Ciclo de Conferencias Magistrales. Tema: Desarrollo de Placenta

Development and Physiology of the Placenta

In this section, the speaker discusses the development and physiology of the placenta in humans, along with related pathologies.

Development of the Placenta

• The human placenta is an organ that develops in women during gestation, facilitating oxygen and nutrient exchange between mother and embryo. It originates from the trophoblast.

• After fertilization, the embryo remains surrounded by the zona pellucida, which acts as an immunological barrier lacking histocompatibility antigens to prevent immune attacks on the embryo.

• The zona pellucida dissolves at a specific point to allow for implantation. This process is known as blastocyst hatching.

• Loss of the zona pellucida around day 5 post-fertilization enables embryo penetration into the endometrium for implantation. Failure to lose it at the correct location can lead to ectopic pregnancy.

Pathologies Related to Implantation

• Ectopic pregnancies occur when implantation happens outside the uterus, with tubal pregnancies being common. Incorrect implantation locations can lead to complications like placenta previa obstructing birth canals.

• Strong adhesion between embryo and endometrial stroma is crucial before contact; cytokines like leukemia inhibitory factor aid in this process by facilitating attachment through integrins.

Continuation: Development of Trophoblast

This section delves into trophoblast differentiation, its interaction with endometrium, and subsequent growth within the uterus.

Trophoblast Differentiation

• Trophoblast cells differentiate upon adhering to endometrium using integrins for attachment via ligands.

• By days 10-12 post-fertilization, syncytiotrophoblast covers the embryo entirely and expands across endometrium through cellular proliferation.

Formation of Residual Reaction

• Syncytiotrophoblast induces a residual reaction forming a cellular matrix around itself and endometrium that shields against maternal immune recognition.

Arterial Erosion and Acretism Placentae

This part explores arterial erosion by syncytiotrophoblast leading to lacunar spaces formation in trophoblastic villi.

Arterial Erosion Process

• As syncytiotrophoblast grows, it erodes spiral arteries creating lacunar spaces filled with blood causing mistaken bleeding for abnormal menstruation.

Acretism Placentae Pathology

• Acretism placentae results from abnormal placental adherence due to deficient basal decidua leading to three types: accreta, increta, percreta based on depth of villi attachment.

Detailed Embryonic Development Process

In this section, the detailed process of embryonic development is discussed, focusing on the invasion and formation of various structures within the embryo.

Metro La Inquieta and Vellosidades

• The process begins with "metro la inquieta," where vellosidades invade deeply into the metro.

• Initially, there is a period of pre-bello citar yo leading to the development of velocidades coriónicas.

• Vellosidades coriónicas develop into primary vellosidades characterized by cell accumulations.

• Secondary vellosidades form as mesenchyme from the chorionic plate attaches to primary vellosidades.

Differentiation and Blood Vessel Infiltration

• By the third week, corionic velocities differentiate as they are infiltrated by fetal blood vessels.

• Asymmetric growth leads to tertiary velocities at different poles of the embryo.

Placental Formation and Cell Proliferation

• Cordón umbilical and placenta formation are observed alongside maternal blood vessel infiltration.

• Cells express transcription factor Gen 1 for proliferation within maternal blood spaces.

Maternal-Fetal Circulation and Placental Types

• Maternal blood enters intervellositary space through maternal arteries due to erosion for pressure regulation.

Embryonic and Fetal Hemoglobin Differences

The discussion focuses on the distinction between embryonic and fetal hemoglobin in relation to oxygen transport in the fetus.

Embryonic Hemoglobin Function

• Embryonic hemoglobin is present from the beginning until week 12.

• Due to limited maternal blood supply before week 12, there is low oxygen delivery to the fetus, leading to a state of hypoxia.

• Embryonic hemoglobin has a high affinity for oxygen to maximize oxygen uptake in low-oxygen conditions.

Transition to Fetal Hemoglobin

• After week 12, increased maternal blood supply results in higher oxygen levels.

• Fetal hemoglobin replaces embryonic hemoglobin with less affinity for oxygen due to improved oxygen availability.

Structure and Functions of Chorion

Exploring the composition and asymmetrical features of the chorion in pregnancy.

Components of Chorion

• Comprised of extraembryonic mesoderm and trophoblast.

• Trophoblast further divides into cytotrophoblast and syncytiotrophoblast.

Asymmetrical Vellosities Formation

• Oxygen-poor environment at the embryonic pole promotes vellosities growth.

• Spiral arteries sealed by cytotrophoblast cells restrict blood flow, maintaining low oxygen levels for cell mitosis.

Decidua Types and Placental Development

Discussing decidua types, their roles, and changes during gestation.

Decidua Classification

• Decidua basalis: Forms part of the placenta directly.

• Decidua capsularis: In contact with smooth chorion.

• Decidua parietalis: Not closely associated with chorionic structures.

Gestational Changes

• Capsularis degenerates post mid-gestation merging with parietalis.

Mature Placental Structure

Detailing characteristics of a mature placenta towards the end of gestation.

Placental Features

• Thickness: 3 cm; Diameter: ~20 cm; Weight: ~500g at term.

Feto-Maternal Circulation in Placenta

Explaining circulation between fetal and maternal components within the placenta.

Fetal Component

• Comprises frondosum cordis derived from extraembryonic mesoderm & cytotrophoblast layers.

Maternal Component

Placental Physiology and Function

This section delves into the intricate processes of nutrient exchange, waste removal, and barrier functions within the placenta during pregnancy.

Nutrient Exchange in the Placenta

• The maternal blood does not directly mix with fetal blood; only specific substances like oxygen pass through.

• : Oxygen, nutrients, and vitamins are transferred to nourish the embryo or fetus via the umbilical vein.

• Waste products like CO2 are carried away from the fetus through two umbilical arteries towards the placenta for disposal.

• : CO2 is removed from fetal blood at the placental barrier without mixing with maternal blood.

Placental Barrier Evolution Throughout Pregnancy

• The placental barrier undergoes changes between the first and third trimesters to facilitate nutrient transfer.

• : In early pregnancy, multiple layers separate maternal and fetal blood for molecule exchange.

• : By late pregnancy, some barriers disappear, simplifying nutrient transport for efficiency.

Structural Adaptations in Placental Development

• Microvilli on chorionic villi increase surface area for absorption based on fetal needs.

• : Enzymes aid in molecular conversion within microvilli to support nutrient uptake.

• Microvilli adapt in size based on fetal requirements; more oxygen demand leads to increased microvilli size.

• : Fetal macrophages decrease as pregnancy progresses, impacting immune responses.

Maternal-Fetal Substance Transfer

• From mother to fetus: Oxygen, water, electrolytes, glucose are crucially supplied; antibodies provide temporary immunity post-birth.

• : Glucose is a primary nutrient source for embryos; antibodies offer passive immunity prenatally.

• Harmful substances like certain drugs can cross from mother to fetus through placental transfer with potential risks.

• : Torch profile tests identify pathogens that may cause congenital diseases if transmitted from mother to baby.

Torch Profile Testing and Implications

• Torch profile screens for infections that could affect newborns if passed from mother during pregnancy.

Detailed Overview of Endocrinology in Pregnancy

In this section, the discussion revolves around the transmission of hormones and antigens between the mother and fetus, focusing on pathologies like erythrocytes is fetal. Additionally, the role of the endocrine placenta in hormone synthesis and secretion is explored.

Transmission of Hormones and Antigens

• Erythrocytes is fetal is a condition where the mother produces antibodies against the Rh proteins of the fetus's red blood cells.

Role of Endocrine Placenta

• The endocrine placenta, specifically the syncytiotrophoblast, is responsible for synthesizing and secreting hormones crucial during pregnancy.

Functions of Gonadotropin Chorionic Hormone

• Gonadotropin chorionic hormone plays a key role in maintaining the corpus luteum during early pregnancy to prevent its degeneration.

Functions of Human Chorionic Gonadotropin

This segment delves into how human chorionic gonadotropin supports hormone production during pregnancy by stimulating progesterone and estrogen synthesis.

Maintenance of Corpus Luteum

• Human chorionic gonadotropin ensures that the corpus luteum continues producing essential hormones like progesterone and estrogen during early pregnancy.

Collaboration with Placenta

• The placenta collaborates with human chorionic gonadotropin to collectively produce necessary hormones since the placenta alone cannot meet all hormonal requirements during gestation.

Synthesis of Progesterone and Estrogens

This part focuses on how progesterone and estrogens are synthesized within the placenta using precursors from acetate or cholesterol, highlighting their vital functions during pregnancy.

Independent Synthesis

• Progesterone is synthesized autonomously in the placenta from acetate precursors, while estrogens are produced independently by combining adrenal fetal glands with fetal liver enzymes.

Role of Human Chorionic Gonadotropin

Here, we explore how human chorionic gonadotropin influences progesterone and estrogen secretion while shedding light on other essential hormones like somatomammotropin chorionic hormone.

Regulatory Function

• Human chorionic gonadotropin potentially regulates progesterone and estrogen secretion; however, further research is needed to clarify its exact mechanisms.

Impact of Somatomammotropin Chorionic Hormone

This section elucidates how somatomammotropin chorionic hormone affects various physiological aspects such as breast growth, lactation promotion, and metabolic changes related to carbohydrate resistance.

Metabolic Effects

Homólogo de la Hormona Liberadora de Gonadotropina

In this segment, the speaker discusses the homolog of gonadotropin-releasing hormone that regulates the release of various hormones, including gonadotropin and progesterone. The speaker mentions a specific book by Carson as a reference source.

Homolog Regulation

• The homolog of gonadotropin-releasing hormone regulates the release of hormones like gonadotropin and progesterone.