Introduction to Embryology-445.pdf

Introduction to Embryology Main Text Important Female slides Male slides Doctor’s notes Editing File Extra info Objectives Define Embry...

Introduction to Embryology Main Text Important Female slides Male slides Doctor’s notes Editing File Extra info Objectives Define Embryology. Define the developmental periods. Define the significance of embryology. Knew the different embryological terminology. Define the nomenclature used to describe body parts, positions, and relationships. Describe in brief the important events in embryology.  Definition of Embryology Embryology Human Embryology It is a branch of biology that includes the study of the Is the science concerned with the origin and formation, growth, and development of new development of a human being starting from individuals from an egg. a zygote to the birth of an infant. It refers to the prenatal stage of development including fertilization, zygote formation, and Development does not stop at birth. embryonic and fetal development specifically the Important changes, in addition to growth formation of germ layers. , simply refers to prenatal occur after birth ( postnatal changes ) development of embryos and fetuses. e.g.development of teeth and female breasts.  Significance of Embryology The study of prenatal stages of development, especially those occurring during the embryonic period is important to understand : the normal and abnormal body structure. to better understand congenital malformation including their causes so that they can be avoided. So,It is concerned with various genetic and/or environmental factors that disturb the normal development producing birth defects Developmental anatomy : is powerful adjunct to an in-depth understanding of gross anatomical pattern.  Developmental Periods 1-Prenatal Development 2-Postnatal Development It is the main developmental 1 The changes occurring after changes occurring before birth birth, like teeth and breast. including The Embryonic The Fetal Period Period 2 NOTE : Prenatal development is more rapid Starts from Begins from the than postnatal development and fertilization to the 9th week until results in more striking changes. end of 8th week birth The most critical period is the 444 note embryonic period, especially from week 3 -> 8.  Critical Periods of Human Development IN MALE SLIDES ONLY What are critical periods of development? This is the stage of development Each part of fetus’s body forms at of an embryo that is susceptible to specific time. an agent, such as a drug or virus, During these times, the which can lead to congenital developing fetus is very sensitive to abnormalities. injury caused by some drugs, Embryological Development : is alcohol, virus, x-rays. most easily disrupted when the This specific time is called the tissues and organs are forming “critical period of development” for during the embryonic period. that body part.  Common Terminology 1-Oocyte 2-Ovum 3-Sperm the immature ovum the mature female the mature male germ or female germ cell. germ cell. cell. 4-Zygote 5-Neonate/Newborn the fertilized ovum. First 28 days of life 6-Infant 0 to 1 year  Common Terminology cont. 7-Cell Division One cell divides into two daughter cells in mitosis while 4 cells in meiosis, there are two types of cell Division: Reduction Division Mitosis Meiosis Primitive germ (sex) cells in the Somatic cells Occurs in testes and ovaries 2 cells Produces 2 cells then 4 cells Only one stage Stages Two stage 44 Autosome 22 46 (diploid) 23 (haploid) Sex 2 (Diploid number) 1 (Haploid number) Chromosomes  Common Terminology Related to direction: Related to the plans or section: Longitudinal Coronal Transverse Cranial : the top of the embryo Median or sagittal Frontal Horizontal or the head. Cephalic : superior or the head. Ventral : anterior or the belly side. Dorsal : back of the embryo. Divides the body into Divides the body into Divides the body into right & left parts anterior & posterior parts upper & lower parts Caudal : inferior or the tail end. Medial : near to the midline. Lateral : flank side. Cranial/Cephalic Ventral Dorsal Caudal  Major Events During Embryonic Period Gametogenesis & Fertilization 1st week Implantation Begins one week after fertilization Development of the CNS and Heart Begins at 3rd week Embryonic folding 4th week  Gametogenesis It is the production of mature gametes ( sperm & ova ), in the gonads ( Testes & ovaries ). Spermatogenesis Oogenesis ( In Males ) ( In Female ) It is the process of formation of It is the process of formation of mature sperms. mature ovum. Occurs in the seminiferous tubules It occurs in the cortex of the of testis. ovary. starts during fetal life. Starts from puberty till old ages. (9th week until birth) It ends by formation of mature completed after puberty (primary sperms with oocyte).ovulation starts(secondary haploid number of chromosomes. oocyte)and fertilization complete (secondary oocyte) continues till menopause. It ends by formation of mature ovum with haploid number of chromosomes. Results of spermatogenesis : 1. Reduction of chromosomal number from the diploid to the haploid number. 2. Change the primitive germ cell (spermatogonia) to the motile sperm. 3. Increase the number of the sperms. It is the process during which a mature Fertilization male Definition : gamete ( sperm ) unites with a mature female gamete ( ovum ) to form a single cell ( ZYGOTE ). It occurs in the uterine tube. Site : ( ampulla ) ( or Fallopian tube ) Fertilization The diploid number of chromosomes is restored. Result : The sex of the embryo is determined. Initiates cleavage ( Cell division ) of the zygote. ( via mitosis )  Implantation It is the process of embedding of the blastocyst in the endometrium of the uterus. It begins one week after fertilization. It is completed by the 12th day after fertilization. Normal site Abnormal site (ectopic pregnancy) In the upper part of the Most common type of posterior surface of the uterus ectopic pregnancies occurs near the fundus.(X) in the uterine tube ( Fallopian tube ). Tubal pregnancy is the most common type of ectopic pregnancy.(A) Ovarian pregnancy is the least common type of ectopic pregnancy.(H)  Bilaminar Disc Trilaminar Disc Formed by the differentiation of the cells into In week 3 the embryonic disc is formed of 3 layers : Two layers ( 2 germ layers in Week TWO ): A. Epiblast : ( Epi = up ) -Embryonic Ectoderm - High columnar cells adjacent to the amniotic ( formation of CNS and skin ) cavity. -Intraembryonic Mesoderm - develops into embryonic ectoderm. ( formation of skeletal muscles and connective tissues) B. Hypoblast : ( Hypo = down ) -Embryonic Endoderm - Small cuboidal cells adjacent to Yolk sac. ( formation of cardiovascular tissues ) - developers into embryonic endoderm. Cells in these layers will give rise to all tissues and organs of the embryo.  MCQs 1-When is embryological development most easily disrupted? A)During the fetal period B)During the embryonic period C)after the birth of the child D)the 9th week after fertilization 2-how many stages in Mitosis and Meiosis divisions respectively ? A) 2 and 1 B) 2 and 3 C)1 and 2 D)1 and 1 3- when the development of the CNS and Heart begins ? A)3rd day B)4th week C)5th week D)3rd week Don’t look 4-How many sperms are produced from primary spermatocytes? 5-B 4-D 3-D 2-C A-3 sperms B)2 Spermatids C) 2 sperms D)4 sperms 1-B 5- Which one of these formed the floor for the amniotic cavity ? A)Hypoblast B)Epiblast C)Trophoblast D)syncytiotrophoblast  MEET THE TEAM TEAM LEADERS : Munira Al-Mutairi Abdullah Mujalled TEAM MEMBERS : Fatima Alsayegh🧬 Faris Aldawood🧬 Hala Alanzi Fahad Almousa Fatima Alhubail Albara Aljohani Sarah Almohsen Faisal Abdulrahim Layan Alqarni Firas Alnakhli [email protected]