|From the superior view of the pelvis, you should be able to identify the following:
|The pelvic brim extends from promontory of the sacrum, arcuate line of the ilium, pectineal line (pectin of pubis) and pubic crest. Some people divide the pelvis into a greater (or false) pelvis and lesser (or true) pelvis. They are separated by using the pelvic brim as the limiting line. The greater pelvis is located above the pelvic brim and the lesser pelvis below the brim.
No muscle crosses the pelvic brim. If they did, they would be in the way during childbirth.
|Turn the pelvis over and identify the structures on the back:
|From the lateral view, identify the:
|In this image, the pelvis is shown as it would be in the erect posture. The anterior superior iliac spine and pubic tubercle are in the same vertical plane.
Looking at the pelvis from the inside, you should be able to identify the following items:
|Strong ligaments are necessary to hold the hip bone to the sacrum. These are found anteriorly and posteriorly. Anteriorly, you can identify the anterior sacroiliac ligaments.
Posteriorly, there are even stronger ligaments:
The fifth lumbar vertebra also has a strong tie-in with the ilium through the iliolumbar ligament.
The sacrotuberous and sacrospinous ligaments complete the greater and lesser sciatic foraminae.
|This is the male pelvis as seen on sagittal section. Along with this image is a small image of the pelvic skeleton seen from the midline. You should always find something easy to identify so that you can tell where the front and back of the diagram are. I usually start by looking for the pubic symphysis for the front and sacrum for the back.
Starting from the pubic symphysis, work your way back and identify the following structures:
|In the sagittal section of the female pelvis, identify the following items, staring again from the front:
Again the pelvic inlet and outlet is represented as two lines. You can see exactly what structures are within the lesser pelvis. Again, they are midline structures. Since, in both male and female, the organs are centrally located, that means that their blood and/or nerve supply must come in from laterally or posteriorly and we will find this to be true when we examine the vasculature of the pelvis. We will also note that most of the muscles found in the pelvis lie laterally.
These midline structures are supported by a musculature pelvic diaphragm which we will discuss in a moment.
|Muscles of the female pelvis are the:
|The male pelvic muscles are the same as the female except that there is no vagina to support in the male.
Identify the following:
The puborectalis is actually a part of the pubococcygeus muscle that wraps around the posterior aspect of the rectum forming a sling that holds the rectum forward in the pelvis.
The pubococcygeus and iliococcygeus muscles make up the levator ani. The muscles of the levator ani are important supportive muscles for the midline organs of the pelvis. Any weakness in these muscles can cause clinical problems of urinary or fecal incontinence.
|With one exception, the arteries of the pelvis are branches of the internal iliac artery. The exception is the superior rectal artery which is a branch of the inferior mesenteric artery.
Starting posteriorly, the branches of the internal iliac artery are as follows:
|The nerves of the pelvis are derived from the:
The lumbosacral plexus is made up of:
The sacral sympathetic chain is the continuation of the lumbar chain.
The sacral part of the parasympathetic nervous system arises from S2, S3, S4 and supplies the pelvic structures as well as the left colic flexure, descending colon and sigmoid colon.
|Compare the male and female bladders.
Male bladderThis image displays the male urinary bladder opened from the top and front and defining the:
Female bladderIn the female bladder, identify:
|The prostate gland is a cone-shaped gland about the size of a chestnut and is made up of connective tissue and smooth muscle. Parts of relations of the gland are:
If the prostate is opened up from the front, you can identify the following:
|The uterus is a midline organ and is held to the lateral walls of the true pelvis by a double layer of peritoneum, called the broad ligament. The broad ligament also encloses the uterine tube in its upper free border, the ovarian artery, the round ligament of the uterus, uterine artery, ovary, and the ovarian ligament. A better understanding of the relationships to the broad ligament can be gained if you also look at a section through the broad ligament. In the first image, you are looking at the posterior aspect of the broad ligament and the posterior wall of the vagina has been opened up.
These items should be found in relation to the broad ligament.
In the section through the broad ligament pay attention to the:
|The rectum and anal canal are clinically important parts of the intestinal tract because, by either palpation or rectoscope or sigmoidoscope, they can be easily examined in a routine physical. Tumors, hemorrhoids or abscesses are frequent in this part of the GI tract.
The rectum is the continuation of the sigmoid colon and at the point of their junction, the rectum becomes covered by peritoneum only on its anterior surface, and therefore becomes retroperitoneal.
The rectum terminates approximately at the attachment of the levator ani to its borders. Also at this point, is the pectinate line which, anatomically, is the anorectal junction.
The inside of the rectum is thrown into folds called rectal valves. These maintain the fecal material until water is removed and a bowel movement occurs. At that point the rectum elongates and the valves become less prominent.
At the lower end of the rectum, a series of rectal columns encircle the rectum. Between the column are rectal sinuses. Outside of the columns is found the internal rectal plexus of veins. It is here that internal hemohhroids are found.
At the junction of the rectum and anal canal, the columns and sinuses form a dentate or pectinate appearance. This is called the pectinate line and is the starting point of the anal canal which is about 2.5-4.0 cm long.
The lining of the anal canal is continuous with the skin at the white line of Hilton (or intersphincteric line). This line can be felt with the finger as a small indentation between the internal anal sphincter (circular muscle of the rectal wall) and the subcutaneous external anal sphincter. The external anal sphincter is much stronger to the touch than the internal. Note that the external anal sphincter consists of three parts, the deep, superficial and subcutaneous.
Arteries to the rectum
|There are three sources of arterial supply to the rectum and anus:
|Surrounding the rectum and anus is a very dense rectal plexus of veins. The upper part of the plexus will send tributaries to form the superior rectal vein which then goes into the inferior mesenteric vein.
From the middle part of the plexus, along with tributaries from the bladder, prostate and seminal vesicle pass to the internal iliac vein
From the inferior part of the plexus, drainage is into the internal pudendal vein.
|From the rectum, lymphatics pass eventually into the inferior mesenteric group of preaortic lymph nodes.
From the anal canal, lymphatics pass along the middle rectal artery to end in the internal iliac nodes and from these to the common iliac nodes and then to the lateral aortic group of nodes.
From the anus, below the white line of Hilton, the lymphatics join those of the perineum and scrotum and pass into the superficial inguinal nodes
|This is copyrighted©1999 by Wesley Norman, PhD, DSc|