3)PLACENTA and FOETAL MEMBRANES 2024 2.pdf

PLACENTA and FETAL MEMBRANES Prof.Dr.Cengiz Bayçu -2024 Objectives Describes the structure and function of the placenta, umbilical cord , amnion ,yolk sac,allantois: The extaembryonic of fetal membranes They originate from the embryo, but are not considered part of it. They typically perform roles i...

PLACENTA and FETAL MEMBRANES Prof.Dr.Cengiz Bayçu -2024 Objectives Describes the structure and function of the placenta, umbilical cord , amnion ,yolk sac,allantois: The extaembryonic of fetal membranes They originate from the embryo, but are not considered part of it. They typically perform roles in nutrition, gas exchange, and waste removal Fetal Membranes and Placenta: Their origin is ZYGOT Membranes : 1. Yolk (Vitelline) sac 2. Amnion 3. Allantois 4. Chorion The fetal membranes are four of six accessory organs developed by the conceptus that are not part of the embryo itself, the other two are the placenta, and the umbilical cord. 1. Umbilical cord 2. Placenta Development of Yolk sac and Amnion (8 through 14 days of 3 week embryogenesis) The inner cell mass becomes a bilaminar disc as it divides into the: A- HYPOBLAST, which forms the YOLK SAC, B- EPIBLAST, which forms the AMNION. The yolk sac and amnion develop simultaneously, which begins during eight (8) day through day-14 of embryogenesis. inner cells Yolk Sac (vitellin sac) Yolk sac forms from proliferating HYPOBLAST cells after implantation. It attaches ventrally to the developing embryo via the yolk stalk. The yolk stalk connects the yolk sac to the midgut, which is an early derivative of the gastrointestinal system. Both the midgut and yolk sac are endodermal in origin. The yolk sac has several critical biological functions during early gestation such as ; 1. It is the structure that provides NUTRITION in the second and third weeks. 2. It is site of «PRIMITIVE HEMATOPOIESIS AND FIRST BLOOD» production at 3rd.week 3. It is site of «GERM CELL« production. Primordial germ cells that appear in the endodermal epithelium of the sac (3rd week) they migrate towards the gonads 5-6 week In 4 th. week, it appears as a MIDDLE INTESTINE, and from here the epithelium of the trachea,lungs and digestive tract develops in the future. The sac is quite large in first month but regresses every week and at 20 week , it becomes very small and then disappears Amniotic Fluid It begins to form from the 12th day of fertilization. The amonut of the fluid is ; 30 ml at the 10th gestational week, 50 ml at the 12th gestational week, and 800 to 1000 ml at full term (40 weeks) Contents ; 99% water ,exfoliated epithelium, carbonhydrate, Protein,Fat, Enzyme,Hormone, 400cc of liquid is swallowed by the fetus per day. A. B. The liquid passes into the respiratory and digestive system and into the fetal bloodstream.Waste products are transferred to the maternal circulation through the placenta. Urine and other substances (water) excreted by the fetal kidneys pass into the amniotic fluid and are swallowed again by the fetus. C. Meconium (fetal feces) formation in the fetus is observed in the last stages of pregnancy Circulation of Amniotic fluid 1. The water content of the amniotic fluid changes every 3 hours. 2. A large amount of water enters the mother's tissue through the chorioamniotic membrane and enters into the uterine capillaries. 3. The exchange of fluid with fetal blood occurs through the umbilical cord, which is connected to the chorionic plate of the amnion on the fetal side of the placenta Fetal face Maternal face Functions of Amnion 1. Plays role in Symmetrical growth of the embryo 2. Protects the embryo/fetus against infections 3. Protects fetus from mechanical impacts 4. Ensures normal lung development of the fetus 5. Maintains optimal retention of body temperature 6. Ensures the free movement of the fetus and the normal development of the muscular system 7. Maintaines homeostasis and electrolyte balance 8. It is a Immunological barrier AMNIOTIC FLUID PROBLEMS Oligohydramnios: (500 ml) Fluid deficiency due to renal agenesis or lack of placental circulation. Low amniotic fluid volumes can be the result of numerous maternal, fetal, or placental complications and can lead to poor fetal outcomes. (Fetal and Placenta deffiency, maternal hypertension) Polyhydramnios (2000 ml.) Increased amount of fluid due to inability to swallow fluid 1. CNS disorder or Esophageal atresia of the foetus 2. Blockages in the baby's intestine 3. Pathologies that prevent swallowing in the baby (fetal goiter, masses on the neck 4. Having diabetes in the mother Various drug and substance uses (cocaine, heroin use or lithium treatment) Meconium Aspiration (MAS) and Birth Injury Under normal circumstances, a fetus’s meconium (excretory matter,feces) is stored in the intestines until after delivery. However, distress of the baby like infection or lack of oxygen can cause passage of meconium into the amniotic fluid before or during birth. Which can cause fetus to inhale the meconium and The mixture can then travel to their lungs and the baby may breathe (aspirate) it into lungs just before, during, or after birth. This amniotic fluid. is known as meconium aspiration syndrome (MAS). The most common signs of fetal distress are: 1. 2. 3. 4. 5. Difficulty in breathing due to precense of meconium in the lungs. Changes in the fetal heart rate (lower or higher rate than normal). The fetus moves less for an extended period of time. Low amniotic fluid. Oxygen deficiency Main Causes : 1. 2. 3. Compression of the head and/or umbilical cord due to hypoxia or hypoxia, Increased vagal stimulation due to hypoxia Relaxation of the anal sphincter due to increased intestinal peristalsis cause meconium to flow into the amniotic fluid. Treating methods of MAS 1. 2. 3. 4. 5. 6. 7. 8. Endotracheal intubation and mechanical ventilation as needed. Supplemental oxygen as needed to keep PaO2 high to relax pulmonary vasculature. Surfactant or antibiotics to open lungs and clear any infection. IV antibiotics. Inhaled nitric oxide in severe cases of PPH. The meconium aspiration of the fetus cannot be prevented. However , To prevent severe aspiration is may possible by ; To monitor the amniotic fluid for meconium and watch for fetal distress Detecting aspiration early and quickly Allantois About at 3rd week it begins to appear in the form of a caudal protrusion from the YOLK SAC AND Moves Inside The Connectıng Stalk Of The Embryo Function of Allantois In the embryonic period ; 1- Plays role in RESPIRATION by exchanging gases with the chorionic membrane 2- Participates in the development BLADDER and it is site of urine storage in this period 3- Participates in the DEVELOPMENT OF BLOOD and UMBILICAL CORD VESSELS. After the second month, it regresses and than the PLACENTA AND AMNION BEGIN TO FUNCTION UMBILICAL CORD A. The umbilical cord is the vital connection between the fetus and the placenta. Connects the embryo/fetus to the maternal placenta. In the womb, the umbilical cord provides the OXYGEN AND NUTRIENTS needed for the embryo to grow. B. It is formed by the (5) fifth week of development and it functions throughout pregnancy to protect the vessels that travel between the fetus and the placenta. At 8-10 week , the umbilical formed. cord has fully By the 10th week the gastrointestinal tract has developed and protrudes through the umbilical ring to form a physiologically normal herniation into the umbilical cord Blood Vessels of the umbilical cord: A- With the Umbilical vein carrying oxygenated blood with nutrients from the placenta to the fetus (Chorioamniotic membrane) B- Umbilical arteries transporting deoxygenated blood with waste products from the fetus to the placenta. Wharton jelly consist of 2 arteries 1 vein -mucous connective tissue Arteries Vein Umbilical cord entanglement and knot Hypoxia- Brain damage and mental retardation in the fetus in case of oxygen deficiency for more than 5 minutes. Anoxia (oxygen deficiency) and death are observed in the knotting The Placenta 1. The placenta begins to develope from the blastocyst shortly after implantation. 2. The placenta and umbilical cord are transport organs 3. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations 4. It is an important endocrine organ producing hormones that regulate both maternal and fetal physiology during pregnancy. Functions Protection Nutrition Respiration Excretion Production of hormone Development of Placenta Developes From DECIDUA BASALIS and CHORION FRONDOSUM In 3rd week the anatomical and physiological connection is established between the embryo and the mother 1- TROPHOBLAST are cells forming the outer layer of a blastocyst, which provides nutrients to the embryo, and develops into a large part of the placenta. They are formed during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg. 2- In second week the differentiates during implantation into the following: 1- The CYTOTROPHOBLAST, a layer of mitotically active cells around the amnion and yolk sac. 2- The SYNCYTIOTROPHOBLAST, a more superficial, nonmitotic mass of multinucleated cytoplasm which invades the surrounding stroma. As a result, from these layers CHORION is formed (FETAL PLACENTA) The formation of vascularization on week 4 and accordingly, the start of nutrition and gas exchange between embryo and mother. Parts of Placenta A- Fetal Placenta : CHORION: The chorionic membrane is a fibrous tissue layer containing the fetal blood vessels. The chorionic villi are involved in fetal-maternal exchange which is two parts ; 1. Chorion Laeve (smooth) : the smooth part of the chorion that lacks villi and is not part of the placenta. 2. Chorion Frondosum The part of the chorion that has persistent villi and that with the decidua basalis forms the placenta B- Maternal Plasenta : Desidua basalis (in Uterus endometrium) Human Placenta 1. 2. Placenta also called ; Placenta cotylodonata Placenta discoidalis 3. Placenta hemochorialis Placental barrier: Chorion Villi consist of : a. Cytotrophoblast-syncytiotrophoblast layers b. Connective tissue of villi c. Vascular endothelium of villi 1 Placenta Layers 2 1. Decidua parietalis: the part that covers the inside of the uterus 2. Decidua basalis : the layer that forms the maternal placenta 3. Decidua capsullaris : the part of the placenta that surrounds the fetus 3 DECIDUA : Endometrium gravidarum The decidua forms the maternal part of the placenta and remains for the duration of the pregnancy Composition of Decidua A- Cells Macrophages, Lymphocytes, Granulocytes, Decidual cells B-Exstracellular matrix Laminin ,Fibronectin Kollagen type-IV Heparan sulfate, proteoglycan 1- Decidual cells are stromal cells in the uterine endometrium that develop, grow and accumulate glycogen-fat due to an increase in Progesterone during pregnancy 2- Decidual cells also protect the mother from the attack of syncytiotrophblasts Placenta after birth Maternal Fetal Vascularization of the Chorion Villi 10 week Mature a.CytotrophoblastSyncytiotrophoblast layers b.Connective tissue of villi c.Vascular endothelium of villi Histology of Mature Placenta--1 Functions of Hofbauer cell: 1-Macrophage-like cells and are involved in defense 2- Ensures the formation of the villi stroma 3-Controls the flow of placental fluid 4-Control of vasculogenesis 5-Possibly indirectly stimulate collagen production Fetal-placental circulation 1. Oxygen-poor blood leaves the fetus and enters the placenta through the Umbilical Arteries 2. 3. 4. These vessels in the placenta are divided into many branches and form a dense ARTERIO-VENOUS CAPILLARY SYSTEM IN THE VILLI This system forms a very large surface that performs metabolism and gas exchange between the mother and the fetus The oxygenated blood in the fetal capillaries passes through the veins, these veins merge to form the Umbilical Vein, which carries oxygen-rich blood to the fetus. Placenta as Allograft and Tissue Rejection 1. Allograft : An allograft is tissue that is transplanted from one person to another 0r a tissue graft taken from another individual (donor) who is the same species as the recipient 2. The placenta is an allograft according to the mother. The concept is the part that forms the Fetal Part of the Placenta that carries the genetic material of the mother and father. In this case, how is the placenta protected from the immune system of the mother or why the mother does not reject the placenta ? 3. 4. The fetal-maternal immune system determines the fate of pregnancy. THE TROPHOBLAST cells not only give an active response against external stimuli but are also involved in secreting most of the cytokines. These cells have an essential function IN FETAL ACCEPTANCE OR FETAL REJECTION. Tolerance of the fetus by the maternal immune system: role of inflammatory mediators at the fetalmaternal interface and Factors that play role in tissue rejection DECIDUA provide an immuno protective environment for the development of the embryo. A. Cytotrophoblast cells are exposed to T LYMPHOCYTES AND NATURAL KILLER (NK) cells which are two types of maternal immune cells in decidua, and therefore cytotrophoblast cells are potentially target of an immune attack. B. Production of PROSTOGLANDINS AND OTHER IMMUNESUPPRESANT substances secreted by DECIDUAL cells to inhibit the activation of T /NK cells in the endometrial stroma Secondly, Secretion of Interleukin-2 by leukocytes entering the endometrial stroma to prevent rejection of the embryo by the maternal tissue C. D. Despite the fact that chorionic villi cells are exposed to immune cells of the maternal tissue, the absence of major histocompatibility (MHC) antigens in the SYNCYOTROPHOBLAST DO NOT INITIATE TISSUE REJECTION Metabolism of the Placenta Substances transfer between the mother and the Fetus: 1. Water-Glucose 2. Cholesterol-Triglyceride 3. Amino Acids-Hormones-Electrolyte 4. Antibodies from mother (IgG) There is a 2-way transport of substances between the placenta and the mother and these are basically 4 types: 1. Passive transport by simple diffusion: oxygen -CO2 -water electrolytes 2. Facilitated diffusion : glucose 3. Active transport – amino acid ,vitamin 4. Pinocytosis-fat,complex proteins,Ig Placental Hormones and functions Syncytiotrophoblasts in the fetal placenta synthesize protein and steroid hormones a. The placenta provides the production of the hormones PROGESTERONE and ESTROGEN, which are involved in maintaining pregnancy. b. hCG (HUMAN CHORIONIC GONADOTROPIN) is synthesized in the second week that suppresses the menstrual cycle , ensures the continuation of the corpus luteum (corpus luteum of pregnancy). At the eighth week hormone reaches the highest level in c. d. e. the mother's blood and urine, then gradually decreases Chorionic somatotropin or placental lactogen Chorionic thyrotropin Chorionic corticotropin Placental Barrier and harmful substances Pregnancy and Rubella infection (Rubella syndrome) Rubella is a common viral infection. It can cause serious problems like Abartus and anomalia in the fetus during pregnancy. Infection is caused by direct contact with the secretions of the nose and mouth Deafness, Cataracts, Heart defects, hearing loss, Diabetes mellitis, brain disorders, Mental retardation,fetal growth restriction bone alterations, Liver and spleen damage. peripheral pulmonary stenosis narrowing in one or more of the branches of the pulmonary arteries 7 Toxoplasma Infection Toxoplasmosis is an infection with a parasite called Toxoplasma gondii ( most animals and birds ). Toxoplasmosis can cause miscarriages, dead or disabled births during pregnancy. People often get the infection from ; A. Eating undercooked meat or from contact with cat feces B. Organ transplantation or blood transfusion from an infected person The parasite can pass from placenta and reach to a baby during pregnancy. 1- Symptoms : 1. 2. 3. 4. Too much fluid in or around the brain, also called hydrocephalus. Severe eye infection. Irregularities in brain tissues. An enlarged liver or spleen. 2- Symptoms of severe disease vary ; 1. Problems with mental or motor skills. 2. Problems with thinking and learning 3. Blindness or other vision problems. 4. Hearing problems. 5. Seizures. 6. Heart disorders. Placenta Complications. Placenta previa: Abnormal insertion of the placenta in the uterine wall The placenta is next to the cervix but does not cover the opening. the placenta covers part of the cervical opening Risc factors that predispose women to this complications are : Uterine malformations Advanced maternal age Twin pregnancy or multiple pregnancy Having had several previous pregnancies the placenta covers the entire cervical opening Short time between two births Having had a previous cesarean delivery Uterine scars from previous abortions or surgeries Tobacco and cocaine abuse Placenta Accreta The placenta is adhered to the wall of the uterus. The placenta does not only adhere to the wall, but moves into the wall and is called 1. placenta accreta, 2. placenta increta 3. placenta percreta, respectively, according to the degree of this progression. Twin pregnancy Dizygotic Monozygotic Twins 9 week twins 1 2 3 Stages of Labor and Birth Clinically, there are 3 stages of childbirth Dilation of cervix (stage 1) Birth (stage 2) Delivery of Placenta (stage 3) Stages 1-2 9 Prenatal Diagnostic Techniques : Diagnostic Amniocentesis 1. 2. Applied in 15th and 18th weeks of pregnancy The needle no.22 is immersed along the abdominal and uterine walls of the mother to reach the chorion and amnion and 15-20 ml of amniotic fluid is taken up and biochemical and genetic analyses. 3. Genetic disorders such as Down Syndrome, Neural Tube Defects, Congenital Metabolic disorders are diagnosed with this method CHORIONIC VILLUS SAMPLE (CVS) g Ultrasonografi (renkli dopler) IVF (in vitro fertilization) ICSI (intracytoplasmic sperm injection) Thank you for attention