Lecture 26 3/19/24 Flashcards
What are the characteristics of the cervix?
-thick-walled and rigid
-physical barrier from exterior
-secretes mucus during pregnancy to isolate uterus (cervical seal)
-produces mucus during estrus to lubricate vagina and flush material
How does the cervix respond to hormones?
-open and relaxed in response to estrogen
-closed and rigid in response to progesterone
What is the utero-tubal junction?
the connection between the uterine horn and the oviduct
What is the main ligament supporting the uterus?
broad ligament
What are the characteristics of a bicornuate uterus?
-two uterine horns
-small uterine body
-length of horns depends on degree of fusion between paramesonephric ducts
What influence does progesterone have on the uterus?
-lumen secretes uterine milk
-induces uterine quiescence/low contractility
What influence does estradiol have on the uterus?
-enhanced immune system response
-increased uterine contractility
What are the layers of tissue of the uterus?
-serosa (outer)
-muscularis
-endometrium (inner)
Why is it important that the muscularis allows the uterus to contract?
-transport of secretory products and gametes
-expulsion of fetus and fetal membranes during parturition
What is the importance of the endometrial folds?
provide the uterine surface for development of the placenta
What is the function of the infundibulum?
to capture the newly ovulated oocyte
What is the function of the muscularis of the oviduct?
transport newly ovulated oocytes and spermatozoa to the site of fertilization
What is important about the substances secreted by the oviduct mucosa?
-provides optimum environment for free floating, unfertilized oocyte
-sustains spermatozoal function until oocyte arrives after ovulation
-provides suitable environment for early embryo
What occurs in a complete ovarian cycle?
-ovulation occurs
-antral follicles transform into corpus luteum and produce progesterone
-corpus luteum is destroyed
-new follicles develop and produce large amounts of estrogen
-ovulation occurs again; new cycle
Where is the population of oocytes housed?
cortex of ovary
What is found in the ovarian medulla?
vasculature, nerves, and lymphatics
What are the three layers of an antral follicle?
-theca externa
-theca interna
-granulosa cell layer
What is the theca externa?
loose connective tissue that surrounds and supports the follicle
What is the theca interna?
layer responsible for production of androgens under the influence of LH
What are the products of the granulosa cell layer?
-estrogen
-inhibin
-follicular fluid
What is the 2-cell, 2-gonadotropin model?
-binding of LH to its receptors on theca interna cells leads to conversion of cholesterol into testosterone
-binding of FSH to its receptors on granulosa cells leads to conversion of testosterone into estradiol
What is the important step in preparation of the follicle for ovulation?
synthesis of LH receptors by granulosa cells
Which conditions must be met for the final stages of maturation to occur during folliculogenesis?
-animal must have undergone puberty
-must be appropriate season for animals with seasonal repro. patterns
-minimal body condition score must be met
-proper hormonal environment/absence of progesterone from previous corpus luteum
What are the characteristics of oocyte division in the prenatal stages?
-germ cells divide through mitosis
-generate large number of oocytes to form ovarian reserve
-divide into oogonia/primary oocytes
-oocytes enter first meiotic prophase after last mitotic division
-cells arrest in meiotic prophase until after puberty
What are the characteristics of oocyte division post-puberty?
-meiosis resumes
-primary oocyte becomes secondary oocyte
-typically complete first meiotic division at the time of ovulation
-second meiotic division occurs at fertilization
What is the key characteristic of a prepubertal female?
lack of gonadal estradiol to stimulate the surge center
When is puberty initiated in the female?
when GnRH neurons can respond completely to positive and negative feedback
Which factors impact the development of hypothalamic GnRH neurons in the female?
-threshold body size and/or composition
-exposure to certain environmental or social cues
What is ovarian senescence?
depletion of primordial follicles in a female, at which point repro. cyclicity stops
What are the main effects of ovarian senescence?
-decrease in reproductive efficiency
-prolonged and irregular estrous cycles
-eventual cessation of estrous cycles
-net decline in blood estrogen levels
-increases in FSH due to lack of inhibin
-decline in progesterone
What is the main difference between the preantral and antral stages?
there are much higher levels of FSH and LH during the antral stages since the inhibition of GnRH by progesterone is no longer occurring
Which type of follicle is able to enter a follicular wave?
antral follicles
What must occur in order for a follicular wave to result in ovulation?
breakdown of the previous CL and removal of progesterone
How does folliculogenesis differ from follicular waves?
-folliculogenesis is the complete process of development and maturation of oocytes/follicles
-follicular waves are the last few days of folliculogenesis
What is follicular atresia?
degeneration of antral follicles
What is the main trigger for follicular atresia?
the follicle not being exposed to the right concentration of gonadotropin
What is ultrasonography?
use of high-frequency sound waves to generate an image
What are the four types of reflection on ultrasound?
-fluid: anechoic/black appearance
-soft tissue: hypoechoic/grayish appearance
-bone: hyperechoic/bright white appearance
-air: dispersion/acoustic shadow/no image
