CICLO MENSTRUAL - ciclo sexual femenino: Hormonal, ovárico y uterino| ¡Fácil explicación!

The Menstrual Cycle

In this video, Romina Hurtado explains the menstrual cycle and how hormones play a role in the process. She discusses the ovarian cycle and the uterine cycle, highlighting the importance of these cycles in facilitating pregnancy and menstruation.

The Menstrual Cycle

• The menstrual cycle refers to the regular changes that occur in the female reproductive system, primarily involving the ovaries and uterus.

• Its purpose is to produce female gametes (eggs) and prepare the uterus for potential pregnancy.

• The innermost layer of the uterus, called the endometrium, plays a crucial role in the menstrual cycle. It consists of two layers: a functional layer that sheds during menstruation and a basal layer that regenerates it.

• The menstrual cycle is a result of synchronization between two processes: the ovarian cycle and the uterine cycle.

• The ovarian cycle involves follicle development, ovulation (release of an egg), and hormone production by the ovaries.

• The uterine cycle involves changes in the endometrium as a response to ovarian activity.

Phases of the Menstrual Cycle

Ovarian Cycle

• The ovarian cycle consists of two phases: follicular phase and luteal phase.

• Follicular Phase:

• Begins with gonadotropin-releasing hormone (GnRH) release from the hypothalamus, stimulating follicle-stimulating hormone (FSH) secretion from the anterior pituitary gland.

• FSH acts on the ovaries, leading to follicle development.

• Luteal Phase:

• After ovulation occurs, a corpus luteum forms from remnants of ruptured follicles.

• Corpus luteum secretes progesterone and estrogen.

Uterine Cycle

• The uterine cycle consists of three phases: menstrual phase, proliferative phase, and secretory phase.

• Menstrual Phase:

• Shedding of the functional layer of the endometrium due to decreased hormone levels.

• Proliferative Phase:

• Regeneration of the endometrium under the influence of estrogen.

• Secretory Phase:

• Increased secretion and vascularization of the endometrium in response to progesterone.

Menarche and Menopause

• Menarche refers to a woman's first menstrual period, which typically occurs during puberty (around ages 9-15).

• After menarche, the menstrual cycle repeats monthly until menopause.

• Menopause marks the cessation of menstruation, usually occurring between ages 45-55. It is characterized by reduced ovarian activity and egg reserve.

Ovulation

• Ovulation is the process by which an ovary releases a mature egg each month.

• It occurs randomly in either ovary and does not alternate between them.

Synchronization of Cycles

• The ovarian cycle and uterine cycle occur simultaneously and are interconnected.

• They coordinate to facilitate the menstrual cycle's progression through different phases.

Timestamps have been associated with relevant bullet points as requested.

Early stages of follicle development

This section discusses the early stages of follicle development in the ovarian cycle. Follicles containing immature oocytes undergo maturation, leading to ovulation. The hormone follicle-stimulating hormone (FSH) stimulates the growth and development of primordial follicles.

Follicle maturation and FSH stimulation

• Primordial follicles in the ovaries are stimulated by FSH to grow and develop.

• FSH stimulates 15 to 20 primordial follicles initially.

• The dominant primordial follicle, with more FSH receptors, matures and becomes the one that will be ovulated.

Role of inhibin and estradiol in follicular development

In this section, we explore how inhibin and estradiol play a role in regulating follicular development. These substances inhibit further FSH secretion from the pituitary gland to prevent excessive stimulation of primordial follicles.

Inhibin and estradiol secretion

• The dominant primordial follicle secretes inhibin and estradiol upon receiving FSH stimulation.

• Inhibin inhibits the growth of other stimulated primordial follicles.

• Estradiol is also secreted by the dominant follice, which helps regulate FSH secretion from the pituitary gland.

Development of the dominant primordial follicle

This section focuses on how the dominant primordial follicle develops during its early phase. Changes occur in its morphology as it prepares for ovulation.

Morphological changes in the dominant primordial follicle

• The dominant primordial follicle is surrounded by a single layer of flat cells called granulosa cells.

• This follicle has the highest number of FSH receptors and is considered the dominant follicle.

• Upon receiving FSH stimulation, the dominant follicle starts secreting inhibin and estradiol.

Formation of zona pellucida and multiple layers of granulosa cells

In this section, we explore how the dominant primordial follicle continues to develop. The granulosa cells around the oocyte multiply, forming multiple layers. Additionally, stromal cells from the ovarian cortex contribute to the formation of theca cells.

Development of zona pellucida and granulosa cell layers

• The granulosa cells surrounding the oocyte start proliferating and form several layers of cuboidal cells.

• A zone called zona pellucida forms between these granulosa cells and the oocyte.

• Stromal cells from the ovarian cortex contribute to forming a layer called theca externa.

Formation of theca layers

This section focuses on how stromal cells in the ovarian cortex contribute to forming two distinct layers known as teca interna and teca externa. These layers play a role in hormone production.

Formation of teca interna and teca externa

• Stromal cells from the ovarian cortex migrate towards developing follicles.

• These stromal cells form two distinct layers known as teca interna and teca externa.

• Teca interna contains LH receptors, while teca externa provides structural support.

Changes in ovum during development

In this section, we discuss changes that occur within the ovum during its development. The ovum disperses organelles throughout its cytoplasm and forms vesicles containing proteases.

Changes in the ovum

• The ovum disperses organelles throughout its cytoplasm.

• Vesicles called proteasomes are formed within the ovum, which contain enzymes known as proteases.

• These proteases are released when the ovum is stimulated by a spermatozoon, preventing other sperm from fertilizing it.

Hormone synthesis in granulosa and theca cells

This section explores hormone synthesis in granulosa and theca cells. LH stimulates the synthesis of testosterone and androstenedione in teca interna cells, while granulosa cells synthesize aromatase enzyme to convert these hormones into estrogen.

Hormone synthesis in granulosa and theca cells

• LH stimulates teca interna cells to synthesize testosterone and androstenedione.

• Granulosa cells synthesize an enzyme called aromatase.

• Aromatase converts testosterone and androstenedione into estrogen, specifically 17-beta estradiol.

Conclusion

The transcript provides an overview of early follicle development, including FSH stimulation, inhibin secretion, morphological changes in dominant follicles, formation of zona pellucida and multiple layers of granulosa cells, development of teca layers, changes in the ovum during development, and hormone synthesis in granulosa and theca cells.

Follicle Development and Ovulation

This section discusses the development of follicles in the ovaries and the process of ovulation.

Follicle Maturation

• The primary multilaminar follicle transforms into a secondary follicle, which eventually forms a single antral cavity.

• The oocyte moves towards the periphery, surrounded by a layer of cuboidal cells called the corona radiata.

• The secondary follicle is also known as Graafian or mature follicle, which is ready for ovulation.

Menstrual Cycle Phases

• The follicular phase occurs simultaneously with the proliferative phase and menstrual phase of the uterine cycle.

• The proliferative phase involves the growth of the endometrium under the influence of estrogen produced by the dominant ovarian follicle.

• Both the follicular and proliferative phases occur from day 1 to day 13 of the menstrual cycle.

Ovulation Process

• On day 14, a surge in luteinizing hormone (LH) triggers ovulation.

• LH increases cyclic adenosine monophosphate (cAMP) within the follicle, leading to inflammation and rupture of its wall.

• Contraction of ovarian muscles and prostaglandins contribute to expelling the oocyte from the ovary.

Luteal Phase and Corpus Luteum Formation

This section explains what happens after ovulation during the luteal phase and how corpus luteum forms.

Luteal Phase Initiation

• After ovulation, blood fills up the remaining portion of the ruptured ovarian follicle, forming a corpus hemorrhagicum.

• Blood vessels around this structure supply nutrients to granulosa cells and theca cells.

• LH stimulates the transformation of mixed cells into luteal cells, forming the corpus luteum.

Corpus Luteum Function

• The corpus luteum secretes progesterone and estrogen, which prepare the endometrium for potential implantation.

• The luteal phase lasts from day 14 to day 28 of the menstrual cycle.

• If fertilization occurs, the corpus luteum continues its function for approximately three months of pregnancy.

Effects of Progesterone and Estrogen

This section discusses the effects of progesterone and estrogen during the luteal phase.

Endometrial Changes

• Progesterone and estrogen cause further thickening of the endometrium and increased glandular secretion.

• These hormonal changes create an ideal environment for embryo implantation if fertilization occurs.

Mammary Gland Changes

• Progesterone also affects mammary glands, causing them to enlarge due to increased glandular tissue growth.

Degeneration of Corpus Luteum

This section explains what happens if fertilization does not occur and how the corpus luteum degenerates.

Corpus Luteum Regression

• If fertilization does not occur, the corpus luteum degenerates approximately 10 to 12 days after ovulation.

• It transforms into a white scar-like structure called a corpus albicans.

• Progesterone levels decrease as a result.

Menstruation and the Menstrual Cycle

This section discusses menstruation and its relationship to the menstrual cycle. It explains the shedding of the functional layer of the endometrium during menstruation, the duration and amount of blood loss, and the role of progesterone in initiating menstruation.

Menstruation during the Menstrual Phase (0:21:59 - 0:22:21)

• Menstruation corresponds to day 1 of the menstrual cycle.

• The shedding of the functional layer of the endometrium occurs during this phase, accompanied by a small amount of bleeding.

• Menstruation typically lasts for 2 to 7 days with an average blood loss of around 35 mL.

Pain and Inflammation during Menstruation (0:22:44 - 0:23:27)

• Some abdominal, back, and thigh pain is common during the early days of menstruation.

• Severe or incapacitating pain is known as dysmenorrhea.

• Dysmenorrhea is caused by a decrease in progesterone levels, leading to an inflammatory process triggered by prostaglandins.

• Prostaglandins cause abdominal pain due to inflammation resulting from tissue loss during menstruation.

Summary (0:23:45 - 0:25:08)

• The video provides an overview of various aspects related to ovulation, uterine cycles, changes in basal temperature, and menstrual phases.

• The follicular phase marks the beginning of follicle development and expulsion of unfertilized oocytes.

• After expelling unfertilized oocytes, regeneration of lost endometrial tissue occurs as ovarian follicles continue maturing.

• Ovulation triggers a shift into the luteal phase when the uterine endometrium secretes mucus to create an ideal environment for potential fertilization.

• If fertilization does not occur, the unfertilized oocyte is expelled through menstruation, accompanied by the shedding of the functional layer of the endometrium.

The video concludes with a call to action to like, subscribe, and share on social media.