Introduction to Embryology (Med) PDF

INTRODUCTION to EMBRYOLOGY Learning Objectives • Define the embryological terminations and name of the events in human development Menstruel Age žMenstruel Age: Most doctors calculate the start of pregnancy from the first day of your last menstrual period. žThis is called the "menstrual age" and...

INTRODUCTION to EMBRYOLOGY Learning Objectives • Define the embryological terminations and name of the events in human development Menstruel Age žMenstruel Age: Most doctors calculate the start of pregnancy from the first day of your last menstrual period. žThis is called the "menstrual age" and is about two weeks ahead of when conception actually occurs. Menstruel Cycle and Menses ž Each menstrual cycle typically lasts for 28 days. Thus it occurs every month. ž If no sperm is around to fertilize the egg, The egg and the corpus luteum will degenerate, removing the high level of hormones. ž This causes the endometrium to slough off, resulting in menstrual bleeding. žThen the cycle repeats itself. https://www.youtube.com/watch?v=zcvo9VLVHWc Oogenesis (Ovogenesis) and Ovulation Oogenesis: ž It is the sequence of events by which oogonia are transformed into mature oocytes. ž This maturation process begins before birth and is completed after puberty (12 to 15 years) and continues to menapouse, which is permanent cessation of the menses. Ovulation: ž The release of the ripe egg from the ovary. ž The egg is released when the cavity surrounding it (the follicle) breaks open in response to a hormonal signal. ž Ovulation occurs around fourteen or fifteen days from the first day of the woman's last menstrual cycle. ž When ovulation occurs, the ovum moves into the fallopian tube and becomes available for fertilization. Oogenesis (Ovogenesis) and Ovulation Ovarian Cycle • • • • FSH and LH produce cyclic changes in the ovaries. The ovarian cycle is development of folllicles, ovulation, and corpus luteum formation. During each cycle, FSH promotes growth of several primordial follicles into primary follicles. However, only one primary follicle usually develops into a mature follicle and ruptures through the surface of the ovary. Oocytogenetic cycle ›First Step: Beginning to primordial germ cell migration from secondary yolk salk to genital ridge at the postfertilization 4th week. ›Second Step: Mitosis in the genital ridge and formed ovary. (from 6 week to 18 week) ›Third Step: Beginning to Meiosis I and apoptosis (at the 5th month). All primordial oogonia enter the meiosis I and arrested diplotene stage of prophase I. ›Last Step: Start the puberty. Selected primary oocyte continues to meiotic division. ›This step stop the metaphase II. If fertilization would be occurred meiosis is continuous. Foliculogenesis • It is the development of follicles. • The ovarian cycle can be divided into 3 phases:. 1. Follicular phase From many primordial follicles one Graafian follicle develops. 2. Ovulatory phase The graafian follicle is released. 3. Luteal phase The corpus luteum and corpus albicans are produced. Spermatogenesis ž It is the sequence of events by which spermatogonia are transformed into mature sperms or spermatozoa. Spermatogenesis Stage: ›Spermatocytogenesis: Mitosis ›Spermatidogenesis: Meiosis ›Spermiogenesis: Differantiation Embryology • • • Embryology (from Greek, embryon, "unborn, embryo"; and logia is a science. It is about the development of an embryo from the fertilization of the ovum to the fetus stage. Embryology is study of the process and events in the development of the embryo Oocyte (egg) • • The female gamete is often called the ovum. In reality, it is released from the ovary and before it can truly be called ‘ovum’. ž ž The term spermatazoon also has a Greek origin (spermatos, seed + Zoon, animal). The sperm or spermatazoon refers to the male cell produced in the testes (testicles). Fertilization • • Fertilization is the union of the male and female gametes. It is pertinent to note that the female gamete has not completed the second meiotic division at the time of release from the ovary. https://www.youtube.com/watch?v=HuWCwyRiaUI Zygote ž This cells from the union of an oocyte and sperm. ž A zygote is the begininig of a new human being. https://www.youtube.com/watch?v=MyxSQL7_7ko Cleavage ž Cleavage consists of repeated mitotic divisions of the zygote, resulting in a rapid increase in the number of cells. Morula-Compaction ž Morula is a solid mass of cells (blastomeres) resembling a mulberry, formed by cleavage of a fertilized ovum. ž Compaction: When embryo enters the forth division, blastomeres maximize their contact with each other. They form a compact ball of cells held together by tight junctions. Blastulation-Blastocytes ž Blastulation: Formation of the blastula or blastocyst from the morula. ž Blastocytes: After the morula, enters the the uterus from the uterine tube a fluid filled cavity develops inside it. Hatching • Hatching: To emerge from or break out of an egg Cleavage-Morula-Compaction-Blastulation-Blastocytes-Hatching Implantation • • Implantation refers to the attachment of the zygote to the wall of the uterus . The outer layer of this cell mass or trophoblast attaches itself by secreting proteolytic enzymes, which erode the uterine wall cells, gradually embedding itself firmly in the uterine wall. https://www.youtube.com/watch?v=PAVo16b_6j4 Embryo • • The developing human during its early stages of development. The embryonic period extends to the end of the eighth week (56 days) by which time the beginnings of all major structures are present. Organogenesis • It is the process by which the ectoderm, endoderm, and mesoderm develop into the internal organs of the organism. Fetus • After the embryonic period (8 weeks), the developing human is a fetus. Infancy • • It refers to the earliest period of extrauterine life; roughyl the first year after the birth. An infant aged 1 month or less is a called a newborn or neonate. Childhood • • Childhood is the period from about 13 months until puberty (sexuel maturity). The primary (deciduous) teeth continue to appear and are later replaced by the secondary (permanent) teeth. Adolescence • It is the period from about 11 to 19 years of age, which is characterized by rapid physical and sexuel maturity. Adulthood ž Adulthood (attainment of full growth and maturity) is generally reached between the ages of 18 and 21 years. ž One reaches their maximum height and secondary sex characteristics form such as body hair and facial hair, voice lowers in pitch (especially noticeable in men), and menses begin (women). Conception ž Conception is the moment that a man's sperm successfully fertilizes a woman's egg (the act of becoming pregnant; fertilization of an ovum by a spermatozoon). Pregnancy Period • Traditionally a human pregnancy is considered to last approximately 40 weeks (280 days) from the Last menstrual period (LMP), or 38 weeks (266 days) from the date of fertilization. TRIMESTER • • A period of three calender months during a pregnancy. Obstetricians commonly divide the 9 month period of gestation into three trimesters. 1 th Trimester Fertilization (minutes to hours) Preimplantation (~1 week) Implantation (several days) Organogenesis (8-10 weeks) Embryonic period 2nd and 3rd Trimesters • Developmental processes result primarily in GROWTH and FUNCTIONAL MATURATION Embryonic Period • • Progression of DIFFERENTIATIVE and MORPHOGENIC events resulting in the establishment of basic STRUCTURAL BODY FORM (but not size) Accomplished as a result of 3 basic processes: – (1) Cell division – (2) Cell migration – (3) Cell death Fetal Period During the fetal period (9 weeks to birth), differentiation and growth of tissues and organs formed during embryonic period occur. Gestational Age • • It is about two weeks longer than the fertilization age. Because the oocyte is not fertilized until about two weeks after the preceding menstruation. NAEGELE’S RULE: žNaegele's Rule is a standard way of calculating the due date for a pregnancy. žThe rule estimates the expected date of delivery (EDD) by adding one year, subtracting three months, and adding seven days to the first day of a woman's last menstrual period (LMP). žThe result is approximately 280 days (40 weeks) from the LMP. žThe standard definition for gestational term is 266 days from conception to the date of the baby’s birth. This is also defined as 280 days, or 40 weeks, from the first day of the mother’s last menstrual period, a definition which assumes that the mother ovulates on day 14 of a 28 day menstrual cycle. Determination of Gestational Age •Naegele’s Formula: 1. Adding a year, 2. Subtracting three months 3. Adding seven days The calculation method does not always result in a 280 days because not all calendar months are the same length, it does not account for leap years. •The Dating Game… •Scenario 1 •• 24 young woman, 1st pregnancy, LMP = Dec 1st 2009, what is the due date? 1.Dec 1st 2009 + 1 year= Dec 1st 2010 2.Dec 1st 2010 – 3 mounts = September 1st 2010 3.September 1st 2010 + 7 days = September 7th 2010 4.Whereas precisely 280 days would be September 11th 2010. Maternity ž The feelings or characteristics associated with being a mother; motherliness. Pregnancy ž This term is the carrying of one or more offspring, known as a fetus or embryo, inside the body of a female humans. https://www.youtube.com/watch?v=y4HK5CTVkXM ALWAYS BE HAPPY…