Pelvic anatomy

Question 1

three main components of the bony pelvis?

Answer 1

• two hip bones (aka innominate or pelvic bones)
• sacrum
• coccyx

Question 2

functions of the pelvis?

Answer 2

• Transfer of weight from the upper axial skeleton to the lower appendicular components of the skeleton, esp during movement.
• Provide attachment for muscles and ligaments of locomotion.
• Contains and protects the abdominopelvic and pelvic viscera.

Question 3

The osteology of the pelvic girdle allows the pelvic region to be divided into two:

1. ?
2. ?

The junction between the greater and lesser pelvis is known as what?

Answer 3

1. Greater pelvis (false pelvis): superiorly, provides support of the lower abdominal viscera (e.g. ileum and sigmoid colon).
2. Lesser pelvis (true pelvis): inferiorly, contains the pelvic cavity and pelvic viscera.

Junction = pelvic inlet (its size its marked by its edge, the pelvic brim)

Question 4

State which bony components make up the borders of the pelvic inlet.

(posterior, lateral and anterior)

Answer 4

• Posterior: sacral promontory and sacral ala
• Lateral: arcuate line on the inner surface of the ilium, and the pectineal line on the superior pubic ramus (iliopectinal line)
• Anterior: pubic symphysis.

Question 5

Borders of the pelvic outlet? (posterior, lateral and anterior)

Answer 5

• Posterior: tip of coccyx
• Lateral: ischial tuberosities and sacrotuberous ligament
• Anterior: pubic arch (the inferior border of the ischiopubic rami).

Question 6

The angle beneath the pubic arch is known as what? How does it differ between men and women?

Answer 6

the sub-pubic angle (greater size in women)

Question 7

How is the female pelvis adapted for childbirth?

Answer 7

• most women have a gynaecoid pelvis (c.f. male android pelvis)
• gynaecoid: wider and broader structure yet lighter in weight; oval-shaped inlet (c.f. heart-shaped android pelvis); less prominent ischial spines (= greater bispinous diameter); greater angled sub-pubic arch (>80-90 degrees); shorter, more curved sacrum with less pronounced sacral promontory

Question 8

In addition to the bony adaptations, the ____ and ____ ligaments can stretch under the influence of ____ and increase the size of the outlet further.

Answer 8

sacrotuberous

sacrospinous

progesterone

Question 9

The lesser pelvis is the bony canal through which the fetus has to pass during childbirth. It is therefore of great importance to determine the diameter of this canal and therefore the childbearing capacity of the mother.

The diameter can be determined by a pelvic examination or radiographically. Which 2 measurements are of importance?

Answer 9

1. Obstetric Conjugate: minimum AP diameter of the pelvic inlet (narrowest fixed distance that the foetus would have to negotiate). Sacral promontory > midpoint of the pubic symphysis. Can’t be taken clinically, due to the presence of the bladder.
2. Diagonal Conjugate: sacral promontory > inferior border of pubic symphysis. Can be measured manually via the vagina.

Question 10

In addition to measuring the diagonal conjugate, a mid-pelvis check is carried out.

What is this?

Answer 10

testing for straight side walls and measuring the bispinous diameter (narrowest part of the pelvic canal).

The width of the subpubic angle at the pelvic outlet can be determined by the distance between the ischial tuberosities.

Question 11

The hip bones have which three main articulations?

Answer 11

• Sacroiliac joint: with sacrum
• Pubic symphysis: between left and right hip bones.
• Hip joint: with head of femur

Question 12

The hip bone is comprised of which three parts?

Answer 12

• ilium
• pubis
• ischium.

(together they form the acetabulum)

Question 13

Immediately above the acetabulum, the ilium expands to form the wing (or ala).

Describe the 2 surfances of the wing of the ilium

Answer 13

• Inner surface: concave, produces the iliac fossa (site of origin of the iliacus muscle).
• External surface (gluteal surface): convex, provides attachments to the gluteal muscles.

NB: superior margin of the wing is thickened, forming the iliac crest. It extends from ASIS to PSIS

Question 14

On the posterior aspect of the ilium there is an indentation known as the __ __ __

Answer 14

greater sciatic notch

Question 15

The Pubis

1. is the most ____ portion of the hip bone.
2. Consists of which 3 components?
3. Pubic body: located medially, articulates with the opposite pubic body at the __ __.
4. Together, the superior and inferior rami enclose part of the ____ foramen
5. what passes through this?
   6.

Answer 15

1. anterior
2. body, superior ramus and inferior ramus
3. pubic symphysis
4. obturator
5. obturator nerve, artery and vein pass through to reach the lower limb.

Question 16

The Ischium

1. Forms the ____ part of the hip bone. Much like the pubis, it is composed of what three components?
2. The inferior ischial ramus combines with the inferior pubic ramus forming the __ __, which encloses part of the ____ foramen.
3. The posterorinferior aspect of the ischium forms the __ __
4. Near the junction of the superior ramus and body is a posteromedial projection of bone; the __ __

Answer 16

1. posteroinferior. Body, inferior ramus and superior ramus.
2. ischiopubic ramus, obturator
3. ischial tuberosities (where our body weight falls when we sit)
4. ischial spine

Question 17

Which 2 important ligaments attach to the ischium?

Answer 17

• Sacrospinous ligament: sacrum > ischial spine, forming the greater sciatic foramen through which lower limb neurovasculature (including the sciatic nerve) transcends.
• Sacrotuberous ligament: sacrum > ischial tuberosity, forming the lesser sciatic foramen.

Question 18

anatomy of the sacrum page

Question 19

The pelvic viscera (bladder, rectum, pelvic genital organs and terminal part of the urethra) reside within the ___ cavity.

This cavity is located within the ___ part of the pelvis, beneath the __ __

Answer 19

• pelvic (aka the true pelvis)
• lesser
• pelvic brim.

Question 20

The pelvic cavity

1. lateral wall muscles?
2. inferior lining? (pelvic floor muscles aka pelvic diaphragm)

Answer 20

1. obturator internus and pirformis muscles
2. levator ani and coccygeus

Question 21

1. The pelvic floor separates the __ __ from the ____ inferiorly (region which includes the genitalia and anus).
2. Name the 2 significant ‘gaps’ through which structures pass through
3. Between the urogenital hiatus and the anal canal lies a fibrous node known as the __ __ - function of this?

Answer 21

1. pelvic cavity, perineum
2. Urogenital hiatus (urethra and the vagina in females) and rectal hiatus (anal canal)
3. perineal body - joins the pelvic floor to the perineum

Question 22

Functions of the pelvic floor muscles?

Answer 22

• Support of abdominopelvic viscera (bladder, intestines, uterus etc.) through their tonic contraction.
• Resistance to increases in intra-pelvic/abdominal pressure during activities such as coughing or lifting heavy objects.
• Urinary and faecal continence. The muscle fibres have a sphincter action on the rectum and urethra. They relax to allow urination and defecation.

Question 23

When learning about the muscles of the pelvic floor, it is important to keep in mind its funnel-shaped structure

Three main components of the pelvic floor?

Answer 23

• Levator ani muscles (largest component).
• Coccygeus muscle.
• Fascia coverings of the muscles.

Question 24

Levator Ani Muscles

1. Innervation?
2. The levator ani is a broad sheet of muscle. It is composed of which three separate paired muscles?

Answer 24

1. Anterior ramus of S4 and branches of the pudendal nerve (roots S2-4).
2. pubococcygeus, puborectalis and iliococcygeus.

Question 25

**Puborectalis** 1. U-shaped sling - where does it sling round? 2. Function? 3. What are the pre-rectal fibers?

Answer 25

1. around the anal canal. 2. Its tonic contraction bends the canal anteriorly, creating the anorectal angle (90 degrees) - helps maintain faecal continence (relaxes during defectation) 3. Some fibers of the puborectalis muscle that sling around the urethra in males and the urethra + vagina in females. V imp in preserving urinary continence, especially during abrupt increase of the intra-abdominal pressure i.e. sneezing.

Question 26

**Pubococcygeus** 1. T/F: these muscles fibres are the main constituent of the levator ani. 2. attachments?

Answer 26

1. true 2.

Question 27

**Iliococcygeus** 1. Attachments? 2. Function?

Answer 27

1. ischial spines and posterior aspect of the tendinous arch. \> coccyx and the anococcygeal ligament. 2. the actual “levator” of the three: elevates the pelvic floor and the anorectal canal.

Question 28

**Coccygeus** (aka ischiococcygeus) 1. Innervation? 2. Where does it lie in relation to the levator ani muscles? 3. Attachments?

Answer 28

1. anterior rami of S4 and S5. 2. posteriorly 3. It originates from the ischial spines and travels to the lateral aspect of the sacrum and coccyx, along the sacrospinous ligament.

Question 29

**Pelvic Floor Dysfunction** 1. During the second phase of childbirth, the levator ani muscles and/or the _____ nerve are at high risk of damage. _____ and ___ muscles are the most prone to injury due to them being situated most medially. 2. Injury to these muscles can lead to what problems? 3. Name some of the risk factors for prolapse

Answer 29

1. pudendal, Pubococcygeus, puborectalis 2. urinary stress incontinence and rectal incontinence, prolapse 3. Age, multiple vaginal deliveries, FH of pelvic floor dysfunction, BMI, chronic coughing (e.g from a lung disorder)

Question 30

1. Name the major artery of the pelvis. 2. It originates at the bifurcation of the __ \_\_ artery into its internal and external branches at approximately which vertebral level? 3. The artery descends inferiorly, crossing the pelvic inlet to enter the lesser pelvis. During its descent, it is situated ____ to the external iliac vein and obturator nerve. Where does it divide into anterior and posterior trunks? 4. Name some branches of the anterior trunk (supplies the pelvic organs, perineum and gluteal and adductor regions of the lower limb) 5. The posterior trunk branches supply what? 6. There are typically which 3 branches?

Answer 30

1. Internal iliac 2. common iliac, L5-S1. 3. Medially, at the superior border of the greater sciatic foramen 4. inferior vesicular artery, obturator artery, uterine artery, vaginal artery, internal pudendal artery, middle rectal artery, inferior gluteal artery \> ***others?*** 5. the lower posterior abdominal wall, posterior pelvic wall and gluteal region 6. iliolumbar artery, lateral sacral arteries, superior gluteal artery

Question 31

**Minor arteries of the pelvis** 1. the ___ artery is the major gonadal artery in females 2. it arises from the __ \_\_. It divides into an ___ branch and ___ branches 3. Which artery is this describing: is the terminal continuation of the inferior mesenteric artery. Gives rise to branches that supply the rectum. 4. Describe the relationship between the ureters and uterine arteries

Answer 31

1. ovarian 2. abdominal aorta. Ovarian, tubal 3. superior rectal artery 4. uterine artery crosses the ureters approximately 1cm lateral to the internal cervical os (take care not to damage the ureters when clamping the uterine arteries during a hysterectomy). ‘Water under the bridge’.

Question 32

1. Name the 3 major vessels involved in venous drainage of the pelvis 2. Which is is responsible the majority of pelvic venous drainage? 3. The external iliac vein is a continuation of which vein? It arises when the femoral vein crosses underneath the __ \_\_ 4. The external iliac vein receives which 2 veins? 5. T/F: the tributaries of the internal iliac vein correspond with the branches of the internal iliac artery 6. Name the tributaries of the internal iliac vein

Answer 32

1. External iliac vein, internal iliac vein, common iliac vein 2. Internal iliac vein 3. The femoral vein. Inguinal ligament. 4. Inferior epigastric and deep circumflex iliac veins 5. True – with the exception of the iliolumbar vein 6. Vesical veins, Lateral sacral veins, Obturator vein, Uterine and vaginal veins, Internal pudendal vein, Middle rectal vein, Superior and inferior gluteal veins