Pelvis and Perineum — MCQs

Pelvis and Perineum Indian Medical PG Practice Questions and MCQs

Question 551: What is the typical subpubic angle in females?

A. <65°
B. 65-75°
C. 85°
D. 110-120° (Correct Answer)

Explanation: ***110-120°*** - Females typically have a **wider subpubic angle**, which is an adaptation for childbirth, allowing the **pelvic outlet** to be larger [1] - This wider angle is a key distinguishing feature of the **female pelvis** compared to the male pelvis [1] - The increased angle facilitates passage of the fetal head during **parturition** *<65°* - This range is typically observed in the **male pelvis**, indicating a narrower **subpubic angle** [1] - A narrow subpubic angle contributes to the male pelvis's generally **smaller pelvic outlet** and more acute angle - The male subpubic angle typically ranges from **50-60°** *65-75°* - This range is also indicative of a **male-like pelvis**, though slightly wider than the extreme male range - It does not fall within the typical range for a female pelvis, which is designed for accommodating fetal passage during delivery [1] - Still significantly narrower than the female range *85°* - While wider than typical male angles, an 85° subpubic angle is **at the lower limit or below** the characteristic female range - The average female subpubic angle is typically **90° or greater**, with most sources citing ranges well above this value [1] - The significantly wider angle in females is essential for **obstetric function** [1]

Question 552: Which structures pass through the sacral hiatus?

A. S4 nerve root
B. S2 nerve root
C. S3 nerve root
D. S5 nerve root (Correct Answer)

Explanation: S5 nerve root - The **S5 nerve root** passes inferiorly through the sacral hiatus, emerging to supply motor and sensory innervation to the perianal region. - The sacral hiatus is the distal opening of the **sacral canal**, which contains the cauda equina and filum terminale. *S4 nerve root* - The **S4 nerve root** exits the sacral canal through the anterior and posterior sacral foramina, above the level of the sacral hiatus. - It contributes to the **pudendal nerve** and innervates pelvic floor muscles and some lower limb structures. *S2 nerve root* - The **S2 nerve root** exits the sacral canal superior to the sacral hiatus, typically through the second pair of sacral foramina. - It is a significant contributor to the **sciatic nerve** and innervates various muscles and skin in the lower limb. *S3 nerve root* - The **S3 nerve root** exits the sacral canal via the third pair of sacral foramina, which are located superior to the sacral hiatus. - It also contributes to the **sciatic nerve** and the **pudendal nerve**, providing innervation to the perineum.

Question 553: Waldeyer's fascia connects?

A. Rectum to sacrum (Correct Answer)
B. Rectum to uterus
C. Rectum to lateral wall of pelvis
D. Rectum to bladder

Explanation: ***Rectum to sacrum*** - **Waldeyer's fascia** (also known as the **rectosacral fascia**) is a critical anatomical landmark in pelvic surgery, forming a tough, fibrous sheet that connects the posterior surface of the **rectum** to the anterior surface of the **sacrum**. - This fascial condensation represents the fusion of the parietal and visceral pelvic fascia posteriorly, providing significant support to the rectum and defining the plane for surgical dissection during procedures like total mesorectal excision. *Rectum to uterus* - The connection between the rectum and uterus is formed by the **rectovaginal septum** (or pouch of Douglas in women), which is a peritoneal reflection, not Waldeyer's fascia. - Waldeyer's fascia is located posteriorly, specifically connecting the rectum to the sacrum, while the uterus is an anterior structure relative to the rectum. *Rectum to lateral wall of pelvis* - The connection of the rectum to the lateral pelvic wall is primarily achieved by the **lateral rectal ligaments**, which contain the middle rectal arteries. - Waldeyer's fascia is distinct from these lateral attachments and is specifically oriented in the posterior midline, connecting the rectum directly to the sacrum. *Rectum to bladder* - The connection of the rectum to the bladder (in males) is via the **rectovesical septum** (Denonvilliers' fascia), which is an anterior structure. - Waldeyer's fascia is a posterior structure and has no direct connection to the bladder.

Question 554: The glans penis is a continuation of?

A. Bulb of penis.
B. Corpora cavernosa.
C. Crus of penis.
D. Corpus spongiosum. (Correct Answer)

Explanation: ***Corpus spongiosum*** - The **glans penis** is anatomically the expanded distal end of the **corpus spongiosum**. - The **urethra** passes through the corpus spongiosum and exits at the **external urethral orifice** at the tip of the glans. - The corpus spongiosum surrounds the urethra throughout its length in the penis and expands distally to form the glans. *Corpora cavernosa* - The **corpora cavernosa** are paired erectile tissues that form the bulk of the shaft of the penis and attach proximally to the pubic arch. - They are responsible for the **rigidity of the penis** during erection but **terminate proximal to the glans** and do not extend into it. *Bulb of penis* - The **bulb of penis** is the expanded proximal part of the corpus spongiosum. - It is located in the superficial perineal pouch and is covered by the bulbospongiosus muscle. - While it is part of the corpus spongiosum, the glans represents the **distal**, not proximal, continuation. *Crus of penis* - The **crus of penis** (crura, plural) are the proximal attachments of the **corpora cavernosa** to the ischiopubic rami. - Each crus is covered by the ischiocavernosus muscle. - The crura do not contribute to the formation of the glans penis.

Question 555: Which structure is the primary vascular component passing through Alcock's canal?

A. Internal pudendal artery (Correct Answer)
B. Internal iliac artery
C. Inferior rectal vein
D. Inferior mesenteric vein

Explanation: ***Internal pudendal artery*** - The **internal pudendal artery** is the primary vascular structure that enters Alcock's canal (pudendal canal) along with the **internal pudendal vein** and **pudendal nerve**. - It supplies the perineum and gives off several branches within or after exiting the canal, including the **inferior rectal artery**, **perineal artery**, and arteries to the penis/clitoris. *Internal iliac artery* - The **internal iliac artery** is a large artery that gives rise to the internal pudendal artery, but it does not pass through Alcock's canal itself. - It supplies blood to the pelvic organs, gluteal region, and medial thigh. *Inferior rectal vein* - The **inferior rectal vein** is a tributary that drains into the **internal pudendal vein**, which does pass through Alcock's canal. - However, the inferior rectal vein itself is not considered the primary vascular component of the canal—that distinction belongs to the internal pudendal vessels. *Inferior mesenteric vein* - The **inferior mesenteric vein** drains blood from the descending colon, sigmoid colon, and rectum. - It primarily drains into the **splenic vein** and is part of the portal system, completely unrelated to Alcock's canal.

Question 556: What is the depth from the skin surface to reach the lower part of the sacroiliac joint in females?

A. 2 to 2 1/2 cm (Correct Answer)
B. 1 to 1 1/2 cm
C. 3 to 3 1/2 cm
D. 4 to 4 1/2 cm

Explanation: ***2 to 2 1/2 cm*** - In females, the **depth from the skin surface** to reach the **lower part of the sacroiliac joint** is typically **2 to 2.5 cm**. - This anatomical measurement is crucial for procedures like **sacroiliac joint injections**, ultrasound-guided techniques, and diagnostic imaging. - This depth applies to the posterior approach at the level of the posterior superior iliac spine (PSIS). *1 to 1 1/2 cm* - This measurement is generally **too shallow** to accurately reach the sacroiliac joint in females. - At this depth, the needle or probe would likely still be within **superficial soft tissues** (skin, subcutaneous fat, and superficial fascia). *3 to 3 1/2 cm* - This range is usually **too deep** for accessing the lower part of the sacroiliac joint in females. - This depth might penetrate **beyond the joint space** into deeper pelvic structures. *4 to 4 1/2 cm* - This measurement would be significantly **deeper** than necessary to reach the sacroiliac joint in females. - Such excessive depth could result in complications, including penetration of the joint capsule into the **pelvic cavity** or injury to **neurovascular structures**.

Question 557: Which of the following statements about the trigone of the bladder is false?

A. Mucosa is smooth and firmly adherent.
B. Developed from the mesonephric duct.
C. Lined by transitional epithelium
D. Internal urethral orifice lies at lateral angle of base (Correct Answer)

Explanation: ***Internal urethral orifice lies at lateral angle of base*** - The **internal urethral orifice** is located at the **apex** of the trigone, leading into the urethra [1]. - The **lateral angles** of the trigone are defined by the openings of the **ureters**, where they enter the bladder [1]. *Lined by transitional epithelium* - The entire **urinary bladder**, including the trigone, is lined by **transitional epithelium** (urothelium) [1]. - This specialized epithelium allows the bladder to **stretch and recoil** as it fills and empties. *Mucosa is smooth and firmly adherent* - The **mucosa of the trigone** is characteristically **smooth** and lacks the rugae (folds) found in the rest of the bladder. - It is **firmly adherent** to the underlying detrusor muscle, preventing it from folding when the bladder contracts. *Developed from the mesonephric duct* - The embryonic origin of the **trigone** is primarily from the caudal ends of the **mesonephric ducts** (Wolffian ducts). - This distinguishes it embryologically from the rest of the bladder, which develops from the **urogenital sinus**.

Question 558: Which ligament extends from the cervix and vagina to the lateral pelvic wall?

A. Broad ligament
B. Pubocervical ligament
C. Round ligament
D. Transverse cervical ligament (Correct Answer)

Explanation: ***Transverse cervical ligament*** - Also known as **Mackenrodt's ligament**, it provides a primary support for the uterus by extending from the cervix and vagina to the lateral pelvic wall [1]. - It contains the **uterine artery** and veins, contributing to both structural support and vascular supply [1]. *Broad ligament* - This is a wide fold of peritoneum that drapes over the uterus, fallopian tubes, and ovaries. - It does not directly attach the cervix or vagina to the lateral pelvic wall but rather provides a mesentery-like support for these organs [2]. *Pubocervical ligament* - This ligament extends from the cervix to the **pubic symphysis** anteriorly. - It primarily supports the anterior portion of the cervix and bladder, not extending to the lateral pelvic walls. *Round ligament* - This ligament extends from the **uterus**, through the inguinal canal, and attaches to the **labia majora**. - Its primary role is to maintain the anteversion of the uterus and it does not connect to the lateral pelvic wall in the manner described.

Question 559: What is the length of the posterior vaginal wall in centimeters?

A. Approximately 5 cm
B. Less than 5 cm
C. Approximately 7.5 cm (Correct Answer)
D. More than 7.5 cm

Explanation: ***Approximately 7.5 cm*** - The **posterior vaginal wall** is generally longer than the anterior wall. - This measurement is a common anatomical average for the posterior wall. *Approximately 5 cm* - This length is more typical of the **anterior vaginal wall**, which is usually shorter due to the cervix occupying a portion of the anterior fornix. - Therefore, this is an **underestimate** for the length of the posterior vaginal wall. *Less than 5 cm* - This measurement would be considered **unusually short** for a normal vagina, even for the anterior wall, and is incorrect for the posterior wall. - It does not represent the typical anatomical length of either wall. *More than 7.5 cm* - While vaginal length can vary, **significantly longer than 7.5 cm** is not the average measurement for the posterior wall. - This would represent an **overestimation** of the typical anatomical length.

Question 560: Which structure forms the lateral border of the ischiorectal fossa?

A. Perineal membrane
B. Obturator internus muscle (Correct Answer)
C. Gluteus maximus
D. Sacrotuberous ligament

Explanation: ***Obturator internus muscle*** - The **ischiorectal fossa** (also known as the **ischioanal fossa**) is a wedge-shaped space in the perineum, and its lateral wall is formed by the **obturator internus muscle** and its covering fascia [1]. - This muscle originates from the inner surface of the **obturator membrane** and the surrounding bone, descending through the lesser sciatic foramen to insert on the greater trochanter of the femur. *Perineal membrane* - The **perineal membrane** is a dense fibrous sheet that forms the inferior boundary of the **deep perineal pouch**. - It does not form a lateral border of the ischiorectal fossa but rather contributes to the floor of the **urogenital triangle**, anterior to the fossa. *Gluteus maximus* - The **gluteus maximus** is a large muscle of the buttock, primarily involved in extension and lateral rotation of the hip. - It lies superficial to the structures of the perineum and therefore does not form a boundary of the **ischiorectal fossa**. *Sacrotuberous ligament* - The **sacrotuberous ligament** is a strong fibrous band connecting the sacrum to the ischial tuberosity. - While it helps to define the boundaries of the **perineum** posteriorly and contributes to the stability of the **sacroiliac joint**, it does not form the lateral wall of the **ischiorectal fossa**.

Practice by Chapter

Pelvic Walls and Floor

Practice Questions

Pelvic Viscera

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Urogenital Organs

Practice Questions

Pelvic Vasculature

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Pelvic Innervation

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Male Perineum

Practice Questions

Female Perineum

Practice Questions

Pelvic Lymphatics

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Applied Anatomy and Clinical Correlations

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Gender Differences in Pelvic Anatomy

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