Reproductive System Physiology 2 - Teel

Question 1

Interaction of Theca and Granulosa Cells

What receptors are on these cells?

Answer 1

Theca: LH and LDL
Granulosa: LH and LDL and FSH

LDL is used because cholesterol is being utilized as a precursor.

Question 2

Interaction of Theca and Granulosa Cells

Answer 2

Theca cell: Cholesterol -> Pregnenolone -> Progesterone -> Androgens.

Androgens can then go to Granulosa cells to be converted into Estrogens.

Granulosa Cell: Cholesterol -> Pregnenolone -> Progesterone

Also can do:
Androgens -> Estrogens

Progesterone can then go to Theca cells to be converted into Androgens.

Question 3

Ovarian Cycle: Follicular Phase

Entire cycle

Answer 3

Follicular phase stimulated by FSH, LH, estrogens

Mitosis of germ cells -> primary oocytes which arrest prior to first meiotic division. Oocytes surrounded by pregranulosa cells which make up the primordial follicles.

1.) FSH stimulates selection of dominant follicle from the primordial follicles
2.) Dominant follicle transitions into graafian follicle with a fluid-filled antrum
3.) Dominant follicle produces estradiol, causes LH. LH causes oocyte to undergo meiosis.
4.) Secondary oocyte breaks free and floats in antrum.
5.) LH, FSH, progesterone weaken follicular wall.
Pressure of the fluid inside cause oocyte to be expelled. This fluid from antrum creates pressure, leading to rupture of follicle. Ovum expelled out.

Question 4

Ovarian Cycle: Luteal Phase

Answer 4

After ovulation, LH stimulates theca cells and granulosa cells to differentiate into hormone secreting cells.

Corpus luteum secretes both estrogens and progestins.

Question 5

Assuming 28 day cycle: When is ovulation?

Answer 5

Day 14

Question 6

Pre-Ovulation:

Answer 6

around Day 12-13.
Follicular phase

Rise of Estrogen, Influences LH to rise, FSH rises too.

Question 7

Post-Ovulation:

Answer 7

After Day 14. Rapid decline of estrogen, LH, FSH.
Luteal Phase

Corpus luteum secretes Progesterone / Estradiol (estrogen).
Note*: Pre-ovulation: estrogen is from mature follicle. Post-ovulation: estrogen is from corpus luteum.

Question 8

Endometrial Cycle (changes in uterus)

Menstrual phase (Menses)

Answer 8

Occurs during Follicular Phase

First 4 days of cycle.

Decline of hormones from previous cycle causes endometrial tissue to start undergoing necrosis. Decreased estrogen / progesterone result in breakdown of endometrial tissue -> sloughing and bleeding. (Period)

Question 9

Endometrial Cycle (changes in uterus)

Proliferative Phase

Answer 9

Occurs during Follicular Phase

Developing follicles which are producing estrogens stimulate proliferation of the endometrial. (Thickness of endometrium increases)
Estrogens stimulate secretion of GFs / synthesis of progestin receptors which exert an anti-estrogen effect (negative feedback)

Question 10

Endometrial Cycle (changes in uterus)

Secretory Phase

Answer 10

Occurs during Luteal phase

Progestins inhibit estrogen stimulated proliferation of endometrium.
Progestins stimulate glands producing glycogen.
Events occurring to prepare for pregnancy occur. Vascularization is increased, etc.

Question 11

Capacitation

How to activate sperm

Answer 11

Sperm initially released are incapable of fertilizing an ovum. Secretion of female reproductive tract activate the sperm.

Activation of sperm includes:
Washing away inhibitory factors present in semen
Loss of cholesterol material that modifies the acrosome which favors release of enzymes essential to fertilization.
Increased permeability of sperm membranes to Ca2+ -> favors release of acrosomal enzymes essential to fertilization.

Question 12

Midterm question:

Multistep process of Fertilization

Answer 12

1.)Zona Pellucida of oocyte has little protein molecules known as ZP3. Sperm head have receptors for this glycoprotein ZP3.
2.)Acrosomal reaction: certain hydrolytic enzymes released from head of sperm to aid in entrance.
3.)Membranes of sperm / oocyte fuse.
4.)Increase in Ca2+ in oocyte triggers 2nd meiotic division and causes cortical reaction which prevents polyspermy.
5.) Male and female pronuclei fuse producing a zygote with equal numbers of maternal / paternal chromosomes and either XX / XY chromosomes.

Question 13

Difference between X and Y bearing sperm

Answer 13

Y bearing sperm has a smaller payload, so it can swim faster. However it has a shorter lifespan.

Question 14

Events of Fertilization

Midterm question

Answer 14

1.) Sperm cell weaves past follicular cells and binds to zona pellucida of oocyte
2.) Acrosomal reaction occurs, rise in Ca2+ cause exocytosis of acrosome. Releases hydrolytic enzymes into zona pellucida
3.) Enzymes locally dissolve in zona pellucida. Sperm pushes towards oocyte membrane
4.) 2 Membranes fuse. Sperm empties contents into oocyte.
5.) Rise in Ca2+ inside oocyte triggers cortical reaction. Zona pellucida hardens preventing polyspermy.
6.) Rise in Ca2+ induces completion of oocyte’s second meiotic division and formation of 2nd polar body. This lies next to first polar body
7.) Head of sperm enlarges. Becomes male pronucleus
8.) Male / female pronuclei fuse.

Question 15

What causes Down Syndrome?

Answer 15

3 21 chromosomes

Question 16

Contraception

Answer 16

Avoiding intercourse 4 days prior and 3 days following ovulation = 25% failure rate
Condoms prevent STDs, significant failure rate
Pill: administers estrogen / progestins. This inhibits LH and FSH from ant. Pit.
“morning after” pill: strong progestin molecules that block LH.

Question 17

Implantation process

Why isn’t zygote rejected by mother?

Answer 17

Decidualization of endometrium (changes that favor implantation)
Why isn’t zygote rejected by mother? Little embryo can produce anti-rejection molecules.
Trophoblast cells secrete hCG which sustains corpus luteum.
Trophoblasts form syncytiotrophoblasts that invade endometrium

Question 18

Physiology of the Placenta:

Answer 18

Special cells that invade blood supply thats coming to the uterus.
Contains hormones
Gases / solutes move between mother / fetus. Transport via simple diffusion, facilitated diffusion, active transport, endocytosis

Question 19

Problem of placenta:

Answer 19

Can’t make enough cholesterol, but it has enzymes capable of producing estrogens.
Mother needs estrogen, can’t make all by herself.

Question 20

Maternal-Placental-Fetal Unit

Summary

Answer 20

Mother supplies cholesterol. Mother needs progesterone / Estrogen, and cholesterol synthesizes this in placenta.
Placenta converts cholesterol from mom ->pregnenolone -> progesterone

Also does DHEAS -> estriol.

Fetal adrenals / liver supply enzymes that placenta lacks.
Fetal adrenals convert pregnenolone to dehydroepiandrosterone sulfate (DHEAS)
DHEAS hydroxylated by fetal liver. Then travels to placenta for conversion to estriol.

Question 21

Maternal-Placental-Fetal Unit

Mother pathway

Answer 21

Acetate -> cholesterol

Takes progesterone / Estrogens from placenta

Question 22

Maternal-Placental-Fetal Unit

Placenta Pathway

Answer 22

Cholesterol -> Pregnenolone -> progesterone

DHEA -> Estrogens via sulfatase / aromatase

Takes DHEAS from Fetus
Takes Cholesterol from Mother

Question 23

Maternal-Placental-Fetal Unit

Fetus pathway

Answer 23

Pregnenolone -> DHEAS

Takes Pregnenolone from Placenta

Gives DHEAS back into Placenta

Question 24

Maternal Responses to Pregnancy

Question 25

Hormone secretion rates during pregnancy:

Answer 25

10 weeks after pregnancy: HCG large spike
After 10 weeks: HPL, Progesterone, Estriol, steady rise until 40 weeks.

Question 26

Parturition (birth process)

Answer 26

Certain hormones (estrogen) tend to trigger uterine contractions. Progesterone inhibits this kind of activity.
Oxytocin stimulates uterine contractions
Prostaglandins enhance uterine contractility.

Positive Feedback

Question 27

Fetal responses to Parturition

Answer 27

Vascular resistance increases systemically and left ventricular pressure goes up too. Pulmonary vascular resistance decreases.

Right side of heart becomes low pressure system, left side becomes high pressure system.

Foramen ovale closes due to pressure switch

Increased portal venous pressure

Question 28

Circulation in fetus changes

Skim through this slide

Answer 28

Doesn’t need umbilical arteries / veins anymore
connection between pulmonary artery / aorta gone
tons of changes

Question 29

Mechanics of Breathing in the newborn

Answer 29

First breath is a very long loop of huge pressure change, eventually assumes a different pressure volume loop.
First few minutes are very critical.
Volume of breath does not change, but pressure does dramatically between first couple breaths. Big pressure change in first breath, diminishing by 3rd.

Question 30

Physiology of Lactation

Key point here

Answer 30

Key point: Oxytocin which is synthesized from hypothalamus, stored in post. pit. Function is to release milk, not produce it.

Question 31

Lactation process

Answer 31

Stimulus: suckling from fetus
2.) Neurons from spinal cord inhibit dopamine. Decreased Dopamine allows lactotrophs in ant. pit. to release prolactin, stimulating milk production.
3.) Neurons from spinal cord also stimulate release of oxytocin from paraventricular / supraoptic nuclei (post. pit) into systemic blood. Makes way to breast.
4.)Neurons from spinal cord inhibit neurons in arcuate nucleus and preoptic area of hypothalamus, causing fall of GnRH production. Reduced gonadotroph activity inhibit ovarian cycle.

4.) is extra

Question 32

Effects of suckling and neural and hormonal responses in the female

Answer 32

Stress can inhibit milk production
Dopamine is an inhibitor

Question 33

Prolactin synthesis mechanism

Answer 33

good Sleep / no Stress / Suckling Stimulus affect Hypothalamus -> no dopamine -> Anterior Pituitary Lactotropes -> Prolactin.

Prolactin has negative feedback on dopamine

Question 34

Oxytocin synthesis mechanism

Answer 34

Suckling Stimulus affects Spinal chord
Emotions / Spinal chord / Sensory input -> Hypothalamus -> Posterior Pituitary -> Oxytocin

Question 35

Menopause

Answer 35

Increase of FSH, due to deficiency of estrogen. We lose the feedback.

Loss of ovarian follicles cause decline in estrogens / progestins. As a result, negative feedback effect on hypothalamus and ant. pit. removed.

Question 36

Menopausal syndrome

Answer 36

Loss of libido
headaches
hot flashes
night sweats
mood changes
etfc.

Question 37

Menopausal Fevers / hot flashes

Answer 37

Fevers: Hypothalamic set-point is turned up. Body thus tries to lose heat, aka vasodilation and sweating

Hot flashes: Hypothalamic set-point turned down. Decrease in body temp. Basically fever in reverse.
Vasoconstriction / shivering.