Fetal Membranes 1 Lecture 7 PDF

Fetal Membranes I Anatomy Unit  Objectives  1. By the end of this lecture , the student should be able to: 2. Define the fetal membranes 3. Describe the development , types ,functions and anomalies of amnion 4. Describe the develop...

Fetal Membranes I Anatomy Unit  Objectives  1. By the end of this lecture , the student should be able to: 2. Define the fetal membranes 3. Describe the development , types ,functions and anomalies of amnion 4. Describe the development , types ,functions and anomalies of yolk sac 5. Describe the development , types ,functions and anomalies of allantois  Case scenario A 32-year-old woman was referred to ER complaining of sudden passage of a large amount of fluid from the vagina. During the examination, the woman is 35 weeks pregnant, and a little amount of fluid is passing through the cervix with cervical dilatation. A. What is your diagnosis? B. What is the nature of fluid? C. What is the normal amount of this drained fluid? D. Mention 2 anomalies related to this fluid. Fetal Membranes Definition: Structures derived from fertilized ovum and not share in formation of embryo Fetal membranes include:  1) Amnion.  2) Yolk sac.  3) Chorion.  4) Allantois.  5) Connecting stalk & umbilical cord.  6) Placenta.  Amnion  Definition: sac filled with fluid that surrounds the embryo  Time of appearance: 7th or 8th day after fertilization (During implantation).  Development: At first bounded by Roof: Amnioblast Floor: epiblast After folding: completely surround the embryo Amniotic fluid  Definition: fluid fills amniotic cavity  Amount: one liter at birth.  Composition: 99% water. desquamated epithelial cells, organic constituents: CHO, enzymes, fats, hormones, pigments and inorganic salts. Fetal excreta (urine) added to amniotic fluid as pregnancy advances. Amniotic fluid  Source: 1. Amnioblast 2. Placenta. 3. Fetal urine (kidney)  Circulation:  The fluid accumulates in amniotic cavity.  Swallowed by the fetus and absorbed by GIT & Respiratory system (fetus drink 400c.c at 5th month).  Fluid passes to fetal blood 1. waste products cross placental membrane and enter maternal blood 2. Excess water excreted as urine in amnion Function of amnion  Allows fetal movements.  Allows symmetrical growth of fetus.  Prevent adhesion between different parts of fetus.  Prevent (Barrier against) infection  Maintain body temperature of fetus.  Maintain fluid and electrolytes balance.  Protection against trauma and external shock. (cushion) During birth: 1. Dilatation of cervix due to bulge of bag of water that proceed head of fetus in cervical canal. 2. Fluid passes through vagina when bag rupture and act as antiseptic against infection. Amnion OLIGOHYDRAMNIOS POLYHYDRAMNIOS Definition Amniotic fluid less than ½ liter Amniotic fluid more than 2 liters Causes  Placental insufficiency  Idiopathic  Renal agenesis (absent kidney)  Fetal factor: esophageal atresia (obstruction)  Maternal factor (diabetes) Features  Fetal adhesion  Distress to mother and fetus  Fetal abnormalities  Excessive fetal movement casues true knots of the cord  Preterm (premature) labor AMBOSS: https://next.amboss.com/us/article/dO0orT?q=oligohydramnios#Zeb92421b0da5a64f246c83901a7b0a52  Case scenario A 32-year-old woman was referred to ER complaining of sudden passage of a large amount of fluid from the vagina. During the examination, the woman is 35 weeks pregnant, and a little amount of fluid is passing through the cervix with cervical dilatation. A. What is your diagnosis? B. What is the nature of fluid? C. What is the normal amount of this drained fluid? D. Mention 2 anomalies related to this fluid.  Case scenario A newborn baby presents with fluid draining from the umbilicus onto the skin. Testing of the fluid identifies it as urine. What is the most likely diagnosis? A. Urachal cyst. B. Urachal fistula. C. Urachal sinus D. Urachal diverticulum E. Bifid ureter.  Yolk sac  Definition: cavity in relation to ventral aspect of embryo  Time of appearance: 9th day after fertilization (During implantation).  Development: At first bounded by Roof: hypoblast Floor: Heuser’s membrane After folding: The part inside embryo: primitive gut The part outside embryo: definitive yolk sac Yolk Sac After folding  The definitive yolk sac remains connected to the midgut by a duct called Vitelline duct  Both become a content of the umbilical cord  Later, the definitive yolk sac and the vitelline duct degenerate and disappear  Yolk Sac Anomalies: Vitelline fistula: failure of obliteration of whole vitellointestinal duct (abnormal connection between midgut and umbilicus) Functions of Yolk Sac 1. Transfer nutrients to embryo (in 2nd and 3rd weeks). 2. Its endoderm gives epithelium of trachea, bronchi, lungs and digestive tract (in 4th week). 3. Primordial germ cell appears in endoderm of wall of yolk sac and migrates to developing sex organ at 3week. 4. Development of blood cells and blood vessels. Allantois  Definition: Diverticulum from caudal end of yolk sac extends into connecting stalk  Fate: 1. Proximal part of allantois: share in formation of urinary bladder. 2. Distal part of allantois: form the urachus; After birth, urachus becomes fibrous band and form median umbilical ligament which extend from apex of urinary to umbilicus. Allantois Anomalies 1. Urachal fistula  Cause: failure of obliteration of whole urachus.  Feature: communication between urinary bladder and umbilicus. 2. Urachal cyst: Persistent of the middle part of urachus 3. Urachal sinus: Persistent of the distal part of urachus. 2 3 1  Case scenario A newborn baby presents with fluid draining from the umbilicus onto the skin. Testing of the fluid identifies it as urine. What is the most likely diagnosis? A. Urachal cyst. B. Urachal fistula. C. Urachal sinus D. Urachal diverticulum E. Bifid ureter. For more details, please read  Larsen’s human embryology (from P. 47)  Langman's Medical Embryology,