Not only may an anatomical structure be absent, such as in the case of renal aplasia or agenesis, or in the case of a non-existent circumflex coronary artery, but sometimes extra structures can be found. Such is the case where a kidney can present two or even three ureters, all functional. Double inferior vena cavae, cervical ribs, lumbar ribs, the list goes on and on!

Muscles can be added to this list, again, with absence of a muscle, or with new and completely unexpected attachments. An example of this is the presence of a continuation of the rectus abdominis muscle into the chest region, a variation called a sternalis muscle.

The accompanying image shows the sternalis muscle in one of the "muscle plates" of De Humani Corporis Fabrica Libri Septem, published in 1543 by Andreas Vesalius. This image was criticized by showing a muscle that does not exist, although Vesalius clearly stated in the text of his book that this was an anatomical variation that he had seen.

For many decades surgeons had to operate and "see what they could find". There were the days of the exploratory laparotomy. After the discovery of the application of X-rays by Wilhem Konrad Roentgen (1845 - 1923) and the incredible advances in imaging techniques including CT-scan, MRI, PET, etc, the surgeon is now not usually surprised by anatomical variations.

Another area where anatomical variations are extremely important is the heart's coronary circulation. Anatomical variations can cause different cardiac dominance. Normal anatomy states that there are two coronary arteries, yet, up to five separate coronary arteries arising directly from the ascending aorta have been described! There is one variation where the left coronary arises from the right coronary artery, effectively having only one artery arise from the aorta and being in charge of all the arterial supply to the heart. What happens if this single artery stenoses? Bear in mind that this is not an "anomalous" vessel, it is just an anatomical variation.

Sources:
1. Lahey DH, discussing the paper "Partial Hepatectomy with Intrahepatic Cholangiojejunostomy" by Wilson H, and Gillespie CE, Ann Surg. 1949 June; 129(6): 756–765
2. "Renal aplasia is the predominant cause of congenital solitary kidneys" Hiraoka, M et al Kidney Int. 2002 May;61(5):1840-4.

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"The only constant in anatomy is variation". This dictum is incredibly powerful and true. Even the so-called "anatomical constants" are subject to it.

One common misconception is that "we are all the same". This could not be further from the truth. Every body is different from every else's body. Anatomical variations range from the minimal to the incredible. One of the most interesting anatomical variations is the one called "situs inversus". In this case the individual is a mirror image of a human. The apex of the heart points to the right side of the body; the duodenum circles to the right, the liver "hangs" from the left side of the respiratory diaphragm, etc. This particular anatomical variation presents in different degrees and can sometimes coexist with some cardiovascular congenital abnormalities.

Shown here is an extremely rare case of a third kidney. Dixon (1911) describes in his research paper that as of that date, only 10 cases were known, of these only eight were recorded, with 87% of them found on the left side of the body. Click on the image for a larger depiction.

Source and primary image: "Supernumerary kidney: The occurrence of three kidneys in an adult male subject" Dixon, A.F. J. Anat. Physiol. 45:117-121, 1911.

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The prefix [para-] has a Greek origin and means "beside" or "alongside". Today we add the meaning of "parallel to".

We see the daily application of this prefix  in words such as [paramedic], [parajournalism], [paralogism], and [paranormal].

Medical applications of the term include:

• paraesternal: alongside the sternum, such as the internal thoracic vessels
• paramedian: alongside the median plane
• parasagittal: parallel to a sagittal plane (synomym with paramedian)
• paraumbilical: alongside the umbilicus, such as paraumbilical visceral extrusion in a gastroschisis
• parathyroid glands: glans that are found besides the thyroid gland, etc.

Otto C. Brantigan, MD. (1904-1981) An American surgeon and anatomist, Otto Charles Brantigan  was born in Chattanooga, TN in 1904. Having dropped out of high school to help his family and working as a first class machinist, he decided to continue with graduate school. He studied at the Northwestern University in Chicago, where he graduated from the Medical School in 1933.  In 1948 he became Chief of Surgery, and eventually became Professor of Surgery, Professor of Thoracic Surgery, and Professor of Anatomy at the Maryland School of Medicine.  He retired in 1976 having earned many accolades for his profuse surgical work and publications.

As a surgeon of the times, Dr. Brantigan had a wide area of interest. His over 110 publications and surgical work range from thoracoscopy to vascular, plastic, cardiac, and orthopedic surgery. He is most remembered for the pioneer work he did on chronic obstructive pulmonary disease (COPD), emphysema and lung volume reduction surgery (LVRS), which he presented in 1958. The procedure had (at the time) a very high mortality rate  (16 -20%) and Brantigan's work was not readily accepted.

It was not until J. Cooper and his team, revisited the operation proposed by Brantigan  that the operation was accepted, now with new surgical stapling and staple line buttressing technology.  Dr. Brantigan's name was recognized as a pioneer in lung emphysema surgery, unfortunately 14 years after his death. In 1994 his son, Dr Charles O. Brantigan delivered a beautiful biography of Dr. Otto Brantigan in the same meeting where Cooper presented his results with LVRS.

Personal note: I am proud to own one of the copies of Dr. O.C. Brantigan;s "Clinical Anatomy", a book that I use quite frequently. It is listed in my library catalog. Dr. Miranda.

Sources:
1. "Biography of Otto C Brantigan" C.O. Brantigan 1994 Meeting of the American Association for Thoracic Surgery
2. "LVRS in chronic obstructive pulmonary disease" Davies, L; Calverley, P. Thorax 1996;51(Suppl 2):S29-S34
3. ""Bilateral pneumectomy (volume reduction) for chronic obstructive pulmonary disease" Cooper, J.,The Journal of Thoracic and Cardiovascular Surgery Volume 109, Number 1:106-119
4. "The Surgical Approach to Pulmonary Emphysema" Brantigan, OC; Kress, MB; Mueller, EA. Chest. 1961; 39(5):485-499
5. "History of Emphysema Surgery" Naef, AP. Ann Thorac Surg 1997;64:1506-1508

Original image  courtesy of National Institutes of Health. Biography of Dr. Otto Brantigan courtesy of Dr. Charles O. Brantigan.

The rectum is the most distal segment of the large intestine. 

The word [rectum] arises from the Latin [rectus] and means "straight", such as its use in the name "rectus abdominis" for the "straight muscle of the abdomen".

It seems a misnomer, as the rectum of the human species is actually "S" shaped, as seen in the accompanying image. The reason for this discrepancy is that the rectum was named by Galen of Pergamon (129AD - 200 AD) who himself studied this structure in animals such as sheep and goats. In these animals the rectum is indeed straight, and since contradicting Galen was not acceptable (see Michael Servetus), the name has survived until this day. Even Andreas Vesalius has in his 1953 "Fabrica" a depiction of a straight rectum in the human! Click on the bar beneath the image to see Vesalius' image of the rectum.

The proximal end of the rectum is not clearly discernible from the sigmoidorectal region, from here the rectum has an "S" shape, measures approximately six to seven inches in length (15 - 17 cm), and it ends distally at the junction of the rectum with the  pelvic diaphragm. It is at this point that the anal canal begins.

Image source: "Tratado de Anatomia Humana" Testut et Latarjet 8 Ed. 1931 Salvat Editores, Spain
Recommended reading: "Transverse Folds of Rectum: Anatomic Study and Clinical Implications" Shafik, A, et al. Clin Anat 14: 196-203 (2001).

The term "collateral circulation" is generally used to denote a situation where small blood channels dilate and provide blood supply when a pathology creates a stricture and diminishes blood flow (ischemia).

Although the above is correct, the term is also applicable to a normal, non-pathological situation most common in the human body. Please refer to the accompanying image for the following explanation. If needed, click on the image for a larger depiction. In the image, the arrows represent direction of flow.

Most organs or organ segments receive blood supply from more than one source of blood supply. In some cases, like the stomach, there are up to four arteries that provide blood supply to the organ: the right and left gastric arteries, and the right and left gastroepiploic arteries.

This is extremely important, as these collateral channels maintain blood supply to areas that may be affected by bending, such as the elbow and knee, which have a rich collateral network. Most of the organs in the body, with some exceptions (brain, heart), have collateral circulation.

Collateral circulation is extremely important for surgery, as surgeons can safely remove parts of organs without affecting the blood supply to the organ. This is also true for all gastrointestinal anastomoses.