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Questions and Answers
Which muscle is not part of the pelvic diaphragm?
What is the primary function of the pubococcygeus muscle?
What condition is characterized by involuntary urine leakage during activities that increase abdominal pressure?
During which biological process may the levator ani be injured?
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Which part of the levator ani muscle forms a U-shaped sling posterior to the anorectal junction?
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The tendinous arch of the levator ani serves as an attachment point for which structure?
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What is the primary purpose of pelvic floor exercises?
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Which of the following conditions is a form of prolapse through the vagina?
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Which bones form the pelvic girdle?
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What structure forms the inferior limit of the pelvic cavity?
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What is the function of the sphincter during ejaculation?
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Which part of the uterus is located at the top?
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Which structure separates the greater pelvis from the lesser pelvis?
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Where does the rectum commence in the human body?
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What is the pecten pubis associated with?
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Which structure acts as the voluntary 'gate-keeper' for the anal canal?
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Which of the following does NOT form part of the pelvic floor?
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What does the pectinate line separate in the anal canal?
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What are the clinical correlations associated with the prostate primarily related to?
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Which type of innervation is responsible for the sensitivity to pain in the inferior portion of the anal canal?
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Which of the following structures is NOT considered a pelvic viscera?
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What is the typical position of the uterus in adults?
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Which part of the uterine tubes is the usual site of fertilization?
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Which structure connects the ovaries to the uterus?
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What is the deepest region of the vaginal fornices?
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What is the function of the cilia in the ovaries?
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What anatomical feature surrounds the prostatic urethra?
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Which of the following describes a retroverted uterus?
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Which of the following describes the infundibulum of the uterine tubes?
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Which zone of the prostate is most prone to benign prostatic hypertrophy?
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What substance is notably found in prostatic fluid?
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Which lobe of the prostate is most commonly associated with prostatic cancer?
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Which part of the urinary bladder is formed by the detrusor muscle fibers?
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What is the primary component of the anterior region of the prostate?
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What is the function of prostatic fluid in semen?
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Which structure is formed when the ductus deferens joins the duct of the seminal gland?
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What is the primary function of the internal urethral sphincter formed by detrusor muscle fibers?
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Study Notes
Pelvic Girdle
- Formed by right and left hip bones (pelvic bones)
- Each hip bone develops from the fusion of 3 bones: ilium, ischium, and pubis
- Pecten pubis (pectineal line) is on the upper border of the superior pubic ramus.
- Provides attachment for the pectineal ligament (an extension of the lacunar ligament).
Pelvic Cavity
- The inferoposterior part of the abdominopelvic cavity.
- Limited inferiorly by the pelvic diaphragm (made up of muscles and fascia).
- The Perineum is below the pelvic diaphragm.
- The pelvic cavity is divided into greater (false) pelvis and lesser (true) pelvis by the pelvic brim.
Pelvic Walls/Boundaries
-
Muscles of the Pelvic Walls
- Piriformis (Posterior wall)
- Obturator internus (Lateral wall)
-
Muscles of the Pelvic Floor (Pelvic Diaphragm)
- Levator ani
- Puborectalis
- Pubococcygeus
- Iliococcygeus
- Coccygeus
- Levator ani
### Pelvic Diaphragm
- Stretches between:
- Pubis anteriorly
- The coccyx posteriorly
- From one lateral pelvic wall to the other
- Consists of:
- Levator ani
- Coccygeus muscles
-
Levator ani
- Largest & most important muscle of the Pelvic floor.
- Has three parts:
- Puborectalis: forms a U-shaped sling posterior to the anorectal junction.
- Pubococcygeus: arises from the posterior part of the body of the pubis and passes back horizontally.
- Iliococcygeus: posterior part of the levator ani.
-
Tendinous arch of the levator ani
- Formed from the thickening of the obturator internus fascia.
- Serves as the lateral attachment point for a portion of the levator ani muscles.
- The attachment of the levator ani to the obturator fascia divides the obturator internus into a superior pelvic portion and an inferior perineal portion.
Injury to Pelvic Floor
- Levator ani may be injured during childbirth.
- Pubococcygeus and puborectalis are the muscles torn most often.
- Weakening of these muscles decreases support for the vagina, bladder, uterus, or rectum.
- This can lead to:
- Urinary stress incontinence
- Prolapse of pelvic organs through the vagina (e.g., cystocele, rectocele, enterocele).
Position of the Uterus
- The adult uterus is usually anteverted and anteflexed.
- Anteversion: Uterus is tipped anterosuperiorly relative to the axis of the vaginal canal.
- Anteflexed: Flexed or bent anteriorly relative to the cervix.
- Retroversion: Fundus and body of uterus are bent backward on the vagina.
- Retroflexion: When the body of the uterus is bent backward on the cervix.
Uterine Tubes
- Also known as Fallopian tubes or Oviducts.
- About 4 inches (10 cm) long.
- Lies in the free edge of the Broad ligament (Mesosalpinx).
- Extend laterally and open into the peritoneal cavity near the ovaries.
- Divisible into 4 parts:
- Infundibulum: funnel-shaped distal end of the tube that opens into the peritoneal cavity.
- Ampulla: widest & longest, thin walled and tortuous. Usual site of fertilization.
- Isthmus: narrow, straight and thick walled.
- Uterine or Intramural: short intramural segment of the tube that passes through the wall of the uterus.
Ovaries
- Almond shaped.
- Suspended from the posterior aspect of the broad ligament.
- Release oocytes into the peritoneal cavity close to ostia of uterine tubes that are swept up by cilia.
- Connected to the uterus via the ovarian ligament.
- The suspensory ligaments attach each ovary to the pelvic sidewall.
- These ligaments contain the ovarian vessels, lymphatics, and nerves.
Vagina
- Muscular tube extending upward and backward from the vestibule of the vagina to the cervix.
- Has anterior and posterior walls which are normally in apposition.
- The area of the vaginal lumen, which surrounds the cervix, is divided into four regions or fornices:
- Anterior
- Posterior
- Right and left lateral
- The posterior fornix is the deepest and is closely related to the rectouterine pouch.
Prostate
- Accessory gland of the male reproductive system.
- Surrounds the prostatic urethra.
- Glandular part comprises ~2/3 of the gland, fibromuscular part comprises 1/3.
- The fibrous capsule of the prostate is dense and neurovascular, incorporating the prostatic plexuses of veins and nerves.
- The fascia covering the posterior surface of the prostate and separating it from the rectum is the Denonvilliers’ (Rectovesical/Rectoprostatic) fascia.
Lobes of the Prostate
- Anterior (isthmus): lies anterior to the urethra. Mostly fibromuscular
- Left and right (lateral) lobes: located on lateral sides of urethra. Forms major part of prostate.
- Median (middle): lies posterior to the urethra. Tends to undergo hormone-induced hypertrophy (Benign Prostatic Hypertrophy, BPH).
- Posterior (inferoposterior): lies posterior to urethra and inferior to ejaculatory duct. Palpable by digital rectal examination. Most prostatic cancer arises in the posterior lobe.
Glandular zones of the prostate
- Glandular tissue of the prostate arranged in three concentric zones:
- Peripheral zone: glands in this zone are prone to carcinoma.
- Central zone: surrounds the ejaculatory ducts.
- Transitional zone: prone to benign prostatic hypertrophy.
- The anterior region is usually devoid of glandular components. It is composed of fibromuscular tissues.
Prostatic Fluid
- Secreted through many prostatic ducts open into the prostatic sinuses on either side of the seminal colliculus on the prostatic urethra.
- Prostatic fluid contains zinc, citric acid, and some enzymes, including prostate-specific antigen.
- It constitutes ~20% of the volume of semen and plays a role in the activation of sperms.
Ductus Deferens
- Continuation of the duct of the epididymis.
- Ascends within the spermatic cord.
- Ends by joining the duct of the seminal gland to form the ejaculatory duct.
- Vasectomy: sterilizing method whereby part of the ductus deferens is ligated and/or excised. The subsequent ejaculated fluid contains seminal fluid and prostatic fluid but no sperms.
Seminal Glands and Ejaculatory Ducts
- Lie between the fundus of the urinary bladder and the rectum.
- Secretes an alkaline fluid with fructose.
- The duct of the seminal vesicles joins the ductus deferens to form the ejaculatory duct that opens into the prostatic urethra.
Urinary Bladder
- Separated from the pubic bones by a retropubic space (of Retzius).
- Has Apex, Body, Fundus, and Neck.
- The detrusor muscle fibers form the wall of the bladder.
- Toward the neck of the male bladder, the muscle fibers form the involuntary internal urethral sphincter.
- The sphincter contracts during ejaculation to prevent retrograde ejaculation of semen into the bladder.
- Trigone is the smooth triangular region of the posterior wall where the muscle fibers are closely adherent to the mucosa.
Rectum and Anal Canal
- The rectum commences at the level of S3 as a continuation of the sigmoid colon.
- Continues as the anal canal at the level of the tip of the coccyx, where it takes on an acute inferior angle, the anorectal flexure, formed by the puborectalis muscle.
- External anal sphincter: the voluntary "gate-keeper" for the anal canal.
- Internal anal sphincter: smooth muscle and under autonomic nerve control.
Anal Canal
- Divided into upper and lower portions based on developmental origin.
- The pectinate or dentate line demarcates the junction of the upper and lower anal canal.
- The superior part of the anal canal (visceral; derived from the embryonic hindgut), and the inferior part (somatic; derived from the embryonic proctodeum).
- Upper and lower portions have different blood, nerve, and lymphatic supplies.
- Anal columns are formed by submucosal blood vessels, primarily veins. These veins form the internal venous plexus.
- A similar plexus lies in the perianal subcutaneous tissues and is termed the external venous plexus. The two plexuses anastomose extensively and are the cause of internal and external hemorrhoids.
- The nerve supply to the anal canal superior to the pectinate line is visceral innervation from the sympathetic and parasympathetic. It is sensitive only to stretching.
- The nerve supply of the anal canal inferior to the pectinate line is somatic innervation derived from the inferior rectal nerves. Therefore, this part of the anal canal is sensitive to pain, touch, and temperature.
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Description
Test your knowledge on the pelvic girdle and its structures. This quiz covers the anatomy of the hip bones, pelvic cavity, and muscles associated with the pelvic floor. Challenge yourself and learn more about the important components of the pelvic region.
