Developmental Biology and Female Reproduction

What is the definition of development in biology?

All changes that occur during the entire life cycle, including embryonic development and post-birth changes.

What is fertilization?

The process in which gametes (an egg and sperm) fuse to form a zygote.

What is the result of the fusion of a haploid egg and haploid sperm?

A diploid zygote (2n).

What are the major consequences of fertilization?

Restores diploid number (2n), often determines sex, and activates the egg to promote development.

What is the acrosomal reaction?

A change in sperm cells that allows them to penetrate the egg's tough outer layer.

What happens during the cortical reaction in fertilization?

A defense mechanism that prevents polyspermy by releasing enzymes that harden the zona pellucida.

What is the slow block to polyspermy?

Changes in the zona pellucida that harden it and alter sperm receptors to prevent further sperm binding.

What triggers the activation of the egg?

A wave of calcium ions released in the cytoplasm, initiating metabolic reactions and embryonic development.

What occurs during the completion of meiosis after fertilization?

The secondary oocyte resumes meiosis, completing it and generating a second polar body.

What is karyogamy?

The fusion of the sperm nucleus with the egg nucleus, resulting in a diploid zygote.

What is cleavage in embryonic development?

The rapid division of the zygote into a multicellular embryo without growth.

What are the three patterns of cleavage?

Equal holoblastic, unequal holoblastic, and meroblastic.

What characterizes equal holoblastic cleavage?

Complete division of the egg into equal-sized cells.

What characterizes unequal holoblastic cleavage?

Asymmetric cleavage due to varying yolk distribution, resulting in unequal cell sizes.

What is meroblastic cleavage?

Only regions without yolk divide completely, while yolk-rich regions do not.

Which organisms typically exhibit equal holoblastic cleavage?

Echinoderms, mammals, and annelids.

Which organisms typically exhibit unequal holoblastic cleavage?

Amphibians.

Which organisms typically exhibit meroblastic cleavage?

Birds, reptiles, many fishes, and insects.

What is the role of yolk in cleavage?

Yolk serves as food for the developing embryo and affects the pattern of cell division.

What is the blastula?

A hollow embryo stage containing at least 128 blastomeres.

What is gastrulation?

The process that follows cleavage, leading to the formation of the three germ layers.

What is the significance of the zona pellucida?

It acts as a barrier to interspecific fertilization and plays a role in sperm binding.

What is the first step in human fertilization?

The acrosomal reaction, where sperm penetrates the egg's protective layers.

What occurs after the sperm nucleus enters the egg?

The cortical reaction occurs, preventing additional sperm from entering.

What is the final outcome of fertilization?

The zygote undergoes its first division, marking the beginning of embryonic development.

What is the role of maternal enzymes during egg activation?

They are activated to support increased protein synthesis and metabolic reactions.

What is the function of the acrosome in sperm?

It contains enzymes that help the sperm penetrate the egg's zona pellucida.

What is polyspermy?

The fertilization of an egg by multiple sperm, which is prevented by the cortical reaction.

What are the main functions of the female reproductive system?

Produce ova, receive sperm, facilitate fertilization, house and nourish developing embryo, give birth, lactate and feed young.

What are the components of the female reproductive system?

Ovaries, oviducts (Fallopian tubes), uterus, cervix, vagina, vulva.

Where are the ovaries located?

In the abdominal cavity.

What hormones do the ovaries produce?

Estradiol and progesterone.

What is the function of the oviducts?

Collects oocyte from ovary, moves it to the uterus, and is the site of fertilization.

What are the two layers of the uterus?

Myometrium (thick wall of smooth muscle) and endometrium (lines the lumen).

What happens to the endometrium if fertilization does not occur?

It is sloughed off during menstruation.

What is the structure and function of the cervix?

The lower part of the uterus that closes the uterus and separates it from the vagina.

What is the role of the vagina?

Receives the penis and sperm, and serves as the birth canal.

What is oogenesis?

The process of egg (oocyte) development.

What occurs during oogenesis before birth?

Primordial germ cells undergo mitosis to form oogonia, which then develop into primary oocytes.

What is the significance of the primary oocyte?

It begins meiosis and arrests in prophase I until puberty.

What is the menstrual cycle?

A complex sequence of events that prepares the female body for pregnancy, repeating every 28 days unless pregnancy occurs.

What are the two overlapping parts of the menstrual cycle?

Ovarian cycle and uterine cycle.

What are the phases of the ovarian cycle?

Follicular phase (days 1-13), ovulation (day 14), luteal phase (days 15-28).

What are the phases of the uterine cycle?

Menstrual flow phase (days 1-5), proliferative phase (days 6-13), secretory phase (days 15-28).

What is the role of estrogen in female endocrinology?

Stimulates growth of sex organs and secondary sex characteristics, and prepares the endometrium for pregnancy.

What does progesterone do?

Completes preparation of the endometrium for pregnancy and stimulates endometrial glands to secrete nutrient-rich fluid.

What triggers ovulation?

A surge in luteinizing hormone (LH) caused by high levels of estradiol.

What happens during the early luteal phase?

LH stimulates the remaining follicle tissue to become corpus luteum, which secretes high levels of progesterone and estradiol.

What occurs if there is no pregnancy during the late luteal phase?

Low FSH and LH lead to the disintegration of the corpus luteum, stopping the secretion of estradiol and progesterone.

What happens during the proliferative phase of the uterine cycle?

Ovarian hormones stimulate the uterus to prepare for embryo support, and the endometrium thickens.

What occurs during the secretory phase of the uterine cycle?

Promoted by estradiol and progesterone, the endometrium completes preparation to support an embryo.

What initiates the menstrual phase?

The shedding of endometrial tissue, fluid, and blood if fertilization does not occur.

What are the primary functions of the female reproductive system?

Produce ova, receive sperm, facilitate fertilization, house and nourish developing embryo, give birth, and lactate.

What are the main components of the female reproductive anatomy?

Ovaries, oviducts (fallopian tubes), uterus, cervix, vagina, and external genitalia (vulva).

What is the role of the ovaries in the female reproductive system?

They produce gametes (ova) via oogenesis and secrete sex hormones like estradiol and progesterone.

What is the cervix and its significance?

The cervix closes the uterus and separates it from the vagina; it is a common site for cancer, often linked to HPV.

What is the function of the vagina?

It extends to the outside of the body, receives the penis and sperm, and serves as the birth canal.

What occurs during the first meiotic division of oogenesis?

The primary oocyte completes meiosis I, resulting in a secondary oocyte and a polar body.

What is the corpus luteum?

A temporary endocrine gland formed from the ruptured follicle after ovulation, secreting estrogens and progesterone.

What happens to the secondary oocyte if sperm enters?

It completes meiosis II, resulting in a mature egg.

What is the primary female sex hormone?

Estrogen, with estradiol being the main form.

What role does progesterone play in the menstrual cycle?

It completes the preparation of the endometrium for pregnancy and stimulates the secretion of nutrient-rich fluid by endometrial glands.

What hormones are secreted by the hypothalamus and anterior pituitary in the female reproductive system?

The hypothalamus secretes GnRH, while the anterior pituitary secretes FSH and LH.

What is the significance of the follicle cells in oogenesis?

They provide a protective barrier for the primary oocyte and secrete hormones that facilitate maturation.

What happens to the corpus luteum if fertilization does not occur?

It undergoes luteolysis and disintegrates, leading to menstruation.

How many primary oocytes are present at birth?

Approximately 1-2 million primary oocytes.

What is the process of menstruation?

The shedding of the endometrial lining when fertilization does not occur, typically lasting 3-7 days.

What is the role of the hypothalamus in female endocrinology?

It regulates the release of hormones that control the menstrual cycle and reproductive functions.

What initiates the menstrual cycle at puberty?

Hormonal changes that stimulate the growth of sex organs and secondary sex characteristics.

What are the four phases of the ovarian cycle?

Early Follicular Phase, Late Follicular Phase, Early Luteal Phase, Late Luteal Phase

What hormone does the hypothalamus secrete to initiate the ovarian cycle?

GnRH (Gonadotropin-Releasing Hormone)

Which glands are stimulated by GnRH from the hypothalamus?

Anterior Pituitary

What hormones are secreted by the anterior pituitary in response to GnRH?

FSH (Follicle-Stimulating Hormone) and LH (Luteinizing Hormone)

What is the role of FSH in the ovarian cycle?

Stimulates follicle growth

What triggers ovulation in the ovarian cycle?

LH surge

What is the function of the corpus luteum?

Secretes progesterone and estradiol

What happens to the corpus luteum if there is no pregnancy?

It disintegrates

What are the three phases of the uterine cycle?

Menstrual flow phase, Proliferative phase, Secretory phase

During which phase does the endometrium thicken?

Proliferative phase

What hormones promote the thickening of the endometrium?

Progesterone and estradiol

What occurs during the menstrual flow phase?

Endometrial tissue, fluid, and blood are shed

What day is typically associated with ovulation?

Day 14 of the menstrual cycle

What is the effect of high levels of estradiol on the hypothalamus?

Stimulates GnRH secretion

What is the role of progesterone in the uterine cycle?

Maintains the uterine lining for potential embryo implantation

What happens to hormone levels if pregnancy occurs?

Hormone levels remain elevated to support the pregnancy

What is the significance of the LH surge?

It triggers ovulation and the formation of the corpus luteum

What is the relationship between the ovarian and uterine cycles?

They are coordinated; ovarian hormones regulate the uterine lining

What is the typical duration of the menstrual cycle?

Approximately 28 days

What is the role of the hypothalamus in the menstrual cycle?

Regulates hormone release through GnRH

What triggers the start of a new ovarian cycle?

Low levels of estradiol and progesterone after corpus luteum disintegration

What is the effect of low FSH and LH levels?

They cause the corpus luteum to disintegrate

What happens to the endometrium if there is no pregnancy?

It breaks down and is shed during menstruation

What is the role of estradiol during the follicular phase?

Promotes follicle growth and thickening of the endometrium

What is the significance of the early follicular phase?

It marks the beginning of the ovarian cycle with follicle development

What hormone levels are low during the early follicular phase?

Estradiol and progesterone

What does the term 'negative feedback' refer to in the menstrual cycle?

High levels of estradiol and progesterone inhibit further GnRH release