Avian Reproductive Anatomy, Hormonal Control, and Egg Formation

Vocabulary flashcards covering avian reproductive anatomy, endocrine control mechanisms, photoperiod influences, and the step-by-step processes of egg formation and oviposition.

GnRH-I

A form of gonadotropin-releasing hormone that stimulates the synthesis and release of anterior pituitary hormones in hens.

GnRH-II

A form of gonadotropin-releasing hormone involved in regulating mating and courtship behaviour in birds.

Arginine Vasotocin (AVT)

A hormone released from the posterior pituitary that induces uterine contractions, triggers prostaglandin release, and causes behavioural changes during oviposition.

Prostaglandins

Hormones that induce uterine contractions and relax the vagina and uterine sphincter during egg laying.

Oviposition

The process of laying an egg, where vaginal mucus secretion, cloacal stretching, and uterine contractions force the egg to rotate 180 degrees out of the vagina.

Stigma

The line on a mature ovarian follicle along which it splits during ovulation, triggered by an LH surge, to release the yolk into the oviduct.

Infundibulum

The first segment of the oviduct (15–30 minutes) that catches the mature ovum and yolk, forms the vitelline membrane, and serves as the site of fertilisation in breeder birds.

Magnum

The segment of the oviduct (3–4 hours) that secretes egg white protein (albumen) and utilizes inner spiral ridges to form the chalazae.

Isthmus

The region of the oviduct (3–4 hours) that produces some albumen and forms the fused inner and outer shell membranes.

Uterus (Shell Gland)

The region of the oviduct where the egg resides for about 19 hours to undergo plumping with water and electrolytes, shell formation utilizing calcium, and pigmentation.

Vitelline Membrane

A protective membrane formed in the infundibulum that surrounds the yolk and regulates movement between the yolk and albumen.

Chalazae

Twisted protein structures formed in the magnum that anchor the yolk in the center of the egg.

Cuticle

The outermost waxy layer of the eggshell composed of glycoproteins, pigments, and hydroxyapatite that limits water loss and provides antimicrobial protection.

Mammillary Layer

The eggshell layer where calcite crystals nucleate on mammillae cores.

Palisade Layer

The layer of the eggshell composed of calcite columns.

Pre-hierarchical Follicles

Primary ovarian follicles (such as SWF, LWF, and SYF) that grow slowly and are responsive to FSH.

Pre-ovulatory Follicles

Ovarian follicles arranged in a size hierarchy (F5 to F1) that are responsive to LH prior to ovulation.

Hypothalamic-Pituitary-Gonadal (HPG) Axis

The endocrine control pathway in which the hypothalamus releases GnRH to stimulate anterior pituitary hormones (LH and FSH), which act on the gonads.

Pullet Phase

The developmental phase of a young hen during which yolk and oviduct development begins, initiated by FSH.