CHP 8 REPRODUCTION AND DEVELOPMENT (Biology PDF)

CHP 8: Reproduction & Development FSPB 0034 BIOLOGY NOORHASYIMAH ISMAIL Content 8.1 Sexual Reproduction in Flowering Plants 8.2 Human Reproductive System 8.3 Fertilization & Foetal Development 8.4 Roles of Hormones During Pregnancy & Parturition  8.1 Sexual Reproduction in Flowering Plan...

CHP 8: Reproduction & Development FSPB 0034 BIOLOGY NOORHASYIMAH ISMAIL Content 8.1 Sexual Reproduction in Flowering Plants 8.2 Human Reproductive System 8.3 Fertilization & Foetal Development 8.4 Roles of Hormones During Pregnancy & Parturition  8.1 Sexual Reproduction in Flowering Plants LEARNING OBJECTIVES By the end of this topic, students should be able to: 1. State and define the terminologies involved in gamete formation in flowering plants.  8.1 Sexual Reproduction in Flowering Plants 8.1.1 Introduction Process by which new individuals of a species are produced from current generation. New individuals The genetic produced are materials are important to transferred ensure the from one continuity of the REPRODUCTION generation to species. another. Types of For survival of reproduction: future generation of - Asexual a species/ avoid - Sexual from extinction.  8.1 Sexual Reproduction in Flowering Plants 8.1.1 Reproductive organ in angiosperms In angiosperms, they produce a unique reproductive organ ® FLOWER  8.1 Sexual Reproduction in Flowering Plants 8.1.1 Reproductive organ in angiosperms Angiosperm? Non flowering plant?  8.1 Sexual Reproduction in Flowering Plants 8.1.1 Reproductive organ in angiosperms Ovary: contains General Structures of Flower one or more ovules Stigma Style: is a Anther tubular structure Stamen that extends Filament Style from the ovary Anther: has sac containing pollen Carpel which produce / Pistil pollen grains Stigma: sticky Filament: a thin Petal surface that stalk that holds (Petals=Corolla) serves as a the anther up Sepal Ovary landing platform (Sepals=Calyx) Ovule for pollen Receptacle  8.1 Sexual Reproduction in Flowering Plants 8.1.1 Reproductive organ in angiosperms General Structures of Flower Flower is attached to the stem by receptacle Complete flower has all 4 organs: Sepals Non-reproductive organ Petals Carpels Female reproductive organ Stamens Male reproductive organ Incomplete flower lack 1 or more floral organs  8.1 Sexual Reproduction in Flowering Plants 8.1.2 Terminologies in Male Reproductive Parts Terminologies Definition 1. Microsporangium v One of the chambers of an / pollen sac anther (or a male cone) in which pollen is produced 2. Microsporocyte / v A diploid cell in microspore mother microsporangium that divide by cell meiosis to give rise to 4 haploid microspores 3. Microspore v A small haploid spore from a heterosporous plant species that develops into pollen grain / male gametophyte  8.1 Sexual Reproduction in Flowering Plants 8.1.2 Terminologies in Male Reproductive Parts Terminologies Definition 4. Tetrad v A group of 4 haploid microspores (immature pollen grain) produced at the end of the second meiotic division 5. Pollen v Male gametophyte generation containing 2 cells, grain/male generative cell & tube cell when microspore gametophyte divide by mitosis Produced through mitosis of The pollen grain is an immature male haploid microspore gametophyte surrounded by two layer : Sperm producing structure, exine (outer layer) -secrete chemical which form within the pollen sac to determine compatibility of anther intine (inner layer) -secrete chemical Each contains two cell: tube cell to digest stigma tissue and generative cell Pollen grain are shed at maturity and transferred to sticky stigma by process called pollination  8.1 Sexual Reproduction in Flowering Plants 8.1.2 Terminologies in Male Reproductive Parts Terminologies Definition 6. Generative cell v One of the two cells in an angiosperm pollen grain which divide by mitosis to form 2 non-motile sperm cells v Nucleus of generative cell divide by mitosis to from two male gamete/ sperms cells. v Mitosis occurs after pollen grain land on the sticky stigma 7. Tube cell v One of the two cells in an angiosperm pollen grain produced when microspore divide by mitosis v Nucleus of tube cell produce pollen tube that extends down the style towards the ovary. v Pollen tube deliver the male gametes to the egg cell  8.1 Sexual Reproduction in Flowering Plants 8.1.3 Terminologies in Female Reproductive Parts Terminologies Definition 1. Megasporangium Ø A chamber within ovule in a heterosporous plant in which megaspores are produced Ø Female sporangial structure containing megasporocyte/ megaspore mother cell. Ø Correspond to the ovule in seed plants. Each ovule contain only one diploid megasporocytes cell at the center. 2. Megasporocyte / Ø A diploid cell in megasporangium megaspore mother that divide by meiosis to give rise cell to 4 haploid megaspores  8.1 Sexual Reproduction in Flowering Plants 8.1.3 Terminologies in Female Reproductive Parts Terminologies Definition 3. Megaspore Ø A larger haploid spore produce by megasporocyte. Ø Typically, only one megaspore survive and another three of megaspores degenerates. Ø The surviving megaspores undergo 3 mitotic division Ø Produce 1 large cell with 8 haploid nuclei (mitosis without cytokinesis)- known as embryo sac. 4. Embryo sac / Ø A large cell that develops in the ovule of female flowering plants containing 8 nuclei gametophyte formed by mitotic division of the surviving megaspore. Ø Egg producing structure, which begin to develop within the ovule of the ovary.  8.1 Sexual Reproduction in Flowering Plants 8.1.3 Terminologies in Female Reproductive Parts Terminologies Definition 5. Antipodal cell ü Three haploid cells in the mature embryo sac of flowering plants that are situated at the opposite end to micropyle 6. Polar nuclei ü Two haploid nuclei in the center of embryo sac of flowering plants which fuse with a male gamete to form a triploid endosperm 7. Egg cell ü The mature, unfertilized, non-motile female reproductive cell ü Will be fertilized by sperm cell to form diploid zygote (2n). 8. Synergid cell ü The two short-lived haploid cells in the embryo sac of flowering plants that are closely associated to the egg cell.  8.1 Sexual Reproduction in Flowering Plants 8.1.4 Gamete Formation in Flowering Plants (Female gamete)  8.1 Sexual Reproduction in Flowering Plants 8.1.4 Gamete Formation in Flowering Plants (Male gamete)  8.1 Sexual Reproduction in Flowering Plants 8.1.4 Gamete Formation in Flowering Plants (Male gamete) Pollen grain is enclosed by 2 wall, thick outer wall, exine & thin inner wall, intine Pollen grain is known as immature young male gametophyte; is a sperm producing structure A pollen grain becomes mature when it lands on compatible stigma Development of male gametophyte continue after pollination  8.1 Sexual Reproduction in Flowering Plants 8.1.4 Gamete Formation in Flowering Plants (Male gamete) When pollen lands on stigma, tube nucleus will produce pollen tube Generative nucleus divide once by mitosis to produce 2 sperm nuclei (male gametes) Germinated pollen is known as mature male gametophyte Pollen tube will deliver sperms to the egg.  8.1 Sexual Reproduction in Flowering Plants 8.1.4 Gamete Microsporocyte (2n) Formation in meiosis Flowering Plants (Male 4 haploid microspores (n) gamete) mitosis Pollen Grain (2-celled) Generative nucleus Tube nucleus 1X mitosis Gametophyte generation 2 sperm cells Produce pollen tube  8.1 Sexual Reproduction in Flowering Plants 8.1.5 Gamete Formation in Flowering Plants (Female gamete)  8.1 Sexual Reproduction in Flowering Plants 8.1.5 Gamete Formation in Flowering Plants (Female Gametophyte) integuments meiosis Surviving megasporocyte megaspore (2n) (n) micropyle funicle 3 megaspores near Megasporocyte undergoes meiosis to micropyle degenerate produce 4 haploid megaspores Female gametophyte develops within ovule Each ovule is attached to the ovary wall at the site called placenta by a short stalk, funicle Each ovule has 1 megaspore mother cell / megasporocyte (2n) Each megasporocyte divide by meiosis to produce 4 haploid megaspores 3 megaspores near micropyle degenerate  8.1 Sexual Reproduction in Flowering Plants 8.1.5 Gamete Formation in Flowering Plants (Female Gametophyte) meiosis Surviving megasporocyte megaspore (2n) (n) micropyle funicle 3 megaspores near Megasporocyte undergoes meiosis to micropyle degenerate produce 4 haploid megaspores Surviving megaspore undergoes mitosis 3 times to mitosis 3 antipodal nuclei produce 8 haploid nuclei (forming embryo sac) embryo sac mitosis mitosis Synergids 2 polar Ovum (n) nuclei  8.1 Sexual Reproduction in Flowering Plants 8.1.5 Gamete Formation in Flowering Plants (Female Gametophyte) 1 megasporocyte (2n) Meiosis 4 megaspores (n) 1 megaspore survive Mitosis (3x) 8 haploid nuclei (in embryo sac) 3 antipodal 1 ovum is flanked by 2 polar nuclei nuclei 2 synergid nuclei (centre)  8.2 Human Reproductive System LEARNING OBJECTIVES By the end of this topic, students should be able to: 1. Describe the overview male reproductive organ (testes) and the structure of spermatozoa 2. Explain the structure of spermatozoa 3. Explain the role of hormones in spermatogenesis: GnRH, LH, FSH and testosterone 4. Overview female reproductive organ (ovary) and the structure of secondary oocyte 5. Explain the structure of the secondary oocyte 6. Explain the role of hormones in female reproductive cycle: GnRH, LH, FSH, Estrogen and Progesterone.  8.2 Human Reproductive System 8.2.1 Introduction  8.2 Human Reproductive System 8.2.2 Male Reproductive System  8.2 Human Reproductive System 8.2.2.1 Male Reproductive Organ Male gonads; testes exist in pair Produce sperm & secrete sex hormones Held outside the abdominal cavity, in the scrotum (~2°C lower than body temperature) Consist of many long, highly coiled seminiferous tubules (where sperms are formed)  8.2 Human Reproductive System 8.2.2.1 Male Reproductive Organ Between the tubules are Leydig cells (secrete androgens ~ mainly testosterone) Sperms from seminiferous tubules pass into the coiled tubules of epididymis; where sperms become motile During ejaculation, sperm from epididymis pass into vas deferens Sequence: Seminiferous tubule ® epididymis ® vas deferens ® ejaculatory duct ® urethra ® release from body  8.2 Human Reproductive System 8.2.2.2 Structure of Spermatozoa i. Head contains haploid nucleus (paternal DNA) at the tip of the head, has acrosome (contains hydrolytic enzyme) that helps the sperm to penetrate the egg ii. Middle piece contain many mitochondrion supply ATP for movement of the tail iii. Tail (flagellum) originate from centriole for motility  8.2 Human Reproductive System 8.2.2.3 Spermatogenesis Process to produce male gametes (sperm) In which spermatogonia divide by meiosis to form spermatozoa (~7 weeks) Occur in seminiferous tubules in testes Starts at puberty (throughout adolescence and adulthood) Process of meiosis is uninterrupted / continuous  8.2 Human Reproductive System 8.2.2.3 Spermatogenesis Cells found in the outer edge of the seminiferous tubule is known as primordial germ cells Primordial germ cells remain dormant until puberty Shortly before puberty, primordial germ cells divide by mitosis to form spermatogonia (2n) Spermatogonia is supported by a large cell, Sertoli cell As spermatogonia divides, their daughter cells move inward; sperms are relased into the lumen  8.2 Human Reproductive System 8.2.2.3 Spermatogenesis  8.2 Human Reproductive System 8.2.2.3 Roles of Hormone in Spermatogenesis Gonadotropin Releasing Hormone (GnRH) At the onset of puberty, hypothalamus starts to secrete gonadotropin- releasing hormones (GnRH) GnRH stimulates anterior pituitary gland to secrete gonadotropins i.e. i. Follicle Stimulating Hormone (FSH) ii. Luteinizing Hormone (LH) Both hormones travel to testes through blood  8.2 Human Reproductive System 8.2.2.3 Roles of Hormone in Spermatogenesis Luteneizing Hormone (LH) Secreted by anterior pituitary gland. LH stimulates Leydig cells to secrete androgen; mainly testosterone* Follicle Stimulating Hormone (FSH) Secreted by anterior pituitary gland. FSH stimulate Sertoli cell to secrete Androgen Binding Protein (ABP)* **Which causes germ cells in testes become more receptive to testosterone Increase the concentration of testosterone in tubule to stimulate spermatogenesis  8.2 Human Reproductive System 8.2.2.3 Roles of Hormone in Spermatogenesis Testosterone Secreted by Leydig cells Male sex hormone to stimulate and maintain secondary sex characteristics. Helps in spermatogenesis. Regulates the production of GnRH, LH and FSH through negative feedback mechanism.  8.2 Human Reproductive System 8.2.2.3 Roles of Hormone in Spermatogenesis Sex hormone concentrations are regulated by negative feedback mechanism Testosterone acts on hypothalamus & anterior pituitary to regulate concentration of GnRH, FSH and LH FSH secretion is inhibited mainly by inhibin secreted by Sertoli cells FSH itself stimulates inhibin secretion  8.2 Human Reproductive System 8.2.2.3 Roles of Hormone in Spermatogenesis Hormone Secreted by Function GnRH Hypothalamus Stimulate anterior pituitary gland to secrete FSH and LH FSH Anterior Stimulate Sertoli cells to secrete Androgen pituitary Binding Protein LH Anterior Stimulate Leydig cells to secrete testosterone pituitary Testosterone Leydig cell Stimulate spermatogenesis process Inhibin Sertoli cell Inhibits anterior pituitary from secreting FSH FSH, LH and testosterone all directly or indirectly stimulate spermatogenesis  8.2 Human Reproductive System 8.2.3 Female Reproductive System  8.2 Human Reproductive System Oviduct / fallopian 8.2.3.1 Female Reproductive Organ tube extends from uterus towards a funnel-like opening at each ovary Female gonad (ovary) Uterus (pear-shaped, exists in pair fist sized) is located Flanking the uterus on centrally in pelvic each side region Held in place within It has thick wall of abdominal cavity by smooth muscle ligaments (myometrium) and its Size & shape almost like inner lining is called as large almonds endometrium  8.2 Human Reproductive System 8.2.3.1 Female Reproductive Organ Function: Produce female gametes (eggs / ovum) & secrete female sex hormones (estrogen & progesterone). Ovary release secondary oocyte every month during ovulation through the ruptured Graafian follicle. Ovary contains many follicles. Each follicle contains one primary oocyte surrounded by granulosa/follicular cells  8.2 Human Reproductive System 8.2.3.1 Female Reproductive Organ Size : 100-120µm diameter. Has large haploid nucleus and its cytoplasm contains the usual organelles. The haploid nuclei (arrested at metaphase II) sits inside a cell with a large volume of cytoplasm. Corona Radiata secretes estrogen produces zona pellucida Zona Pellucida Thick glycoprotein layer that prevent polyspermy  8.2 Human Reproductive System 8.2.3.2 Oogenesis Process to produce female gametes In which oogonium divide by meiosis to produce ovum Occurs in ovary Starts before birth and continue at puberty Process of meiosis is interrupted by resting period  8.2 Human Reproductive System 8.2.3.2 Oogenesis Before birth Arrested at Prophase I At puberty Arrested at Metaphase II (1 each cycle ~ till menopause) Entry of sperm  8.2 Human Reproductive System 8.2.3.3 Role of Hormones in Female Reproductive Cycle Occurs every month from puberty until menopause In each menstrual cycle, the endometrium (lining of uterus) thickens and develops a rich blood supply before being shed through the cervix and vagina if pregnancy does not occur. In average, a complete cycle occurs within 28 days (but can varies from 20 – 40 days) There are 2 types of cycle: Female Reproductive Cycle 1. Ovarian Cycle 2. Uterine / Menstrual Cycle  8.2 Human Reproductive System 8.2.3.3 Role of Hormones in Female Reproductive Cycle Ovarian cycle is regulated by 5 hormones: GnRH FSH LH Estradiol Progesterone  8.2 Human Reproductive System 8.2.3.3 Role of Hormones in Female Reproductive Cycle LH GnRH induce final Secreted by maturation of hypothalamus Graafian follicle Stimulates stimulates anterior pituitary ovulation gland to secrete (Graafian follicle FSH and LH rupture, releasing the secondary oocyte) FSH stimulates Stimulates the transformation of development of rupture Graafian follicles in the ovary follicle into the The growing follicles corpus luteum. secrete oestrogens  8.2 Human Reproductive System 8.2.3.3 Role of Hormones in Female Reproductive Cycle Oestrogen Progesterone Secreted by growing Secreted in follicle during follicular large amount phase by corpus As the follicle mature, they luteum secrete more oestrogen. maintain the Repair and thicken the endometrium endometrium with blood wall in vessel during proliferative preparation phase for Secreted in small amount implantation. by corpus lutuem during luteal phase Continued thickening of the endometrium for a possible pregnancy  8.2 Human Reproductive System 8.2.3.3 Role of Hormones in Female Reproductive Cycle Hormone Secreted by Function GnRH Hypothalamus Stimulate anterior pituitary gland to secrete FSH and LH FSH Anterior Stimulate development of follicles and pituitary secretion of estrogen LH Anterior Stimulate ovulation and development of pituitary corpus luteum Estrogen Growing follicle Induces maturation of follicle, (estradiol) Stimulate thickening of endometrium Progesterone Corpus luteum Stimulate further thickening of endometrial lining (enlargement of arteries to enlarge & supply blood to uterine lining)  8.3 Fertilization & Foetal Development LEARNING OBJECTIVES By the end of this topic, students should be able to: 1. Define embryogenesis. 2. State the developmental stages from zygote to the formation of morula, blastocyst and gastrula through cleavage. 3. Define organogenesis. 4. State the organ formed from each germ layers during organogenesis.  8.3 Fertilization & Foetal Development 8.3.1 Fertilization / conception Fertilization is a process that occurs when a Occurs in oviduct / Fallopian tube. haploid nuclei of the sperm fuses with a Producing a diploid zygote. haploid nuclei of the egg (ovum) in oviduct. There are 4 stages: Ovulation Fertilization 4 stages: 1 Capacitation 2 Acrosomal reaction 3 Fusion of sperm head membrane & oocyte 4 Cortical reaction  8.3 Fertilization & Foetal Development 8.3.1 Foetal Development Oviduct Secondary oocyte Fimbriae Ovulation process After fertilization, zygote moves from oviduct towards the uterus Ovary With the help of: i.Cilia movement in the lining of oviduct ii.Contraction of oviduct muscles / peristalsis As zygote moves, it undergoes a series of cleavage  8.3 Fertilization & Foetal Development 8.3.1 Foetal Development EMBRYOGENESIS Definition: Process by which the embryo forms and develop. Starts with formation of zygote after fertilization. Zygote undergoes cleavage. Cleavage is a series of rapid mitotic cell division without growth Forming multicellular embryo. Development begins in the oviduct and then embryo moved towards the uterus for implantation.  8.3 Fertilization & Foetal Development 8.3.1 Foetal Development DEVELOPMENTAL STAGES Zygote undergoes cleavage progressing through 2 cell, 4 cell and 8 celled stages. As cleavage continue, forming solid ball stage of cells known as morula Each small cells in the morula is called blastomere. Morula develop into hollow ball stage of cells with inner cavity known as blastocyst.  8.3 Fertilization & Foetal Development 8.3.1 Foetal Development DEVELOPMENTAL STAGES Blastocyst consists of blastocoel, trophoblast and inner cell mass. Blastocysts attaches to uterine lining for implantation. Trophoblast secrete enzyme to penetrate the endometrium. Trophoblast also secrete hCG to prevent corpus luteum from disintegrate. Inner cell mass separate into epiblast and hypoblast.  8.3 Fertilization & Foetal Development 8.3.1 Foetal Development The fluid-filled cavity is called blastocoel It is surrounded by a single layer of cell, trophoblast (later forms chorion & contributes to placenta) The cluster of cells inside is called inner cell mass, which gives rise to embryo  8.3 Fertilization & Foetal Development 8.3.1 Foetal Development DEVELOPMENTAL STAGES Gastrulation occurs to form gastrula. Producing three germ layers. Which is ectoderm, mesoderm and endoderm. Four extraembryonic membrane are form: chorion, amnion, yolk sac and allantois  8.3 Fertilization & Foetal Development 8.3.1 Foetal Development DEVELOPMENTAL STAGES  8.3 Fertilization & Foetal Development 8.3.2 Organogenesis Formation of organs. The process by which the three germ layers give rise to specific organs of the body. Ectoderm- form nervous system, epidermis of skin and sensory organ. Mesoderm- muscles, bones, cartilage, heart, circulatory systems, kidneys and reproductive system Endoderm- innermost lining of the intestine and digestive organs (pancreas, liver)  8.3 Fertilization & Foetal Development 8.3.2 Organogenesis Definition - the formation of organ from the differentiation & development of 3 germ layers The first event in organogenesis is neurulation, early steps in the formation of brain & spinal cord Notochord, brain & spinal cord are among the 1st organ to develop Also heart & blood cells Organogenesis occurs during the 3rd – 8th weeks of development (embryonic period ® embryo) Embryogenesis is the period of organogenesis Most sensitive period  8.3 Fertilization & Foetal Development 8.3.2 Organogenesis By the end of embryonic period, all major structures of the adult are present in early forms Embryo is then called as fetus After embryogenesis / organogenesis is completed, fetal development ® fetal period Fetal period extends from 9th week of gestation until birth Mesoderm around notochord develop into segmented blocks called somites Some develop into vertebrae, others form muscle & ribs Some body organs (kidney, reproductive structures & circulatory organs) develop from mesoderm along the somite At the end of organogenesis, all organ systems are formed Embryo is now called as fetus (W9 – before birth)  8.3 Fertilization & Foetal Development 8.3.2 Organogenesis Developmental fates of Primary Germ Layers Ectoderm - Epidermis (outer layer of skin) - Nervous system - Sensory organ Mesoderm - Skeletal system (notochord), & bone - Muscles & connective tissues (cartilage, blood) - Circulatory system (heart, vessels, lymph vessels) - Excretory system (kidney) - Reproductive system (gonad) & spleen Endoderm - Lining of digestive system - Lining of respiratory tract, lungs - Liver & pancreas, urinary bladder  8.3 Fertilization & Foetal Development 8.3.3 Human Development Overview Ovulation Fertilization Cleavage Implantation Gastrulation Blastocyst-day 7 Foetal development Organogenesis Fetal period Embryogenesis W9-birth W3-W8 Pregnancy/Gestation Parturition Lactation  8.4 Roles of Hormones During Pregnancy & Parturition LEARNING OBJECTIVES By the end of this topic, students should be able to: 1. Explain the role of hormones during pregnancy. - Progesterone - Oestrogen - Human chorionic gonadotropin 2. Explain the role of hormones during parturition / birth process. - Progesterone - Oestrogen - Oxytoxin - Prostaglandin  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.1 Role of Hormones during: During:- Pregnancy / Gestation Parturition / Birth  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.1 Role of Hormones during Pregnancy Appropriate levels of hormones are important to maintain pregnancy Hormones involved are:- hCG (human chorionic gonadotropin) Progesterone Estrogen  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.1.1 hCG (human chorionic gonadotropin) hCG is secreted by trophoblast Signals corpus luteum that pregnancy has begun In response, corpus luteum increase in size, secrete large amount of estrogen & progesterone Without hCG, corpus luteum will degenerate (hCG acts like LH)  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.1.1 hCG (human chorionic gonadotropin) If corpus luteum is removed before 11th week, embryo spontaneoulsly aborts2 After 11th week, placenta can secrete enough progesterone & estrogen to maintain pregnancy As level of hCG decrease, corpus luteum degenerates  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.1.1 hCG (human chorionic gonadotropin) All pregnancy tests used today are antibody tests that detect hCG in a woman’s blood or urine Usually detectable 1 week after fertilization (implantation)  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.1 Role of Hormones during Pregnancy Hormones Function Time Secreted by hCG § Maintain corpus luteum 1-11th week Trophoblast Estrogen § Stimulate development of uterine wall Until 11th Corpus (endometrium) & myometrium muscle2 week luteum § Stimulate the enlarge/growth of uterus & breasts5 After 11th Placenta § Increase the number of oxytocin receptors week in uterine wall (late pregnancy)2 § Prevent ovulation & menstrual cycle (inhibits secretion of FSH & LH)2  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.1 Role of Hormones during Pregnancy Hormones Function Time Secreted by Progeste- § Stimulate the growth of endometrium lining5 Same as estrogen rone § Inhibits uterine contractions2 (prevent miscarriage) § Stimulate mucus production in cervix to form a protective plug (against infection)1 § Stimulates growth of maternal portion of placenta1 § Stimulate the enlarge/growth of uterus & breasts1 § Prevent ovulation & menstrual cycle (inhibits secretion of FSH & LH)2  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.1 Role of Hormones during Pregnancy Initially (the first 2-4 weeks) implanted embryo obtain nutrients by digesting the endometrial cells1 By the end of the 3rd month, well-developed placenta starts to provide nutrients & O2  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.2 Parturition Process Parturition / Birth – Stage 1 (Dilation of cervix) As labor begins, contractions become more vigorous & rapid Contractions of uterus move the fetus toward the cervix, causing the cervix to dilate (open)  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.2 Parturition Process Parturition / Birth – Stage 1 (Dilation of cervix) From labor onset until cervix is fully dilated by the baby’s head (usually 10 cm) Cervix soften & thinner Eventually amnion usually ruptures Releases amniotic fluid through the vagina Longest stage  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.2 Parturition Process Parturition / Birth – Stage 1 (Dilation of cervix)  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.2 Parturition Process Parturition / Birth – Stage 2 (Expulsion of baby) Start from full dilation of cervix to delivery of infant Fetus passes through the cervix and vagina ® born / delivered Lasts ~ 20 minutes - 1 hr The cord is tied and cut, separating the child from the mother The cord ~ detached (scar remains)  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.2 Parturition Process The cord is tied and cut, separating the child from the mother The cord ~ detached (scar remains)  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.2 Parturition Process Parturition / Birth – Stage 3 (Expulsion of placenta) Placenta loosened from the lining of the uterus & expelled by another series of contractions Lasts ~ 5 or 30 minutes after the birth of the baby  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.2 Parturition Process  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.3 Role of Hormones during Parturition A process when fetus is expelled from the uterus to the outside through cervix & vagina Regulated by interaction of 4 hormones:- Estrogen Progesterone Oxytocin Prostaglandin  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.3 Role of Hormones during Parturition During pregnancy, progesterone & estrogen levels are high High level of progesterone prevents contraction of uterus In late pregnancy, fetus secretes ACTH (cortisol) It stimulates placenta to secrete more estrogen Causing level of estrogen to increase at late pregnancy. High level of estrogen causes: Ø Formation of oxytocin receptors on the myometrium / uterus to increase its sensitivity Ø Weak, irregular contraction of myometrium  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.3 Role of Hormones during Parturition Contraction stimulates stretch receptors in the cervix Which sends signals to mother’s hypothalamus Hypothalamus stimulates posterior pituitary gland to secrete oxytocin Further contraction occurs Contraction also stimulates placenta to secrete prostaglandin  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.3 Role of Hormones during Parturition Both hormones stimulates greater myometrium contraction The baby is pushed deeper into birth canal Stimulates stretch receptors in the cervix Increasing physical & emotional stress of the mother stimulates the secretion of both hormones by positive feedback Further contraction occurs until the baby is born  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.3 Role of Hormones during Parturition Hormones Function Time Secreted by Estrogen § Increase the number of Late Placenta oxytocin receptors in uterine pregnancy wall (late pregnancy) § Stimulate the relaxation of pelvic ligaments to facilitate the passage of fetus through birth canal Progesterone § Its level decrease prior to Late Placenta parturition which removes pregnancy inhibition of uterine contraction5  8.4 Roles of Hormones During Pregnancy & Parturition 8.4.3 Role of Hormones during Parturition Hormones Function Time Secreted by Oxytocin § Stimulate strong rhythmic Late Fetal & contraction of uterine pregnancy mother’s muscle posterior § Prevent ovulation & pituitary menstrual cycle (inhibits secretion of FSH & LH) Prostaglandin § Stimulate further Labor Placenta contraction of uterine muscle End of CHP 8 Any questions?