A. Pelvis 1. Name the Innominate Bones

1. Name the innominate bones (those that are fused together and don’t move).

There are two innominate bones, and each innominate bone contains three bones that are fused together. The three bones are the ilium, ischium, and pubis. They are placed laterally (on the side) on the pelvis, and each innominate bone has an acetabulum where the three bones fuse around it. The acetabulum is the concave surface of the pelvis, where the head of the femur meets with the pelvis to form the hip joint.

2. Describe the sacrum.

The sacrum is a triangular shaped bone that has a superior base and an inferior apex. The anterior side of the sacrum is concave, while the posterior surface is convex. The sacrum consists of five vertebrae fused together. Attached by the sacroiliac joints, the sacrum lies between the innominate bones.

The sacral promontory is the anterior and superior edge of the sacrum’s base (first sacral vertebra), and it protrudes forward forming the concavity. This protrusion into the cavity of the pelvis reduces the anteroposterior diameter of the pelvic inlet. If the sacral promontory was pushed backwards, it would widen the pelvic inlet and increase its diameter.

3. Describe the coccyx.

The coccyx, or tailbone, is the final segment of the vertical column. It is also triangular and looks like a shortened tail at the bottom of the spine. It is composed of four vertebrae. The sacrococcygeal joint is between the superior side of the first coccygeal vertebra and the inferior side of the fifth sacral vertebra.

4. Give the difference between the primary and accessory ligaments.

There are four primary ligaments and two accessory ligaments.

The four primary ligaments are:

1. The anterior sacroiliac ligament - these are short and transverse, running from the ilium to the sacrum, more specifically, the preauricular sulcus of the ilium. The preauricular sulcus is observed as a female characteristic in the pelvic, and it is a groove near the sacrum. This ligament inserts into the anterior side of the ala of the sacrum. 2. The interosseous sacroiliac ligament - are short and transverse bands of ligaments that lie deep to the posterior ligament. The run from the posterior surface of the ilium, horizontally to the sacrum. 3. The short posterior sacroiliac ligaments - are strong transverse bands that lie behind the interosseous ligaments. 4. The long posterior sacroiliac ligaments - are each attached from the posterior superior iliac spine to the tubercles of the third and fourth sacral vertebrae.

The two accessory ligaments are:

1. The sacrotuberous ligaments - are long ligaments originating from the ischial tuberosity (sit bones) and inserting into the posterior inferior iliac spine and posterior superior iliac spine. This ligament is also known as an extension to the posterior sacroiliac ligament. Basically, it is in the posterior inferior pelvis, between the sacrum and sit bones. 2. The sacrospinous ligament - is a triangle shaped transverse ligament, and is attached from the fifth sacral and first coccygeal vertebrae to the ischial spine.

5. What is the sacroiliac joint? The sacroiliac joint or SI joint is between the ilium bones and the sacrum of the pelvis. It is a synovial joint (an egg white like fluid to reduce friction between cartilage during movement), and permits a small degree of movement. The SI joint also is contained by a capsule (an envelope surrounding a synovial joint) that is weak. The joint’s stability is maintained by muscles and ligaments around it.

6. Describe the Symphysis Pubis.

The symphysis pubis is a secondary cartilaginous joint located near the left and right superior rami pubic bone, near the midline of the body. This joint is not a synovial joint, so it does not contain a capsule. There is very little movement from this joint, and it is in front of and below the bladder. Below the symphysis pubis is the arcuate pubic ligament, which is a strong inferior ligament in the pubic arch.

7. What is the sacrococcygeal Joint and why is it important?

The sacrococcygeal joint lies between the inferior fifth sacral vertebrae and the superior first coccygeal vertebrae. It is a synovial joint, so there is movement involved, allowing for extension and flexion of the sacrum and coccyx. During parturition, when there is extension, it allows the fetal head to fit and engage more due to the increased anteroposterior diameter of the pelvic outlet. If coccyx didn’t extend back, it would be a much tighter outlet for the baby to pass through. If this is over extended, the small cornua, (connecting bone between the coccyx and sacrum) may break. Due to it being a synovial joint, it is surrounded by a weak capsule that must be reinforced by anterior, posterior, and lateral sacrococcygeal ligaments

8. How does the mobility of the pelvis change during pregnancy?

Progesterone and relaxin both increase the flexibility of the sacroiliac joints and the symphysis pubis during pregnancy. The joints also undergo hyperemia (an increase in blood flow to different tissues) and ligament softening. Excessive movement of the pubic symphysis can lead to pain and difficulty in walking. The pubic bones may separate one to 12 millimeters. The pelvis is an incredible structure, because it is designed for its flexibility to allow a fetus to smoothly pass through it, allowing bones to move and extend.

9. What are the differences in the male and female pelvis?

The female and male pelvis are both born the same, and develop at puberty in the presence of hormones and gonads. There are many differences between the two, and can be easily noticed and differentiated. The female pelvic cavity is much shallower compared to a deep male pelvic cavity. This allows for a quicker passage for the fetus. The female iliac crest with respect to the pelvis is shorter, while the males is higher and taller. The female pelvic bones are lighter and thinner than the denser rougher males’. The pubic arch differences in subpubic angles vary, where the females is much wider, typically at an 80 degree angle or above, and the males is less than or equal to 70 degrees. The male arch is closer to the shape of a “V,” while the female is like the shape of an “L.” The female pelvic inlet is an oval shape, while the males is heart-shaped. The sacrums are different too, where the female sacrum is wider, shorter, and curved, with the coccyx being straighter. The male sacrum is longer, and straighter, and the coccyx curves forward.

10. Explain how the adolescent female and adult female pelvis differ. How and why does this happen?

The pelvis of an adolescent girl is much smaller than that of a mature woman. An adolescent girl’s growth in height is at a different rate than her pelvic growth. For instance, within the first year after she has her first menstrual cycle, her stature will rapidly decelerate, and stops within one or two years. While her pelvic basin grows much more slowly and steadily during late adolescence. Her pelvis will also change shape, from an anthropoid (resembling the male pelvis) to a gynecoid (more circular, narrower female shape). A woman's complete growth and development of her pelvis isn't indicated by a mature reproductive system, or peak adult statute.

B. Pelvic Floor

1. What is the pelvic floor and what are its functions? The pelvic floor is a funnel-shaped structure and divides the pelvic cavity above and the perineal space below. It is composed of muscle fibers of the levator ani, the coccygeus muscle, and is covered completely by connective tissue parietal fascia. The urethra and vagina pass through an anterior gap called the urogenital hiatus. The rectum and anal canal pass through the rectal hiatus, which is posterior to the urogential hiatus.

It’s functions are to:

1. Support the pelvic viscera in humans. The pelvic viscera includes the bladder, distal ends of the ureters, rectum, and reproductive organs. 2. Contract the diaphragm muscles, abdominal wall, and pelvic floor all together in order to build effective intra abdominal pressure. 3. Help the anterior rotation of the fetal presenting part during parturition, and direct it downward and forward along the birth canal.

2. Part of the pelvic floor consists of the Levator Ani. This is further subdivided into two main muscles. One of these is the pubococcygeus muscle. What is this muscle and what does it do/why is it important? Ensure you cover all three sections completely.

The pubococcygeus muscle is a hammock-like muscle that stretches from the pubic bone to the coccyx forming the floor of the pelvic cavity and supporting the pelvic organs. It is a very important, dynamic, and specialized part of the pelvic floor. It’s in the midline of the pelvis and is perforated by the urethra, vagina, and rectum. This muscle is often damaged during delivery. It originates from the anterior medial portion of the pubis, and inserts posteriorly to the sacrum. It contains three different sections: the pubovaginalis, puborectalis, and pubococcygeus proper.

1. The pubovaginalis muscle - is the most medial section, and is shaped like a horseshoe with its opening facing anteriorly. It acts as a sling, wrapped around the vagina to support the female pelvic organs. It supports the vagina because the vagina itself helps to support the uterus and appendages, bladder and urethra, and rectum. This muscle inserts into the sides and back of the vagina and ends at the central point of the perineum. Uterovaginal prolapse is likely to happen as a result of tearing or overstretching the pubovaginalis. This muscle also acts as the vaginal sphincter, and vaginismus, is the condition of it spasming. 2. The puborectalis muscle - is the most intermediate part and loops around the anal canal and rectum. Between the external and internal sphincter ani, lies the puborectalis, and also within the anococcygeal body. The puborectalis plays a small role in supporting the pelvic structures, and the rectum does not support the pelvic viscera, so its main function is to suspend the rectum. It acts as an auxillary sphincter for the anal canal by controlling the descent of feces. The anococcygeal junction is located under the pubic symphysis, and when this ligament is pulled forward, the puborectalis slows the descent of feces by increasing the anorectal flexure. 3. The pubococcygeus proper - is a Y-shaped lateral muscle that inserts into the sides of the coccyx. When it contracts it pulls the coccyx forward, like the puborectalis, to control the descent of feces.

3. What happens to the pelvic floor during parturition? Why do you think this is the case?

The pelvic floor muscles need to stretch and expand in order to allow for adequate birth without tearing or an episiotomy to be performed. The pubococcygeus needs to stretch three times its original length during birth. The central point of the perineum begins to thin out as the presenting part has descended to a proper level during birth. All the muscles relax, like the levator ani muscles and the anal sphincter, which contribute greatly to a smooth partuition. When these muscles are in stress, they are tense, and do not allow for smooth passage. This happens because as the baby, uterus, placenta, and more grows, there's much more pressure against the pelvic floor, and a lot less room within the abdomen. Everything is more condensed. The abdominal muscles are weakened and stretched out, so they aren't supporting the pelvic viscera as much as usual. During birth, the uterus strongly contracts, pushing against the pelvis, causing these changes. The pelvic floor muscles and openings need to regain their tone and reduce in size again postpartum.

C. Perineum

1. What is the perineum and what are the two triangles?

The perineum is a diamond shaped space that is superior to the pelvic floor, and lateral to the bones and ligaments of the pelvic outlet, the subpubic angle, ischiopubic rami, ischial tuberosities, sacrotuberous ligaments, and coccyx. It is also inferior to the skin and fascia. It is divided into two triangles which are the urogenital triangle, and the anal triangle. A transverse band made of the transverse perineal muscles and the urogenital diaphragm separates these triangles. Imagine two triangles bases touching each other, forming a diamond shape, or just imagine a vertical diamond with a line touching the left vertex to the right vertex. When looking at the inferior view of a woman's perineum, the urogenital triangle is the top triangle, and the anal triangle is the bottom triangle.

The urogenital triangle is the anterior part of the perineum. It has 3 vertices, and the top vertex is at the pubic symphysis, while the bottom left and right are at the ischial tuberosities.

The anal triangle has its bottom vertice at the coccyx, and the top left and right at the ischial tuberosities as well. This is the posterior triangle of the perineum.

2. What anatomical parts are contained within the Urogenital Triangle?

The urogenital triangle, from top down, contains: the clitoris, external urethral orifice (opening), vaginal orifice, bulbs of the vestibules (two elongated masses of erectile tissues on each side of the vaginal opening, a.k.a. Clitoris bulbs), ischiocavernosus muscle, bulbocavernosus muscle, greater vestibular (Bartholin’s) gland (also located on either side of the vaginal orifice and secretes a mucous substance that lubricates the vagina), and the superficial transverse perineal muscle. Deeper, it also contains the superficial and deep perineal pouches, blood vessels, nerves, lymphatics, and the urogenital diaphragm.

3. What is the urogenital diaphragm? What does it contain?

The urogenital diaphragm (triangular ligament) resides within the urogenital triangle, and it is a layer of the pelvis that separates the deep perineal sac from the upper pelvis. The diaphragm is made of muscle tissue covered by fascia, a band or sheet of connective tissue, primarily collagen, beneath the skin that attaches, stabilizes, encloses and separates muscles and other internal organs. It originates at the arcuate pubic ligament, and inserts at the ischial tuberosities. The two layers of fascia fuse and become superficial, forming the superior transverse perineal ligament, and they join in the center of the perineum (perineal body).. The urogenital diaphragm contains two muscles, the deep transverse perineal and the sphincter of the membranous urethra. It also has a thin and weak superior layer of fascia, and a strong inferior layer of fascia.

4. What is the job of the Sphincter of Membranous Urethra?

The job of the sphincter of membranous urethra is to expel the last remaining drops of urine. Its fibers are involuntary and surround the urethra, acting as a sphincter. It lies between the two fascial layers of the urogenital diaphragm, so between the superior and inferior fascia’s. The sphincter of membranous urethra is also known as the compressor of the urethra.

5. What is the Anal Triangle and what does it contain?

The anal triangle is is the posterior “upside down” traingle of the perineum and contains everything related to the anus, and more. The triangle connects from the two ischial tuberosities, to the coccyx. It contains the anococcygeal ligament, ischiorectal fossa, the anal canal and its sphincters, blood vessels, lymphatics, and nerves.

6. What are the two jobs of the Sphincter Ani Externus? There are three parts to the sphincter ani externus: the subcutaneous, superficial and deep. All of these layers start at the tip of the coccyx and the anococcygeal ligament, ending at the perineal body. The subcutaneous layer surround the anal orifice, the superficial is the middle layer after the subcutaneous, and the deep portion is the last (third) layer outside the anal orifice. All of these layers move laterally, side by side, not deep within the body (but they do go deep as well.. The superficial layer has voluntary fibers that will act during defecation or in an emergency. While the deep portion is an involuntary muscle, acting as a sphincter for the anus. This part blends with the levator ani muscle and the internal anal sphincter.

7. What comprises the Perineal Body and what is the biggest issue with this area in childbirth?

The perineal body is also called the perineum and it is the space between the vagina and anus. The many muscles that meet to form this structure are the sphincter ani externus, superficial and deep transverse perineal muscles, two levator ani muscles, and the bulbocavernosus muscle. During childbirth, the perineum is often torn, and there are four degrees of perineal tearing/ lacerations.

The first degree is the least severe tear, and it mainly injures the first layer of tissues around the vagina and perineum. The second degree tear is the most commonly seen tear, and it is a bit larger, and affects deeper through the skin and into the muscular tissue of both the vagina and perineum. The third and fourth degree tears and much more severe, tearing from the vagina to the anus. The third degree with injure the muscular tissue of the perineum, and the anal sphincter muscles. Anal sphincter muscles control your bowel movement, so these tears should be done by a doctor. The fourth degree tear is the least common tear, and it tears past the sphincter muscles, and into the rectum. It is the most severe tear.

D. Uterus and Vagina

1. What is the uterus? Describe its size, purpose, and location.

The uterus is a female hormone-responsive secondary sex organ of the reproductive system. It is in the shape of an inverted pear, is very muscular and located between the bladder and the rectum. The bladder is in anterior, and the rectum is posterior. The uterus is entirely within the pelvis, and as it grows by the fourth month of gestation, it extends into the abdominal region. By the third month of gestation, the uterus is globular, and from seven months to term, it is pyriform again.

The uterus grows from 7.5 x 5.0 x 2.5 centimeters to 28 x 24 x 21 centimeters. It goes from 30 to 60 grams, to 1000 grams (roughly 2.2. pounds) at the end of gestation. It changes from a large organ to a large sac.

It’s main function involves the reproduction cycle, fertility, and childbearing. The uterus accepts the fertilized ovum, which will turn into a fetus, and houses/supports it.

2. Name the three layers of the uterus.

The three layers of the uterus are the perimetrium, myometrium, and endometrium.

3. Describe each of the three uterine layers.

The perimetrium is the outermost layer, almost like a covering of the uterus. The posterior side of the uterus is completely covered by the perimetrium, and the anterior side only partially.

The myometrium is the “middle” lining. It is made of smooth muscle cells, making it very muscular. This layer's main function is to execute uterine contractions. The myometrium and the fundus of the uterus are the two places that grow the most during gestation. The main factor of uterine growth during the first half of pregnancy is hyperplasia (new muscle fibers forming). Then in the second half, hypertrophy (enlargement of existing myometrial cells) takes place. At term, there are an estimated 200 billion cells. Four major proteins compose the myometrial fibers: myosin, actin, tropomyosin, and troponin. Blood vessels increase in size and number as well, and connective tissue overgrows. The lumen of these vessels also become larger and the walls become thinner.

The myometrium has three layers:

1. An inner layer whose fibers run in a circular pattern. 2. A middle layer that is thick and contains fibers that are filled with blood vessels. The pattern is a sort of “X” shape or interlacing pattern. This layer contracts and retracts, kinking the blood vessels and controlling postpartum hemorrhage 3. An outer layer composed of longitudinal fibers.

The endometrium is directly attached to the myometrium and is the innermost layer and contains many blood vessels. The fertilized egg will implant itself in the endometrium. It will extend itself and form the maternal side of the placenta.

The endometrium has two decidua layers:

1. A decidua functionalis - the top/outer layer 2. A decidua basalis - the deep/inner layer

Decidua means mucosal lining.

4. What is the isthmus? What role does it play and how does it change in pregnancy?

The isthmus is the smallest and most constricted region of the uterus. It is five to seven millimeters in length, and it is superior to the internal os. In the uterus’ normal state. The isthmus is pretty insignificant. But, during pregnancy, it plays an important role of increasing in length as the uterus grows. It increases up to 25 millimeters, becoming compressible and soft.

When the ovum implants in the upper uterus, the enlarging embryo at three months of gestation will grow into the isthmus. Because of this, the isthmus will expand to make space for the developing embryo. The more the isthmus grows, the more it morphs into the general uterine cavity. This changes the uterine shape from a pear to globular. Because the isthmus is between the upper uterus and cervix, as it expands it becomes the lower segment of the uterus during labor. The anatomical internal os then, becomes the physiologic retraction ring. After month seven, the uterus becomes pyriform again. The lower uterine segment makes up ⅓ of the entire uterus, and ist contractions are very weak compared to the uterine body.

5. Explain the role of the cervix and vagina in pregnancy as well as the different features and layers.

The cervix is a short cylinder shaped neck of connective tissue and muscle fibers. It connects the vagina and the uterus, and the vagina is inferior to it. In the non-pregnant state, the cervix is firm and hard. During pregnancy, the cervix becomes softer overtime due to selling, increased vascularity, and hyperplasia of the glands. The compound tubular glands (branched out tubed glands), become overactive, generating large amounts of mucus. This mucus accumulates and thickens within the cervical canal to form the mucus plug. The mucus plug is a protective collection of mucus sealing the cervical canal. It acts as a barrier keeping unwanted bacteria from traveling into the uterus. Towards the end of pregnancy, the internal os disappears to merge with the cervical canal (which also becomes part of the lower uterine segment), only leaving the external os.

The vagina is the muscular genital tract in females. The outer vaginal opening is normally covered by a membrane called the hymen. Inferiorly the vagina is surrounded by the vulva. Posterior is the rectum. Superior to it is the uterus, and the bladder is anterior. The cervix protrudes into the deep section of the vagina, and divides the vaginal vault into four fornices: posterior, anterior, and two lateral fornices. Because of the way the cervix enters the vagina (through the anterior wall), the posterior fornix is deeper. The anterior wall is 6-8 centimeters deep, shorter than the 7-10 centimeter deep posterior. The vaginal wall has four layers:

1. Mucosa - the epithelial layer 2. Submucosa - the second layer, and rich in blood vessels 3. Muscularis - the third layer 4. Tunica adventitia or Paracolpium - the fourth and outer layer that connects the vagina to the surrounding structures and is made of connective tissues.

The vagina during pregnancy becomes more vascularized, thickens, and lengthens its walls. It increases secretion as well. This all helps it reach greater distention than the non-pregnant state can already handle.

6. What is uterine prolapse? Discuss the complications, treatments, etc with this abnormality.

Uterine prolapse is a condition where the internal supports, such as the pelvic floor muscles, of the uterus become weak and are no longer strong enough to support the uterus. The uterus, cervix, vagina, or bladder can descend into the vagina or in more severe cases, bulge out of the vagina. Uterine prolapse during pregnancy is rare, but can cause immense trouble, because of course, the uterus can not be completely out of the vagina and carry out a pregnancy to term. The uterus rises out of the pelvis by the end of the fourth month, and if it doesn't, then it's usually the cervix that protrudes through the vagina.

Complications of uterine prolapse are:

During antepartum:

1. Premature labor and abortion 2. Cervical swelling, ulceration and sepsis 3. Urinary retention and infection 4. Possible consideration of prolonged bed rest

During intrapartum:

1. Cervical dilation possibly beginning outside of the vagina 2. Swelling and fibrosis may cause cervical dystocia 3. Lacerations of the cervix 4. Uterine rupture due to labor obstruction

During postpartum:

1. Puerperal infection is increased. This is a bacterial infection following childbirth in the uterus and surrounding areas after birth.

Treatment of uterine prolapse are:

During antepartum:

1. Bed rest in the trendelenburg position to reduce swelling and permit repositioning of the uterus. This position is the body laid on its back and on a 15-30 degree incline with the feet elevated above the head. 2. The use of a pessary to maintain the position of the uterus. The pessary is a device inserted into the vagina to treat prolapse and maintain the location of organs in the pelvic area.

During intrapartum:

1. A normal vaginal delivery is usually carried out, but arrest of progress may ensue. 2. Several procedures are considered and executed if cervical dystocia develops: a. Duhrssen incisions of the cervix, which are three surgical incisions of the cervix. b. Augmentation of labor using pitocin.

During postpartum:

A pessary will be used to support the ligaments and elevate the uterus.

7. What are the three main uterine complications in labor and delivery?

Three main uterine complications in labor and delivery are:

1. A retained placenta - a condition in which all or part of the placenta or membranes remain in the uterus during labor. 2. Subinvolution of the placental site - when the uterus does not return to its normal size. 3. Postpartum hemorrhage.

8. What is a unicornuate and bicornuate uterus?

A unicornuate uterus has a normal vagina and a single normal tube, in most cases. It has a single horn, and the other half is missing or rudimentary. Many patients with this abnormality will also have a missing kidney on the side of the absent horn. An incompetent cervix is also often present, and it is very difficult to conceive.

A bicornuate uterus is another uterine anomaly where there is a deep indentation at the fundus of the uterus. It is heart-shaped and there is a division down the middle of the uterus up to the internal os.