Lecture 6: Spermatogenesis and male tract 1 Flashcards
What are the origins of the these early development Testis Cell Types.
- Spermatogonia
- Sertoli Cells
- Leydig Cells
- Myeloid Cells
- Spermatogonia from Germ cells
- Sertoli Cells from epithelial cells
- Leydig Cells from Interstitual tissue between cords
- Myeloid Cells from interstitual tissue between cords wrap around seminiferous tubules; are contractile
When do the testes descend? What controls this?
- 7-8 months
- Within abdominal cavity descent is under the influence of AMH
- Once in the inguinal ring under the influence of testosterone
What is cryptorchidsm?
- Failure of testes to descend, 3% incidence
- 2 forms:
- Incomplete (90%)
- Maldescent (goes wrong way e.g into abdomen)
- If not treated will –> infertility
How do testosterone levels change in the early stages of development?
- Peak at 13-15 weeks - brain programming
- Peak at 2-3 months in neonate for gonadal programming
- Drops until puberty when there is a huge increase
What changes occur in puberty?
- Proliferation of spermatogonia
- Cords develop a lumen to become seminiferous tubules
- begining of sperm production
Spermatogonia?
- Sit on basement membrane of seminiferous tubules
- Full set of chromosomes
Sertoli cells
- Sit on BM but extend –> lumen of seminiferous tubules
- Germ cells sit enveloped in sertoli cells
- have junctional complexes made from tight junctions to seperate spermatogonia and spermatocytes
Leydig cells
- Pale cytoplasm, rounded cells in the interstitual space. Produce Androgens ‘testosterone’
What are Myofibroblasts?
Little cells that sit on the outside of the Seminiferous tubule, can squeeze the tubule to move the fluid down the tubule lumen!
Look and describe pg 29 spermatogenesis diagram
The spermatatogonia divide,
- One half stays at the basement membrane, as a back up layer
- The other half just keeps dividing and moves through the Junctional Complex to become a 1º spermatocyte.
- This is now a slow process of Meiosis; takes around 3 weeks (which is why you can usually see lots of them)
- First division produces 2º spermatocyte, which are only around for a short time (chromosome number has reduced ‘haploid’)
- Once undergone 2nd meiotic division, it is now a spermatid. Th.ese are little Round cells → elongated with dark nuclei
What are the 3 main stages of Spermatogenesis?
- Spermatocytogenesis: mitosis
- Meiosis: reduced # chromosome, 2 divisions
First division: halves number of chromosomes
Second Division: double number of cells again to 4 - Spermiogenesis
See pg 28 of module book!
The Golgi Phase of Spermatid Development
Golgi Phase: Rounded cells, opposite to a forming flagellum there is a Golgi; (where proteins get added to carbs produced in the ER) and vesicles of protein+carbs fuse and become large, membrane bound Proacrosomal Granules (which will form the acrosome)
The Cap Phase of Spermatid Development
Cap Phase: granules keep fusing, and eventual form a cap of acrosomal cap, and the whole structure is called an acrosome that sits atop the nucelus like a beanie.
Describe the 4 phases of Spermatid Development
- Golgi Phase
- Cap Phase
- Acrosomal Phase
- Maturation Phase
Periodic Release of Spermatozoa into the lumen comes every ____ days in ___________.
Why does this occur?
Periodic Release of Spermatozoa into the lumen comes every 16 days in successive waves.
The interval at any point in the lumen is 16 days.
This is because sperm are all linked from the initial spermatogonia to the spermatozoa by cytoplasmic bridges, that are all marching together in unision to the lumen.
Sperm is produced 300-600/second
