Chapter 16 - Reproductive Cycles And Fertilisation Flashcards
What is the Ovarian Cycle? (What is involves, associated with and regulated, length)
The ovarian cycle is a series of events that take place within the ovaries.
- MATURATION of an egg and its release into uterine tube
- associated with theses events are the DEVELOPMENT of FOLLICLES in the ovary and Corpus Luteum formation
- HYPOTHALAMUS (pituary gland) secretes hormones to regulates It.
cycles length is highly variable depending on the individual and circumstances
- approximately 20-40 day
- with average of 28 days (only 30% of women experience this)-however the cycle is considered 27-28 day cycle
OVARIAN AND MENSTRUAL CYCLE WORK TOGETHER AT THE SAME TIME
The Ovarian Cycle; Birth
How much? what is it called? Types of follicles and when it stopped division.
- ovaries contain 400 000 immature eggs
- formation of the eggs began before birth during FOETAL DEVELOPMENT
- Cells in the ovary undergo a number of divisions but stop dividing before any eggs are actually formed
It is called a PRIMODORIAL FOLLICLE = primary oocyte + follicular cells
- FOLLICULAR CELLS are other cells within the ovary surround each immature egg to produce a sphere composed of a single layers of cells around the developing egg (they enlarge)= PRIMARY FOLLICLE
- An egg develops in Primary follicle
The primary oocyte (in primary follicle) is in PROPHASE of the 1st meiotic division
- still diploid (2n)
- immature eggs remain in resting phase for many years
What is puberty?
When an individual matures sexually, produces mature Gametes and can reproduce via intercourse.
In females; in period referred to as puberty the menstruation cycle begins and the ovarian cycles CONTINUES.
In males; at puberty the males gametogenesis starts again and produces a continuous supply of sperm in semen.
How does the Ovarian Cycle Continue In Puberty?
At puberty some of the PRIMARY follicles undergo further development
- cells forming the of the primary follicle begin to ENLARGE AND DIVIDE; creating layers of cells around the developing egg
- secretions of these cells create a ‘fluid filled space’ that gradually forces the egg to the edge of the follicle = referred to now as SECONDARY FOLLICLE with secondary oocyte
- Many commence development in each ovarian cycle but usually only one completes development; others normally breakdown and is reabsorbed by ovary
- by this stage primary oocyte has completed 1st division of meiosis; now haploid
- as more FLUID ACCUMULATES within follicle, it continues to enlarge and gradually moves towards the SURFACE OF THE OVARY
- On reaching the surface it produces a BULGE, looks Like a swollen blister on the surface of ovary
- At this stage it is referred to as a MATURE FOLLICLE (aka GRAAFIAN FOLLICLE )
- it usually takes 10-14days for a primary follicle to develop into a mature follicle
Explain what the Ovarian Cycle does During Ovulation
Ovulation; process when the mature follicles bursts, it expels the egg (secondary oocyte)
Once ovulation occurs the open end of the uterine wall (F.T) acts like a funnel over the ovary and captures the egg because the beating Cilia within the funnel create a current that sweeps the egg into oviduct
One follicle usually matures so only one egg is released
Occasionally 2 or more follicles matures at a time releasing more than 1 egg
Egg is gradually swept down the uterine tube towards the uterus by the beating of cilia lining the inside of the tube and the peristalsis like movement of the smooth muscle in F.Tubes
CAN GET FERTILISED IN FALLOPIAN TUBE
What happens in the ovarian Cycle following ovulation ? Fertilisation does/doesn’t occur
Fertilisation does not occur; the ruptured follicle collapses and the blood within forms a clot
- the clot gradually absorbed by the remaining follicle cells which enlarge and change colour to from Cream-coloured body called the CORPUS LUTEUM (Latin yellow body)
- CORPUS LUTEUM excretes the hormone Progesterone which influence the development and thickening of the lining of the uterus
- if fertilisation doesn’t occur the corpus luteum reaches its MAX development about 8-10 days after ovulation
- it begins to CORPUS LUTEUM DEGENERATES into a FIBORIUS MASS OF SCAR TISSUE = CORPUS ALBICANS (Latin white body) which eventually disappears
- ANOTHER Ovarian Cycle Then BEGINS. It is a matter of chance in the same ovary or opposite one
if fertilisation does occur;
- of an egg takes place in endometrium and pregnancy follows
- CORPUS LUTEUM continues to DEVELOPS and the OVARIAN CYCLE CEASES
- produces PROGESTERONE for lining
- it reaches the peak of its development at approx 3rd month of pregnancy - after this it begins to slowly degenerate and still present in ovary at childbirth
- it usually resumes only after breastfeeding of the baby has ceased.
Summary of Ovulation
Primary follicle - secondary follicle - GRAAFIAN/ mature follicle - ovulation - corpus luteum - corpus alibcans
What is the Menstrual Cycle
Menstrual cycle; a cycle (monthly occurrence) where changes in the lining of the uterus wall (ENDOMETRIUM) are closely associated with the stages in the ovarian cycle.
Involves the uterus, and to a lesser extent the vagina.
- prepares uterus for developing embryo (If fertilisation occurs)
- directly controlled by ovarian hormones
- regulated by the sequence of events that take place in ovary
- caused by secretion of OESTROGEN AND PROGESTERONE from the ovary
- begins on the 1st day of menstruation as a period (blood sheds and exits body via vagina) lasts 2-7days and is easily detected.
Explain the Menstrual Cycle
In 1st stage of ovarian cycle (Period where follicle matures) the endometrium of the uterus THICKENS and Builds Up via the FOLLICULAR CELLS produce Oestrogen builds it up
INCREASE NUMBER of BLOOD VESSELS and MUCUS SECRETING GLANDS
AFTER OVULATION the endometrium continues to THICKEN VIA GRAAFIAN/:MATURE FOLLICLE , and ENDOMETRIUM GLANDS it begin to secrete WATERY MUCUS rich in GLYCOGEN.
- if the Egg is NOT FERTILISED by a sperm, the CORPUS LUTEM DEGENERATES, REDUCING PROGESTERONE influencing the buildup of the endometrium which results in its breakdown
- 14 DAYS AFTER OVULATION, blood from BROKEN DOWN-CAPILLARIES, MUCOUS SECRETIONS And CELL DEBRIS from the uterine lining are lost through the vagina = MENSTRUATION
- Menstruation takes place over several days and is commonly referred to as the MENSTRUAL PERIOD
- As this this event is most recognisable point in the menstrual cycle, the onset of menstruation is taken to be day 1 of the cycle
What is Menarche and Menopause?
Menarche; when menstruation first begins.
- marks the commencement of puberty in females
- from that time on a female will have a menstrual cycle about once a month unless it it interrupted by pregnancy
Menopause; the time when the processes that occurred at puberty are reversed
- usually between the age of 45-55
- takes place over a period of years during which time the menstrual cycle becomes irregular until eventually ceases
- typically a woman has potential of about 35 child-bearing years and in most women only 400 of initial 400 000 potential eggs reach maturity
Summary of the stages, days and events OF MENSTRUAL CYCLE
Menstruation; day 1-4; uterine bleeding, accompanied by shedding of the endometrium, and discharge via vagina
Preovulation/ Proliferative phase; day 5-12; Endometrial growth and repair begins, development of ovarian follicle, uterine lining Gradually thickens (2-3mm)
Ovulation; day 13-15; rupture of mature follicle releasing egg and endometrium continued to thicken and soften triggered by Luteinising hormone from pit gland.
Secretion; day 16-20; Secretion of watery mucus by glands of endometrium, cervix and uterine tubes, movement and breakdown of unfertilised egg, development of corpus Luteum
- further endometrium thickening (5-6mm) in response to progesterone from Corp.Lute
Premenstruation; day 21-28; degeneration of corpus luteum, deterioration of endometrium
Factors affecting menstrual cycle
- stresses
- smoking
- sickness
- excessive alcohol consumption
- dieting; extreme W. Loss and eating disorders
- regular strenuous activity (over -sport/exercise)
- medication (the pill)
- Hormone production; different amounts and length presence
What is Endometriosis?
A condition where the endometrium, the tissue lining the uterus grows outside the uterus in other parts of the body.
Most growths occur on organs in the abdominal cavity such as the ovaries, uterine tubes, and outside the of the uterus, bladder, intestines (rectum).
The growths detach and bleed at menstruation, but the blood and tissue cannot be passed to the outside .
It is estimated that 10% of women suffer from endometriosis during their reproductive years.
About 30-40% of those sufferers are infertile- one cause of infertility
Symptoms ; painful (irritation and inflammation in areas), adhesion of organs to each other, adhesion of Fallopian tube oviducts to close
Hormone Regulation
Menstrual and ovarian cycles.(+other features) of human reproductive systems depend on the Endocrine Glands for their regulation and control.
These are glands that empty their secretions called HORMONES into extracellular fluid that surrounds the cells making up the gland.
The secretion then passes into capillaries to be transported by the blood.
Hormones play an important role in the development and maintenance of body structures, processes and behaviours including those associated with reproduction.
Pituitary gland and it’s importance
One of the important endocrine glands associated with the reproductive system = Pituitary gland
It is a small organ lying in a pit in the bone below the brain and above the roof of the mouth
The hormones it secretes includes for reproductive system
When hormone enters the blood it circulates in the body until it reaches the organ on which it will have effect - TARGET ORGAN
Eg testes and ovaries
In addition to the gonadotropin hormones the pituitary glands secretes lactogenic hormone or PROLACTIN which has a direct effect on the greats of a woman, and together with other hormones it is important for the preparation and maintenance of milk production
At puberty the secretions of gonadotropic hormones stimulates a number of changes, both physical and psychological and in both males and females
- in males the production of testosterone and in females the production of oestrogen infulnces the development of the body to sexual maturity
