pelvis [pel´vis] (L.)
1. any basinlike structure in the body.
the bony pelvis, the lower (caudal) portion of the trunk of the body, forming a basin bounded anteriorly and laterally by the hip bones and posteriorly by the sacrum
; it is formed by the sacrum, the coccyx, and the ilium
, and ischium
, bones that also form the hip
and the pubic arch
. These bones are separate in the child, but become fused by adulthood. The pelvis is subjected to more stress than any other body structure. Its upper part, which is somewhat flared, supports the weight of internal organs in the upper part of the body. The floor of the pelvis
or pelvic floor
is the layer of tissue just below the outlet, formed by the coccygeal and levator ani muscles and the perineal fascia.
Pelvic structures in men and women differ both in shape and in relative size. The male pelvis is heart-shaped and narrow and proportionately heavier and stronger than that of the female, so that it is better suited for lifting and running. The female pelvis is constructed to accommodate the fetus during pregnancy and to facilitate its downward passage through the pelvic cavity in childbirth. The most obvious difference between the male and female pelvis is in the shape. A woman's hips are wider and her pelvic cavity is round and relatively large. There are differences in the shape of the female pelvis, which must be taken into account in childbirth. During pregnancy
the capacity of the pelvis and the pelvic diameters
are measured, so that possible complications during labor can be anticipated.
Dynamic pelvic floor imaging using MRI. MR sequences can now be acquired every half-second or so and this rapidity allows functional studies of the gastrointestinal tract to be undertaken. A and B, These sagittal views can be used to measure pelvic floor descent as well as to give valuable information on the local anatomy. C, Diagrammatic baseline sagittal view. (1 = pubococcygeal baseline; 2 = bladder base descent; 3 = uterocervical descent; 4 = anorectal junction descent.) From Aspinal and Taylor-Robinson, 2001.
Various types of pelvic inlets.
android pelvis one with a wedge-shaped inlet and narrow anterior segment typically found in the male.
anthropoid pelvis one whose anteroposterior diameter equals or exceeds the transverse diameter.
assimilation pelvis one in which the ilia articulate with the vertebral column higher (high assimilation pelvis) or lower (low assimilation pelvis) than normal, the number of lumbar vertebrae being correspondingly decreased or increased.
beaked pelvis one with the pelvic bones laterally compressed and their anterior junction pushed forward.
brachypellic pelvis a short oval type of pelvis, in which the transverse diameter exceeds the anteroposterior diameter by 1 to 3 cm.
contracted pelvis one showing a decrease of 1.5 to 2 cm in an important diameter; when all dimensions are proportionately diminished, it is a generally contracted pelvis.
cordate pelvis a heart-shaped pelvis.
dolichopellic pelvis a long, oval pelvis with the anteroposterior diameter greater than the transverse diameter.
flat pelvis one in which the anteroposterior dimension is abnormally reduced.
frozen pelvis a condition, due to infection or carcinoma, in which the adnexa and uterus are fixed in the pelvis.
funnel pelvis one with a normal inlet but a greatly narrowed outlet.
gynecoid pelvis the normal female pelvis: a rounded oval pelvis with well rounded anterior and posterior segments.
a generally contracted pelvis with an oval shape, a high sacrum, and inclination of the walls; called also juvenile pelvis
pelvis jus´to ma´jor an unusually large gynecoid pelvis, with all dimensions increased.
pelvis jus´to mi´nor a small gynecoid pelvis, with all dimensions symmetrically reduced.
kyphotic pelvis a deformed pelvis marked by increase of the conjugate diameter at the brim with decrease of the transverse diameter at the outlet.
the part of the pelvis superior to a plane passing through the ileopectineal lines. Called also false pelvis
and greater pelvis
the part of the pelvis inferior to a plane passing through the ileopectineal lines. Called also lesser pelvis
and true pelvis
Nägele's pelvis one contracted in an oblique diameter, with complete ankylosis of the sacroiliac synchondrosis on one side and imperfect development of the sacrum and coxa on the same side.
Otto pelvis one in which the acetabulum is depressed, accompanied by protrusion of the femoral head into the pelvis.
platypellic pelvis (platypelloid pelvis) one shortened in the anteroposterior aspect, with a flattened transverse, oval shape.
rachitic pelvis one distorted as a result of rickets.
the funnel-shaped expansion of the upper end of the ureter
into which the renal calices
open; it is usually within the renal sinus
, but under certain conditions a large part of it may be outside the kidney (extrarenal pelvis).
scoliotic pelvis one deformed as a result of scoliosis.
split pelvis one with a congenital separation at the symphysis pubis.
spondylolisthetic pelvis one in which the last, or rarely the fourth or third, lumbar vertebra is dislocated in front of the sacrum, more or less occluding the pelvic brim.
pelvis (pel'vis) (pel'vez?) (pel'vi-sez) plural.pelvespelvises [L. pelvis, basin]
1. A basin-shaped structure or cavity.
2. The bony compartment comprising the innominate bones, the sacrum, and the coccyx, joined at the symphysis pubis, sacroiliac, and sacrococcygeal articulations by a network of cartilage and ligaments. The structure supports the vertebral column and articulates with the lower limbs. See: illustration
The cavity encompassed by the innominate bones, the sacrum, and the coccyx.
The pelvis is separated into a false or superior pelvis and a true or inferior pelvis by the iliopectineal line and the upper margin of the symphysis pubis. The circumference of this area constitutes the inlet of the true pelvis. The lower border of the true pelvis, termed the outlet, is formed by the coccyx, the protuberances of the ischia, the ascending rami of the ischia, and the descending rami of the ossa pubis and the sacrosciatic ligaments. The floor of the pelvis is formed by the perineal fascia, the levator ani, and the coccygeus muscles. All diameters normally are larger in the female than in the male.
Interspinous: The distance between the outer edges of the anterosuperior iliac spines, the diameter normally measuring 26 cm (1014 in.). Intercristal: The distance between the outer edges of the most prominent portion of the iliac crests, the diameter normally being 28 cm (11 in.). Intertrochanteric: The distance between the most prominent points of the femoral trochanters, 32 cm (1212 in.). Oblique (right and left): The distance from one posterosuperior iliac spine to the opposite anterosuperior iliac spine, 22 cm (812 in.), the right being slightly greater than the left. External conjugate: The distance from the undersurface of the spinous process of the last lumbar vertebra to the upper margin of the anterior surface of the symphysis pubis, 20 cm (778 in.).
True conjugate: The anteroposterior diameter of the pelvic inlet, 11 cm (414 in.), the most important single diameter of the pelvis. Diagonal conjugate: The distance between the promontory of the sacrum to the undersurface of the symphysis pubis, 13 cm (518 in.). Two cm (34 in.) are deducted for the height and inclination of the symphysis pubis to obtain the diameter of the conjugate. Transverse: The distance between the ischial tuberosities, 11 cm (414 in.). Anteroposterior (of outlet): The distance between the lower border of the symphysis pubis and the tip of the sacrum, 11 cm (414 in.). Anterior sagittal: The distance from the undersurface of the symphysis pubis to the center of the line between the ischial tuberosities, 7 cm (234 in.). Posterior sagittal: The distance from the center of line between the ischial tuberosities to the tip of the sacrum, 10 cm (4 in.).
pelvis aequabiliter justo major
A pelvis that is symmetrically larger than the standard in all its dimensions. Synonym: giant pelvis
pelvis aequabiliter justo minor
A pelvis with all its dimensions uniformly smaller than the standard. Synonym: reduced pelvis
The normal shape of the male pelvis. About 30% of women share this bony configuration; however, the heart-shaped inlet, convergent sidewalls, slanted sacrum, and narrow sacrosciatic notch pose problems for childbearing. The narrowed dimensions increase the risk of fetopelvic disproportion, obstructed labor, and cesarean delivery. Synonym: masculine pelvis
A deviation from the normal gynecoid configuration of the pelvic bones in which the anterior-posterior diameter is greater than the transverse diameter. It is found in approximately 20% of women. Deviations from the normal gynecoid configuration include a long, oval, narrow inlet and narrow sacrum, straight sidewalls, and a wide sacrosciatic notch. The shape increases the potential for fetal posterior positions during childbearing.
A structural abnormality that results from a developmental lumbosacral fusion or from a sacrococcygeal fusion.
A pelvis with the pelvic bones laterally compressed and pushed forward so that the outlet is narrow and long. Synonym: rostrate pelvis; triradiate pelvis
The skeleton of the pelvis, consisting of the right and left hip bones (each made of an ilium, an ischium, and a pubis), the sacrum, and the coccyx.
An oval pelvis in which the transverse diameter is at least 1 cm longer, but no more than 3 cm longer, than the anteroposterior diameter of the pelvis.
brim of the pelvisBrim (2).
A pelvis in which one or more of the principal diameters is reduced to a degree that parturition is impeded.
A pelvis possessing a heart-shaped inlet.
A pelvis deformed subsequent to hip joint disease.
An abnormal pelvis in which the anteroposterior diameter is greater than the transverse diameter.
An unusually small pelvis in which all diameters are symmetrically reduced.
elastic pelvisOsteomalacic pelvis.
A renal pelvis located outside the kidney.
The portion of the pelvic cavity that lies above the pelvic brim, bounded by the linea terminalis and the iliac fossae. It supports the weight of the growing uterus during the middle and last trimesters of pregnancy. Synonym: pelvis major
A structural malformation in which the ilia are pushed forward to an almost parallel position; caused by rickets.
A pelvis in which the anteroposterior diameters are shortened.
Adhesion of the female reproductive organs to the peritoneum or bowel by cancer, endometriosis, or pelvic infection.
A pelvis in which the outlet is considerably contracted but the inlet dimensions are normal.
giant pelvisPelvis aequabiliter justo major.
A normal female pelvis. Relative to the male pelvis, it has a wider bone structure and a more oval shape.
A deformed pelvis resulting from softening of bones because of osteomalacia..
An adult pelvis that retains its infantile characteristics. Synonym: juvenile pelvis
pelvis justo major
An unusually large pelvis.
juvenile pelvisInfantile pelvis.
A deformed pelvis caused by rickets.
A deformed pelvis characterized by an increase of the conjugate diameter at the brim with reduction of the transverse diameter at the outlet.
A deformed pelvis in which the spinal column has an anterior curvature in the lumbar region.
pelvis majorFalse pelvis.
A female pelvis that resembles a male pelvis, esp. in that it is narrower, more conical, and heavier-boned and has a heart-shaped inlet. Synonym: android pelvis
pelvis minorTrue pelvis.
A deformed pelvis in which the vertebral column extends across the pelvic inlet.
A pelvis distorted because of osteomalacia. Synonym: elastic pelvis
Otto pelvis See: Otto pelvis
A rare structural malformation that resembles a flattened gynecoid pelvis with shortened anteroposterior and wide transverse diameters.
A rachitic pelvis similar to that of a person with osteomalacia.
A pelvis deformed from rickets.
reduced pelvisPelvis aequabiliter justo minor.
The expanded proximal end of the ureter. It is within the renal sinus of the kidney and receives the urine through the major calyces.
A pelvis shaped like a kidney.
Robert pelvis See: Robert pelvis
rostrate pelvisBeaked pelvis.
A tympanic depression in the inner wall, at the bottom of which is the fenestra rotunda.
A pelvis with a circular inlet.
A deformed pelvis resulting from spinal curvature.
simple flat pelvis
A pelvis with a shortened anteroposterior diameter.
A rachitic pelvis with a pointed pubic crest. Synonym: Kilian pelvis
A pelvis with a congenital division at the symphysis pubis.
A pelvis in which the last lumbar vertebra is dislocated in front of the sacrum, causing occlusion of the brim.
triradiate pelvisBeaked pelvis.
The portion of the pelvis lying below the iliopectineal line. The dimensions of the true pelvis are of obstetrical significance in determining the success of fetal descent. Synonym: pelvis minor