Reproductive System

What are the Key Stages of Fertilization

• Corona radiata penetration

  • Corona radiata is outer layer of cells

  • Sperm releases enzymes to break down corona radiata

• Zona pellucida penetration

  • Layer outside of plasma membrane

  • Sperm releases several enzymes to break down zona pellucida (acrosomal reaction)

• Fusion of pronuclei

  • Joining of the egg and sperm cell nuclei

  • Combines genetic material

What is hCG? What does it do?

·       hCG is a hormone only released by women and helps get pregnancy going

·       Maintains corpus luteum

·       Allows for continue release of progesterone and estrogen

·       Results in the maintenances of the uterine lining

·       Also prevents menstruation and stimulates placental development

What is progesterone’s functions during pregnancy?

·       Concentrations will be high until parturition

·       Maintenance of the uterine lining

·       Prevents premature uterine contractions during pregnancy

·       Supports placental formation

·       Stimulates development of milk glands

o   Glands produce milk

·       Prevents lactation during pregnancy

·       Concentration drops after delivery of placenta

What are estrogen’s functions during pregnancy?

·       Stimulates the start of uterine growth

·       Increases placental blood flow

·       Stimulates development of milk ducts

o   Milk ducts transport milk

·       Stimulates fetal development

·       Concentrations will be high until parturition

o   High concentrations increase uterine sensitivity to oxytocin

·       Concentration drops after delivery of placenta

What is the function of the placenta?

·       Exchange site between fetus and mother

o   Nutrients

o   Waste

o   Gases

o   Antibodies

·       Releases hormones

o   hCG

o   Progesterone

o   Estrogen

·       Barrier – to keep fetus safe

o   Physical

o   Immune

What is umbilical circulation?

o   Fetal blood enters the placenta via the umbilical artery, while maternal blood comes from the uterine artery

o   Blood in the uterine artery is oxygenated

o   Blood in the umbilical artery is deoxygenated, and this blood goes to the placenta to pick up oxygen

What is the goal of pregnancy in the reproductive system? How does it do this?

·       Goal: Maintain pregnancy and inhibit ovarian and uterine cycles

·       Increased breast size (estrogen) and development of milk glands (progesterone)

·       Increased uterine growth

·       Development of cervical plug to prevent infection

·       Progesterone and estrogen inhibit GnRH, preventing ovulation during pregnancy

What is the goal of pregnancy in the endocrine system? How does it do this?

·       Goal: Maintain pregnancy and inhibit menstrual cycle

·       Increased progesterone, estrogen, and hCG

o   Supports pregnancy

·       Reduced GnRH, FSH, LH

o   Inhibition of menstrual/uterine cycle

What is the goal of pregnancy in the cardiovascular system? How does it do this?

·       Goal: Deliver oxygen, nutrients, and remove waste from the fetus

·       Increased plasma volume

·       Estrogen indirectly increases cardiac output

o   Indirectly causes vasodilation (decreased resistance)

o   Increases blood volume by stimulating RAAS and increasing plasma protein production

·       Progesterone decreases TPR via vasodilation

·       Decreased MAP during the 1^st and 2^nd trimesters

o   Decreased TPR —> increased cardiac output

What is the goal of pregnancy in the respiratory system? How does it do this?

·       Goal: Provide oxygen and remove carbon dioxide from the fetus

·       Progesterone increases V(t) and V(E)

·       Leads to respiratory alkalosis

o   Leads to metabolic compensation

·       Lung volumes altered due to growing fetus

How does the urinary system function during pregnancy?

·       Progesterone causes vasodilation

·       Increases GFR

·       Urinary output increases due to –

o   Increased GFR

o   Metabolic compensation

·       Urinary frequency increases due to-

o   Fetus compressing bladder

What is the goal of pregnancy in the digestive system? How does it do this?

·       Goal: Provide nutrients to fetus

·       Motility reduced by progesterone and compression of stomach and intestines

·       Reduced motility causes constipation

o Allows for greater water and nutrient absorption

How does the nervous system function during pregnancy?

·       PNS activity increases during the 1^st trimester (maintain pregnancy)

o   Increases digestive function

o   Promotes vasodilation

o   Relaxes smooth muscle

·       SNS activity increases during the 3^rd trimester (prepare for labor and delivery)

o   Better distribution of blood flow

o   Increases metabolic rate

o   Activation of RAAS (Regulation of MAP and water balance)

o   Stimulates uterine contractions

What does parturition mean?

·       Parturition = the process of giving birth

What are the key hormonal shifts that are sensed by the uterus to initiate labor?

o   Decreased Progesterone leads to decreased uterine relaxation

o   ­Increased Estrogen increases uterine sensitivity to oxytocin

o   Fetal cortisol surge increases placental estrogen production

What type of feedback is labor? How does this loop work?

Labor = positive feedback loop

·       Oxytocin binds to uterine receptors —> uterine contractions

·       Contractions stretch cervix & fetal membranes —> prostaglandin release

·       Prostaglandins amplify uterine contractility —> more oxytocin release

·       Mechanical stretch of the cervix augments oxytocin release

What are the lactation hormones? What are each hormones function in relation to lactation?

·       Progesterone

o   Stimulates milk glands (milk factories)

o   Inhibits release of prolactin

o  Progesterone concentration decreases after delivery, which allows for prolactin release

·       Estrogen

o   Stimulates development of milk ducts (milk trucks and highways)

o   Stimulates secretion of prolactin

·       Prolactin stimulates milk production (turn factories on)

o   Stimulated by estrogen and sucking baby

·       Oxytocin stimulates let-down (delivery of milk)

o   Oxytocin also causes uterine contraction

·       Crying baby and/or a suckling child cause the release of both hormones

What is oogenesis?

o   Production of female gametes/egg cells

What is Folliculogenesis?

o   Growth and development of ovarian follicles/mature egg cells

o   The development of the house where the egg will mature

o   Follicles are structures made of specialized cells that surround the oocyte (egg cell). These cells nourish the oocyte as well as produce hormones.

What are the stages of Folliculogenesis?

·      Resting follicle

o   Most common type

o   Pool of follicles present before puberty

·      Primary follicles

o   Resting follicle that has undergone the initial stages of development

·      Cells within follicle divide to form secondary follicle

·      Oocyte within follicle releases fluid (antrum) and follicle becomes a tertiary follicle

o   Most die

·      Tertiary follicles that mature fully will rupture to release oocyte

·      Remaining cells in follicle form corpus luteum

o   Produces progesterone

What are the two stages of the ovarian cycle?

1. Follicular Phase

2. Luteal Phase

What is the Follicular Phase of the Ovarian Cycle?

The first stage:

o   Follicular Phase (days 1-14)

o Follicle develops, ultimately leading to rupture

o  Increase in estrogen

o  Ends with ovulation

What happens in the Luteal Phase of the Ovarian Cycle (brief)?

o   Luteal Phase (days 15-28)

o  Corpus luteum takes over

o  Increase in progesterone and inhibin (inhibits the release of another egg)

What is the pathway to ovulation (Follicular Phase more in-depth)?

·      GnRH released from hypothalamus

o   Stimulates release of FSH and LH from anterior pituitary

·      FSH and LH stimulate the follicle

o   FSH causes release of inhibin which inhibits release of FSH

o  #NegativeFeedback

o   LH stimulates release of estrogen

·      At the end of the follicular phase there are high concentrations of estrogen

·      High estrogen causes a surge in LH

·      This triggers ovulation - egg ruptures from the ovaries into the tubes

What happens in the Luteal Phase of the Ovarian Cycle (in-depth)?

·      Ruptured follicles turn into corpus luteum

·      Corpus luteum secretes progesterone and estrogen

o   Helps prepare the uterus for possible implantation (esp progesterone helps with implantation)

o   Provides negative feedback on hypothalamus which reduces release of GnRH

o   Corpus luteum also releases inhibin

o  Prevents release of FSH

·      If fertilization/implantation does not occur the corpus luteum degrades

·      Progesterone and estrogen decrease which leads to menstruation

What are the 3 phases of the Uterine Cycle?

1. Menstrual Phase

2. Proliferative Phase

3. Secretory Phase

What occurs during the Menstrual Phase?

·      Start a new reproductive cycle

·      Occurs in conjugation with the ovarian cycle

o   Menstrual phase occurs during the first half of the follicular phase

·      Menstrual phase begins on the 1^st day of menstruation and generally lasts for 5 days

o   Uterus sheds its inner lining of soft tissue and blood vessels Blood loss of 10 ml to 80 ml is considered normal

o   Abdominal cramps

·      Due to low levels of estrogen and progesterone

What occurs during the Proliferative Phase?

·      Starts when menstrual phase ends

·      Proliferative phase occurs during the second half of the follicular phase

·      Endometrium grows back and becomes

o   Thicker

o   More vascularized (more blood vessels)

·      Occurs due to release of high levels of estrogen

·      Preparation for possible implantation

·      Days 6-14

What occurs during the Secretory Phase?

·      Secretory phase occurs during the luteal phase

·      Endometrium continues to prepare for possible implantation

o   Due to release of progesterone (primary) and estrogen (secondary) from corpus luteum

·      Increased blood support potential embryo

·      Endometrium starts to degrade towards the end of this phase

o   Due to reduced release of progesterone and estrogen from degrading corpus luteum

·      Days 15-28

What are the correlations between the uterine and ovarian cycles?

·      Menstrual phase occurs during the early follicular phase of the ovarian cycle

o   Progesterone and estrogen levels are low

·      Proliferative phase coincides with the mid to late follicular phase of the ovarian cycle

o   High levels of estrogen

·      Secretory phase corresponds with the luteal phase of the ovarian cycle

o   Driven by high levels of progesterone

o   There are also moderate levels of estrogen

o   Both are released from the corpus luteum

What event occurs in the Ovarian cycle that causes the Follicular phase to end and the Luteal phase to begin?

When the follicle is released from the ovaries into the fallopian tubes

What are parts of the female anatomy?

• Vulva

• Clitoris

• Vagina

• Labia

• Uterus

• Ovaries

• Uterine tubes (fallopian tubes)

What are the homologues structures between females and males?

• Ovaries and testes

  • Produce gametes

• Clitoris and penis

  • Have erectile tissue

  • involved in orgasm

• Labia majora and scrotum

  • Protect and support reproductive organs

What does FSH cause in both Males and Females?

• Males - spermatogenesis

• Females - Follicle development

What does LH cause in both Males and Females?

• Males - Production and release of testosterone from interstitial cells (cells of leydig)

• Females - Production of estrogen and ovulation

What are sustentacular (sertoli) cells?

These help nourish, support, and mature sperm

What cells have negative feedback on the hypothalamus in males? How?

• Sertoli cells are stimulated by FSH and then releases androgen and inhibin, in which inhibin inhibits the hypothalamus

• LH stimulates the leydig cells, which releases testosterone, and testosterone goes back and inhibits the hypothalamus

  • The androgens released by the sertoli cells can also lead to testosterone secretion

What are the parts of the male anatomy?

• Penis

• Testes

• Scrotum

• Epididymis

List the order in which sperm develops?

1. Spermatogonia (stem cell)

2. Spermatocytes

3. Spermatids (mature and last stage)