REVISION: Equine reproductive anatomy and physiology (male and female)

Question 1

What accessory glands does the stallion have?

Answer 1

ampulla (each deferent duct) 2 seminal vesicles 1 prostate gland 2 bulbourethral glands

Question 2

How is the stallion repro tract supported within the pelvic cavity?

Answer 2

by the genital fold

Question 3

What are the 4 layers of the scrotum?

Answer 3

skin - sweat glands tunica dartos - SMCs for vertical mobility fascia - vertical and lateral movement vaginal tunic - watery fluid facilitates testes movement

Question 4

When do testes descend?

Answer 4

enter the inguinal canal before closure of internal inguinal ring during first 2 weeks after birth and descend into scrotum

Question 5

What is the size of a mature equine testis? Weight?

Answer 5

Length: 80-100mm Width: 50-80mm Weight: 225g

Question 6

What does testicular parenchyma consist of?

Answer 6

seminiferous tubules and interstitial tissue

Question 7

When does equine male pre-pubertal stage start?

Answer 7

approx 6 months old, few colts produce sufficient sperm for ejaculation before 14 months of age.

Question 8

How long does it take for a spermatozoa to form?

Answer 8

57 day cycle (70,000 sperm/second)

Question 9

What is the function of the external cremaster muscle?

Answer 9

temperature control

Question 10

What end of the testis is the corpus epididymis found?

Answer 10

cylindrical, loosely attached to dorsal testis, sperm storage (also ampullae)

Question 11

How wide is the epididymal duct versus the ampulla?

Answer 11

Epididymal duct = 5mm Ampulla = 18mm (paired ampullae contain crypts and glands)

Question 12

What is the pelvic portion of the urethra covered in?

Answer 12

striated urethralis mm - contracts during ejaculation

Question 13

What are seminal vesicles like?

Answer 13

elongated hollow pouches, 15-20mm diameter, seminal plasma

Question 14

Describe the prostate gland

Answer 14

single firm solid gland with two narrow lobes connected via the transverse isthmus, seminal plasma

Question 15

Where are the bulbourethral glands?

Answer 15

either side of the ischial arch, function unclear in stallions, also called Cowper’s glands

Question 16

Is the corpus spongiosum erectile?

Answer 16

Yes (like corpus cavernosum) but is not contained within the tunica albuginea, small and surrounds the urethra

Question 17

What is the size of a stallion’s penis: Relaxed? Erect?

Answer 17

RELAXED: 50cm long, 2.5-5cm diameter, 15-20cm in prepuce ERECT: 50% increase in length and diameter, 300-400% increase in diameter of glans penis

Question 18

Outline oxytocin in stallions.

Answer 18

Leydig cells release oxytocin into interstitial fluid. This facilitates rhythmic contraction of the seminiferous tubules to help evacuate sperm.

Question 19

How is spermatogenesis regulated

Answer 19

Sertoli cells release inhibin and activin regulate this. Episodic bursts of LH control testosterone production. Testes also produce high levels of oestrogens but precise function unknown (also activin/inhibin)

Question 20

What controls erection, emission and ejaculation?

Answer 20

Erection - initiated by cerebral responses, penile arterioles dilated by PS override of nromal S control Emission - sympathetic impulses Ejaculation - PS impulses, series of strong pulsatile contractions of urethralis and bulbospongiosus mm results in 5-7 jets of semen, first few pulses contain more sperm than later

Question 21

What causes variation in semen

Answer 21

age month testicular size extent and duration of sexual arousal

Question 22

How much sperm do stallions have enough for ejaculate-wise?

Answer 22

optimum = 1/day (for ideal sperm reserves) May have sufficient reserves for 2-3 ejaculates per day in season Libido, testicular size and morphologically-normal live sperm numbers are limiting factors for mare numbers

Question 23

How are daylight length and melatonin related?

Answer 23

As daylight length increases, melatonin production by pineal gland decreases and inhibition of the HPO axis is downregulated. This leads to production of hypothalamic GnRH. When in large enough quantities, FSH and LH release is stimulated and cyclicity returns. Other factors such as nutrition, age and breed also play a role in the transition form anoestrous to normal cycling.

Question 24

What do oestrogens produced by the ovary regulate? 3

Answer 24

behaviour, tract changes, LH

Question 25

What do ovarian follicles secrete?

Answer 25

inhibin (this inhibits FSH)

Question 26

What does LH sitmulate (mare)?

Answer 26

ovulation and luteinisation

Question 27

Outline maternal recognition of pregnancy in mares

Answer 27

Blastocyst capsule oestrogrens prevent endometrial gland secretion of PGF2a which would occur if failure of recognition or no blastocyst

Question 28

What type of placentation does this show?

Answer 28

diffuse epitheliochorial placentation

Question 29

What does this show?

Answer 29

equine microcotyledon at full term

Question 30

Outline the hormonal changes during equine pregnancy

Answer 30

maternal recognition - 14 day s- blastocyts capsule secretes oestrogens 2nd wave of ovarian follicles ovulate and supplement progesterone chorionic girdle form endometrial cups which secrete eCG 35-100 days (pregnancy test 45-95 years) Foetal gonads secrete oestrone sulphate 100 days to full term (pregnancy test 120 - 300 days)

Question 31

What does this show?

Answer 31

endometrial cups