The Circulatory System

I received a call last week from a client who wanted to know which side of the neck contained the carotid artery and which side contained the jugular vein. I was a bit shocked at first but after giving it some thought I have realized that, although my clients are highly educated, their expertise is in a completely different area. Some things that I consider common knowledge may be completely unknown to those who missed it in high school biology class and haven’t come across it since. Therefore, I think it might be helpful for me to offer a basic primer on some of the major anatomy and physiology concepts in these blog posts I write each month. Today, in honor of that client who was trying to find the carotid artery, I’ll cover the basics of the circulatory system.

The circulator system (cardiovascular system) is easiest to understand if you divide the structures into three groups: 1) the heart, 2) the great vessels, and 3) the peripheral vessels. But overall, we must first understand that the circulatory system is a transportation system like a series of highways and smaller rural roads that act together to provide oxygen and nutrients to the various tissues of the body and to carry away waste materials and toxins. I will use this transportation and roads analogy extensively throughout this primer. I use this analogy rather than a similar analogy based on rivers or house plumbing because roads allow traffic in both directions. Arteries, which carry blood from the heart out to the body, and veins, which carry blood from the body back to the heart, often run together side-by-side, just like the north and southbound lanes of traffic on a highway.

The heart is a fist sized muscular organ that pumps the blood throughout the circulatory system. The heart is divided into four hollow chambers, two on the right and two on the left. The two upper chambers of the heart are called atria (singular, atrium). The two lower chambers are called ventricles (singular, ventricle). All blood enters the heart through the atria. The deoxygenated blood carrying waste carbon dioxide enters the right atrium through the superior vena cava and inferior vena cava, the largest veins of the body. Freshly oxygenated blood arrives into the left atrium from the lungs via the pulmonary veins. These atria are relatively thin walled without much muscle and their only task is to pump the blood that they receive from the veins down into the ventricles below. The ventricles are responsible for the major pumping action of the blood and therefore have much thicker muscular walls. The right ventricle pumps blood out to the lungs via the pulmonary arteries where the blood can release the built up waste carbon dioxide and take on the all-important oxygen in a process called gas exchange. The left ventricle pumps blood out through the aorta that, through the variety of branches and divisions we will describe below, will reach all regions of the body from the top of the head down to the bottom of the feet.

The great vessels are the major arteries and veins that connect directly to the heart. Each of the great vessels is unique so some memorization is required but there are only a few so we should be able to cover them quickly. Let’s start with the arteries. As I mentioned above, arteries carry blood away from the heart. The aorta is the largest artery in the body since it is the major highway for blood flowing to all regions of the body. It is easily recognized because it arises from the top of the heart, forms a large loop (the aortic arch), and courses down behind the heart and down through the midline of the chest and abdomen. The aortic arch has three large branches in the upper chest; the brachiocephalic artery, the left common carotid artery and the left subclavian artery. The brachiocephalic, which courses upward and to the right soon divides into the right subclavian artery and right common carotid artery. As the aorta courses down through the back of the abdomen, it has a number of branches that vascularize the abdominal organs and spine. Low in the abdomen the aorta divides (bifurcates) into the left and right iliac arteries that course down through the pelvis and into the legs. Another artery that arises from the top of the heart is the pulmonary trunk that bifurcates into right and left pulmonary arteries that send blood out to the lungs. This division of the pulmonary trunk forms a capital T shape and lies just beneath the aortic arch. The great veins include the superior vena cava, inferior vena cava and the pulmonary veins. All blood returning to the heart from the arms, upper torso, head and neck enter the superior vena cava from the right and left jugular veins and the right and left subclavian veins via the right and left brachiocephalic veins. The blood returning from the lower body enters the inferior vena cava that runs alongside the distal aorta in the back of the abdomen. Four separate pulmonary veins provide blood flow from the lungs into the posterior aspect of the left atrium.

The peripheral vessels are a bit easier to recognize and remember because many of the peripheral arteries and veins have an adjacent course (like north and southbound traffic) and have identical names. This is true for the iliac, femoral and popliteal arteries and veins in the legs, the subclavian, brachial, radial and ulnar arteries and veins in the arms and the carotid arteries and jugular veins in the neck. What confuses many is the fact that many of these different vessels are actually just the same continuous structure that has different names depending on the location. Think of a street that changes names for no apparent reason when you go through an intersection. The subclavian artery becomes the brachial artery when it passes from the chest into the upper arm and then becomes the ulnar artery after the radial artery branches off in the elbow region. Also it is good to remember that, except for the vessels of the chest and abdomen, all vessels are symmetrical with the exact same structure in each arm, each leg and on each side of the head and neck.

As with the skeleton and the various muscles, the circulatory system can be intimidating simply because of the vast number of structures and multiple names for each. The good thing is that few need to remember each and every structure to understand the system as a whole. You can always refer back to illustrations and diagrams to find the exact location or name of each vessel, but it is good to retain a working knowledge of how the blood is pumped by the heart, taken out to the body via the arteries and returned to the heart via the veins.

Infections During Pregnancy

Several years ago, when my wife was pregnant with our son, I contracted a human parvovirus. Having assisted on a few cases involving gestational infections, I was quite concerned and sought treatment immediately. We also notified my wife’s obstetrician and took steps to avoid transmission of the virus to her and the developing child. Thankfully, our doctors took this situation seriously and followed us closely to be sure that there was no risk to the pregnancy. Pregnancy often leaves the mother with a weakened immune system. Infections can be a great risk to the fetus. Therefore it is an important responsibility of the obstetrician to avoid and treat infections in a timely manner.

I have participated in a variety of medical malpractice cases involving maternal infections that were not adequately treated and therefore allowed to infect the child, either in the womb or during delivery. In those cases, I have seen that there are three basic ways that the baby may become infected. 1) Congenital infections are infections that pass from the mother to the child across the placenta while the baby is womb. 2) Perinatal infections are infections of the birth canal that spread to the child during labor or delivery. These infections may cross the fetal membranes or invade after the membranes are broken to infect the baby in the womb, or infect the baby as it passes through an infected vaginal canal during delivery. 3) Postnatal infections spread to the baby after delivery, primarily through the mother’s breast milk.

Congenital infections can be caused by protozoan parasites as in toxoplasmosis, bacteria as in syphilis, or by a variety of viruses such as rubella, cytomegalovirus, herpes or human parvovirus. Each different microbe is a risk to the developing fetus at different stages of development. Some may interfere with development leading to deformities or developmental abnormalities. Others may lead to fetal death and miscarriage. It is important that the mother be monitored for infections throughout the pregnancy and that any infection be treated promptly.

Perinatal infections are caused by bacteria such as strep or viruses such as herpes or the human papilloma virus that may be present in the vagina during labor or delivery. These infections include many sexually transmitted diseases that can infect the baby during delivery. Another risk comes from fecal material that may contaminate the birth canal during labor. As mentioned above, some of these infections may cross the fetal membranes and infect the fetus in utero. Others may move into the womb after the membranes are disrupted (water breaks). Certainly the fetus is exposed to any infections within the vagina during the process of delivery as the baby passes through the birth canal. Once again, it is the responsibility of the obstetrician to recognize and treat any vaginal infections prior to delivery to avoid this contamination.

Postnatal infections involve many of the same bacteria or viruses mentioned above and can pass from the mother to the child through the breast milk. These infections can be easily avoided if the mother has been properly diagnosed and breast-feeding is delayed until after treatment is complete.

In each case of fetal infection that I’ve worked on over the years the issue being litigated is either the failure to diagnose a maternal infection or a failure to treat the infection or take steps to prevent contagion. If, in future cases, you encounter issues of fetal deformity or fetal demise, it would benefit you to do a thorough examination of the medical records to see if there is any evidence of infections that existed in the mother that may have contributed to the outcome of the pregnancy.

Intramedullary Fixation

I'll never forget the first orthopedic surgery I observed while at medical school training for my medical illustration degree. I was shocked at the crude brutality of the procedure with all the hammering, sawing, drilling and reaming. It seemed more like carpentry than what I had envisioned as modern medicine. If nothing else, orthopedic surgery is certainly dramatic and perhaps this inherent drama is what makes it such a popular subject for demonstrative evidence. Because of that popularity, I have selected one orthopedic issue as our topic for the month. Let's learn a bit about intramedullary fixation.

We'll begin with the basics. When a bone is broken, the body has a remarkable ability to repair itself by producing new bone to knit the fracture back into a solid structure. This can only occur successfully if the fractured edges of bone are in contact with one another and if the fracture site is immobilized during the healing process. That is the primary goal of the orthopedist when dealing with a fracture: to align and stabilize the fracture site. In many instances, this alignment and stabilization can be done without surgery. Non-displaced fractures can be stabilized in a splint or cast. Some displaced fractures can be realigned externally before stabilization. More complex or severe fractures must be aligned surgically and held in position with fixation hardware to provide the stabilization required for healing.A variety of fixation techniques and types of fixation hardware have been developed over centuries. Orthopedic surgeons may use wires, staples, plates, screws or rods to hold fractures in position as they heal. One of the most popular techniques for fixation of large long bone (extremities) fractures is the insertion of an intramedullary rod inside the length of the bone. Long bones in the arms, legs, feet and hands consist of a hard compact outer layer that forms a tube surrounding a hollow chamber called the medullary cavity containing the bone marrow. This hollow chamber is ideal for the placement of a fixation rod allowing for the stabilization of the entire length of the bone.

The surgical technique for intramedullary fixation includes the access of the end of the broken bone through a small open incision. A hole is created through the hard outer compact bone to expose the medullary canal. A guidewire is inserted down the length of the bone to insure alignment and to identify the medullary canal. A drill-like reamer is advanced over the guidewire to clear the marrow and open a pathway for the fixation rod. Finally, the rod itself is hammered into position. Locking screws may be placed at either end of the rod to hold the rod in position. This fixation rod may be left in position permanently or may be removed at a later date following the full healing of the fracture.

Beyond the great stability offered by intramedullary fixation, there are other advantages to utilizing this technique. Intramedullary fixation can be accomplished with a much smaller incision than the large open incision required for the placement of fixation plates across the external aspect of the fracture. This reduces post-operative pain and recovery time and also involves lower risk of damage to vessels and nerves that may lie in the region of the fracture. Also, because the open incision is not at the actual site of the fracture, there is no additional disruption and risk of infection that would prevent bone healing.

Larger bones are more commonly treated with intramedullary fixation. This includes the femur (thigh), the tibia (shin) and the humerus (upper arm). Smaller bones such as the fibula (smaller lower leg bone), metacarpals (hand), metatarsals (foot), phalanges (fingers and toes) and even the clavicle (collar bone) can be fixated with smaller intramedullary rods or pins, but this is less common than the use of small plates and screws. Another term you may run across is "retrograde". Retrograde fixation means that the rod is placed through the distal end of the bone extending upward rather than into the proximal end and extending downward.

If you handle any personal injury cases in your practice, you'll eventually run across a case involving an intramedullary fixation. Hopefully this overview has helped you to better understand these dramatic orthopedic procedures.

Stations of Presentation

In the past few weeks I have had calls from three attorneys with traumatic birth injury cases. Each one needed last minute help with demonstrative evidence to illustrate the basics of labor and delivery. They had all waited to the last minute, thinking they didn’t need anything very specific and that they could get something very quickly. Unfortunately, each of these clients was unable to answer one vital question about their case, which forced them to rush back to their experts for more information and nearly prevented them from acquiring their exhibits in time. The vital question they could not answer was, “What system of classification was used in this case to notate the station of presentation?”
If you’ve ever taken part in any litigation regarding labor and delivery, certainly you’re familiar with stations of presentation. Basically, this system allows the healthcare provider to record the progress the baby makes down through the birth canal during the process of labor. It is vital to chart this progress because any deviation from the normal range can give vital clues that there is a problem that might require action. Delays in fetal progress down the birth canal during labor could be a sign of a variety of problems including an insufficient size of the mother’s pelvis, inadequate contractions, shoulder dystocia or other serious complications. The records regarding this progression may be the only evidence of what was happening during labor in a case that eventually results in litigation, so the records of the fetal stations is vital. There are two separate systems in use out there and to get an accurate picture of what occurred, you must know what system was in use.


Fetal station refers to the level of the leading edge of the fetus within the birth canal (either the head in a vertex presentation, or the foot or buttocks in a breech presentation). This level is measured in relation to the location of small protrusions of the pelvis of the mother called ischial spines. The station refers to how far above or below the ischial spines the fetus has progressed. Unfortunately, there are two distinct systems for determining fetal station in use. We’ll refer to these two systems as the “thirds” system and the “fifths” system.


Traditionally, the thirds system of measuring the station of presentation was the standard. In this system the level of the birth canal level with the ischial spines is referred to as 0 station. Above the 0 station, the distance from the pelvic inlet at the top of the pelvis down to the ischial spines is divided into thirds and referred to as -3, -2 and -1 from top to bottom. Below the 0 station, the distance from the ischial spines down to the pelvic outlet where the baby emerges from the birth canal is also divided into thirds and referred to as +1, +2 and +3 as the baby progresses. So, you take the total distance between these landmarks and divide the distance into thirds.

In 1988, the American College of Obstetricians and Gynecologists began to change the system and divide these spaces into fifths. In the fifths system, the ischial spines still represent the 0 station, but the new system refers to the stations as -5, -4, -3, -2, -1, 0, +1, +2, +3, +4 and +5. More importantly, these stations are no longer just arbitrary divisions of the total space. In the fifths system each station is divided by 1 cm, so an actual measurement can be taken to more accurately determine the station, depending on how many centimeters above or below the ischial spines the leading edge has reached.


Although 0 station is the same in the thirds and fifths system, none of the other stations coincide, so it is important to know what system was used. Regretfully, no consistency is seen in the world of obstetrics and it depends on where and when the obstetrician was trained, as well as the standards of the hospital where the delivery is performed. Early in your research and discovery phase of the case, you must determine which system was in use in order to properly understand the stations that are recorded in the records. Certainly, if the time comes for you to depict the events of the case accurately in demonstrative evidence you must be sure that the illustrations you use reflect the proper system.

VBAC and Uterine Rupture

Of all the issues we regularly see in OB/GYN medical malpractice cases, those involving uterine rupture are often the most devastating. The rupture of the uterus during pregnancy or during delivery can lead to severe and even fatal complications for both mother and child. Uterine rupture can result from a variety of complications, but the most common that we see is the weakening of the uterine wall caused by a previous cesarean section (C-section). These weaknesses are most apparent during an attempted vaginal birth after cesarean (VBAC) when the uterus is under extreme stress.


The uterus is a thick-walled hollow organ made up primarily of interlaced bundles of smooth muscle that give the uterus the ability to expand dramatically in size as the fetus develops and to contract forcefully to expel the fetus during delivery. In a C-section, the muscular wall of the uterus is cut creating a large opening to allow the surgeon to remove the fetus through an abdominal incision when the fetus fails to pass normally through the mother's pelvis. While this procedure provides a relatively safe and effective means of avoiding complications in the initial delivery, it can set the stage for increased complications in later pregnancies.


Following a C-section, the cut edges of the uterus are repaired with sutures and this incision site will heal over time, but this healing is accomplished with scar tissue, not new pristine muscle. This region of scar tissue at the original C-section site can never regain the full strength and flexibility of undamaged uterine tissue. In future pregnancies and particularly in future deliveries, when the uterus is again placed under stress by stretching and contracting, there is a substantial risk that there may be tearing or a complete rupture at the previous C-section site.


Risks of uterine rupture can affect both the mother and the fetus. For the mother, there is a risk of significant hemorrhage. The uterus is a highly vascular organ and tears can stretch and lacerate vessels of a variety of sizes. If not recognized and repaired promptly, these vascular injuries could prove fatal. For the fetus, there are a variety of risks. If the tear happens to compromise the placenta or major vessels supplying the uterus, there could be an interruption of umbilical blood flow leading to hypoxia or reduced oxygenation of the fetus. Also, if the rupture is of sufficient size, the fetus could be expelled out into the abdomen of the mother. This expulsion can also cause a partial or complete detachment of the placenta leading to a complete loss of blood supply to the fetus resulting in complete deoxygenation. An immediate diagnosis of the rupture and a repeat C-section would be necessary to rescue a fetus in such a case.


Years ago, VBAC was not an option. Any woman would delivered via C-section would never have been given the option of vaginal delivery in future pregnancies. Advances in surgical techniques and other medical practices have now made VBAC a viable option, but not all risks have been eliminated. The risks for a VBAC are significantly higher than for a normal vaginal birth. Such a delivery must be monitored closely and adequate facilities must be on hand and available to deal with any sudden emergencies. Any uterine rupture may result in devastating consequences for both mother and child.

Building an Attorney’s Medical Reference Library

As I’ve been writing these various articles covering a wide range of medical-legal topics over the past few years, many readers have contacted me with questions regarding the references that I use. While some are interested in specific references for specific topics, I have noticed that most are just interested in building a good medical reference library for use in their practice. I believe that that is an admirable goal.

While my reference library is filled with a wide variety of anatomical atlases, cellular biology texts, chemistry texts and multiple surgical atlases, I would never dream of recommending that the average personal injury or medical malpractice attorney spend the money it would require to build such a library. I set out to try to come up with a comprehensive and affordable list and one of my first steps was to call Ms. Janabeth Evans Taylor, a widely known and respected medical-legal consultant to see if she had any recommendations. Luckily, I discovered that Janabeth has already written a great article on this topic and she has agreed to let me share it with you.

Janabeth Evans (Taylor), R.N., R.N.C., Paralegal, has been a successful medical-legal consultant since 1990. She has assisted attorneys in both state and federal court proceedings and is well recognized and highly respected for diligence, thoroughness, accuracy, and excellent communication skills. Ms. Evans (Taylor) has authored and co-developed a broad variety of publications and presentations for lawyers, paralegals and other professionals. Representative topics include medical research, internet search strategies, low speed vehicular crashes, drug litigation, soft tissue injury, placental pathology, and medical expert deposition preparation techniques.

Click here to read her excellent suggestions for Building Your Medical Library.

Custom Models for Litigation

Physical models have always been popular in education. We can all remember spinning a globe to learn our geography or building a volcano to better appreciate geology. Models became even more important for me as I began a more intense study of biology and medicine. When learning the structure of molecules, there was no substitute for our little set of balls and sticks and certainly having a full size skeleton model gave a better understanding of anatomy. Medical models of all types are often very helpful in grasping concepts of structure and proximity. For these reasons, physical models also have a long history of usefulness as demonstrative evidence in trial.

Although Medical Legal Art is not in the business of creating medical models, we have always made it a practice to resell a wide range of medical models for our clients who recognize the usefulness of these items. Regretfully, until recently, I have been unaware of any company in the country that was actively creating custom models for legal use. Often clients would call and request custom models that would not only show basic normal anatomy but also be able to show the case specific facts of their case. It was frustrating to have no recommendations for these customers.

But in the past few months I've been happy to get to know the people at Archetype 3D (http://www.archetype3d.com), a company that specializes in custom models of all types. I'm thrilled that I now have a solution for those who call me requesting a source for custom models and I wanted to help them spread the news regarding their services. Click on the link below to learn more about Archetype 3D and their commitment to the use of scale models in trial. I'm sure that you will find them as pleasant as I have if you find yourself in need of custom models.

The Argument for Scale Models as Legal Props in the Courtroom