Spermatogenesis

Question 1

Where in the testes does spermatogenesis occur?

Answer 1

Seminiferous tubules

Question 2

What cell type lines the seminiferous tubules?

Answer 2

Sertoli cells

Question 3

What cell type is homologous to Sertoli cells in females?

Answer 3

Granulosa cells

Question 4

What cell type is homologous to Leydig cells in females?

Answer 4

Theca cells

Question 5

Where are Leydig cells found in the testes?

Answer 5

Interstitium

Question 6

What proportion of the testes volume do seminiferous tubules make up?

Answer 6

95%

Question 7

What is the function of Leydig cells?

Answer 7

Testosterone synthesis

Question 8

What are the functions of Sertoli cells?

Answer 8

1. 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

Question 9

What are the phases of spermatogenesis?

Answer 9

1. Mitosis; 2. Meiosis; 3. Cytodifferentiation

Question 10

When does mitosis start in males?

Answer 10

At the start of puberty

Question 11

In what compartment of the seminiferous tubules does mitosis occur?

Answer 11

Basal compartment

Question 12

What occurs during mitosis in males

Answer 12

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

Question 13

What factors promote round of mitosis in SSCs?

Answer 13

GDNF (secreted by Sertoli cells), its action potentiated by bFGF and CSF-1

Question 14

At what point do cells move into the adluminal compartment from the basal compartment?

Answer 14

Each pre-leptotene (pre-meiosis) resting primary spermatocyte duplicates its DNA - it is then that it moves into the adluminal compartment

Question 15

At what point does meiosis begin?

Answer 15

As a resting primary spermatocyte

Question 16

What are the stage of mitosis?

Answer 16

G1 (cellular content, excluding chromosomes duplicated), S (chromosome duplication); G2 (error checking); mitosis; cytokinesis

Question 17

What are the stages of meiosis

Answer 17

Interphase — Prophase I (leptotene, zygotene, pachytene, diplotene, diakinesis) — Metaphase I — Anaphase I — Telophase I — Prophase II — Metaphase II — Anaphase II — Telophase II — Cytokinesis

Question 18

What happens during leptotene (PI)?

Answer 18

(Prior = duplication of chromosomes) Chromatin condenses

Question 19

What happens during zygotene (PI)?

Answer 19

Homologous chromosomes come together in pairs, attached to the nuclear mebrane at their extremities

Question 20

What happens during pachytene (PI)?

Answer 20

Chromosome pairs (bivalents) shorten + condense. Crossing over takes place

Question 21

What happens during diplotene (PI)?

Answer 21

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)

Question 22

What happens during diakinesis?

Answer 22

Nuclei disappear, nuclear membrane disintegrates, meiotic spindle begins to from

Question 23

What happens during MI?

Answer 23

Paired homologous chromosomes (bivalents) align on the equatorial plane, bisecting the spindle

Question 24

What happens during AI?

Answer 24

Homologous chromosomes pulled to opposite poles of the cell

Question 25

What happens during TI?

Answer 25

New nuclear membrane forms and chromosomes uncoil back into chromatin. Cytokinesis occurs and two secondary spermatocytes are formed. Another round of meiosis occurs (meiosis II) and in this, from each secondary spermatocyte, 2 haploid spermatozoa will be formed

Question 26

What are the changes that take place during maturation?

Answer 26

1. Acquisition of motility; 2. Chromatin modification; 3. Acrosome size alteration; 4. Migration of the cytoplasmic droplet from the sperm's neck, to near the annulus; 5. Acquisitor of the ability to recognise, bind and fuse with eggs; 6. Modification to the surface plasma membrane

Question 27

What is spermiation?

Answer 27

When spermatozoa are release into the lumen of the seminiferous tubules and washed along by testicular fluid formed from the Sertoli cells, following cytoplasmic bridge rupture