tailieunhanh - Ebook Atlas of histology of the juvenile rat: Part 2

Part 2 book "Atlas of histology of the juvenile rat" includes content: Female reproductive system, male reproductive system, the endocrine system, immune system, hematopoietic system, the eye and harderian gland, urinary system, cardiovascular system | Chapter 7 Female Reproductive System Catherine A. Picut and Amera K. Remick WIL Research Hillsborough NC United States INTRODUCTION During the neonatal period PND 0 to 7 the ovary is a solid parenchymal mass with no medulla cortex or hilus. It The female reproductive tract composed of the ovaries ovi- is comprised of ovigerous nests which are packets of oogo- ducts uterus cervix and vagina is immature at birth and nia enveloped by undifferentiated mesenchyme. Within the develops into a fully functional reproductive unit by PND 42. first few days the ovigerous nests transform into primordial The ovary is considered mature once the rat has experienced follicles ie a primary oocyte surrounded by a single layer at least two ovulatory cycles and this typically occurs by of flattened pre-granulosa cells . Follicular development PND 42. Follicle development is pituitary independent dur- starts in the core of the ovary where these primordial fol- ing the first 10 days of life and becomes dependent on and licles become primary follicles primary oocyte surrounded receptive to gonadotropins thereafter. Early antral follicles by a single layer of cuboidal granulosa cells and secondary are not typical and develop from the medulla outward to follicles primary oocyte surrounded by more than one layer the cortex. After PND 21 apoptosis of granulosa cells first of cuboidal granulosa cells . During this neonatal period becomes apparent. Then a wave of follicular atresia ensues of development the ovary is independent of and unre- at around PND 27 which has the result of clearing away old sponsive to pituitary gonadotropins LH luteinizing hor- follicles and leaving a defined cortex and medulla. From that mone or FSH follicle stimulating hormone Picut et al. point forward ovulatory follicles develop in the cortex and 2015 . Follicular development is under the control of local first ovulation occurs at around PND 33. Significant biologi- paracrine and autocrine factors. cal