Reproductive Flashcards
Describe the hypothalamic-pituitary-gonadal axis
Hypothalamus releases gonadotropin releasing hormone (GnRH) that stimulates the anterior pituitary
Anterior pituitary will release follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) from gonadotrophs (cell type in anterior pituitary)
FSH and LH act on the ovaries to release progestins and estrogens, and on the testes to release androgens
Progestins, estrogens, and androgens then go to target tissues throughout the body as well as providing feedback on this axis
GnRH is under negative feedback by
Steroid hormones (progestins, estrogen, androgens)
Follicle stimulating hormone (FSH) acts on what cells in the ovaries and what cells in the testes and stimulates what in these organs?
Ovarian granulosa cells - stimulates follicular development
Sertoli cells in testes - aids spermatogenesis
Negative feedback for FSH and LH comes from what?
Steroid hormones and inhibin
There is a point at which rising estrogen actually causes positive feedback on LH to cause LH surge during ovulation
Luteinizing hormone acts on what cells in the ovaries and testes to stimulate what?
Ovaries - multiple, but remember LH SURGE ACTS ON OVARIAN GRANULOSA CELLS to stimulate ovulation; LH will also cause ovaries to produce steroid hormones
Testes - Leydig cells - steroid hormone synthesis
What are the three major roles of estrogens?
Fertilization
Pregnancy preparation and pregnancy
Long-term effects on physiology
How do estrogens influence fertilization?
Increase estrous behavior in some species
Increase uterine contractility
Open cervix to admit sperm
How do estrogens influence pregnancy preparation and pregnancy?
Stimulates endometrial development
Increase uterine progesterone receptors
Increases GnRH leading to LH surge that results in ovulation
What long-term effects do estrogens have on physiology?
Female secondary sex characteristics
What are the three major roles of progestins in the body?
Fertilization
Preparation for pregnancy and pregnancy
Lactation
How do progestins impact fertilization?
Decrease uterine contractility
Close cervix
Decrease FSH secretion
How do progestins influence preparation for pregnancy and pregnancy?
Increase uterine musculature
Increase endometrial gland secretions
How do progestins influence lactation?
Stimulates development of mammary alveolar cells
Inhibits milk production
What are the three roles of androgens in the body?
Spermatogenesis
Fertilization
Long-term effects on physiology
How do androgens influence spermatogenesis?
Actions on Sertoli cells
Maintenance of efferent ductular system
Maintenance of accessory sex glands
How do androgens influence fertilization?
Promote sexual behavior
What are the long-term effects of androgens on physiology?
Male secondary sex characteristics
Anabolic effect (promotes growth)
Where is prolactin produced?
Anterior pituitary
What does prolactin do?
Promotes lactation and maternal behavior, inhibits follicular development
Where is oxytocin produced?
Produced in hypothalamus and released from posterior pituitary
Where is inhibin produced?
Granulosa and Sertoli cells
What does inhibin do?
Selectively inhibits FSH (not LH)
In reproductive physiology, prostaglandins are most often considered in the context of __
Luteolysis
The follicular phase is divided into
Proestrus and estrus
What is the dominant hormone during the follicular phase
Estrogen
What happens during proestrus?
Early follicular development
Gamete maturation
What happens during estrus?
Final follicular development and sexual receptivity
What are the phases of the reproductive cycle?
Follicular phase (proestrus, estrus)
Ovulation
Luteal phase (metestrus, distrusted, luteolysis)
When does ovulation occur
End of estrus (shortly after end of estrus in some species)
What triggers ovulation?
LH surge (which is in turn triggered by rising levels of estrogen inducing positive feedback of GnRH in the hypothalamus)
What happens during ovulation?
Ovum is released into oviduct to encounter sperm for fertilization
The luteal phase is divided into __ (3 stages)
Metestrus
Diestrus
Luteolysis
What is the dominant hormone during the luteal phase of the reproductive cycle?
Progesterone
What happens in metestrus
Formation of corpus luteum
Transition from estrogen to progesterone dominance
What happens during diestrus
Corpus luteum is functional. And produces progesterone to prepare uterine environment to be favorable to pregnancy
What happens in luteolysis?
Destruction of corpus luteum and termination of luteal progesterone secretion
What are indications for vaginal cytology in female dogs?
- Evaluate inflammation in caudal reproductive tract
- Evaluate hemorrhagic discharge in caudal reproductive tract
- Look for evidence of malignancy in caudal reproductive tract
- Determine stage of reproductive cycle
What happens to cells on canine vaginal cytology around ovulation?
Become anucleate superficial epithelial cells aka cornified cells
Ovulation typically coincides with the finding of 70-90% cornified cells on cytology
