Important Topic Of Biology: Menstrual Cycle

Definition:

The menstrual cycle is marked by a recurring monthly event (28 days with slight variability) in the form of menstrual flow (i.e. rupture of the uterine endometrium by bleeding).

Girls start menstruating (menstruation) on average, between the ages of 11 and 14. By this time, some sexual features have improved, and pubic hair and growing breasts. Menopause is a stage in a woman’s life cycle when ovulation and menstruation stop. Occurs between the ages of 45 and 50. It marks the end of a woman’s fertility.

A follicle with two layers of follicular cells is known as the primary follicle. These cells store hypertrophy and multiply to form more layers around the oocyte. Those cells eventually came to be recognized as ‘granulosa’ cells.

The two-layer follicles of the follicular cells are known as primary follicles, these follicles are formed during the embryonic stage and are the basic unit of the female reproductive system.

Stages of the menstrual cycle

The menstrual cycle includes cycles of the uterus and uterus. The ovarian cycle describes changes from the ovary follicles, while the uterine cycle describes changes in the endometrial lining of the uterus. Thus, there are 4 levels of the menstrual cycle:

• Menopause:
  It occurs for five days, during which the endometrium ruptures, menstruation begins. Cells of the endometrium, fluid, blood, and ovaries represent the flow of menstruation, and progesterone production decreases.
• Follicular Category:
  It lasts from the sixth to the thirteenth day. Endometrium rebuilds, FSH and LH secretion will increase which stimulates follicular growth in addition to estrogen release. It is also called the growth phase.
• Ovulatory Category:
  It occurs on the 14th day of the menstrual cycle. Both LH and FSH receive high levels. Ovulation occurs.
• Luteal Category:
  It occurs from the 15th day until the twenty-eighth day of the menstrual cycle. Corpus luteum produces progesterone. The endometrium becomes stronger and the uterine glands become secretive. Also called a secret category.

Hormonal in the menstrual cycle

The menstrual cycle is complex and is governed by the many hormones and hormones produced by those glands. The hypothalamus in the brain causes the nearby pituitary gland to release certain chemicals, which open the ovaries to produce the sex hormones estrogen and progesterone. Every part of the menstrual cycle is influenced by female hormones, especially estrogen, progesterone, FSH, and LH. Differences in the level of those hormones regulate the stages of the menstrual cycle.

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are produced in the form of the anterior pituitary. FSH stimulates the growth of ovarian follicles that produce estrogen. Progesterone is produced in the form of corpus luteum. FSH and LH will always grow during the follicular phase. They promote the development of follicles and the release of estrogen from them. Estrogen promotes the growth of the endometrium. Increased level of LH and FSH during the cycle. LH causes ovulation. After ovulation, the broken follicle grows into the corpus luteum, producing progesterone, thereby increasing the level of progesterone during the luteal phase. Progesterone is needed to preserve the endometrium for implantation. In the absence of fertilization, the corpus luteum decreases, and progesterone levels decrease, leading to endometrial rupture and menstrual flow.

• Embryonic Development
  In humans, the embryo develops about 4 days after fertilization. The development of the human embryo is also called embryogenesis. It is characterized by the processes of cell division and embryonic stem cells that occur during the early stages of growth. Embryogenesis occurs very early in the pregnancy, even before the baby is a true embryo.

Steps involved in embryogenesis

• Fertilization:
  The fusion of the sperm nucleus, of the father’s origin, with the egg nucleus of the mother’s origin, forms the main nucleus of the embryo. Fertilization in humans occurs at the ampullary-isthmic junction of the fallopian tube. The fluid of the female genital tract removes the covering of semen, especially those on the acrosome. These chemical compounds together are known as sperm lysin. Due to the acrosomal reaction, the plasma membrane of sperm joins the plasma membrane of the second oocyte so that the sperm contents enter the oocyte. Changes inside the oocyte membrane prevent access to additional sperm. Therefore, it ensures that the best sperm can fertilize the ovum. Sperm penetration involves the elimination of the meiotic separation of the second oocyte. The second meiotic phase is equally incompatible and leads to the formation of a second polar body and a haploid (ootid) ovum. Soon the haploid nucleus of sperm and the ovum come together to form the diploid zygote. The zygote divides to produce 2,4,6,8 female cells called blastoma cells.
• Blastocyst formation:
  Because the zygote separates, it forms a blastocyst or ball cell. An embryo with eighteen blastomeres is called a morula. In the next stage of growth, which produces the embryo with approximately sixty-four cells, an empty structure forms in the center of the cell mass. An empty space is called a blastocoel and an embryo is called a blastocyst. The outer envelope of the blastocyst is called the trophoblast or trophectoderm.
• Implantation:
  After the formation of the blastocyst, the trophoblast travels through the fallopian tube and attaches to the uterine wall during implantation. When the blastocyst attaches itself to the wall of the uterus, cells in the uterus begin to grow beyond the blastocyst, forming the amniotic cavity. Zona pellucida prevents the insertion of the blastocyst into the abnormal area.

The menstrual cycle is complex and is governed by the many hormones and hormones produced by those glands. The hypothalamus in the brain causes the nearby pituitary gland to release certain chemicals, which open the ovaries to produce the sex hormones estrogen and progesterone. Every part of the menstrual cycle is influenced by female hormones, especially estrogen, progesterone, FSH, and LH. Differences in the level of those hormones regulate the stages of the menstrual cycle.

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are produced in the form of the anterior pituitary. FSH stimulates the growth of ovarian follicles that produce estrogen. Progesterone is produced in the form of corpus luteum. FSH and LH will always grow during the follicular phase. They promote the development of follicles and the release of estrogen from them. Estrogen promotes the growth of the endometrium. Increased level of LH and FSH during the cycle. LH causes ovulation. After ovulation, the broken follicle grows into the corpus luteum, producing progesterone, thereby increasing the level of progesterone during the luteal phase. Progesterone is needed to preserve the endometrium for implantation. In the absence of fertilization, the corpus luteum decreases, and progesterone levels decrease, leading to endometrial rupture and menstrual flow.

• Embryonic Development
  In humans, the embryo develops about 4 days after fertilization. The development of the human embryo is also called embryogenesis. It is characterized by the processes of cell division and embryonic stem cells that occur during the early stages of growth. Embryosgenesis occurs very early in the pregnancy, even before the baby is a true embryo.

The menstrual cycle includes the follicular phase, ovulation, and luteal. After fertilization, the cleavage produces a blastocyst that attaches to the endometrium. Female reproductive cycles are regulated by hormones activated in the hypothalamus and anterior pituitary and hormones from the reproductive organs and organs. A woman’s pregnancy begins with an egg pregnancy and continues for 3 trimesters of pregnancy. The first trimester lays down the main systems of the body, including the organs of the body, heart, eyes, and liver. The 2nd trimester maintains the development of all organs and systems. The 3rd trimester is best known for displaying excellent fetal growth and ending with labor and transport. The exercise process consists of 3 stages (contraction, fetal transport, and placental abruption), each of which is performed with the help of hormones.

Also read: Male and Female Reproductive Systems

FAQs

When does LH surgery occur?

LH surgery occurs during maturation.

What happens if there is no fertilization?

Without fertilization, no zygote will form and the egg will deteriorate and fall off the uterine lining.

What is the function of trophoblast cells?

They help to impart nutrients to the embryos and later build up an extraembryonic membrane called amnion and chorion.

What are the different stages of fertilization?

The different stages of fertilization are: sperm infiltration, acrosomal reactions, cortical reactions, karyogamy.