Perineum Anatomy Quiz

The most likely explanation for the correct answer is that the two pelves depicted have characteristics that are typically associated with male and female individuals. This could include differences in the shape, size, and structure of the pelvis, as well as the presence or absence of certain features such as the pelvic inlet and outlet. These differences can be used to determine the sex of an individual based on skeletal remains.

The rectouterine pouch is a peritoneal recess located between the rectum and the uterus. It is also known as the pouch of Douglas. This pouch is formed by the reflection of the peritoneum from the posterior wall of the uterus to the rectum. It is an important anatomical landmark in gynecology and can be accessed through the anterior vaginal fornix during certain procedures. The rectouterine pouch does not contain the ovaries and its main function is not to provide support to the bladder.

The correct answer is the ischial spine. In an AP pelvic radiograph, the ischial spine appears as a bony prominence located posteriorly and medially to the ischial tuberosity. It is an important landmark used in pelvic measurements and is also a reference point for identifying certain pelvic fractures. The sacrotuberous ligament is not visible on an AP radiograph, and the iliac tubercle is located on the iliac crest, not the ischial spine. A posteriorly dislocated femoral head would be seen as a displacement of the femoral head from its normal position in the acetabulum.

The sacrotuberous ligament is a strong ligament that attaches from the sacrum to the ischial tuberosity. Its main function is to resist posterosuperior rotation of the sacrum, which means that it prevents the inferior aspect of the sacrum from moving posteriorly and superiorly. This helps to stabilize the sacrum and maintain proper alignment of the pelvis. The other statements in the question are incorrect and do not accurately describe the function or location of the sacrotuberous ligament.

Spondylolisthesis is the most likely explanation for the abnormally prominent spinous process of the L5 vertebra compared to the superior lumbar vertebrae. Spondylolisthesis is a condition where one vertebra slips forward over the vertebra below it. This can cause the spinous process to appear more prominent. Fracture of the body of L5 would likely cause more severe symptoms and would be less likely in a pregnant woman without a history of trauma. Vertebral canal tumor and spina bifida would typically present with different symptoms. Kyphosis refers to excessive forward curvature of the spine, which would not explain the specific finding of the prominent spinous process.

The given statement is incorrect because pelvic parasympathetic innervation does not stimulate ejaculation. Ejaculation is primarily controlled by the sympathetic nervous system. The parasympathetic innervation of the pelvis is responsible for stimulating bladder contraction for urination and rectal contraction for defecation. The fibers of pelvic parasympathetic innervation are indeed accompanied by visceral afferent fibers from pelvic viscera.

All of the statements you provided are correct. Here’s a brief explanation for each:

The pelvic girdle is indeed composed of the right and left hip bones and the sacrum.

In infants and children, the hip bone is composed of three separate bones—the ilium, ischium, and pubis.

The ala of the ilium helps to form the acetabulum.

The ischial spine separates the greater and lesser sciatic foramina.

The pelvic brim separates the greater (false) and lesser (true) pelves. 

The uterine artery passes superior to the ureter at the lateral fornix of the vagina. This is the correct answer because the uterine artery is located above the ureter and runs along the lateral fornix of the vagina. This anatomical relationship is important to note as it helps to avoid injury to the ureter during surgical procedures involving the uterus or surrounding structures.

The pelvic pain line characterizes pelvic pain referral areas based on the inferior limit of peritoneum. This means that it identifies the areas where pain is felt in the pelvis based on the location of the peritoneum. It is not limited to childbirth or hysterectomy, but rather applies to any pelvic pain. It is not specific to a particular vertebral level, but rather focuses on the peritoneum as a reference point for identifying pain referral areas.

The correct answer is that the umbilical artery does not give rise to the obturator artery. The umbilical artery is a branch of the internal iliac artery, and it gives rise to the superior vesical arteries. It forms the medial umbilical ligament postnatally, and it can have both patent and occluded parts.

During pregnancy, the hormone relaxin is released, which relaxes the pelvic ligaments. This allows for increased mobility and flexibility in the pelvis, enabling it to accommodate the growing fetus and facilitate childbirth. The transverse diameter of the pelvis also increases to provide more space for the baby to pass through during delivery. Additionally, the amount of pelvic rotation around the sacrum increases, aiding in the birthing process. The coccyx, or tailbone, is permitted to move more posteriorly to further accommodate the baby's passage. However, the true distance between the sacral promontory and the posterosuperior aspect of the pubic symphysis does not increase during pregnancy.

The transverse cervical (cardinal) ligament is a fibrous band that provides support to the uterus and attaches to the lateral wall of the pelvic cavity. It is composed of subperitoneal endopelvic fascia, which makes it strong and capable of holding sutures during pelvic surgery. However, it does not provide an attachment for the levator ani, which is a different structure responsible for supporting the pelvic organs and maintaining continence.

The pelvic diaphragm is not synonymous with the levator ani. The pelvic diaphragm is a group of muscles that forms the floor of the pelvic cavity and separates it from the perineum. It helps maintain urinary and fecal continence by supporting the organs in the pelvic cavity. The levator ani is a specific muscle within the pelvic diaphragm that plays a role in supporting the pelvic organs and controlling continence, but it is not synonymous with the entire pelvic diaphragm.

The correct answer is "Most of its branches exit the pelvis through the lesser sciatic foramen." This statement is incorrect because most of the branches of the sacral plexus actually exit the pelvis through the greater sciatic foramen, not the lesser sciatic foramen. The lesser sciatic foramen is primarily traversed by the tendon of the obturator internus muscle and the pudendal nerve.

The levator ani is a group of muscles located in the pelvic region. It plays a crucial role in maintaining continence and supporting the organs in the pelvis. During coughing, the levator ani contracts actively to provide additional support to the pelvic organs and prevent any leakage of urine or feces. This contraction helps to maintain continence and prevent any involuntary release of urine or feces during coughing episodes. Therefore, the statement "actively contracts during coughing" is the correct explanation for the given answer.

The hypogastric plexuses are a network of nerves located in the pelvis. They are responsible for conveying sympathetic fibers to the pelvic viscera. This means that they transmit signals from the sympathetic nervous system, which is responsible for the fight-or-flight response, to the organs in the pelvic region. These sympathetic fibers help regulate various functions in the pelvic viscera, such as blood flow, digestion, and bladder control.