Spermatogenesis + testicular function

what is spermatogenesis?

• formation of spermatozoa

what are the 3 stages of spermatogenesis

1. proliferation

2. meiosis

3. differentiation

What are the products of:

1. proliferation

2. meiosis

3. differentiation

in spermatogenesis?

1. spermatogonia

2. primary + secondary spermatocytes

3. spermatids/spermatozoa

what is the time frame for spermatogenesis?

• 5-9 weeks species dependend

what cells do spermatogonia develop from?

• primordial germ cells

what two cells can primordial germ cells become?

• A1 or B

• copy of itself or spermatogonia

which cell type, A1 or B, becomes spermatozoa?

• type B

how does cell type B, spermatogonia, become spermatozoa

1. mitosis into primary spermatocyte

2. meiosis I → secondary spermatocyte

3. meiosis 2 → spermatid

4. differentiation → spermatozoa

What do each fo the black lines represent?

• different stage of spermatogenesis → closer to basal compartment = primordial germ cells, sertoli cells and spermatogonia

• towards the lumen = progression to spermatozoa

how are sertoli cells involved in protecting spermatogenesis?

• the spermatogonia cells and future divisions reside within the cytoplasm of the sertoli cells, connected by intracellular birdges

• as the cells develop, the sertoli cell unravels the tight junction, enabling the cell to move closer to the lumen as it develops.

what is spermiogenesis?

• final stage of spermatogenesis

what are the 5 keys steps of spermiogenesis

1. nuclear condensation

2. acrosome formation

3. flagellum development

4. cytoplasmic reduction

5. mitochondrial rearrangement

what is the end point result of spermeiogenesis

• non-motile spermatozoa

what is spermiation

• the release of the spermatozoa from the sertoli cells

what are 4 key steps in spermiation

1. detachment from sertoli cells

2. breakdown of junctions

3. cytoplasm removal

4. epididymis transport via fluid flow

how many cycle of the seminiferous epithelium is equal to the duration of spermatogenesis?

• roughly 4.5

if we were told:

• the seminiferous epithelium cycle of a ram is 10.6 days, what is the duration of spermatogenesis

what would you do?

• multiply 10.6 by 4.5 = 47.7

• the actual duration for a ram is 48 days - so almost accurate

what do we mean by the cycle of the seminiferous epithelium?

• reoccurrence of the same stage in a specific area of the seminiferous tubule

  • the time taken to return to the original stage

how many stages int he cycle of the seminiferous epithelium are there?

• 8

what is stage 1 of the cycle of the seminiferous epithelium

• spermatogonia start mitotic division

what is stage 2 of the cycle of the seminiferous epithelium

• primary spermatocytes undergo DNA replication

what is stage 3 of the cycle of the seminiferous epithelium

• primary spermatocytes prepare for meiosis I

what is stage 4 of the cycle of the seminiferous epithelium

• secondary spermatocytes are formed

what is stage 5 of the cycle of the seminiferous epithelium

• secondary spermatocytes enter meiosis II = spermatids

what is stage 6 of the cycle of the seminiferous epithelium

• round spermatids start elongation

what is stage 7 of the cycle of the seminiferous epithelium

• spermatids undergo nuclear condensation/acrosome formation

what is stage 8 of the cycle of the seminiferous epithelium

• mature spermatids undergo spermiation, move into lumen

what is meant by a stage of the cycle of the seminiferous epithelium

specific cellular associations at any cross section at any moment in time

what is meant by stage duration of the cycle of the seminiferous epithelium

• time required to progress from 1 stage to the next

what is meant by cycle of the cycle of the seminiferous epithelium

• progression through sequence of all stages

what is meant by cycle duration of the cycle of the seminiferous epithelium

• time required to complete any 1 cycle

what is meant by a spermatic wave in the cycle of the seminiferous epithelium

• differences in any given instance along the seminiferous tubule

what are the 4 phases of spermiogenesis

1. golig phase

2. cap phase

3. acrosomal phase

4. maturation phase

what happens in the golgi phase of spermiogenesis

• vesicles of golgi fuse to form acrosomic vesicle

• centrioles move to base of nucleus

• proximal centriole anchors tail to nucleus

• distal centriole forms central flagellum

what is the cap phase of spermiogenesis?

• acrosome forms a cap

• golgi apparatus migrates + disappears

• primitive flagellum forms

what happens in the acrosomal phase of spermiogenesis?

• acrosome spreads

• nucleus elongates

• manchette tubules form sperm head shape

• neck forms

• annulus forms

what is the function of the annulus during the acrosomal phase of spermiogenesis

• separates midpiece from principal piece of tail

• structural integrity

what is the maturation phase of spermiogenesis

• manchette forsm post-nuclear cap

• mitochondria form spiral assembly - mid-piece

what are 2 key points about the head of the sperm?

• nucleus + acrosome + post-nuclear cap

• acrosome contains hydrolytic enzymes needed for penetration of zona pellucida

what are 2 key features of the mid-piece of a spermatozoa

• capitulum - anchors tail to head

• axoneme - arranges microtubules for movement

what are the 3 parts of the tail of a spermatozoa?

• principal piece

• middle piece

• terminal piece

what axis is essential for spermatogenesis?

• HPG axis

function of LH in spermiogenesis?

• binds to receptors on leydig cells → testosterone secreted

what is the function of FSH in spermiogenesis?

• binds to receptors on sertoli cells → testosterone converted to oestradiol

• inhibin produced

describe the pattern of testosterone secretion

• pulsatile

describe the testosterone negative feedback loop

• testosterone in blood

• redcued GnRH at hypothalamus

• lowers LH secretion

• less Leydic cell stimulation

state 3 hormones, not testosterone, that exhibit negative feedback on the testosterone cycle and where they act

1. dihydrotestosterone - androgen sensitive tissue

2. oestrogen - hypothalamic inhibition + anterior pituitary

3. inhibin - FSH

what is daily sperm production

• total number of spermatozoa produced by the testes per day

what is daily sperm output

• number of spermatozoa ejaculated over a period of time

the sample requires diluting 1 in 10 in normal saline for its motility analysis. How would you prepare 1ml of this dilution

• 100 microlitres of semen + 0.9ml saline

sample requires diluting 1 in 80 in normal saline for its count analysis, how would you prepare 4ml of this dilution

• 4000microlitres divided by 80

• 50microlitres semen + 3.95 ml saline