Pelvic cavity(Redirected from Lesser pelvis)
The various cavities of the human body as seen in a frontal projection, with the pelvic cavity labeled 4.
The various cavities of the human body as seen in a lateral projection, with the pelvic cavity labeled 4.
|Lymph||Primarily internal iliac lymph nodes|
The pelvic cavity primarily contains reproductive organs, the urinary bladder, the pelvic colon, and the rectum. The rectum is placed at the back of the pelvis, in the curve of the sacrum and coccyx; the bladder is in front, behind the pubic symphysis. In the female, the uterus and vagina occupy the interval between these viscera. The pelvic cavity also contains major arteries, veins, muscles, and nerves. These structures coexist in a crowded space, and disorders of one pelvic component may impact upon another; for example, constipation may overload the rectum and compress the urinary bladder, or childbirth might damage the pudendal nerves and later lead to anal weakness.
The pelvis has an anteroinferior, a posterior, and two lateral pelvic walls; and an inferior pelvic wall, also called the pelvic floor. The parietal peritoneum is attached here and to the abdominal wall.
The lesser pelvis (or "true pelvis") is the space enclosed by the pelvic girdle and below the pelvic brim: between the pelvic inlet and the pelvic floor. This cavity is a short, curved canal, deeper on its posterior than on its anterior wall. Some consider this region to be the entirety of the pelvic cavity. Others define the pelvic cavity as the larger space including the greater pelvis, just above the pelvic inlet.
The lesser pelvis is bounded in front and below by the pubic symphysis and the superior rami of the pubes; above and behind, by the sacrum and coccyx; and laterally, by a broad, smooth, quadrangular area of bone, corresponding to the inner surfaces of the body and superior ramus of the ischium, and the part of the ilium below the arcuate line.
|posterior: sacrum, coccyx||lateral: obturator internus||anterior: pubic symphysis|
The lesser pelvis contains the pelvic colon, rectum, bladder, and some of the sex organs. The rectum is at the back, in the curve of the sacrum and coccyx; the bladder is in front, behind the pubic symphysis. In the female, the uterus and vagina occupy the interval between these viscera.
The pelvic splanchnic nerves arising at S2-S4 are in the lesser pelvis.
The greater pelvis (or "false pelvis") is the space enclosed by the pelvic girdle above and in front of the pelvic brim. It is bounded on either side by the ilium; in front it is incomplete, presenting a wide interval between the anterior borders of the ilia, which is filled by the muscles and fascia of the anterior abdominal wall; behind is a deep notch on either side between the ilium and the base of the sacrum that is filled by the thoracolumbar fascia and associated muscles.
It is generally considered part of the abdominal cavity (this is why it is sometimes called the false pelvis). Some[who?] consider this region part of the pelvic cavity, while others reframe the classification question by calling the combination the abdominopelvic cavity.
The femoral nerve from L2-L4 is in the greater pelvis, but not in the lesser pelvis.
|broad ligament of the uterus||uterus||side of pelvis|
|* mesosalpinx||Fallopian tube||broad ligament of the uterus|
|cardinal ligament||cervix & vagina||pelvic wall|
|round ligament of the uterus||ovary||travels through inguinal canal, ends at mons pubis|
|suspensory ligament of the ovary||ovary||pelvic wall|
The pelvis can be classified into four main types by measuring the pelvic diameters and conjugates at the pelvic inlet and outlet and as oblique diameters.
|Between extreme lateral points of pelvic inlet||13.5–14 cm|
|Oblique diameter I||Right sacroiliac joint||Left iliopubic eminence||12-12.5 cm|
|Oblique diameter II||Left sacroiliac joint||Right iliopubic eminence||11.5–12 cm|
|Pubic symphysis||Promontory||~12 cm|
|Obstetric conjugate||Retropubic eminence
|Diagonal conjugate*||Inferior pubic ligament||Promontory||11.5–12 cm|
|Straight conjugate||Lower border of symphysis||Tip of coccyx||9.5–10 cm|
|Median conjugate||Lower border of symphysis||Lower border of sacrum||11.5 cm|
|Between ischial tuberosities||10–11 cm|
|Interspinous distance||Between anterior superior iliac spines||26 cm
|Intercristal distance||Between furthest lateral points of iliac crest||29 cm
|External conjugate||Spinous process of fifth lumbar vertebra||Upper edge of symphysis||~20 cm|
|Intertrochanteric distance||Between femurs||31 cm|
|*Because the true conjugate can not be measured directly it is derived from the diagonal conjugate which is measured through the vagina.|
- This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)
- Moore, Keith L. et al. (2010) Clinically Oriented Anatomy 6th Ed, ch.3 Pelvis and perineum, p.339
- Richard S. Snell Clinical Anatomy By Regions, Pelvic cavity p.242
- Tank, P. (2013) Grants Dissector 15th ed., ch.4 The abdomen, p.99
- "Anatomy of the Female Pelvis - D. El-Mowafi". Retrieved 2007-12-03.
- Drake et al. (2009) Grays Anatomy for Students, 2nd Edition, ch.5 Pelvis and perineum - general description, p.406
- Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.). Thieme. p. 190. ISBN 3-13-533305-1.