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Reproductive and Developmental Biology > Lecture 4 (2b) - Male Reproductive Systems > Flashcards

Lecture 4 (2b) - Male Reproductive Systems Flashcards

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1
Q

Aquatic invertebrates

A
  • predominantly external fertilization
    • eg echinoderms
  • cephalopod molluscs - hectocotylus delivers the spermatophore into the female mantle
  • octopus with specialized tentacle into female mantle
  • more efficient/less sperm if internal fertlization
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2
Q

Cephalopod molluscs

…. delivers the spermatophore into the female mantle

A

hectocotylus

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3
Q

Aquatic invertebrates

hectocotylus delivers the spermatophore into the female

A

mantle

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4
Q

Aquatic vertebrates

“Fish” and Amphibians

A
  • predominantly external fertilization
    • eg most teleosts and amphibia
  • elasmobranchs - claspers deliver spermatophore into female cloaca
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5
Q

Aquatic vertebrates

… deliver spermatophore into female cloaca

A

claspers

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6
Q

Aquatic vertebrates

claspers deliver spermatophore into female

A

cloaca

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7
Q

Terrestrial animals

A

invertebrates practice

  • indirect internal fertilizatoin
    • eg arachnids
  • or direct internal fertilizatoin
    • eg insects
  • vertebrates always have direct internal fertiliation - insemination​​
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8
Q

Terrestrial animals

Invertebrates practice

A

indirect internal fertilization

  • eg arachnids

direct internal fertilizatoin

  • eg insects
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9
Q

Terrestrial animals

vertebrates always have

A

direct internal fertilization

(insemination)

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10
Q

Scorpions

A
  • indirect internal fertilization
  • male paraxial organs deliver the spermatophore
    • packages 2 halves of spermatophore
  • “promenade a deux”
  • female cloaca dragged over spermatophore
    • deposit sperm on ground and drag female over it
    • she resists as he pulls her → rocking motion takes up sperm
    • must be quick so the sperm doesn’t dry out
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11
Q

Spiders

A
  • indirect internal fertilization
  • spermatophore depositied and then sperm picked up by pedipalp
    • ​pedipalp produced at back (?)
  • pedipalp delivers spermatophore into female cloaca
  • copulatory plug
    • ​pedipalp breaks off
    • only 2 so males mate twice then die
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12
Q

Insects

A
  • direct internal fertilization
  • several specialized structures for insemination
    • aedeagus
    • juxta
  • “traumatic insemination” in Cimicidae
    • male punctures female abdomen and sperm goes in “anywhere” and into paragenital system
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13
Q

Terrestrial vertebrates

reptiles and mammals

A

direct fertilization via a penis

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14
Q

Terrestrial vertebrates

birds

A
  • 97% of birds (and tuatara) lack a penis
  • direct fertilization via a “cloacal kiss”
    • ​no intromissive organ
  • tuatara really old/primitive so penises are a relatively new feature
  • ostriched DO have penises - “runs” on lymphatics
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15
Q

Mammalian testis size

A
  • highly variable
  • allometric scaling - testis as a proportoin of body mass decreases with increasing size
    • eg body mass doubles but structures don’t exactly double
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16
Q

Animals bigger

→

A

testis bigger

(but not necessarily proportional)

(testis mass vs body mass)

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17
Q

Testis mass vs body mass (%)

A
  • average size of testis is ~1% body mass unless very small organism (>1%)
  • animals with biggest testes proportionally - rodents
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18
Q

Rodents testes size

A
  • most variation in very small
  • proportionally largest testes in smallest animals
  • biggest proportionally = gerbil
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19
Q

Internal testes

A
  • TESTICONDIDS
  • testes internal - don’t have to be scrotal
  • for purposes of streamlining/aerodynamics
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20
Q

Where would you find mamalian testes?

A
  • originate in abdomen
  • anterio-rostral migration (in scrotum)
  • contraction of gubernuculum
    • caused by androgens
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21
Q

Why do testes desccend in scrotal mammals?

A
  • **NOT **scrotal because of temperature
    • can cool testes without requiring testicular descent
  • ?galloping (in the way of gait)
  • ?sexual display
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22
Q

Size of testes based on

A

whether or not there’s sperm competition

(no competition → smaller testes)

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23
Q

Testis structure

A
  • comprised primarily of seminiferous tubules
    • one tubule goe back and forth
  • seminiferous tubules contain Sertoli cells and sperm
    • ​Sertoli cells inside tubules look after maturing sperm
  • packed in between the seminiferous tubules are interstitial Leydig cells
    • Leydig cells outside tubules, make testosterone
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24
Q

Testis comprised primarily of

A

seminiferous tubules

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25
Q

Seminiferous tubules contain

A

Sertoli cells and maturing sperm

(Sertoli cells inside tubules looking after maturing sperm)

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26
Q

Packed in between the seminiferous tubules are interstitial

A

Leydig cells

(outside tubules, make testosterone)

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27
Q

Function of Sertoli cells

A

to mature the sperm

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28
Q

Sperm are germ cells but…

A

they are looked after by Sertoli cells which are somatic cells

  • Sertoli cells are diplod
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29
Q

2 major cell types

A

Sertoli cells

  • look after sperm
  • inside the tubule

Leydig cells

  • make testosterone
  • outside the tubule
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30
Q

The tubule collects into the

A

epididymis

a single duct flows out for ejaculation

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31
Q
A
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32
Q

Direction of cell movement inside the tubule

A

basal → adluminal

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33
Q

2 main hormones

A

leuteinizing hormone (LH)

  • Leydig cells respond to leuteinizing hormone

follicle-stimulating hormone (FSH)

  • Sertoli cells respond to follicle-stimulating hormone
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34
Q

Leydig cells respond to

A

luteinizing hormone

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35
Q

Sertoli cells respond to

A

follicle-stimulating hormone

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36
Q

Sperm cells on the basal side of the tubule close to the junction between Leydig cells and the Sertoli cells have

A

spermatogonia

  • diploid
  • dividie by mitosis
  • mitosis turns one spermatogonium into multiple spermatogonia
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37
Q

Spermatogonia

A
  • diploid
  • dividie by mitosis
  • mitosis turns one spermatogonium into multiple spermatogonia
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38
Q

When spermatogonia enter meiosis, they become

A

spermatocytes

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39
Q

Spermatocytes become

A

spermatids

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40
Q

Spermatids will ultimately mature to become

A

spermatozoa

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41
Q

Sperm stages

A

spermatogonia

spermatocytes

spermatids

spermatozoa

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42
Q

Spermatogonia → spermatozoa

happens in

A

a single sertoli cell

  • these cells all require very different microenvironments
    • has an environment onthe basal side perfect for spermatogonia
    • an environment in the middle for spermatocytes
    • an environment at the apex for spermatids and spermatozoa
43
Q

Endocrine products

A
  • Leydig cells make testosterone (steroid) in response to LH
  • Sertoli cells also produce some hormones
    • inhibin (not a steroid) but is a growth factor
    • androgen-binding protein (ABP) - with the ability to carry testosterone
44
Q

Leydig cells make

A

testosterone

45
Q

Leydig cells make testosterone in response to

A

LH

46
Q

Sertoli cells produce

A
  • inhibin (not a steroid but a growth factor)
  • androgen-binding protein (ABP) with the ability to carry testosterone
47
Q

Inhibin is a

A

growth factor

48
Q

Androgen-binding proten (ABP) has the ability to

A

carry testosterone

49
Q

Paracrine products

A

products that act on each other

(act on neighboring cells rather than elsewhere in the body)

50
Q

We make LH and FSH in

A

the pituitary gland

51
Q

LH and FSH are

A

heterodimeric glycoproteins

  • have 2 subunits which are dissimilar
  • heavily glycosylated that gives them the weight of 25-30kDa
52
Q

Both LH and FSH have the same

A

α-subunit

53
Q

α-subunit of LH and FSH

A

gonadotrophin α-subnit (GSU)

  • paired with LHβ → luteinizing hormone
    • LH will stimulate Leydig cells to synthesize testosterone
  • paired with FSHβ → FSH
    • FSH will stimulate Sertoli cells to make mature sperm
54
Q

Sperm have no receptors for

A

gonadotrophins

  • if the endocrine system wants to stimulate sperm division, it can’t do that on the sperm
  • must stimulate Sertoli cells
  • the Sertoli cells have to tell the sperm what to do
55
Q

NO … on sperm

A

FSH or LH receptors

(no FSH or LH receptors on sperm)

56
Q

FSH receptors are on

A

Sertoli cells

57
Q

FSH also stimulates Sertoli cells to make

A

the growth factor inhibin

58
Q

In the brain you have the

A

gonadotrophin releasing hormone (GnRH)

59
Q

GnRH

A
  • the hormone in the hypothalamus that drives reproduction
  • important in puberty
  • stimulates the anterior pituitary glad to produce LH and FSH gonadotrophins
60
Q

GnRH stimulates the anterior pituitary gland to produce

A

LH and FSH gonadotrophins

61
Q

LH stimulates the testis to make

A

testosterone

62
Q

FSH stimulates Sertoli cells to make

A

inhibin

and closely related

activin

63
Q

Inhibin and activin

A

together exert negative feedback

64
Q

Testosterone exerts negative feedback on

A

both LH and FSH

65
Q

Inhibin exerts negative feedback on

A

FSH

(inhibin produced in response to FSH and suppresses FSH)

66
Q

Negative feedback…

A

keeps the testes small

  • if the negative feedback is lost in a species that produces a lot of LH and FSH, the testes will grow larger and larger

→ testicular hypoplasia

67
Q

In animals with sperm competition we see

A

a really strong endocrine drive and large testes

  • want to produce lots of sperm
  • semen from elsewhere, sperm comes from testis
68
Q

Testosterone transport

A
  • testosterone has limited solubility in blood
  • can associate with serum albumin
    • 54% in humans
  • associates with hydrophobic core of hepatic sex hormone binding globulin (SHBG)
    • 44% in humans
69
Q

Meiosis in the testis

A

1 spermatogonium (2n)

→

2 primary spermatocytes (2n)

→

4 secondary spermatocytes (n)

70
Q

Spermatogenesis

A

spermatogonium A

spermatogonium B

primary spermatocyte (leptoptene)
primary spermatocyte (zygotene)

primary spermatocyte (pachytene)

primary spermatocyte (diplotene)

primary spermatocyte (diakinesis)

secodary spermatocyte

round spermatid

71
Q

Spermiogenesis

A

round spermatid

elongate spermatid

spermatozoon

72
Q

Endocrine control of spermatogenesis

Complete spermatogenesis + spermiogenesis dependeng on

A

FSH + testosterone/DTH

73
Q

Endocrine control of spermatogenesis

FSH more important in

A

early stages of meiosis

(via Sertoli cells)

74
Q

Endocrine control of spermatogenesis

Androgens more important in

A

latter stages (RS) plus spermiogenesis

75
Q

Male pelvic anatomy

A
76
Q

Male pelvic anatomy

(bullets)

A
  • testis are a collection of supercoiled tubules
  • also supercoiling in the epididymis
    • looks like a simple tube but isn’t
    • that’s a covering under which we see convoluted tubules
  • vas deferens is a simple tube that runs out of the epididymis to the penal urethra
    • on its way it passes seminal vesicles
77
Q

Epididymis is composed of

A

supercoiled tubules until it runs into the vas deferens

78
Q

Vas deferens

A

a simple tube that runs out of the epididymis to the penal urethra, passing seminal vesicles

79
Q

Epididymis

A

2 and 3. caput epididymis (head)

  1. corpus epididymis (body)
  2. cauda epididymis (tail)
  • called body and tail because of way sperm moves through them
  • in humans oriented to earth this way
  • in many eutherians not oriented this way
80
Q

Spermiogenesis finishes off in the

A

epididymis

81
Q

Normal spermatozoan

A
82
Q

Spermatozoan

A
  • when mature has acrosome
    • membrane-bound enzymes
  • spiral micochondrium
    • wraps around flagellum
    • very plastic
  • tail
    • flagellum that makes sperm depending where the sperm is
83
Q

Acrosome

A
  • mature spermatozoan
  • enzymes that sit over the nucleus
84
Q

Spiral mitochondrion

A
  • wraps around the flagellum
  • very plastic
  • dividing and fushing, not as mean as there appears
85
Q

Tail

A
  • flagellum that makes sperm swim depending where sperm is
86
Q

When sperm leave the testes they are

A

immotile

87
Q

Epididymal sperm maturation

A

testicular spermatozoa still need to acquire

  • motility
  • ability to fertilizie oocyte

both acquired as sperm pass through caput and cauda epididymis

88
Q

Testicular spermatozoa still need to acquire

A
  • mobility
  • ability to fertilize oocyte

both acquired as sperm pass through the caput and cauda epididymes

89
Q

Don’t want sperm to be hyperactive in the

A

epididymis

90
Q

Sperm are stored in the

A

cauda epididymis

(before going to the vas deferens)

91
Q

Sperm acquire …. to prevent hyperactivation

A

decapacitation factors

(keeps them calm)

looks like just extra cholesterol

92
Q

Decapacitation factors need to be removed

A

in female tract prior to fertilization

93
Q

Decapacitation factors need to be remoed in the female tract prior to fertilization

A
  • alkaline due to pH
  • why epididymis can’t fertilize
  • may involve progesterone to remove cholesterol
94
Q

Secretions of the epididymis also include

A
  • inositol
    • man, stallion, ram
    • sugar, carb
    • preserves seminal osmolarity
  • glycerophosphorylcholine
    • substrate for phospholipid metabolism
95
Q

Species variations in accessory sex glands

A
  • dogs don’t have bulbo-urethral glands
  • humans have large prostrates as do dogs
  • bull has sall prostrate, but huge seminal vesicles
  • boar - culper gland is enormous but the prostrate is reduced
  • because of different strategies to maximize fertilization different animals have evolved different structures
96
Q

The prostrate gland

A

secretions of the prostrate gland include

  • citric acid
    • chelates Ca2+ to prevent semen coagulation
    • the anticoagulant property of citric acid will be neutralized when entering the female tract
    • the semen will coagulate and set (to form mating plug)
  • acid phosphatase
    • hydrolyses choline from glycerophosphorylcholine
    • added in the epididymis
  • prostaglandins cause female tract to convulse
97
Q

Citric acid

A
  • from prostrate gland
  • chelates Ca2+ to prevent semen coagulation
  • the anticoagulant property of citric acid will be neutralized when entering the female tract
  • the semen will coagulate and set (to form mating plug)
98
Q

Acid phosphatase

A
  • produced by prostate gland
  • hydrolyses choline from glycerophosphorylcholine
  • added in the epididymis
99
Q

Prostaglandins

A
  • produced by prostate gland
  • prostaglandins cause female tract to convulse
100
Q

Secretions of the seminal vesicles

A

fructose

  • anaerobic fructolysis in sperm
  • for sperm propulsion

inositol

  • bull and boar (convergent evolution)
  • preserves seminal osmolarity

citric acid

  • stallion, ram, boar, bull
  • to stop semen from coagulating in the semen tract
101
Q

Fructose

A
  • secretion of the seminal vesicles
  • anaerobic fructolysis in sper
  • for sperm propulsion
102
Q

Inositol

A
  • secretion of seminal vesicles
  • bull and boar (convergent evolution)
  • preserves seminal osmolarity
103
Q

Citric acid

A
  • stallion, ram, boar, bull
  • to stop semen from coagulating in the semen tract until in female
104
Q

The bulbo-urethral (cowper’s) gland

A
  • produces clear, viscous “pre-ejaculate” on sexual arousal
    • lubricates penis
  • alkaline secretion
    • neutrlizes acidic urine in the penile urethera
    • if too acidic then the sperm will die
    • biggest acid must worry about is uric acid from urine in the urethra
    • in mammals sperm move down the same tract as urine
  • causes semen coagulation
    • contributes to “gel fraction” in boar
    • bull produces 1.5 liters of ejaculate - a large fraction of which is gel fraction which stops the ejaculate falling out
    • this is made in the bulbo-urethral gland - hence why the bulbo-urethral gland is huge in boars

Reproductive and Developmental Biology (8 decks)

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