Embryology Student Past Paper 2024 - BMD

Embryology Dr Ian Jenkins  Learning objectives To be able to identify the key stages of development from fertilisation to implantation To be familiar with the processes of gastrulation and the transition from a bilaminar embryo to a trilaminar embryo To be able to id...

Embryology Dr Ian Jenkins  Learning objectives To be able to identify the key stages of development from fertilisation to implantation To be familiar with the processes of gastrulation and the transition from a bilaminar embryo to a trilaminar embryo To be able to identify from which of the 3 cell populations (endoderm, mesoderm and ectoderm) is each major organ derived To understand the basic processes of neurulation To be able to explain how the process of heart development can lead to common heart defects In the beginning: ovulation In the beginning: fertilisation In the beginning: fertilisation In the beginning: rapid cell division 2-cell stage Morula In the beginning: blastocyst In the beginning…week 1  Abdomina l Interstitia Ampullar l y Isthmus Infundibu lar Ovarian Ectopic pregnan Cervical cy Week 2: 2 layers (bilaminar disc) Trophoblast Inner cell mass Week 2: 2 layers Week 2: 2 layers Week 3: 3 layers  3 Germ Layers: Gastrulation Mesoderm: bones, connective tissue, skeletal muscle, urogenital system, cardiovascular system Ectoderm: Skin, CNS, PNS, eyes, internal ear Endoderm: gut and associated derived tissues (liver, pancreas etc and lungs).  Neurulation ectoderm Neural plate Neural tube Neurulation  Neurulation Anterior Day 22 neuropore, closes at 24 days Posterior neuropore, closes at 28 days Failure of posterior neuropore to close Spina bifida Failure of anterior neuropore to close  Brain (https://www.coursehero.com/tutors-problems/Psychology/31127772-Explain-structure-and-functions-of-Forebrain-Midbrain-and-Hindbrain-/) BREAK 1 The heart  Heart is one of earliest differentiating and functioning organs Develops from cardiogenic mesoderm (lateral plate), originally lying above cranial end of developing neural tube Blood islands - haemangioblasts & myoblasts Haemangioblasts - endocardial heart tube angiogenic lateral folding of cell clusters embryo results in coalesce fusing of paired forming right endocardial tubes and left into primitive heart endocardial tube. tubes  Lateral folding Cardiogenic mesoderm Endocardial tubes Heart tube 21 days Proximal aorta and Truncus arteriosus pulmonary artery Ventricular outflow Bulbus cordis tracts and Right Ventricle Blood flow Primitive ventricle Left ventricle Primitive atria Left and right atria Sinus venosus smooth part of righ atrium and coronar sinus As the primitive heart tube continues to elongate it is limited in length by the pericardium. So the tube begins to fold within the pericardium, which places the chambers and major vessels into an alignment similar to the adult heart. This process 35 days Truncus arteriosus Proximal aorta and pulmonary artery Primitive atria Left and right atria Bulbus cordis Ventricular outflow tracts and Right Ventricle Primitive vent Left ventricle Sinus venosus smooth part of right atrium (sinus venarum) and coronary sinus  Truncus arteriosus Proximal aorta and pulmonary artery Primitive atria Left and right atria Bulbus cordis Ventricular outflow tracts and Right Ventricle Primitive ventricle Left ventricle The heart has 2 chambers, a ventricle Sinus venosus and an atria. These smooth part of right atrium (sinus chambers are venarum) and coronary sinus Septum formation in the atrio-ventricular canal On about 28 days (end of 4th week), two swellings of mesenchymal tissue appear from walls of the canal - endocardial cushions The endocardial cushions grow and fuse together to divide canal into R & L BREAK 2  ATRIUM ATRIUM Endocardial cushion VENTRICLE VENTRICLE  Ostium Septu secundum m Primu m Ostium primum  Ostium Septu secundum m Primu m  Ostium Septum secundum Secundu m Forame n ovale Foramen ovale Foetal circulation Ductus venosus - shunts blood from umbilical vein to IVC (bypassing liver) Foramen ovale - shunts blood from RA to LA (bypassing pulmonary circulation) Ductus arteriosus – shunts blood from pulmonary trunk to ascending aorta (bypassing lungs) Foetal circulation Ductus venosus - fibroses to form ligamentum venosus Foramen ovale - closes because of increased pressure in LA (compared to RA) to form fossa ovalis Ductus arteriosus – Ligament fibroses to form um teres ligamentum arteriosum Medial umbilical ligaments  Right atrium Left atrium Right atrium Left atrium Higher pressure Lower pressure Lower pressure Higher pressure (pulmonary resistance) Probe patent foramen ovale In up to 25% of people a probe can be passed from one atrium to the other. Defect usually small and is not significant.  Atrial Septal Defects ASD incidence 7:10,000 births 2:1 prevalence in females versus males Septum primum and septum secundum defects This large ASD with left-to-right shunt resulted in pulmonary hypertension and increased pulmonary arterial pressures that led to right-to-left shunt, resulting in right ventricle Ventricular septation  End of 4th week a muscular IVS develops from floor of primordial ventricle Grows towards Membranou membranous IVS s which develops from component endocardial cushions Muscular component  Ventricular Septal Defect VSDs are most common type of cardiac defect accounting for 25% of congenital heart defects. Many small VSD will close spontaneously (30-50%). Isolated VSD are detected with an incidence of 10-12:10,000. About 90% of VSD are in membranous septum and 10% in muscular septum.  This is a VSD in the membranous portion of the ventricular septum. Gut tube development Ectoderm: Skin, CNS, PNS, eyes, internal ear Mesoderm: bones, connective tissue, skeletal muscle, urogenital system, cardiovascular system Endoderm: gut and associated derived tissues (liver, pancreas etc and lungs). Gut tube development - 3 distinct parts Foregut Stomach, 1st part duodenum, liver, pancreas, spleen COELIAC TRUNK Midgut Caudal duodenum, small and large intestine up to splenic flexure SUPERIOR MESENTERIC ARTERY Hindgut Splenic flexure, descending, sigmoid colon, rectum, upper anal canal INFERIOR MESENTERIC ARTERY  Gut tube development The midgut rapidly elongates and begins to herniate out ethe abdominal cavity into the umbilical cord. It then rotates twice. The abdominal cavity increases in size and the gut tube moves back into the abdominal cavity.  The End. Thank you for your attention And ‘Goodbye’ (Almost)..