Equine Reproductive Anatomy - Male

Question 1

What is the source and role of GnRH (male)

Answer 1

Hypothalamus

stimulate pituitary to secrete FSH/LH

Question 2

What is the source and role of FSH (male)

Answer 2

Pituitary

stimulate Sertoli cells to mature sperm

Question 3

What is the source and role of LH (male)

Answer 3

Pituitary

stimulates leydig cells to release testosterone

Question 4

What is the source and role of testosterone (male)

Answer 4

Testes (leydig cells) and adrenal glands

stimulate sertoli cells to produce sperm

Question 5

What is the source and role of oestrogen (male)

Answer 5

Testes (leydig cells)

regulation of laminal fluid

Question 6

Are males seasonal breeders

Answer 6

Yes - long day breeder

sperm production all year but quantity/quality poor

Question 7

Describe testes morphology

Answer 7

• ovoid shape
• sit in inguinal region horizontally
• 10cm length average

Question 8

Describe testicular development

Answer 8

• start in abdomen and decend into scrotal position

- right decends first

Question 9

Why is it important to check if testes descended

Answer 9

problem when one is retained in abdomen
need lower temperature for sperm to survive, too hot at body temperature in abdomen
maintain at 35-36 celcius

Question 10

Cryptorchid and rig

Answer 10

= one testes decended and one inside retained testicle
abdominal pressure doesnt push testes down through ingunor canal
= castrated one testicle, one remain

Question 11

How to check if testes descended/are there

Answer 11

feel for testicle
test testosterone levels
HCG test
blood test for oestrogen sulfate in leydig cells (oestrogen higher in stallion)

Question 12

What is the HCG stimulation test

Answer 12

inject horse with human chorionic gonadotropin
high level = stallion with testes
low level = no testes

Question 13

What is androgen-binding hormone

Answer 13

glycoprotein produced by sertoli cells and binds to testosterone. keeps testosterone at elevated level in seminiferous tubule

Question 14

What temperature should testes maintained and how adapted to do so

Answer 14

30.5-32.5 celcius
external location close to body wall
scrotal skin - contains sweat gland to aid temp regulation

Question 15

What is the tunica dartos, cremaster muscle and pampiniform plexus

Answer 15

lining of muscle within the scrotum which contracts (testes closer to abdomen, reduce scrotal surface and heat loss) and relaxes to temperature regulation

moves testes up/down/sideways also for temp reg and protection

formed by dense cappilary network where arterial and venous supplies come into close contact
- warm blood enter testes by artery loses heat to cooler venous return

Question 16

Where and how testes suspended

Answer 16

from abdominal cavity wall by spermatic cord which contains blood vessels, nerves and ductus deferens

Question 17

What is the ductus deferens

Answer 17

transports sperm from testes through penis

between epididymus and urethra (through spermatic cord, abdomen and ampulla

Question 18

What is pampiniform plexus

Answer 18

site where artery and vein intertwine
temp reg = form of heat
at the most cranial aspect of testes

Question 19

What is the tunica albuginea

- lobes

Answer 19

fibrous layer that arises from peritoneum covering spermatic cord, testes and epididymis
provide support to suspended testes
- sheets of tunica albugina divide into lobes
- each lobe is mass of convoluted seminiferous tubules with intertubular areas
- each area responsible for oneof 2 functions ~ gameotogenic (sertoli cells and SemT) or ~ steroidogenic (leydig cells and intertubual tissue)

Question 20

Describe the testes internaly

Answer 20

composed of semineferous tubules
embedded with supportive tissue (leydig cells)
semineferous tubules lined with sertoli cells where spermatogenesis occurs

Question 21

Claudin 11 in spermatogenesis

Answer 21

expresed by sertoli cells
role = tight junction formation in the testis, helps the sertoli cells for the blood testis barrier, if absent stops spermatogenesis progressing past meiosis and leads to infertility

Question 22

What is the epididymis

Answer 22

seminiferous tubules empty into it
lies dorsally over testes
cylindrical 70cm
Caput(head)/Corpus(body)/Cauda(tail) 
surrounded by muscle to aid sperm movement

Question 23

What is the urethra and corpus spongeosum

Answer 23

excretory canal for urine and semen
surrounded by striated muscle - contracts during ejaculation
surrounded by corpus spongiosum (spongy tissue that aids erection)
urethra opens within urethral fossa at the end of glans penis w/urethral process projecting beyond glans

Question 24

What are the seminal vesicles

Answer 24

• lie adjacent to neck of bladder
• add seminal plasma and nutrients to semen via urethra ~ (SP) high conc of potassium, citric acid and gel
• volume of secretion depends on testosterone cocs
• 15-20cm long 5cm wide

Question 25

What is the prostate

Answer 25

- bilobed structure with single exit to urethra - situated between bulbourethral glands and ampulla - H-shaped gland - produces alkaline secretion to buffer acidic urine before and during ejaculation

Question 26

What are the Bulbourethral glands

Answer 26

- lie either side of urethra near ischial arch - secrete pre-ejaculatory fluid to flush urethra of urine and bacteria and thick mucous (lubrication) - contain lots of fibrous connective tissue

Question 27

Penis - physical structure

Answer 27

- cylindrical, muscular - extends from ischial arch of pelvis to the umbilicus root body and shaft - resting = lies retracted within prepuse and held by retractor muscle - 50cm length and 2.5-5cm diameter (not erect) - many sebaceous glands within folds of prepuce - build up of smegma

Question 28

Penis - root

Answer 28

- attatched to pelvis via ischiocavernous muscles | - bulbospongious muscle covers root and ventrally w/in penis around urethra

Question 29

Penis - body

Answer 29

- composed mostly corpus cavernosum - spongy tissue that becomes engorged (swell with blood) - corpus spongiosum - spongy tissue that surrounds urethra (also engorges), surrounded by bulbospongious muscle ~ contained w/in tunica albugina - contains erectile tissue - haemodynamic = responds to blood pressure

Question 30

What is the glans penis What is strange about the retractor muscle in stallions

Answer 30

enlarged free end of penis, filled with nerve endings and where fossa glandis located under-developed ventral to bulbospongiosus muscle

Question 31

What cell no. increases during breeding season and why role of sertoli cells

Answer 31

setoli cells becuase increase in seminiferous tubule length - aid sperm development - form blood testis barrier (claudin 11) - phagocytic (digest degenerating germinal cells - secrete luminal fluid and proteins

Question 32

Where is sperm stored

Answer 32

- cauda epidydimis - if not passed up vas deferens as result of ejaculation, degenerate and absorbed overtime = allow fresh supply of sperm available

Question 33

What are the vas deferens

Answer 33

= connects epidydimis to urethra, passing the accessory glans and into penis - thick muscular wall w/ 3 layers ~ inner oblique ~ middle circular ~ outer longitudinal = propell sperm and surrounding fluid by peristalsis (wave muscle contractions) - lumen = small and folded ~ maximise surface area aiding sperm storage and reabsorption of testicular fluids

Question 34

What is the ampulla glands and why important

Answer 34

- glands paired outfoldings of vas deferens where meets the urethra - secretions high in ergothionine = antioxidising agent that cleans up toxic by-products of sperm metabolism

Question 35

What is seminal plasma and role

Answer 35

= major fluid fraction of semen - provision of energy and protection of sperm form changes of pH, osmotic pressure and oxidisation - contains gel which forms partial clot in semen

Question 36

What are accessory glands

Answer 36

4 glands - bulbourethral - seminal vesicles - prostate - ampulla primarily responsible for secretion of seminal plasma

Question 37

What is prepuse and retractor muscle

Answer 37

= double folded covering to penis - w/in inner fold lies glans end penis - runs along bottom of penis - contraction returns penis to prepuse