Medical Gross Anatomy: Pelvic Anatomy

Medical Gross Anatomy: Pelvic Anatomy

Fall 2008

Goals & Objectives

I. Goal: To understand the general anatomical design of the human pelvis through careful examination of the following objectives: The student will:

1. Understand the overall composition, morphology, & function of the human pelvis. (Each section will be described in more detail throughout the objectives. However, it will be necessary to refer to your slides for some pictures and further clarification):

a. Composition

- Pelvic girdle and floor

- Pelvic organs

- Perineum

- Neurovascular structure

b. Morphology: bowl shaped with skeletal walls, a muscular floor

c. Function: Provide space, support, and protection to viscera

- Distal urinary tract (bladder and urethra)

- Distal digestive tract (rectum and anus

- Reproductive tracts

II. Goal: To understand the anatomy of the pelvic girdle, in terms of its composition, bony landmarks, pelvic sex differences, types of fractures, and joints through careful examination of the following objectives: The student will:

1. Learn the names & characteristics of bones that form the pelvic girdle and os coxae.

a. Composition of the pelvic girdle:

- Os Coxa (2 parts- a right os coxa and a left os coxa): hip or pelvic bone of irregular shape which consists of 3 bones

· Ileum

· Ischium

· Pubis

b. Sacrum: 5 fused vertebrae

- Sacral canal: longitudinal space and protection for the spinal nerves

- Anterior and posterior sacral foramina: connect with the spinal canal for the spinal nerves

- Promontory: anterior margin of the body

c. Coccyx “tail bone”- 3 or four fused vertebrae

2. Be able to determine the anterior, posterior, medial, & lateral surfaces of the os coxae.

a. Lateral surface:

- Acetabulum: cup shaped articular surface for the head of the femur

- Obturator foramen: largest foramen in the body; membrane-covered for muscle attachment

b. Posterior margin:

- Greater sciatic notch on the superior part of the posterior margin

- Lesser sciatic notch inferior to spine

- Ischial spine separates the notches

- Posterior superior iliac spine (PSIS): terminal point of the iliac crest

- Posterior inferior iliac spine located above the greater notch

- Ischial tuberosity: rough and curved, the “sit” bone, attachment for hamstrings

c. Anterior surface:

- ASIS

- AIIS

- Superior pubic ramus

- Pubic tubercle

d. Superior Margin:

- Iliac crest: prominent superior ridge

e. Inferior margin:

- Ischial ramus

- Inferior pubic ramus

f. Medial surface:

- Iliac fossa: broad, fan shaped

- Portions of the pelvic brim:

· Arcuate line: lateral pelvic brim

· Pectin pubis: anterolateral pelvic brim

· Pubic crest: anterior brim

3. Learn the names and locations of the bony landmarks of the os coxae and will be able to specify the ones that can be palpated.

a. PSIS, ASIS, ischial tuberosity, sacrum, iliac crest

4. Learn how to correctly orient the pelvic girdle line in the anatomical position.

a. The pelvic girdle should be tilted posteriorly about 40 degrees downward

b. The ASIS and pubic tubercle line up in the same coronal plane

5. Be able to correctly sex a pelvic girdle through an analysis of observations concerning various dimorphic features of the pelvis and will know the causes for sexual dimorphism of the human pelvic girdle.

a. Female

- Appears less massive, contains less prominent markings and the greater sciatic notch is wider than the thumb

- Pubic angle is wide (>100 degrees)

· An anatomical compensation for childbirth; need for a birth canal

b. Male

- Appears more massive, contains more prominent markings, greater sciatic notch is thumb-sized

- The pubic angle is narrow (<80 degrees)

6. Know the morphological classes of the human pelvic inlet and which ones are normally expected for the male and female.

a. Male: smaller inlet

- Android: heart shaped

- Anthropoid: oval in mid-sagittal direction

b. Female: larger inlet

- Gynecoid: oval in transverse direction

- Platypelloid: more extreme transverse diameter

7. Learn the three measures of pelvic diameters.

a. Transverse: widest, largest diameter (131 mm)

b. Conjugate: promontory to pubic symphysis; smallest diameter (112 mm)

c. Oblique: diagonal (125 mm)

8. Learn the pelvic variations that would increase the probability of the need for a cesarean delivery.

a. A woman of very small frame might require a cesarean delivery if the physician feels

natural birth could harm her or the baby. The pubic angle is usually the determinant

measurement.

9. Know the locations of probable hip fractures resulting from different forces. (Dr. Terrell only briefly mentioned this in lecture. I’ll list the most common forms of hip fractures from Wikipedia for your reading pleasure

a. Many subtypes of fractures about the hip joint are colloquially known as 'hip fractures'. Although a true hip fracture involves the joint, the following four proximal femur fractures are commonly referred to as 'hip fractures'. The differences between them are important because each is treated differently.

b. Femoral head fracture denotes a fracture involving the femoral head. This is usually the result of high energy trauma and a dislocation of the hip joint often accompanies this fracture.

c. Femoral neck fracture denotes a fracture adjacent to the femoral head in the neck between the head and the greater trochanter. These fractures have a propensity to damage the blood supply to the femoral head, potentially causing avascular necrosis.

d. Intertrochanteric fracture denotes a break in which the fracture line is between the greater and lesser trochanter on the intertrochanteric line. It is the most common type of 'hip fracture' and prognosis for bony healing is generally good if the patient is otherwise healthy.

e. Subtrochanteric fracture actually involves the shaft of the femur immediately below the lesser trochanter and may extend down the shaft of the femur.

10. Learn the name, location, articulation, type of joint, and ligaments for each joint of the pelvic girdle. Include lumbosacral joint abnormalities.

a. Lumbosacral Joint @ L5-Si

- Movement at two joints

· Zygapophysical joint: synovial planar type between articular processes

· Intervertebral joint: cartilaginous type between bodies of LV & S1 with intervertebral disk

- Ligaments

· Iliolumbar ligament: LV transverse process to iliac crest

· Lumbosacral ligament: LV transverse process to sacrum

· Anterior longitudinal ligament: lumbar bodies to sacral bodies

b. Sacroiliac Joint: attaches sacrum and os coxae (at the ilium)

- Transmits forces between vertebral column and lower limbs

- Synovial type joint

- Articular surfaces are jagged to interlock which provides more strength

- Ligaments:

· Anterior and posterior sacro-iliac: broad, joint capsule

· Interosseus sacro-iliac: deep and strong; in roughened surfaces of the joint

c. Pubic symphysis: anterior at the 2 os coxae

- Cartilaginous type joint

- Ligaments:

· Superior and inferior pubic ligaments

- Stretches during childbirth

11. Be able to identify bony structures on a radiograph.

See this website for an interactive “show and tell” of the pelvic radiograph (it also has the same thing for all parts of the body!!)

http://ect.downstate.edu/courseware/rad-atlas/Pelvis/1PelRad.html

http://ect.downstate.edu/courseware/rad-atlas/index.html

III. Goal: To understand the anatomy of the pelvic cavity walls and floor through careful examination of the following objectives: The student will:

1. Understand the morphology, regions, & walls of the pelvic cavity.

a. Muscles of the female pelvis

b. Muscles of the male pelvis

2. Know the boundaries of the pelvic inlet and outlet of the true pelvis.

a. Pelvic Brim:

- False (greater) pelvis: inferior part of abdomen

- True (lesser) pelvis: forms the pelvic cavity

· Pelvic inlet: circular shaped superior opening

* Boundaries:

§ Posterior: sacrum

§ Anterior: pubic symphysis

§ lateral: distinct bony rim on pelvic bone

* Contents:

§ body of vertebra S1projects thru inlet as the sacral promontory. On each side of this vertebra, wing-like processes called the alae contribute to the margin of the pelvic inlet

§ fetus passes thru pelvic inlet during childbirth

· Pelvic outlet: diamond shaped inferior opening

· Boundaries:

* Anterior: pubic symphysis

* posterior-point of the coccyx

* lateral: ischial tuberosities

· Contents: terminal parts of the urinary and gastrointestinal tracts and the vagina pass through the pelvic outlet

3. Learn the bone, ligaments, & muscles of the lateral walls of the pelvic cavity.

a. Bone: os coxae, sacrum, coccyx

b. Ligaments: enclose sciatic notches to form sciatic foramens and stabilize sacrum with os coxae

- Sacrospinous ligament: sacrum to ischial spine (function: divides greater and lesser sciatic foramen)

- Sacrotuberous ligament: sacrum to ischial tuberosity (forms posterior border of sciatic foramens

c. Muscles:

- Obturator internus: exists through Is. sciatic foramen

- Piriformis: splits greater sciatic foramen into 2 openings

4. Learn the pelvic cavity apertures & their contents.

a. Obturator canal: small slit on the lateral margin of Obturator internus

- Obturator nerve, artery and vein exit to the medial thigh

b. Greater sciatic foramen: superior to piriformis

- superior gluteal nerve, artery, and vein

c. Greater sciatic foramen: inferior to piriformis

- Inferior gluteal nerve, artery, and vein, and sciatic nerve

d. Lesser sciatic foramen

- Obturator internus muscle

- Pudendal nerve and internal pudendal nerve, artery, and vein

5. Understand the structure that covers the floor of the pelvic cavity & outlet and its associated functions. (Pelvic Diaphragm)

a. Function: to support the pelvic viscera, resist changes in intra-abdominal pressure, and allow for voluntary control of defecation

b. Composition:

- Coccygeus: triangle shaped to ischial spine; forms and supports the posterior diaphragm

- Levator ani: bowl-shaped structure that joins in the midline

· Puborectalis: medial- forms the puborectal sling which maintains the anorectal angle and prevents defecation

· Pubococcygeus- middle

· Iliococcygeus- lateral

- Genital hiatus: a midline gap in anterior levator ani to allow for passage of urethra and vagina

6. Know the composition of, identify, and function of the pelvic diaphragm, levator ani, and the genital hiatus.

a. See above

7. Know the major structures that pass through each of the pelvic inlet and outlet.

a. See above

8. Learn the types & functions of pelvic fascia and fascial ligaments.

a. Pelvic Fascia Types:

- Parietal: lines inner muscle cavity walls and floor

- Visceral: covers pelvic visceral and vessels

- Endopelvic: filler or packing between viscera

b. Pelvic Fascial Ligaments: thickening of fascia to provide passive support for the pelvic organs

- Tendinous arch of pelvic fascia: bilateral band from pubis to sacrum along floor next to midline

· Pubovesical (puboprostatic) ligament: anterior most; connects bladder (prostate) to pubis bone

· Sacrogenital (uterosacral): posterior most; connects bladder or cervix and vagina to sacrum

- Transverse cervical ligament: attaches cervix and vagina to lateral pelvic wall

- Hypogastric sheath: conduit between lateral wall and pelvic viscera for neurovascular, uteters, vas deferens

IV. Goal: To understand the anatomy of the pelvic cavity viscera through careful examination of the following objectives: The student will:

1. Learn the ureters’ composition, function, extent, and course through the pelvic cavity.

a. Composition: retroperitoneal muscular tubes (25cm)

b. Function: transport urine via peristaltic constrictions every 25 seconds

c. Extent: only distal half is in the pelvis

- Enter pelvic inlet anterior to the bifurcation of the common iliac

- Course down in pelvic wall

- Posteriolateral sides of bladder

2. Learn the bladder’s composition, function, anatomical surfaces, stabilizing supportive ligaments, wall structure, and internal structure.

a. Morphology: rounded, 3-sided pyramid shape

b. Surfaces:

- Apex: anteriorly to top of pubic symphysis

- Base: inverted triangle posteroinferiorly

· Internal structure of base:

* Trigone: smooth triangular area

§ Ureteric orifices and sphincters: upper corners surround ureters; constrict during micturation

§ Internal urethral orifice and sphincter: encircle urethra; relaxes during micturation

* Uvula: upward bulge of Trigone from prostate

- Superior surface: balloons upward to the abdomen

- Neck: most inferior part; site of urethra attachment

c. Composition of wall:

- Rugae: distensible folds of mucosa/submucosa

- Detrusor muscle: muscular coat with 3 layers

d. Stabilizing/supportive ligaments:

- Pubioporstatic (pubovesical) ligaments: thickened endoscopic fascia from neck to pubis bones

- Median umbilical ligament: attaches apex to anterior abdominal wall

3. Learn the male urethra’s extent and segments.

a. Morphology: 20 cm; bends 2 times

b. Male urethra is divided into four segments

- Preprostatic: 1 cm at the base of the bladder to the prostate; with the internal urethral sphincter

- Prostatic urethra: 4 cm surrounded by prostate

· Urethral crest: longitudinal midline fold

· Urethral sinus (2): on side of crest

· Receives ejaculatory and prostatic ducts

- Membranous urethra: passes through perineum external urethral sphincter; made of skeletal muscle (voluntary control)

- Spongy (penile) urethra:

· In root and body of penis (corpus spongiosum)

· Bends 2x at bulb and navicular fossa

· Receives ducts from cowper’s (bulbourethral) glands

· External urethral orifice: a slit at the terminal end

4. Learn the female urethra’s extent, attachment, and why they are more susceptible than men to urinary tract infections

a. Morphology: short, about 4 cm

b. Attaches to anterior wall of vagina

c. External urethral orifice opens in the vestibule

d. The relatively short length of the urethra in women makes them more susceptible than men to bladder infection.

5. Learn the rectum’s location, boundaries, transverse folds, and anal canal features.

a. Location: most posterior pelvic organ; anterior to sacrum

b. Boundaries:

- rectosigmoid junction: to sigmoid colon at S3

- anorectal junction: to anal canal at tip of coccyx

· anorectal flexure- 80 degree angle, maintained by puborectalis sling

c. wall structure

- transverse rectal folds (3): valves that retain fecal mass when passing gas

- lacks taeniae coli and omental appendicies

d. anal canal:

- terminal part of GI tract; passes through pelvic floor and perineum

- mucosa folds

· anal columns and sinuses: longitudinal ridges and grooves that release mucous passages

- internal and external anal sphincters: smooth and skeletal muscle in two layers

- anus (anal aperture): termination of anal canal with perianal skin

6. Understand the general design and comparative anatomy of the male and female reproductive systems.

General Structure Male Female

1. Primary organ testes ovaries

2. Tract organs vas deferens uterine tubes

ejaculatory duct uterus

urethra vagina

3. Accessory glands seminal vesicle mammary

prostate paraurethral

bulbourethral vestibular

4. External genitalia scrotum& penis vulva

7. Learn the composition of the testes in terms of its protective coat, functional tissues, and conducting tubules.

a. Protective coats:

- Tunica vaginalis: closed sac of the peritoneum covering anterior aspects and sides

- Tunica albuginea: Connective Tissue capsule-lobes

b. Functional tissues:

- seminiferous tubules- highly coiled (~600): site of meiotic sperm cell formation

- Interstitial cells – between tubules and secrete testosterone

c. Additional tubules:

- rete testis- posterior testes; collecting chamber from seminiferous tubules