Pelvis & Perineum
Bony pelvis, pelvic floor, pelvic viscera, and the urogenital and anal triangles.
30 entriesBony pelvis: 5Pelvic floor: 1Pelvic viscera: 3Female reproductive organs: 6Male reproductive organs: 4Perineum: 5
Bones (2)
- Bony pelvis HYRing formed by the two hip bones, the sacrum and the coccyx. Its inlet and outlet define the birth canal, and ring fractures from high-energy trauma can cause life-threatening hemorrhage.
- Hip bone HYLarge flat bone formed by the fusion of the ilium, ischium and pubis at the acetabulum. Its palpable landmarks guide the exam, and its apophyses are classic sites of avulsion fractures in adolescents.
Muscles (1)
Nerves (3)
- Pelvic autonomic nerves HYSympathetic hypogastric nerves and parasympathetic pelvic splanchnic nerves (S2–S4) that meet in the inferior hypogastric plexus to control the bladder, rectum and sexual function. They are at risk in prostate and rectal surgery.
- Pudendal nerve HYMain somatic nerve of the perineum (S2–S4), supplying the external anal and urethral sphincters, the perineal muscles and perineal skin. It is blocked at the ischial spine in labor and can be stretched in childbirth or entrapped in cyclists.
- Sacral plexus HYNerve network on the posterior pelvic wall (L4–S4) that gives the sciatic, gluteal and pudendal nerves. It supplies the buttock, posterior thigh, nearly all of the leg and foot, the pelvic floor and the perineum.
Arteries (2)
- Internal iliac artery HYMain artery of the pelvis, supplying the pelvic viscera, perineum, gluteal region and medial thigh. Its branches bleed in pelvic fractures and are embolized for postpartum hemorrhage and fibroids.
- Uterine artery HYBranch of the internal iliac artery that crosses above the ureter beside the cervix to supply the uterus. It is ligated in hysterectomy, embolized for fibroids and postpartum hemorrhage, and greatly enlarged in pregnancy.
Lymphatics (1)
Organs (13)
- Anal canal HYTerminal 3–4 cm of the gut, surrounded by the internal and external anal sphincters. The pectinate line divides it into two halves with different blood supply, lymph drainage, nerves and diseases.
- Ductus deferens and seminal glands Thick-walled muscular duct carrying sperm from the epididymis to the ejaculatory duct, joined behind the bladder by the seminal gland. It is cut in vasectomy and absent in men with cystic fibrosis.
- Ovary HYPaired almond-shaped gonads on the lateral pelvic wall that produce oocytes and sex hormones. Their blood supply comes from the aorta, which explains torsion, and their lymph drains to the para-aortic nodes.
- Penis HYMale copulatory and urinary organ made of three erectile bodies — two corpora cavernosa and the corpus spongiosum around the urethra. Erectile dysfunction, priapism, penile fracture and phimosis/paraphimosis are its key problems.
- Prostate HYWalnut-sized gland around the prostatic urethra below the bladder. BPH arises in the transition zone and carcinoma mostly in the peripheral zone, which is the part felt on digital rectal exam.
- Rectum HYFinal part of the large intestine, from the rectosigmoid junction at S3 to the anorectal junction at the puborectalis sling. Rectal cancer staging and treatment depend on its peritoneal relations and pelvic surroundings.
- Testis and epididymis HYPaired male gonads in the scrotum with the epididymis along their back. Torsion is a surgical emergency, and aortic blood supply plus para-aortic lymph drainage reflect the testis's descent from the abdomen.
- Urethra HYTube from the bladder to the exterior — about 18–20 cm and S-shaped in males, about 4 cm in females. The site of the injury determines where extravasated urine goes, and urethral injury must be excluded before catheterizing a trauma patient.
- Urinary bladder HYDistensible muscular reservoir for urine lying behind the pubis. Its autonomic control explains neurogenic bladder, and rupture type (intraperitoneal vs extraperitoneal) decides management.
- Uterine tubes HYPaired tubes that carry the oocyte from the ovary to the uterus; fertilization usually occurs in the ampulla. They are the most common site of ectopic pregnancy and are damaged by pelvic inflammatory disease.
- Uterus HYThick-walled muscular organ between the bladder and rectum in which the embryo implants and develops. Fibroids, endometrial cancer, cervical cancer and postpartum hemorrhage are its key clinical problems.
- Vagina HYFibromuscular canal from the cervix to the vestibule. Its fornices, relations and split nerve and lymph supply matter for pelvic exams, vaginitis, prolapse and cancer spread.
- Vulva Female external genitalia in the urogenital triangle — mons pubis, labia, clitoris, vestibule and vestibular glands. Bartholin gland cysts and abscesses, lichen sclerosus and vulvar cancer are the key problems.
Joints (2)
- Pubic symphysis Fibrocartilaginous midline joint between the two pubic bones. It widens in pregnancy and after open-book pelvic injuries, and is a source of groin pain in athletes (osteitis pubis).
- Sacroiliac joint HYStrong, nearly immobile joint between the sacrum and ilium that transmits body weight to the pelvis. It is the classic site of inflammatory sacroiliitis in axial spondyloarthritis.
Ligaments (2)
- Broad ligament Double fold of peritoneum draped over the uterus, tubes and ovaries to the pelvic walls. It carries their vessels, and the ureter runs beneath its base, where it is at risk during hysterectomy.
- Sacrotuberous and sacrospinous ligaments HYTwo strong ligaments from the sacrum and coccyx to the ischium that stabilize the sacrum and turn the sciatic notches into the greater and lesser sciatic foramina, the gateways between pelvis, gluteal region and perineum.
Spaces & regions (4)
- Ischioanal fossa Paired fat-filled wedge-shaped spaces on either side of the anal canal. The pudendal canal lies in their lateral wall, and anorectal abscesses spread through them, sometimes in a horseshoe pattern.
- Perineal pouches HYTwo fascial compartments of the urogenital triangle, separated by the perineal membrane. Their fascial attachments determine where urine spreads after urethral injury and how Fournier gangrene tracks.
- Perineum HYDiamond-shaped region below the pelvic diaphragm, divided into the urogenital and anal triangles. The perineal body at its center is torn in obstetric lacerations, and saddle anesthesia here signals cauda equina syndrome.
- Rectouterine pouch HYDeepest recess of the female peritoneal cavity, between the uterus and rectum. Blood, pus and ascites collect here; the male equivalent is the rectovesical pouch.