Avian reproduction Flashcards
List the features of the male reproductive tract in the bird
- Gonads (testis)
- Epididymis
- Ductus deferens
- No accessory glands
- +/- phallus
Describe the testis of birds
- Paired
- Large compared to mammals
- Intra-abdominal
- Cranioventral to first kidney lobe, near abdominal air sac
- Can increase 300-500x when breeding
Describe the duct system in male birds
- Epidydimis and ductus deferens
- E is small
- DD highly coiled, terminates in urodeum on papilla
What is the seminal glomus in bird?
Some species of bird have enlarged end of ductus deferens used for sperm storage
Give the 2 insemination methods in birds
- No phallus/no phallus but no intromission = cloacal kiss
- Phallus with intromission
Describe the cloacal kiss in birds
- Method of insemination
- Male everts cloacal wall to everted opening of female oviduct
- Cloaca to cloaca contact
What are the components of the female avian reproductive tract?
- Ovary
- Infundibulum
- Magnum
- Isthmus
- Shell gland
- Vagina
- Oviduct
Describe the ovaries of birds
- Legt ovary function
- Right usually regresses during development and becomes vestigial
- Look like bunch of grapes, yellow
What are the components of avian follicles?
- Oocyte
- Granulosa cells
- Theca cells
Describe the oocytes within follicles in birds
- NO zona pellucida
- Membrana granulosa and cumulus oophorus present, simple structure
- Yellow yolk within each follicle
What is the yellow yolk in birds analogous to?
The oocyte
Describe follicle development in the birds
- Slowly at first, lipids deposited in egg’s yolk
- Small number of oocytes enlarge and deposit white primordial yolk
- Enter rapid growth phase and deposit yellow yolk
- From this point on very rapid enlargement
- Surrounded by granulosa and theca cells, no fluid filled cavity
Describe follicle maturation in birds
- Not in synchrony
- F1 largest, matures first, then F2 then F3
- Smallest white follicles, larger yellow
- Large number of smaller white folicles, will become atretic
What happens at ovulation in brids?
Follicle splits open to release egg (yellow yolk)
Describe the post-ovulatory follicle in birds
- Thin walled sac
- Hypertrophied granulosa cells remain
- Metabolically active for a number of days (8-10)
- Non-steroid hormones being produced
What are the actions of the non-steroid hormones being produced by the granulosa cells in birds following ovulation?
Role in ovipostiion, egg laying and nesting behaviour
What is the function of the granulosa cells in birds (compare this to mammalian)?
- Progesterone production
- In mammals, granulosa cells produce E2
What is the function of the theca cells in birds (compare this to mammals)?
- Production of E2
- In mammals produce progesterone
Where is the progesterone from luteinised cells derived from in birds?
Graulosa and theca cells
Describe the egg laying endocrinology
- E2 rises a couple of weeks prior to egg laying
- E2 linked preparation for egg layinng
- Ovulation preceded by increased LH and progesterone
- Increased LH leads to increased progesterone
- Progesterone positive feedback to hypothalamus to increase LH
What changes occur near ovulation that lead to the hormonal changes seen in birds?
- Follicles mature, enzyme activity in theca cells decreases = less conversion to oestradiol
- Increased activity in granulosa cells = more progesterone produced at time of ovulation
Describe the oestrogen-linked preapartion for egg laying in birds
- Synthesis of calcium ATPase
- Medullary spaces calcified
- VLDL precursors to yolk produced and transferred to yolk
- Oviduct enlarges
- Plumage, comb size and receptivity altered
When is oestrogen highest in the bird?
At start of follicular development
What is the open period in birds?
The window of time for LH release, lasts around 8-10 hours from onset of darkness to around 1 hours after lightonset
Describe ovulation in relation to the open period
- In F1 follicle, enough P4 in open period = LH surge = ovulation
- NO CL formed
What follicles can produce progesterone and what is the function of this?
- Mature follicles only
- Suppress GnRH and LH if high levels
- So only mature produce to avoid suppression