Female reproductive system Flashcards
Where is GnRH released from and what is its action (women)?
The hypothalamus releases gonadotrophin-releasing hormone (GnRH). GnRH stimulates the anterior pituitary to produce luteinising hormone (LH) and follicle-stimulating hormone (FSH).
Role of oestrogen on the Hypothalamic–Pituitary–Gonadal Axis?
Oestrogen has a negative feedback effect on the hypothalamus and anterior pituitary to suppress the release of GnRH, LH and FSH.
Which cells secrete oestorgen?
The theca granulosa cells around the follicles secrete oestrogen.
Action of LH and FSH?
LH and FSH stimulate the development of follicles in the ovaries.
Action of oestrogen (female reproductive system)?
- Breast tissue development
- Growth and development of the female sex organs (vulva, vagina and uterus) at puberty
- Blood vessel development in the uterus
- Development of the endometrium
Action of progesterone (female reproductive system)?
Progesterone acts on tissues that have previously been stimulated by oestrogen. Progesterone acts to:
- Thicken and maintain the endometrium
- Thicken the cervical mucus
- Increase the body temperature
What causes progesterone to be produced?
Progesterone is a steroid sex hormone produced by the corpus luteum after ovulation.
When pregnancy occurs, progesterone is produced mainly by the placenta from 10 weeks gestation onwards.
Levels of GnRH, LH, FSH, oestrogen and progesterone in the system of a female before puberty?
All relatively low
Sequence of female puberty?
Development of breast buds
Pubic hair
Menarche
What enzyme is important in the production of oestrogen and where is it found? What are the implications of this?
Aromatase is an enzyme found in adipose (fat) tissue.
Therefore, the more adipose tissue present, the higher the quantity of the enzyme responsible for oestrogen creation.
here may be delayed puberty in girls with low birth weight, chronic disease or eating disorders, or athletes.
How long after puberty starts does mensturation typically occur?
Two years
Tanner Scale stages in relation to age?
Stage I: Under 10
Stage II: 10-11
Stage III: 11-13
Stage IV: 13-14
Stage V: Over 14
Tanner Scale stages in relation to pubic hair?
Stage I: None
Stage II: Light and thin
Stage III: Coarse and curley
Stage IV: Adult like but not reaching the thigh?
Stage V: Reaching the thigh
Hormonal Changes During Puberty - Female?
Growth hormone (GH) increases initially, causing a spurt in growth during the initial phases of puberty.
The hypothalamus starts to secrete GnRH, initially during sleep, then throughout the day in the later stages of puberty.
GnRH stimulates the release of FSH and LH from the pituitary gland.
FSH and LH stimulate the ovaries to produce oestrogen and progesterone.
FSH levels plateau about a year before menarche.
LH levels continue to rise, and spike just before they induce menarche.
Follicular development in the ovaries?
Follicles are oocytes surrounded by granulosa cells
Stages:
Development that occurs independent of the menstrual cycle:
Primordial follicles
Primary follicles
Secondary follicles
At follicular stage:
Antral follicles (also known as Graafian follicles)
Secondary follicles have developed receptors to FSH so requires FSH to develop into astral follicles
Menstrual cycle: follicular stage
Menstruation from day 1
FSH stimulates further development of the secondary follicles.
As the follicles grow, the granulosa cells that surround them secrete increasing amounts of oestradiol (oestrogen).
The oestradiol has a negative feedback effect on the pituitary gland, reducing the quantity of GnRH produced to act on the AP to produce more LH and FSH.
The rising oestrogen also causes the cervical mucus to become more permeable, allowing sperm to penetrate the cervix around the time of ovulation.
One of the follicles will develop further than the others and become the dominant follicle.
Luteinising hormone (LH) spikes just before ovulation, causing the dominant follicle to release the ovum (an unfertilised egg) from the ovary.
Ovulation happens 14 days before the end of the menstrual cycle
Luteal Phase of the menstrual cycle - absence of fertilsation
After ovulation, the follicle that released the ovum collapses and becomes the corpus luteum.
The corpus luteum secretes high levels of progesterone, which maintains the endometrial lining.
This progesterone also causes the cervical mucus to become thick and no longer penetrable.
The corpus luteum also secretes a small amount of oestrogen.
When there is no fertilisation of the ovum, and no production of hCG, the corpus luteum degenerates and stops producing oestrogen and progesterone.
This fall in oestrogen and progesterone causes the endometrium to break down and menstruation to occur.
Additionally, the stromal cells of the endometrium release prostaglandins.
Prostaglandins encourage the endometrium to break down and the uterus to contract.
Menstruation starts on day 1 of the menstrual cycle.
The negative feedback from oestrogen and progesterone on the hypothalamus and pituitary gland ceases, allowing the levels of LH and FSH to begin to rise, and the cycle to restart.
The luteal phase of the menstrual cycle - when fertilisation occurs
After ovulation, the follicle that released the ovum collapses and becomes the corpus luteum.
The corpus luteum secretes high levels of progesterone, which maintains the endometrial lining.
This progesterone also causes the cervical mucus to become thick and no longer penetrable.
The corpus luteum also secretes a small amount of oestrogen.
When fertilisation occurs, the syncytiotrophoblast of the embryo secretes human chorionic gonadotrophin (HCG).
Progesterone continues to be realised maintaining the pregnancy
What tissue is involved in menstruation?
Menstruation involves the superficial and middle layers of the endometrium separating from the basal layer. The tissue is broken down inside the uterus, and released via the cervix and vagina. The release of fluid containing blood from the vagina lasts 1 – 8 days.
Where are luteinizing hormone (LH) and follicle stimulating hormone (FSH) produced?
Anterior pituitary gland
Symptoms indicative of ovulation
An increase in a woman’s basal body temperature occurs due to the LH surge.
As a result, the rise in body temperature indicates that ovulation is likely to occur in the next 24-48 hours.
The cervical mucus also becomes thinner around the time of ovulation to allow easier passage of sperm.
At what point of the menstrual cycle is a woman most fertile
Days 9-16
The most fertile period of the menstrual cycle is from 5 days before ovulation to 1-2 days after. Couples often use this knowledge to increase their chances of conception.
Roles of LH
Formation and maintenance of the corpus luteum
Thinning of the Graafian follicles membrane
In a normal 28 day menstrual cycle, when would you expect the LH surge to occur, and when does ovulation subsequently occur?
The LH surge usually occurs on day 12. This occurs due to oestrogen levels reaching a peak level which stimulates large amounts of LH production. The high LH level causes the membrane of the Graafian follicle to become thin. As a result, 24-48 hours after the LH surge ovulation usually occurs due to the rupture of the Graafian follicle.
Functions of progesterone
Inhibition of LH and FSH production
Initiation of the secretory phase of the endometrium
Increase in basal body temperature
What are the effects of increased levels of oestrogen in the follicular phase of the menstrual cycle?
Thinning of cervical mucous
Thickening of the endometrium
Physiological aetiology of increased vaginal discharge
Pregnancy
Sexual arousal
Menstrual cycle variation
Pathological aetiology of increased vaginal discharge
Vaginal: candidiasis, trichomoniasis, gardnerella associated, forigen body, post menopausal vaginitis
Cervical: gonorrhoea, non specific genital infection, herpes, cervical ectopy (rare), cervical neoplasm e.g. polyp
Normal endometrial thickness pre menopause
during menstruation: 2-4 mm
early proliferative phase (day 6-14): 5-7 mm
late proliferative / preovulatory phase: up to 11 mm
secretory phase: 7-16 mm
following dilatation and curettage or spontaneous abortion: <5 mm, if it is thicker consider retained products of conception
Normal endometrial thickness post menopause?
vaginal bleeding (and not on tamoxifen):
suggested upper limit of normal is <5 mm
no history of vaginal bleeding:
the acceptable range of endometrial thickness is less well established in this group, cut-off values of 8-11 mm have been suggested
if on tamoxifen 3: <5 mm
At what phase of the menstural cycle is it best to perform a hysterosalpingogram
Proliferitive phase
Not pregnant, endometrium thinnest so can visualise cervix best
Hormonal changes in pregnancy?
Increase in:
Steroid hormones (anterior pituitary gland produces more ACTH leading to increased steroid production, particular aldosterone and cortisol)
T3/T4 (TSH remains normal)
Prolactin (anterior pituitary gland produces more)
Melanocyte stimulating hormone (anterior pituitary gland produces more)
Oestrogen (Produced by placenta throughout pregnancy)
Progesterone (The corpus luteum produces progesterone until ten weeks gestation. The placenta produces it during the remainder of the pregnancy)
HCG (roughly doubling every 48 hours until they plateau around 8 – 12 weeks, then gradually start to fall)
Decrease in:
FSH and LH (Increased prolactin acts to suppress FSH and LH)
Respiratory changes in pregnancy?
Tidal volume and respiratory rate increase in later pregnancy, to meet the increased oxygen demands.
Renal changes in pregnancy?
Increase in:
Blood flow
EGFR
Sodium reabsorption (Increased aldosterone)
Water reabsorption (Increased aldosterone)
Protein excretion
Physiological hydronephrosis (Dilatation of the ureters and collecting system, leading to a physiological hydronephrosis (more right-sided)
Blood changes in pregnancy?
Increase in:
RBC
WBC
ALP (up to 4 times normal, due to secretion by the placenta)
Clotting factors (Clotting factors such as fibrinogen and factor VII, VIII and X increase in pregnancy, making women hyper-coagulable)
ESR
D Dimer
Platelets
Decrease in:
Albumin (due to loss of proteins in the kidneys)
Platelets
Haematocrit ( Plasma volume increases more than red blood cell volume, leading to a lower concentration of red blood cells. High plasma volume means the haemoglobin concentration and red cell concentration (haematocrit) fall in pregnancy, resulting in anaemia.)
{Calcium requirements increase, but so does gut absorption of calcium, meaning calcium levels remain stable}
Skin changes in pregnancy?
Linea nigra (Increased melanocyte stimulating hormone from AP causes increased pigmentation)
Melasma (Increased melanocyte stimulating hormone from AP causes increased pigmentation)
Striae gravidarum
Spider naevi
Palmar erythema
General itchiness (pruritus) can be normal, but can indicate obstetric cholestasis
Cardiovascular changes in pregnancy?
Increase:
Blood volume
Plasma volume
Cardiac output
Decrease in:
Vascular resistance
Blood pressure (in early and middle pregnancy, returning to normal by term)
Peripheral Vasodilation (also causes flushing and hot sweats)
Varicose veins (can occur due to peripheral vasodilation and obstruction of the inferior vena cava by the uterus)
Uterus weight change in pregnancy
Aprox 100g to 1.1kg
There is hypertrophy of the myometrium and the blood vessels in the uterus.
Myometrium change in pregnancy
Hypertrophy
Cervical changes in pregnancy
Increased discharge
Ectropian
Both due to increased oesterogen (produced by placenta)
Vaginal changes in pregnancy
Increased discharge
Hypertrophy
Candida
Bacteria
All due to increase in oestrogen (produced by placenta)
What is the transformation zone and how can it appear?
The transformation zone is the border between the columnar epithelium of the endocervix (the canal), and the stratified squamous epithelium of the ectocervix (the outer area of the cervix visible on speculum examination).
When the transformation zone is located on the ectocervix, it is visible during speculum examination as a border between the two epithelial types.
Primordial follicle
Primordial follicles each contain a primary oocyte which is contained within the pregranulosa cells surrounded by the basal lamina layer
The oocytes are the germ cells (first generation of sex cell) that eventually undergo meiosis to become the mature ovum, ready for fertilisation.
They contain the full 46 chromosomes.
These primordial follicles and oocytes spend the majority of their lives in a resting state inside the ovaries, waiting for their time to develop into primary follicles
Primary follicle
Primordial follicles grow and become primary follicles. These primary follicles have three layers:
The primary oocyte in the centre
The zona pellucida
The cuboidal shaped granulosa cells
The granulosa cells secrete the material that becomes the zona pellucida. They also secrete oestrogen.
As the follicles grow larger, they develop a further surrounding layer called the theca folliculi. The inner layer of the theca folliculi is called the theca interna. The theca interna secretes androgen hormones. The outer layer, called the theca externa, is made up of connective tissue cells containing smooth muscle and collagen.
Theca folliculi of the primary follicle
Theca folliculi develops as follicle grows bigger
Two layers:
The theca interna secretes androgen hormones.
The outer layer, theca externa, is made up of connective tissue cells containing smooth muscle and collagen.
Secondary follicle
The process of primordial follicles maturing into primary and secondary follicles is always occurring, independent of the menstrual cycle.
As primary follicles become secondary follicles, they grow larger and develop small fluid-filled gaps between the granulosa cells.
Once the follicles reach the secondary follicle stage, they have receptors for follicle stimulating hormone (FSH).
Further development after the secondary follicle stage requires stimulation from FSH.
At the start of the menstrual cycle, FSH stimulates further development of the secondary follicles.
Development of the antral follicles
FSH stimulation at the start of the menstural cycle causes the secondary follicle develops a single large fluid-filled area within the granulosa cells called the antrum. This is the antral follicle stage.
This antrum fills with increasing amounts of fluid, making the follicle expand rapidly.
The corona radiata is made of granulosa cells, and surrounds the zona pellucida and the oocyte.
At this point, one of the follicles becomes the dominant follicle. The other follicles start to degrade, while the dominant follicle grows to become a mature follicle. This follicle bulges through the wall of the ovary.
What happens to the remainder of the dominant follicle once ovulation has occurred?
The leftover parts of the follicle collapse and turn a yellow colour becoming the CORPUS LUTEUM.
The cells of the granulosa and theca interna become luteal cells.
Luteal cells secrete steroid hormones, most notably progesterone.
Which two things will happen to a corpus luteum?
The corpus luteum persists in response to human chorionic gonadotropin (HCG) from a fertilised blastocyst when pregnancy occurs.
When fertilisation does not occur, the corpus luteum degenerates after 10 to 14 days.
What happens to the primary oocyte once released from the dominant follicle just prior to fertilisation?
Just before and around the time of ovulation, the primary oocyte undergoes meiosis.
This process splits the full 46 chromosomes in the oocyte (a diploid cell) into two, leaving only 23 chromosomes (a haploid cell). The other 23 chromosomes float off to the side and become something called a polar body.
It is then a secondary oocyte.
The female egg (ovum) at this stage still has the surrounding layers from its time in the follicle. In the middle is the oocyte with the first polar body, surrounded by the zona pellucida and the granulosa cells that make up the corona radiata.
Structure of a blastocyst
The blastocyst contains the main group of cells in the middle, called the embryoblast.
Alongside the embryoblast is a fluid-filled cavity called the blastocele.
Surrounding the embryoblast and the blastocele is an outer layer of cells called the trophoblast.
At this point, it gradually loses the corona radiata and zona pellucida.
When the blastocyst enters the uterus, it contains 100-150 cells.
Basic overview of stages from fertilsation to implantation
Fertilisation occurs, fertilised egg becomes ZYGOTE
Zygote divides to become mass of cells - MORULA
Fluid filled cavity forms within the morula becomes the BLASTOCYST
BLASTOCYST implants into the stroma of the endometrium
What structure is formed surrounding the embryonic disc, yolk sac and amniotic sac
Over a short time, a space called the chorionic cavity forms around the yolk sac, embryonic disc and amniotic sac. These structures are suspended from the chorion by the connecting stalk, which will eventually become the umbilical cord.
What are the layers of the fetal pole
The ectoderm (outer layer)
The mesoderm (middle layer)
The endoderm (inner layer)
These three layers go on to become all the different tissues of the body.
