Menstrual Cycle Flashcards
Menstrual Cycle- about 28 days
The menstrual cycle is a series of changes the female body undergoes monthly, specifically in the uterus and ovaries, it prepares the egg/ovum for fertilization and implantation.
cycle is controlled by four hormones
Menstruation
Menstruation or period is the shedding of the uterus lining. Every month, a woman’s body is prepared for pregnancy, if fertilization and implantation do not occur the uterus lining sheds. The uterus lining is then discharged as blood.
Follicle
A follicle is a small sac that contains fluid and one developing egg cell. It is located in the ovaries.
Graafian Follicle
When the developing follicle bulges outside the ovary, it is called a graafian follicle.
Ovulation
The release of an ovum from an ovary
Ovary, Hormone Levels and Uterus Lining- Menstrual Cycle Days 1-7
Ovum matures inside a graafian follicle.
Oestrogen and progesterone levels are relatively low.
The uterus lining is thick.
Ovary, Hormone Levels, Uterus Lining Day 7-14
On day 14, ovulation occurs which is the release of ova from the ovaries
Oestrogen levels begin to increase, progesterone levels are still low.
Oestrogen stimulates the uterus lining to thicken
Ovary, Hormone Levels, Uterus Lining Day 14-21
The corpus luteum develops and secretes progesterone.
Oestrogen levels drop and progesterone levels greatly increase.
Progesterone stimulates the uterus lining to remain thick.
Ovary, Hormone Levels, Uterus Lining day 21-28
The corpus luteum degenerates.
Oestrogen and Progesterone levels decrease and remain low.
The uterus lining begins to deteriorate.
Hormones in the menstrual cycle: Follicle Stimulating Hormone
It is secreted by the pituitary gland at the beginning of the cycle.
- It stimulates a graafian follicle to develop in an ovary and an ovum to mature inside the follicle.
It stimulates the graafian follicle to produce oestrogen.
Oestrogen
Produced by the graafian follicle, mainly during the second week of the cycle.
- It stimulates the uterus lining to thicken and its blood supply to increase after mensturation.
- It causes the pituitary gland to stop secreting the FSH and INSTEAD TO SECRETE LH hormones.
Luteinising Hormone
Secreted by the pituitary gland in the middle to the cycle
- a sudden rise in LH causes ovulation to take place
- LH stimulates the corpus luteum to develop in the ovary and secrete progesterone
Simulates the corpus luteum to develop inside the ovaries.
Progesterone
produced by the corpus luteum and secreted by the ovaries during the third week of the cycle
- Causes the uterus lining increase slightly in thickness and to remain thick.
- If fertilization does not occur, the corpus luteum degenerates therefore reducing the secretion of progesterone. The decrease of progesterone causes the uterus lining to deteriorate, and the pituitary gland to secrete FSH at the end of the fourth week.
Human Reproduction
Human reproduction simplified is the bringing together of the male and female gamete. When a male becomes sexually excited, blood flows into their penis and it becomes erect and it is now able to penetrate the female’s vagina. Semen composed of sperm flows into the woman’s vagina and flows up into the cervix and uterus and into the oviducts. There it meets an ovum and it enters, leaving its tail outside. The fertilization membrane immediately develops around the ovum making it impenetrable and preventing other sperm from entering. The nuclei of the sperm and ova fuse together to form a zygote. And from then on an embryo is formed and a foetus develops inside the woman’s womb.
Sexual Reproduction importance
Sexual reproduction ensures that there is genetic variation in a species. since genetic material (chromosomes) from 2 different individuals are brought together.
male and female gametes differ from each other due to a process called meiosis.
Fertilization
This is the fusion of the nuclei of the male and female gametes to form a zygote, from which the offspring develops.
Embryo
A ball of cells that developed from the zygote dividing repeatedly - using the yolk stored in the ovum- .
Implantation
It takes many hours for the embryo to reach the uterus. Upon arrival, the embryo sinks in the thick, soft and spongy lining of the uterus. As the embryo develops so does the placenta which connects to the walls of the uterus.
The process by which the embryo moves down the oviducts and sinks into the uterus lining.
Diffusion
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration until the particles are evenly distributed.
Carbon dioxide, for use in photosynthesis, moves into leaves and plant cells by diffusion.
Oxygen, produced in photosynthesis, moves out of plant cells and leaves by diffusion.
Osmosis
Osmosis is the movement of water molecules through a differentially permeable membrane from a solution containing a lot of water molecules, e.g. a dilute solution (or water), to a solution containing fewer water molecules, e.g. a concentrated solution.
All cells are kept hydrated by water moving into them by osmosis.
Plant cells are kept turgid by water moving into them by osmosis. This causes non-woody stems to stand upright and keeps leaves firm.
osmosis helps water move through pants and ensures leaves get water for photosynthesis
osmosis in animal cells
an animal cell in water or a solution
that is more dilute than its cytoplasm. The cell swells and eventually bursts
an animal cell in a solution that is more concentrated than its cytoplasm. The cell shrinks
osmosis in plant cells
a plant cell in water or a solution
that is more dilute than its cytoplasm
and cell sap. The cell swells and
becomes turgid
a plant cell in a solution that is more concentrated than its cytoplasm and cell sap. The cell shrinks and becomes flaccid. The cell contents are said to be plasmolysed
Placenta- cells of the embryo continue to divide and some of those cells develop into the placenta.
The placenta is a disc of tissue with capillaries running throughout and finger-like projections called villi that project into the uterus lining.
Why is the placenta important?
The placenta allows exchange of materials between the mother’s blood and the embryo’s blood like glucose and oxygen, but prevents mixing of the two bloods which may be of different types. It also prevents certain unwanted substances entering the embryo’s blood from the mother’s blood, e.g. many bacteria and viruses
