1. Organismal Development Part 4
Female Animals

2. Important concepts from previous units:
Ligands can be hormones.
The Signal Transduction Pathway has three parts – Reception, Transduction, and Response.

3. I. Female Reproductive Cycles
A. Cycles favor energy conservation, especially during harsh environmental times, such as winter.
B. Female reproductive cycles are controlled by hormones and environmental cues, such as temp., rainfall, day length.

4. Important Female Anatomy
Uterus – This is the muscular structure for gestating (growing) a fetus. (A.K.A. Womb)
Endometrium – The inside lining of the uterus. It is responsible for menses. It can act as a cushion for a fetus.
Fallopian Tubes (Oviducts) – These are the tubes leading from each ovary to the uterus.
They are lined on the inside with ciliated cells. These help in collecting and moving the egg toward the uterus.
Ovaries – These are the organs responsible for egg and hormone (estrogen and progesterone) production.
Follicle – This structure is the protective case for a maturing egg, called an ovum.
Ovulation – This term refers to the releasing of an adult egg ready to be fertilized. It is caused by LH hormone.

5. Female Reproductive Anatomy
Oviduct
Ovaries
Follicles
Corpus luteum
Uterine wall
Uterus
Endometrium
Cervix
Vagina

6. Oogenesis – This is the “creation” of a haploid egg.
Oogonium – This is the diploid cell that undergoes meiosis. It stops after the first DNA division to become a primary oocyte.
It will be reactivated by FSH coming from the anterior pituitary at the start of a menstrual cycle.
The secondary oocyte will be released at ovulation. (It will perform the second division if and after fertilization occurs.)
Process results in one haploid cell and 2 polar bodies. (All organelles of the cell come from the mom’s egg cell.)

8. Oogenesis in the ovaries
Ovary
Primary germ cell
in embryo
Differentiation
Oogonium
in ovary
Oogonium
Mitotic
division
Primary
oocyte
within
follicle
Primary
oocyte
Completion of meiosis I
and onset of meiosis II
Growing
follicle
Secondary
oocyte
First polar body
Ovulation
Entry of sperm
triggers
completion
of meiosis II
Mature follicle
Ruptured
follicle
Second polar body
Ovum
Ovulated
secondary oocyte
Corpus luteum
Degen-
erating corpus luteum

9. Female Hormonal Pattern (This is cyclic; unlike males.)
Menstrual cycles - This cycle mainly occurs in humans. (A cycle is usually 28 days long.)
It requires menstruation to release the sugar rich endometrium of the uterus, if no pregnancy occurs.
Estrous cycles - Mainly occurs in other mammals. (No menstruation occurs because the endometrium is reabsorbed.)
Estrous - This is a period of increased sexual activity. (A.K.A. heat) It last only a couple of days per year.

10. Female Reproductive Cycle in Humans
Control by hypothalamus
Inhibited by combination of
estrogen and progesterone
Hypothalamus
Stimulated by high levels
of estrogen
GnRH
Anterior pituitary
Inhibited by low levels of
estrogen
FSH LH
Pituitary gonadotropins
in blood
Changes in the uterus coincide with changes in the ovaries. LH
FSH
FSH and LH stimulate
follicle to grow
LH surge triggers
ovulation
Ovarian cycle
Corpus
luteum
Degenerating
corpus luteum
Growing follicle
Mature
follicle
Follicular phase
Ovulation
Luteal phase
Estrogen secreted
by growing follicle in
increasing amounts
Progesterone and
estrogen secreted
by corpus luteum
Ovarian hormones
in blood
Peak causes
LH surge
Estrogen
Progesterone
Estrogen level
very low
Progesterone and estro-
gen promote thickening
of endometrium
Uterine (menstrual) cycle
Endometrium
Menstrual flow phase
Proliferative phase
Secretory phase
Days 5 10 14 15 20 25 28

11. Ovarian Cycle – This is occurring at the same time as the menstrual cycle.
GnRH released by the hypothalamus travels to the anterior pituitary gland.
The Anterior Pituitary gland releases FSH (AND LH) to travel to the ovaries to stimulate several follicles to begin to mature.
Follicular Phase (Days 1 -13) – Follicle and egg mature and release estrogen. It travels to the uterus to stimulate proliferation of the endometrium in the uterus.
Ovulation – The release of the egg to the fallopian tubes occurs (STIMULATED BY LH). It travels toward the uterus and possible sperm.
Luteal Phase (Days ) – Corpus luteum (empty follicle) produces progesterone and estrogen. MAKE CHANGE HERE
When the corpus luteum is “gone”, that causes the Hypothalamus to detect no progesterone; and releases GnRH to start the next cycle.
A fetus mimics a corpus luteum until HGH can take over to prevent next cycle.

13. Female Reproductive Cycle in Humans
Control by hypothalamus
Inhibited by combination of
estrogen and progesterone
Hypothalamus
Stimulated by high levels
of estrogen
GnRH
Anterior pituitary
Inhibited by low levels of
estrogen
FSH LH
Pituitary gonadotropins
in blood
Changes in the uterus coincide with changes in the ovaries. LH
FSH
FSH and LH stimulate
follicle to grow
LH surge triggers
ovulation
Ovarian cycle
Corpus
luteum
Degenerating
corpus luteum
Growing follicle
Mature
follicle
Follicular phase
Ovulation
Luteal phase
Estrogen secreted
by growing follicle in
increasing amounts
Progesterone and
estrogen secreted
by corpus luteum
Ovarian hormones
in blood
Peak causes
LH surge
Estrogen
Progesterone
Estrogen level
very low
Progesterone and estro-
gen promote thickening
of endometrium
Uterine (menstrual) cycle
Endometrium
Menstrual flow phase
Proliferative phase
Secretory phase
Days 5 10 14 15 20 25 28

15. The Female Human Menstrual Cycle
Days 1 – 5 - This is the menstrual flow phase. There is shedding of the old endometrium because pregnancy didn’t occur.
Days 5 – 13 - This is the proliferative phase. Estrogen causes a new endometrium to be built back up. (Fetal cushion)
Day 14 – This usually is the day ovulation (release of the egg) occurs.
Days 14 – 25 - This is the secretory phase. Progesterone causes the new endometrium to secrete a sugary substance.
This sugar will serve to feed the developing fetus until an umbilical cord develops.
Days 25 – 28 – This is the endometrial breakdown phase – if no pregnancy has occurred. Breakdown tissues for menses.
When menses begins, that marks day one of a new cycle beginning.

17. VI. Menopause – No more GnRH released
VI. Menopause – No more GnRH released. No more menstrual cycles – no more possible pregnancies. Occurs at 40 – 50 years old.

18. Fertilization and Implantation if pregnancy occurs
Cleavage starts
Cleavage continues
Ovary
Fertilization occurs
The blastocyst implants
Uterus
Ovulation
Endometrium
From ovulation to implantation