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 development of the heart and veins associated with the embryonic heart begins with angioblastic cords that appear and are thin heart tubes. And as the lateral embryonic fold occurs, eventually these cords come together to form a single heart tube which are the endocardial heart tubes. The heart starts beating at 22 to 23 days and then blood begins to flow throughout the embryo during the fourth week. There are three type of veins that drain into the tubular heart of a embryo at 4-weeks: vitelline veins (return poorly oxygenated blood from the umbilical vesicle (yolk sac)), umbilical veins (carry well-oxygenated blood from the chorionic sac), and common cardinal veins (return poorly oxygenated blood from the body of the embryo).
4. Define the inferior vena cava and its function. -The inferior vena cava is formed during a series of changes when the primordial veins receives blood from the rest of the embryo and shifts from left to right side of the body. This vein becomes the receiver of all the veins throughout the body that flows into the heart. The IVC is connected at the ductus venosus, which is a shunt that bypasses the liver from the chronic sac through the umbilical vein. IVC is made up of four main segments: hepatic segment (from the liver), prerenal segment (from “in front” of the kidneys), renal segment (from the kidneys), postrenal segment (from “below” the kidneys). These veins are carry deoxygenated blood from the lower parts of the body through the inferior vena cava to the heart.
5. Define the superior vena cava and its function. -The superior vena cava is formed from the right anterior cardinal vein and the right common cardinal vein which then flows in the inferior vena cava. Superior vena cava is a vein that carries deoxygenated blood from the head, arms, and upper body to the heart.
6. Explain the anatomy and development of the fetal heart. -The development of the fetal heart begins as the endothelial tubes come together to create one tube, which is the fetal heart, there develops an internal endothelial lining of the heart called endocardium and the primordial myocardium become the muscular wall of the heart called myocardium. On one end of the enlarging fetal heart, is the sinus venosus that receives the umbilical, vitelline, and common cardinal veins that flow from the chorion, umbilical vesicle, and embryo. The other end of the fetal heart “tube” is the pharyngeal arches that supply the pharyngeal arch arteries that arise form the aortic sac and terminate in the dorsal aortae. At about 23 to 28 days, the tubular heart undergoes a dextral (right-handed) looping and forms a U-shape D-loop with the apex pointing to the left.
7. Explain tetralogy of fallot. -Tetralogy of fallot are the classic group of four cardiac defect. These defects are pulmonary artery stenosis (obstruction of right ventricular outflow), VSD (ventricular septal defect), dextroposition of aorta (overriding or straddling aorta), and right ventricular hypertrophy. With tetralogy, the pulmonary trunk is usually small and there are signs of deficient oxygenation of blood called cyanosis. This can be a result of when division of the TA(truncus arteriosus) is unequal and the pulmonary trunk is narrow.
8. Explain the fetal and neonatal circulation. -The fetal and neonatal circulation is possible by the fetal cardiovascular system that is designed to serve prenatal needs and permit modifications at birth that establish the neonatal circulatory pattern. Before the lungs take their responsibility of oxygenating the red blood cells, the placenta has this responsibility first. With the fetal circulation, highly oxygenated, nutrient-rich blood gets perfused from the placenta through the umbilical vein. As this blood approaches the liver, about ½ by-passes through the ductus venosus(DV) to the inferior vena cava and the other ½ goes through the liver and reaches the IVC through the hepatic veins. In the IVC is where well oxygenated blood mixes with poor oxygenated blood from the lower part of the body. This blood then enters the right atrium of the heart and mixes with the small amount of poor oxygenated blood from the lungs back to the lungs being medium oxygenated through the pulmonary veins. Then out of the left atrium, the blood leaves through the ascending aorta, where well-oxygenated blood goes to the heart, neck, head, and upper limbs. Neonatal circulation does not use the placenta but the lungs are functioning and transform low oxygenated blood into high oxygenated blood. This means that blood does not bypass the liver, but now all the lower half of the body’s blood circulates up through the liver into the right atrium and out the pulmonary trunk to the lungs. In the lungs, the blood becomes oxygenated, goes out through the pulmonary veins into the left atrium and out the arch of aorta which high oxygenated blood flows to the head arms and then back down to the right of the body through the descending aorta.
9. Explain transitional neonatal circulation. - Transitional neonatal circulation occurs when the fetal blood through the placenta ceases and the infant’s lungs expand and begin to function. In this transition, the oval foramen(that separates the right atrium of the heart and the left atrium), DV, ductus arteriosus(DA), and umbilical vessels are no longer needed. Also, since the left atrium increases with pressure from the well oxygenated blood from the lungs, the oval foramen is pressed, closing it and only blood from right is into the pulmonary trunk. By 96 hours after birth, the DA is fully closed. And the umbilical arteries constrict at birth so the infant does not loose blood. However, the umbilical vein continues to transfer well-oxygenated fetal blood from the placenta to the infant until there is no more blood or its cut off. The change from fetal to the neonatal circulation is not a sudden occurrence but different changes occur from the first breath, to the first couple hours, to the first couple of days.
10. What is associated with aeration of the lungs? -Aeration of the lungs is associated with dramatic decrease in pulmonary vascular resistance, marked increase in pulmonary blood flow, and progressive thinning of the walls of the pulmonary arteries.
11. Explain the development of the lymphatic system. -The lymphatic system develops at the end of the sixth week, about 2 weeks after the primordia of the cardiovascular system begins. Lymphatic vessels develop in a manner similar to how blood vessels are developed; they make connections with the venous system. The early lymphatic capillaries join each other to form a network of lymphatics. There are six primary lymph sacs that present themselves at the end of the embryonic period: two jugular lymph sacs (at the neck), two iliac lymph sacs (near the bottom), one retroperitoneal lymph sac (posterior abdominal wall), and one cisterna chyli (opposite to the retroperitoneal lymph sac). These lymphatic vessels then connect between the sacs throughout the body.
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
NOTES Ultrasound is out of the human’s hearing of 20 Hz to 20,000 Hz.
Transducer up against the skin, sends a pulse through the skin, and travels towards whatever is behind the skin and once there is an interface, some pulse is sent back to the transducer, and the other pulse continues till another interface and another interface. -Pulse is sent, and portions of the pulse is sent back when interfaced with an edge of an object. To use ultrasound, high frequency, low wavelength = less diffraction (clearer image)
Video 2 talks about an ultrasound of a baby in the womb
Heart tracing: zoom in and this gets heart beats per minute, and see how the heart is beating
You can see: spin, brain anatomy, abdominal anatomy, legs, thighs, rounded bum, hands, arms, umbilical cord
Common measurements Crown-rump measurement : length and helps with dating – but can only do before 13 weeks Side-to-side measurement & Circumference Abdominal circumference around the waist Thigh-to-knee bone (femur) Report page See if measurements are concordance with dates See if measurements are concordance with one another.
OB ultrasound Evaluates baby’s environment Other soft tissues like your cervix and bladder Liquid around the baby Baby’s movements
All Sound waves travel through liquid best, and this gets best picture All fluid on the screen is black
OB ultrasound takes pictures for mother Early ultrasounds give the most accurate dates, predicting due date best. Gender is found at about 20 weeks 20 weeks they do a screening ultrasound, that’s more in depth and takes about 40 minutes and they look at baby head to toe.
Ultrasound are sound waves that are higher then what the human ear can hear. These sounds waves are higher then 20,000 Hz, with a high frequency and have low wave lengths. This allows for less diffraction and creates a more accurate picture as the sound waves return back to the transducer. The accurate pictures are needed for diagnosing anything that is abnormal in the abdominal and accuracy is need for looking at early developments of a fetus.
During an obstetrical ultrasound, this accuracy of the sound waves, helps to take measurements of the baby to determine the baby’s age in the womb and an estimated due date.
Measurements also are compared with one another to see if there are any development issues going on. This means the ultrasound can see the arms, hands, feet, legs, and rounded bum. The measurements that are taken are crown-rump (which is the length but needed to be taken before thirteen weeks), side-to-side with circumference, abdominal circumference, and thigh-to-knee bone, also known as the femur measurement.
An ultrasound sound can also see the heart movements, the spine, brain anatomy, abdominal anatomy, and the umbilical cord. Viewing all these details allows the obstetrician to see what the baby’s environment looks like and any see if there are any visible issues. Even though so much details are viewed during the ultrasound, gender is not quite noticeable until about 20 weeks. With viewing the heart, a heart tracing is done where they zoom in on the screen and get a number of how many beats per minute. The last few things that are evaluated during an ultrasound is viewing other soft tissues like the cervix and bladder, the liquid that surrounds the baby, and the baby’s movements.