physiology of female reproductive system 01092010
TRANSCRIPT
FEMALE REPRODUCTIVE SYSTEM
• Assoc Prof Dr Muhammad Shamsir
• Dr Noorzaid Muhamad
• Pn Resni Mona
Genitalia (Sex Organs)
• Internal genitalia– duct system from ovary to outside the body
consisting of uterine tubes, uterus & vagina
• External genitalia– clitoris, labia minora, and labia majora– accessory glands beneath the skin provide
lubrication for intercourse
Ovary• Ovaries produce eggs
and female hormones– almond-shaped organ, 3
cm x 1.5 cm x 1 cm– Inside tunica albuginea
capsule like the testes– cortex producing gametes– medulla holding vessels
• Each egg develops in its own fluid-filled follicle and is released by ovulation, bursting of the follicle
Anatomy of Ovary
Uterine or FallopianTubes (Oviducts)
• 10 cm long, muscular tube (smooth muscle) lined with ciliated cells
• Major portions of tube– near uterus forms a
narrow isthmus– middle portion is body
(ampulla)– flared distally into
infundibulum with fimbriae
The Uterus• Thick-walled, pear-shaped
muscular chamber opening into vagina and tilted forward over the urinary bladder– harbor fetus, provide nutrition
for fetus and expel fetus at end of development
– openings into uterine tubes in its two upper corners
– fundus (broad superior curvature), body (midportion) and cervix (cylindrical inferior end)
– uterus measures 7 cm from cervix to fundus
– internal & external os of cervical canal (narrow passage through cervix)
– cervical canal contains cervical glands that secrete mucus to prevent spread of microoganisms from the vagina to the uterus; near ovulation mucus is thinner for easier passage of sperm
Vagina
• 8-10 cm long, distensible muscular tube– allows for discharge of menstrual fluid, receipt of semen
and birth of baby
• no glands, lubricated by transudation of serous fluid through its walls and by mucus from cervical glands above it– vaginal epithelial cells rich in glycogen– bacteria ferment glycogen to lactic acid producing
acidic pH that inhibits growth of pathogens (acidity is neutralized by the semen so it does not harm the sperm)
• hymen - a membranous fold of tissue that partly or completely occludes the external vaginal orifice
• vaginal rugae - transverse friction ridges, stimulate penis
The Vulva (Pudendum)• Mons pubis = mound of fat over
pubic symphysis• Labia majora = thick folds of skin
and fat inferior to mons• Labia minora = more medial, thin
folds– form vestibule containing
urethral & vaginal openings– form hoodlike prepuce over
clitoris• Clitoris = erectile, sensory organ,
pair of corpora cavernosa enclosed in connective tissue (has no corpus spongiosum)– homologous to penis of male
• Vestibular bulbs = erectile tissue around vagina
• Paraurethral glands (homologous to male prostate) and greater vestibular glands (homologous to bulbourethral glands of male) & lesser vestibular glands open into vestibule for lubrication
Puberty
Breast Developmentfirst physical sign of puberty in girls is usually a firm, tender lump under the center of the
areola of one or both breasts, occurring on average at about 10.5 years of age. Referred to as thelarche. Classified using Tanner staging.
Tanner I • no glandular tissue; areola follows the skin contours of the chest
(prepubertal) [typically age 10 and younger]Tanner II • breast bud forms, with small area of surrounding glandular tissue; areola
begins to widen [10-11.5]Tanner III • breast begins to become more elevated, and extends beyond the borders of
the areola, which continues to widen but remains in contour with surrounding breast [11.5-13]
Tanner IV • increased breast size and elevation; areola and papilla form a secondary
mound projecting from the contour of the surrounding breast [13-15]Tanner V • breast reaches final adult size; areola returns to contour of the surrounding
breast, with a projecting central papilla. [15+]
Pubic hair Second noticeable change in puberty, usually within a few months
of thelarche, referred as pubarche.
Tanner I • no pubic hair at all (prepubertal Dominic state) [typically age 10 and
younger]Tanner II • small amount of long, downy hair with slight pigmentation at the
base of the penis and scrotum (males) or on the labia majora (females) [10–11.5]
Tanner III • hair becomes more coarse and curly, and begins to extend laterally
[11.5–13]Tanner IV • adult-like hair quality, extending across pubis but sparing medial
thighs [13–15]Tanner V • hair extends to medial surface of the thighs [15+]
• Axillary hair
• Growth spurt
• Menarche (menses)
Menstrual cycle
Menstrual Cycle
• from Greek words mean moon + beginning • A specific hormonal signal for menarche is not known• menarche - relatively chance result of the gradual thickening of the
endometrium induced by rising estrogen.• When menarche has failed to occur for more than 3 years after
thelarche, or beyond 16 years of age, the delay is referred to as primary amenorrhea.
• Divided into 2 distinct cycles – endometrial and ovarian
Menstrual Cycle -- Proliferative Phase
• Time of rebuilding of endometrial tissue lost at last menstruation -- mitosis occurs in stratum basalis (day 6 to 14)
• Result of estrogen from developing follicles• Estrogen also stimulate endometrium to produce progesterone
receptors• Endometrium reaches 2-3 mm in thickness
Proliferative phase
• Further thickening of endometrium due to secretion & fluid accumulation -- not mitosis (day 15 to 26)
• Due to progesterone stimulation of glands• Reaches 5-6 mm in thickness
Menstrual Cycle -- Secretory Phase
Menstrual Cycle -- Premenstrual Phase
• Endometrial degeneration (last 2 days of menstrual cycle)• Progesterone level falls due to atrophy of corpus luteum• Spiral arteries constrict causing endometrial ischemia• Pools of blood accumulate in stratum functionalis
Menstrual Cycle -- Menstrual Phase
• Blood, serous fluid and endometrial tissue are discharged (day 1 to 5)
• Average woman loses 40 mL of blood & 35 mL of serous fluid --- contains fibrinolysin so it does not clot
Ovarian Cycle -- Follicular Phase
• From beginning of menstruation (day 1) to ovulation(14) – most variable part of cycle
• Seldom possible to predict date of ovulation• Contains menstrual and preovulatory phases
• End of menstruation to the day of ovulation (days 6 to 14)• Growing follicle secretes estrogen which FSH secretion by anterior
pituitary and makes follicle more sensitive to FSH• one follicle advances to mature (graafian) stage & protrudes from
surface of ovary– atresia of other follicles occurs with FSH
• Primary oocyte completes meiosis I and becomes secondary oocyte• Secondary oocyte stopped at metaphase II stage of meiosis • FSH and estrogen stimulate follicle to produce LH receptors
Follicular Phase - Preovulatory Phase
Ovarian Cycle -- Ovulation
• Ovulation, release of secondary oocyte (day 14)• Results from a spike of LH (caused by estrogen from follicle)
– LH blood flow in follicle, more serous fluid filters from capillaries causes follicle to swell rapidly; LH stimulates secretion of collagenase which weakens ovarian wall; fluid oozes out with secondary oocyte and is swept up into uterine tube by fimbriae
Ovarian Cycle -- Postovulatory Phase
• Ovulation to beginning of menstruation (day 15-28)• Luteal phase (first 12 days) - corpus luteum forms from ruptured
follicle under direction of Luteinizing Hormone progesterone stimulates secretory phase of menstrual cycle (in uterus)
• Premenstrual phase (last 2 days) – if no pregnancy, corpus luteum corpus albicans progesterone menstruation
• If pregnancy occurs corpus luteum is active for about 3 months
• During discharge of menstrual fluid (days 1-5)• Day 25 previous cycle (3 days before menstruation) FSH
stimulating 20-25 primary oocytes to begin meiosis I• Follicles around oocytes develop (primordial follicle primary
follicle secondary follicle)
Follicular Phase - Menstrual Phase
Female sexual cycle (a) The ovarian cycle (events in the ovary);(b) the menstrual cycle (events in the uterus)
Oogenesis
Oogenesis• Monthly event producing 1 haploid egg by meiosis• Embryonic development of ovary
– female germ cells arise from yolk sac of embryo– differentiate into oogonia & multiply in number– transform into primary oocytes (eggs) -- early meiosis I– most degenerate (atresia) by time reach childhood– by puberty 400,000 oocytes remain
• Beginning in adolescence, FSH stimulates completion of meiosis I, produces secondary oocyte & 1st polar body– proceeds to meiosis II & ceases until fertilization– if not fertilized secondary oocyte dies and never
finishes meiosis– after fertilization , releases 2nd polar body which
disposes of one chromatid from each chromosome
Oogenesis and Follicle Development
fertilisation
• Union of a human egg and sperm, usually occurring in the ampulla of the uterine tube.
Viability of Gametes• Oocyte remains viable approximately 24 hours after
ovulation while spermatozoa may remain viable in female reproductive tract for several days.
Results of Fertilization• Completion of 2nd meiotic division of the female gamete.• Formation of zygote.• Restoration of the diploid number of chromosomes.• Determination of sex of the embryo.• Initiation of cleavage.
Clevage
• The two - cell stage zygote undergoes a series of mitotic divisions, resulting in an increase in the number of cells (blastomeres)
• Clevage begins at about 30 hrs after fertilization.• 16 cells stage zygote (morula) is formed about 3 days
after fertilization.• About 4 days after fertilization, a fluid - filled space
(blastocyst cavity or blastocele ) appears inside the morula.
• As fluid increases in the blastocyst cavity, it separates the blastomeres into 2 parts i.e. outer cell layer (trophoblast) and inner cell layer (embryoblast). At this stage, the conceptus is called blastocyst.
Implantation• Burrowing and embedding of the early
blastocyst into the deep layers of uterine endometrium by the end of the 1st week of development.
Site of Implantation• It occurs along the posterior or anterior
wall of the body of the uterus near the fundus.
Pregnancy
Pregnancy
• carrying of one or more offspring, known as a fetus or embryo, inside the uterus of a female human.
• Obstetrics is the medical field that studies and treats pregnant patients.
• pregnancy =gravid, and a pregnant female is sometimes referred to as a gravida.
Pregnancy
• Pregnancy - female gamete or oocyte (egg) penetrated by male gamete spermatozoon in a process referred to "fertilization", or commonly known as "conception".
• The fusion of male and female gametes usually occurs through the act of sexual intercourse.
• However, artificial insemination has also made achieving pregnancy possible in such cases where sexual intercourse is not potentially fertile (through choice or male/female infertility).
Hormones During Pregnancy
Human chorionic gonadotropin hormone(HCG)– This hormone is only produced during pregnancy
-- first by the ovaries and later by the placenta. – HCG hormone levels found in maternal plasma
and urine increase dramatically during the first trimester and may contribute to causing nausea and vomiting often associated with pregnancy.
– This hormone prevents the release of eggs from the ovaries and stimulates the production of the hormones estrogen and progesterone.
Hormones During Pregnancy
Human placental lactogen (HPL)– This hormone, produced by the placenta,
ensures proper fetal development and stimulates the milk glands in the breasts in anticipation of breastfeeding.
Hormones During Pregnancy
Estrogen– This group of hormones is responsible for
the development of the female sexual characteristics.
– Normally formed in the ovaries, this hormone is also produced by the placenta during pregnancy, to help maintain a healthy pregnancy.
Hormones During Pregnancy
Progesterone • This hormone is produced by the ovaries and by the
placenta during pregnancy.• Progesterone stimulates the thickening of the
uterine lining in anticipation of implantation of a fertilized egg.
• During pregnancy, progesterone is responsible for placental functioning.
• Levels of progesterone will drop to initiate labor at the end of pregnancy
Parturition
• Process which the baby is born.
• The exact cause is not known. Two categories of effect :-– Hormonal changes– Mechanical factors – stretch of uterine
musculature
Hormonal changes
– Ratio of estrogens to progesterone– Progesterone inhibits contraction while Estrogens
increases contraction.– Increase in Estrogen to Progesterone ratio at the end of
pregnancy
– Effect of oxytocin– Causes uterine contraction– Increase in responsiveness of uterus to oxytocin at the
end of pregnancy– Increase in rate of oxytocib secretion near term.– Stretching of uterus cause neurogenic reflex that
increases oxytocin secretion.
– Effect of fetal’s hormones– The fetus’ pituitary gland also secretes increasing
quantities of oxytocin– Fetal membranes also releases prostaglandins which
increases the intensity of uterine contractions.
• Mechanical factors – stretch of uterine musculature
Lactation
Prolactin
• Prolactin stimulates mammary glandular ductal growth and epithelial cell proliferation and induces milk protein synthesis.
• Prolactin is produced by the adenohypophysis (anterior pituitary) and released into the circulation.
• The regulation of prolactin levels in the plasma is controlled by the dopaminergic system.
• Prolactin acts on the human breast to produce milk. This occurs by binding to mammary epithelial cell prolactin receptors, which stimulates synthesis of mRNA of milk proteins.
• It takes several minutes of the infant sucking at the breast to cause prolactin secretion.
• Prolactin is also important in inhibiting ovulation.
Oxytocin
• The other important hormone involved in the milk ejection or letdown reflex is oxytocin.
• When the neonate is placed at the breast and begins suckling, oxytocin is released.
• The suckling infant stimulates the touch receptors that are densely located around the nipple and areola.
• The tactile sensations create impulses that, in turn, activate the dorsal root ganglia via the intercostals nerves.
• These impulses ascend the spinal cord, creating an afferent neuronal pathway to both the paraventricular nuclei of the hypothalamus where oxytocin is synthesized and secreted by the pituitary gland.
• The stimulation of the nuclei causes the release of oxytocin down the pituitary stalk and into the posterior pituitary gland, where oxytocin is stored.
• Oxytocin causes the contraction of the myoepithelial cells that line the ducts of the breast. These smooth muscle–like cells, when stimulated, expel milk from alveoli into ducts and subareolar sinuses that empty through a nipple pore.
comparison
• Spermatogenesis– Life long process
– Hormone – testosterone
– Produce millions
– Carries X / Y chromosome
– Meiosis – resulting in increased number
• Oogenesis– Intrauterine life,
stopped until puberty– Hormone – estrogen
– Number – 400,000 at birth
– Carries X chromosome only
– Meiosis – resulting in decreased number