The pelvis is the region found between the trunk and lower limbs. In females, the pelvis is wider and lower than that of their male counterpart, making it more suited to accommodate a fetus during both pregnancy and delivery. Using cross-sectional anatomy imagery of this area allows a visual medium that facilitates the understanding of its structural organization. That will allow us to have an unique representation of the positions, sizes, shapes and relationships of the female pelvic structures.
Anatomy of the female pelvis
The cross-sectional anatomy of the female pelvis shows five bones: two hip bones, sacrum, coccyx and two femurs. Each hip bone is formed by the fusion of three bones: the ilium, pubis and ischium. The sacrum and coccyx are also comprised of smaller bones. The first is formed by the fusion of the five sacral vertebrae (S1-S5), and the latter by the fusion of the four coccygeal vertebrae. The femur is the strong thigh bone. It articulates with the hip, forming the ball-and-socket hip joint.
There’s a numerous variety of muscles that can be seen in the female pelvis, depending on the level of the cross section. The abdominal region includes the external oblique, internal oblique, transversus abdominis, rectus abdominis and pyramidalis muscles. The muscles of the back region include the quadratus lumborum, latissimus dorsi, serratus posterior inferior, erector spinae, interspinales and transversospinalis muscles. The muscles present in the thigh region can be split into three sections, anterior, medial and posterior. The anterior compartment is comprised of the iliopsoas, quadratus femoris, sartorius, and pectineus. The medial compartment is comprised of the adductor magnus, adductor longus, adductor brevis, obturator externus, and gracilis. The posterior compartment is comprised of the biceps femoris, semitendinosus and semimembranosus muscles. In the gluteal region, the muscles seen there are the gluteus maximus, gluteus medius, gluteus minimus and tensor fascia latae, as well as the deeper piriformis, gemellus superior, gemellus inferior and obturator internus muscles. The pelvic floor includes the levator ani, bulbospongiosus and the deep transverse perineal muscles.
The major organs present in a female pelvis cross section are those of the digestive, urinary and reproductive systems. Organs of the digestive tract include the ascending and sigmoid colon, ileum of the small intestine, rectum and anal canal. Organs of the urinary system include the urethra, bladder and the two ureters. Organs of the female reproductive system present in the pelvis are subdivided into internal and external genitalia. The internal genitalia consist of the uterus, two uterine tubes, two ovaries and the vagina. The external genitalia, on the other hand, mainly consist of the mons pubis, clitoris, labia majora and minora, and Bartholin glands.
The arteries located in the female pelvic region include the aorta, common iliac and branches of the external and internal iliac arteries. The veins in this area are similar to that of their corresponding arteries, with the addition of the inferior vena cava. The nerves present include those arising from the sacral and coccygeal plexuses, as well as the obturator nerve originating from the lumbar plexus.
Ultrasound is the imaging modality usually chosen for the evaluation of the female pelvis. That said, it has its set of shortcomings, such as limited ﬁeld of view, patient size and its dependency on the skill and experience of the operator. In that case, computed tomography (CT) and magnetic resonance imaging (MRI) become diagnostic tools for female pelvic pathologies. These scans depend on the cross-sectional analysis of the complex anatomic structures in the female pelvic region and play a vital role in clinical practice. They can detect small sized ovarian cysts and polyps, hemorrhages, tubal abnormalities, uterine endometrial pathologies, pelvic floor dysfunction, as well as other gynecological disorders.