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ANAT 381 > Making Sperm > Flashcards

Making Sperm Flashcards

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
Q

describe differences between spermatogenesis and oogenesis - meiosis timings

A

oog = meiosis 1 before fertilization, meiosis 2 after
sperma = both meiotic divisions precede fertilization

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26
Q

describe/compare products of both oogensis and spermatogenesis

A

oogenesis = 1st meiosis produces 1 polar body, 2nd meiosis produced another polar body, ends up with one gamete
sperma = 4 half gametes

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27
Q

name the 3 stages of spermatogenesis

A

mitotic proliferation
meiosis including both meiotic divisions
morphological changes (spermiogenesis)

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28
Q

what are ssc - describe

A

spermatogenic sperm cell
cell that has ability to divide
typically produces one stem cell and 2nd daughter cell differentiates to another cell

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29
Q

where do the ssc live - describe

A

reside in niche - location that supports stem cells
located near bm of seminiferous tubule
close to periphery

30
Q

where is the niche close to - explain

A

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
Q

spermatogenesis - mouse vs human - amount of time

A

mouse = 35d
human = 75d

32
Q

describe whole of spermatogenesis - gen

A

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
Q

describe sperm output - from mice to men

A

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
Q

describe luminal progression

A

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
Q

why is luminal progression useful

A

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
Q

describe tight junctions - spermatogenesis

A

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
Q

what is on outside vs inside of tjs

A

sperm and spermatogonia on OUTSIDE
spermatocytes and spermatids on INSIDE

38
Q

describe sertoli cells

A

have fsh receptor,
responsive to testosterone produced by leydig cells
essential for process of sperm development to be completed

39
Q

what is sperm production in adults proportional to

A

number of sertoli cells generated during fetal life
if have many sertoli cells = will make lots of sperm

40
Q

describe leydig cells

A

has lh receptor
produced testosterone
testosterone <–> dihydrotestosterone via 5alpha reductase
estradiol to <–> testosterone (androstenedione) via 17beta-hsd
testosterone <–> estrone (then estradiol) via aromatase

41
Q

how much testosterone do leydig cells produce

A

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
Q

when are androgens required during spermatogenesis

A

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
Q

describe in vitro systems for studying spermatogeneis

A

not as developed as for study of oocytes

44
Q

where are ssc located

A

near periphery of seminiferous tubules

45
Q

where are sertoli cells located

A

inside seminiferous tubules

46
Q

which cell type produces testosterone

A

leydig

47
Q

describe spermiogenesis

A

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
Q

describe major elements of mature sperm - acrosome - informally

A

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
Q

what does acrosome cover

A

Anterior half of nucleus

50
Q

what is acrosome derived from

A

golgi

51
Q

what happens to acrosme during fertilization

A

outer membrane fuses with plasma membrane releasing acrosomal contents

52
Q

what does acrosome contain

A

numerous enzymes typical of lysosomes
acrosin = inactive proacrosin converted to active form by acrosome reaction
hyaluronidase = breaks down cumuls cell matrix surrounding egg

53
Q

describe length of sperm tail

A

55 mu m long in humans (sperm = 60 mu m)

54
Q

what does tail have/how its organized

A

typical structure axonemes - microtubules arranged in 9+2 structure
outer dense fibers
mitochodria

55
Q

describe nucleus of sperm - gen

A

most unique part of sperm
Extremely condense dna = <5% of somatic volume - non nucleosomal
shrunken, compacted dense bundle

56
Q

is nucleus of sperm transcriptionally active

A

no inactive

57
Q

describe major elements of mature sperm - nucleus - histones and stuff

A

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
Q

describe chromatin structure - generally usually - standard

A

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
Q

describe nucleoprotein transitions during spermiogenesis

A

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
Q

are all regions of sperm dna replaced by protamines

A

nooo
some regions of sperm dna that retain their histones, despite widespread condensation and replacement of histones, selective retention

61
Q

how much of sperm dna remains associated with histones

A

~15% in humans

62
Q

you are what your father eats = describe

A

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
Q

describe transgenerational epigenetic inheritance

A

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
Q

what is msci/msuc

A

meiotic sex chromosome inactivation = msci
meiotic silencing of unpaired chromatin = msuc

65
Q

describe meiosis - pairing at pachytene - msci

A

mediated by proteins known as synaptonemal complex
proteins - pairing happens in sperm and egg

66
Q

describe what happens when x and y chroms paired together - msci - specifically

A

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
Q

describe meiosis in males - msci

A

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
Q

describe consequences of msci - what actually happens

A

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
Q

what does failure of msci cause

A

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
Q

describe xyy - msci

A

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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