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Part 1 Read pages 289 – 362 (Chapter 13 through Chapter 14) in The Developing Human For all fill in the blank questions you only need to provide the missing word or phrase. For all other questions including definitions please ensure you write in complete sentences using appropriate grammar. A question will be deemed to have been answered when the question has been restated in your answer along with all pertinent information. Ensure you do not miss any information in multi-part questions. Simply listing facts is less important than explaining the information so that we can be sure you fully grasp the content. 1. What is the first major system to function in the embryo? The first major system to function in the embryo is the cardiovascular system. 2. When do the primordial heart and vascular system appear? The primordial heart and vascular system appear in the middle of the third week. 3. Briefly explain the development of the heart and veins associated with the embryonic Heart.. The appearance of endothelial strands called angioblastic cords, in the 3rd week is the first appearance of the heart developing. These strands will go to form two thin tubes which will eventually form into one heart tube. The heart will begin to beat at 22-23 days and blood will begin to flow in the fourth week.Around 4 weeks, there are 3 paired veins that drain into the tubular heart.The veins in the heart are: Vitelline veins- This vein returns poorly oxygenated blood from the yolk sac. Umbilical veins- Carries well oxygenated blood from the primordial placenta. Cardinal veins- Returns poorly oxygenated blood from the body of the embryo. 4. Define the inferior vena cava and its function. The inferior vena cava is a large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart to oxygenate.Its is formed by the joining of the right and left iliac veins. 5. Define the superior vena cava and its function. The superior vena cava is a major vein in the upper body.This is very important for the function of the cardiovascular system. The superior vena cava carries blood from the head, neck,arms and chest. 6. Explain the anatomy and development of the fetal heart. The fetal heart is developed from splanchnic mesoderm. The heart is composed of a thin endothelial tube,separated from a cardiac jelly a thick myocardium. The primordial myocardium becomes the myocardium muscle part of the heart. As the heart elongates it forms into the pericardial cavity. The bulbus cordis which is composed of the( truncus arteriosus, conus and conus cordis,), the ventricle, atrium, and sinus venous. These four structures are what makes up the four chambers of the heart. Around 23-28 days the tubular heart undergoes a dextral looping. This forms a u-shaped d'loop that results in a heart with apex pointing to the left. As the primordial heart bends, the atrium and sinus venosus come to lie dorsal to the TA,bulbus cordis and the ventricle.At this time the sinus venosus has developed lateral expansions, the right and left sinus horns. As the heart elongates and bends it will gradually invaginate into the pericardial cavity. The heart will be initially suspended from the dorsal wall by a mesentery, the dorsal mesocardium. As the central part of the mesentery degenerates it forms a communication, the transverse pericardial sinus. The heart is now attached only at its cranial and caudal ends. 7. Explain tetralogy of fallot. Tetralogy of fallot is a cardiac defect.There are four defect: - Pulmonary artery stenosis(obstruction of the right ventricular outflow) This is the narrowing of the pulmonary valve, which flows oxygen poor blood into the pulmonary artery and from there the blood travels to the lungs to pick up oxygen.Pulmonary stenosis is where the pulmonary valve can not open fully, which causes the heart to work harder and results in a lack of blood reaching the lung. - VSD ( Ventricular septal defect) A ventricular septal defect is a hole in the septum that causes oxygen rich blood ( left ventricle) and oxygen poor blood (right ventricle) to mix. - Dextroposition of aorta. In a normal heart,the aorta is attached to the left ventricle and allows oxygen rich blood to flow throughout the body.In tetralogy of fallot heart the aorta is located between both the left and right ventricle. This causes oxygen poor blood from the right ventricle to flow into the aorta instead of the pulmonary artery. - Right ventricular hypertrophy. This is when the muscle of the right ventricle is thicker due to the right side of the heart receiving excessive blood flow from the left side of the heart. 8. Explain the fetal and neonatal circulation. The blood flow in the fetus follows this pathway: Oxygen and nutrients from the mother’s blood are transferred across the placenta to the fetus through the umbilical cord. This enriched blood flows through the umbilical vein to the fetuses liver.There it moves through a shunt called the ductus venosus. The blood is directed through the oval foramen in the left ventricle atrium and there it mixes with blood from the heart. The blood then travels from the left atrium to the left ventricle and out through the aorta. Then it travels through the arteries in the head,neck and upper limbs then to the descending aorta.From there it travels to the umbilical arteries and back to the placenta for reoxygenation. 9. Explain transitional neonatal circulation. Important adjustments occur at birth when the circulation of the fetal blood through the placenta stops and the infant's lungs begins to function.Soon as the baby is born, the oval foramen,da,dv and umbilical vessels are no longer needed. The transition from the fetal to neonatal circulation includes, elimination of the placental circulation,lung expansion and increase in lung blood flow so that the entire cardiac output can be used and the closure of the foramen ovale, ductus arteriosus and ductus venosus can occur. 10. What is associated with aeration of the lungs? At birth, the newborn needs to clear liquid out quickly to allow air entry and the onset of pulmonary gas exchange to begin. It also triggers the increase in pulmonary blood flow at birth.Lung aeration is the big event for the successful transition to newborn life. 11. Explain the development of the lymphatic system. The lymphatic system begins to develop at the end of the 6th week. Lymphatic vessels develop in a similar way as blood vessels and make connections with the venous system. Early lymphatic capillaries join each other to form a network of lymphatics. There is a lot that develops in the lymphatic system. -Development of lymph sacs and lymphatic ducts. There are six primary lymph sacs present at the end of the embryonic period. *Two jugular lymph sacs *Two iliac lymph sacs *one retroperitoneal lymph sac *Cisterna chyli Soon lymphatic vessels connect to the lymph sacs. -Development of the thoracic duct - Development of the lymph nodes -Development of lymphocytes -Development of the spleen and tonsils Part 2 For this assignment you will become familiar with ultrasounds. They are a tool often used in fetal development and it can be confusing to know exactly how they work, even if you have been pregnant and had ultrasounds yourself. Watch these two films and take notes. You will be learning the specifics of ultrasound generally and then obstetrically. Once you have your information from the two videos you can write a 2-3 paragraph synopsis of what you learned. Video 1 Video 2 .
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