Revision General Embryology MCQ PDF

 Dr : Sherif Mohamed Zaki Revision Professor of General Embryology MCQ Anatomy & Embryology Fakeeh College for Medical Sciences  Spermatogenesis DEFINITION: It is the process of formation of spe...

 Dr : Sherif Mohamed Zaki Revision Professor of General Embryology MCQ Anatomy & Embryology Fakeeh College for Medical Sciences  Spermatogenesis DEFINITION: It is the process of formation of sperms. Spermatogonium (46) give rise to 1ry spermatocyte (46). 1ry spermatocyte undergoes 1st meiotic division to give two 2 ry spermatocytes (23). Each 2ry spermatocyte undergoes 2nd meiotic division to give two spermatids (23). SPERMIOGENESIS: changes that occur in spermatid to be transformed into a mature sperm.  Abnormalities of semen Hypospermia: Hyperspermia: Semen volume < 1.5 ml Semen volume > 5.5 ml  Abnormalities of sperm Count Morphology Motility Azoospermia: Oligospermia: Teratozoospermia: Necrospermia: Asthenospermia: absence of Sperm count less More than 40% of sperm are of presence of sperms in Decreased sperm motility. than 20 million/ml abnormal form dead sperms. semen  OOGENESIS Before birth, Oogonia (46) proliferate & enlarge to form Primary Oocytes (46). From puberty to menopause (ovarian cycle): Primary Oocyte completes 1st meiotic division & gives rise to secondary Oocyte (23) After fertilization: 2ry oocyte completes 2nd meiotic division forming mature Oocyte (23)  Ovarian cycle 1- Follicular phase Under control of FSH. This phase is characterized by production of estrogen. Ends by formation of Graafian follicle 2- Ovulation It is rupture of Graafian follicle Cause: Luteinizing Hormone (LH) surge 3- Luteal phase Under the effect of LH The ruptured Graafian follicle becomes corpus luteum. Corpus luteum secretes progesterone.  Life span of corpus luteum: If fertilization does not occur: – Corpus luteum lives for 9 days only after ovulation. – Then, it is transformed into corpus albicans. If fertilization & pregnancy occur: The developing embryo secretes Human Chorionic Gonadotrophic (HCG), which stimulates corpus luteum to grow forming corpus luteum of pregnancy.  Phases of menstrual cycle Menstruation Proliferative phase Secretory phase Duration: 3-5 days Duration: 10 days. Duration: 14 days. Hormonal factor: Hormonal factor: Hormonal factor: withdrawal of estrogen. progesterone progesterone.  Fertilization Definition: It is the union of a sperm & an oocyte. Site: ampulla of Fallopian tube.  1- Maturation of sperms Capacitation: Acrosomal reaction: Removal of cholesterol coat & glycoprotein Development of perforations in coat that covers acrosomal cap. acrosomal cap.  2- Phases of fertilization Phase 1 : Phase 2 : Penetration of the corona radiata. Penetration of the zona pellucida.  3- Prevention of Polyspermy Fast block: rapid electrical Slow block: cortical & zonal depolarization of the plasma reactions membrane of the oocyte  3- Pronuclei Stimulation of the 2nd meiotic The nucleus of the division of the 2ry oocyte : the sperm enlarges to nucleus of mature oocyte form male becomes the female pronucleus. pronucleus  Results of fertilization: The diploid number of chromosome (46) is restored. The sex of the embryo is determined. A series of mitotic divisions called cleavage division start. The most sensitive period for inducing birth defects is 3rd - 8th weeks (the period of embryogenesis).  Cleavage division Site : Fallopian tube. Steps : The 2-cell stage. The 4-cell stage. Morula (12-16-cell stage): –Time: 3rd day after fertilization. –Its cells are arranged into inner cell mass & outer cell mass. –It is surrounded by zone pellucida.  BLASTOCYST Time: 4th day after fertilization. Composed of –An outer shell of cells called the trophoblast. –An inner cell mass called the embryoblast. The zona pellucida disappears about the 5th day.  Implantation Normal site of implantation: endometrium of the posterior & superior walls of the body of uterus. Time of implantation: –Started by 6th -7th day. – Completed by 11th-12th day. Abnormal sites of implantation  Outside the uterus: (ectopic pregnancy): Uterine tube (tubal pregnancy) Abdominal cavity. Ovary (ovarian pregnancy).  Placenta previa Is a placenta, which develops, in the lower segment of uterus near the internal os. Types of Placenta Previa Low lying Marginal Partial placenta Complete placenta previa placenta previa previa placenta previa Low lying placenta previa: the placenta is in lower part of uterus but does not reach the internal os. Marginal placenta previa: the edge of placenta reaches the margin of internal os Partial placenta previa: the placenta covers the internal os partially. Complete placenta previa: The placenta completely covers the internal os.  Where does fertilization normally occur ? A. In the fundus of the uterus. B. In the posterior wall of uterus. C. In the anterior wall of uterus. D. In the ampulla of the uterine tube. E. Near the cervical canal When does the second meiotic division of the secondary oocyte complete ? A. At foetal life. B. Before ovulation. C. At time of ovulation D. At Fertilization. E. In the Menstrual cycle.  Which one of the following stages is concerning to implantation ? A. 2-cell stage. B. 4-cell stage C. 8-cell stage. D. Morula stage. E. Blastocyst stage. Which one of the following is the result of fertilization ? A. Restoration of the diploic number of chromosomes. B. Formation of blastocyst. C. Formation of morula D. Initiation of implantation of the zygote. E. Beginning of 2nd meiotic division.  Removal of cholesterol coat & glycoprotein coat that covers the acrosome is called: A- Capacitation B- Acrosomal reaction C- Cortical reaction D- Zonal reaction 10/17/2023 Dr Sherif Zaki 31 The following hormone is used for detection of pregnancy A. Estrogen B. Progesterone C. Human Chorionic Somatomammotropin D. Human Chorionic Gonadotrophin E. Human Chorionic Corticotropin The preovulatory phase of ovarian cycle is under the influence of the following hormone A. Progesterone B. Follicular stimulating hormone C. Luteinizing hormone D. Human Chorionic Gonadotrophin E. Human Chorionic Corticotropin  The postovulatory phase of ovarian cycle is under the influence of the following hormone A. Estrogen B. Follicular stimulating hormone C. Luteinizing hormone D. Human Chorionic Gonadotrophin E. Human Chorionic Corticotropin  2nd week changes Embryonic disc is 2 layers Epiblast Hypoblast Two cavities Amniotic cavity 1ry then 2ry yolk sac Trophoblast is 2 layers Cytotrophoblast Syncytiotrophoblast Extra-embryonic mesoderm differentiated into 2 layers by chorionic cavity: Somatopleuric mesoderm. Splanchnopleuric mesoderm. Two membranes are formed Amnion Chorion 3rdweek changes Gastrulation: The process of formation of the three germ layers (ectoderm, mesoderm & endoderm).  Teratogenesis Associated with Gastrulation Caudal dysgenesis (sirenomelia) Tumors Associated With Gastrulation Caudal dysgenesis (sirenomelia) Insufficient mesoderm is formed in the caudal most region. Because this mesoderm contributes to formation of lower limbs, urogenital system & lumbosacral vertebrae, abnormalities in these structures ensue. Sirenomelia = mermaid  Teratogenesis Associated with Gastrulation Caudal dysgenesis Tumors Associated With Gastrulation (sirenomelia) (sacrococcygeal teratomas) Sacrococcygeal teratomas Remnants of primitive streak persist in sacrococcygeal region. These clusters of pluripotent cells proliferate and form tumor that contains tissues derived from all 3 germ layers Derivatives of germ layers  Derivatives of ectoderm Epidermal Neural Neural Epidermis placodes Tube (PNS) Lens Brain Skin Spinal Inner ear cord Hair Breast Neurulation: is the process of transformation of neural plate into neural tube. Neural tube develops into spinal cord & brain.  INTRA-EMBRYONIC MESODERM Para-axial Intermediate Lateral plate 1- Paraxial gives rise to somites that differentiate 2) Intermediate into derivatives: Sclerotomes give rise to –Suprarenal cartilage & bones (vertebral cortex. column) –Kidney. Dermomyotome: divides –Gonads (testis & into: ovary). –Dermatome: develops into dermis. –Myotome: develops into skeletal muscles.  INTRA-EMBRYONIC MESODERM Lateral plate Para-axial Intermediate divided by intra-embryonic coelom into Somatic layer Visceral layer –Lateral plate gives rise to: Connective tissue & muscles of body wall. Connective tissue & smooth muscles of GIT & respiratory system. –Serous membranes :pleura , pericardium & peritoneum. –CVS. –Septum transversum: gives diaphragm.  Derivative of endoderm Digestive system. Respiratory System. Most of urinary bladder & urethra.  Folding Definition: Conversion of embryo from a flat embryonic disc into 3- dimensional structure Time: 3rd – 4th weeks.  Types of folding Head & tail folds Lateral folds  Results of folding Effects on amniotic cavity Effects on yolk sac The amniotic cavity expands & surrounds the embryo from all sides  Results of folding Effects on amniotic cavity Effects on yolk sac The 2ry yolk sac is differentiated into 3 parts: ▪ The part incorporated into the embryo form primitive gut. ▪ The part remains outside the embryo is called definitive yolk sac. ▪ The part in-between is called vitello-intestinal duct which becomes yolk sac stalk.  Results of folding Effects on amniotic cavity Effects on yolk sac Primitive gut Definitive yolk sac Yolk sac stalk Foregut Midgut Hindgut Which one of the following is ectodermal derivative? A. Epidermis B. Dermis C. Urinary bladder D. Urethra E. Uterus Which one of the following is endodermal derivative? A. Epidermis B. Dermis C. Urinary bladder D. Heart E. Uterus Which one of the following is mesodermal in origin? A. Epidermis B. Dermis C. Urinary bladder D. Trachea E. Stomach  The process of formation of 3 germ layers is called A. Morula B. Gastrulation C. Neurulation D. Capacitation E. Blastula The following areas of the embryo is bilaminar A. Buccopharyngeal membrane B. Septum transversum C. Cardiac area D. Lens E. Neural plate  Components of placenta Maternal part: Fetal part: formed by chorion frondosum formed by decidua basalis.  Parts of chorion Chorion frondosum: Chorion leave: The villi forms the fetal part of placenta The villi degenerate  Components of placenta Maternal part: Fetal part: formed by the chorion frondosum formed by the decidua basalis. Definition Decidua is the endometrium after implantation Parts of decidua: Decidua basalis: part which lies over chorionic frondosum. Decidua capsularis: part which covers chorion laeve. Decidua parietalis: part which lines the remaining part of uterine cavity.  Internal structure of placenta Chorionic villi Intervillous spaces Placental septa The villi are filled with fetal blood The intervillous spaces are filed with maternal blood Placental septa divide maternal surface of placenta into 15-20 cotyledons.  Placental barrier Is the tissue barrier between fetal & maternal blood. In early pregnancy it is formed of: Endothelial of the fetal vessels. In late pregnancy it is formed of: Extra-embryonic mesoderm. Endothelial of the fetal vessels. Cytotrophoblast. Syncytiotrophoblast. Syncytiotrophoblast.  It is a disc-shape Its diameter is 15 –25 cm Its thickness is 3 cm Its weight is 500 g Full term placenta  Full term placenta Fetal surface: - Is formed by chorion frondosum. Maternal surface: - Is smooth & covered by amniotic - Is formed by decidua basalis. membrane. - Is rough & irregular. - Umbilical cord is attached near its - Is divided into 15 –20 cotyledons. center.  Anomalies of placenta Anomalies in Anomalies in Placenta Anomalies in shape attachment invasion previa of cord Anomalies in shape Diffuse placenta (placenta membranacea): all fetal membranes remain covered by chorionic villi Accessory placenta (succenturiate placenta): a main placenta & a small accessory lobe Bidiscoidal placenta: The placenta is formed of 2 disc-like equal parts  Anomalies of placenta Anomalies in Anomalies in Placenta Anomalies in shape attachment of invasion previa the cord Anomalies in invasion Placenta accreta: The placenta grows superficially into the myometrium Placenta increta: The placenta grows into the myometrium. Placenta percreta: placenta invades the myometrium & peimetrium.  Placenta previa It Is a placenta, which develops, in the lower segment of uterus near the internal os. Types of Placenta Previa Low lying Marginal Partial placenta Complete placenta previa placenta previa previa placenta previa Low lying placenta previa: the placenta is in lower part of uterus but does not reach internal os. Marginal placenta previa: the edge of placenta reaches the margin of internal os Partial placenta previa: the placenta covers the internal os partially. Complete placenta previa: The placenta completely covers the internal os.  Amnion Sources: Secretion from amnioblastic cells & excretion of the kidneys of fetus Amount: 1500 cc.  Function of amniotic fluid In early pregnancy : 1- Protective watery cushion 2- Keeps temperature constant. During birth : 1- Dilatation of cervix. 3- Prevents adhesion of fetus to amnion. 2- The amniotic fluid 4- Allows free movements of fetus. washes the vagina. 5- The fetus learn how to suckle. 6- A space for urine accumulation  Amniotic fluid abnormalities Polyhydramnios Oligohydramnios Definition: volume more than 2 liters Definition: volume less than ½ liter. Causes: Causes: 1- Idiopathic 1- Placental insufficiency with low placental 2- Maternal diabetes which causes fetal hyperglycemia & blood flow polyuria. 2- Renal Agenesis. 3- Fetal anomalies 3- Obstructive Uropathy (urinary tract a) Esophageal atresia that impairs the ability of fetus obstruction) lead to absence of fetal urine to swallow b) Anencephaly impairs swallowing reflex.  Blood formation Primordial germ cells migrate into the developing gonads & differentiate into spermatogonia or oogonia endoderm of yolk sac is incorporated into the embryo as the primitive gut. Allantoic vessels persist as umbilical vessels. Definitive umbilical cord Soft & tortuous Length : 50-60 cm Diameter : 1 cm It has a smooth surface as it is covered by amnion. It is attached to the fetal surface of placenta near its center.  NB – Connecting stalk forms Wharton's jelly – Allantoic vessels form umbilical vessels.  Anomalies of umbilical cord Anomalies of Number of Anomalies in length Knots attachments umbilical arteries Very long umbilical cord : may wind around the neck of the fetus & cause its death Very short umbilical cord: may cause premature separation of the placenta.  Anomalies of cord Anomalies of Number of Anomalies in length Knots attachments umbilical arteries Eccentric attachment. Marginal attachment (battledore placenta). Velamentous attachment : the cord ends in the membranes surrounding placenta.  Anomalies of cord Anomalies of Number of Anomalies in length Knots attachments umbilical arteries False knots: – It is caused by excessive tortuosity of umbilical vessels. – These are normal & do not cause harm of the fetus. True knots: – rare , but dangerous as they cause obstruction to flow of blood in umbilical vessels leading to death of the fetus  Anomalies of cord Anomalies of Number of Anomalies in length Knots attachments umbilical arteries Single umbilical artery: Twins  Dizygotic Monozygotic Incidence: 70% of twins. 30% of twins. Two ova are released from the ovary Splitting of a single original Mechanism of development: simultaneously embryo 2 placentae , 2 chorionic cavities. Share none , some or all their Characters: 2 amniotic cavities. fetal membranes Sex: They may be of the same or different sex. They are of the same sex. external appearance Have different features. They are identical.  Siamese (CONJOINED)TWINS Fused monozygotic twins that occurs due to incomplete separation of embryonic disc. They could be either: Craniopagus: Fusion between 2 heads. Thoracopagus: Fusion at thoracic region. Pygopagus: Fusion at the pelvic region.  Techniques used in prenatal diagnosis Non-invasive Invasive Maternal serum Amniocentesis screening Chorionic villus Ultrasound sampling (CVS)  Maternal serum screening Alfa-fetoprotein (AFP) Unconjugated estriol (uE3): HCG Its concentration in maternal serum increase Increases-----Neural tube defect Higher--- Down syndrome throughout pregnancy. Decreases------ Down syndrome Decreases ----- Down syndrome  Invasive tests Amniocentesis Chorionic villous sampling Chorionic villous sampling Collection of chorionic villi under ultrasound guidance Preferred: 10 weeks gestation. Indications: – DNA analysis – Chromosomal abnormalities  Invasive tests Amniocentesis Chorionic villous sampling AMNIOCENTESIS A needle is inserted transabdominally into amniotic cavity (guided by ultrasound) & 20 to 30 mL of fluid is withdrawn. Preferred time: 16 weeks gestation. Fluid can be used for estimation of – Bilirubin level for hemolytic disease. – Alfa fetoprotein. – Fetal cells for karyotyping The following structure forms the fetal part of placenta A. Decidua basalis B. Decidua capsularis C. Decidua parietalis D. Chorion frondosum E. Chorion laeve  The following structure forms the maternal part of placenta A. Decidua basalis B. Decidua capsularis C. Decidua parietalis D. Chorion frondosum E. Chorion laeve  The following is a cause of polyhydramnios A. Diabetic mother B. Thalassemic mother C. Anemic mother D. Fetus with renal agenesia E. Fetus with obstructive uropathy  The following is a cause of oligohydramnios A. Diabetic mother B. Thalassemic mother C. Fetus with esophageal atresia D. Fetus with renal agenesia E. Fetus with anencephaly  The next figure represents which of the following placental anomalies A. Placenta membranacea B. Circumvallate placenta C. Placenta accreta D. Velamentous placenta E. Succenturiate placenta  The next figure represents which of the following placental anomalies A. Placenta membranacea B. Circumvallate placenta C. Placenta accreta D. Placenta previa E. Succenturiate placenta