Implantation Embryology Lecture 3 PDF

Cleavage & Implantation Anatomy Unit201 Anatomy Unit  Objectives By the end of this lecture , the student should be able to: 1. Define the term “implantation’. 2. Describe the cleavage and the stage at which implantation occurs. 3. Explain the process of...

Cleavage & Implantation Anatomy Unit201 Anatomy Unit  Objectives By the end of this lecture , the student should be able to: 1. Define the term “implantation’. 2. Describe the cleavage and the stage at which implantation occurs. 3. Explain the process of blastocyst formation. 4. Describe the process of ‘implantation’. 5. Define the normal site of implantation. 6. Describe the abnormal sites of implantation (ectopic pregnancy). 7. Describe decidua and its types  Case scenario Q. A 20-year-old woman presents at the emergency department with severe abdominal pain on the right side with signs of internal bleeding. She indicated that she has been sexually active without contraception and missed her last menstrual period. Based on this information, which of the following disorders must be included as an option in the diagnosis? (A) Ovarian cancer (B) Appendicitis (C) Normal pregnancy (D) Ectopic tubal pregnancy  Implantation Definition: Penetration of the blastocyst into the superficial layer of the endometrium. The endometrium after implantation is called decidua. Time: 7th day after fertilization and is completed at 11th day.  Implantation Normal site of implantation In the endometrium of the uterus (upper part of the posterior wall of the body near the fundus).  Implantation Blastocyst attaches to the endometrial epithelium (at embryonic pole). Degeneration off the zona pellucida. Enlargement of the blastocyst. Exposure of the trophoblast and differentiated into two layers; o Syncytiotrophoblast (outer mass) o Inner cellular cytotroblast (day7).  Implantation The exposed trophoblast has two functions: Adhesive power: the blastocyst adheres to endometrial epithelium and invade it by its finger like processes. Histolytic power: o Syncytiotrophoblast produce lysis of endometrial tissues (releasing proteolytic enzymes) o formation of a defect in the endometrium. o The blastocyst is gradually embedded in the endometrium.  Implantation The blastocyst gradually embed deeper in the endometrium.  The defect in the endometrial epithelium is filled by fibrin plug (day 10).  Implantation The defect gradually disappear Blood filled lacunae appear in as the endometrial epithelium is Syncytiotrophoblast )filled with repaired (day 12 & 13) maternal blood(.  Abnormal sites of implantation A)Inside the uterus (Placenta praevia): Def: Implantation of a blastocyst in the inferior segment of the uterus nears the internal os (the placenta proceed the fetus during delivery).  Abnormal sites of implantation Types of placenta previa: 1) Placenta praevia lateralis: the placenta away from internal os of cervix. 2) Placenta praevia centeralis: the placenta completely covers the internal os of cervix. 3) Placenta praevia marginalis: the placenta partially covers the internal os.  Abnormal sites of implantation( B) Outside the uterus )ectopic pregnancies( Types 1-Fallopian tube (causes-features) 2- Ovary(causes) 3- Abdomen (peritoneal) Cause ? ? ? ?  The decidua Def: It is the endometrium of the pregnant uterus. Parts: 1) The decidua basalis: Is the part of the endometrium, which lies between the fetus and the muscle wall of the uterus. 2) The decidua capsularis: Is the part of the endometrium which overs the fetus. 3) The decidua parietalis: Is the part of the endometrium, which lines the rest of the uterine cavity  The decidua Fate: 1) The decidua basalis: form the maternal part of the placenta. 2) The decidua capsularis and parietalis: During the 12th week, fused due to the growth of the embryo. By 22-24 weeks: degenerate and disappear by pressure of growing embryo which decrease blood supply to the decidua capsularis  Case scenario  Q. A 20-year-old woman presents at the emergency department with severe abdominal pain on the right side with signs of internal bleeding. She indicated that she has been sexually active without contraception and missed her last menstrual period. Based on this information, which of the following disorders must be included as an option in the diagnosis? (A) Ovarian cancer (B) Appendicitis (C) Normal pregnancy (D) Ectopic tubal pregnancy  Ectopic pregnancy Causes Signs Symptoms Treatment Langman medical embryology