1) The study examined follicular development in human ovaries from birth to age 9. Nine major classes of follicles were identified based on morphology, size, number of granulosa cells, and oocyte growth.
2) The smallest follicles (Class B) contained a non-growing oocyte surrounded by a single layer of flattened cells. The largest follicles (Class F) reached 6 mm and contained a fully grown oocyte of 80 μm surrounded by fluid and granulosa cells.
3) Follicle development followed the same pattern across ages from birth to 9 years, with oocyte growth ceasing at 80 μm while follicles continued growing, forming fluid-filled antra.
Cleavage patterns, fate maps and cell lineages… What can early developmental ...ahejnol
This document discusses early developmental similarities between animal embryos and whether they can be used to determine homology of late larval structures. It notes that while cleavage patterns and early cell lineages may be similar between distantly related animals, the fate of blastomeres can vary between species, making it difficult to infer homology of later tissues based on early development alone. Comparative anatomy, not embryology, is argued to be the primary basis for determining homology. While some larval structures like ciliated bands develop from similar blastomeres in spiralians, variability in developmental processes means early similarities do not guarantee late similarities.
Embryogenesis involves several key processes including cleavage, gastrulation, and organogenesis. Cleavage involves cell division and depends on egg type, being either holoblastic or meroblastic. Gastrulation establishes the three germ layers - ectoderm, mesoderm, and endoderm. Organogenesis then generates specific organs as each germ layer differentiates. A key event is neurulation, which forms the central nervous system from ectoderm. Vertebrates also derive neural crest cells from ectoderm that contribute to diverse structures.
This document summarizes key aspects of the nematode Caenorhabditis elegans. It describes C. elegans' structure as a 1mm long roundworm with 945 cells. It details its life cycle from zygote to adult over 3 days, producing 300 progeny. C. elegans establishes three embryonic axes - anterior-posterior determined by sperm entry point, dorso-ventral set by first cleavage, and left-right by asymmetric cell divisions. The document outlines C. elegans' larval stages and early embryonic development, including axis formation and cell lineage.
This document discusses megasporangium, or ovules, including their types and integuments. It begins by introducing megasporangium and its components. It then describes the six types of ovules classified based on micropyle position: orthotropous, anatropous, hemitropous, campylotropous, amphitropous, and circinotropous. Next, it provides details on each type. Finally, it discusses integuments, which are usually one or two layers and can be unitegmic or bitegmic depending on the plant family. Integuments may also include an aril or become fleshy.
This document outlines a course on developmental biology and teratology. It discusses how pattern formation during embryogenesis is genetically controlled and involves cells responding to morphogen gradients and cell signaling pathways to develop spatial patterns. Key genes involved in pattern formation are homeobox genes, which help specify where anatomical structures will develop. In particular, Hox genes are organized in clusters and control patterning along the anteroposterior body axis. Mutations in genes of pattern formation can lead to various clinical congenital malformations and anomalies.
This document discusses the process of human fertilization and early embryonic development. It begins by explaining that fertilization occurs when a sperm and egg fuse, forming a single-celled zygote. The zygote then undergoes rapid cell division called cleavage to form a solid ball of cells called a morula. By the end of the first week, the morula has further developed into a hollow ball of cells called a blastocyst. The blastocyst begins to implant in the uterine wall, marking the beginning of the embryonic period of development.
A chart showing the fate of each part of an early embryo, in a particular blastula stage is called fate maps. It is done because the correct interpretation of gastrulation is impossible without the knowledge of the position which are the presumptive germinal layers (Ectoderm, Mesoderm and Endoderm) occupy in blastula.
Fate mapping is a method used in developmental biology to study the embryonic origin of various adult tissues and structures. The "fate" of each cell or group of cells is mapped onto the embryo, showing which parts of the embryo will develop into which tissue. When carried out at single-cell resolution, this process is called cell lineage tracing. It is also used to trace the development of tumors.
Developmental biologists are asking questions about how genetic information results in different cell types, how cell division and formation of organized structures are regulated, and how reproductive cells are set apart. They study development through comparative embryology, evolutionary embryology, teratology, and mathematical modeling. Some key concepts are epigenesis versus preformation, germ layers and induction, von Baer's principles of vertebrate development, fate maps, distinguishing analogous and homologous structures, and types of growth models.
Cleavage patterns, fate maps and cell lineages… What can early developmental ...ahejnol
This document discusses early developmental similarities between animal embryos and whether they can be used to determine homology of late larval structures. It notes that while cleavage patterns and early cell lineages may be similar between distantly related animals, the fate of blastomeres can vary between species, making it difficult to infer homology of later tissues based on early development alone. Comparative anatomy, not embryology, is argued to be the primary basis for determining homology. While some larval structures like ciliated bands develop from similar blastomeres in spiralians, variability in developmental processes means early similarities do not guarantee late similarities.
Embryogenesis involves several key processes including cleavage, gastrulation, and organogenesis. Cleavage involves cell division and depends on egg type, being either holoblastic or meroblastic. Gastrulation establishes the three germ layers - ectoderm, mesoderm, and endoderm. Organogenesis then generates specific organs as each germ layer differentiates. A key event is neurulation, which forms the central nervous system from ectoderm. Vertebrates also derive neural crest cells from ectoderm that contribute to diverse structures.
This document summarizes key aspects of the nematode Caenorhabditis elegans. It describes C. elegans' structure as a 1mm long roundworm with 945 cells. It details its life cycle from zygote to adult over 3 days, producing 300 progeny. C. elegans establishes three embryonic axes - anterior-posterior determined by sperm entry point, dorso-ventral set by first cleavage, and left-right by asymmetric cell divisions. The document outlines C. elegans' larval stages and early embryonic development, including axis formation and cell lineage.
This document discusses megasporangium, or ovules, including their types and integuments. It begins by introducing megasporangium and its components. It then describes the six types of ovules classified based on micropyle position: orthotropous, anatropous, hemitropous, campylotropous, amphitropous, and circinotropous. Next, it provides details on each type. Finally, it discusses integuments, which are usually one or two layers and can be unitegmic or bitegmic depending on the plant family. Integuments may also include an aril or become fleshy.
This document outlines a course on developmental biology and teratology. It discusses how pattern formation during embryogenesis is genetically controlled and involves cells responding to morphogen gradients and cell signaling pathways to develop spatial patterns. Key genes involved in pattern formation are homeobox genes, which help specify where anatomical structures will develop. In particular, Hox genes are organized in clusters and control patterning along the anteroposterior body axis. Mutations in genes of pattern formation can lead to various clinical congenital malformations and anomalies.
This document discusses the process of human fertilization and early embryonic development. It begins by explaining that fertilization occurs when a sperm and egg fuse, forming a single-celled zygote. The zygote then undergoes rapid cell division called cleavage to form a solid ball of cells called a morula. By the end of the first week, the morula has further developed into a hollow ball of cells called a blastocyst. The blastocyst begins to implant in the uterine wall, marking the beginning of the embryonic period of development.
A chart showing the fate of each part of an early embryo, in a particular blastula stage is called fate maps. It is done because the correct interpretation of gastrulation is impossible without the knowledge of the position which are the presumptive germinal layers (Ectoderm, Mesoderm and Endoderm) occupy in blastula.
Fate mapping is a method used in developmental biology to study the embryonic origin of various adult tissues and structures. The "fate" of each cell or group of cells is mapped onto the embryo, showing which parts of the embryo will develop into which tissue. When carried out at single-cell resolution, this process is called cell lineage tracing. It is also used to trace the development of tumors.
Developmental biologists are asking questions about how genetic information results in different cell types, how cell division and formation of organized structures are regulated, and how reproductive cells are set apart. They study development through comparative embryology, evolutionary embryology, teratology, and mathematical modeling. Some key concepts are epigenesis versus preformation, germ layers and induction, von Baer's principles of vertebrate development, fate maps, distinguishing analogous and homologous structures, and types of growth models.
Plant embryology is the study of plant development from fertilization to the formation of a mature embryo. Key developments included the discovery of pollen tubes and their role in fertilization in the 17th-18th centuries. In the 19th century, scientists discovered that the embryo forms from the fertilized ovule rather than from the pollen tube tip. Double fertilization, where one sperm fuses with the egg and one with the central cells, was discovered in the late 19th century. The 20th century saw advances in microscopy techniques that improved understanding of embryogenesis. Indian scientists like Maheshwari and Johri made seminal contributions to angiosperm embryology in the 20th century. Modern plant embryology explains
This document provides information on an international course on developmental biology to be held in Paris in October 2011. The course will be held at Pierre and Marie Curie University and the Curie Institute. It is intended for master's and PhD students and will include 3 weeks of practical laboratory sessions and 2 weeks of lectures. The practical sessions will cover topics like early mouse development, chick embryo culture, Drosophila imaginal discs, Xenopus embryos, C. elegans, and zebrafish. The lecture sessions will feature talks from researchers on various topics within developmental biology.
This document discusses monocot and dicot embryogenesis. It describes the key structures and regions of the embryonic axis in monocots and dicots, including the epicotyl, hypocotyl, cotyledons, plumule, and radicle. It also summarizes the different types of dicot embryogenesis based on the contribution of the apical and basal cells, such as the onagrad, asterad, solanad, and chenopodiad types. The embryogenesis process in the monocot Najas is also outlined in detail.
1) The ovary contains a cavity lined with epidermal cells. Ovules develop from these epidermal cells and are contained within the ovary cavity, attached by a stalk called the funiculus.
2) The ovule has four main parts: the nucellus at the center containing sporogenous cells, one or two integuments surrounding the nucellus, the funiculus stalk connecting the ovule to the placenta, and the chalaza where the nucellus, integuments and funiculus merge.
3) A megaspore mother cell within the nucellus undergoes meiosis to form a megaspore, which
This document discusses the processes of reproduction including asexual reproduction, sexual reproduction, gametogenesis, and fertilization. It defines the key terms and describes: (1) the types of asexual and sexual reproduction in single-celled and multi-cellular organisms, (2) the processes of spermatogenesis and oogenesis leading to the formation of gametes, and (3) fertilization which involves the fusion of male and female gametes during syngamy and egg activation to form a zygote. The document provides detailed explanations of these reproductive concepts and processes.
This document provides an overview of the history and techniques of embryology. It discusses how embryology has advanced from early observations to the use of microscopes and experimental techniques. Key developments included the cell theory, theories of preformation and epigenesis, and von Baer's laws of development. Modern techniques allow for prenatal screening and diagnosis using ultrasound, maternal serum screening, amniocentesis, and chorionic villus sampling. Fetal therapy is also possible through transfusions, medications, and even surgery. The field also studies concepts like stem cell potency, differentiation, and regeneration. A variety of methods are used like histology, tracing, transplantation, and culture techniques.
Fate maps are the bases for experimental embryology since they provide researchers with information on which portions of the embryo normally become which larval or adult structures.
Megasporogenesis and megagametogenesisSACHIN KUMAR
The document discusses female gametophyte development in plants. It begins with meiosis forming a haploid megaspore from the diploid megaspore mother cell. This megaspore then develops into the female gametophyte inside the ovule. Transcription factors and hormone gradients influence the development and cell specification of the female gametophyte. The mature female gametophyte contains seven cells - one egg cell, two synergid cells, three antipodal cells, and one central cell formed from two fused polar nuclei. The female gametophyte facilitates fertilization and influences early seed development.
The document discusses early concepts of development including preformation versus epigenesis. It was once thought that the embryo was preformed in the egg, but experiments demonstrated that undifferentiated material in the egg becomes arranged through epigenesis. Key developmental stages are described including fertilization, cleavage, blastula formation, and gastrulation which establishes the three germ layers. Differences in protostome and deuterostome development are outlined, focusing on differences in cleavage, fate determination, and body axis formation. The role of induction in patterning the embryo is also summarized.
Amphibian development begins with fertilization and cortical rotation that establishes dorsal-ventral polarity. Cleavage is holoblastic but unequal, forming a blastula with large yolky cells in the vegetal pole. Gastrulation involves bottle cell invagination, dorsal mesoderm involution, and ectoderm epiboly. The organizer tissue directs body axis formation through beta-catenin signaling in the dorsal region. Left-right asymmetry results from nodal gene expression induced by cilia rotation in the organizer. Amphibians like Xenopus laevis are widely used models for studying these developmental processes.
1. Plant embryogenesis begins with an asymmetric cell division forming an apical and basal cell, followed by further cell divisions forming a rudimentary plant body with an embryonic axis and cotyledons.
2. Key genes involved in embryo development establish the apical-basal and radial patterns, and mutations in these genes disrupt proper embryo formation.
3. In angiosperms, embryo development typically arrests after meristems and cotyledons form, with the seed coat enclosing the dormant embryo until germination conditions are met.
The document describes the structure and development of three types of embryo sacs:
1) Monosporic embryo sacs develop from a single megaspore that undergoes three nuclear divisions without cell wall formation, resulting in an eight-nucleated sac with haploid nuclei.
2) Bisporic embryo sacs form when one cell of the megaspore dyad develops while the other degenerates, with each nucleus dividing twice to create the eight-nucleated sac.
3) Tetrasporic embryo sacs form when the four megaspore nuclei remain in a single cell (coenocyte) and all participate in embryo sac formation.
1. The document discusses the origin and evolution of seeds from pre-ovules. It describes how seeds evolved from megasporangium through a series of steps including the formation of integument and micropyles.
2. Fossil structures from the Devonian and Carboniferous periods called pre-ovules provide evidence for the transition from naked megasporangium to ovules with fused integuments. These pre-ovules had unfused or partially fused integumentary lobes lacking a defined micropyle.
3. The degree of fusion of integumentary lobes in various fossil structures like Genomosperma, Physostoma and Stamnostoma demonstrate the progressive
The document summarizes early development in Drosophila, including embryogenesis, fate determination, and patterning. It discusses how Drosophila undergo holometabolous development through distinct larva, pupa, and adult stages. It then details the processes of fertilization, cleavage, gastrulation, and segmentation that establish the body plan. Key genes that pattern the anterior-posterior and dorsal-ventral axes are also summarized, including maternal effect genes, gap genes, pair-rule genes, segment polarity genes, and homeotic genes.
Developmental biology studies how interacting processes generate an organism's shapes, sizes, and structures from embryo to adult. Early scientists like Hippocrates, Aristotle, and Galen made observations of embryonic development but believed embryos derived nourishment from the mother. In the 1500s, da Vinci conducted early dissections of human fetuses. In the 1600s, Harvey observed chick embryos and concluded the amniotic fluid was absorbed. Later, scientists like Wolff and Pander established epigenesis over preformation through experiments showing structures develop progressively. Spemann's organizer experiments in the 1920s demonstrated induction, wherein one group of cells causes changes in adjacent cells. This established embryology's genetic basis and developmental mechanisms. Cell differentiation,
1) Gametogenesis is the process by which gametes (eggs and sperm) are formed through meiosis in both males and females. Oogenesis occurs in females and produces eggs, while spermatogenesis produces sperm in males.
2) Oogenesis begins with primordial germ cells that develop into oocytes through meiosis. At puberty, a few oocytes complete the first meiotic division and arrest until ovulation. Spermatogenesis occurs through meiosis within the testes, producing spermatids that transform into sperm.
3) Fertilization is the fusion of an egg and sperm. It involves the approximation and fusion of the gametes, restoring the diploid number of chromosomes
This document discusses various aspects of cleavage in fertilized eggs. It begins by defining cleavage as the process of segmentation of the zygote into multiple cells or blastomeres following fertilization. The blastomeres initially remain closely associated but later form a hollow sphere called a blastula. Three key points are made: 1) Cleavage prepares the groundwork for embryonic design by producing cells, 2) It establishes conditions for gastrulation, the next developmental stage. 3) Distinct planes of cell division exist during early cleavage. The document then describes different types of cleavage patterns and their relationships to embryonic cell fate determination.
CAS Biology 11.4 Human Reproduction Part 1Ryan Dougherty
This document discusses human reproduction, including the processes of spermatogenesis and oogenesis. Spermatogenesis is the development of sperm in the testes in five stages - spermatogonia, primary spermatocyte, secondary spermatocyte, spermatid, and sperm. Oogenesis is the development of eggs in the ovaries also through five stages - oogonium, primary oocyte, secondary oocyte, ootid, and ovum. Fertilization then has three main stages - the acrosome reaction, penetration of the egg membrane, and the cortical reaction.
This document discusses embryology and cell division. It begins by defining embryology as the study of developmental processes from a single cell to established organ structures. This occurs through embryogenesis in the first 8 weeks and fetal development from 9 weeks to birth. The document also discusses meiosis, which reduces cells from diploid to haploid and alters germ cell shape, allowing for fertilization and zygote formation. Meiosis is significant because it produces haploid cells, reduces DNA amounts, and generates genetic variability through crossovers during chiasma formation.
- Mammalian development is unique compared to other animals. Cleavages are slow, occurring every 12-24 hours. They also involve rotational cleavage and asynchronous cell divisions.
- A key feature is compaction, where blastomeres cluster tightly at the 8-cell stage. This forms an inner cell mass and outer trophoblast layer. The trophoblast will form the placenta while the inner cell mass develops into the embryo.
- The blastocyst hatches from the zona pellucida in the uterus and implants, aided by proteases and cell adhesion proteins. The trophoblast and inner cell mass then support placental development to obtain nutrients from the mother.
The document describes the development of the placenta and umbilical cord from fertilization through gestation. It discusses the stages of embryogenesis including cleavage, morula, blastula, and gastrula. It then describes the formation and differentiation of the chorionic villi and decidua, and the roles they play in nutrient and gas exchange between mother and fetus. Finally, it summarizes the key functions of the mature placenta including breathing, nutrition, waste removal, and establishing an immunological barrier between mother and fetus.
Plant embryology is the study of plant development from fertilization to the formation of a mature embryo. Key developments included the discovery of pollen tubes and their role in fertilization in the 17th-18th centuries. In the 19th century, scientists discovered that the embryo forms from the fertilized ovule rather than from the pollen tube tip. Double fertilization, where one sperm fuses with the egg and one with the central cells, was discovered in the late 19th century. The 20th century saw advances in microscopy techniques that improved understanding of embryogenesis. Indian scientists like Maheshwari and Johri made seminal contributions to angiosperm embryology in the 20th century. Modern plant embryology explains
This document provides information on an international course on developmental biology to be held in Paris in October 2011. The course will be held at Pierre and Marie Curie University and the Curie Institute. It is intended for master's and PhD students and will include 3 weeks of practical laboratory sessions and 2 weeks of lectures. The practical sessions will cover topics like early mouse development, chick embryo culture, Drosophila imaginal discs, Xenopus embryos, C. elegans, and zebrafish. The lecture sessions will feature talks from researchers on various topics within developmental biology.
This document discusses monocot and dicot embryogenesis. It describes the key structures and regions of the embryonic axis in monocots and dicots, including the epicotyl, hypocotyl, cotyledons, plumule, and radicle. It also summarizes the different types of dicot embryogenesis based on the contribution of the apical and basal cells, such as the onagrad, asterad, solanad, and chenopodiad types. The embryogenesis process in the monocot Najas is also outlined in detail.
1) The ovary contains a cavity lined with epidermal cells. Ovules develop from these epidermal cells and are contained within the ovary cavity, attached by a stalk called the funiculus.
2) The ovule has four main parts: the nucellus at the center containing sporogenous cells, one or two integuments surrounding the nucellus, the funiculus stalk connecting the ovule to the placenta, and the chalaza where the nucellus, integuments and funiculus merge.
3) A megaspore mother cell within the nucellus undergoes meiosis to form a megaspore, which
This document discusses the processes of reproduction including asexual reproduction, sexual reproduction, gametogenesis, and fertilization. It defines the key terms and describes: (1) the types of asexual and sexual reproduction in single-celled and multi-cellular organisms, (2) the processes of spermatogenesis and oogenesis leading to the formation of gametes, and (3) fertilization which involves the fusion of male and female gametes during syngamy and egg activation to form a zygote. The document provides detailed explanations of these reproductive concepts and processes.
This document provides an overview of the history and techniques of embryology. It discusses how embryology has advanced from early observations to the use of microscopes and experimental techniques. Key developments included the cell theory, theories of preformation and epigenesis, and von Baer's laws of development. Modern techniques allow for prenatal screening and diagnosis using ultrasound, maternal serum screening, amniocentesis, and chorionic villus sampling. Fetal therapy is also possible through transfusions, medications, and even surgery. The field also studies concepts like stem cell potency, differentiation, and regeneration. A variety of methods are used like histology, tracing, transplantation, and culture techniques.
Fate maps are the bases for experimental embryology since they provide researchers with information on which portions of the embryo normally become which larval or adult structures.
Megasporogenesis and megagametogenesisSACHIN KUMAR
The document discusses female gametophyte development in plants. It begins with meiosis forming a haploid megaspore from the diploid megaspore mother cell. This megaspore then develops into the female gametophyte inside the ovule. Transcription factors and hormone gradients influence the development and cell specification of the female gametophyte. The mature female gametophyte contains seven cells - one egg cell, two synergid cells, three antipodal cells, and one central cell formed from two fused polar nuclei. The female gametophyte facilitates fertilization and influences early seed development.
The document discusses early concepts of development including preformation versus epigenesis. It was once thought that the embryo was preformed in the egg, but experiments demonstrated that undifferentiated material in the egg becomes arranged through epigenesis. Key developmental stages are described including fertilization, cleavage, blastula formation, and gastrulation which establishes the three germ layers. Differences in protostome and deuterostome development are outlined, focusing on differences in cleavage, fate determination, and body axis formation. The role of induction in patterning the embryo is also summarized.
Amphibian development begins with fertilization and cortical rotation that establishes dorsal-ventral polarity. Cleavage is holoblastic but unequal, forming a blastula with large yolky cells in the vegetal pole. Gastrulation involves bottle cell invagination, dorsal mesoderm involution, and ectoderm epiboly. The organizer tissue directs body axis formation through beta-catenin signaling in the dorsal region. Left-right asymmetry results from nodal gene expression induced by cilia rotation in the organizer. Amphibians like Xenopus laevis are widely used models for studying these developmental processes.
1. Plant embryogenesis begins with an asymmetric cell division forming an apical and basal cell, followed by further cell divisions forming a rudimentary plant body with an embryonic axis and cotyledons.
2. Key genes involved in embryo development establish the apical-basal and radial patterns, and mutations in these genes disrupt proper embryo formation.
3. In angiosperms, embryo development typically arrests after meristems and cotyledons form, with the seed coat enclosing the dormant embryo until germination conditions are met.
The document describes the structure and development of three types of embryo sacs:
1) Monosporic embryo sacs develop from a single megaspore that undergoes three nuclear divisions without cell wall formation, resulting in an eight-nucleated sac with haploid nuclei.
2) Bisporic embryo sacs form when one cell of the megaspore dyad develops while the other degenerates, with each nucleus dividing twice to create the eight-nucleated sac.
3) Tetrasporic embryo sacs form when the four megaspore nuclei remain in a single cell (coenocyte) and all participate in embryo sac formation.
1. The document discusses the origin and evolution of seeds from pre-ovules. It describes how seeds evolved from megasporangium through a series of steps including the formation of integument and micropyles.
2. Fossil structures from the Devonian and Carboniferous periods called pre-ovules provide evidence for the transition from naked megasporangium to ovules with fused integuments. These pre-ovules had unfused or partially fused integumentary lobes lacking a defined micropyle.
3. The degree of fusion of integumentary lobes in various fossil structures like Genomosperma, Physostoma and Stamnostoma demonstrate the progressive
The document summarizes early development in Drosophila, including embryogenesis, fate determination, and patterning. It discusses how Drosophila undergo holometabolous development through distinct larva, pupa, and adult stages. It then details the processes of fertilization, cleavage, gastrulation, and segmentation that establish the body plan. Key genes that pattern the anterior-posterior and dorsal-ventral axes are also summarized, including maternal effect genes, gap genes, pair-rule genes, segment polarity genes, and homeotic genes.
Developmental biology studies how interacting processes generate an organism's shapes, sizes, and structures from embryo to adult. Early scientists like Hippocrates, Aristotle, and Galen made observations of embryonic development but believed embryos derived nourishment from the mother. In the 1500s, da Vinci conducted early dissections of human fetuses. In the 1600s, Harvey observed chick embryos and concluded the amniotic fluid was absorbed. Later, scientists like Wolff and Pander established epigenesis over preformation through experiments showing structures develop progressively. Spemann's organizer experiments in the 1920s demonstrated induction, wherein one group of cells causes changes in adjacent cells. This established embryology's genetic basis and developmental mechanisms. Cell differentiation,
1) Gametogenesis is the process by which gametes (eggs and sperm) are formed through meiosis in both males and females. Oogenesis occurs in females and produces eggs, while spermatogenesis produces sperm in males.
2) Oogenesis begins with primordial germ cells that develop into oocytes through meiosis. At puberty, a few oocytes complete the first meiotic division and arrest until ovulation. Spermatogenesis occurs through meiosis within the testes, producing spermatids that transform into sperm.
3) Fertilization is the fusion of an egg and sperm. It involves the approximation and fusion of the gametes, restoring the diploid number of chromosomes
This document discusses various aspects of cleavage in fertilized eggs. It begins by defining cleavage as the process of segmentation of the zygote into multiple cells or blastomeres following fertilization. The blastomeres initially remain closely associated but later form a hollow sphere called a blastula. Three key points are made: 1) Cleavage prepares the groundwork for embryonic design by producing cells, 2) It establishes conditions for gastrulation, the next developmental stage. 3) Distinct planes of cell division exist during early cleavage. The document then describes different types of cleavage patterns and their relationships to embryonic cell fate determination.
CAS Biology 11.4 Human Reproduction Part 1Ryan Dougherty
This document discusses human reproduction, including the processes of spermatogenesis and oogenesis. Spermatogenesis is the development of sperm in the testes in five stages - spermatogonia, primary spermatocyte, secondary spermatocyte, spermatid, and sperm. Oogenesis is the development of eggs in the ovaries also through five stages - oogonium, primary oocyte, secondary oocyte, ootid, and ovum. Fertilization then has three main stages - the acrosome reaction, penetration of the egg membrane, and the cortical reaction.
This document discusses embryology and cell division. It begins by defining embryology as the study of developmental processes from a single cell to established organ structures. This occurs through embryogenesis in the first 8 weeks and fetal development from 9 weeks to birth. The document also discusses meiosis, which reduces cells from diploid to haploid and alters germ cell shape, allowing for fertilization and zygote formation. Meiosis is significant because it produces haploid cells, reduces DNA amounts, and generates genetic variability through crossovers during chiasma formation.
- Mammalian development is unique compared to other animals. Cleavages are slow, occurring every 12-24 hours. They also involve rotational cleavage and asynchronous cell divisions.
- A key feature is compaction, where blastomeres cluster tightly at the 8-cell stage. This forms an inner cell mass and outer trophoblast layer. The trophoblast will form the placenta while the inner cell mass develops into the embryo.
- The blastocyst hatches from the zona pellucida in the uterus and implants, aided by proteases and cell adhesion proteins. The trophoblast and inner cell mass then support placental development to obtain nutrients from the mother.
The document describes the development of the placenta and umbilical cord from fertilization through gestation. It discusses the stages of embryogenesis including cleavage, morula, blastula, and gastrula. It then describes the formation and differentiation of the chorionic villi and decidua, and the roles they play in nutrient and gas exchange between mother and fetus. Finally, it summarizes the key functions of the mature placenta including breathing, nutrition, waste removal, and establishing an immunological barrier between mother and fetus.
This case study describes a fetus papyraceus (vanishing twin phenomenon) found in a patient who delivered twins at 37 weeks gestation. Fetus papyraceus occurs when one twin dies in the second trimester and is compressed by the growing sac of the surviving twin. The deceased twin in this case was estimated to be 14 weeks gestational age based on measurements of leg and arm bones. The placenta of the deceased twin showed signs of infarction, indicating a lack of maternal blood supply. While the surviving twin was delivered healthy, fetus papyraceus is associated with potential anomalies in the surviving co-twin.
The liver develops from the endoderm-derived hepatic diverticulum which forms the liver bud in the fourth week of development. The liver bud expands and differentiates into the pars hepatica, which develops into the major structures of the liver including hepatocytes and bile ducts, and the pars cystica, which forms the gallbladder and cystic duct. Precise regulation of signaling molecules and transcription factors is required for the differentiation of hepatoblasts and arrangement of liver cells into their functional structures.
This document discusses engineering the microenvironment of ovarian follicles for in vitro culture through the application of tissue engineering principles. It begins with an overview of follicle development in vivo and the current state of in vitro follicle culture systems. Two-dimensional culture systems disrupt follicle architecture, while three-dimensional systems better maintain cell-cell interactions but have room for improvement. The field of tissue engineering can provide tools to better control the biochemical and mechanical signals within engineered follicle culture systems. The challenges of selecting appropriate biomaterials and manipulating their properties to regulate factor transport and mechanical cues throughout follicle development are discussed.
Relative Morphology of Extraembryonic Membranes in Mammals: Their Roles in Hi...Joseph Holson
Presented by John DeSesso and Joseph F. Holson in Symposium I ("A Detective Story: Is the Prenatal Toxicity of a Therapeutic in Rats Relevant to Human Risk?", J.F. Holson and L. B. Pearce, co-chairpersons) at the Forty-Third Annual Meeting of the Teratology Society, Philadelphia, PA, June 26, 2003.
The liver develops from the endoderm of the foregut. During the 4th week, the hepatic diverticulum buds off from the foregut and divides into the pars hepatica and pars cystica. The pars hepatica gives rise to the liver parenchyma of hepatocytes and bile ducts. It expands between the layers of the septum transversum mesenchyme. The pars cystica develops into the gallbladder and cystic duct. By week 8, the basic structure of the liver and biliary tree is established.
Hypospadias is a congenital anomaly where the urethral meatus is located on the ventral side of the penis instead of at the tip. It occurs in about 1 in 150-300 live male births. Diagnosis is based on the location of the ectopic urethral meatus and the presence of ventral penile curvature and an incomplete foreskin. The cause is thought to be a disruption of normal penile development during gestation, which involves the formation and fusion of the urethral folds. Risk factors include premature birth and low birth weight. Associated anomalies include undescended testes and inguinal hernias. More severe forms may be associated with disorders of sexual development.
The document summarizes research on analyzing gene expression in the human endometrium throughout the menstrual cycle using microarray technology. It discusses that the endometrium undergoes regulated changes in its cell types' gene expression across the proliferative, secretory, and menstrual phases of the cycle in response to hormones. Studies have identified phase-specific gene expression profiles and common temporal patterns. The research aims to better understand normal endometrial function and characterize the receptive phase to prevent reproductive failures like infertility.
The document provides information about animal reproduction and development. It discusses topics like asexual and sexual reproduction, embryonic development, formation of germ layers and organs.
The key stages of embryonic development discussed are fertilization, cleavage, blastula formation, gastrulation and organogenesis. Gastrulation involves the formation of three germ layers - ectoderm, mesoderm and endoderm. Organogenesis is the development of organs from the germ layers.
The document also covers post-embryonic development in different life stages from infancy to childhood. It provides details about physical, mental, emotional and social development during these stages.
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Lintern moore
1. FOLLICULAR DEVELOPMENT IN THE INFANT
HUMAN OVARY
SUE LINTERN-MOORE, HANNAH PETERS, G. P. M. MOORE
and M. FABER
The Finsen Laboratory, The Finsen Institute, Copenhagen, Denmark
{Received 12th November 1973)
Summary. The morphology and growth pattern of human ovarian
follicles has been studied between birth and 9 years of age. Follicles
have been classified according to their morphology, diameter, the
diameter of the oocyte and the number of granulosa cells in the widest
cross-section. Nine major classes of follicle were recognized. The smallest,
Class B follicles, contained a non-growing oocyte and were surrounded
by a single layer of flattened granulosa cells. The largest, Class F
follicles, which were up to 6 mm in diameter, contained an oocyte which
had completed growth (80 g=mm) and a large fluid-filled antrum. The
range of follicles and the pattern of oocyte growth in relation to follicle
growth found in the ovary was independent of age during childhood.
Follicular growth and atresia are discussed in the light of current
concepts of gonadal and pituitary function during infancy and child-
hood.
INTRODUCTION
The morphological changes which occur within the human ovary during
infancy and childhood have been described in detail. Maturation of the ovary
is indicated by increases in ovarian weight and size, flattening of the surface
epithelium, development of the tunica albugínea ovarii, changes in the orienta¬
tion and quantity of connective tissue in the stroma and increased vasculariza-
tion (Stevens, 1903; Shaw, 1925; Simkins, 1932; Forbes, 1942; Delson, Lubin,
& Reynolds, 1949; Sauramo, 1954; Boyd & Hamilton, 1955; Curtis, 1962;
Merrill, 1963; Potter, 1963; Mossman, Koering & Ferry, 1964; Van Wagenen
& Simpson, 1965; Valdes-Dapena, 1967; Mossman & Duke, 1973).
The most striking characteristic of the infant ovary is the presence of
follicles in all stages of growth and atresia. The occurrence of antral follicles
(both microscopic and macroscopic) from 7 months after conception onwards
has been reported on numerous occasions. Spivak (1934) reviewed accounts
dating from the early 18th century of 'cystic follicles' in newborn ovaries.
More recently, this subject has been dealt with by Govan & Mukherjee (1950),
Polhemus (1953), Ober & Bernstein (1955), Ahlvin & Bauer (1957), Curtis
(1962), Kraus & Neubecker (1962), Winter (1962) and Merrill (1963).
*
Present address: Department of Zoology, Australian National University, Canberra ACT,
Australia.
53
2. 54 Sue Lintern-Moore et al.
In the present study, the quantitative patterns of oocyte and follicular
growth are investigated during the period of infancy. Using this information,
a classification for the follicle types found in the infant ovary has been derived.
The classification is intended to form a basis for studies of the dynamics of
follicular growth in the human ovary.
MATERIALS AND METHODS
Ovaries were obtained at autopsy from infants and children ranging in age
from birth to 9 years. The specimens were fixed in Bouin's solution, embedded
in paraffin wax and sectioned at 7 µ . Sections were stained with either Harris
haematoxylin and eosin or Heidenhain's Azan.
In order to determine the incidence and sizes of antral follicles in ovaries
at different ages, an initial survey was made of sectioned material obtained
from 400 subjects. From these, a group was selected consisting of nineteen
EXPLANATION OF PLATE 1
Fig. 1. Class A human oocytes (oo—9 to 25 ß diam.) in the transition stages of meiotic
prophase. At birth, these were found either in the extreme outer cortex abutting the
surface epithelium (s.e.) (Fig. la) or in the medullary region of the ovary (Fig. lb).
After 2 months of age, Class A follicles were less abundant. They were mainly found in
medullary nests, surrounded by cells which resembled those of the rete ovarii and were
encapsulated by a complete basement membrane. Age 3 days; 910.
Fig. 2. Class (right) and B/C (left) oocyte nuclei which have entered the resting stage of
diplotene. Class follicles were surrounded by flattened granulosa cells with highly baso-
philic nuclei. Class B/C follicles had both flattened and cuboidal granulosa cells. In
general, the flattened cells surrounded one side of the oocyte and cuboidal cells the other.
Whether the cuboidal cells arise from the flattened granulosa cells or represent a different
cell population is unknown. Oocytes of follicles form the major portion of the oocyte
population in the ovary at any time and constitute the resting pool from which future
follicular growth will occur. They occurred in great abundance in the outer cortex at
birth and thereafter appeared less commonly due not only to an increase in the size of
the ovary but also to atresia (Baker, 1963). Age 5 years; 910.
Fig. 3. A Class C oocyte surrounded by a single complete layer of cuboidal granulosa
cells and a complete basement membrane which separates the granulosa layer from the
adjacent stroma. The stroma surrounding the follicle formed a halo of connective tissue
fibres and fibroblast-like cells. No definitive theca was present. The oocyte had not
commenced growth but the number of follicle cells had increased. Class C follicles were
located deeper in the cortex than those of Classes and B/C and were less frequently found
than the latter. Age 7 years; 910.
Fig. 4. A Class Dj follicle containing a growing oocyte surrounded by two to seven layers
of granulosa cells. The zona pellucida is now present. Class Di follicles were located
deeper in the cortex than those of any of the previous classes. Age 3 years; 910.
Fig. 5. A Class D2 follicle. These follicles had a similar follicle and oocyte size range and
location as Dt but were characterized by a granulosa cell layer containing fluid filled
spaces and Call-Exner (ce.) vacuoles. Age 8 years; 910.
Fig. 6. A Class E follicle. These follicles occurred less frequently than any of the previous
follicle classes and were characterized by a definitive crescent-shaped antrum. The oocyte
had ceased growth in the majority of cases. The wide distribution of follicle sizes (Text-
fig. 5) in this class suggests that fluid accumulation may occur at any stage in follicular
development after the formation of two or more layers of granulosa cells. The theca
(th) may be well vascularized. Age 3 years; 910.
Fig. 7. A Class F follicle. These follicles lay deep in the medullary region of the ovary and
represented the final stage of follicle growth in the infant ovary. They were characterized
by the development of a large fluid-filled antrum and the oocyte, which had ceased
growth, was embedded in a cumulus of granulosa cells. In some cases, the cells of the theca
might be markedly hypertrophied, taking on a partly luteinized appearance. Vasculariza-
tion of the theca was advanced. Part of an atretic Class F follicle (a) is seen to the lower
left. Note the undifferentiated thecal-type interstitial gland cells. Age 8 years; X 146.
4. Follicular development in the infant human ovary 55
normal subjects ranging in age from birth to 9 years, who had died either from
misadventure (eight cases) or acute disease (eleven cases) in which the period
of illness was not longer than 48 hr and its nature considered unlikely to affect
the ovary. The follicle classification is based on measurements made on the
ovaries from this group. Ovary sections were examined under a Zeiss projec¬
tion microscope. Measurements were only made of those follicles which shoved
no apparent signs of atresia or post-mortem degeneration, i.e. the nuclei of
the granulosa cells and oocytes showed no signs of pyknosis and macrophages
were absent (see Baker, 1963). The diameters of the follicle, oocyte and oocyte
nucleus were then obtained using the method described by Mandi & Zucker-
man (1952) and the number of granulosa cells were counted in the widest
cross-section of the follicle. Approximately twenty representatives of each
follicle class were measured in each of the nineteen ovaries. This was not
possible with the larger follicles which occurred much less frequently than the
smaller ones and, in most cases, were atretic.
RESULTS
Incidence and size of antral follicles
The survey of 400 ovaries showed that the range of morphological types of
Text-fig. 1. The relationship between oocyte diameter (µ ) and follicle diameter (ß )
in the infant human ovary. During Phase A of growth, these are positively and signifi¬
cantly correlated (r = +091; <0·001; y = 0·57 + 9-89—for abbreviations, see
Table 1). During Phase B (y = 0·001 + 80·70), the regression coefficient was not signi¬
ficantly different from zero. The point of intersection of the lines of best fit for both sets of
parameters was highly sensitive to small variations in both the regression coefficients, a,
and intercepts, b. The points which fell around the intersection of the two lines were
excluded from the calculations (Mandi & Zuckerman, 1952).
5. 56 Sue Lintern-Moore et al.
follicles present in the ovary was similar regardless of the age of the subject.
Antral follicles were present in 60 % of the newborn ovaries. This frequency
declined between 9 and 28 days of life to 30%, but rose to 100% by the age
of 1 year. Thereafter, antral follicles were always found in the ovary through¬
out infancy and childhood. The mean diameter of antral follicles ranged from
0-2 mm to 6 mm and was independent of age.
Table 1. Coefficients of straight line regression relationships {y=ax + b) between
oocyte diameter(y) or oocyte nuclear diameter (y) and follicle diameter (x) and their
corresponding correlation coefficients (r) for Phase A of growth in twenty normal
human female subjects aged between 3 days and 25 years
No.
Oocyte diameter/follicle diameter ofpairs Oocyte nuclear diameter/follicle
(Phase A) of diameter (Phase A)
measure¬ r* a b
ments
3 days + 0-90 0-47 14-22 100 + 0-87 0-10 8-41
14 days + 0-88 0-64 14-85 160 + 0-92 0-11 813
7 weeks + 0-89 0-49 10-42 105 + 0-79 0-13 8-71
3 months + 0-93 0-66 8-36 100 + 0-77 0-10 1219
4 months + 0-80 0-53 7-09 98 + 0-76 009 10-09
4J months + 0·94 0-58 9-16 97 + 0-82 0-11 9-50
11 months + 0-94 0-51 13-21 120 + 0-85 0-11 10-11
1 year + 0-98 0-44 15-11 118 + 0-90 0-14 8-30
1 year 4 months + 0-91 0-49 12-78 115 + 0-84 0-12 8-93
1 year 9 months + 0-84 0-52 8-84 90 + 0·72 0-09 10-05
2 years + 0-97 0-69 9-97 160 + 0-88 0-14 8-81
2 years + 0-99 0-57 9-77 100 + 0-94 0-15 8-18
3 years + 0·96 0-48 15-39 180 + 0-66 0-09 10-97
4 years + 0-97 0-52 13-30 103 4-0-78 0-19 11-55
5 years + 0-87 0-49 11-61 100 + 0-89 0-13 9-07
7 years + 0·97 0-48 15-78 100 + 0-87 0-09 12-69
8 years + 0-95 0-52 9-83 190 + 0-94 0-15 8-98
8 years + 0-95 0-52 8-01 102 4-0-94 0-11 9-33
9 years + 0-97 0-55 9-52 100 4-0-94 0-13 9-05
25 years + 0-99 0-55 9-32 100 + 0-93 0-10 11-05
Pooled data
Phase A + 0-91 0-57 9-89 2238 + 0-82 0-12 9-17
Phase 0-001 i 80-70 35 0-0004f 25-55
* All values of r significant at the 0-001% level. Not significantly different from zero.
Values for a, b and r for pooled data (excluding that from the 25-year-old subject) are also presented
for both Phases A and of growth.
Growth of the oocyte and follicle
In order to establish the pattern of oocyte growth in relation to follicle
growth, oocyte and follicle diameters were compared using measurements
pooled from the nineteen ovaries studied (Text-fig. 1). Oocyte diameter and
follicle diameter were found to be positively and linearly correlated until the
oocyte reached a mean diameter of 80 µ (range 60 to 120 /mi) at a follicle
diameter of 124 µ (growth phase A). Thereafter, the oocyte ceased to grow
whilst follicular growth continued (growth phase B). A similar biphasic
relationship was found to exist between oocyte nuclear diameter and follicle
diameter. The oocyte nucleus reached a maximum diameter of 26 /tm (range
6. Follicular development in the infant human ovary 57
22 to 35 µ ) at a follicle diameter of 128 µ (Table 1). Thus, the oocyte and
its nucleus ceased growth at approximately the same stage of follicle develop¬
ment and their diameters were positively and linearly correlated with each
other (Text-fig. 2).
The validity of pooling data from each of the different subjects has been
investigated in Table 1. The values of a (regression coefficient) and b (inter¬
cept) for Phase A of the relationships between oocyte and follicle diameter
and oocyte nuclear diameter and follicle diameter varied between individuals
Text-fig. 2. Oocyte diameter (/an) and oocyte nuclear diameter (µ ) in the infant
human ovary were positively and linearly correlated (r =
+0-92; P< 0-001; y =
3-2X-43-7).
but no age trend could be detected. It was not possible to obtain sufficient
measurements of follicle and oocyte diameters for Phase of growth from
individual subjects since most of these follicles within each ovary were atretic.
The relationship between follicle diameter and the number of granulosa
cells in the widest cross-section of the follicle was curvilinear (Text-fig. 3). In
follicles greater than 200 /¡m in diameter, the accumulation of follicular fluid
rather than the proliferation of the granulosa cells appeared to determine the
follicle size.
7. 58 Sue Lintern-Moore et al.
Follicleclassification
The morphological pattern of follicular development in the infant ovary is
depicted in Text-fig. 4. In Text-figs 5 and 6, the pooled data from all the ovaries
are plotted as histograms to demonstrate the distribution of follicle classes in
relation to follicle and oocyte diameter. With the exception of Class A follicles
(PI. 1, Fig. 1), all of these types of follicles were found in the nineteen ovaries
studied.
Text-fig. 3. The relationship between the number of granulosa cells in the widest cross-
section of the follicle (logt0) and follicle diameter (ßm) in the infant human ovary.
There was a considerable overlap in oocyte size between follicle classes.
Furthermore, aparticular follicle size can encompass a number of morpho¬
logical classes. Fluid accumulation could commence in follicles with as few as
forty granulosa cells in the widest cross-section (Class / 2) and a defined
antrum when the number of cells reached 100 (Class E). Similarly, the oocyte
might cease growth (Text-fig. 1) at a follicle diameter which included those
of both Class D and E morphology (Text-fig. 5). This might include multi-
laminar follicles with no fluid accumulation.
Based upon these observations, follicular growth in the infant human ovary
can be summarized as follows. The preliminary stages of oogénesis are com¬
pleted by 6 months post partum since oogonia and oocytes in early meiotic
prophase (Class A) have disappeared (PI. 1, Figs la and b). Class follicles
8. Text-fig. 4. Schematic representation of follicular growth in the ovary of infancy and
childhood. The classification of follicles was based upon follicle diameter, oocyte diameter,
the number of granulosa cells in the widest cross-section and follicular morphology.
Class A, which represents oocytes in the early pre-diplotene stages of meiotic pro-
phase (Pi. 1, Figs la and lb), is not included. Follicular growth occurred first during the
transition from Class to Class G. Oocyte growth commenced during the Class C/D to D
transition. Oocyte growth in general ceased during the progression from Class D to Class
E but in exceptional cases occurred as early as Class C/D (Text-fig. 6).
100
50
-
D,
B/C C/DI D¡ D,
26to50/j.m 5ltolOO/j.m 101 to 200/¿m 201 to 6000µ/
Follicle diameter
Text-fig. 5. The distribution of follicle classes in relation to follicle diameter (ßm) in
the infant human ovary.
9. 60 Sue Lintern-Moore et al.
(PI. 1, Fig. 2) are in the resting stage of prophase (diplotene) and form the
major portion of the oocyte population at any age. They constitute a pool
from which follicular growth will occur throughout life. Follicular growth is
first evident from the multiplication of granulosa cells in Class B/C and C
follicles (PL 1, Figs 2 and 3) and oocyte growth begins in Class C/D (Text-
fig. 4). With further granulosa cell proliferation and oocyte growth, follicles
become Class D type in which fluid may begin to accumulate between the cells
of the follicular envelope and thecal tissue to differentiate (PI. 1, Figs 4 and 5).
With the appearance of a definitive antrum, the follicles are designated as
Class E (PI. 1, Fig. 6). During the Class D to E transition, oocyte growth
ceases (Text-figs 1 and 6). Class F follicles show further fluid accumulation
and the thecal cells may be markedly hypertrophied. This class represents the
largest follicle type present in the infant ovary (PI. 1, Fig. 7).
100
50
B/C C/D
C/D D2
C/D D2 I—
13 to 39 /¿m 40 to 80 µ 81 to 120 ¿¿m
Oocyte diameter
Text-fig. 6. The distribution of follicle classes in relation to oocyte diameter (µ ) in
the infant human ovary.
DISCUSSION
The high incidence of antral follicles in the ovaries of newborn girls appears
to be unrelated to any pathological state in mother or child. Ahlvin & Bauer
(1957) suggested a relationship between the presence of antral follicles in the
newborn ovary and diabetes in the mother, but this was not supported by the
more extensive survey of Kraus & Neubecker (1962). Furthermore, Spivak
(1934) and Ober & Bernstein (1955) found no correlation between hyper-
plasia and hypertrophy of the newborn uterine endometrium and the presence
of antral follicles in the ovary. They concluded that although the morphology
of the newborn uterus may reflect maternal steroid levels, the degree of ovarian
development was independent of these factors. Advanced stages of follicular
growth are also found in the ovaries of other newborn mammals which are
born in a comparatively precocious state (Kellas, Van Lennep & Amoroso,
1958; Perry & Rowlands, 1962; van Wagenen & Simpson, 1965).
10. Folliculardevelopment in the infant human ovary 61
As in other mammals (Brambell, 1928; Parkes, 1932; Zuckerman & Parkes,
1932), the pattern of oocyte growth in relation to follicular growth in the
infant human ovary is biphasic (Text-fig. 1) and individual (although not
age-dependent) variations may exist in both the regression coefficient, a, and
the intercept, b, for phase A of growth (Table 1). Similar individual variations
also occur in the rhesus monkey and the rat (Green & Zuckerman, 1947;
Mandi & Zuckerman, 1952). In the human infant, the oocyte reaches a
maximum diameter of 80 µ (range 60 to 120 /tin) at a follicular diameter of
124 µ . Thereafter, follicular growth continues whilst the rate of oocyte
growth approaches zero. The value for a in phase A of growth (0-57) is within
the range recorded for other mammals, i.e. 0-14 for the pig and 0-64 for the
shrew (see Parkes, 1932; Green & Zuckerman, 1947). Furthermore, the overall
values for both a and b for phase A for the infant ovary did not differ signifi¬
cantly from those obtained for the single adult ovary studied during the
course of this work (Table 1) or those obtained by Green & Zuckerman (1951)
for a 6-year-old ovary. The close similarity in many different mammalian
species between the maximum diameter achieved by the oocyte at the end of
growth phase A and the corresponding follicle diameter has been noted
previously (Parkes, 1932; Brambell, 1956). The possible functional significance
of this observation in relation to synthetic activity of the oocyte nucleus has
been discussed elsewhere (Moore & Lintern-Moore, 1974).
No evidence for ovulation was found in any of the 400 ovaries studied. The
maximum diameter achieved by the oocyte during infancy (60 to 120 µ ) is
less than that (120 to 190 µ ) reported for freshly ovulated human ova (Pincus
& Saunders, 1937; Hamilton, 1944). Although some of the disparity in size
can be accounted for
by shrinkage on fixation (Hamilton, 1944; Menkin &
Rock, 1948), it is possible that the fully grown oocyte of infancy does not
develop to the preovulatory dimensions found in the adult. Similarly, the
maximum diameter of antral follicles encountered routinely in the infant
ovary (5 to 6 mm) is considerably less than the values of 10 to 15 mm reported
for a full-sized adult follicle (Watzka, 1957). Thus, it is concluded that antral
follicles in the infant human ovary do not achieve preovulatory size and all of
the apparently normal growing follicles seen, in the absence of a resting stage
beyond Class B, must, at some stage in development, degenerate. Certainly,
all classes of follicles described for the infant ovary were encountered in atretic
forms (see also Potter, 1963; Valdes-Dapena, 1967) and the pattern of follicular
atresia appears to resemble closely that described for non-ovulatory follicles
in the adult Macaca mulatta (Koering, 1969).
The data indicate that follicular growth and degeneration in the human
ovary occurs continuously throughout infancy and childhood. It may be
pertinent to consider whether a functional association between the gonadal-
pituitary-hypothalamic axis is also present. Normal prepubertal children have
circulating gonadotrophin levels which are considerably lower than those
recorded during puberty and adulthood. They are, nevertheless, in excess of
those recorded in hypo-pituitary subjects, lower than those of 5- to 10-year-
old subjects with gonadal dysgenesis and higher in females than in males.
Similarly, although oestradiol-17/? levels are also very low, prepubertal subjects
11. 62 Sue Lintern-Moore et al.
appear to be more sensitive to low doses of ethinyl oestradiol (as reflected by
FSH excretion) than do those who have reached puberty (Kulin, Grumbach &
Kaplan, 1969; Buckler & Clayton, 1970; Penny, Guyda, Baghdassarian,
Johanson & Blizzard, 1970; Root, Moshang, Bongiovanni & Eberlein, 1970;
Sizoneko, Burr, Kaplan & Grumbach, 1970; Jenner, Kelch, Kaplan & Grum¬
bach, 1972; Kelch, Grumbach & Kaplan, 1972; Lee, Midgley & Jaffe, 1972).
These data suggest that a gonadal-pituitary relationship may exist during the
prepubertal period. To support this, Roth, Kelch, Kaplan & Grumbach (1972)
have shown that LH-releasing factor (LH-RF) stimulates the release of similar
amounts of FSH in prepubertal, pubertal and adult subjects. By contrast, LH
production and release only became significant at puberty. Thus it appears
that during infancy and childhood a special, highly sensitive form of the
gonadal-pituitary feedback system may be operating. The nature of this
system and its relation to the pattern of follicular growth reported here is not
known at the present time.
ACKNOWLEDGMENTS
This study was supported by the NATO Scientific Committee and was carried
out in partial fulfilment of EURATOM Contract 120-73-1 BIODK. We
wish to thank the pathologists who kindly supplied ovaries used in this study :
Dr J. M. Bouton, Alderhey Children's Hospital, Liverpool; Dr H. B. Marsden,
Royal Manchester Children's Hospital, Manchester; Dr A. D. Bain, Royal
Hospital for Sick Children, Edinburgh; Dr A. E. Claireaux, Hospital for
Sick Children, London; Dr G. Molz, Kanton Hospital, Zürich; Dr .
Barzilai, Rambam Government Hospital, Haifa; Dr G. Kohn and Dr J.
Chatten, Children's Hospital, Philadelphia; Dr M. J. Barry, Our Lady's
Hospital for Sick Children, Dublin.
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