The Reproductive System - Female PDF

The Reproductive System Female Female Reproductive Anatomy Ovary: produce female eggs/ovum as well as estrogen & progesterone Ovum (Egg): female reproductive cells that contribute X chromosomes. Fallopian tubes (Oviducts): tubes that transport ovum to the uterus; passageway whe...

The Reproductive System Female Female Reproductive Anatomy Ovary: produce female eggs/ovum as well as estrogen & progesterone Ovum (Egg): female reproductive cells that contribute X chromosomes. Fallopian tubes (Oviducts): tubes that transport ovum to the uterus; passageway where fertilization occurs; a possible site of ectopic pregnancy; site where tubal ligation (sterilization) occurs. Female Reproductive Anatomy Uterus “womb”: when an egg is fertilized it becomes implanted within the lining of the uterus; when no fertilized egg is present the lining of the uterus sheds. Cervix: lower end of the uterus; an opening between the uterus and vagina that passes sperm, menstrual fluid, and a fetus. Vagina: pathway for menstrual flow, birth canal, sperm, and STDs. Opening for sexual intercourse and contains vaginal secretions/lubrication. Female Reproductive Anatomy Urethra: opening for urine. Clitoris: consists of erectile tissue like the penis  Oogenesis During fetal development, primitive germ cells in the ovaries differentiate into Oogonia. These oogonia rapidly divide to form thousands more  Oogenesis Oogonia then enter a growth phase, enlarge, and become Primary Oocytes. Primary oocytes begin the first meiotic division but stop in prophase (I). The cells remain at this stage until puberty  Oogenesis Many of the primary oocytes degenerate before birth leaving 700,000 oocytes at birth. This is a lifetime supply. No more will develop after birth. By puberty the number declines to approx. 400,000  Oogenesis At puberty FSH stimulates several primary oocytes to start growing each month. One of the primary oocytes outgrows the others and completes meiosis I producing a Secondary Oocyte and a smaller Polar Body  Oogenesis The secondary oocyte begins the second meiotic division but stops in metaphase (II) Ovulation occurs If fertilization occurs, meiosis II is completed to produce an Ovum and a Second Polar Body. The first polar body also divides to produce two smaller polar bodies. Polar bodies degenerate.  The maturation of a follicle Primary follicle becomes a secondary follicle when a fluid filled cavity forms. A secondary follicle becomes a Graafian follicle when the oocyte sits on a stalk. Ovulation occurs and the oocyte is ejected from the follicle. The follicle post ovulation becomes the corpus luteum* (Yellow body) which degenerates. *The corpus luteum secretes progesterone which thickens the uterine lining in preparation for the fertilized egg  Fimbriae The cilia of the fimbriae beat and create a current in peritoneal fluid. Without this current the oocyte could be lost into the peritoneal cavity (The fallopian tubes do not directly connect to the ovaries)  Uterus A hollow, thick walled organ which receives, retains, and nourishes a zygote. 7.5cm long with a maximum diameter of 5 cm Weighs 50-100 g Normally it bends anteriorly near its base; the uterus covers the superior and posterior surfaces of the urinary bladder - Anteflexion In about 20% of women the uterus bends backward toward the sacrum – Retroflexion. A retroflexed uterus generally becomes anteflexed spontaneously during the third month of pregnancy  The Uterus – Internal Anatomy Two anatomical regions: 1. Body 2. Cervix  The Uterus – Internal Anatomy The Body – Largest portion of the uterus – Fundus is the rounded, superior portion of the body superior to the attachment of the uterine tubes – Ends at a constriction known as the isthmus of the uterus  The Uterus – Internal Anatomy The Cervix – the inferior portion of the uterus that extends from the isthmus to the vagina – It projects about 1.25 cm into the vagina – Within the vagina its distal end forms a curving surface that surrounds the external os of the uterus – The external os leads into the cervical canal that opens into the uterine cavity at the internal os  Uterine Blood Supply The uterus receives blood from branches of the uterine arteries and from branches of the ovarian arteries The branches to the uterus are extensively interconnected Numerous veins and lymphatics also drain the uterus  Uterine Innervation Autonomic fibres from the hypogastric plexus (sympathetic) and from sacral segments S3 and S4 (parasympathetic) Sensory information reaches the CNS within the dorsal roots of spinal nerves T 11 and T12 The most delicate anesthetic procedures used during labour and delivery, known as segmental blocks, target only spinal nerves T10-L1  The Uterine Wall Approx. 1.5 cm thick in women of reproductive age who have not given birth Consists of a thick outer Myometrium and a thin, inner, glandular Endometrium The Perimetrium is the serous membrane that covers the fundus and posterior surface of the uterine body  The Uterine Lining The Endometrium – Contributes 10% to the uterine mass – The glands and vascular tissue support the developing fetus – Under the influence of Estrogen the uterine glands, blood vessels, and epithelium change with the phases of the uterine cycle  The Uterine Lining The Myometrium – Thickest portion of the uterine wall – Constitutes 90% of the mass of the uterus – Smooth muscle arranged into longitudinal, circular and oblique layers – Provides the force needed to expel the fetus  Uterine Histology The endometrium may be divided into: Functional Zone – closest to the uterine cavity – Contains most of the uterine glands – Contributes most of the endometrial thickness – Changes dramatically in thickness and structure during the menstrual cycle Basilar Zone – Attaches endometrium to the myometrium – Contains the terminal branches of the tubular uterine glands  Uterine Histology Within the myometrium branches of the Uterine arteries form Arcuate Arteries Radial arteries branch from these to supply Straight (Basal) Arteries which supply blood to the Basilar zone and Spiral arteries to supply blood to the Functional Zone  The Uterine Cycle A repeating series of changes in the structure of the endometrium Ranges from 21 to 35 days (avg. 28 days) Consists of three phases: – Menses – Proliferative phase – Secretory phase Menses and Proliferative phase occur during the Follicular phase of the Ovarian cycle while the secretory phase occurs during the Luteal phase  Menses Degeneration of the functional zone Caused by the constriction of the spiral arteries Deprived of O2 and nutrients the secretory glands and other tissues deteriorate The weakened arterial walls rupture and blood pours into the connective tissues of the functional zone Blood cells and degenerating tissue break away and enter the uterine lumen  The Proliferative Phase The epithelial cells of the uterine glands multiply and spread across the endometrial surface Continuous growth and vascularization restores the integrity of the functional zone Simultaneously the primary and secondary follicles enlarge in the ovary and produce oestrogens which stimulate the events of this phase  The Secretory Phase Initiated at ovulation Endometrial cells enlarge and increase their rates of secretion Blood vessels supplying the uterine wall elongate and spiral through the tissues of the functional zone These activities are influenced by progestins and estrogens from the corpus luteum Phase lasts as long as corpus luteum remains intact  The Secretory Phase Secretory activities peak at about 12 days after ovulation Over next two days glandular activities decline Corpus luteum stops producing hormones and the uterine cycle ends. Menses then occurs The secretory phase lasts 14 days, therefore, the date of ovulation can be determined by counting backward 14 days from the first day of the menses  Hormones and the Female Reproductive Cycle GnRH regulates hormone production Follicular Phase (Days 1 – 13) – Menstruation occurs (Days 1 – 5) – One or more follicles start to develop (Days 6 -13); initiated by FSH – Oestrogen produced by follicle causes Inhibition of FSH LH production Growth and repair of uterine lining  Hormones and the Female Reproductive Cycle Follicular Phase (cont’d) Other functions of oestrogen – Stimulation of bone and muscle growth – Maintains secondary sex characteristics – Affects sex drive – Maintains functional accessory reproductive glands and organs Follicle increases in size at the end  Hormones and the Female Reproductive Cycle Ovulatory Phase (Day 14) – Oestrogen levels increase rapidly causing the release of high levels of LH and FSH – The sudden release of FSH causes the final development of the follicle – LH causes: Completion of meiosis I of primary oocyte Rupture of follicle wall ovulation – If the oocyte is not fertilized within 36 hours it dies  Hormones and the Female Reproductive Cycle Luteal Phase (Days 15 – 28) – LH causes follicular cells to develop into corpus luteum – Corpus luteum secretes some oestrogen and large amounts of progesterone – Progesterone causes: Mammary glands and uterus prepare for pregnancy In conjunction with oestrogen it inhibits FSH and LH production  Hormones and the Female Reproductive Cycle Luteal Phase (cont’d) – When FSH and LH levels fall the corpus luteum gets smaller and less progesterone and oestrogen are secreted – Low progesterone and oestrogen levels means FSH is no longer inhibited so cycle starts again  Hormones and the Female Reproductive Cycle If fertilisation occurs – Corpus luteum secretes sufficient oestrogen to support pregnancy and progesterone to maintain the uterine wall and sustain the developing embryo The corpus luteum is maintained by human chorionic gonadotropin (hCG) – Once the placenta develops it produces progesterone and oestrogen  Hormones and the Female Reproductive Cycle At the end of pregnancy progesterone levels fall and high oestrogen levels trigger the onset of labour  External Genitalia: Vulva (Pudendum) Lies external to the vagina and includes the mons pubis, labia, clitoris, and vestibular structures Mons pubis – round, fatty area overlying the pubic symphysis Labia majora – elongated, hair-covered, fatty skin folds homologous to the male scrotum Labia minora – hair-free skin folds lying within the labia major: homologous to the ventral penis External Genitalia: Vulva (Pudendum) Greater vestibular glands Pea-size glands flanking the vagina Homologous to the bulbourethral glands Keep the vestibule moist and lubricated Clitoris Erectile tissue hooded by the prepuce Homologous to the penis  Mammary Glands Modified sweat glands consisting of 15-25 lobes that radiate around and open at the nipple Areola – pigmented skin surrounding the nipple Suspensory ligaments attach the breast to underlying muscle fascia Lobes contain glandular alveoli that produce milk in lactating women Compound alveolar glands pass milk to lactiferous ducts, which open to the outside The Stages of Labour Dilation Fetal Expulsion Placental Expulsion  Dilation Stage 8 or more hours  Expulsion Stage Cervix is pushed open by approaching fetus Continues until fetus is totally expelled through vagina Lasts for up to 2 hours  Placental Stage Muscle tension builds in the uterus causing a reduction in size Connections between the endometrium and placenta tear Placenta is ejected accompanied by blood http://en.wikipedia.org/wiki/Childbirth