ºÝºÝߣ

ºÝºÝߣShare a Scribd company logo

L.9.L10.L11 EMBRYOLOGY 1. Intruduction.pdf

•
•
J
JuliusKauki1

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.

1 of 28
Download to read offline
KILIMANJARO CHRISTIAN MMEDICAL UNIVERSITY COLLEGE Faculty of Nursing and Rehabilitation Medicine Department of Anatomy and Neuroscience EMBRYOLOGY DISCUSSION LECTURE (L9,10,11) INTRODUCTION TO EMBRYOLOGY Date: November 25th 2022, from 8:00 am, GF 01 MD1 Classroom. Lecturer: J. S. Kauki, BSc, MSc, on PhD, Email: jskauki@gmail.com. Office ext. 69 IPH Block, 3RD Floor, Anatomy dept.
General Course Objectives • An understanding of human embryology provides a rational basis for comprehending gross anatomy and the variations and/or abnormalities that a physician encountered in the physical examination, radiology, surgery or other invasive and non-invasive diagnostic procedures. • An understanding of development is of great value in understanding congenital malformations, whether these be inherited or acquired in utero. Surgical approaches for treating these malformations require an understanding of embryology. • An understanding of embryonic and fetal development is obviously essential for anyone entering the field of Health sciences • Future therapeutics employing genetic or molecular medicine may necessitate in utero approaches.
Cleft lip and palate Amelia We need to know the cause and management of these and many other conditions that occurs during development
Discussion • What causes Congenital anomalies / Birth defects?
L.9.L10.L11 EMBRYOLOGY 1. Intruduction.pdf
Recent History • 1965 - Neural Crest Research Nicole Le Douarin. • 1977 - Thalidomide and its affects on development. Thalidomide • 1978 - First IVF baby born. In Vitro Fertilization • 1986 Discoveries of growth factors • 1995 Genetic control of early embryonic development • 1996 - "Dolly the sheep" First adult somatic cell cloning using the process of nuclear transfer. • 2002 Cell cycle • 2002 Cell death • 2007 Embryonic stem cells • 2010 Development of in vitro fertilization (More? Assisted Reproductive Technology) • 2000 - Human Genome Complete Human Genome • 2001 Talk given by Robert Winston "Engineering Reproduction: Will We Still Be Human At The End of the 21st Century". • 2009 - Induced pluripotent stem (iPS) Stem Cells • 2011 - First Successful Transplantation of a Synthetic Tissue Engineered Windpipe Karolinska Institute | University College London Louise Brown, the first IVF baby as an adult.
In Vitro Fertilization (IVF)
The ten most frequently reported birth defects in USA between 2003-2004 1. Hypospadias 2. Obstructive Defects of the Renal Pelvis or Obstructive Genitourinary Defects 3. Ventricular Septal Defect 4. Congenital Dislocated Hip 5. Trisomy 21 or Down syndrome 6. Hydrocephalus 7. Cleft Palate 8. Trisomy 18 or Edward Syndrome 9. Renal Agenesis/Dysgenesis 10. Cleft Lip and Palate - occur with another defect in 33.7% of cases. (Cases for TZ and Ethiopia)
Patterns of Congenital anomalies compared RANKS Major Congenital anomaly USA EthiopiaTanzania Genital urinary 1 6 8 Cardiovascular 2 5 6 Musculoskeletal 3 3 2 Neural tube defects 4 1 1 Ear, Nose, Head and Neck 5 7 4 Orofacial defects 6 2 - Syndrome defects (Down, Patau) 7 4 7 Gastrointestinal - - 3 Multiple congenital anomalies - - 5 Others 8 8 9 0 1 2 3 4 5 6 7 8 9 10 GU CVS MSS NT E,N,H&N OFD SD GIT MCA O Patterns of Congenital anomalies compared between countries USA Ethiopia Tanzania Between 3% to 4% of all live born children will be diagnosed with significant birth defects within their first two years
Causes congenital anomalies / Birth defects? • Approximately 50% of congenital anomalies cannot be linked to a specific cause. • However, known causes include single gene defects, chromosomal disorders, multifactorial inheritance, environmental teratogens and micronutrient deficiencies. • Genetic causes can be traced to inherited genes or from mutations.
L.9.L10.L11 EMBRYOLOGY 1. Intruduction.pdf
Common terms encountered Oocyte = female germ cell produced in the ovary Sperm (spermatozoon) = male germ cell Zygote = cell resulting from union of sperm and ovum Cleavage = series of mitotic divisions of the zygote forming early embryonic cells (blastomeres) Blastomeres = individual cells of the cleavage stage embryo. Morula = round cluster of ~16 blastomeres (from Latin meaning mulberry). Compaction = process during which tight and gap junctions form between blastomeres evidenced by a smoothing of the morula surface. Blastocyst = ~58 cell stage at which fluid accumulation occurs within the embryo forming the blastocoel cavity. Trophoblast = the cell layer that gives rise only to extraembryonic tissue. Inner cell mass = tissue in blastula that gives rise to the embryo proper and some extraembryonic tissues. Zona pellucida = glycoprotein rich layer surrounding ovum, zygote, morula and blastula which is shed just prior to implantation (around day 6 of development). Implantation = penetration of the uterine wall by the embryo at ~days 6-8.
Developmental periods • Human development is a continuous process that begins with a fertilization of an ovum by a sperm in the female reproductive system. • The resulting zygote (conceptus) is transformed into a human being through cell division, cell migration, programmed cell death (Apoptosis), differentiation, growth and cell rearrangement. • Embryonic period: First eight weeks of development. • Period in which all major organ systems form but only the cardiovascular system truly functions and is essential for subsequent development. • Period of greatest susceptibility to teratogens. • Teratogen is any agent that can disturb development of an embryo/ fetus thus causing a birth defect in the child or halt the pregnancy outright. • Fetal period: Ninth week through birth. • Period in which the major tissues and organ systems complete differentiation, enlarge & begin functioning.
Risk of Birth defects on teratogen exposure
Internal female reproductive structure
Gametogenesis • A process of formation and development of gametes (sperm and ovum) • This process involves meiotic cell division which reduces the number of chromosomes to half and alters the shape of cells • Gametogenesis prepares sex cells for fertilization
Spermatogenesis • Process by which spermatozoa are produced from male primordial germ cells • Begins at puberty (13-16yrs); continues into old age • Begins with transformation of primitive germ cells called spermatogonia in the seminiferous tubules • Spermatogonia transform into primary spermatocyte after several mitotic divisions • Each primary spermatocyte undergoes 1st meiotic division to form 2 haploid secondary spermatocytes • Secondary spermatoctyes undergoes 2nd meiotic division to form 4 haploid spermatids • Spermatids are transformed to mature sperms during spermiogenesis
Spermiogenesis • Transformation of spermatids into mature sperms • Involves • Loss of cytoplasm • Development of a tail • Formation of acrosome • Spermatogenesis (including spermiogenesis) takes about two months! • Produced sperms are viable for 48hrs • When spermiogenesis is complete, sperms enter into the lumen of the seminiferous tubules then transported into epididymis for storage • Sertoli cells lining the seminiferous tubules Support and nurture the germ cells Mature Sperm
L.9.L10.L11 EMBRYOLOGY 1. Intruduction.pdf
Maturation of sperms • Ejaculated sperm must undergo Capacitation & Acrosome reaction to be able to fertilize the ovum • During capacitation • Capacitation takes place in uterus or uterine tubes by substances secreted by these parts of female genital tract • Glycoprotein coat & seminal proteins are removed from surface of sperm’s acrosome • Sperms becomes more active • Acrosome reaction • During acrosome reaction, perforations occur in the acrosome • Angiotensin converting enzyme in the acrosome involved in acrosome reaction • Completed before sperm fuse with oocyte
Oogenesis • Sequence of events by which primitive germ cells called oogonia in the ovary are transformation into mature oocytes • Begins before birth • Completed after puberty is reached • The process ultimately produces one mature ovum every month viable for 24hrs • Prenatal maturation of oocytes • Oogonia ploriferates by mitosis to form primary oocytes before birth • Connective tissue cells forms follicular cells that surrounds primary oocyte • Primary oocytes surrounded by follicular cells is called primary follicle
• Each primary oocytes is surrounded by zona pelucida • All primary oocytes begin 1st meiotic div before birth but completion of prophase of 1st meiotic division doesn't occur until adolescence • All primary oocytes remain dormant in suspended prophase stage of 1st meiotic div in ovarian follicles until sexual maturity and the menstrual cycles begin during puberty Postnatal maturation of oocytes • Beginning during puberty, usually one follicle matures each month and ovulation occurs • Primary oocyte completes the 1st meiotic div shortly before ovulation to form one secondary oocyte and first polar body (which degenerates) • Secondary oocyte begins 2nd meiotic div. at ovulation but progresses only to metaphase of 2nd meiotic div. when division is arrested • If the sperm penetrates the secondary oocyte, the 2nd meiotic division is completed Oogenesis Cont… Prenatal • 1st meiotic div starts during early fetal life • 1st Meiotic div arrested at prophase stage • Oocyte maturation inhibitor produced by follicular cells Postnatal • At puberty i.e. Just before ovulation, primary oocyte completes 1st meiotic Div • Starts 2nd meiotic div at ovulation but is arrested at Metaphase • 2nd meiotic div completed after sperm penetration
Follicle Maturation and Ovulation Oocytes ~2 million at birth ~40,000 at puberty ~400 ovulated over lifetime Leutinizing Hormone surge (from pituitary gland) causes changes in tissues and within follicle: • Swelling within follicle due to increased hyaluronan • Matrix metalloproteinases degrade surrounding tissue causing rupture of follicle Egg and surrounding cells (corona radiata) ejected into peritoneum Corona radiata provides bulk to facilitate capture of egg.
• Note: • Long duration of the first meiotic division (up to 45 yrs) may account for meiotic errors e.g. Nondisjunction (failure of chromatids to dissociate) that occur with increasing maternal age • Primary oocytes in suspended prophase are vulnerable to environmental teratoges such as radiations • There are about 2 million primary oocytes in ovaries of newborn female infant • Many regresses and only about 400 become secondary oocytes and are expelled at ovulation during reproductive period
Human Ovary
Abnormal gametogenesis/gametes • Ideal maternal age for reproduction is 18-35 yrs of age • Risk of chromosomal abnormalities increases after age 35 yrs • Nondisjunction e.g. Down syndrome • Other form of trisomy • Gene mutation increases with age
Textbooks • Either of the textbooks listed below are recommended for the course 1. Keith L. Moore, T.V.N. Persaud, Mark G. Torchia. (2011). The Developing Human: clinically oriented embryology (9th ed.). Philadelphia: Saunders. Publisher: Philadelphia, PA : Saunders/Elsevier, ISBN: 9781437720020 2. Schoenwolf, G.C., Bleyl, S.B., Brauer, P.R. and Francis-West, P.H. (2009). Larsen’s Human Embryology (4th ed.). New York; Edinburgh: Churchill Livingstone.
THANK YOU

More Related Content

L.9.L10.L11 EMBRYOLOGY 1. Intruduction.pdf

  • 1. KILIMANJARO CHRISTIAN MMEDICAL UNIVERSITY COLLEGE Faculty of Nursing and Rehabilitation Medicine Department of Anatomy and Neuroscience EMBRYOLOGY DISCUSSION LECTURE (L9,10,11) INTRODUCTION TO EMBRYOLOGY Date: November 25th 2022, from 8:00 am, GF 01 MD1 Classroom. Lecturer: J. S. Kauki, BSc, MSc, on PhD, Email: jskauki@gmail.com. Office ext. 69 IPH Block, 3RD Floor, Anatomy dept.
  • 2. General Course Objectives • An understanding of human embryology provides a rational basis for comprehending gross anatomy and the variations and/or abnormalities that a physician encountered in the physical examination, radiology, surgery or other invasive and non-invasive diagnostic procedures. • An understanding of development is of great value in understanding congenital malformations, whether these be inherited or acquired in utero. Surgical approaches for treating these malformations require an understanding of embryology. • An understanding of embryonic and fetal development is obviously essential for anyone entering the field of Health sciences • Future therapeutics employing genetic or molecular medicine may necessitate in utero approaches.
  • 3. Cleft lip and palate Amelia We need to know the cause and management of these and many other conditions that occurs during development
  • 4. Discussion • What causes Congenital anomalies / Birth defects?
  • 6. Recent History • 1965 - Neural Crest Research Nicole Le Douarin. • 1977 - Thalidomide and its affects on development. Thalidomide • 1978 - First IVF baby born. In Vitro Fertilization • 1986 Discoveries of growth factors • 1995 Genetic control of early embryonic development • 1996 - "Dolly the sheep" First adult somatic cell cloning using the process of nuclear transfer. • 2002 Cell cycle • 2002 Cell death • 2007 Embryonic stem cells • 2010 Development of in vitro fertilization (More? Assisted Reproductive Technology) • 2000 - Human Genome Complete Human Genome • 2001 Talk given by Robert Winston "Engineering Reproduction: Will We Still Be Human At The End of the 21st Century". • 2009 - Induced pluripotent stem (iPS) Stem Cells • 2011 - First Successful Transplantation of a Synthetic Tissue Engineered Windpipe Karolinska Institute | University College London Louise Brown, the first IVF baby as an adult.
  • 8. The ten most frequently reported birth defects in USA between 2003-2004 1. Hypospadias 2. Obstructive Defects of the Renal Pelvis or Obstructive Genitourinary Defects 3. Ventricular Septal Defect 4. Congenital Dislocated Hip 5. Trisomy 21 or Down syndrome 6. Hydrocephalus 7. Cleft Palate 8. Trisomy 18 or Edward Syndrome 9. Renal Agenesis/Dysgenesis 10. Cleft Lip and Palate - occur with another defect in 33.7% of cases. (Cases for TZ and Ethiopia)
  • 9. Patterns of Congenital anomalies compared RANKS Major Congenital anomaly USA EthiopiaTanzania Genital urinary 1 6 8 Cardiovascular 2 5 6 Musculoskeletal 3 3 2 Neural tube defects 4 1 1 Ear, Nose, Head and Neck 5 7 4 Orofacial defects 6 2 - Syndrome defects (Down, Patau) 7 4 7 Gastrointestinal - - 3 Multiple congenital anomalies - - 5 Others 8 8 9 0 1 2 3 4 5 6 7 8 9 10 GU CVS MSS NT E,N,H&N OFD SD GIT MCA O Patterns of Congenital anomalies compared between countries USA Ethiopia Tanzania Between 3% to 4% of all live born children will be diagnosed with significant birth defects within their first two years
  • 10. Causes congenital anomalies / Birth defects? • Approximately 50% of congenital anomalies cannot be linked to a specific cause. • However, known causes include single gene defects, chromosomal disorders, multifactorial inheritance, environmental teratogens and micronutrient deficiencies. • Genetic causes can be traced to inherited genes or from mutations.
  • 12. Common terms encountered Oocyte = female germ cell produced in the ovary Sperm (spermatozoon) = male germ cell Zygote = cell resulting from union of sperm and ovum Cleavage = series of mitotic divisions of the zygote forming early embryonic cells (blastomeres) Blastomeres = individual cells of the cleavage stage embryo. Morula = round cluster of ~16 blastomeres (from Latin meaning mulberry). Compaction = process during which tight and gap junctions form between blastomeres evidenced by a smoothing of the morula surface. Blastocyst = ~58 cell stage at which fluid accumulation occurs within the embryo forming the blastocoel cavity. Trophoblast = the cell layer that gives rise only to extraembryonic tissue. Inner cell mass = tissue in blastula that gives rise to the embryo proper and some extraembryonic tissues. Zona pellucida = glycoprotein rich layer surrounding ovum, zygote, morula and blastula which is shed just prior to implantation (around day 6 of development). Implantation = penetration of the uterine wall by the embryo at ~days 6-8.
  • 13. Developmental periods • Human development is a continuous process that begins with a fertilization of an ovum by a sperm in the female reproductive system. • The resulting zygote (conceptus) is transformed into a human being through cell division, cell migration, programmed cell death (Apoptosis), differentiation, growth and cell rearrangement. • Embryonic period: First eight weeks of development. • Period in which all major organ systems form but only the cardiovascular system truly functions and is essential for subsequent development. • Period of greatest susceptibility to teratogens. • Teratogen is any agent that can disturb development of an embryo/ fetus thus causing a birth defect in the child or halt the pregnancy outright. • Fetal period: Ninth week through birth. • Period in which the major tissues and organ systems complete differentiation, enlarge & begin functioning.
  • 14. Risk of Birth defects on teratogen exposure
  • 16. Gametogenesis • A process of formation and development of gametes (sperm and ovum) • This process involves meiotic cell division which reduces the number of chromosomes to half and alters the shape of cells • Gametogenesis prepares sex cells for fertilization
  • 17. Spermatogenesis • Process by which spermatozoa are produced from male primordial germ cells • Begins at puberty (13-16yrs); continues into old age • Begins with transformation of primitive germ cells called spermatogonia in the seminiferous tubules • Spermatogonia transform into primary spermatocyte after several mitotic divisions • Each primary spermatocyte undergoes 1st meiotic division to form 2 haploid secondary spermatocytes • Secondary spermatoctyes undergoes 2nd meiotic division to form 4 haploid spermatids • Spermatids are transformed to mature sperms during spermiogenesis
  • 18. Spermiogenesis • Transformation of spermatids into mature sperms • Involves • Loss of cytoplasm • Development of a tail • Formation of acrosome • Spermatogenesis (including spermiogenesis) takes about two months! • Produced sperms are viable for 48hrs • When spermiogenesis is complete, sperms enter into the lumen of the seminiferous tubules then transported into epididymis for storage • Sertoli cells lining the seminiferous tubules Support and nurture the germ cells Mature Sperm
  • 20. Maturation of sperms • Ejaculated sperm must undergo Capacitation & Acrosome reaction to be able to fertilize the ovum • During capacitation • Capacitation takes place in uterus or uterine tubes by substances secreted by these parts of female genital tract • Glycoprotein coat & seminal proteins are removed from surface of sperm’s acrosome • Sperms becomes more active • Acrosome reaction • During acrosome reaction, perforations occur in the acrosome • Angiotensin converting enzyme in the acrosome involved in acrosome reaction • Completed before sperm fuse with oocyte
  • 21. Oogenesis • Sequence of events by which primitive germ cells called oogonia in the ovary are transformation into mature oocytes • Begins before birth • Completed after puberty is reached • The process ultimately produces one mature ovum every month viable for 24hrs • Prenatal maturation of oocytes • Oogonia ploriferates by mitosis to form primary oocytes before birth • Connective tissue cells forms follicular cells that surrounds primary oocyte • Primary oocytes surrounded by follicular cells is called primary follicle
  • 22. • Each primary oocytes is surrounded by zona pelucida • All primary oocytes begin 1st meiotic div before birth but completion of prophase of 1st meiotic division doesn't occur until adolescence • All primary oocytes remain dormant in suspended prophase stage of 1st meiotic div in ovarian follicles until sexual maturity and the menstrual cycles begin during puberty Postnatal maturation of oocytes • Beginning during puberty, usually one follicle matures each month and ovulation occurs • Primary oocyte completes the 1st meiotic div shortly before ovulation to form one secondary oocyte and first polar body (which degenerates) • Secondary oocyte begins 2nd meiotic div. at ovulation but progresses only to metaphase of 2nd meiotic div. when division is arrested • If the sperm penetrates the secondary oocyte, the 2nd meiotic division is completed Oogenesis Cont… Prenatal • 1st meiotic div starts during early fetal life • 1st Meiotic div arrested at prophase stage • Oocyte maturation inhibitor produced by follicular cells Postnatal • At puberty i.e. Just before ovulation, primary oocyte completes 1st meiotic Div • Starts 2nd meiotic div at ovulation but is arrested at Metaphase • 2nd meiotic div completed after sperm penetration
  • 23. Follicle Maturation and Ovulation Oocytes ~2 million at birth ~40,000 at puberty ~400 ovulated over lifetime Leutinizing Hormone surge (from pituitary gland) causes changes in tissues and within follicle: • Swelling within follicle due to increased hyaluronan • Matrix metalloproteinases degrade surrounding tissue causing rupture of follicle Egg and surrounding cells (corona radiata) ejected into peritoneum Corona radiata provides bulk to facilitate capture of egg.
  • 24. • Note: • Long duration of the first meiotic division (up to 45 yrs) may account for meiotic errors e.g. Nondisjunction (failure of chromatids to dissociate) that occur with increasing maternal age • Primary oocytes in suspended prophase are vulnerable to environmental teratoges such as radiations • There are about 2 million primary oocytes in ovaries of newborn female infant • Many regresses and only about 400 become secondary oocytes and are expelled at ovulation during reproductive period
  • 26. Abnormal gametogenesis/gametes • Ideal maternal age for reproduction is 18-35 yrs of age • Risk of chromosomal abnormalities increases after age 35 yrs • Nondisjunction e.g. Down syndrome • Other form of trisomy • Gene mutation increases with age
  • 27. Textbooks • Either of the textbooks listed below are recommended for the course 1. Keith L. Moore, T.V.N. Persaud, Mark G. Torchia. (2011). The Developing Human: clinically oriented embryology (9th ed.). Philadelphia: Saunders. Publisher: Philadelphia, PA : Saunders/Elsevier, ISBN: 9781437720020 2. Schoenwolf, G.C., Bleyl, S.B., Brauer, P.R. and Francis-West, P.H. (2009). Larsen’s Human Embryology (4th ed.). New York; Edinburgh: Churchill Livingstone.