Spermatogenesis Flashcards
Where in the testes does spermatogenesis occur?
Seminiferous tubules
What cell type lines the seminiferous tubules?
Sertoli cells
What cell type is homologous to Sertoli cells in females?
Granulosa cells
What cell type is homologous to Leydig cells in females?
Theca cells
Where are Leydig cells found in the testes?
Interstitium
What proportion of the testes volume do seminiferous tubules make up?
95%
What is the function of Leydig cells?
Testosterone synthesis
What are the functions of Sertoli cells?
- Support/nutrition of developing germ cells; 2. Compartmentalise the seminiferous tubules; 3. Controlled release of spermatids into the tubular lumen; 4. Secretion into the tubules; 5. Phagocytosis
What are the phases of spermatogenesis?
- Mitosis; 2. Meiosis; 3. Cytodifferentiation
When does mitosis start in males?
At the start of puberty
In what compartment of the seminiferous tubules does mitosis occur?
Basal compartment
What occurs during mitosis in males
Primordial germ cells (enter mitosis) —- become spermatogonial stem cells (SSCs) —- type A spermatogonia emerge upon SSC mitosis — each type A = mitosis to a clone of 16. Type A transform morphologically to become A1 spermatogonia — A2 — A3 —- A4 — intermediate spermatogonium — type B spermatogonia — resting primary spermatocyte
What factors promote round of mitosis in SSCs?
GDNF (secreted by Sertoli cells), its action potentiated by bFGF and CSF-1
At what point do cells move into the adluminal compartment from the basal compartment?
Each pre-leptotene (pre-meiosis) resting primary spermatocyte duplicates its DNA - it is then that it moves into the adluminal compartment
At what point does meiosis begin?
As a resting primary spermatocyte
What are the stage of mitosis?
G1 (cellular content, excluding chromosomes duplicated), S (chromosome duplication); G2 (error checking); mitosis; cytokinesis
What are the stages of meiosis
Interphase — Prophase I (leptotene, zygotene, pachytene, diplotene, diakinesis) — Metaphase I — Anaphase I — Telophase I — Prophase II — Metaphase II — Anaphase II — Telophase II — Cytokinesis
What happens during leptotene (PI)?
(Prior = duplication of chromosomes) Chromatin condenses
What happens during zygotene (PI)?
Homologous chromosomes come together in pairs, attached to the nuclear mebrane at their extremities
What happens during pachytene (PI)?
Chromosome pairs (bivalents) shorten + condense. Crossing over takes place
What happens during diplotene (PI)?
Chromosomes start to spirit and decidedness a little to allow fro DNA transcription (but bivalents still remain closely bound at the chiasma and remain so until the chiasmata is severed at the transition into AI)
What happens during diakinesis?
Nuclei disappear, nuclear membrane disintegrates, meiotic spindle begins to from
What happens during MI?
Paired homologous chromosomes (bivalents) align on the equatorial plane, bisecting the spindle
What happens during AI?
Homologous chromosomes pulled to opposite poles of the cell