Midterm 2 - Lecture 19

Question 1

In birds where are the testis?

Answer 1

• they are internal
• testes develop on dorsal wall of the developing conceptus and stay there

Question 2

Phallus

Answer 2

• found near the cloaca to help with transferring semen to the hen’s cloaca
• tend to remain internal until the time of mating
• more prominent in aquatic species so there is less of a chance of contamination with H2O

Question 3

Do we know what causes the testes to develop in birds?

Answer 3

• no

Question 4

What does the mesonephric duct in the avian tract develop into?

Answer 4

• under the control of T4, develops into the vas deferens and epididymis

Question 5

What happens to the paramesonephric duct in the avian tract?

Answer 5

regressions
- cause unknown (unlike mammals where we know it is AMH)

Question 6

How are gametes different in birds?

Answer 6

• females are the heterogametic sex (ZW); males are homogametic (ZZ)

Question 7

What are the 2 theories of avian sexual development?

Answer 7

1) presence of female-specific W chromosome that triggers female
2) presences 2x- Z chromosome that confers maleness

Question 8

What are the 3 main factors that influence avian male sexual maturation?

Answer 8

1. age
2. body weight (influenced by genetics and nutrition)
3. Photoperiod
   - primary trigger initiating sexual maturation is increasing day length

Question 9

What does FSH result in?

Answer 9

• growth of sertoli cells in testis
• seminiferous tubule growth and differentiation
• supports spermatogenesis

Question 10

What does LH result in?

Answer 10

• androgens (T4) produced by leydig cells in the testis
• comb and testicular growth
• spermatogenesis

Question 11

Where are avian testes located?

Answer 11

in the body cavity attached to the dorsal body wall

Question 12

At what temperature does spermatogenesis occur?

Answer 12

~41 degrees (equivalent to core body temp)

Question 13

How is avian testis structure similar to mammalian testes?

Answer 13

• seminiferous tubules in the testicular parenchyma make up the majority of the testicular mass
• well developed Blood Testes Barrier creates an immunologically privileged site that prevents immune system from affectig the developing sperm

Question 14

How long does spermatogenesis in chickens require?

Answer 14

~14-16 days

Question 15

How are avian sperm heads shaped?

Answer 15

• filiform (rather than paddle shaped)

Question 16

What are 5 key features of avian sperm morphology?

Answer 16

1. highly condensed nucleus
2. high surface: volume ratio
3. sensitive to changes in osmolarity
4. don’t tolerate dilution well
5. susceptible to irreversible damage to organelles and structure

Question 17

What are 4 features of the avian epididymus?

Answer 17

1. not coiled and subdivided like mammals
2. 24-72 hrs for sperm to travel from testis, through the epididymus, to vas deferens
3. changes to the sperm plasma membrane surface allows recognition in female reproductive tract
4. motility and fertilizing ability gained in epididymus

Question 18

5 features of the Vas deferens

Answer 18

1. ~20cm long
2. highly convoluted tube
3. newly generated sperm are stored in the ends of the vas deferens
4. sperm travels through Vas deferens in 24-48 hrs (regularly ejaculated)
5. primary storage site- sperm accumulation creates a cloacal protuberance

Question 19

What is the advantage of having highly concentrated semen?

Answer 19

• frequent matings of short duration to large group of hens
• small amount of concentrated semen ensures a higher probability of fertilization
• only 1% of sperm ejaculated enter hen’s sperm storage tubule (SST)