Lecture 1 Embryology PDF

# Lecture 1 Embryology ## Chapter 1: Embryology - **Embryology:** Science dealing with Formation, early growth & developing organisms, production of gametes from male and Female From gonads (Spermatogenesis) (Oogenesis) - **Human developmental anatomy:** - **embryology:** علم الأجنة - **p...

# Lecture 1 Embryology ## Chapter 1: Embryology - **Embryology:** Science dealing with Formation, early growth & developing organisms, production of gametes from male and Female From gonads (Spermatogenesis) (Oogenesis) - **Human developmental anatomy:** - **embryology:** علم الأجنة - **prenatal stages:** مراحل قبل الولادة - the intrauterine development till birth changes Occurs after birth - **Developmental stages of all chordates:** - **Maturation:** النضج - **Fertilization:** التخصيب - **Segmentation (cleavage):** التجربة - **Gastrula:** المعدة - **Neuralation and formation of organ rudiments:** العصبية وتشكيل أساسيات الجهاز - Formation of primitive organs and tissues - **Organogenesis:** تکوین - Differentiation of organs and integration of their function الأعضاء البدائية - **Gerology:** changes of old age ## Developmental anatomy of Mammalian:- 1. **Maturation and fertilization of the germcell, segmentation & Formation of the general pattern of the embryo** 2. **Implantation of the ovum and formation of fetal membranes & placenta** المشية الأغشية الجنينية 3. **Development and formation of individual systems** ## The Prenatal Period of Human:- 1. **Germinal Period:** fertilization and implantation of Blastocyst (18-21) day 2. **Embryonic period:** (4th week: 8th week). Most organs start developing 3. **Fetal period:** (9-38 week) - Body and organs grows rapidly. - Most of organs complete its developing. - Brain, Ear, Eyes, Teeth, adrenal gland, external genitalia الكظرية الأعضاء التناسلية الخارجية - develop and sensitive to teratogens المسخات / التشوهات ## PGCs & Reproductive Organs Origin:- - **Mature male & Female germ cells are direct descendants of PGCs.** - Appears in stalk wall of yolk sac in human embryo at end of 3rd week. - It migrates to developing gonads at end of 4th week - By amoeboid movement حركة أمبية - They arrive germinal Ridges at 6th week of development - If they fail in arrival to germinal ridges, gonads don't develop. - **Gorids start developing as a common analog, in the form of germinal ridges arrive from embryonic Kidney الركلة الجنسية** - **Direction of differentiation is determined by SRy gene, encoding te stis located on y chromosome determining factor** - **Male** ♂ - Thick Medulla - Thin Cortex - **Female** ♀ - Thin Medulla - Thick Cortex - PGC arranges at primitive sexcords PGE arranges at Cortex inside Medulla ## Body Cells - **Somatic:** جسمية - It is form the basic structural and functional units of all organisms. - It gives rise to all body cells except. reproductive germ cell - May exist and function:- - alone: individual blood cells. - in groups: tissues & organs - Diploid 2N - divide mitotically - there are 210 different types. each perform special function, like: - epithelial cells: lining closed internal body Cavities - Contractile cells. muscles - Neurons: electrically excitable in nervous system - Blood cells - Bones - **Germ:** جرثومية - Part of germ line - involved in gametes formation ova, sperm - Haploid N (23 chromosomes) containing half amount of DNA, genes no. - PGCs form the origin of germ cell - they migrate to gonal ridge where they form gametogonia and thus start gametogenesis ## Spermatogenesis: - **process of devebping of male spermatogna into mature spermatozoa** - **male version of gametogenesis** - **in mammals: occurs in testes, epidymis in a (stepwise fashion طريقة متدرجة** - **in human: take 64 days nearly.** - **توليد الحيوانات المنوية**