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Edit Comment Close Premium member Presentation Transcript Physiology of Reproduction : Physiology of Reproduction Sex Determination: Overview : Dimorphism: Males ? sperm Females ? eggs Chromosomes Autosomes Sex Chromosomes X - chromosome Y - chromosome Sex Determination: Overview Reproductive system : Reproductive system Sexual differentiation : genetic differentiation occurs with fertilization Ovum has 22+x chromosomes Sperm has 22+x/22+y chromosomes So chromosomal pattern can be female 44+xx chromosomes/male 44+xy chromosomes Sex determination : Sex determination Chromosomes : autosomes + sex chromosomes Human gametes : ova and sperm During gamete formation meiotic division occurs mature sperm and ova have haploid chromosomes : 23( 22 autosomes+ 1 sex chromosome) Sexual Differentiation: Internal Embryonic Development : Bipotential tissues: genes & hormones direct differentiation Gonad ? testis or ovary Wolffian duct ? Vas deferens, Mullerian duct ? oviduct Sexual Differentiation: Internal Embryonic Development Sexual Differentiation: Internal Embryonic Development : Sexual Differentiation: Internal Embryonic Development Sexual Differentiation: External Genitalia : Bipotential tissues: genital tubercle, urethral folds, urethral groove and labioscrotal swellings Sexual Differentiation: External Genitalia Sexual Differentiation: External Genitalia : Sexual Differentiation: External Genitalia Pathway for Sexual Development: Review for Genes to Organs : Pathway for Sexual Development: Review for Genes to Organs Slide 10: Human y chromosome has SRY region Barr body : Barr body After embryonic development one/the other of 2 x chromosomes of somatic cells become functionally inactive (the choice of x chromosome to become inactive is random. In case of normal cells in some somatic cells in adult females there is present an inactive x chromosome which condenses and can be seen in various types of cells near nuclear membrane as barr body called sex chromatin Drumstick like appearance Used for identification of sex genotype : cells used are epithelial cells of epidermal spinous layer. buccal mucosa, mucosal cells of vagina, PMN cells. Also used for identifying abnormal genotypes. Hormonal regulation of male development : Hormonal regulation of male development Mullerian inhibiting substance : produced by sertoli cells of fetal testis functions :-1. regression of mullerian duct 2. continued growth of wolffian duct 3. in later part of embryonic life causes descent of testis Testosterone : secreted by leydig cells of fetal testis in response to HCG functions :- 1. causes u/l virilization of wolffian duct into vas efferens,epididymus, vas deferens and seminal vesicle Continued…. : Continued…. 2. in other organs it is first converted to dihydrotestosterone to produce androgenic effects Dihydrotestosterone:- formed at site of action from testosterone in presence of enzyme 5a reductase functions :- causes masculization of prostate and external genitalia Disorders of sexual development : Disorders of sexual development Abnormalities occur due to defect in sex chromosomes and hormonal abnormalities Chromosomal abnormalities include:- Trisomy Monosomy Abnormalities with more than 3 chromosomes Triploidy Abnormalities in crossing over Mosaicism Trisomy and Monosomy : Trisomy and Monosomy Trisomy : Trisomy Sex chromosomes Human development more tolerant of wrong numbers in sex chromosome But produces a variety of distinct conditions in humans XXY = Klinefelter’s syndrome male XXX = Trisomy X female/ superfemale Klinefelter’s syndrome : Klinefelter’s syndrome XXY male one in every 2000 live births have male sex organs, but are sterile feminine characteristics tall normal intelligence Continued … : Continued … Gynaecomastia ( development of breast in males) Low level of testosterone Increase levels of LH and FSH High plasma level of oestradiol Positive sex chromatin test Monosomy : Monosomy Turner syndrome Monosomy X or X0 1 in every 5000 births varied degree of effects webbed neck short stature immature sterile females Turners syndrome : Turners syndrome Hormonal abnormalities : Hormonal abnormalities Fetal testes secrete testosterone required for male development but when genetic females exposed to androgens in 8th -13th wk. have male like development Disorders known as pseudohermaphroditism Pseudohermaphroditism : Pseudohermaphroditism Individuals having genotype of one sex and genitalia of the other sex. Female pseudohermaphroditism Male pseudohermaphroditism FEMALE PSEUDOHERMAPHRODITISM : FEMALE PSEUDOHERMAPHRODITISM EXCESS FETAL ANDROGENS Congenital adrenal hyperplasia 21 -hydroxylase deficiency 11-hydroxylase deficiency 3ß-hydroxysteroid dehydrogenase deficiency EXCESS MATERNAL ANDROGEN Maternal androgen secreting tumors (ovary, adrenal) Maternal ingestion of androgenic drugs Male pseudohermaphroditism : Male pseudohermaphroditism A genetic condition where affected people have male chromosomes & male gonads with complete or partial feminization of the external genitals An inherited X-linked recessive disease with a mutation in the Androgen Receptor (AR) gene resulting in: Functioning Y sex chromosome Abnormality on X sex chromosome Types CAIS (completely insensitive to AR gene)-External female genitalia -Lacking female internal organs PAIS (partially sensitive-varying degrees)-External genitalia appearance on a spectrum (male to female) MAIS (mildly sensitive, rare)-Impaired sperm development and/or impaired masculinization Also called Testicular Feminization True hermaphroditism : True hermaphroditism Rare condition gonads of both sexes are present (an ovary on one side and testis on the other side) resulting in numerous variations in phenotypic differentiations Puberty and adolescence : Puberty and adolescence Phases of growth between childhood and adulthood Defined as the period when endocrine and gametogenic functions of the gonads have first developed to a point where reproduction is possible. In girls the phases are :- thelarche - development of breasts pubarche - development of axillary and pubic hair menarche- first menstrual period MEAN AGE AT ADVENT OF MATURATIONAL EVENTS IN FEMALES : MEAN AGE AT ADVENT OF MATURATIONAL EVENTS IN FEMALES Pubic hair Breast budding Axillary hair Menarche Menstrual regularity Menstrual pain 11 12 Age in years 13 14 PUBERTAL STAGES (TANNER) FEMALE : PUBERTAL STAGES (TANNER) FEMALE P1Prepubertal P2Early development of subareolar breast bud +/-small amounts of pubic hair and axillary hair P3Increase in size of palpable breast tissue and areolae, increased amount of dark pubic hair and of axillary hair P4Further increase in breast size and areolae that protrude above breast level adult pubic hair P5Adult stage, pubic hair with extension to upper thigh PUBERTAL STAGES (TANNER) MALE : PUBERTAL STAGES (TANNER) MALE P1Prepubertal, testicular length less than 2.5cm P2Early increase in testicular size, scrotum slightly pigmented, few long and dark pubic hair P3Testicular length 3.3-4 cm, lengthening the penis, increase in pubic hair P4Testicular length 4.1-4.5cm, increase in length and thickening of the penis, adult amount of pubic hair P5Testicular length greater than 4.5cm, full spermatogenesis In case of males : In case of males Phases or stages are :- 1.pre adolescent stage (7.5 yrs) 2.genital development begins(12yrs) 3.axillary and pubic hair start appearing also enlargement of penis is there(14yrs) 4.further growth of testis ,penis and genitalia and sudden increase in height spurt(15yrs) 5.adult genitalia and secondary sexual characters(16.5yrs) CHRONOLOGICAL ASPECT : CHRONOLOGICAL ASPECT GIRLS acceleration of growth rate development of breasts and pubic hair Axillary hair menarche BOYS increase of testicular volume increase of penile length pubic hair increased growth rate Axillary hair deepening of the voice Control of onset of puberty : Control of onset of puberty Mainly hormonal:- 1. Gonadotrophins- pulsatile secretion of gonadotrophins brings on puberty. 2. Adrenal androgens- increase secretion at puberty 8-10 yrs in girls and 10-12 years in boys. Function is to cause growth of pubic and axillary hair and muscle mass strength. 3. Growth hormone- increased peaks at puberty 4. Thyroid gland secretions- also increase 5. Gonadal hormones- increase secretion. Endocrine Regulation : Negative feedback: Inhibits GnRH from hypothalamus. Inhibits anterior pituitary response to GnRH. Inhibin secretion inhibits anterior pituitary release of FSH. Female: Estrogen and progesterone. Male: Testosterone. Endocrine Regulation Continued.. : Continued.. Role of hypothalamus- increase pulsatile secretion of GnRH also it is sensitive to critical body mass, visual, external, olfactory and other sensory stimuli. Role of Leptin-There is good evidence that the hormone leptin is also involved. Leptin is a hormone released by adipose tissue. Circulating leptin levels may reflect total body fat storage by the body. In females, a certain minimum total-body fat content is required for puberty to progress and for maintenance of the menstrual cycle. Development of secondary sexual characteristics : Development of secondary sexual characteristics This usually coincides with the final maturation of the gonads. In humans, this is referred to as puberty. Mechanism controlling onset is unclear, but appears to involve the loss of inhibition of gonadal development. One potential candidate (at least in males) is melatonin. During childhood, melatonin is produced in the pars intermedia of the pituitary gland. Puberty disorders- early/precocious puberty or delayed puberty : Puberty disorders- early/precocious puberty or delayed puberty Precocious puberty- Early development of secondary sexual characteristics without gametogenesis is caused by abnormal exposure of immature males to androgen or females to estrogen. This syndrome should be called precocious pseudo puberty to distinguish it from true precocious puberty due to an early but otherwise normal pubertal pattern of gonadotropin secretion from the pituitary. Classification of the causes of precocious sexual development in humans. : Classification of the causes of precocious sexual development in humans. Precocious Puberty : Precocious Puberty Definition - Appearance of secondary sex characteristics before the age of 8 yrs in girls and 9 yrs in boys. • True or central precocious puberty due to the premature activation of hypothalamicpituitary-gonadal axis – Isosexual precocious sexual development. • Pseudoprecocious puberty: due to a secreting tumor inducing only the development of secondary sexual characteristics. • Partial or incomplete precocious puberty: premature adrenarche, premature thelarche. Delayed or absent puberty : Delayed or absent puberty The normal variation in the age at which adolescent changes occur is so wide that puberty cannot be considered to be pathologically delayed until the menarche has failed to occur by the age of 17 or testicular development by the age of 20. Causes can be:-1. failure of hypothalamus to secrete gonadotrophins 2. primary gonadal failure kleinfelters syndrome and turners syndrome 3. deficiency of enzymes for steroid synthesis 4. deficiency of specific receptors in the target tissues Menopause : Menopause The human ovaries become unresponsive to gonadotrophins with advancing age, and their function declines, so that sexual cycles disappear (menopause). This unresponsiveness is associated with and probably caused by a decline in the number of primordial follicles, which becomes precipitous at the time of menopause Total rates of secretion of gonadotropic hormones throughout the sexual lives of female and male human beings, showing an especially abrupt increase in gonadotropic hormones at menopause in the female : Total rates of secretion of gonadotropic hormones throughout the sexual lives of female and male human beings, showing an especially abrupt increase in gonadotropic hormones at menopause in the female Estrogen secretion throughout the sexual life of the female humanbeing. : Estrogen secretion throughout the sexual life of the female humanbeing. Symptoms of menopause : Symptoms of menopause Sensations of warmth spreading from the trunk to the face (hot flushes; also called hot flashes), night sweats, and various psychic symptoms are common after ovarian function has ceased, they are prevented by estrogen treatment. In addition, they occur after castration in men. Their cause is unknown. However, they coincide with surges of LH secretion. LH is secreted in episodic bursts at intervals of 30-60 minutes or more (circhoral secretion), and in the absence of gonadal hormones these bursts are large. Slide 45: Male Reproductive System TESTES: ONE PAIR : HAS SEMENIFEROUS TUBULES: SERTOLI CELLS SPERMATOGONIA SPERM CELLS IN VARIOUS STAGES INTERSTITIAL CELLS OF LEYDIG: SECRETE TESTOSTERONE, THE MALE REPRODUCTIVE HORMONE TESTES: ONE PAIR DUCTULAR SYSTEM : RETE TESTIS EFFERENT DUCTULES EPIDIDYMIS VAS DEFERENS FUNCTION: TRANSPORT OF MATURE SPERMATOZOA. DUCTULAR SYSTEM GLANDS : SEMINAL VESICLES PROSTATE GLAND: BOTH SECRETING SEMEN BULBO-URETHRAL GLANDS: SECRETE A MUCOID SUBSTANCE GLANDS Male reproductive system : Male reproductive system Three major subdivisions: (1) spermatogenesis which means simply the formation of Sperm (2) performance of the male sexual act; and (3) regulation of male reproductive functions by the various hormones. Slide 50: During formation of the embryo, the primordial germ cells migrate into the testes and become immature germ cells called spermatogonia which lie in two or three layers of the inner surfaces of the seminiferous tubules .The spermatogonia begin to undergo mitotic division, beginning at puberty, and continually proliferate and differentiate through definite stages of development to form sperm. Spermatogenesis I: : Spermatogenesis I: The immature germ cell in the male is referred to as the spermatogonium. These cells are located just under the basement membrane of the seminiferous tubules, between adjoining sustentacular (Sertoli) cells. Since sperm production continues throughout adult life and at the peak, 100-200 million sperm can be produced daily, the spermatogonia are constantly renewed. The first step in spermatogenesis is a mitotic division of the spermatogonium. One of the daughter cells remains, to replace the original spermatogonium, while the other cell (now called a primary spermatocyte) undergoes meiosis. Spermatogenesis : Spermatogenesis Spermatogonia: Replicate initially by mitosis. One of the 2 primary spermatocytes undergoes meiosis: 2 nuclear divisions: 1st meiotic division produces 2 secondary spermatocytes. 2nd meiotic division produces 4 spermatids. Slide 54: Cell divisions during spermatogenesis Spermatogenesis II: : Spermatogenesis II: The first meiotic division yields two secondary spermatocytes. Usually, these secondary spermatocytes do not fully separate during cell division, leaving a direct cytoplasmic connection between the cells. Following the second meiotic division (again, an incomplete division), the cells are known as spermatids. As the germ cells are undergoing meiosis, they also migrate towards the lumen of the seminiferous tubule. As they approach the lumen, they shed much of their cytoplasm. They are attached to the Sustentacular cells, via specialized junctions, which provide nutrients. When the spermatids reach the lumen, they remain embedded within the sustentacular cells, where they undergo tail development, acrosome formation and nuclear condensation. Finally, the fully-formed spermatozoa are shed into the lumen of the seminiferous tubule, where they are carried to the epididymus. This whole process takes between 60 and 70 days. Spermiogenesis : Maturation of spermatozoa. Phagocytosis of cytoplasm by the Sertoli cells. Cytoplasm is eliminated. Spermiogenesis Spermiogenesis : Spermiogenesis Spermatid undergo change in shape and orientation of organelles:- nucleus undergo condensation and forms head. golgi apparatus forms the acrosome mitochondria forms the tail part provide energy for movement Sertoli Cells : Sertoli Cells Form blood-testes barrier: Prevents autoimmune destruction of sperm. Produce FAS ligand which binds to the FAS receptor on surface to T lymphocytes, triggering apoptosis of T lymphocytes. Prevents immune attack. Secrete inhibin. Phagocytize residual bodies: May transmit information molecules from germ cells to Sertoli cells. Secrete androgen-binding protein (ABP): Binds to testosterone and concentrates testosterone in the tubules. Continued… : Continued… Secrete mullerian inhibiting substance Secrete seminiferous tubular luminar fluid:- secrete watery ,solute rich (k+ and HCO3-) fluid into the lumen. Structure of a spermatozoon : Structure of a spermatozoon 55-65 µm in length Three parts head, neck and tail. On the outside of the anterior two thirds of the head is a thick cap called the acrosome that is formed mainly from the Golgi apparatus. It contains enzymes similar to those found in lysosomes hyaluronidase and powerful proteolytic enzymes. These play important roles in allowing the sperm to enter the ovum and fertilize it. Continued.. : Continued.. The tail of the sperm, called the flagellum, has three major components: (1) a central skeleton constructed of 11 microtubules, collectively called the axoneme (2) a thin cell membrane covering the Axoneme (3) a collection of mitochondria surrounding the axoneme in the proximal portion of the tail (called the body of the tail). Back-and-forth movement of the tail (flagellar movement) provides motility for the sperm. This movement results from a rhythmical longitudinal. The energy for this process is supplied in the form of adenosine triphosphate that is synthesized by the mitochondria in the body of the tail. Normal sperm move in a fluid medium at a velocity of 1 to 4 mm/min. Hormonal control of spermatogenesis : Hormonal control of spermatogenesis Testosterone- essential for growth of germinal testicular cells Luteinizing hormone - stimulates the Leydig cells to secrete testosterone. Follicle-stimulating hormone -for conversion of the spermatids to sperm (the process of spermiogenesis). Estrogens –essential for spermiogenesis. Growth hormone (as well as most of the other body hormones) is necessary for controlling background metabolic functions of the testes. Male Accessory Organs : Male Accessory Organs Epididymis responsible for: Maturational changes. Resistance to pH changes and temperature. Storage of sperm between ejaculations. Ductus (vas) deferens: Carries sperm from epididymis into pelvic cavity. Seminal vesicles secrete: Fructose. Prostate secretes: Alkaline fluid. Citric acid. Ca2+. Coagulation proteins. Effect of temp. on spermatogenesis : Effect of temp. on spermatogenesis Spermatogenesis requires a temperature considerably lower than that of the interior of the body. The testes are normally maintained at a temperature of about 32 °C. Applied:- Cryptorchidism i.e. failure or incomplete descent of testes they may lie in the lumbar region , in the iliac fossa,in inguinal canal, or the upper part of scrotum. incidence 10% at birth which falls to 0.3% at puberty. Effects –spermatogenesis fails to occur in undescended testis . testosterone secretion is normal. more likely to develop malignant tumor. Treatment – surgical correction and also testosterone administration. Erection, Emission, and Ejaculation : Erection, Emission, and Ejaculation Erection: Controlled by hypothalamus and spinal cord. Increased vasodilation of arterioles. Parasympathetic nervous system. NO is the NT. Blood flow into the erectile tissues of the penis. Emission: Movement of semen into the urethra. Stimulated by sympathetic nervous system. Ejaculation: Forcible expulsion of semen from the urethra out of the penis. Stimulated by sympathetic nervous system. Semen : composition : Semen : composition Semen contains sperms and the secretions of the seminal vesicles, prostate, Cowper's glands, and, probably, the urethral glands. An average volume per ejaculate is 2.5-3.5 mL after several days of abstinence. Even though it takes only one sperm to fertilize the ovum, there are normally about 100 million sperms per milliliter of semen. Fifty percent of men with counts of 20-40 million/mL and essentially all of those with counts under 20 million/mL are sterile. The presence of many morphologically abnormal or immotile spermatozoa also correlates with infertility. Continued… : Continued… Appearance :- is milky due to prostate secretions Specific gravity :- 1.028 Reaction :- is alkaline pH 7.5 helps to bring vaginal pH from 3.5-6.5 which aids in sperm motility Coagulant nature when ejaculated but liquefies after 15-20mins. Secretions of seminal vesicles have fructose, phosphorylcholine,ergothionine ,ascorbic acid and prostaglandins. These provide nutrition to sperm and help in fertilization. Prostate gland secretions help in maintaining pH etc. Slide 68: The bulbourethral glands are paired glands that secrete a small amount of thick clear mucus. This secretion is released prior to ejaculation and is believed to neutralize traces of acidic urine in the urethra. The prostate gland is a single gland, which secretes about one third of the semen volume. It secretes a milky, slightly acidic fluid containing citrate, acid phosphatase and several proteolytic enzymes. These enzymes are probably involved in breaking down the mucus plug in the cervix. They also appear to contribute to the motility and viability of the sperm Sperm capacitance: : Sperm capacitance: Freshly ejaculated sperm are incapable of fertilizing an egg. As the sperm travel up the female reproductive tract, they lose cholesterol from their membranes When the sperm reach the fallopian tubes, the membranes around the acrosome are fragile enough to allow the release of the acrosomal enzymes. Male Fertility : Male Fertility 60-150 million sperm/ml ejaculate. Oligospermia: Sperm count of < 20 million/ml ejaculate. Decreased fertility caused by heat, pharmaceuticals, and illicit drugs. Male contraception: Compounds that suppress gonadotropin secretion. Testosterone. Progesterone and GnRH antagonist. Vasectomy: Each ductus deferens is cut and tied. Interferes with sperm transport. May develop anti-sperm antibodies. Testosterone : Testosterone Interstitial Cells of Leydig in the Testes. Androgens, including testosterone, dihydrotestosterone, and Androstenedione. Production of Estrogen in the Male. one fifth the amount in the nonpregnant Female. The exact source of estrogens in the male is unclear, but the following are known: the concentration of estrogens in the fluid of the seminiferous tubules is quite high and probably plays an important role in Spermiogenesis. This estrogen is believed to be formed by the Sertoli cells by converting testosterone to estradiol. Much larger amounts of estrogens are formed from testosterone and androstanediol in other tissues of the body, especially the liver. Control of testosterone secretion : Control of testosterone secretion Negative feedback: Testosterone inhibits LH and GnRH production. Maintain relatively constant secretion of LH and FSH. Declines gradually in men over 50 years of age. Testosterone converted to DHT, which inhibits LH. Inhibin inhibits FSH secretion Derivatives of Testosterone : Derivatives of Testosterone Endocrine Function of the Testes : Testosterone and its derivatives are responsible for initiation and maintenance of body changes in puberty. Stimulate growth of muscles, larynx, and bone growth until sealing of the epiphyseal discs. Promote hemoglobin synthesis. Act in paracrine fashion, responsible for spermatogenesis. Endocrine Function of the Testes Slide 75: 1. INITIATION & MAINTAINANCE OF SPERMATOGENESIS. 2. ? GnRH FROM THE HYPOTHALAMUS 3. INHIBITS LH SECRETION VIA ANTERIOR PITUITARY. 4. DIFFERENTIATION & MAINTAINANCE OF MALE SECONDARY SEXUAL CHARACTERISTICS:Facial Hair & Body Habitus. TESTOSTERONE - FUNCTIONS 5. INDUCES DIFFERENTIATION & MAINTAINS ACCESSORY REPRODUCTIVE ORGANS. 6. STIMULATES PROTEIN ANABOLISM, BONE GROWTH & IT’S CESSATION. 7. ENHANCES LIBIDO & AGGRESSIVE BEHAVIOUR BY MASCULINIZING THE BRAIN. 8. STIMULATES SECRETION OF ERYTHROPOIETIN FROM THE KIDNEYS Brain-testicular axis: : Brain-testicular axis: Applied aspects : Applied aspects Hypogonadism in males:- due to absent or deficient testicular functions Congenital nonfunctioning of testis Underdeveloped testis due to absence of HCG in fetal life Cryptochidism due to partial or total degeneration of seminiferous tubules Absence of androgen receptors in testis Hypogonadism… : Hypogonadism… Frohlich’s syndrome:- adipose genital syndrome or hypothalamic eunuchoidism this is hypogonadism which occurs due to hypothalamic disorders pituitary disorders genetic inability to secrete LHRH and GnRH Hypergonadism : Hypergonadism Due to excessive secretion of male sex hormones as in tumors of leydig cells. Features:- rapid growth of musculature and bones height is less due to early closure of epiphysis excessive development of sexual characters secrete estrogens which causes gynaecomastia Female reproductive system: : Female reproductive system: Female Reproductive Anatomy and Physiology: Overview : Ovary Fallopian tube Fimbriae Uterus Cervix Endometrium Vagina Clitoris Labia Female Reproductive Anatomy and Physiology: Overview Ovary: Details of Histology & Physiology : Follicle Oocytes Thecal cells Granulosa cells Estrogen ? Corpus luteum Corpus luteum Progesterone Inhibin Ovary: Details of Histology & Physiology Follicular Structure : Follicular Structure Physiology of female reproductive cycle : Definition The cycle of physiological changes in the ovaries, cervix and endometrium under the influence of female sex hormones. Consist of:- ovarian cycle menstrual cycle Physiology of female reproductive cycle Ovarian Cycle-preovulatory phase : 5 mo. gestation, ovaries contain 6-7 million oogonia. Oogenesis arrested in prophase of 1st meiotic division (primary oocyte). Begins at 15 weeks and at peak at 20 to 28 wk. of gestation Apoptosis occurs: 2 million primary oocytes at birth. 400,000 primary oocytes at puberty. 400 oocytes ovulated during the reproductive years. Ovarian Cycle-preovulatory phase Slide 88: Ovarian Cycle :- oogenesis Egg forming cells (oöcytes) go through two divisions 1º = primary 2º = secondary Starts with a 2n=46 1ºoöcyte that divides, resulting in two n=23 cells, but one is a large 2º oöcyte and one is a small 1st polar body that may itself divide Second division only occurs if 2º oöcyte is fertilized. Results in one large n=23 ovum (egg) and one small n=23 2nd polar body Thus oögenesis results in one large fertilized egg (zygote) and possibly three small polar bodies Oogenesis vs Spermatogeneis : Oogenesis vs Spermatogeneis Oogenesis Female cannot form oogonia beyond 28 wks and must function with decreasing pool of oocytes Meiosis in females cause foramtion of one viable oocyte Spermatogenesis Spermatogonia are produced throughout life Each primary spermatogonia gives rise to 64 spermatozoa The Ovary : The Ovary Pair of organs, size of unshelled almonds in upper pelvic region Histology -Capsule of dense CT Cortex just deep to capsule contains follicles with egg cells (oöcytes) Medulla is middle region composed of connective tissue, blood vessels & lymphatics Germinal epithelium is peritoneal membrane covering the ovary Capsule Capsule Ovarian Follicles : Ovarian Follicles Oöcytes (egg cells) develop within follicles Stages of follicular development Primordial follicle Single layer of squamous cells around the oöcyte Primary follicle Layers of cuboidal granulosa cells around the oöcyte Granulosa cells secrete estrogens Ovarian follicle : Ovarian follicle Primary follicle:-granulosa cells flat form stratum granulosum after mitosis Secondary folicle:-granulosa cells further proliferate. Theca folliculi proliferate form theca interna and theca externa theca interna is secretory. Tertiary follicle:- theca cells become steroidogenic upto this stage the fllicular growth is stimulated by FSH alone. Ovarian cycle : Ovarian cycle Secondary follicle Antral cavity forms Graafian follicle Follicle mature ready to ovulate oöcyte Ovulation Follicle ruptures releasing oöcyte Ovarian Follicle : Ovarian Follicle Graffian follicle:-at about 7th day the follicle increases in size , antrum becomes larger with fluid , theca interna is more prominent just prior to ovulation completion of the first meiotic division of the primary oocyte of the graffian follicle to form the secondary oocyte and the first polar body. Ovarian Cycle:- folliculogenesis : Secondary oocyte confined to graafian follicle. Arrested at metaphase II. ( mature only if fertilized by a sperm, at that time 2nd polar body is extruded) Under FSH stimulation: Theca cells secrete testosterone. Granulosa cells contain the enzyme aromatase to convert testosterone into estrogen. Granulosa cells form a ring (corona radiata) around oocyte and form mound (cumullus oophorus). Between oocyte and corona radiata is zona pellucida. Provides barrier to the sperm to fertilize the egg. Ovarian Cycle:- folliculogenesis Ovulation : One graafian follicle forms bulge on surface of ovary. Extrudes secondary oocyte into the uterine tube. LH causes the empty follicle to become corpus luteum which secretes: Progesterone and estrogen. If not fertilized, becomes corpus albicans. Ovulation Ovulation : Ovulation Refers to release of the secondary oocyte from the ovary usually occurs 14 days after onset of menstruation There is rapid swelling of graffian follicle Formation of stigma Release of proteolytic enzymes Dissolution of the capsular wall Rupture of the follicle Determination of ovulation time : Determination of ovulation time Basal body temperature:- falls slightly 0.3 – 0.5ºC and increases after ovulation. Hormone excretion in urine:-excretion of end products of estrogens increase at peak at time of ovulation and end products of progesterones after ovulation Hormone levels in the plasma:- LH and estrogens are increased and FSH levels are decreased at time of ovulation and progesterone level increase at time of ovulation Ultrasound scanning Corpus Luteum : Corpus Luteum After ovulation, empty follicle becomes a corpus luteum Corpus Luteum secretes:- Progesterone – completes the preparation of uterine lining Estrogens – work with progesterone Relaxin – relaxes uterine muscles and pubic symphysis Inhibin – decreases secretion of FSH and LH Corpus albicans is a white scar tissue left after the corpus luteum dies. Summary of ovarian cycle : Summary of ovarian cycle Ovarian cycle is divided into four phases Development of follicles primitive follicles?primary follicles ? secondary follicles ? antrun/ developing follicles ? maturity follicles ovulation corpus luteum corpus albican Ovarian cycle : Ovarian cycle Follicular Phase : Lasts from day 1 to about 13. FSH: Follicles become increasingly sensitive to FSH. FSH stimulates the production of FSH receptors on the granulosa cells. Toward the end of the phase, sensitivity of FSH receptors increases. FSH and estradiol stimulate production of LH receptors in graafian follicle. Rapid rise in estradiol from granulosa cells. Negative feedback on LH and FSH. Follicular Phase Slide 103: Follicular Phase (continued) Hypothalamus increases frequency of GnRH pulses. Augments the ability of anterior pituitary to respond to GnRH, to increase LH secretion. Positive feedback: LH surge begins 24 hours before ovulation. Triggers ovulation. FSH increase stimulates development of new follicles. Slide 104: Control of Ovarian function - Early and Middle follicular phase Luteal Phase : LH stimulates formation of the empty follicle into corpus luteum. Corpus luteum secretes: Progesterone: Plasma concentration rapidly rises. Exerts negative feedback on LH and FSH. Inhibin: Suppresses FSH secretion. Inhibin production decreases towards end of luteal phase. Luteal Phase Luteal Phase (continued) : Corpus luteum regresses unless fertilization occurs: Estradiol decreases. Progesterone decreases. Withdrawal of estradiol and progesterone cause menstruation to occur. Luteal Phase (continued) Slide 107: Control of Ovarian function – Late Follicular Phase (LH Surge) Slide 108: Hormonal levels – Ovarian events Slide 111: FEMALE REPRODUCTIVE SYSTEM ? UTERUS ENDOMETRIUM TWO LAYERS: undergoes cyclic changes which prepare it for implantation of a fertilized ovum (1) FUNCTIONAL LAYER (stratum functionalis) (2) BASAL LAYER (stratum basale) - BORDERS UTERINE LUMEN - SLOUGHED OFF AT MENSTRATION - RETAINED AT MENSTRATION - SOURCE OF CELLS FOR REGENERATION OF FUNCTIONAL LAYER - CONTAINS UTERINE GLANDS STRAIGHT AND SPIRAL ARTERIES Endometrial cycle : Endometrial cycle Stages of uterine cycle : Stages of uterine cycle The proliferative phase (estrogen phase), occurs before ovulation Secretory phase (progesterone phase) ,occurring after ovulation Desquamation of endometrium known as menstruation Proliferative phase (estrogen phase) : Proliferative phase (estrogen phase) At start of each cycle endometrium has been desquamated under influence of estrogens the stromal and the epithelial cells proliferate reepithelialized in 4-7 days during next one week justbefore ovulation occurs—the endometrium increases greatly in thickness, owing to increasing numbers of stromal cells and to progressive growth of the endometrial glands and new blood vessels into the endometrium. At the time of ovulation, the endometrium is 3 to 5 millimeters thick. Changes in cervix in proliferative phase : Changes in cervix in proliferative phase The cervical glands secrete thin stringy mucus these strings align along length of the canal and help to guide the sperm in proper direction in the female tract Secretory phase(progesterone phase) : Secretory phase(progesterone phase) During the latter half after ovulation progesterones and estrogens both are secreted from corpus luteum P causes the secretory changes and marked swelling in the endometrium, increasing the tortuosity of the glands cytoplasm of the stromal cells increases , blood supply increases. At the peak of secretory phase the thickness of the endometrium is 5-6 mm.The purpose of all these endometrial changes is to produce a highly secretory endometrium that contains large amounts of stored nutrients to provide appropriate conditions for implantation of a fertilized ovum during the latter half of the monthly cycle Menstruation : Menstruation If no fertilization occurs about 2 days before the end of each cycle the corpus luteum involutes and the levels of E and P decrease. The endometrium becomes thinner. Foci of necrosis appear in the endometrium, and these coalesce. There is in addition spasm and then necrosis of the walls of the spiral arteries, leading to spotty hemorrhages that become confluent and produce the menstrual flow. There is vasospasm is probably produced by locally released prostaglandins.during normal menstruation about 40 ml of blood is lost and an additional 35 ml of serous fluid is lost. There is fibrinolysin in the fluid so it is non coagulating Cyclic changes in the cervix (cervical cycle( : Cyclic changes in the cervix (cervical cycle( The cervical sphincter is tighter and more competent during the luteal than during the follicular phase. Follicular phase: Gland: epithelium taller columnar. Cervical mucus: stretch into threads at time of ovulation (Spinnbarkeit test) Absorb more water & salts and when allowed to dry, crystals of Na Cl & K Cl deposits in characteristic pattern (fern pattern( Cyclic changes in the cervix (cervical cycle) : Cyclic changes in the cervix (cervical cycle) At time of ovulation: Profuse secretion (ovulation cascade) ? easily penetrated by spermatozoa. Luteal phase: Glands: more branched. Mucus: more viscous & forms a cervical plug, looses its ability to stretch without breaking and resist sperm penetration. NB: cervical mucous is scanty, viscid, less cellular with negative ferning & spinnbarkait Cyclic changes in the vaginal epithelium : Cyclic changes in the vaginal epithelium Anovulatory Cycles : Anovulatory Cycles Ovulation will not occur - surge of LH is not of sufficient First few cycles after the onset of puberty. cycles occurring several months to years before menopause. Slide 124: Basal body temperature Plasma oestradiol Plasma progesterone Volume of cervical mucus – and sperm penetration Uterine endometrium Ovarian Hormones : Ovarian Hormones Estrogens (oestrogens) & progestins important of the estrogens is the hormone b-estradiol, other derivatives of estrogen are estrone and estriol important progestin is progesterone. other are progestin,17 a-hydroxyprogesterone. Estrogens : Estrogens Non-pregnant female - only from the ovaries. During pregnancy - also from placenta. 3 estrogens - b-estradiol, estrone, & estriol. Main estrogen by the ovaries - b-estradiol. Estriol – weak estrogen. oxidative product of estradiol and estrone. conversion in the liver. Estrogens metabolism : Estrogens metabolism 2% free and remainder is bound 60% to albumin, 38% to gonadal steroid-binding globulin Liver conjugates and form glucuronides and sulfates. Diminished liver function – increases activity of estrogens. Progestins : Progestins Important of progestins – progesterone Significant amounts only during the latter half of each ovarian cycle. Large amounts from the placenta in pregnancy - after fourth month of gestation. Progestins metabolism : Progestins metabolism 2% free and remainder is bound 80% to albumin, 18% to corticosteroid binding globulin Liver conjugates and form glucuronides. Has short half life. Mechanism of estrogen action : Mechanism of estrogen action Free estradiol ? enters the cells and diffuse into the nucleus. The specific estrogen receptor protein are intranuclear. The steroid-receptor complex interacts with nuclear DNA ?hormone message to nuclear gene structure ?production of a messenger RNA, which is transported to cytoplasmic ribosomes where it leads to protein synthesis and the cellular response characteristic of estrogen responsive cells Slide 131: Estogen mechanism of action Functions of the estrogens : Functions of the estrogens Secondary sex characteristics Increase size of ovaries, fallopian tubes,uterus, and vagina. External genitalia enlarge - deposition of fat in the mons pubis and labia majora, enlargement of the labia minora. Functions of the estrogens : Functions of the estrogens Vaginal epithelium - from a cuboidal into a stratified type. Stimulate endometrial growth. Fallopian tubes - glandular tissues proliferate. Breast development of the stromal tissues, growth of an extensive ductile system, deposition of fat. Functions of the estrogens : Functions of the estrogens Stimulate bone growth – inhibit osteoclastic activity in the bones. accelerate metabolism (burn fat)but only on ethird as that of testosterone reduce muscle mass maintenance of vessel Skin texture - soft and usually smooth Functions of the estrogens : Functions of the estrogens Protein synthesis Increase hepatic production of binding proteins slight increase in total body protein. evident by positive nitrogen balance seen on giving estrogens Lipid Increase fat depositition in the subcutaneous tissues Sodium and water retention Functions of Progesterone : Functions of Progesterone Most important function – promote secretory changes in endometrium. Increased mucosal secretion of fallopian tubes. Breasts - development of lobules and alveoli and become secretory in nature. Hypothalamic-Pituitary ovaryaxis : Hypothalamic-Pituitary ovaryaxis GnRH secretes in pulses lasting 5 to 25 minutes - every 1 to 2 hours. Limbic system has control over -intensity & frequency of the pulses. Estrogen has a strong effect to inhibit the production of LH & FSH Hypothalamic-Pituitaryovaryaxis : Hypothalamic-Pituitaryovaryaxis Inhibitory effect of estrogen is multiplied when progesterone is available. But progesterone itself has little effect. Inhibin ( from granulosa cells) has feedback effects on pituitary. Female Sexual Response: : Female Sexual Response: As with Males, arousal is controlled by parasympathetic stimulation. Involves engorgement of the erectile tissues. Increased bloodflow to the external genitalia and vaginal walls. Stimulation of secretion of cervical mucous glands and greater vestibular glands. Female Sexual Response (cont.): : Female Sexual Response (cont.): Rhythmic contact of the clitoris and vaginal walls, reinforced by touch sensations from the breasts and other stimuli, can lead to orgasm. As with male climax, female climax results in rhythmic peristaltic contractions of the uterus and vaginal walls and associated skeletal muscles. This is thought to enhance the migration of sperm up the female reproductive tract. Female climax is NOT required for fertilization. Fertilization and pregnancy: : Fertilization and pregnancy: Fertilization : Fertilization In humans, fertilization of the ovum by the sperm usually occurs in the ampulla of the uterine tube. Fertilization involves (1) chemo attraction of the sperm to the ovum by substances produced by the ovum (2) adherence to the zona pellucida, the membranous structure surrounding the ovum (3) penetration of the zona pellucida and the acrosome reaction (4) adherence of the sperm head to the cell membrane of the ovum, with breakdown of the area of fusion and release of the sperm nucleus into the cytoplasm of the ovum. Slide 143: Ejaculation 300 million sperm, 100 reach (uterine) fallopian tube. Capacitation occurs. Fertilization occurs in the uterine tubes. Acrosome of sperm contains hyaluronidase, an enzyme that digests a channel through zona pellucida. Sperm fuses with ovum cell membrane. Fertilization Blocks to polyspermy : Blocks to polyspermy If more than one sperm were to fertilize the egg, then the genetic complement would be 3n. In order to prevent multiple sperm penetrations, two responses have evolved in the egg. First, as soon as the first sperm head penetrates the egg, it triggers a massive influx of Na+. This influx depolarizes the egg, making it positive inside. This repels the positively charged sperm, inhibiting penetration of more sperm. Slide 146: Second, the depolarization triggers an influx of Ca 2+ . This Ca 2+ facilitates the exocytosis of a number of secretory vesicles, known as cortical vesicles. The contents of these vesicles surrounds the egg, swells with water and gels, pushing other sperm away from the egg and blocking their entry. Slide 147: As fertilization occurs, secondary oocyte completes 2nd meiotic division. Sperm enters ovum cytoplasm. Ovum nuclear membrane disappears, zygote formed. Centrosome of zygote is derived from sperm cell. Fertilization (continued) Cleavage and Blastocyst Formation : Cleavage: 30-36 hrs. after fertilization, the zygote divides by mitosis. About 50-60 hours after fertilization, the early embryo develops into morula. Blastocyst develops: Inner cell mass Fetus. Surrounding chorion: Trophoblasts form placenta. Cleavage and Blastocyst Formation Slide 149: 6th day after fertilization, blastocyst attaches to uterine wall. Trophoblast cells produce enzymes that allow blastocyst to burrow into endometrium. Implantation Fertilization: : Fertilization: Slide 152: Only fertilized egg cells and early cleavage cells are totipotent: Ability to create the entire organism. Reproductive cloning: Adult stem cells can become totipotent if transplanted into egg cell cytoplasm. Therapeutic cloning: Nucleus transplantation to produce stem cells for purpose of growing specific tissue for the treatment of disease. Pluripotent: Cells obtained from inner cell mass of blastocyst (embryonic stem cells) can give rise to all tissues except the placenta. Multipotent: Can give rise to a number of differentiated cells. Embryonic Stem Cells and Cloning PREGNANCY BEGINS : THIS RESULTS IN THE ONSET OF A NINE-MONTH RELATION SHIP BETWEEN THE EMBRYO-FETUS, AND THE MOTHER. THIS PHYSIOLOGICAL STATE IS CALLED PREGNANCY. IT IS DIVIDED INTO THREE TRIMESTERS OF THREE MONTHS EACH. PREGNANCY BEGINS FETO PLACENTAL UNIT : FETO PLACENTAL UNIT CHOLESTEROL PREGNENOLONE PROGESTERONE DHEAS 16-OH- DHEAS CORTISOL & CORTICOSTERONE DHEAS 16-0H-DHEAS ESTRADIOL ESTRIOL PLACENTA FETAL ADRENAL TESTS OF PREGNANCY : 1. ASCHEIM ZONDEK TEST 2. FRIEDMAN TEST 3. GALLI-MAININI TEST 4. IMMUNOLOGICAL TESTS a) SHEEP RBC AGGLUTINATION b) LATEX PARTICLE AGGLUTINATION c) GRAVINDEX TEST TESTS OF PREGNANCY 1. ASCHEIM ZONDEK TEST : URINE FROM THE WOMAN IS INJECTED INTO IMMATURE MICE 0.5 ml b.d FOR THREE DAYS ON THE FIFTH DAY THE MICE ARE SACRIFICED. THEY ARE DISSECTED TO LOOK FOR CORPUS HEMORRHAGICUM. IF IT IS THERE, THE WOMAN IS PREGNANT. 1. ASCHEIM ZONDEK TEST 2. FRIEDMAN TEST : 10 -15 ml OF THE WOMANS URINE IS GIVEN I.V TO A MATURE FEMALE RABBIT. THE RABBITS OVARIES ARE EXAMINED AFTER 24/48 HRS FOR EVIDENCE OF OVULATION. RABBITS HAVE REFLEX OVULATION. 2. FRIEDMAN TEST 3. GALLI – MAININI TEST : A SIMPLE AND INEXPENSIVE TEST. 5 ml OF THE WOMAN’S URINE IS PUT INTO THE DORSAL LYMPH SAC OF A MALE TOAD. 1-2 HRS LATER, IT’S CLOACAL FLUID IS EXAMINED FOR SPERMATOZOA. 3. GALLI – MAININI TEST Slide 159: MOSTLY BEING USED THESE DAYS. BASIS: REACTION BETWEEN ANTIGENS AND ANTIBODIES OF HUMAN CHORIONIC GONADOTROPHIN (HCG) HCG ANTIBODIES ARE PRODUCED FROM RABBITS 4. IMMUNOLOGICAL TESTS Slide 160: a) SHEEP RBC AGGLUTINATION TEST: Sheep RBCs are coated with the antibodies. They get agglutinated when exposed to urine containing HCG. b) LATEX PARTICLE AGGLUTINATION. c) GRAVINDEX TEST: Most commonly used test today. 4. IMMUNOLOGICAL TESTS Slide 161: GRAVINDEX: HCG TEST KIT Slide 162: CNS: I Trimester: Excitement Depression Irritability II Trimester: Euphoria: a sense of ‘well being’ III Trimester: Worries and anxieties PHYSIOLOGICAL CHANGES IN PREGNANCY Slide 163: BLOOD VOLUME INCREASED BY 25% HEMODILUTION. ANEMIA CARDIAC OUTPUT INCREASED BY 30% PULSE RATE INCREASED. PERIPHERAL RESISTANCE DECREASES BP IS MAINTAINED NORMAL. CHANGES IN CARDIOVASCULAR SYSTEM CHANGES IN GASTROINTESTINAL SYSTEM : MORNING SICKNESS: HYPEREMESIS GRAVIDARUM CONSTIPATION HEARTBURN ? ACIDITY DUE TO ?LES TONE CHANGES IN GASTROINTESTINAL SYSTEM CUTANEOUS CHANGES : INCREASED PIGMENTATION PURPLE STRIA: STRIAE GRAVIDARUM RENAL CHANGES INCREASED FREQUENCY. SLIGHT ALBUMINURIA. SODIUM & WATER RETENTION. CUTANEOUS CHANGES CHANGES IN RESPIRATORY SYSTEM : ? TIDAL VOLUME. ? PULMONARY VENTILATION OXYGEN UTILISATION INCREASES. BLOOD CHANGES ? ERYTHROCYTE SEDIMENTATION RATE. ? COLLOID ONCOTIC PRESSURE EDEMA LOSS OF 1/8th TO 1/10th IRON. CHANGES IN RESPIRATORY SYSTEM CHANGES IN ENDOCRINES : HYPOTHALAMO-HYPOPHYSIAL AXIS STOPPED. HCG TAKES OVER. CORPUS LUTEUM AND PLACENTA BECOME MAJOR ENDOCRINE GLANDS PRODUCING ESTROGENS & PROGESTERONE. INCREASED LEVELS OF: PTH, CORTISOL, PROLACTIN & OXYTOCIN. CHANGES IN ENDOCRINES CHANGES IN METABOLISM : BMR INCREASED BY 25%. WEIGHT GAIN: 12.5 kg. POSITIVE CALCIUM BALANCE. PROTEIN ANABOLISM POSITIVE NITROGEN BALANCE. HYPER GLYCEMIA INABILITY TO TOLERATE FASTING. CHANGES IN METABOLISM CHANGES IN MAMMARY GLANDS : BREASTS ARE ENLARGED. THE AREOLA AND NIPPLES ARE DARKENED & SWOLLEN. CHANGES IN MAMMARY GLANDS Slide 170: PROFOUND CHANGES OCCUR. UTERUS INCREASES IN WEIGHT & SIZE. BOTH HYPERPLASIA & HYPERTROPHY OCCUR OF BOTH ENDO & MYOMETRIA. WEAK CONTRACTIONS OCCUR IN THE UTERUS CHANGES IN REPRODUCTIVE ORGANS CHANGES IN REPRODUCTIVE ORGANS contd. : CERVIX BEGINS TO SOFTEN. OVARIES: NO OVULATION CORPUS LUTEUM OF PREGNANCY INCREASES IN SIZE WITHIN THE OVARY. VAGINA BECOMES HYPERVASCULAR. MUCOSA BECOMES PURPLISH ? ACIDITY IN THE VAGINA. CHANGES IN REPRODUCTIVE ORGANS contd. Implantation: : Implantation: Chorionic villi : Chorionic villi Placenta : Syncytiotrophoblast secretes enzymes that create blood filled cavities in the maternal tissue. Cytotrophoblast then forms villi that grow into the pools of venous blood. Produces chorion frondosum on the side that faces the uterine wall. Other side of chorion bulges into the uterine cavity. Placenta Placenta : Placenta Fully formed placenta is a disc shaped structure with diameter of 15-20 cm and weighs 500gms. Placental membrane consist of :- endothelium of the fetal blood vessels and its basement membrane connective tissue cytotrophoblast and its basement membrane syncytiotrophoblast Slide 184: Decidual reaction: Endometrial growth. Accumulation of glycogen. Decidua basalis: Maternal tissue in contact with the chorion frondosum. Decidua basalis and chorion fondosum together become placenta. Maternal and fetal blood do not mix. Formation of the Placenta and Amniotic Sac Slide 185: Envelop the embryo and umbilical cord. Amniotic fluid initially is isotonic, but as fetus develops; concentration changes by urine and sloughed cells of the fetus, placenta, and amniotic sac. Amnion Placental hormones: : Placental hormones: During early pregnancy, HCG is secreted by the syncitial trophoblasts. Later, the placenta secretes estradiol, progesterone, relaxin and somato-mammotropin. Slide 187: hCG (Human Chorionic Gonadotropin) Trophoblast cells secrete hCG: Signals corpus luteum not to degenerate until placenta secretes adequate [hormones]. Prevents immunological rejection of implanting embryo. Has thyroid-stimulating ability. Produces effects similar to LH. Basis of pregnancy test. Function of placental hormones: : Function of placental hormones: HCG is similar to LH and maintains the corpus luteum in a functional state for 3-4 months. This keeps progesterone levels high and they maintain the functional endometrium. Relaxin increases flexibility in the pelvic joints, as well as suppressing release of oxytocin. Placental progesterone keeps the uterine wall intact. Somatomammotropin acts like prolactin and triggers the mammary glands to develop. Estrogen increases the sensitivity of the myometrium to mechanical irritation, as well as oxytocin stimulation. Placental Hormones : hCS (chorionic somatomammotropin): secretion begins at 5th wk of pregnancy(plasma concentration is proportional to activity of placenta) Actions similar to GH. Actions similar to prolactin. hCS and GH cause diabetic-like effect: Glucose sparing effects by maternal tissues. Ensure sufficient supply of glucose for placenta and fetus. Polyuria. Lipolysis. Placental Hormones Placental Hormones (continued) : Fetal-placental unit: Placenta must cooperate with the adrenal cortex in the fetus to produce estrogen. Estrogen/estriol stimulates: Endometrial growth. Inhibition of prolactin secretion. Growth of mammary ducts. Enlargement of mother’s uterus. Placental Hormones (continued) Placental Hormones (continued) : Progesterone: Suppresses uterine contractions. Stimulates uterine growth. Suppresses LH and FSH. Stimulates development of alveolar tissue of the mammary gland. Placental Hormones (continued) Placenta Function : Site for exchange of gases and other molecules between maternal and fetal blood. Gas exchange: 02 and C02. Nutrient exchange. Waste exchange. Synthesis of proteins and enzymes. Placenta Function Parturition : Estrogen in late pregnancy: Stimulates production of oxytocin receptors in myometrium. Produces receptors for prostaglandins. Produces gap junctions between myometrium cells in uterus. Factors responsible for initiation of labor are incompletely understood. Parturition Slide 194: Parturition (continued) Parturition (continued) : Fetal adrenal cortex: Chain of events may be set in motion through CRH production. Fetal adrenal zone secretes DHEAS, which travel from fetus and placenta. Uterine contractions: Oxytocin. Prostaglandins. Parturition (continued) Labour: : Labour: Towards the end of pregnancy, relaxin secretion falls off, thus, the uterus becomes more sensitive to oxytocin. Initially, the fetus secretes oxytocin into the maternal circulation. The oxytocin stimulates contractions, which push the head down against the cervix. Slide 197: This pressure on the cervix stimulates the release of oxytocin from the maternal pituitary gland. The maternal oxytocin causes more contractions of the uterus, forcing the head of the fetus against the cervix even harder. This is a positive feedback system. Labour and delivery: : Labour and delivery: As the head of the fetus is pressed down against the cervix, it thins and then starts to dilate. This stage is known as the Dilation Stage and can last several hours, or days (usually around 8 hours). Once the cervix has dilated, the fetus starts moving through the birth canal. Contractions are maximal and come about 2-3 minutes. This is known as the Expulsion Stage. If the vaginal wall has not stretched enough, tearing may occur. Labour and delivery cont. : : Labour and delivery cont. : There is also a chance that the fetus will get stuck in the birth canal (usually caused by insufficient molding of the head. In these cases, a cesarean section is performed. Finally, after expulsion of the fetus, the placenta detaches from the uterine wall and is delivered through the birth canal. This is known as the Placental Stage. Lactogenesis : Lactogenesis Phases are:- 1.preparation of breast for milk secretion (mammogenesis) 2.Synthesis and secretion of milk ( lacto genesis) 3.Expulsion of milk ( galactokinesis) 4.Maintainance of lactation (galactopoiesis) Lactogenesis : Lactogenesis Stage 1:- in later weeks of pregnancy there is secretion of colostrum rate is only 1/100th of that of secretion of milk it occurs due to high levels of prolactin and HCS Stage 2 :- occurs after the baby is born due to loss of the estrogens and progesterone thus allowing the lactogenic secretion of prolactin to take place secretion rate is 500- 750 ml/day Human milk composition : Human milk composition Human milk has 88.5% water and 11.5% solids. solids have both organic and in organic components it contains 1.proteins: 1-2 gm% 2. Carbohydrates ( lactose) : 6.5-8.5gm% 3. Fats 3.0-5.0 gm% 4. Calcium .03 gm% 5. Minerals 0.18-0.25 gm% Expulsion of milk: suckling reflex : Expulsion of milk: suckling reflex Two hormones are involved, PRL and oxytocin. PRL stimulates milk production, while oxytocin is required for the expression of milk from the breast. Lactation : Hypothalamus releases PRH. Anterior pituitary releases prolactin: Stimulates milk production. Prolactin secretion primarily controlled by PIH. Oxytocin needed for “milk letdown.” Lactation Lactation (continued) : Mammary gland: Lobules contain glandular alveoli that secrete milk of the lactating female. Alveoli secrete milk into secondary tubule that converge to form mammary duct. Ampulla: Where milk accumulates during nursing. Neuroendocrine reflex: Act of nursing maintains high levels of prolactin. Sucking may cause release of PRH. Lactation (continued) Prolactin secretion : Prolactin secretion Milk-Ejection Reflex : Milk-Ejection Reflex Fertility issues: : Fertility issues: You do not have the permission to view this presentation. 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