Gender, family and culture - Physiology Flashcards
1
Q
What is the hypothalamuc pituitary ovarian (HPO) axis?
A
It is a system of controlling female reproduction
2
Q
What are the two components of the menstrual cycle?
A
- Ovarian cycle
- Uterine cycle
3
Q
What is the hormonal cycle tightly regulated to do?
A
- To select ovarian follicle for ovulation
- Prepare endometrium for implantation of fertilized follicle
4
Q
How long is the ovarian cycle?
A
Approximately 28 days
5
Q
What are the phases of the ovarian cycle? and state on which days they occur
A
- Follicular phase 2. Ovulation (days 1-14)
- Luteal phase (days 15-28)
6
Q
Describe the stages of the ovarian cycle
A
- Follicular phase
- Primordial follicles become primary follicles
- 1’ follicles become 2’ follicles and the theca folliculi are formed
- Cells of the theca produce oestrogens during maturation process
- A fluid filled space develops into a corona radiata surrounding the oocyte
- The follicle is now a mature graffian follicle, ready to release a 2’ oocyte at ovulation
- Ovulation
- Ovulation usually occurs in alternative ovaries
- The follice ruptures and the 2’ oocyte is expelled into abdominal cavity
- The oocyte enters the fimbriated end of the fallopian tube
- Pain in the lower abdomen can occur at ovulation (mittlescherz)
- Usually only one oocyte is released in ecah ovarian cycle
- The follicular phase ends with ovulation
- Luteal phase
- The ruptured follicle caves in and fills with a blood clot
- Granulosa and theca cells increase and form an endocrine structure called the corpus luteum
- The corpus luteum secretes progestoerone and oestrogen
- Corpus luteum is essential in preparing for fertilization and for maintaining a pregnancy that should occur
- If fertlization does not occur, the corpus luteum degenerates after 12-14 days
- The area of the corpus luteum becomes scar tissue (corpus albicans)
- If fertilization occurs the corpus luteum continues to function to maintain pregnancy until placental and fetal hormone production is sufficient
7
Q
Describe the follicular phase of the ovarian cycle
A
- Primordial follicles become primary follicles
- 1’ follicles become 2’ follicles and the theca folliculi are formed
- Cells of the theca produce oestrogens during maturation process
- A fluid filled space develops into a corona radiata surrounding the oocyte
- The follicle is now a mature graffian follicle, ready to release a 2’ oocyte at ovulation
8
Q
Describe the ovulation phase of the ovarian cycle
A
- Ovulation usually occurs in alternative ovaries
- The follice ruptures and the 2’ oocyte is expelled into abdominal cavity
- The oocyte enters the fimbriated end of the fallopian tube
- Pain in the lower abdomen can occur at ovulation (mittlescherz)
- Usually only one oocyte is released in ecah ovarian cycle
- The follicular phase ends with ovulation
9
Q
Describe the ovulation phase of the luteal cycle
A
The ruptured follicle caves in and fills with a blood clot
- Granulosa and theca cells increase and form an endocrine structure called the corpus luteum
- The corpus luteum secretes progestoerone and oestrogen
- Corpus luteum is essential in preparing for fertilization and for maintaining a pregnancy that should occur
- If fertilization does not occur, the corpus luteum degenerates after 12-14 days
- The area of the corpus luteum becomes scar tissue (corpus albicans)
- If fertilization occurs the corpus luteum continues to function to maintain pregnancy until placental and fetal hormone production is sufficient
10
Q
a) Name the hromones that the ovarian cycle is controlled by?
b) Where are they released from?
A
a)
- Ganadotrophins
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
11
Q
Describe the role of Follicle-stimulating hormone (FSH) & Luteinizing hormone (LH)
A
FSH and LH fluctuate during the cycle and control the release of the ovarian hromones, oestrogens and progesterone
12
Q
Describe the hormonal control of the ovarian cycle
A
- Follicle-stimulating hormone (FSH) and Leutenizing hormone (LH) stimulate initial follicular development and oocyte maturation
- Small amounts of oestrogen produced by the follicle inhibits secretion of FSH and LH by the pituitary by negative feeback
- Granulosa cells secerete inhibin, which inhibits FSH release
- Oestrogen acually increases the effects of FSH and LH on the follicle
- The follicle continues to develop, and oestrogen levels rise
- Oestrogen plasma levels reach a critical point, which causes oestrogen to stop inhibiting and start stimulation (positive feedback) of the anterior pituitary
- More FSH and LH is prodced in respone by the pituitary, mid cycle sees a surge in LH stimulating ovulation and formation of the corpus luteum, which LH helps to maintain
- Following ovulation, the corpus luteums secretes progesterone and oestrogen
- This results in a negative feedback inhibition of further FSH and LH release (nolonger want follicles to be stimulating)
- If pregnancy does not occur the fall in LHcauses the corpus luteum to degenerate and results in reduced levels of progesteroe and oestrogen
- This removes the inhibition and enables the pituitoary to again secerete FSH and LH, starting a new cycle
13
Q
What is the uterine cycle and describe its role
A
The uterine cycle is changes occurring in the uterus as the endometrium respons to ovarian hormones
It’s role is to prepare the endometrium for possible implantation by the fertilized embryo
14
Q
Name the 3 phases of the uterine cycle
A
- Proliferative phase
- Secretory phase
- Menstrual phase
15
Q
Describe the phases of the uterine cycle
A
Proliferative phase
- Correponds to the follicular phase of the ovarian cycle and starts 5 days when bleeding ceases
- Folllowing mestruation only the basal layer of the endometrium remains (stratum basalis)
- The release of oestrogens results in cell proliferation and regeneration of the stratum functionalis
- The proliferative phase ends with the maturation of the graffian follicle and ovulation at day 14
- The endometrium is 2mm thick
- The proliferative phase sees the cervicle mucus change from a thick plug, blocking the cervix to profuse amounts of thick, slipper mucus that can be penetrated by spermatozoa
Secretory phase
- Corresponds with the luteal phase of the ovarian cycle and lasts 14 days
- The endometrium prepared by oestrogen is now inflluences by progesterone
- Progesterone causes the glands to enlarge and secrete glycogen, to nourish the embryo at implantation
- The spiral arteries in the endometrium is now 5mm thick
- Cervical mucus changes to a thick plug, blocking the cervical canal and protetcing the embryo
- If fertilization does not occur corpus lutueum hormones decline resulting in spiral artery spasm and endometrium degeneration due to depravation of nutrients and autodigestion by lysosomes
- This is followed 24hrs by menstruation
Menstrual cycle
- Lasts 3-6 days
- The spiral arteries dilate and bleed into the necrotic stratum functionalis
- The menstrual flow consists of blood, other fluids, and endometrium fragments
- Menstrual loss is 75ml of which 50% is blood
- Clotting of the menstural blood flow is prevented in the uterus by release of fibrinolysins, ensuring the endometrim is completely expelled
- At the outset of menstruation, the uetrus contracts in response to prosaglandings to expel the blood
- These contractions can result in the pain - dysmenorrhea
