BME 419 - Reproduction

Gametogenesis and steroidgenesis

Gonads serve a dual function:

1. Gonadotropin-releasing hormone (GnRH)

2. Follicle-stimulating hormone (FSH) & Luteinizing hormone (LH)

3. sex hormones - estrogen, testosterone, and progesterone

Hormones involved in the regulation of the reproductive system

Gonadotropin-releasing hormone (GnRH)

Hormone that stimulates the anterior pituitary to release FSH and LH

Follicle-stimulating hormone (FSH) & Luteinizing hormone (LH)

Hormones released by the anterior pituitary gland in response to GnRH. They regulate the function of the gonads (ovaries in females, testes in males).

Peptide and steroid

Two kinds of hormones classes mediate intercellular communication in the reproductive hormone axis:

Negative

Sex hormones have a ___________ feedback relationship on the hypothalamus to release GnRH

Becuase the hormones are secreted into the portal blood vessels

Why does it take only very small quantities of hypophysiotropic hormones to regulate anterior pituitary gland hormone secretion?

46, 23

Each nucleated human cell contains __ chromosomes, or __ pairs of homologous chromosomes.

Germ cells give rise to gametes and contribute to genetic diversity, while somatic cells make up the body and do not participate in reproduction.

What is the difference between germ cells and somatic cells?

In females - in utero

In males - starting at puberty and throughout life

When does mitosis of germ cells occur in females/males?

Start: One Spermatogonium with 46 chromosomes.

End: Four sperm cells, each with 23 chromosomes—genetically unique from each other and the original germ cell.

What do you start and end with in male gametogenesis?

Start: One primary oocyte (diploid, 46 chromosomes).

End:

One mature egg (ovum) (haploid, 23 chromosomes).

Three polar bodies (haploid, non-functional).(All four daughter cells are genetically unique, but only the egg is viable for fertilization.)

and end with in female gametogenesis?

Crossing over

During meiosis, the exchange of genetic material between homologous chromosomes.

SRY gene

The presenece of the _____ gene on the Y chromosome will cause differentiation of the gonads into testes

X and Y chromosomes

The gender is determined by the sex chromosomes: ___________. The genes directly determine whether the individual will have testes or ovaries.

Sertoli cells

Leydig cells

What cells support developing sperm, and what cells produce testosterone?

Müllerian-inhibiting substance (MIS)

What hormone is released by sertoli cells

Testosterone

What hormone is released by Leydig cells?

Seminiferous tubule

Functional unit of the testes. Where spermatogenesis occurs

seminiferous tubules > efferent ductules in the epididymus >> vas deferens > vas deferens + seminal vesicles = ejaculatory ducts >> prostate > urethra

The sperm route (start at seminiferous tubules)

Fluid: 1. nutrients 2. buffers 3. chemicals 4. prostaglandins

What composes the fluid in semen (combines with sperm to make semen)

Seminal vesicles

1. Which of the following male accessory reproductive organs secretes prostaglandins?(1) prostate gland(2) seminal vesicles(3) epididymis(4) bulbourethral glands(5) vas deferens

Undifferentiated germ cells

Spermatogenesis starts with mitosis of ______________

Spermatogonia moving between tight junction and exposing it to signals from sertoli cells

What happens to a spermatogonia stem cells to make it commit to cell division

Differentiation

Final phase of spermatogenesis

Head, midpiece, flagellum (tail)

The structure of a sperm cell has 3 different parts

Acrosome

Protein filled vesicle in sperm that carries hydrolytic enzymes that help the sperm penetrate the outer layers of the egg

(3) requires participation of Sertoli cells

The process of spermatogenesis from primary spermatocyte to sperm: (1) takes about three weeks in the human. (2) occurs when a male is an embryo, ceasing at birth. (3) requires participation of Sertoli cells. (4) occurs in the epididymis. (5) occurs as the cells gradually travel between two closely attachedLeydig cells.

(4) Sperm entering the epididymis are fully motile

Which of the following statements regarding male reproductive function is FALSE? (1) Sperm formed in the testes enter the epididymis before enteringthe vas deferens. (2) The seminal fluid is alkaline and rich in nutrients. (3) The Sertoli cells produce androgen-binding protein.(4) Sperm entering the epididymis are fully motile. (5) Most of the seminal volume is provided by the secretions of the seminal vesicles and prostate gland

- two ovaries

- reproductive tract:

- fallopian tubes

- uterus

- cervix

- vagina

The female reproductive system includes:

- oogenesis

- oocyte maturation

- ovulation

- hormone production

Functions of ovaries (4):

oogenesis

fertilization

Production of haploid gametes in females is called ________. The full sequence of meiosis is not completed until ___________

A) Cell division of primary oogonia results in the production of 2 to 4 million primary oocytes, which are present at birth.

1. During in utero (fetal) development of the ovary, which of these occurs?

A) Cell division of primary oogonia results in the production of 2 to 4 million primary oocytes, which are present at birth.

B) Cell division of primary oogonia, which all complete the first meiotic division before birth.

C) Cell division of primary oogonia, which all complete both meiotic divisions before birth.

D) The mitotic division of primary and secondary oocytes produces cells with 23 chromosomes each.

E) A single primary oogonium remains dormant, which then undergoes rapid mitosis after birth

D) Carry ova from the ovaries to the uterus.

2. The fallopian tubes:

A) Connect the uterus to the vagina.

B) Carry sperm from the testes to the epididymis.

C) Degenerate in females, due to the presence of Müllerian inhibiting substance.

D) Carry ova from the ovaries to the uterus.

E) Develop from the embryonic Wolffian duct system.

Ovarian follicle

The functional unit of the ovary

Oocyte surrounded by granulosa cells

What is the composition of a primordial follicle (start of folliculogenesis)

Fully grown oocyte surrounded by granulosa cells and early theca cells

What is the composition of a preantral follicle (third stage of folliculogenesis)

Antrum

Fluid filled space in follicle that is developed during the 3rd->4th stage of folliculogenesis

FSH - Granulosa cells

LH - Thetca cells

What cells in a ovarian follicle have receptors for FSH? LH?

Theca cells synthesize androgens

Granulosa cells convert androgens to estrogen

What do Theca cells (LH) and Granulosa cells (FSH) do?

Follicular phase

Luteal phase

The menstrual cycle is broken into 2 stages:

Steroid

Changes in ________ production drives the rest of the changes that characterize the menstrual cycle of adult women

Follicular phase

Menstrual cycle phase where the following events occur: uterine bleeding, follicle development, one follicle becomes dominant

Luteal phase

Menstrual cycle phase where the corpus luteum functions and then degenerates

follicular

luteal

ovulation

Menstrual cycle: The __________ phase is marked by increasing levels of estrogens whereas the ________ phase is one of increased progesterone levels; the transition between the two is ____________.

LH & FSH: Spike just before

Estrogen: increases before, peaks before and decreases after

Progesterone: continual increase

Describe what happens to the concentrations of LH, FSH, Estrogen, and Progesterone in between ovarian phases (ovulation)

Due to the decline in progesterone from the degeneration of the corpus luteum, which removes negative feedback on the pituitary

Why do plasma FSH concentrations increase at the end of the luteal phase?

Inhibin

During the follicular phase, _______ acts on the pituitary to inhibit the secretion of FSH

The feedback relationship between estrogen and pituitary gland secretion reverses in mid-cycle, eliciting a large, ovulatory surge in LH due to a positive feedback loop

Describe the feedback relationship between estrogen and the pituitary gland mid cycle

The first meiotic division of the oocyte completes and the dominant follicle ruptures.

Which of the following occurs at ovulation? 1. The first meiotic division of the oocyte completes and the dominant follicle ruptures. 2. The second meiotic division of the oocyte occurs. 3. The oocyte, along with its surrounding thecal layer, is expelled onto the ovarian surface. 4. The second meiotic division of the oocyte occurs and the dominant follicle ruptures. 5. The corpus luteum is expelled from the ovary and enters the fallopian tube.

Theca/Leydig

Granulosa/Sertoli

With respect to hormonal control and secretion, ______ cells in the ovary are analogous to ______ cells in the testis. (2 pairings)

4. Growing follicles produce estrogen, which further stimulates follicle maturation.

Which is TRUE about the maturation of ovarian follicles? 1. Granulosa cells produce androgens, which stimulates follicle maturation. 2.Theca cells produce estrogen, which is converted to the androgens that stimulate follicle maturation. 3.On day 1 of the cycle, growing follicles have both FSH and LH receptors on granulosa cells. 4.Growing follicles produce estrogen, which further stimulates follicle maturation. 5.Follicle maturation is stimulated when FSH binds to theca cells and LH binds to granulosa cells.

Fertilization

_____________ begins with the fusion of a sperm and egg

zona pellucida

The _______ _____________ glycoproteins function as receptors for sperm surface proteins

1. Membrane potential change2. Cortical reaction

2 Mechanisms to prevent polyspermy

C. Of the several hundred million sperm in an ejaculation, only about 100 to 200 reach the fallopian tube.

Which is TRUE about sperm delivery? A. Most of the ejaculated sperm arrive in the vicinity of the ovum (if there is one). B. Sperm transport through the cervix is made possible by actions of progesterone on the cervical mucus. C. Of the several hundred million sperm in an ejaculation, only about 100 to 200 reach the fallopian tube. D. Sperm are able to fertilize an egg from the instant they arrive in the female reproductive tract. E. Sperm can survive for up to 2 weeks in the mucus of the cervix.

C) Fertilization occurs in the Fallopian tube, and it takes about 4 days to reach the uterus.

Which is TRUE regarding fertilization and transport of an egg?

A) Fertilization occurs in the uterus, and must occur within 24-48 hours of ovulation.

B) Fertilization can occur any time within 7 days after ovulation, and it generally takes 10-14 days for the fertilized zygote to reach the uterus.

C) Fertilization occurs in the Fallopian tube, and it takes about 4 days to reach the uterus.

D) Fertilization must occur while the follicle is still attached to the ovary, and transport of the fertilized zygote to the uterus takes 24-48 hours.

E) Fertilization occurs in the Fallopian tube, and the zygote must reach the uterus within 24-48 hours to implant, or it will die

Implantation

The embedding of the blastocyst into the endometrium(7 days after ovulation /21st day of the cycle) .

B) It normally occurs midway through the luteal phase.

Which is a TRUE statement about implantation of a zygote?

A) When it occurs outside the uterus, it is called a myopic pregnancy.

B) It normally occurs midway through the luteal phase.

C) It is a result of digestion of myometrial cells by enzymes in the trophoblast.

D) It occurs at a time in the cycle when plasma estrogen concentration is higher than progesterone concentration.

E) It occurs at the same time as ovulation, and is caused by the LH surge.

Placenta

A combination of interlocking fetal and maternal tissues, which serves as the organ of exchange between mother and fetus for the remainder of the pregnancy.

Estrogen

Hormone that stimulates growth of uterine muscle

Progestrone

Hormone that prevents contraction

HCG: Peaks at 2 months, decreases to steady level

Estrogen/progesterone - increases, immediate drop at delivery

What happens to the following hormones during the span of pregnancy:

Human chorionic gonadotropin, estrogen, progesterone

C. hCG

The implanting blastocyst "rescues" the corpus luteum by secreting:

A. large quantities of FSH and LH

B. GnRH, which stimulates the pituitary gland to secrete FSH and LH

C. human chorionic gonadotropin

(hCG)

D. progesterone and estrogen

E. cortisol

Human chorionic gonadotropin (hCG)

Hormone produced by the placenta shortly after fertilization. Its main role is to support the early stages of pregnancy by signaling the ovaries to continue producing progesterone, which helps maintain the uterine lining. Hormone detected in pregnancy tests

1. feto-placental unit

2. "placental clock"

What initiates parturition? (2 things)

PUBERTY:

Estrogen - branching

Progesterone - growth

During puberty, what is the role of estrogen and progesterone in terms of breast development

PREGNANCY:

Prolactin - mother

Estrogen, progesterone and lactogen - placenta

During pregnancy, what 4 hormones contribute to breast development and where do they come from?

Prolactin

Estrogen

____________ is the major hormone stimulating milk production, but _________ prevents its action on the breasts.

B. the high levels of estrogen and progesterone in maternal plasma inhibit prolactin effects on the breasts

Lactation normally does not occur during pregnancy because

A. the breast ducts do not develop until after a baby is born

B. the high levels of estrogen and progesterone in maternal plasma inhibit prolactin effects on the breasts

C. maternal plasma levels of prolactin are low during pregnancy

D. high levels of androgens inhibit milk synthesis by the breasts

E. the low levels of circulating estrogen and progesterone during pregnancy inhibit milk synthesis by the breasts

E. stimulation of milk synthesis

Which of the following is NOT a function of estrogen during pregnancy?

A. stimulation of myometrial growth

B. maintenance of the endometrium

C. stimulation of prolactin secretion

D. stimulation of breast development

E. stimulation of milk synthesis

Fimbria cilia

Damage to the _________ ______ beating toward the uterus can cause infertility

1) Rhythm method

2) Steroid hormone contraceptive pill

3) Intrauterine device

Three reversible contraception methods

Rhythm Method

Intercourse only after ovulation until the end of menstrual flow