chapter 16 part c

Chapter 16: Reproductive System & Development

Part C: Menstrual cycle, Pregnancy

1.     Menstrual (uterine) cycle

a.    Overview

                                          i.    Cyclic changes of the endometrium

                                        ii.    Regulated by cyclic production of estrogen and progesterone

                                       iii.    FSH and LH regulate the production of estrogen and progesterone

                                       iv.    Both female cycles are about 28 days in length

                                         v.    Ovulation typically occurs about midway through cycle on day 14

1.     However, there are a lot of variations

b.    Stages

                                          i.    Menstrual phase

1.     Days 1-5

2.    Functional layer of the endometrium is sloughed

3.    Bleeding occurs for 3-5 days

4.    By day 5, growing ovarian follicles are producing more estrogen

                                        ii.    Proliferative stage

1.     Days 6-14

2.    Regulation of functional layer of the endometrium

3.    Estrogen levels rise

4.    Ovulation occurs  in the ovary at the end of this stage

                                       iii.    Secretory stage

1.     Days 15-28

2.    Progesterone levels rise and increase the blood supply to the endometrium

3.    Endometrium  increases in size and readies for implantation

4.    If fertilization does occur:

5.    Embryo produces a hormone(HCG) that causes the corpus lutem to continue producing its hormone

a.    If fertilization does not occur:

b.    Corpus luteum degenerates as LH blood levels decline

c.    Hormones produced by ovaries

                                          i.    Estrogen

1.     Produced by follicle cells

2.    Cause secondary sex characteristics:

a.    Enlargement of accessory organs

b.    Development of breasts

c.    Appearance of axillary and pubic hair

d.    Increase in  fat beneath the skin, particularly in hips and breasts

e.    Widening and lightening of the pelvis

f.    Onset of menses (menstrual cycle)

                                        ii.    Progesterone = the hormone of pregnancy

1.     Produced by the corpus luteum

2.    Production continues until LH diminishes in the blood

3.    Does not contribute  to the appearance of secondary sex characteristics

4.    Helps maintain pregnancy

5.    Prepares breasts for milk production

6.    Feedback

d.    Mammary glands

                                          i.    Present in

1.     Modified

                                        ii.    Function is

                                       iii.    Stimulated by