This document provides an overview of basic embryology and early human development from a lecture series by Dr. Beda Olabu. It begins with an introduction to embryology as the study of prenatal development from gametogenesis through birth. It then outlines the scope of the basic embryology lectures, which will cover topics like gametogenesis, fertilization, the first two weeks of development and implantation. The document provides learning outcomes and details for each topic.
Embryology is the study of prenatal human development from fertilization through the first 8 weeks of embryonic development. There are three main stages of prenatal development: pre-embryonic (first 2 weeks), embryonic (weeks 3-8), and fetal (remaining weeks until birth). The document defines key terms like germ cells and somatic cells, and describes the processes of meiosis, mitosis, gametogenesis (spermatogenesis and oogenesis), and fertilization.
During the second week of development, the bilaminar germ disc undergoes several key events: 1) implantation of the blastocyst in the uterus, 2) differentiation of the trophoblast into syncytiotrophoblast and cytotrophoblast layers, establishing utero-placental circulation, and 3) differentiation of the embryoblast into hypoblast and epiblast layers, forming the amniotic and exocoelomic cavities. The trophoblast also begins forming primary villi and the extraembryonic mesoderm develops between the trophoblast and embryoblast, forming the chorionic cavity.
the process by which a bilaminar germ disc is formed within the second week of development. second week is a week of two's. development and clinical implications or correlates. the formation of the 2 fluid cavities
The document summarizes key events during the third week of human embryonic development. It describes how the bilaminar embryonic disc undergoes gastrulation to form the trilaminar embryo, with the three germ layers. It also discusses neurulation, somite formation, and the folding of the embryo. The main developments are the formation of the primitive streak, notochord, and somites, which establish the body plan and organize the developing systems and structures.
During the second week of embryo development:
- The blastocyst is partially or completely embedded in the endometrial lining, with the trophoblast differentiating into layers. The embryoblast also divides into the hypoblast and epiblast.
- A small cavity, the future amniotic cavity, appears in the epiblast. The syncytiotrophoblast penetrates deeper into the endometrial stroma and establishes the first circulatory system between the embryo and mother.
- By the end of the second week, the extraembryonic mesoderm and chorionic cavity have formed, and primary villi with syncytial covering have begun to develop in the chorionic cavity.
1. The document summarizes the key embryonic changes that occur during the first and second weeks of pregnancy. It describes the processes of fertilization, zygote formation, implantation, and development of the inner cell mass and outer cell mass.
2. During the second week, the inner cell mass rearranges to form two layers (the bilaminar germ disk) that will develop into the embryo, while the outer cell mass forms the trophoblasts and primary villus, which are precursors to the placenta.
3. A hormone called HCG is produced from the syncytiotrophoblast cells starting around 8 days after fertilization, and can be detected in pregnancy tests.
General embryology introduction ( chapter 1)saahil0000
Embryology is the study of the development of an organism from conception to birth. The prenatal period spans 38 weeks and includes the embryonic period from fertilization to 8 weeks, and the fetal period from 9 weeks until birth. During the embryonic period, the three germ layers are established which will give rise to all organs. Organogenesis occurs from weeks 4 through 8. The fetal period involves growth and maturation of organs. A basic understanding of embryology assists with learning anatomy and diagnosing congenital conditions.
This document describes human development from fertilization through the third week. In the first week, fertilization occurs along with cleavage and the formation of the morula and blastocyst. In the second week, implantation of the blastocyst occurs along with changes forming the chorionic vesicle. The third week involves the formation of three types of chorionic villi from the chorion and gastrulation forming the trilaminar disc.
Embryology is the study of prenatal human development from fertilization through the first 8 weeks of embryonic development. There are three main stages of prenatal development: pre-embryonic (first 2 weeks), embryonic (weeks 3-8), and fetal (remaining weeks until birth). The document defines key terms like germ cells and somatic cells, and describes the processes of meiosis, mitosis, gametogenesis (spermatogenesis and oogenesis), and fertilization.
During the second week of development, the bilaminar germ disc undergoes several key events: 1) implantation of the blastocyst in the uterus, 2) differentiation of the trophoblast into syncytiotrophoblast and cytotrophoblast layers, establishing utero-placental circulation, and 3) differentiation of the embryoblast into hypoblast and epiblast layers, forming the amniotic and exocoelomic cavities. The trophoblast also begins forming primary villi and the extraembryonic mesoderm develops between the trophoblast and embryoblast, forming the chorionic cavity.
the process by which a bilaminar germ disc is formed within the second week of development. second week is a week of two's. development and clinical implications or correlates. the formation of the 2 fluid cavities
The document summarizes key events during the third week of human embryonic development. It describes how the bilaminar embryonic disc undergoes gastrulation to form the trilaminar embryo, with the three germ layers. It also discusses neurulation, somite formation, and the folding of the embryo. The main developments are the formation of the primitive streak, notochord, and somites, which establish the body plan and organize the developing systems and structures.
During the second week of embryo development:
- The blastocyst is partially or completely embedded in the endometrial lining, with the trophoblast differentiating into layers. The embryoblast also divides into the hypoblast and epiblast.
- A small cavity, the future amniotic cavity, appears in the epiblast. The syncytiotrophoblast penetrates deeper into the endometrial stroma and establishes the first circulatory system between the embryo and mother.
- By the end of the second week, the extraembryonic mesoderm and chorionic cavity have formed, and primary villi with syncytial covering have begun to develop in the chorionic cavity.
1. The document summarizes the key embryonic changes that occur during the first and second weeks of pregnancy. It describes the processes of fertilization, zygote formation, implantation, and development of the inner cell mass and outer cell mass.
2. During the second week, the inner cell mass rearranges to form two layers (the bilaminar germ disk) that will develop into the embryo, while the outer cell mass forms the trophoblasts and primary villus, which are precursors to the placenta.
3. A hormone called HCG is produced from the syncytiotrophoblast cells starting around 8 days after fertilization, and can be detected in pregnancy tests.
General embryology introduction ( chapter 1)saahil0000
Embryology is the study of the development of an organism from conception to birth. The prenatal period spans 38 weeks and includes the embryonic period from fertilization to 8 weeks, and the fetal period from 9 weeks until birth. During the embryonic period, the three germ layers are established which will give rise to all organs. Organogenesis occurs from weeks 4 through 8. The fetal period involves growth and maturation of organs. A basic understanding of embryology assists with learning anatomy and diagnosing congenital conditions.
This document describes human development from fertilization through the third week. In the first week, fertilization occurs along with cleavage and the formation of the morula and blastocyst. In the second week, implantation of the blastocyst occurs along with changes forming the chorionic vesicle. The third week involves the formation of three types of chorionic villi from the chorion and gastrulation forming the trilaminar disc.
Somite differentiation and neural crestVharsha Haran
Neural crest cells arise from the ectoderm layer and give rise to diverse cell lineages including melanocytes, craniofacial cartilage and bone, smooth muscle, and neurons. They have multipotent capability, migrate throughout the embryo, and are precisely regulated. The neural crest can be divided into four main regions that develop into different structures and tissues. Somites form from paraxial mesoderm and later split into dermatomes, myotomes, syndetomes, and sclerotomes which give rise to skin, skeletal muscle, tendons and cartilage, and bone, respectively.
1) The document discusses the key stages in the first week of human development including fertilization, cleavage, formation of the morula and blastocyst, and implantation.
2) Fertilization involves the fusion of an ovum and spermatozoa to form a zygote, which occurs in the fallopian tube. The zygote then undergoes cleavage divisions as it moves through the uterine tube.
3) By day 5-6, the blastocyst has formed with an inner cell mass and outer trophoblast layer. The blastocyst implants in the endometrium around day 7, initiating formation of the placenta and decidua. Abnormal implantation can result in
Somites are bilaterally paired segments of paraxial mesoderm that form along the embryonic axis and give rise to important structures. Somites subdivide into sclerotomes, myotomes and dermatomes that form vertebrae, ribs, muscle, tendons and skin. Somite formation depends on a "clock mechanism" where paraxial mesoderm segments into somites according to their position in a regulated process. Within each somite, cells are specified based on location and retain flexibility before differentiating into somite-derived tissues through epithelialization and mesenchymal transformation processes.
During the third week of development, gastrulation occurs where the three germ layers (ectoderm, mesoderm, endoderm) are formed. The notochord also begins developing from epiblast cells that ingress through the primitive streak and primitive node. These cells form the notochordal process which then fuses with endoderm and detaches to form the definitive notochord cord between the ectoderm and endoderm. The mesoderm organizes into three segments - paraxial, intermediate, and lateral plate mesoderm - which will give rise to muscles, skeleton, urinary/genital systems, and other tissues.
Gastrulation is the process that establishes the three germ layers - ectoderm, mesoderm, and endoderm - in the embryo. It begins with the formation of the primitive streak on the surface of the epiblast. Cells from the epiblast migrate through the primitive streak and invaginate inward, some forming endoderm and others mesoderm between the endoderm and remaining ectoderm. This process spreads the germ layers throughout the embryo. Disruptions can cause abnormalities like caudal dysgenesis where insufficient mesoderm is formed, impacting lower limb and urogenital development. Rare tumors can also form from remnants of the primitive streak.
The white matter of the cerebrum contains three main types of nerve fibers: commissural fibers, association fibers, and projection fibers. Commissural fibers such as the corpus callosum connect the two cerebral hemispheres. Association fibers like the superior longitudinal bundle connect different regions within the same hemisphere. Projection fibers including those in the internal capsule connect the cerebral cortex to lower brain centers. The internal capsule specifically contains fibers that project to and from the cortex and plays an important role in motor function. Damage to the internal capsule can thus cause contralateral hemiplegia.
The document summarizes the process of gastrulation in humans. It discusses how the embryo develops two germ layers, the epiblast and hypoblast, just before implantation. It describes the formation of the primitive streak around day 15, which defines the body axes. Cells migrate through the primitive streak during gastrulation to form the definitive endoderm, intraembryonic mesoderm, and ectoderm. Key cellular processes in gastrulation include epithelial-to-mesenchymal transition and convergent extension.
The document summarizes key events that occur during the first two weeks of human development. During the first week, fertilization occurs along with cleavage and blastocyst formation. The blastocyst undergoes implantation in the uterus. In the second week, implantation is completed and the bilaminar embryonic disc forms. Extraembryonic structures like the amniotic cavity and yolk sac also develop in the second week.
During the third week of development, the bilaminar germ disc differentiates into a trilaminar embryo through the process of gastrulation. Gastrulation begins with the formation of the primitive streak along the midline of the epiblast. Cells from the epiblast migrate through the primitive streak and groove to form the mesoderm and endoderm germ layers. This results in the formation of the trilaminar embryo consisting of the ectoderm, mesoderm and endoderm germ layers. Concurrently, structures like the notochord, allantois and intraembryonic coelom begin developing.
The document discusses embryonic development from the 4th to 8th week. It describes how the neural tube forms from the neural plate and folds, and how it eventually develops into the brain and spinal cord. It also discusses the fate of the neural crest in forming various structures. The ectoderm gives rise to other structures like the skin, ears and eyes. As the embryo folds and bends upon itself, its shape changes from a flat disc to a cylinder. This folding results in the gut and membranes that will aid in nutrient exchange for the growing embryo.
During the 4th week of development, the embryo undergoes longitudinal and transverse folding which transforms it from a flat disc into a curved tube. This folding incorporates the yolk sac endoderm to form the gut tube and divides the coelom into the thoracic and abdominal cavities. It also repositions structures like the heart and mouth opening. By the end of the 4th week, the embryo has prominent head and tail folds, limb buds, and many organ systems are established.
This document summarizes the key stages in human reproduction from ovulation through implantation. It describes how ovulation is triggered by hormones, followed by fertilization if sperm penetrate the egg's barriers. The zygote then undergoes cell division as it develops into a blastocyst, which implants in the uterine wall. Successful implantation depends on cellular interactions between the trophoblast and endometrium.
The document discusses the process of fertilization and early embryonic development. It begins with an overview of the events of fertilization, including sperm penetration through the corona radiata and zona pellucida, the cortical reaction, and fusion of the male and female pronuclei. It then describes the early cleavage stages, where the zygote undergoes rapid cell divisions without growth to form a morula, followed by blastulation and implantation in the uterus. Key events include capacitation of sperm, the acrosomal reaction, prevention of polyspermy, and formation of the blastocyst from the inner cell mass and trophoblast.
The document summarizes the embryogenesis of the central nervous system (CNS). It describes how the CNS begins as a neural plate that folds to form a neural tube within the embryo. Within the neural tube, stem cells generate neurons and glia, which are the major cell types of the nervous system. The brain develops within the cranial cavity and the spinal cord develops within the spinal canal. The neural tube is completed by 4 weeks of development through the process of primary and secondary neuralization. The spinal cord extends along the spinal canal but ends at the lumbar region in adults. Neuroregeneration refers to the regrowth of nervous tissues and differs between the peripheral and central nervous systems.
Bilaminar and trilaminar embryonic discs form during the third week of gestation through the process of gastrulation. In a bilaminar disc, the inner cell mass differentiates into two germ layers - an outer ectoderm layer and inner endoderm layer. As development continues, the disc becomes pear-shaped and the primitive streak and notochord form along the central axis to establish the embryo's orientation. Mesoderm cells then migrate between the ectoderm and endoderm to form the trilaminar disc consisting of all three germ layers.
Spermatogenesis is the process by which sperm cells are produced in the testes in males. It involves the transformation of spermatogonia into mature sperm through two stages: spermatocytogenesis where primordial germ cells develop into spermatids, and spermiogenesis where spermatids are transformed into mature sperm. In humans, it takes approximately 74 days to complete and produces around 300 million sperm cells daily. Oogenesis is the similar process that occurs in females within the ovaries to produce eggs.
This document provides an outline for a lecture on general embryology. It covers topics like erythropoiesis, gastrulation, formation of the three germ layers, neurulation, somite formation, and differentiation of the mesoderm and endoderm. During gastrulation, cells migrate through the primitive streak to form the ectoderm, mesoderm and endoderm layers. The notochord forms in the midline and guides development. Neurulation involves the formation of the neural plate and tube which will become the central nervous system. Somites form from the paraxial mesoderm and differentiate into sclerotome, myotome and dermatome. The intermediate and lateral plate mes
Gastrulation begins with the formation of the primitive streak, primitive node, buccopharyngeal membrane, and cloacal membrane. Epiblast cells migrate through the primitive streak and invaginate to form the endoderm, mesoderm, and remaining ectoderm layers. The notochord develops from the primitive pit through the stages of the notochordal process, canal, and plate. It will eventually form the primitive axial skeleton and nucleus pulposus of intervertebral discs.
The pons is part of the brainstem located inferior to the midbrain and superior to the medulla oblongata. It has anterior and posterior surfaces. Notable features on the anterior surface include the emergence of the trigeminal nerve and the abducent, facial, and vestibulocochlear nerves between the pons and medulla. The internal structure of the pons contains basal and tegmental parts, which can be seen on transverse sections passing through the caudal and cranial parts. Key structures visible in these sections include cranial nerve nuclei, fiber tracts such as the medial lemniscus, and pontine nuclei.
The document provides an overview of basic human embryology. It discusses the early stages of development from fertilization through the formation of the zygote and pre-embryonic period. It also describes the embryonic and fetal periods, when major organs develop and the fetus continues to grow and mature, respectively. Key terms related to embryology and reproductive structures are defined. The processes of gametogenesis, fertilization, and early pregnancy are summarized.
Somite differentiation and neural crestVharsha Haran
Neural crest cells arise from the ectoderm layer and give rise to diverse cell lineages including melanocytes, craniofacial cartilage and bone, smooth muscle, and neurons. They have multipotent capability, migrate throughout the embryo, and are precisely regulated. The neural crest can be divided into four main regions that develop into different structures and tissues. Somites form from paraxial mesoderm and later split into dermatomes, myotomes, syndetomes, and sclerotomes which give rise to skin, skeletal muscle, tendons and cartilage, and bone, respectively.
1) The document discusses the key stages in the first week of human development including fertilization, cleavage, formation of the morula and blastocyst, and implantation.
2) Fertilization involves the fusion of an ovum and spermatozoa to form a zygote, which occurs in the fallopian tube. The zygote then undergoes cleavage divisions as it moves through the uterine tube.
3) By day 5-6, the blastocyst has formed with an inner cell mass and outer trophoblast layer. The blastocyst implants in the endometrium around day 7, initiating formation of the placenta and decidua. Abnormal implantation can result in
Somites are bilaterally paired segments of paraxial mesoderm that form along the embryonic axis and give rise to important structures. Somites subdivide into sclerotomes, myotomes and dermatomes that form vertebrae, ribs, muscle, tendons and skin. Somite formation depends on a "clock mechanism" where paraxial mesoderm segments into somites according to their position in a regulated process. Within each somite, cells are specified based on location and retain flexibility before differentiating into somite-derived tissues through epithelialization and mesenchymal transformation processes.
During the third week of development, gastrulation occurs where the three germ layers (ectoderm, mesoderm, endoderm) are formed. The notochord also begins developing from epiblast cells that ingress through the primitive streak and primitive node. These cells form the notochordal process which then fuses with endoderm and detaches to form the definitive notochord cord between the ectoderm and endoderm. The mesoderm organizes into three segments - paraxial, intermediate, and lateral plate mesoderm - which will give rise to muscles, skeleton, urinary/genital systems, and other tissues.
Gastrulation is the process that establishes the three germ layers - ectoderm, mesoderm, and endoderm - in the embryo. It begins with the formation of the primitive streak on the surface of the epiblast. Cells from the epiblast migrate through the primitive streak and invaginate inward, some forming endoderm and others mesoderm between the endoderm and remaining ectoderm. This process spreads the germ layers throughout the embryo. Disruptions can cause abnormalities like caudal dysgenesis where insufficient mesoderm is formed, impacting lower limb and urogenital development. Rare tumors can also form from remnants of the primitive streak.
The white matter of the cerebrum contains three main types of nerve fibers: commissural fibers, association fibers, and projection fibers. Commissural fibers such as the corpus callosum connect the two cerebral hemispheres. Association fibers like the superior longitudinal bundle connect different regions within the same hemisphere. Projection fibers including those in the internal capsule connect the cerebral cortex to lower brain centers. The internal capsule specifically contains fibers that project to and from the cortex and plays an important role in motor function. Damage to the internal capsule can thus cause contralateral hemiplegia.
The document summarizes the process of gastrulation in humans. It discusses how the embryo develops two germ layers, the epiblast and hypoblast, just before implantation. It describes the formation of the primitive streak around day 15, which defines the body axes. Cells migrate through the primitive streak during gastrulation to form the definitive endoderm, intraembryonic mesoderm, and ectoderm. Key cellular processes in gastrulation include epithelial-to-mesenchymal transition and convergent extension.
The document summarizes key events that occur during the first two weeks of human development. During the first week, fertilization occurs along with cleavage and blastocyst formation. The blastocyst undergoes implantation in the uterus. In the second week, implantation is completed and the bilaminar embryonic disc forms. Extraembryonic structures like the amniotic cavity and yolk sac also develop in the second week.
During the third week of development, the bilaminar germ disc differentiates into a trilaminar embryo through the process of gastrulation. Gastrulation begins with the formation of the primitive streak along the midline of the epiblast. Cells from the epiblast migrate through the primitive streak and groove to form the mesoderm and endoderm germ layers. This results in the formation of the trilaminar embryo consisting of the ectoderm, mesoderm and endoderm germ layers. Concurrently, structures like the notochord, allantois and intraembryonic coelom begin developing.
The document discusses embryonic development from the 4th to 8th week. It describes how the neural tube forms from the neural plate and folds, and how it eventually develops into the brain and spinal cord. It also discusses the fate of the neural crest in forming various structures. The ectoderm gives rise to other structures like the skin, ears and eyes. As the embryo folds and bends upon itself, its shape changes from a flat disc to a cylinder. This folding results in the gut and membranes that will aid in nutrient exchange for the growing embryo.
During the 4th week of development, the embryo undergoes longitudinal and transverse folding which transforms it from a flat disc into a curved tube. This folding incorporates the yolk sac endoderm to form the gut tube and divides the coelom into the thoracic and abdominal cavities. It also repositions structures like the heart and mouth opening. By the end of the 4th week, the embryo has prominent head and tail folds, limb buds, and many organ systems are established.
This document summarizes the key stages in human reproduction from ovulation through implantation. It describes how ovulation is triggered by hormones, followed by fertilization if sperm penetrate the egg's barriers. The zygote then undergoes cell division as it develops into a blastocyst, which implants in the uterine wall. Successful implantation depends on cellular interactions between the trophoblast and endometrium.
The document discusses the process of fertilization and early embryonic development. It begins with an overview of the events of fertilization, including sperm penetration through the corona radiata and zona pellucida, the cortical reaction, and fusion of the male and female pronuclei. It then describes the early cleavage stages, where the zygote undergoes rapid cell divisions without growth to form a morula, followed by blastulation and implantation in the uterus. Key events include capacitation of sperm, the acrosomal reaction, prevention of polyspermy, and formation of the blastocyst from the inner cell mass and trophoblast.
The document summarizes the embryogenesis of the central nervous system (CNS). It describes how the CNS begins as a neural plate that folds to form a neural tube within the embryo. Within the neural tube, stem cells generate neurons and glia, which are the major cell types of the nervous system. The brain develops within the cranial cavity and the spinal cord develops within the spinal canal. The neural tube is completed by 4 weeks of development through the process of primary and secondary neuralization. The spinal cord extends along the spinal canal but ends at the lumbar region in adults. Neuroregeneration refers to the regrowth of nervous tissues and differs between the peripheral and central nervous systems.
Bilaminar and trilaminar embryonic discs form during the third week of gestation through the process of gastrulation. In a bilaminar disc, the inner cell mass differentiates into two germ layers - an outer ectoderm layer and inner endoderm layer. As development continues, the disc becomes pear-shaped and the primitive streak and notochord form along the central axis to establish the embryo's orientation. Mesoderm cells then migrate between the ectoderm and endoderm to form the trilaminar disc consisting of all three germ layers.
Spermatogenesis is the process by which sperm cells are produced in the testes in males. It involves the transformation of spermatogonia into mature sperm through two stages: spermatocytogenesis where primordial germ cells develop into spermatids, and spermiogenesis where spermatids are transformed into mature sperm. In humans, it takes approximately 74 days to complete and produces around 300 million sperm cells daily. Oogenesis is the similar process that occurs in females within the ovaries to produce eggs.
This document provides an outline for a lecture on general embryology. It covers topics like erythropoiesis, gastrulation, formation of the three germ layers, neurulation, somite formation, and differentiation of the mesoderm and endoderm. During gastrulation, cells migrate through the primitive streak to form the ectoderm, mesoderm and endoderm layers. The notochord forms in the midline and guides development. Neurulation involves the formation of the neural plate and tube which will become the central nervous system. Somites form from the paraxial mesoderm and differentiate into sclerotome, myotome and dermatome. The intermediate and lateral plate mes
Gastrulation begins with the formation of the primitive streak, primitive node, buccopharyngeal membrane, and cloacal membrane. Epiblast cells migrate through the primitive streak and invaginate to form the endoderm, mesoderm, and remaining ectoderm layers. The notochord develops from the primitive pit through the stages of the notochordal process, canal, and plate. It will eventually form the primitive axial skeleton and nucleus pulposus of intervertebral discs.
The pons is part of the brainstem located inferior to the midbrain and superior to the medulla oblongata. It has anterior and posterior surfaces. Notable features on the anterior surface include the emergence of the trigeminal nerve and the abducent, facial, and vestibulocochlear nerves between the pons and medulla. The internal structure of the pons contains basal and tegmental parts, which can be seen on transverse sections passing through the caudal and cranial parts. Key structures visible in these sections include cranial nerve nuclei, fiber tracts such as the medial lemniscus, and pontine nuclei.
The document provides an overview of basic human embryology. It discusses the early stages of development from fertilization through the formation of the zygote and pre-embryonic period. It also describes the embryonic and fetal periods, when major organs develop and the fetus continues to grow and mature, respectively. Key terms related to embryology and reproductive structures are defined. The processes of gametogenesis, fertilization, and early pregnancy are summarized.
Anomalies of the first and second branchial archesDr Medical
https://userupload.net/8n9v7tg9jkl1
Anomalies of the branchial arches are the second most common congenital lesions of the head and neck in children [1]. They may present as cysts, sinus tracts, fistulae or cartilaginous remnants and present with typical clinical and radiological patterns dependent on which arch is involved. The course of a particular branchial anomaly is caudal to the structures derived from the corresponding arch and dorsal to the structures that develop from the following arch. Branchial anomalies are further typed into cysts, sinuses, and fistulas.
This document provides information on human reproduction and development from conception through infancy. It discusses the basic concepts of heredity including genes, DNA, and chromosomes. It describes the biological sources of developmental disabilities that can occur during critical periods of pregnancy in the germinal phase, embryonic phase, and fetal phase due to genetic disorders, chromosomal abnormalities, infections, or physical trauma during birth. The document also outlines typical developmental milestones in gross motor skills, receptive language, and expressive language during infancy and early childhood.
Oogenesis, spermatogenesis, and embryogenesis are the processes of gamete and embryo formation. Oogenesis involves the growth of oogonia in females from fetal development through puberty, forming primary oocytes arrested in meiosis. Spermatogenesis in males involves spermatogonia differentiating into spermatocytes through meiosis and spermiogenesis. Embryogenesis begins with fertilization and cleavage, forming a blastocyst through implantation and gastrulation, establishing the three germ layers. Over 8 weeks, all major organ systems begin developing as the embryo undergoes folding and segmentation.
Embryology is the study of development from fertilization to organ formation. In humans, this encompasses the first 8 weeks and includes key stages like gastrulation and organogenesis. The development involves 5 processes - gametogenesis, fertilization, cleavage, gastrulation, and organogenesis. During these stages, the cells proliferate, migrate, and differentiate to form the three germ layers and subsequent organs. Fetal membranes like the amnion, chorion, yolk sac and allantois also develop to nourish and protect the growing embryo.
Determining pregnancy in cattle is an important
management tool. The ability to determine
pregnancy can allow us to make timely
culling decisions and focus the resources of our
operation on sound, reliable breeders.
USMLE GENERAL EMBRYOLOGY 008 First week of development A embryo .pdfAHMED ASHOUR
The initial week of embryonic development is a vital period commencing with fertilization, leading to the creation of the zygote and early cell divisions. It's noteworthy that, throughout this week, the developing embryo remains in the pre-implantation stage, journeying from the fallopian tube toward the uterus. Key events such as fertilization, cleavage, and the formation of the blastocyst are crucial for the embryo's early development.
These events lay the foundation for subsequent processes in the following weeks. The successful implantation of the blastocyst into the uterus marks the transition from the first week to the second week of embryonic development.
1. Fertilization involves the fusion of an egg and sperm, forming a zygote with a full set of chromosomes. The zygote then undergoes cleavage, forming a morula by day 3 and a blastocyst by day 5 as it travels down the fallopian tube.
2. The blastocyst implants in the uterine wall around 1 week after fertilization. The trophoblast cells of the blastocyst initiate implantation and will later form the placenta, while the inner cell mass gives rise to the embryo.
3. During the first week, the zygote develops from a single cell through cleavage, compaction, blastulation and begins implantation in the uterus.
Oogenesis is the process by which female gametes (ova/eggs) are formed. It begins during fetal development with the formation of oogonia, which undergo mitosis to form primary oocytes. Primary oocytes then enter meiosis I but arrest in prophase I. After puberty, one oocyte is selected each month to complete meiosis I and II, forming a haploid egg and polar bodies. The remaining oocytes remain arrested until death. Oogenesis involves three phases - multiplication, growth, and maturation - resulting in a mature ovum containing half the number of chromosomes, organelles and nutrients required for embryonic development.
This document provides an overview of an embryology discussion lecture at Kilimanjaro Christian Medical University College. The lecture will cover introduction to embryology and discuss topics like congenital anomalies, their causes, and management. It provides objectives of understanding embryology and developmental periods. It also discusses gametogenesis and lists common terms in embryology. Potential causes of birth defects including genetic and environmental factors are mentioned. Recent advances in areas like IVF and stem cell research are also summarized. Recommended textbooks for the course are provided at the end.
This document discusses human embryology and development from fertilization through birth. It describes the embryonic and fetal periods, the stages of development including fertilization, cleavage, gastrulation, and organogenesis. Key events like formation of the three germ layers and development of the placenta, amnion, chorion, and allantois are summarized. The roles of hormones and growth of the major organs by the third trimester are highlighted. Birth and the role of oxytocin in labor are briefly mentioned.
This document provides an overview of a lecture on embryology given at Kilimanjaro Christian Medical University College. It discusses the general course objectives of understanding embryology, including comprehending anatomy and diagnosing abnormalities. Specific topics covered include cleft lip and palate, causes of birth defects such as genetic factors and environmental teratogens. The document also reviews key events in reproductive cell development like spermatogenesis and oogenesis, as well as early human development from fertilization through implantation.
Developmental biology is the study of how organisms grow and develop. It involves processes like gametogenesis, fertilization, growth, differentiation, pattern formation and morphogenesis. Gametogenesis refers to the formation of gametes or sex cells through meiosis. In spermatogenesis, spermatogonia undergo mitosis and meiosis to form spermatids that then differentiate into spermatozoa. In oogenesis, oogonia undergo mitosis and meiosis to form a secondary oocyte and first polar body, with the secondary oocyte then undergoing a second meiotic division. Fertilization occurs when a sperm fuses with an ovum, forming a zygote. Development then progresses through
Embryology of head and neck - arun omfspptxRishiKodali2
1. The document discusses the embryology of the head and neck, covering topics like gametogenesis, fertilization, cleavage, blastulation, implantation, and the development of structures in the head and neck region like the skull, face, palate, and teeth.
2. It describes the three main phases of prenatal development - the preimplantation, embryonic, and fetal periods - and the key processes during each like formation of the germ layers and organogenesis.
3. Various congenital abnormalities are discussed, especially chromosomal abnormalities like Down syndrome, and the effects of teratogens on development.
newborn infant is a very important topic for pg entrance.....so all about it has been discussed in detail as required for pg entrance....do make use of it...
Gametogenesis is the process by which mature gametes (sperm or ovum) are formed from primitive germ cells through mitotic and meiotic cell divisions. In males, spermatogenesis occurs in the seminiferous tubules of the testes and produces sperm from puberty until old age. In females, oogenesis begins during fetal development and arrests in meiosis until puberty, when ovulation and formation of ova resumes monthly in the ovaries until menopause. Both processes reduce the number of chromosomes from diploid to haploid and develop the cytoplasmic features necessary for fertilization.
This document outlines various factors that can impact embryo implantation and cause implantation failure, including embryo quality issues, endometrial issues, and other uterine factors. It discusses grading of embryos and the implantation process. Common causes of implantation failure are discussed such as poor embryo quality due to sperm or egg issues, endometrial problems, uterine issues like fibroids, and endocrine or immune disorders. Investigations for implantation failure and methods for improving embryo quality and the endometrium are also outlined. The role of diagnostic hysteroscopy in evaluating and treating intrauterine abnormalities prior to IVF is examined along with evidence for treatments of specific issues like polyps, fibroids, septa, synechia, and hydros
This document summarizes the hormonal effects on vaginal cytology and the interpretation of vaginal smear samples. It describes how hormones influence the cells seen in smears throughout a woman's life. Estrogen causes maturation of superficial cells while progesterone increases intermediate cells. The maturation index is used to assess the ratio of cell types. Smears change over the menstrual cycle and with life events like pregnancy and menopause due to varying hormone levels. Precise collection and interpreting samples in the context of a patient's history is important for evaluation.
This document discusses normal hindgut development and abnormalities that can occur. The hindgut develops from the caudal end of the endoderm and gives rise to the distal colon, rectum, and upper anal canal. The lower anal canal develops from ectoderm. The cloaca divides into the urogenital sinus and anorectal canal. Failure of this division can result in anomalies like imperforate anus. The enteric nervous system arises from vagal neural crest cells that migrate through the gut. Failure of this migration causes Hirschsprung's disease. Genes involved in neural crest cell development like RET, EDNRB, and SOX10 are associated with Hirschsprung's disease
The scalp consists of 5 layers: 1) skin, 2) dense connective tissue, 3) epicranial aponeurosis (galea aponeurotica), 4) loose connective tissue, and 5) pericranium. Layer 4 contains loose areolar tissue and important emissary veins that allow scalp infections to spread to intracranial venous sinuses, potentially causing venous sinus thrombosis. Deep scalp wounds gape widely when the epicranial aponeurosis is divided due to tension produced by the occipitofrontalis muscle. The scalp has surgical utility for access flaps like coronal flaps and reconstruction flaps for scalp and craniofacial
The scalp consists of 5 layers: 1) skin, 2) dense connective tissue, 3) epicranial aponeurosis (galea aponeurotica), 4) loose connective tissue, and 5) pericranium. Layer 4 contains loose areolar tissue and important emissary veins that allow scalp infections to spread to intracranial venous sinuses, potentially causing venous sinus thrombosis. Deep scalp wounds gape widely when the epicranial aponeurosis is divided due to tension produced by the occipitofrontalis muscle. The scalp has surgical utility for access flaps like the coronal flap and reconstruction flaps for scalp and craniofacial
3. Organization of the Nervous system.pptStanleyOdira
The document summarizes the organization and cells of the nervous system. It discusses the divisions of the nervous system into the brain, spinal cord, spinal nerves. It describes the two main cell types as neurons and neuroglia. It outlines the four main functions of neurons as receiving and integrating inputs, generating nerve impulses, conducting impulses, and transmitting information to target cells. It also discusses the different ways neurons can be classified including by function, structure, shape, and size.
This document discusses human papillomaviruses (HPV), which are a family of viruses that can cause warts or cancers. There are over 300 genotypes of HPV that can infect humans, with about 40 affecting the anogenital region. HPV is commonly transmitted sexually and is the most common sexually transmitted infection. Most HPV infections do not cause symptoms and clear on their own, but some high-risk genotypes like HPV 16 and 18 can cause cancers, especially cervical cancer, which they are responsible for in about 50-75% and 12-25% of cases, respectively. While there is no cure for HPV, symptoms can be treated and vaccination can prevent infection from some high-risk types.
5A. BRAINSTEM AND CRANIAL NERVES-1.pptStanleyOdira
The document discusses the brainstem and cranial nerves. It begins by listing the objectives and providing an overview of the components, external features, and internal features of the brainstem. It then discusses the 12 cranial nerves in detail, including their nuclei, functional components, and applied anatomy. The document concludes by answering 5 questions about cranial nerve nuclei and brainstem structures associated with specific cranial nerves.
This document contains a review of various topics related to human anatomy. It includes 21 multiple choice and short answer questions covering topics like:
1. Identification of anatomical structures and their abnormalities or anomalies.
2. Embryological development and derivatives of various structures.
3. Identification of skull bones, sutures, foramina and cranial nerves.
4. Veins, dural sinuses, arteries and nerves of the head and neck.
5. External features, support structures, blood supply, drainage and development of the spinal cord.
This document provides an introduction to virology. It defines viruses and their structure. Viruses are submicroscopic obligate intracellular parasites that contain genetic material surrounded by a protein coat. They can only replicate inside living cells. The complete virus particle is called a virion. Viruses are too small to be seen by light microscopes and have a fixed morphology like helical, polyhedral or spherical shapes. They contain either DNA or RNA and have a protein capsid that may contain an envelope. Viruses must infect host cells to replicate since they lack their own metabolic functions.
16. FACE AND ASSOCIATED STRUCTURES-1.pptxStanleyOdira
This document describes the development of the facial skeleton and associated structures from weeks 3-8 of gestation. It discusses how the face develops from primordial tissues including the frontonasal process, maxillary processes, and mandibular processes. The nose develops from nasal placodes that form pits and sacs. Fusion of surrounding tissues forms the lips, palate, and separates the oral and nasal cavities. The temporomandibular joint also develops during this period through mesenchymal condensation and growth.
4. GAMETOGENESIS-2c FERTILIZATION AND FEMALE CYCLES.pdfStanleyOdira
Gametogenesis is the formation of male and female gametes in the gonads. Spermatogenesis occurs in the testes and takes 64 days to form sperm through phases including spermatocytogenesis, meiosis, and spermiogenesis. Oogenesis begins before birth with oocyte formation and the first meiotic division is arrested until after puberty. Fertilization is the fusion of sperm and egg, occurring in the fallopian tubes in a process involving capacitation, the acrosome reaction, penetration of the egg coats, zona reaction, and fusion of pronuclei to form a zygote.
This document provides an overview of topics to be covered related to cell membrane structure and function. It will discuss the plasma membrane, lipids and proteins that make up the membrane, and functions of integral membrane proteins including receptors, adhesion molecules, and channels. Specific topics to be covered are the structure and properties of the cell membrane, transport across the membrane, and cellular communication.
This document discusses viral infections of the central nervous system, focusing on poliovirus and rabies virus. It provides details on the pathogenesis, transmission, clinical presentation, diagnosis and prevention of infections caused by these two viruses. Poliovirus is an enterovirus that causes poliomyelitis. It is transmitted via the fecal-oral route. Rabies virus is transmitted via bites from infected mammals and causes rabies, an acute neurological disease. Both infections can be prevented through vaccination.
This document discusses the classification of viruses. It describes that viruses can be classified based on their nucleic acid composition (DNA or RNA), whether they are enveloped or not, and the disease they cause. It provides examples of virus families under each classification type. The document also discusses several virus classification systems used historically and currently, including the Baltimore classification system which is favored by molecular biologists as it groups viruses based on their replication strategies.
1. Introduction to structure of biomolecules lecture Lecture 2-1.pptxStanleyOdira
The document discusses the hierarchy of biological organization from the molecular to cellular level. It begins by defining biomolecules as organic compounds formed from key elements like carbon, hydrogen, nitrogen, and oxygen. These biomolecules include micromolecules like amino acids, sugars, and fatty acids that combine to form macromolecules like proteins, carbohydrates, lipids, and nucleic acids. These macromolecules further assemble into supramolecular complexes and organelles, with the basic unit of organization being the cell. The hierarchical organization and precise integration of biochemical reactions in cells allows living organisms to maintain a high level of internal order despite being inherently unstable systems.
1. Nucleotides and the nucleic acids-1.pptStanleyOdira
Nucleotides are the basic building blocks of nucleic acids DNA and RNA. They consist of 3 components - a nitrogenous base (purine or pyrimidine), a 5-carbon sugar (ribose in RNA and deoxyribose in DNA), and 1-3 phosphate groups. The 4 main nucleotides that make up DNA are deoxyadenosine, deoxyguanosine, deoxycytidine, and thymidine. Nucleotides bond together via phosphodiester linkages between the phosphate group of one nucleotide and the sugar group of the next, forming polynucleotide chains called DNA and RNA which store and transmit genetic information in living cells.
This document discusses normal hindgut development and abnormalities that can occur. The hindgut normally develops into the distal colon, rectum, and upper anal canal from the caudal end of the hindgut. The lower anal canal develops from ectoderm. Abnormalities like imperforate anus can occur if the urorectal septum fails to develop. The enteric nervous system arises from neural crest cells that migrate into the gut. Hirschsprung's disease results when these cells fail to colonize a portion of the gut, leaving it aganglionic. Several genes have been identified that are involved in hindgut development and Hirschsprung's disease when mutated.
The document discusses amino acids, the building blocks of proteins. It describes the basic structure of an amino acid, which consists of a central carbon atom bonded to an amino group, carboxyl group, hydrogen atom, and variable R group. The 20 standard amino acids that make up proteins are specified. The amino acids are classified based on properties of their R groups, including polarity and charge. The document also discusses how amino acids join together via peptide bonds to form polypeptides and proteins, and the four levels of protein structure that determine a protein's function.
The parotid gland is the largest salivary gland located below and in front of the external ear. It is enclosed in connective tissue capsules and surrounded by the parotid bed. The facial nerve passes through the gland dividing it into superficial and deep lobes. The parotid duct exits the gland and opens into the mouth opposite the upper second molar. Structures passing through or related to the gland include the facial nerve, retromandibular vein and auriculotemporal nerve. The gland is supplied by the external carotid artery and drained by the retromandibular vein and parotid lymph nodes.
The ear is divided into the external, middle, and inner ear. The external ear collects sound waves and directs them through the external auditory canal to the tympanic membrane. The middle ear contains the ossicles that amplify vibrations before passing them to the inner ear. The inner ear contains the cochlea for hearing and vestibular system for balance. Within these structures are specialized hair cells that detect mechanical stimuli and transduce them into electrical signals via stereocilia on their surfaces.
T1L3 ORGANIZATION OF THE THYROID AND PARATHYROID GLANDS.pptxStanleyOdira
The thyroid and parathyroid glands are located in the neck. The thyroid gland contains follicles made up of follicular cells that synthesize thyroid hormones from iodinated thyroglobulin. The parathyroid glands contain chief cells that secrete parathyroid hormone to regulate calcium levels. Both glands are surrounded by capsules containing blood vessels and nerves and have distinct cell types that carry out important endocrine functions.
Histololgy of Female Reproductive System.pptxAyeshaZaid1
Dive into an in-depth exploration of the histological structure of female reproductive system with this comprehensive lecture. Presented by Dr. Ayesha Irfan, Assistant Professor of Anatomy, this presentation covers the Gross anatomy and functional histology of the female reproductive organs. Ideal for students, educators, and anyone interested in medical science, this lecture provides clear explanations, detailed diagrams, and valuable insights into female reproductive system. Enhance your knowledge and understanding of this essential aspect of human biology.
- Video recording of this lecture in English language: https://youtu.be/kqbnxVAZs-0
- Video recording of this lecture in Arabic language: https://youtu.be/SINlygW1Mpc
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
TEST BANK For Community Health Nursing A Canadian Perspective, 5th Edition by...Donc Test
TEST BANK For Community Health Nursing A Canadian Perspective, 5th Edition by Stamler, Verified Chapters 1 - 33, Complete Newest Version Community Health Nursing A Canadian Perspective, 5th Edition by Stamler, Verified Chapters 1 - 33, Complete Newest Version Community Health Nursing A Canadian Perspective, 5th Edition by Stamler Community Health Nursing A Canadian Perspective, 5th Edition TEST BANK by Stamler Test Bank For Community Health Nursing A Canadian Perspective, 5th Edition Pdf Chapters Download Test Bank For Community Health Nursing A Canadian Perspective, 5th Edition Pdf Download Stuvia Test Bank For Community Health Nursing A Canadian Perspective, 5th Edition Study Guide Test Bank For Community Health Nursing A Canadian Perspective, 5th Edition Ebook Download Stuvia Test Bank For Community Health Nursing A Canadian Perspective, 5th Edition Questions and Answers Quizlet Test Bank For Community Health Nursing A Canadian Perspective, 5th Edition Studocu Test Bank For Community Health Nursing A Canadian Perspective, 5th Edition Quizlet Test Bank For Community Health Nursing A Canadian Perspective, 5th Edition Stuvia Community Health Nursing A Canadian Perspective, 5th Edition Pdf Chapters Download Community Health Nursing A Canadian Perspective, 5th Edition Pdf Download Course Hero Community Health Nursing A Canadian Perspective, 5th Edition Answers Quizlet Community Health Nursing A Canadian Perspective, 5th Edition Ebook Download Course hero Community Health Nursing A Canadian Perspective, 5th Edition Questions and Answers Community Health Nursing A Canadian Perspective, 5th Edition Studocu Community Health Nursing A Canadian Perspective, 5th Edition Quizlet Community Health Nursing A Canadian Perspective, 5th Edition Stuvia Community Health Nursing A Canadian Perspective, 5th Edition Test Bank Pdf Chapters Download Community Health Nursing A Canadian Perspective, 5th Edition Test Bank Pdf Download Stuvia Community Health Nursing A Canadian Perspective, 5th Edition Test Bank Study Guide Questions and Answers Community Health Nursing A Canadian Perspective, 5th Edition Test Bank Ebook Download Stuvia Community Health Nursing A Canadian Perspective, 5th Edition Test Bank Questions Quizlet Community Health Nursing A Canadian Perspective, 5th Edition Test Bank Studocu Community Health Nursing A Canadian Perspective, 5th Edition Test Bank Quizlet Community Health Nursing A Canadian Perspective, 5th Edition Test Bank Stuvia
Osteoporosis - Definition , Evaluation and Management .pdfJim Jacob Roy
Osteoporosis is an increasing cause of morbidity among the elderly.
In this document , a brief outline of osteoporosis is given , including the risk factors of osteoporosis fractures , the indications for testing bone mineral density and the management of osteoporosis
These lecture slides, by Dr Sidra Arshad, offer a quick overview of the physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar lead (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
6. Describe the flow of current around the heart during the cardiac cycle
7. Discuss the placement and polarity of the leads of electrocardiograph
8. Describe the normal electrocardiograms recorded from the limb leads and explain the physiological basis of the different records that are obtained
9. Define mean electrical vector (axis) of the heart and give the normal range
10. Define the mean QRS vector
11. Describe the axes of leads (hexagonal reference system)
12. Comprehend the vectorial analysis of the normal ECG
13. Determine the mean electrical axis of the ventricular QRS and appreciate the mean axis deviation
14. Explain the concepts of current of injury, J point, and their significance
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. Chapter 3, Cardiology Explained, https://www.ncbi.nlm.nih.gov/books/NBK2214/
7. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
share - Lions, tigers, AI and health misinformation, oh my!.pptxTina Purnat
• Pitfalls and pivots needed to use AI effectively in public health
• Evidence-based strategies to address health misinformation effectively
• Building trust with communities online and offline
• Equipping health professionals to address questions, concerns and health misinformation
• Assessing risk and mitigating harm from adverse health narratives in communities, health workforce and health system
Clinic ^%[+27633867063*Abortion Pills For Sale In Tembisa Central19various
Clinic ^%[+27633867063*Abortion Pills For Sale In Tembisa Central Clinic ^%[+27633867063*Abortion Pills For Sale In Tembisa CentralClinic ^%[+27633867063*Abortion Pills For Sale In Tembisa CentralClinic ^%[+27633867063*Abortion Pills For Sale In Tembisa CentralClinic ^%[+27633867063*Abortion Pills For Sale In Tembisa Central
3. INTRODUCTION
Embryology* is the study of morphological changes
or processes that occur prenatally
Spans from gametogenesis until birth
Focusses on both the normal and the abnormal
developmental processes
Helps us to understand the anatomical basis of
congenital anomalies
3
Dr. Beda Olabu: Introduction to Embryology
4. INTRODUCTION
Overview of prenatal developmental periods:
Before conception:
Gametogenesis
Fertilization
After conception:
Pre-embryonic period
Embryonic period
Foetal period
Dr. Beda Olabu: Introduction to Embryology
5. INTRODUCTION
Basic embryology*
Focuses on the general principles of embryology and the
events of the early developmental stages
Systemic embryology*
Development of various body organs, according to their
organ systems
5
Dr. Beda Olabu: Introduction to Embryology
7. LECTURE SCOPE OF BASIC EMBRYOLOGY
1. Gametogenesis
2. Fertilization and its results
3. Female reproductive
cycles*
4. 1st week of development
5. Implantation & 2nd week
of development
6. Mechanisms of twinning
7. Gastrulation & derivatives
of the three germ layers
8. Neurulation process and
neural tube defects*
9. Foetal membranes and
the placenta
10. Principles of teratology
11. The foetal period
Dr. Beda Olabu: Basic Embryology
9. GAMETOGENESIS
Formation and development of the gametes
Occurs within the gonads (testis and ovary)
Spermatogenesis – Formation of sperms
Oogenesis – Formation of the ovum
9
Dr. Beda Olabu: Basic Embryology Series
10. LEARNING OUTCOMES
1. Explain the key steps in the process of spermatogenesis
2. Explain the key steps in the process of oogenesis
3. State the differences between spermatogenesis and
oogenesis
4. Highlight clinical disorders related to the process of
gametogenesis
10
Dr. Beda Olabu: Basic Embryology Series
11. PRIMORDIAL GERM CELLS
Embryonic cells that migrate into
the embryonic gonad during its
development
Become stem cells of gametes in
their respective gonads
PGCs are pluripotent cells that
arise from the walls of the yolk
sac and allantois
Dr. Beda Olabu: Basic Embryology Series
12. SPERMATOGENESIS
Occurs within the seminiferous
tubules of the testis
The process begins at puberty
Continues throughout life
It takes about 2 months to form
a single sperm
The most efficient temperature
for spermatogenesis is 34° C
The developing sperms are
supported by the Sertoli cells
12
Dr. Beda Olabu: Basic Embryology Series
15. PARTS OF A MATURE SPERM
A = Head
B = Neck
C = Acrosome
X = Middle piece
Y = Principle
piece
Z = End piece
15
Dr. Beda Olabu: Basic Embryology Series
16. COMMON SPERM DISORDERS
Determined by semen
analysis
1. Teratospermia
2. Aspermia
3. Hypospermia
4. Oligospermia
5. Azoospermia
6. Asthenozoospermia
16
Dr. Beda Olabu: Basic Embryology Series
17. OOGENESIS
Takes place in the ovarian
cortex
The process begins prenatally
for all the developing oocytes
Oocyte’s meiotic cell division is
however arrested at Prophase I
The meiotic division proceeds in
“monthly” cycles after puberty
17
Dr. Beda Olabu: Basic Embryology Series
18. OOGENESIS
Multiple oocytes are
stimulated each month
Development occurs
during the 1st half of
the woman’s cycle,
then ovulation occurs
18
Dr. Beda Olabu: Basic Embryology Series
19. OOGENESIS
The oocyte is surrounded by an increasing number of
supporting cells, termed the follicular cells
19
20. Oogonia
Primary oocytes
Mitotic cell division
Formation of the
zona pellucida
Primordial Germ Cells
Differentiation
Surrounded by
the follicular cells
21. Primary oocytes
Meiosis I
Secondary oocytes
1st Meiotic arrest [P1]
Birth → Puberty
Cyclic completion
Meiosis II
2nd Meiotic arrest [M2]
Ovulation occurs
Fertilization by a sperm
Mature ovum
22. PARTS OF THE MATURE (GRAAFIAN) FOLLICLE
1.Secondary oocyte
2.Zona pellucida
3.Corona radiata
4.Cumulus oophorous
5.Granulosa cells
6.Follicular antrum
7.Theca interna
What is corpus luteum?
Dr. Beda Olabu: Basic Embryology Series
23. THE CORPUS LUTEUM
Remnants of the mature
follicle after ovulation
Consists of Granulosa
lutein & theca lutein cells
Secrete progesterone
hormone
23
Dr. Beda Olabu: Basic Embryology Series
24. OVERVIEW OF GAMETOGENESIS
SPERMATOGENESIS:
Takes place in the testis
Begins after puberty and takes
about 2 months, at 34 degrees
Supported by the Sertoli cells
Primordial germ cells →
spermatogonia → primary
spermatocytes → secondary
spermatocytes → spermatids →
spermatozoa
24
Dr. Beda Olabu: Basic Embryology Series
25. OVERVIEW OF GAMETOGENESIS
OOGENESIS:
Takes place in the ovary
Begins prenatally but is arrested,
and is completed in cycles after
puberty
Ovum is surrounded by follicular
cells and the zona pellucida
Primordial germ cells → oogonia
→ primary oocyte → secondary
oocyte → ovum
25
Dr. Beda Olabu: Basic Embryology Series
26. CLASS DISCUSSION
Outline the differences between
oogenesis and spermatogenesis
26
Dr. Beda Olabu: Basic Embryology Series
27. CLASS DISCUSSION
27
SPERMATOGENESIS OOGENESIS
Starts at puberty Starts prenatally
No meiotic arrest Two meiotic arrests
Lasts about 2 months Lasts many years
Equal meiotic division Unequal meiotic division
4 viable cells 1 viable & polar bodies
29. CLINICAL CORRELATION
29
Teratomas:
Germ cell tumors arising from
ectopic pluripotent stem cells
Contain multiple tissue lines
Dr. Beda Olabu: Basic Embryology Series
What would happen if PGCs do not migrate into the
developing gonad?
31. LEARNING OUTCOMES
1. Define fertilization and state where it occurs
2. Explain the sequence of events during the
process of fertilization
3. State the various outcomes of fertilization
4. Highlight the common clinical correlations
31
Dr. Beda Olabu: Basic Embryology Series
32. FERTILIZATION
Fusion of the sperm & the
ovum to form the zygote
Occurs in the ampulla of the
Fallopian tube
Illustrate parts of the Fallopian
tube using a diagram*
32
Dr. Beda Olabu: Basic Embryology Series
33. PARTS OF THE FALLOPIAN TUBE
33
Fimbria
Infundibulum
Ampulla
Isthmus
Intramural
segment
Fundus
Body
Cervix
UTERUS UTERINE TUBE (OVIDUCT)
34. THE PROCESS OF FERTILIZATION
1. Capacitation
2. Acrosome reaction
3. Penetration of the
oocyte coats
4. Zona reaction
34
Dr. Beda Olabu: Basic Embryology Series
35. FUNCTIONS OF ZONA PELLUCIDA
1. Prevents polyspermy
2. Ensures species specificity
3. Protects the oocyte
35
Dr. Beda Olabu: Basic Embryology Series
36. THE PROCESS OF FERTILIZATION
Only the head enters……….
5. Fusion of cell membranes
6.Completion of the oocyte
2nd meiotic division
7. Fusion of the male and the
female pronuclei
36
Dr. Beda Olabu: Basic Embryology Series
38. SUMMARY OF THE PROCESS OF FERTILIZATION
Process of fusion of the sperm
and the ovum
Occurs in the ampulla of the
Fallopian tube
Sperm penetrates the oocyte
coverings, then its nucleus fuses
with nucleus of the oocyte
The resultant new cell is called
the zygote
Dr. Beda Olabu: Basic Embryology Series
39. OUTCOME OF FERTILIZATION
1. Formation of the zygote from the ootid stage
2. Completion of oocyte 2nd meiotic division and
formation of the 2nd polar body
3. Restoration of the diploid (2n) number of chromosomes
4. Determination of embryonic sex (XX or XY genotype)
5. Genetic variation (variation of species)
6. Metabolic activation and restoration of capacity for
cell division (cleavage)
39
Dr. Beda Olabu: Basic Embryology Series
40. CLINICAL CORRELATION
1. Contraception
2. Assisted reproductive technology
3. Numerical chromosomal disorders
4. Polyspermy and molar pregnancy
40
Dr. Beda Olabu: Basic Embryology Series
44. 44
45X0: Tuner’s Syndrome 47XXX = Triple X Syndrome
NUMERICAL CHROMOSOMAL DISORDERS
Dr. Beda Olabu: Basic Embryology Series
45. 45
Trisomy 18: Edward’s Syndrome Trisomy 13: Patau Syndrome
NUMERICAL CHROMOSOMAL DISORDERS
Dr. Beda Olabu: Basic Embryology Series
46. MOLAR PREGNANCY
Occurs when there is an
“excess set” of paternal
chromosomes
Abnormal “vesicular”
proliferation of placental tissues
Also called hydatidiform mole
46
Dr. Beda Olabu: Basic Embryology Series
48. INRODUCTION
Hormonally regulated “monthly” cycles
✓Gonadotropic hormones (from pituitary)
✓Ovarian hormones
Involves changes in the endometrium as
well as the ovary
48
Dr. Beda Olabu: Basic Embryology Series
49. LEARNING OUTCOMES
1. State the effects of FSH & LH on the ovary
2. Name the phases of the ovarian cycle and state
their hormonal basis
3. Name the phases of the endometrial cycle and state
their hormonal basis of each
4. Understand the concept of safe days and its basis
49
Dr. Beda Olabu: Basic Embryology Series
57. INTRODUCTION
Pre-embryonic period of development:
1. The 1st 14 days (2 weeks) after conception
2. Formation & differentiation of embryonic and
trophoblastic (placental) tissues
3. Implantation and establishment of pregnancy
Dr. Beda Olabu: Basic Embryology Series
58. LEARNING OUTCOMES
1. Explain the events and morphological changes that
occur during the 1st week of development
2. Describe the process of implantation and state the
common disorders related to this
3. Outline the events that occur in the 2nd week of and
explain the concept of the “week of twos”
Dr. Beda Olabu: Basic Embryology Series
59. 1ST WEEK OF DEVELOPMENT
Occurs largely along
the Fallopian tube
Day 1 – 4/5: Within the
Fallopian tube
From day 5/6: In the
endometrial cavity
Dr. Beda Olabu: Basic Embryology Series
60. 1ST WEEK OF DEVELOPMENT
The conceptus:
1. Is propelled towards the
endometrial cavity
2. Undergoes cleavage &
morphological changes
Dr. Beda Olabu: Basic Embryology Series
61. 1ST WEEK OF DEVELOPMENT
Cleavage
ZYGOTE
STAGE
MORULA
STAGE
DAY 1 DAY 1-2 DAY 3-4
OOTID 12-32 CELLS
Compaction
2 CELLS
2-CELL
STAGE
Cleavage
62. 1ST WEEK OF DEVELOPMENT
BLASTOCYST
STAGE
MORULA
STAGE
DAY 3-4 DAY 5-6
Fluid accumulation
12-32 CELLS CAVITY PRESENT
Cleavage & Compaction
Cavity formation
63. 1ST WEEK OF DEVELOPMENT
LATE
BLASTOCYST
THE BLASTOCYST STAGE
EARLY
BLASTOCYST
DAY 5-6 DAY 6-8
Dr. Beda Olabu: Basic Embryology Series
Hatching Process
64. SUMMARY OF THE 1ST WEEK
1. Movement of the conceptus towards the endometrial
cavity (site of implantation)
2. Continuous cleavage & compaction, then hatching
3. Zygote → Two-cell stage → Morula → Blastocyst
4. Ends when the embryblastic and trophoblastic tissues
(inner and outer cell masses) have been established
Dr. Beda Olabu: Basic Embryology Series
65. PARTS OF THE BLASTOCYST
Individual cells of the blastocyst are termed blastomeres
66. 2ND WEEK OF DEVELOPMENT
1. Implantation of the blastocyst
2. Differentiation of the embryoblastic and the
trophoblastic tissues
3. Establishment of the foetal membranes
………………..The “week of twos”………………….
Dr. Beda Olabu: Basic Embryology Series
67. IMPLANTATION
The process by which the blastocyst attaches and
embeds itself into the endometrial lining of uterine wall
Invasion of the endometrium by the blastocyst is done
by the trophoblast layer; between day 6-13
Site of implantation determines site of placentation
Commonest site = Posterior aspect of uterine fundus
Dr. Beda Olabu: Basic Embryology Series
68. RELEVANT ANATOMY OF THE UTERUS
PARTS OF THE UTERUS LAYERS OF THE UTERINE WALL
LUMEN
PERIMETRIUM
MYOMETRIUM
ENDOMETRIUM
STRATUM BASALE
STRATUM
FUNCTIONALIS
70. IMPLANTATION PROCESS
Formation of the
syncitiotrophoblast layer
Burrowing & embedding,
guided by the trophoblast
Dr. Beda Olabu: Basic Embryology Series
73. ABNORMALITIES OF IMPLANTATION
Placenta previa:
Low lying placenta
Placenta detaches before
delivery of the baby
Risk of bleeding & still birth
Dr. Beda Olabu: Basic Embryology Series
78. THE CHORIONIC PLATE
COMPONENTS:
1. Extraembryonic
mesoderm
2. Cytotrophoblast
3. Syncitiotrophoblast
Dr. Beda Olabu: Basic Embryology Series
79. TWO PARTS OF THE CHORIONIC LAYER
Chorion frondosum & chorion laeve
Dr. Beda Olabu: Basic Embryology Series
80. “WEEK OF TWOS”
2 Cell masses
2 poles
2 Embryonic layers
2 Cavities
2 Trophoblastic layers
Dr. Beda Olabu: Basic Embryology Series
81. SUMMARY OF THE MORPHOLOGICAL STAGES OF THE
CONCEPTUS DURING THE 1ST TWO WEEKS
ZYGOTE
STAGE
MORULA
STAGE
BLASTOCYST
STAGE
BILAMINAR
DISC STAGE
2-CELL
STAGE
Dr. Beda Olabu: Basic Embryology Series
82. ABNORMALITIES OF THE 2ND WEEK
Blighted ovum (abembryonic pregnancy)
Dr. Beda Olabu: Basic Embryology Series
Dr. Beda Olabu: Basic Embryology Series
83. ABNORMALITIES OF THE 2ND WEEK
Hydatidiform mole (Molar pregnancy)
Dr. Beda Olabu: Basic Embryology Series
84. MOLAR PREGNANCY
Occurs when there is an
“excess set” of paternal
chromosomes
Abnormal “vesicular”
proliferation of placental
tissues
84
Dr. Beda Olabu: Basic Embryology Series
85. MULTIPLE GESTATION
FOCUS ON MECHANISMS and TYPES OF TWIN
PREGNANCIES
Dr. Beda Olabu:
Basic Embryology Lecture Series
86. MULTIPLE PREGNANCIES
oTwins, Triplets, Quadruplets, Quintuplets
Types of twin gestations:
1. Dizygotic
2. Monozygotic
Dr. Beda Olabu: Basic Embryology Series
87. DYZYGOTIC TWINNING
Two ova are ovulated, & subsequently fertilized by
different sperms
Hence development begin by two zygotes
The twins are genetically different (Fraternal)
Constitute the majority of twin gestations
Dr. Beda Olabu: Basic Embryology Series
89. MONOZYGOTIC TWINNING
An ovum is fertilized by one sperm and development
starts with 1 zygote, hence are termed monozygotic
Separation of the early embryonic cells then occurs
The splitting of embryonic cells is only possible up to
day15
Twins are classified based on the structures they share
Dr. Beda Olabu: Basic Embryology Series
90. STAGES OF EARLY DEVELOPMENT
ZYGOTE
STAGE
MORULA
STAGE
BLASTOCYST
STAGE
BILAMINAR
DISC STAGE
2-CELL
STAGE
Dr. Beda Olabu: Basic Embryology Series
96. CONJOINED (SIAMESE) TWINS
Separation at the primitive streak stage
(hence partial splitting of the cells of the
primitive streak)
The twins will share some body organs
All are monochorionic-monoamniotic types
Dr. Beda Olabu: Basic Embryology Series
102. COMPLICATIONS OF MULTIPLE GESTATION
6. Intrauterine demise of one twin
Fetus Papyraceus Vanishing twin
Dr. Beda Olabu: Basic Embryology Series
103. GASTRULATION
FOCUS ON THE TRILAMINAR EMBRYONIC DISC
Dr. Beda Olabu:
Basic Embryology Lecture Series
104. INTRODUCTION
The process of formation of a three layered
embryo (the gastrula or trilaminar germ disc)
The three embryonic layers are: ectoderm,
mesoderm & endoderm
Takes place during the 3rd week of development
Dr. Beda Olabu: Basic Embryology Series
105. INTRODUCTION
Events of the third week of development set stage for
the period of organogenesis
Occasionally referred to as the “week of threes”:
1. Three embryonic layers develop from the epiblast
2. Three embryonic structures are formed: The primitive
streak, notochord and neural tube
3. Three mesodermal segments develop – the paraxial,
intermediate and lateral plate mesoderm
Dr. Beda Olabu: Basic Embryology Series
106. LEARNING OUTCOMES
1. State the formation, functions and fate of the
primitive streak
2. The events during the process of gastrulation
3. Outline the adult derivatives of each of the
three germ layers
Dr. Beda Olabu: Basic Embryology Series
107. THE PRIMITIVE STREAK
Formed by proliferation of the midline epiblast cells
Around the caudal end of the bilaminar embryo
Dr. Beda Olabu: Basic Embryology Series
108. PARTS OF THE PRIMITIVE STREAK
Primitive groove
Primitive node
Primitive pit
Dr. Beda Olabu: Basic Embryology Series
109. FUNCTIONS OF THE PRIMITIVE STREAK
1. Provide structural support to the bilaminar
embryonic disc
2. Establishes the embryonic axis and bilateral
symmetry
3. Direct the process of gastrulation
Dr. Beda Olabu: Basic Embryology Series
110. FATE THE PRIMITIVE STREAK
The primitive streak degenerates (disappears)
What would happen if these
totipotent cells persist?
Sacrococcygeal teratoma
Contain multiple tissue lines
Dr. Beda Olabu: Basic Embryology Series
111. GASTRULATION
The process of formation
of the trilaminar disc
(gastrula)
The cells of primitive streak
migrate downwards and
outwards
The cellular migration
occurs in 2 phases:
Dr. Beda Olabu: Basic Embryology Series
112. GASTRULATION PROCESS
1st phase of migration:
Displace the hypoblast
layer of cells laterally
Becomes the endodermal
layer
Extends laterally to even
form the lining of the yolk
sac
Dr. Beda Olabu: Basic Embryology Series
113. GASTRULATION PROCESS
2nd phase of migration:
The cells sandwich themselves
between the formed endoderm
& the remaining epiblast cells
Become the mesodermal layer
This later divides into three
Dr. Beda Olabu: Basic Embryology Series
114. GASTRULATION PROCESS
Remaining epiblast constitute
the ectodermal layer
The structure is now called
gastrula (trilaminar germ disc)
All its layers arise from the
epiblast layer
Dr. Beda Olabu: Basic Embryology Series
116. DERIVATIVES OF THE GERM LAYERS
1. Ectoderm layer:
Protecting & communicating
layer
Differentiates into two parts:
1. Neuroectoderm: Nervous
system (both PNS & CNS)
2. Surface ectoderm: epidermis
of the skin
Dr. Beda Olabu: Basic Embryology Series
117. DERIVATIVES OF THE GERM LAYERS
2. Endoderm layer:
A nourishing layer
Becomes incorporated into
the embryo during folding
Constitutes the lining of the
primordial gut
Gives rise to epithelial lining &
glands of digestive &
respiratory systems
Dr. Beda Olabu: Basic Embryology Series
118. DERIVATIVES OF THE GERM LAYERS
Differentiation of the mesoderm layer:
Dr. Beda Olabu: Basic Embryology Series
119. DERIVATIVES OF THE GERM LAYERS
3. Mesoderm layer:
(a) Paraxial mesoderm
Undergoes segmentation to
form the somites
Somites differentiate into:
1. Sclerotome: Axial skeleton
2. Myotome: Skeletal muscles
3. Dermatome: Trunkal dermis
Dr. Beda Olabu: Basic Embryology Series
120. DERIVATIVES OF THE GERM LAYERS
3. Mesoderm layer:
(b) Intermediate mesoderm
Urinary system
Reproductive system
Dr. Beda Olabu: Basic Embryology Series
121. DERIVATIVES OF THE GERM LAYERS
3. Mesoderm layer:
(c) Somatic mesoderm
Appendicular skeleton
Dermis
Dr. Beda Olabu: Basic Embryology Series
122. DERIVATIVES OF THE GERM LAYERS
3. Mesoderm layer:
(d) Splanchnic mesoderm
Smooth musculature
Cardiac musculature
Visceral C.T
Dr. Beda Olabu: Basic Embryology Series
123. THE GERM LAYERS & THEIR DERIVATIVES
Dr. Beda Olabu: Basic Embryology Series
125. NEURULATION
FOCUS ON FORMATION OF THE NEURAL
TUBE & NEURAL TUBE DEFECTS
Dr. Beda Olabu:
Basic Embryology Lecture Series
126. INTRODUCTION
Neurulation is the process of formation of the neural
tube
The neural tube is the primordium of the central
nervous system – brain and spinal cord
Occurs during the 3rd to 4th week of development
There is primary and secondary neurulation processes
Dr. Beda Olabu: Basic Embryology Series
127. LEARNING OUTCOMES
1. State the formation, functions and fate of
notochord
2. Describe the process of primary and secondary
3. Highlight on the common neural tube defects
4. Outline the derivatives of the neural crest cells
Dr. Beda Olabu: Basic Embryology Series
129. FUNCTIONS OF THE NOTOCHORD
1. Provide structural support
2. Define the embryonic axis
3. Induce neurulation
4. Basis for axial skeleton
Dr. Beda Olabu: Basic Embryology Series
130. FATE OF THE NOTOCHORD
Degenerates
Form the nucleus
pulposus of the
intervertebral discs
If it fails to degenerate?
Dr. Beda Olabu: Basic Embryology Series
132. NEURULATION
Process of formation of
the neural tube
Primordium of CNS
Leads to formation of
neural tube & neural crest
Primary & secondary…..
Dr. Beda Olabu: Basic Embryology Series
133. NEURULATION
Process of formation of
the neural tube
Primordium of CNS
Leads to formation of
neural tube & neural crest
Primary & secondary…..
Dr. Beda Olabu: Basic Embryology Series
138. OVERVIEW OF NEURULATION PROCESS
Induction by the notochord
Form the neuroectoderm &
surface ectoderm
Thickening (= neural plate)
Neural groove & neural folds
Fusion to form the neural tube
(and neural crest)
Dr. Beda Olabu: Basic Embryology Series
139. OVERVIEW OF NEURULATION PROCESS
Induction by the notochord
Form the neuroectoderm &
surface ectoderm
Thickening (= neural plate)
Neural groove & neural folds
Fusion to form the neural tube
(and neural crest)
Dr. Beda Olabu: Basic Embryology Series
143. NEURAL CREST DERIVATIVES
In the peripheral nervous
system
In the integument system
In the endocrine system
In the heart
In the craniofacial region
Dr. Beda Olabu: Basic Embryology Series
144. ANOMALIES ASSOCIATED WITH NEURAL
CREST CELLS
1. Congenital aganglionic megacolon
2. Disorders of skin pigmentation
3. 1st pharyngeal arch syndromes
4. Cardiac malformations
Dr. Beda Olabu: Basic Embryology Series
148. LEARNING OUTCOMES
For each foetal membrane, state:
1. When and how the membrane is formed
2. The roles/functions of the foetal membrane
3. The eventual fate of the foetal membrane
4. Clinical aspects regarding the foetal membrane
Dr. Beda Olabu: Basic Embryology Series
149. THE AMNION
Forms in the ICM during the 2nd
week of development
By migration of the amnioblast
cells from the epiblast layer
Secrete (amniotic) fluid into
the amniotic cavity
Dr. Beda Olabu: Basic Embryology Series
150. THE AMNIOTIC SAC
The size increases as the pregnancy advances
Dr. Beda Olabu: Basic Embryology Series
151. SOURCES OF AMNIOTIC FLUID
EARLY SOURCES:
Secretions of amnioblast
cells
Maternal tissue fluid (by
diffusion)
LATER SOURCES:
Fetal urine
Foetal secretions: from
foetal skin, lungs and GIT
Dr. Beda Olabu: Basic Embryology Series
153. FUNCTIONS OF THE AMNIOTIC FLUID
Protective/shock
absorption
Lubricates the fetal skin
to prevent drying
Musculoskeletal
development
Permit symmetrical growth
of the foetus
Thermoregulation
Lubricate the birth canal
Promote expansion of the
lung alveoli
Dr. Beda Olabu: Basic Embryology Series
154. FATE OF THE AMNION
Tears around the time of delivery during
“rupture of membranes”
The membrane is expelled “after birth”
together with the placenta
Dr. Beda Olabu: Basic Embryology Series
157. OLIGOHYDRAMNIOS
Amniotic fluid volume is
less than expected for the
gestational age
Often less than 500mL
List possible causes of
oligohydramnios
Dr. Beda Olabu: Basic Embryology Series
158. CAUSES OF OLIGOHYDRAMNIOS (DRIPPC)
Demise/Drugs
Renal abnormalities (hence reduced urine output):
agenesis, dysplasia, cystic kidney diseases, PUVs,
urethral atresia
Intra-uterine growth restriction (IUGR)
Premature rupture of membranes (PROM & PPROM)
Placental insufficiency
Chromosomal anomalies: Trisomy 13; Trisomy 18
Dr. Beda Olabu: Basic Embryology Series
160. POLYHYDRAMNIOS
Amniotic fluid volume is
more than expected for
the gestational age
Generally AFI >25 cm
List possible causes of
polyhydramnios
Dr. Beda Olabu: Basic Embryology Series
161. CAUSES OF POLYHYDRAMNIOS
Categories:
More than 50% is
idiopathic
Maternal causes: DM,
CCF
Multiple foetal causes:
Common foetal causes:
CNS anomalies
Anomalies that lead to
gastrointestinal obstruction
Multiple pregnancy
Cardiac anomalies
Trisomy 21(or 18 and 13)
Dr. Beda Olabu: Basic Embryology Series
163. AMNIOTIC BAND SYNDROME
Comprises a wide spectrum
of abnormalities
Result from entrapment of
various fetal body parts in a
disrupted amnion
Multiple defects can occur
Dr. Beda Olabu: Basic Embryology Series
166. YOLK SAC (UMBILICAL VESICLE)
Formed in the 2nd week of
development
By migrating cells from the
hypoblast layer
Later by endodermal cells
Dr. Beda Olabu: Basic Embryology Series
167. FUNCTIONS OF THE YOLK SAC
Early nutrient supply
Site of early hemopoiesis
Gives rise to the PGCs
(primordial germ cells)
Dr. Beda Olabu: Basic Embryology Series
168. OVERVIEW OF EMBRYONIC FOLDING
The embryo folds both longitudinally (cranio-caudal axis)
and laterally (transverse axis)
As the embryo folds, the dorsal part of the yolk sac is
longitudinally incorporated into the developing baby
Discuss with your neighbor the key outcomes of each of
the embryonic folding processes
Dr. Beda Olabu: Basic Embryology Series
169. OUTCOME OF EMBRYONIC FOLDING
Transverse embryonic folding:
Dr. Beda Olabu: Basic Embryology Series
170. OUTCOME OF EMBRYONIC FOLDING
Cranio-caudal embryonic folding:
Dr. Beda Olabu: Basic Embryology Series
171. THE FATE OF THE YOLK SAC
Dr. Beda Olabu: Basic Embryology Series
172. FATE OF THE YOLK SAC
Dorsal part is incorporated
into the embryo during
folding (to become the
primordial gut)
Ventral part degenerates
Dr. Beda Olabu: Basic Embryology Series
173. FATE OF THE VITELLINE DUCT
Dr. Beda Olabu: Basic Embryology Series
174. YOLK SAC: CLINICAL CORRELATES
Vitelline duct anomalies
Meckel’s diverticulum Vitelline fistula Vitelline cyst Fibrous cord
Dr. Beda Olabu: Basic Embryology Series
175. THE ALLANTOIS
An extension of the yolk sac,
into the connecting stalk
Similar functions as yolk sac*
Contribute to formation of
the umbilical vessels
Dr. Beda Olabu: Basic Embryology Series
176. FATE OF THE ALLANTOIS
Lower part incorporated to
form the urinary bladder
Upper part degenerates as
the urachus
Becomes the median
umbilical ligament
Dr. Beda Olabu: Basic Embryology Series
177. CLINICAL CORRELATIONS
Persistence of the
allantois lead to
Urachal anomalies
Commoner types are:
Urachal fistulas
Urachal cysts
Dr. Beda Olabu: Basic Embryology Series
178. THE CHORIONIC PLATE
COMPONENTS:
1. Extraembryonic
mesoderm (somatic L)
2. Cytotrophoblast
3. Syncitiotrophoblast
Dr. Beda Olabu: Basic Embryology Series
179. TWO PARTS OF THE CHORION
Chorion frondosum & chorion laeve
Dr. Beda Olabu: Basic Embryology Series
180. FUNCTIONS OF THE CHORION
Chorion frondosum forms the
foetal component of the
placenta
Chorion protects the embryo
Haemopoietic centre
Dr. Beda Olabu: Basic Embryology Series
181. CLINICAL UTILITY OF THE CHORION
For diagnosis of early
pregnancy:
1. Laboratory detection of
beta hCG (from urine or
blood samples)
2. Sonographic visualization
of the gestational sac
(chorionic cavity)
Dr. Beda Olabu: Basic Embryology Series
182. CLINICAL UTILITY OF THE CHORION
For diagnosis of an
early pregnancy:
1. Laboratory detection of
beta hCG (from urine or
blood samples)
2. Sonographic visualization
of the gestational sac
(chorionic cavity)
Dr. Beda Olabu: Basic Embryology Series
183. CLINICAL UTILITY OF THE CHORION
Chorionic villous sampling:
Dr. Beda Olabu: Basic Embryology Series
185. FUNCTIONS OF THE PLACENTA
Exchange – Oxygen, carbon dioxide, nutrients,
antibodies
Endocrine – hCG, estrogen, progesterone, hPL
Metabolic – Glycogen
Dr. Beda Olabu: Basic Embryology Series
186. STRUCTURAL ANOMALIES OF THE PLACENTA
Excess penetration/invasion into the uterine wall:
Dr. Beda Olabu: Basic Embryology Series
187. STRUCTURAL ANOMALIES OF THE PLACENTA
Placenta
Previa
Battledore
Placenta
Bi-lobed
Placenta
Dr. Beda Olabu: Basic Embryology Series
188. STRUCTURAL ANOMALIES OF THE PLACENTA
Circumvallate
Placenta
Placenta
Velamentosa
Placenta
Succenturiata
Dr. Beda Olabu: Basic Embryology Series
189. FOETAL PERIOD OF DEVELOPMENT
FOCUS ON THE 9TH WEEK UNTIL BIRTH
Dr. Beda Olabu:
Basic Embryology Lecture Series
190. INTRODUCTION
Prenatal developmental periods:
Before conception:
Gametogenesis
Fertilization
After conception:
Pre-embryonic period
Embryonic period
Foetal period
Dr. Beda Olabu: Basic Embryology Series
191. 1. Main characteristics of the foetal period
2. Methods of assessing foetal growth
3. Prenatal diagnosis of birth defects
4. Key features in various foetal periods
5. Factors which influence foetal growth
LEARNING OUTCOMES
Dr. Beda Olabu: Basic Embryology Series
192. 1. Rapid growth of the body organs
✓ 1st trimester – hyperplasia
✓ 2nd trimester – hyperplasia & hypertrophy
✓ 3rd trimester – hypertrophy
2. Marked increase in height and weight
✓ In the 3rd trimester, weight triples and length doubles
as body stores of protein, fat, iron and calcium increase
CHARACTERISTICS OF THE FOETAL PERIOD
Dr. Beda Olabu: Basic Embryology Series
193. 3. Ossification
4. Fat deposition
CHARACTERISTICS OF THE FOETAL PERIOD
Dr. Beda Olabu: Basic Embryology Series
194. 5. Reduced head dominance (compared to the rest
of the body)
CHARACTERISTICS OF THE FOETAL PERIOD
Dr. Beda Olabu: Basic Embryology Series
195. Ossification centers for long bones and cranium appear
Head is ½ of the crown heel length
Face is recognizably human
Hepatosplenic phase of hemopoiesis
Intestines return to the abdomen
Urine formation
Gender of the external genital becomes distinguishable
WEEK 9 – 12 OF DEVELOPMENT
Dr. Beda Olabu: Basic Embryology Series
196. Rapid growth occurs
Ossification is active
Head becomes relatively small compared to the 12th
week fetus: longer limbs
Face changes: eyes are anterolateral, ears almost in
place
14 weeks:
Limb movements are coordinated
Slow eye movements
WEEK 13 – 16 OF DEVELOPMENT
Dr. Beda Olabu: Basic Embryology Series
197. Rapid growth occurs
Ossification is active
Head becomes relatively small
compared to the 12th week fetus: longer
limbs
Face changes: eyes are anterolateral,
ears almost in place
Limb movements are coordinated
Slow eye movements
WEEK 13 – 16 OF DEVELOPMENT
Dr. Beda Olabu: Basic Embryology Series
198. Growth slows
Fetal movements can be felt by
mother
Skin covered by vernix caseosa
Uterus formed, vagina canalized
Eye brows and head hair visible
Fetal skin covered by lanugo
Brown fat is formed (site of heat
production)
Descent of the testes
WEEK 17 – 20 OF DEVELOPMENT
Dr. Beda Olabu: Basic Embryology Series
199. Weight gain occurs
Wrinkled skin, translucent
Skin is pink
Rapid eye movements; Blink startle 21-23 weeks
Finger-nails present
Type II pneumocytes start to secrete surfactant
WEEK 21 – 25 OF DEVELOPMENT
Dr. Beda Olabu: Basic Embryology Series
200. Lungs and pulmonary vasculature adequately formed
CNS can regulate body temperature and breathing
Eyelids open at 26 weeks
Toe nails are visible
Subcutaneous fat present (3.5% of body weight), making
skin smooth
Bone marrow takes over hematopoiesis at 28 weeks
WEEK 26 – 29 OF DEVELOPMENT
Dr. Beda Olabu: Basic Embryology Series
201. Pupillary light reflex can be elicited
Upper and lower limbs now have a chubby
appearance
Fat is now 8% of body weight
WEEK 30 – 34 OF DEVELOPMENT
Dr. Beda Olabu: Basic Embryology Series
202. Firm grasp by fetus
Spontaneous orientation to light
Fat is about 16% of the body weight (fat increases
at 14g per day)
At 36 weeks abdominal circumference same as
head circumference
Breasts protrude in both males and females
WEEK 35 – 36 OF DEVELOPMENT
Dr. Beda Olabu: Basic Embryology Series
204. Genetic factors: Race; Chromosomal disorders
Hormonal factors: Fetal thyroid hormone
Environmental factors: uterine environment,
maternal systemic disease, Smoking)
FACTORS THAT INFLUENCE FOETAL GROWTH
Dr. Beda Olabu: Basic Embryology Series
205. Infectious agents (TORCH-S)
Diet and nutrients
Social and emotional stress
Drug and smoking
Teratogens and toxins
Altitude and temperature
Ionizing radiation
FACTORS THAT INFLUENCE FOETAL GROWTH
Dr. Beda Olabu: Basic Embryology Series
206. Fundal height:
Estimates the size of
the uterus
ASSESSMENT OF FOETAL GROWTH
Dr. Beda Olabu: Basic Embryology Series
220. Teratology:
Study of birth defects
Teratogen:
An agent that causes congenital defects
Congenital anomaly:
A structural defect that someone is born with
DEFINITIONS OF TERMS
Dr. Beda Olabu: Basic Embryology Series
221. Malformation: A primary structural defect resulting
from a localized error of morphogenesis (intrinsic)
Disruption: Specific abnormality that results from
disruption of normal developmental processes.
Deformation: An alteration in shape / structure of
previously normally formed part (extrinsic)
Syndrome: A recognized pattern of malformations with
a given etiology
DEFINITIONS OF TERMS
Dr. Beda Olabu: Basic Embryology Series
222. 1. General principles of teratology
2. Common mechanisms of birth defects
3. Common morphological defects
4. Causes of birth defects
5. Prenatal diagnosis of birth defects
LEARNING OUTCOMES
Dr. Beda Olabu: Basic Embryology Series
223. 2-3% of live newborns have birth defects
Wide spectrum
Multiple defects can occur – syndromes
Shows geographical and ethnic differences
GENERAL PRINCIPLES OF CONGENITAL
ANOMALIES
Dr. Beda Olabu: Basic Embryology Series
224. Failed induction to form an organ
Persistence of an embryonic structure
Inadequate/failed cellular migration
Excessive migration of cells/tissues
Developmental arrest
COMMON MECHANISMS OF CONGENITAL
ANOMALIES
Dr. Beda Olabu: Basic Embryology Series
225. Incomplete/partial separation
Defective septation of an organ/embryonic structure
Failed/inadequate/excess tissue resorption
Failure to fuse/merge
Abnormal union/merging
COMMON MECHANISMS OF CONGENITAL
ANOMALIES
Dr. Beda Olabu: Basic Embryology Series
243. 1. Death – abortion or miscarriage
2. Malformation
3. IUGR – intrauterine growth retardation
4. Functional defects in the newborn
5. Normal newborn
CONSEQUENCES OF EXPOSURE TO A TERATOGEN
Dr. Beda Olabu: Basic Embryology Series