General Embryology Introduction PDF

Dr. Ashraf Elmansori Ass. Professor Anatomy department  Course Map Introduction Gametogenesis Female reproductive cycles (ovarian and menstrual cycles) Fertilization Differentiation of the embryoblast and trophoblast. Development of trilami...

Dr. Ashraf Elmansori Ass. Professor Anatomy department  Course Map Introduction Gametogenesis Female reproductive cycles (ovarian and menstrual cycles) Fertilization Differentiation of the embryoblast and trophoblast. Development of trilaminar germ disc and chorionic villi. Embryonic period. Derivatives of the 3 germ layers. Fetal membranes (placenta, amnion and umbilical cord) Fetal circulation Development of the integumentary system Development of the skeletal system Twins and congenital anomalies Objectives Outline the structure of the male genital system Outline the structure of the female genital system.  Importance of the embryology Greater understanding of embryology has resulted in new techniques for prenatal diagnoses and treatments; therapeutic procedures to circumvent problems with infertility; and mechanisms to prevent birth defects, the leading cause of infant mortality. The study of the embryological origins and causes for birth defects called teratology  A BRIEF HISTORY OF EMBRYOLOGY In 1961, the science of teratology became prominent because of the drug thalidomide that was given as an antinauseant and sedative to pregnant women. Unfortunately, the drug caused birth defects, including unique abnormalities of the limbs in which one or more limbs was absent (Amelia). The advent of molecular biology has advanced the field of embryology to the next level, and as we decipher the roles of individual genes and their interplay with environmental factors, our understanding of normal and abnormal developmental processes From a single cell to a baby in 9 months Embryonic development is directed by genomes that contain all of the information required to make an individual. The information is encoded in DNA in sequences called genes that code for proteins. In turn, proteins regulate expression of other genes and act as signal molecules to orchestrate development. There are approximately 23,000 genes in the human genome that coded for approximately 100,000 proteins  Male reproductive system Organs Function Pathways of the seminal cells.  Male reproductive system Consists of a number of sex organs that produce, store, and release the male gametes (sperms). Consists of external & internal genital organs.  External genital organs Penis Scrotum  Internal genital organs Testis. Epididymis. Vas deferens. Accessory glands: Seminal vesicles Prostate gland Bulbourethral gland  Penis The organ by which the sperm is delivered into the female vagina. Spongy tissue become turgid & erect when filled with blood.  Erectile tissue Corpus spongiosum: spongy tissue surround the urethra. Corpus cavernosa: two lateral sponge tissues. Urethra: tube that conveys the semen during ejaculation. Glans: rounded highly sensitive top of the penis. Prepuce: fold of skin covering the head.  Scrotum Pouce of skin bulges from the lower part of abdominal wall. It keeps the testis at a temperature slightly cooler the the body temperature.  Testis (testes) Two oval shape sex organ that produce sperms. Made of highly coiled seminiferous tubules. Produce also testosterone hormone.  Epididymis Worm shape structure adherent to testis. (6-7m) Important for maturation & storage of sperms.  Vas deferens (ductus deferens) Thin tube extends from the tail of the epididymis to the urethra in the penis. About 30 cm.  Seminal vesicles Sac- like structure attached to vas deferens on each side of the bladder. Produce yellowish fluid contain fructose.  Prostate gland Surround the ejaculatory duct and the base of the urethra just below the bladder. Responsible for production of the semen liquid ( mixture of sperm cells, prostate fluid & seminal fluids). Bulbourethral glands (Cowper’s gland) Two small glands on each side of the urethra just below the prostate. Produce clear slippery fluid directly into the urethra.  Female reproductive system Produce sex hormones (Estrogen & progesterone). Produce ova (eggs). Support & protect developing embryo.  Major organs Vagina Cervix Uterus Ovaries (gonads) Fallopian (uterine) tubes.  Vagina Muscular ridged sheath connects the external genitalia to the cervix. Lodge the penis during intercourse. An avenue through which the baby enters the world.  Female external genitalia Vulva: extends from the pubic area to the rectum. Labia majora: surround vagina & contain Bartholin’s gland which helps lubrication during intercourse. Labia minora: thin hairless ridges surround the entrance of vagina Clitoris: small pea shaped structure (important in sexual excitement)  External genitalia (continu) Urethral office: below clitoris & it is a passage for urine. Vaginal opening: just below the urinary opening. The hymen: thin crescentic fold of tissue partially covers the vaginal opening.  Ovaries (female gonads) Produce ova Current knowledge indicates that females are born with their entire lifetime supply of gametes( 1-2 millions ). Produce also estragon & progesterone.  Fallopian tube Extends from the uterus to the ovary. About 8-15 cm length. Its ovarian end called fimbria. The fimbria lines by tiny hair-like cilia. The cilia beat in waves to catch the egg & move it toward the uterus. Fertilization occurs typically in the fallopian tube. Uterus Pear shapes muscular organ Its upper part is called the fundus where the pregnancy occurs. Its lower part called the cervix which serve as a sphincter to keep the uterus closed till the time of birth. It enlarge 10-20 times its normal size during pregnancy. Myometrium The main part (myometrium) is lined by inner lining of vascular & glandular membrane (endometrium). The endometrium thickens during the menstrual cycle to allow implantation of the fertilized egg. Endometrium Endometrium is echogenic with an average thickness 8-15 mm (if less : unsuccessful outcome. During pregnancy: the blood vessels in the endometrium further increase in size & number to form the placenta. Placenta supplies the oxygen & nutrition to the embryo & fetus.