1 Animal Science 434 Lecture 12: Spermatogenesis Production of Fertile Sperm • hormonal regulation of the testis • mitotic division of spermatogonia • meiotic divisions of spermatocytes • morphologic transformation of spermatids into spermatozoa Hormonal Regulation of the Testis LH LH LH LH GnRH GnRH GnRH GnRH FSH FSH FSH FSH Time of Day (24 hr) Pulses are important ! Hypothalamus GnRH E 2 Inhibin ABP Sertoli Cells Leydig Cells Seminiferous Tubule Ant. Pituitary FSH on Sertoli Cells • estradiol • inhibin • ABP • tight junctions FSH LH Negative Feedback of Estradiol and Inhibin Germ Cells T ABP + T To Epid. Negative Feedback of Androgens TJ
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Animal Science 434 mitotic division of spermatogonia Lecture 12 ... · 1 Animal Science 434 Lecture 12: Spermatogenesis Production of Fertile Sperm •hormonal regulation of the testis
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Animal Science 434
Lecture 12: Spermatogenesis
Production of Fertile Sperm
• hormonal regulation of the testis
• mitotic division of spermatogonia
• meiotic divisions of spermatocytes
• morphologic transformation ofspermatids into spermatozoa
Hormonal Regulationof the Testis
LHLH LH LH
GnRHGnRH
GnRH GnRH
FSH FSH FSH FSH
Time of Day (24 hr)
Pulses are important !
HypothalamusGnRH
E2
Inhibin
ABP
SertoliCells
LeydigCells
SeminiferousTubule
Ant.Pituitary
FSH on Sertoli Cells• estradiol• inhibin• ABP• tight junctions
FSHLH
Negative Feedback ofEstradiol and Inhibin
GermCells
T
ABP+T
ToEpid.Negative
Feedback ofAndrogens
TJ
2
Spermatogenesis
Myoid Cells
Sertoli Cell
Sertoli Cell
Every 13.5 Daysa new group of cellsinitiate the cycle
Every 13.5 Days spermare released from this
point
Spermatozoa
SecondarySpermatocyte
PrimarySpermatocyte
RoundSpermatid
Spermatogonia
Spermatogonia(A, intermediate, B)
Primary Spermatocyte
SecondarySpermatocyte
Round Spermatid
Spermatozoa
A
A A
I IBB
P PS S
RS RS
SP SP
Spermato-cytogenesis
Spermio-genesis
Mitosis
Meiosis
Rete Testis
Spermiation
Typical Sequence of Spermatogenesis
A
A A
I IBB
P PS S
RS RS
SP SP
1
2
48
1632
64
Potential Sperm Produced
Many Sperm are Produced
3
Mitotic Divisions• species dependent
– between 2 and 6 divisions (4 to 64 potentialdaughter cells produced)
• classifications vary among species andinvestigators– A1, A2, A3, A4, B 1, B2, P– Ad, Ap, B, P– As, A0, A1, A2, I, B, P
• cytoplasmic bridges form betweendaughter cells
Degenerating Spermatogonia (Apoptosis, as high as 75%)
• Testis Size• Efficiency of spermatogenesis–mitotic division– degeneration of germ cells
• Length of spermatogenesis
Apoptosis of Germ Cells
• Season• Disease• Trauma or heat• Hormone levels• Normal part of spermatogenesis
Over Population of Spermatogonia
SGSGSGSGSGSG SG SG SG
Basement Membrane
Sertoli Sertoli
Tight Junction
PS
PS
SGSG SG
Basement Membrane
SertoliSertoli
AP APAP AP
Normal Apoptosis Inhibited
SGSGSGSGSGSG SG SG SG
Basement Membrane
Sertoli SertoliSG
SG
Animation of Spermatogenesis
View the Animation of SpermatogenesisUsing the Link at the Bottom of the ScreenView the Animation of Spermatogenesis
Using the Link at the Bottom of the ScreenThe objective is to see how the process of spermatogenesistakes place over time and involves both stages and cycles.
• In the animation, the timing of events is correct but wehave taken liberties in moving groups of cells from side toside to make room for development of other cells.
• The animation begins with primordial germ cell migrationinto the primary sex chord and replication of gonocytes toform stem cell A-Type spermatogonia.
The objective is to see how the process of spermatogenesistakes place over time and involves both stages and cycles.
• In the animation, the timing of events is correct but wehave taken liberties in moving groups of cells from side toside to make room for development of other cells.
• The animation begins with primordial germ cell migrationinto the primary sex chord and replication of gonocytes toform stem cell A-Type spermatogonia.