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PHYSIOLOGY IV > LECTURE 8 (Female hormones) > Flashcards

LECTURE 8 (Female hormones) Flashcards

1
Q

Describe the embryological development of ovarian eggs

A

1) During foetal life, outer surface of ovary is covered by a GERMINAL EPITHELIUM (embryologically derived from epithelium of germinal ridge) + PRIMORDIAL OVA differentiate from germinal epithelium and migrate into OVARIAN CORTEX
2) Each ovum collects round it a layer of spindle cells from the OVARIAN STROMA + takes on epitheliod characteristics
[called Granulosa cells at this point]
3) Ovum surrounded by a single layer of granulosa cells is called a “Primordial follicle” or “Primary oocyte” -> after follicular growth it becomes “Primary follicles”
4) During reproductive years of life (13-46 years), follicles develop to expel their ova + remainder become degenerate/”atretic”
[in menopause, only a few primordial follicles remain in ovaries + degenerate soon after]

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2
Q

What are the three different types of hormones?

A
  • Gonadotropin-releasing hormone (GnRH)
    [hypothalmic releasing hormone]
  • Follicle-stimulating hormone (FSH) + Luteinising hormone (LH)
    [anterior pituitary sex hormones + secreted in response to GnRH]
  • Oestrogen + Progesterone
    [secreted by ovaries in response to LH and FSH]
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3
Q

Describe the release of GnRH

A
  • Released from hypothalamus increased and decreases much less drastically during the monthly sexual cycle
  • Secreted in short pulses every 90 minutes
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4
Q

What is “Menarche”?

A

The time of the first menstrual cycle

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5
Q

What happens when LH and FSH bind to their receptors in ovarian target cell membranes?

A
  • Increase the cells’ rates of secretion
  • Growth + proliferation of cells
  • Activation of cyclic adenosine monophosphate second messenger system in cytoplasm -> formation of protein kinase + multiple phosphorylations of key enzymes that stimulate sex hormone synthesis
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6
Q

Describe the ovarian egg cells during childhood

A

Granulosa cells provide nourishment for the ovum + secrete an oocyte maturation-inhibiting factor to keep the ovum in its primordial state in the PROPHASE stage of meiosis

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7
Q

What is the effect of increased secretion of LH and FSH?

A
  • Accelerated growth of 6-12 primary follicles each month
  • Rapid proliferation of granulosa cells -> gives rise to more layers
  • Spindle cells derived from ovary interstitium collect in several layers outside granulosa cells -> forms “theca” (2 layers)
    [Theca Interna = epithelioid characteristics + develop ability to secrete oestrogen and progesterone, Theca Externa = develops into highly vascular connective tissue capsule that becomes the capsule of the developing follicle]

ADDITIONAL INFO: The early growth of the primary follicle up to the ANTRAL STAGE is stimulated mainly by FSH alone

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8
Q

What happens after the proliferative phase of growth?

A
  • Mass of granulosa cells secretes a FOLLICULAR FLUID that contains a high concentration of oestrogen
  • Accumulation of fluid causes an ANTRUM to appear within the mass of granulosa cells
  • Greatly accelerated growth occurs, leading to larger follicles called VESICULAR FOLLICLES
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9
Q

What is accelerated growth of follicles into “vesicular follicles” caused by?

A
  • Oestrogen secreted into the follicle causes granulosa cells to form increasing numbers of FSH receptors -> makes granulosa cells more sensitive to FSH
  • Pituitary FSH and oestrogens combine to promote LH receptors on original granulosa cells -> allows LH stimulation to occur alongside FSH stimulation -> rapid increase in follicular secretion
  • Increasing oestrogens from follicle + increasing LH from anterior pituitary -> proliferation of follicular thecal cells
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10
Q

What happens in Atresia?

A

1) Large amounts of oestrogen from the rapidly growing follicle act on the HYPOTHALAMUS to depress further enhancement of FSH secretion -> blocks further growth of less well developed follicles
2) Largest follicle continues to grow because of INTRINSIC POSITIVE FEEDBACK EFFECTS + all other follicles stop growing and involute

EXPLANATION: Atresia is important because it prevents multiple pregnancies

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11
Q

What happens shortly before ovulation?

A

Protruding outer wall of follicle swells rapidly + “stigma” (small area in center of follicular capsule) protrudes like a nipple -> Fluid oozes from follicle through the stigma -> Stigma ruptures widely, allowing a vicious fluid to evaginate outwards -> Vicious fluid carries with it the ovum surrounded by a mass of several thousand small granulosa cells called “Corona radiata”

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12
Q

What happens during ovulation?

A

-

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13
Q

What happens 2 days before ovulation?

A
  • The rate of secretion of LH by the anterior pituitary gland increases markedly
  • FSH increases 2-3 fold
  • FSH and LH act synergistically to cause rapid swelling of the follicle during the last few days before ovulation
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14
Q

What happens before ovulation occurs?

A
  • Rapid growth of follicle
  • Diminished oestrogen secretion after prolonged phase of excessive oestrogen secretion
  • Initiation of secretion of progesterone
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15
Q

Which two events occur that are necessary for ovulation?

A
  • Theca externa begins to release proteolytic enzymes from lysosomes -> cause dissolution of follicular capsular wall + consequent weakening of wall -> further swelling of entire follicle + degeneration of stigma
  • Rapid growth of new blood vessels into follicle wall + prostaglandins secreted into follicular tissues -> plasma transduction into follicle + follicle swelling

FOLLICLE SWELLING + DEGENERATION OF STIGMA -> FOLLICLE RUPTURE -> DISCHARGE OF OVUM

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16
Q

What happens during the “Luteal phase” of the cell cycle?

A
  • After release of ovum, granulosa and theca interna cells change into “Lutein cells” [LUTEINISATION] where they grow + fill with lipid giving a yellow colour [becomes “CORPUS LUTEUM”]
    (dependent on LH + inhibited by luteinisation-inhibiting factor)
  • Granulosa cells -> develop extensive intracellular smooth endoplasmic reticula that form large amounts of progesterone and oestrogen
  • Theca cells -> form androstenedione and testosterone (androgens)
    [most are converted by AROMATASE in oestrogen]
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17
Q

What happens to the Corpus Luteum?

A
  • Grows to 1.5cm 7-8 days after ovulation
  • After 12 days of ovulation, begins to involute + loses secretory function + yellow lipid characteristic
    [becomes “corpus albicans”]
  • Replaced by connective tissue and over months is absorbed
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18
Q

What inhibits the anterior pituitary gland from secreting FSH and LH?

A
  • Oestrogen and progesterone (lesser extent)
  • Inhibin

EXPLANATION: Low blood concentrations of both LH and FSH cause the corpus lute to degenerate completely [“involution” of corpus luteum]

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19
Q

What is the difference in functions between oestrogens and progestins?

A
  • Oestrogens = promote proliferation + growth of specific cells in the body responsible for the development of most secondary sexual characteristics of female
  • Progestins = prepare uterus for pregnancy + breasts for lactation
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20
Q

Describe the synthesis of Oestrogen and Progesterone

A
  • Steroids synthesised from cholesterol + small portion from Acetyl-CoA
  • Mainly progesterone and testosterone and androstenedione are synthesised first -> during follicular phase, most converted to oestrogen by AROMATASE in granulosa cells -> Lack of aromatase in theca cells, androgens diffuse into adjacent granulosa cells for conversion
  • During luteal phase, too much progesterone is formed for all to be converted -> high conc in blood
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21
Q

How are Oestrogen and Progesterone transported in blood?

A

Bound to plasma albumin and with specific progesterone and oestrogen-binding globulins

ADDITIONAL INFO:
binding between hormones is loose enough to rapidly release to tissues over a period of 30 minutes

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22
Q

What are the functions of the liver in oestrogen degradation?

A
  • Conjugates oestrogens to form glucuronides and sulphates -> excreted in bile + urine
  • Converts potent oestrogens, Estradiol and Estrone, into almost totally potent estriol

ADDITIONAL INFO:
Decreased liver function increases the activity of oestrogens in the body (HYPERESTRINISM)

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23
Q

What is the fate of progesterone degradation?

A
  • Almost all progesterone is degraded to other steroids
  • Liver degrades to PREGNANEDIOL -> excreted in urine

ADDITIONAL INFO:
You can estimate rate of progesterone formation in body from the rate of this excretion

24
Q

What are the effects of oestrogens in puberty?

A
  • Ovaries, Fallopian tubes, uterus, vagina, mons pubis, labia majora and minora increase in size
  • Change vaginal epithelium from a cuboidal into a stratified type [more resistant to trauma + infection]
  • Marked proliferation of endometrial storm + greatly increased development of endometrial glands [aid in providing nutrition to implanted ovum]
25
Q

What is the effect of Oestrogens on the Fallopian tubes?

A
  • Cause glandular tissues of lining to proliferate
  • Cause the number of ciliated epithelial cells that line the Fallopian tubes to increase
  • Activity of the cilia is enhanced [helps propel fertilised ovum in that direction]
26
Q

What is the effect of Oestrogens on the breast?

A
  • Development of stromal tissues of the breasts
  • Growth of an extensive ductile system
  • Deposition of fat in the breasts

EXPLANATION:
Oestrogens initiate the growth of the breasts and of the milk-producing apparatus but do not complete the job of converting the breasts into milk-producing organs

27
Q

What is the effect of oestrogens on the skeleton?

A
  • Inhibit osteoclastic activity in the bones + stimulate bone growth
    [stimulates OSTEOPROTEGERIN also called “osteoclastogenesis inhibiting factor”]
  • Cause uniting of the epiphyses with shafts of the long bones
    [Female eunuch devoid of oestrogen production is taller than the normal mature female since epiphyses do not unite at the normal time]
28
Q

What is the effect of Oestrogen deficiency in old age?

A
  • Increased osteoclastic activity
  • Decreased bone matrix
  • Decreased deposition of bone calcium + phosphate

Results in OSTEOPOROSIS -> weak bones + bone fractures -> treat with oestrogen replacement

29
Q

What is the effect of Oestrogen in body metabolism?

A
  • Increase whole-body metabolic rate slightly
  • Slight increase in total body protein
  • Increased deposition of fat (especially buttocks and thighs)
30
Q

What hormones mainly affect hair distribution?

A

Androgens

EXPLANATION: Oestrogens do not greatly affect hair distribution but androgens formed in adrenal glands are mainly responsible

31
Q

What are the effects of Oestrogens on the skin?

A
  • Cause skin to develop a soft and smooth texture
  • Cause skin to thicken
  • Cause skin to become more vascular -> associated with increased warmth of skin + promotes greater bleeding of cut surfaces
32
Q

What is the effect of Oestrogens on electrolyte imbalance?

A

Sodium and water retention by the kidney tubules

33
Q

What is the effect of Progesterone on the Fallopian tubes?

A

Promotes increased secretion by the mucosal lining of the Fallopian tubes -> necessary for nutrition of the fertilised, dividing ovum as it travels through the tube

34
Q

What is the effect of Progesterone on the breasts?

A
  • Promotes development of the lobules and alveoli of the breasts -> causes alveolar cells to proliferate, enlarge and become secretory in nature
  • Causes breasts to swell
    [increased fluid in tissue]
35
Q

What are the different stages of the menstrual cycle?

A

1) Proliferation of the uterine endometrium
2) Development of secretory changes in the endometrium
3) Desquamation of the endometrium (Menstruation)

36
Q

What happens during the Proliferative Phase (Oestrogen phase) of the Endometrial cycle?

A
  • After menstruation, only epithelial cells located in deep portions of glands and crypts of endometrium are left
  • Under influence of oestrogens, stromal and epithelial cells proliferate rapidly -> Endometrium increases in thickness
  • Endometrial glands (especially of cervix) secrete a thin, stringy mucous -> form channels in cervical canal to guide sperm
37
Q

What happens during the Secretory Phase (Progestational phase) of the Endometrial cycle?

A
  • Progesterone and oestrogen are secreted in large quantities by the Corpus Luteum
  • Oestrogen causes cell proliferation + Progesterone causes marked swelling and secretory development of the endometrium
    [glands + blood vessels become tortuous, increased blood supply to endometrium, lipid and glycogen deposits increase in stromal cells]
  • A highly secretory endometrium is produced which contains large amounts of stored nutrients to provide appropriate conditions for implantation of a fertilised egg
38
Q

What happens during menstruation?

A
  • If ovum is not fertilised, Corpus luteum involutes and oestrogen and progesterone decrease to low levels of secretion
  • Decreased stimulation of endometrial cells followed by involution of endometrium itself
  • Vasospasm, decrease nutrients to endometrium and loss of hormonal stimulation -> necrosis of endometrium + blood vessels
  • Mass of desquamated tissue and blood in uterine cavity + contractile effects of prostaglandins -> initiate uterine contractions that expel uterine contents
39
Q

Why is the uterus highly resistant to infection during menstruation?

A

Since a tremendous amount of leukocytes are released along with necrotic material and blood

40
Q

Describe the secretion of GnRH from the hypothalamus

A

GnRH secretion is in pulses lasting 5-25 minutes every 1-2 hours -> causes intermittent output of LH secretion

Explanation: When GnRH is infused continuously, its ability to cause release of LH and FSH by anterior pituitary gland is lost

41
Q

Describe the Centers for GnRH release

A
  • Neuronal activity that causes pulsatile release of GnRH occurs primarily in the MEDIOBASAL HYPOTHALAMUS (especially ARCUATE NUCLEI)
  • Neurons located in pre-optic area of anterior hypothalamus secrete GnRH
  • Multiple neuronal center in higher brain’s “limbic” system (psychic control) modify GnRH release and frequency of pulses
42
Q

Describe the negative feedback effects of LH and FSH secretion

A
  • Oestrogen in small amounts has a strong effect to inhibit LH and FSH -> when oestrogen is available, inhibitory effect of oestrogen is multiplied
  • Feedback effects operate mainly on anterior pituitary gland directly + on hypothalamus to decrease secretion of GnRH
  • Inhibin from Corpus Luteum inhibits LH and FSH secretion
43
Q

What are the causes of the positive feedback effect of oestrogen causing LH surge?

A
  • Oestrogen in the pre-ovulatory stage has a positive feedback effect of stimulating pituitary secretion of LH and FSH
  • Granulosa cells of follicles secrete small but increasing quantities of progesterone a day before LH surge

ADDITIONAL INFO: Without this normal pre-ovulatory surge of LH, ovulation will not occur

44
Q

What are the stages of the feedback oscillation that controls the rhythm of the female sexual cycle?

A

1) Post-ovulatory secretion of the Ovarian hormones and depression of the Pituitary Gonadotropins
[progesterone, oestrogen and inhibin have a negative feedback effect on FSH and LH secretion]
2) Follicular growth phase
3) Pre-ovulatory surge of LH and FSH causes ovulation

45
Q

What are “Anovulatory cycles”?

A

If the pre-ovulatory surge of LH is not of sufficient magnitude, ovulation will not occur and the cycle is said to be “anovulatory”

THE CYCLE IS ALTERED IN THE FOLLOWING WAYS:
- lack of ovulation -> failure of development of corpus luteum -> no secretion of progesterone
- cycle is shortened by several days but rhythm continues

46
Q

What happens in Menopause?

A
  • The cycle ceases and female sex hormones diminish
  • Production of oestrogens decreases as number of primordial follicles approaches zero -> can no longer inhibit LH and FSH production
  • Functions of the body: “hot flushes”, psychic sensations of dyspnea, irritability, fatigue, anxiety, decreased strength and calcifications of bones throughout the body
47
Q

What is Hypogonadism?

A

It is less than normal secretion by the ovaries which can result from poorly formed ovaries, lack of ovaries, or genetically abnormal ovaries that secrete the wrong hormones

EFFECTS:
- Secondary sexual characteristics do not appear + sexual organs remain infantile
- Prolonged growth of long bones due to delayed epiphyseal closure
- Ovaries of fully developed woman are removed -> uterus becomes infantile in size, vagina becomes smaller, vaginal epithelium becomes thin + easily damaged, breasts atrophy, pubic hair becomes thinner
- Amenorrhea (stopping of menstruation)

48
Q

When does female eunuchism occur?

A

When ovaries are absent from birth or when they become non-functional before puberty

49
Q

Describe Hypersecretion by the ovaries

A
  • Rare since excessive secretion of oestrogens decreases the production of LH and FSH in the pituitary -> limits production of ovarian hormones [negative feedback]
  • Caused by a GRANULOSA CELL TUMOUR -> large quantities of oestrogen causing hypertrophy of uterine endometrium + irregular bleeding -> BLEEDING is the first and only indication of tumour
50
Q

Describe the Stimulation of the female sexual act

A
  • Depends on psychic stimulation and local sexual stimulation
  • Sexual sensory signals are transmitted to sacral segments of the spinal cord through the PUDENDAL NERVE and SACRAL PLEXUS -> transmitted to CEREBRUM
51
Q

Describe female erection and lubrication

A
  • Parasympathetic signals dilate the arteries of the erectile tissue (due to release of acetylcholine, nitric oxide and vasoactive intestinal polypeptide) at nerve endings -> allows rapid accumulation of blood in erectile tissue -> Introitus tightens around the penis which aids male in attainment of sexual stimulation for ejaculation to occur
  • Parasympathetic signals pass to Bartholin glands to secrete mucous for lubrication
52
Q

How does the female orgasm aid in fertilisation?

A
  • During the orgasm, perineal muscles of female contract rhythmically -> spinal cord reflexes increase uterine + Fallopian tube motility -> transports sperm up the uterus to the ovum
  • Orgasm causes dilation of the cervical canal for 30 minutes -> easy transport of sperm
  • Release of oxytocin -> rhythmical contraction of uterus -> increased transport of sperm
53
Q

Why is the period of female fertility only 4-5 days?

A

Since the ovum only remains viable and capable of being fertilised after it is expelled from the ovary no longer than 24 hours and sperm remain in the female for up to 5 days

54
Q

What are the tests to test for infertility?

A
  • Analyse urine for pregnanediol (end product of progesterone metabolism) -> lack of substance indicates failure of ovulation
  • Chart body temperature throughout cycle -> progesterone increases temp by 0.5 degrees Celsius
55
Q

What can lack of ovulation cause by hyposecretion of LH and FSH be treated with?

A

Human Chorionic Gonadotropin

Extracted from placenta, it has the same effects as LH and os a powerful stimulator of ovulation -> but, excess use of hormone can cause ovulation from many follicles simultaneously -> causing multiple births

56
Q

How does Endometriosis and Salpingitis lead to infertility?

A

Endometriosis = endometrial tissue grows and menstruates in the pelvic cavity surrounding uterus, Fallopian tubes and ovaries -> fibrosis throughout pelvis which surrounds ovaries so ovum cannot be released into abdominal cavity

Salpingitis = inflammation of Fallopian tubes + causes fibrosis in tubes, occluding them

PHYSIOLOGY IV (14 decks)

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