long and narrow compartmentalized, spermatogenesis happens here

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6
Q

describe epididymis

A

has head, body and tail
sperm maturation and transport
tightly coiled
once sperm mature= complete differentiation and pass to epididymis

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7
Q

describe vas deferens

A

sperm transport
functionally competent now

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8
Q

when do sperm acquire motility

A

when pass through epididymis
factors or secretions give them motility

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9
Q

is the sperm in the testis functional - explain

A

yessss
ones in testis = cannot swim well, but do not need to swim to be functional gamete
can use for icsi - inject into egg

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10
Q

describe development of reproductive tract - gen overview

A

all embryos begin with precursors of male and female
then specifies
leydig cells produce testosterone = wolffian ducts
testis produce amh = inhibits mullerian ducts
*at this stage and location no testosterone in females

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11
Q

describe germ cells - history too

A

antoine van leeunwenhoek (1632-1723)
identified germ cells
could see sperm swimming around

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12
Q

describe preformationism - history too

A

proposed by nicolaas hartsoeker (1656-1725)
idea that embryo was directly formed in sperm
egg produced placenta and embryo came from sperm
egg provides nutrients
preformed babies for generations

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13
Q

describe setoli cells - history too

A

enrico sertoli (1842-1910)
inside seminiferous tubules
role = harbour and support developing germ cells

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14
Q

describe leydig cells - history too

A

outside seminiferous tubules
synthesize steroids - testosterone and some estrogen

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15
Q

describe structure of seminiferous tubules - histology components

A

spermatids near lumen
primary spermatocytes
spermatogonia
sertoli cells= close to periphery, have characteristic shape and staining of nuclei
peritubular myoid = cell, very stretched around outside
leydig cells = exist between seminiferous tubules, outside the seminiferous tubules

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16
Q

how many m of seminiferous tubules/man

A

250m/man
many seminiferous tubules
to 500m

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17
Q

name cells that are similar between spermatogenesis and oogenesis

A

sertoli and granulosa
leydig and theca

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18
Q

describe how sertoli and granulosa cells are similar (between spermatogenesis and oogenesis)

A

derived from same precursor cells in embryonic gonad
in direct contact with and support developing germ cells
expresss fsh receptors

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19
Q

describe how leydig and theca cells are similar (between spermatogenesis and oogenesis)

A

derived from interstitial (cells that are not any other kind of cell) cells of embryonic gonad
are not in direct contact with germ cells
express lh receptors
produce testosterone

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20
Q

describe differences between spermatogenesis and oogenesis - all germ cells

A

oog = all germ cells produced before birth
sperma = new germ cells produced throughout reproductive live (>100mil news sperm/day = >1000/second), estimate, up to 300mil

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21
Q

describe differences between spermatogenesis and oogenesis - germ line stem cells

A

oog = no germ line stem cells after birth
sperma = germ line stem cells throughout reproductive life (that give rise to sperm, create new sperm at high levels for whole reproductive life)

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22
Q

describe differences between spermatogenesis and oogenesis - meiosis

A

oog = enter meiosis before birth
sperma = germ cells enter meiosis throughout reproductive life (as part of differentiation)

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23
Q

describe differences between spermatogenesis and oogenesis - growth and maturation

A

oog = requires 3-4 months
sperma = requires ~2.5 (2-3) months

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24
Q

describe differences between spermatogenesis and oogenesis - support

A

oog = many granulose cells support one germ cell
sperma = one sertoli cell supports many germ cells

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25
describe differences between spermatogenesis and oogenesis - meiosis timings
oog = meiosis 1 before fertilization, meiosis 2 after sperma = both meiotic divisions precede fertilization
26
describe/compare products of both oogensis and spermatogenesis
oogenesis = 1st meiosis produces 1 polar body, 2nd meiosis produced another polar body, ends up with one gamete sperma = 4 half gametes
27
name the 3 stages of spermatogenesis
mitotic proliferation meiosis including both meiotic divisions morphological changes (spermiogenesis)
28
what are ssc - describe
spermatogenic sperm cell cell that has ability to divide typically produces one stem cell and 2nd daughter cell differentiates to another cell
29
where do the ssc live - describe
reside in niche - location that supports stem cells located near bm of seminiferous tubule close to periphery
30
where is the niche close to - explain
blood vessels outside seminiferous tubules may be releasing growth factors, niche exists close to this blood vessel, or cells that provide growth factors - molecules for stem cells to divide and live and sustain sperm production for many years bmp4 and neuregulin 1 (source unknown)
31
spermatogenesis - mouse vs human - amount of time
mouse = 35d human = 75d
32
describe whole of spermatogenesis - gen
type A1 spermatogonia type A2 spermatogonia type A3 spermatogonia type A4 spermatogonia (histologically different, undergo mitotic amplification, not as much in humans tho, increase number of cells by mitotic divisions) intermediate spermatogonia type B spermatogonia = enter meiosis, triggered by retinoic acid, tells mitotic cells to undergo meiotic division after 1st meiotic division = primary spermatocytes after 2nd meiotic division = secondary spermatocytes 2nd meiotic divisions then called spermatids, haploid = spermiogenesis, generates mature sperm
33
describe sperm output - from mice to men
rodent = 40mil sperm/gram testis tissue/day monkey = 41 mil sperm/gram testis tissue/day human = 4.4 mil sperm/gram testis tissue/day- humans have less amplification divisions
34
describe luminal progression
as enter meiosis, 1st and 2nd divisions and spermiogenesis = moving in seminiferous tubules begin in niche as ssc, then after divides to type A spermatogonia = located at periphery of seminiferous tubules, as undergoing process = move from periphery to center of seminiferous tubules must cross through tight junctions
35
why is luminal progression useful
allows mature sperm to be located in lumen of seminiferous tubule then transferred out to epididymis and vas deferens brings sperm to right place
36
describe tight junctions - spermatogenesis
sertoli cells linked to each other by tjs, sticks cell close together, not much can get inbetween must pass through tjs = tjs much become disassembled, so things can pass through, transiently disassembled- they must
37
what is on outside vs inside of tjs
sperm and spermatogonia on OUTSIDE spermatocytes and spermatids on INSIDE
38
describe sertoli cells
have fsh receptor, responsive to testosterone produced by leydig cells essential for process of sperm development to be completed
39
what is sperm production in adults proportional to
number of sertoli cells generated during fetal life if have many sertoli cells = will make lots of sperm
40
describe leydig cells
has lh receptor produced testosterone testosterone <--> dihydrotestosterone via 5alpha reductase estradiol to <--> testosterone (androstenedione) via 17beta-hsd testosterone <--> estrone (then estradiol) via aromatase
41
how much testosterone do leydig cells produce
3-10mg of T per day= lots 95%of total testosterone produced by male (other 5% = adrenals) supports spermatogenesis but also development of secondary sex characteristics
42
when are androgens required during spermatogenesis
around second meiotic division (after 1st) and when making spermatids = spermiogenesis when no androgens or receptors for them = sperm differentiation process blocked, cannot produce functional mature sperm
43
describe in vitro systems for studying spermatogeneis
not as developed as for study of oocytes
44
where are ssc located
near periphery of seminiferous tubules
45
where are sertoli cells located
inside seminiferous tubules
46
which cell type produces testosterone
leydig
47
describe spermiogenesis
big morphological reshaping of sperm extensive cellular remodelling - sheds cytoplasm, remodels and end up with sperm = tail (produces motion, prinicipal piece and mid piece with mitochondrial sheath) and head = acrosome and dna
48
describe major elements of mature sperm - acrosome - informally
bag of enzymes Contains factors sperm will need to penetrate protective coat around around - to bind with egg at fertilization factors that enable fertilization in acrosome - bag, so will not be lost or used to early
49
what does acrosome cover
Anterior half of nucleus
50
what is acrosome derived from
golgi
51
what happens to acrosme during fertilization
outer membrane fuses with plasma membrane releasing acrosomal contents
52
what does acrosome contain
numerous enzymes typical of lysosomes acrosin = inactive proacrosin converted to active form by acrosome reaction hyaluronidase = breaks down cumuls cell matrix surrounding egg
53
describe length of sperm tail
55 mu m long in humans (sperm = 60 mu m)
54
what does tail have/how its organized
typical structure axonemes - microtubules arranged in 9+2 structure outer dense fibers mitochodria
55
describe nucleus of sperm - gen
most unique part of sperm Extremely condense dna = <5% of somatic volume - non nucleosomal shrunken, compacted dense bundle
56
is nucleus of sperm transcriptionally active
no inactive
57
describe major elements of mature sperm - nucleus - histones and stuff
histones mainly replaced with protamines = sperm specific basic proteins histones = rich in lysines (+), helps neg charge dna bind, histones replaced by protamines rich in arginine and cysteine protamines = + charge, can bind to dna protamines do not organize dna into nucleosomes
58
describe chromatin structure - generally usually - standard
nucleosomal structure dna wraps around octamers, consists of 2 molecules at each of core histones h2,h3,h3,h4 histone 1 at some place linker histones between histone all of this lost in mature sperm
59
describe nucleoprotein transitions during spermiogenesis
during mitotic phase and meiosis = meiosis/early differentiation = dna organized in typical fashion = active = histones then post meiotic phase = replaced by transition proteins then during spermiogenesis = protamines
60
are all regions of sperm dna replaced by protamines
nooo some regions of sperm dna that retain their histones, despite widespread condensation and replacement of histones, selective retention
61
how much of sperm dna remains associated with histones
~15% in humans
62
you are what your father eats = describe
if eat healthy = histones retained on certain regions of dna - important significance for gene expression after fertilization if bad diet = maybe histones retained on incorrect parts of dna, remains associated with wrong dna and influences expression of paternal chromatin after fertilization also could apply to environment/pollution mans sperm structure could change in non genetic way = affect embryo gene expression (phenotypic development)
63
describe transgenerational epigenetic inheritance
origin of you are what your father eats p gen = mouse with specific mutation in kit gene - white spotted phenotype f1 gen = some carry mutation, some carry 2 wild type genes = idea that maybe no mutation but sperm modified so get white phenotype
64
what is msci/msuc
meiotic sex chromosome inactivation = msci meiotic silencing of unpaired chromatin = msuc
65
describe meiosis - pairing at pachytene - msci
mediated by proteins known as synaptonemal complex proteins - pairing happens in sperm and egg
66
describe what happens when x and y chroms paired together - msci - specifically
since unpaired chromatin = same would happen if autosomal chroms do not pair essential genes on unpaired x (not so much y) catastrophic of silenced for sperm production = bc many cells need these genes for life
66
describe meiosis in males - msci
somatic chromosomes = pair normally 2 x chromosomes = pair normally x and y chromosomes = do not synapse over most of their length, not 2 homologs, only pair at end= pseudoautosomal region - with enough similarities, but no pairing on rest of x = transcriptional silencing on unpaired portion
67
describe consequences of msci - what actually happens
happens during spermatogenesis bc of dependence on synapsing = so sperm rescue themselves autosomal genes encoding homologues of x encoded genes become transcriptionally active in meiotic sperm cells = activates and helps compensate normally silenced by in meiotic sperm cells = becomes active to compensate for silencing of genes on x chrom x becomes silence and genes on autosome turn on - gene product transcribed off similar gene
68
what does failure of msci cause
cell death if gene not silenced = over production of gene bc still will turn on the autosomal genes to compensate, can occur during pachytene = death
69
describe xyy - msci
xyy --> synapsis of y chrom (bc in early meiosis = abnormal expression of y encoded genes)--> expression of y encoded genes (but should be silenced) --> sterility (only in sperm cells, genes should not be on)

ANAT 381 (24 decks)

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