Reproduction in Birds- Structure and Function Flashcards Preview

ANSC*3040- Reproduction > Reproduction in Birds- Structure and Function > Flashcards

Flashcards in Reproduction in Birds- Structure and Function Deck (21)
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1
Q

what is so special about birds

A

most birds possess 1 functional ovary (left) and one left oviduct

birds lay eggs in clutches= repeat ovulations
- domesticated chickens do not have time between clutches

2
Q

Gonad Determination

A

initial embryo development similar to mammals= lead to undifferentiated gonads populated with primordial germ cells

3
Q

Differentiation of gonads

A

starts at embryonic day 6 in chickens (out of 21 days)

testes, medulla, develops with Sertoli cells

ovary, cortex develops with oogonium

both grow at meso-nephrous kidney

4
Q

Sex Determination

A

Heterologous sex chromosomes carried by females (males ZZ; females ZW)
ZW unrelated to XY as they evolved from different autosomal chromosomes
Z is large and carries the testis determinant factor, DMRT1
the smaller W has few genes and is largely heterochromatic

5
Q

two theories on sex determination

A

dosage: more Z products without compensation= male
dominance: W powers over Z to become female

6
Q

birds are more sensitive to estrogens

A

to feminize –> add estrogen

to masculinize –> add androgens

7
Q

Ovary

A

undifferentiated female gonads produce higher levels of estrogens (from incubation day 5.5)

development of a left ovary, regression of the right

right mullerian duct regresses: left remains and later forms the oviduct

lack of estrogen in males allows testes to develop

8
Q

Disruption to normal development

A

estrogen may cause
ovotestis formation
exposure of male embryos to estrogenic substances- development of a partial ovary on the left

disruption of estrogenic production in females
- functional testes may appear on the right

9
Q

Gynandromorphic Chickens

A

Half ZZ and Half ZW
each cell becomes either male or female based on its genetic sex
somatic sex independent of the gonads

male brain is default in chickens

10
Q

The Hen: Follicular Development

A

at hatch: thousands of prefollicular germ cells are present

5-9 days after hatch: prefollicular germ cells are surrounded by granulosa cells

at sexual maturation, a cohort of small follicles are recruited to develop under FSH

they start producing steroids which stimulate

  • calcium deposition in bone
  • synthesis of yolk precursors in the liver
  • development of the reproductive tract
11
Q

Precursors for yolk formation

A

transferred tot he follicles

  • estrogens stimulate lipid synthesis in the liver up to 14 times= 19g per day
  • precursors travel in the form of VLDL to the theca layer
  • VLDLs pass through the vitelline membrane, binds to receptor and are internalized by endocytosis
  • vitamins also accumulate in the yolk
12
Q

The Infundibulum

A

captures the ovum after ovulation
site of fertilization
deposition of the outer vitelline membrane and the chalazae
stay here for about 15 minutes

13
Q

The Magnum

A

site of egg white production and deposition
proteins stored in granules in the epithelial cells
3 h transit

14
Q

The Isthmus

A

cells in the tubular glands secrete fibrous material
site of shell membrane formation
1.5 h transit

15
Q

The Shell Gland

A

anterior portion

  • water/electrolytes
  • initiation of CaCO3 deposition
  • 5 h transit

posterior portion (pouch)
- active CaCOe depostion
- protein and enzymes,es help anchoring crystals
total transit 18-22h

16
Q

The Vagina

A

from the shell gland to the cloaca
muscle layer very well developed
mucosa rudimentary with no tubular glands
contains the sperm storage tubules

17
Q

Oviposition

A

increased muscle activity from shell gland
nesting behaviour
coordination with ovulatory cycle
- next ovulation 45 min after oviposition

18
Q

The Rooster: Sperm Development

A

at hatch: thousands spermatogonia are present
after hatch: seminiferous cords and tubes develop

avian sperm have a long tail and a thing head with almost no cytoplasm

testes located within the abdominal cavity= spermatogenesis occurs at core temperature 42ºC

19
Q

Fertilization and storage

A

1 insemination can leaf to over 1 week of fertile eggs

20
Q

Avian Reproductive Cycle

A

chick (brooding period) –> >12 h light (up to 20)
juvenile (sexually immature) –> 8h light needed to reset the photosensitive clock

sexual maturation >12h light

active reproductive period 14-16h light

21
Q

Photorefractoriness

A

no response to light stimulation: involution of the reproductive tract (no longer an issue in commercial strains of layers)