Male Repro I

Question 1

Sperm journey

Answer 1

1. High speed manufacturing in testis
2. Fluid absorption and finishing of spermatozoa in the head and body of the epididymis
3. Warehouse and shipping. Smooth muscle contractions. Occurs in tail of epididymis
4. Provide energy and coating removal for transport in the accessory sex glands
5. Delivery system in the penis

Question 2

Thermoregulation of testis

Answer 2

Testis tissue is 4-6 degrees C cooler than body which is needed for normal sperm production

Question 3

What plays a role in testis cooling?

Answer 3

-cremaster muscle
-scrotal skin
-tunica dartos
-vascular countercurrent

Question 4

Vascular counter-current

Answer 4

Testes had papiniform plexus (venous network wrapped around testicular artery)

-Effective in heat exchange, pulse pressure reduction, and transfer of testosterone

Question 5

Pulse pressure in spermatic cord

Answer 5

There is a pulse pressure difference in the testicular artery when above and below the pampiniform plexus.
>High above, Low below

**Reduction significance is unclear. Might be linked to the testicular artery being more elastic

Question 6

Scrotal sweating and thermal polypnea

Answer 6

-Scrotal skin has abundant sweat glands innervated by sympathetic nerves AND thermosensitive nerves that control sweating and rate of respiration

Question 7

Temperature and sperm mortality

Answer 7

Short periods of high temp is mostly tolerated but more than 8hrs can reduce sperm mortality and cause DNA damage

Question 8

Scrotum temperature and resp rate

Answer 8

When there is an increase in scrotal temperature, respiratory rate increases. As temperature drops, respiratory rate decreases

Question 9

Rete tubules of testes

Answer 9

Lobules within the testes have seminiferous tubules that exit into mediastinum/rete tubules

Central rete testes in pigs and bulls

Superficial rete testes in horses and humans

Question 10

Leydig (interstitial endocrine) cells function and appearance

Answer 10

Function: produce testicular androgens (and lots of estrogen in pig and horse)

Appearance: large polymorphous acidophilic cells with round nucleus. Steroid producing

Question 11

Leydig volume in rams, bulls and pigs

Answer 11

Rams: 1%

Bulls: 5%

Pigs: 20-30%

Question 12

Leydig cell populations

Answer 12

1. Fetal leydig cells- from sex determination until shortly after birth
2. Infantile/early postnatal leydig cells- only in some species (primates, pigs, ox); very short lived
3. Adult leydig cells- from puberty through adult life

Question 13

Seminiferous cord/tubules

Answer 13

-convoluted double ended loops (2m in mice, 5km in bulls)
-have lamina propria (contains basal lamina and peritubular cells), sertoli cells, spermatogenic cells

Question 14

Seminiferous cords

Answer 14

-immature
-lack lumen
-70-90 micrometers in diameter
-sertoli and gonocytes

Question 15

Seminiferous tubules

Answer 15

-developed
-have a lumen
-150-300 micrometers
-sertoli and multiple generation of germ cells

Question 16

Peritubular myoid cells

Answer 16

1-5 layers of contractile cells (contain actin and cytoskeleton proteins) surrounding the basal lamina

Contractile action allows for the propulsion of sperm and testicular fluid along the lumen of seminiferous tubules toward rete testes

Question 17

What do the peritubular myoid cells resemble?

Answer 17

Myofibroblasts (eg bull) OR smooth muscle fibers (eg boar)

Question 18

Sertoli (sustentacular) cells appearance

Answer 18

-oval nucleus with nucleolus near base
- large elongated cells with irregular outlines touching basal membrane, and laterally and apically fill space among germ cells
-evenly spaced in tubule

Question 19

Sertoli cells mitotic ability

Answer 19

-Adult cells will lose mitotic capability compared with fetal/early postnatal

Question 20

Sertoli cell functions

Answer 20

-provide nutrients and signals to dividing germ cells
-move germ cells along lumen
-secrete testicular fluid into lumen for sperm transport
-phagocytose faulty germ cells and their excess cytoplasm
-produce chemical mediators to regulate spermatogenesis

Question 21

Sertoli cells junctional complexes

Answer 21

**bundles of microfilaments

Two types of junctions:
1.Sertoli-sertoli tight junction forming blood-testis barrier; divides tubules into basal and adluminal compartments
>can open like zipper to allow germ cells to pass, protecting them from immune system

2. Sertoli-spermatid junction-specialized with spermatid nucleus

Question 22

Gonocytes

Answer 22

Part of male germline stem cells
-they come after primordial germ cells and before spermatogonial stem cells

Question 23

Gonocytes origin in rodents and humans

Answer 23

**hormone independent

Rodents: 13.5 dpc
Humans: 7wk of gestation

Question 24

When do gonocytes appear?

Answer 24

Appear when testis cords are formed AND when primordial germ cells have lost alkaline phosphatase activity and adopted male germ cell fate

Question 25

Gonocyte classification

Answer 25

1. Mitotis fetal gonocytes
2. Quiescent gonocytes
3. Mitotic postnatal gonocytes

Question 26

Mitotic fetal gonocytes

Answer 26

**multiplying M-prospermatogonia

-appear after PGCs and before mitotic arrest
-proliferate from 13.5 to 18dpc in rodents OR 18wks gestation in human embryos

Question 27

Quiescent gonocytes

Answer 27

** primary transitional (T1)- prospermatogonia

-distinctively large round cells (1 or 2 nucleoli in prominent nucleus)
-in transition to A-spermatogonia but in center of cords

-start after mitotic arrest and until 1-2 days in rodents OR wk/month after birth depending on species

Question 28

Mitotic postnatal gonocytes

Answer 28

**secondary transitional (T2)-prospermatogonia

-T1-prospermatogonia develop pseudopods, migrate to basement membrane, resume mitosis and differentiate into T2 prospermatogonia
>failure to form pseudopods=apoptosis; may lead to testicular cancer

-1-4 days postnatal in rodents; 8wks after birth in human boys