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3002 > 66 Pelvic diaphragm. Nerves and arteries of the pelvic cavity > Flashcards

66 Pelvic diaphragm. Nerves and arteries of the pelvic cavity Flashcards

1
Q

What is the false pelvis?

A

The posterior abdominal wall, iliacus covering the iliac bones

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2
Q

What is the true pelvis/ lesser pelvis/ pelvic cavity

A

Inferior to the arcuate lines on the iliac bones (equivalent to the pelvic brim or pelvic inlet)

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3
Q

What muscle lines the pelvic lateral wall?

A

Obturator internus

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4
Q

What muscle forms the pelvic floor/ diaphragm?

A

Levator ani

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5
Q

What is the perineum?

A
  • Diamond-shaped
  • Pudendal region below the pelvic floor/ diaphragm
  • Containing the external genitalia and urethra anteriorly with the anal canal and ischioanal fossa posteriorly
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6
Q

What are the structures which form a hammock for the pelvic visceral/ organs?

A
  • Pelvic side walls - obturator internus

* Pelvic floor/ diaphragm - elevator ani

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7
Q

What structures rest on the levator ani that forms the pelvic floor/ diaphragm?

A
  • Bladder

* Prostate

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8
Q

Perineum is divided into deep and superficial compartments anteriorly by what?

A

Perineal membrane

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9
Q

Pelvis brim/ inlet (of true pelvis) formed by?

A
  • Pubic symphysis
  • Pubic crest
  • Pectineal line on superior pubic ramus
  • Arcuate line of ilium
  • Sacroiliac joint
  • Sacral ala and sacral promontory (S1)
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10
Q

Pelvic outlet formed by?

A
  • Pubic symphysis
  • Ischiopubic ramus
  • Ischial tuberosity
  • Sacrotuberous ligament
  • Sacrum and coccyx
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11
Q

Pelvic outlet is hugely important in what scenario?

A

Childbirth

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12
Q

What triangles are the diamond-shaped perineum divided into?

A
  • Anterior: urogenital triangle

* Posterior: anal triangle

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13
Q

Changes to female pelvis?

A 
Must accommodate childbirth
• Lighter
• More rounded
• Wider
• Oval inlet
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14
Q

Changes to male pelvis?

A
  • Heavier
  • Heart shaped inlet
  • Narrowed outlet (due to more acute sub-pubic angle and enriched upon by the ischial spines)
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15
Q

Ligaments of the pelvis?

A
  1. Sacrospinous
    • Triangular
    • From ischial spine to adjacent sacrum and coccyx
  2. Sacrotuberous
    • Broader
    • From ileum, sacrum and coccyx to ischial tuberosity

Both ligaments form the greater and lesser sciatic foramina

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16
Q

What are the 3 passages through the pelvis floor?

A
  1. Greater sciatic foremen:
    • Above piriformis -Superior gluteal nerve and vessels
    • Below piriformis - Sciatic nerve + inferior gluteal vessels
  2. Lesser sciatic foramen:
    • Pudendal nerve + internal pudendal vessels
  3. Obturator canal
    • Obturator nerve and vessels
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17
Q

What is the piriformis?

A
  • From sacrum —> greater trochanter
  • Forms the posterosuperior pelvic wall
  • Divides the greater sciatic foramen
  • Innervation: S1, S2, occasionally L5
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18
Q

What is the obturator internus?

A

• From obturator membrane and adjacent bone
—> greater trochanter
• Forms the lateral pelvic wall with its overlying obturator fascia that gives origin to the pelvic floor/ diaphragm muscle (elevator ani)
• Innervation: nerve to obturator internus - L5, S1, occasionally S2

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19
Q

Tendinous arch (thickening of obturator fascia) is for the attachment of what muscle?

A

Levator ani

20
Q

What muscles make up the pelvic wall?

A
  1. Obturator internus - lateral

2. Pirifromis - posterosuperior

21
Q

What muscles make up the pelvic floor/ diaphragm?

A
  1. Coccygeus

2. Levator ani

22
Q

What is the coccygeus (aka ischiococcygeus)?

A
  • Overlies sacrospinous ligament
  • Blends with the elevator ani posteriorly
  • Innervation: S4, S5
23
Q

What parts make up levator ani? Innervation?

A
  1. Iliococcygeus:
    • Innervation: S3, S4
  2. Pubococcygeus - subdivided into:
    • Puborectalis posteriorly
    • Pubovaginalis (female) or puboprostaticus (male) anteriorly around the urogenital opening

• Innervation: S3, S4 (occasionally pudendal nerve S2, S3, S4)

24
Q

What muscles make up pubococcygeus in females and males?

A
  1. Females:
    Puborectalis + Pubovaginalis
  2. Males:
    Puborectalis + Puboprostaticus
25
Q

Importance of the levator ani as a bowl of the pelvic floor?

A
  • Supports the visceral organs
  • Maintains urinary and faecal continence
  • Weakness may cause incontinence or prolapse
26
Q

Where does each side of the levator ani meet and form?

A

Each side meets in the midline to form:

  1. Anococcygeal body (a.k.a. raphe or ligament)
  2. Perineal body (a.k.a. central tendon of perineum) - anterior to anal canal and posterior to vagina (females)
27
Q

Actions of levator ani?

A
  • Supports the pelvic viscera
  • Makes the rectoanal angle more acute aiding rectal continence
  • Augments the external anal and urethral sphincters
  • Forms a vaginal sphincter
28
Q

Lymphatic drainage of the pelvis?

A
  1. Lumbar/ para-aortic
  2. Inferior mesenteric
  3. Iliac: common, external, internal
  4. Inguinal: superficial + deep
  5. Sacral
  6. Pararectal

Lymph nodes may be found on the lateral pelvic walls alongside the obturator neuromuscular bundle

29
Q

What structures are under voluntary control in the pelvis?

A
  • Pelvic floor/ diaphragm muscles
  • External urethral
  • External anal sphincters
30
Q

Pelvic nerves overview

A
  1. Somatic - conscious, voluntary
  2. Autonomic - visceral, subconscious, involuntary as always to complement each other both sympathetic and parasympathetic
  3. Afferent (sensory) and efferent (motor) for each of the above
31
Q

What makes up the somatic pelvic nerve supply?

A
  1. Lumbo-Sacral plexus:
    • Ventral rami of spinal nerves L4, L5 (lumbosacral trunk) and S1-4 emerge from anterior sacral foramina
  2. Pudendal nerves:
    • S2-4 to perineum (sensory for external genitalia) and voluntary sphincters (motor for external urethral and external anal)
    • Direct branches from S3 + S4 to pelvic floor/ diaphragm muscles
32
Q

Pudendal nerve overview

A
  • Pudendal nerve (S2-4) passes out of the greater sciatic foramen and into the buttock
  • Curves posterior to the ischial spine, sacra-spinous ligament and coccygeus
  • Before running forwards into the perineum below levator ani
33
Q

What makes up the autonomic pelvic nerve supply?

A
  1. Sympathetic trunks:
    • Bilateral and extending into the pelvis to give sacral splanchnics
  2. Superior hypogastric plexus:
    • Sending branches to the right and left pelvic plexus (a.k.a. inferior hypogastric)
  3. Parasympathetic pelvic splanchnics: from S2, S3, S4
34
Q

The thoracic sympathetic trunk gives which splanchnics?

A
  1. Greater splanchnic nerve derived from T5 to T9 (foregut)
  2. Lesser splanchnic nerve derived from T10 _ T11 (midgut)
  3. Least splanchnic nerve derived from T12 (hindgut)
35
Q

Relationship between splanchnic servers and pelvis?

A
  • Splanchnic nerves form the preaortic (prevertebral) plexus and synapse in ganglia at the celiac trunk, SMA + IMA
  • The preaortic plexus passes into the pelvis as the superior hypogastric plexus that becomes the pelvic plexus (inferior hypogastric)
36
Q

The thoracic sympathetic trunk gives which splanchnics?

A
  1. Greater splanchnic nerve derived from T5 to T9 (foregut)
  2. Lesser splanchnic nerve derived from T10 _ T11 (midgut)
  3. Least splanchnic nerve derived from T12 (hindgut)
37
Q

Relationship between splanchnic servers and pelvis?

A
  • Splanchnic nerves form the preaortic (prevertebral) plexus and synapse in ganglia at the celiac trunk, SMA + IMA
  • The preaortic plexus passes into the pelvis as the superior hypogastric plexus that becomes the pelvic plexus (inferior hypogastric)
38
Q

What does the preaortic (prevertbral) plexus form?

A

Forms superior hypogastric plexus that branches right and left to become the pelvic plexus (inferior hypogastric)

39
Q

What is the pelvic plexus (inferior hypogastric) augmented by?

A

Sacral splanchnic nerves from the sympathetic trunk in the pelvis

40
Q

What nerves does the pelvic splanchnic nerves send?

A

Parasympathetic afferents and efferents to the pelvic plexus from S2, 3, 4

41
Q

Pelvic splanchnics?

A
  • Aka nervi erigentes
  • Afferent and efferent parasympathetic fibres derived from S2, 3, 4
  • They join the pelvic plexus that is BOTH parasympathetic (cholinergic) and sympathetic (adrenergic)
42
Q

Pelvic plexus (inferior hypogastric):
• Derived from?
• Carry which fibres
• Augmented by?

A
  • Derived from the superior hypogastric plexus that descends over the sacrum and is from the the preaortic (prevertebral) plexus
  • Therefore, essentially carrying fibres from the lesser and least splanchnic nerves T10, 11, 12
  • Augmented by sacral splanchnic nerves
  • Afferent and efferent
43
Q

Anatomical relations of pelvic plexus?

A 
Lateral to:
• rectum
• seminal vesicles + prostate (male)
• cervix + vaginal fornicles (female)
• posterior aspect of bladder

Lies in an angle between the internal iliac and inferior vesical arteries

44
Q

What is the blood supply of the pelvis?

A

• Internal iliac artery branches from the common iliac artery opposite the sacroiliac joint at the level of the L5 disc
• Internal iliac artery divides into anterior + posterior trunks
• Supplies:
- buttock + medial thigh
-posterior pelvic + abdominal walls
- pelvic viscera
- perineum
• Its gluteal branches contribute to important anastomoses around the hip - may form a collateral circulation for the lower limb

45
Q

What is the blood supply of the pelvis?

A

• Internal iliac artery branches from the common iliac artery opposite the sacroiliac joint at the level of the L5 disc
• Internal iliac artery divides into anterior + posterior trunks
• Supplies:
- buttock + medial thigh
-posterior pelvic + abdominal walls
- pelvic viscera
- perineum
• Its gluteal branches contribute to important anastomoses around the hip - may form a collateral circulation for the lower limb

46
Q

Venous drainage of the pelvis

A
  • Internal iliac vein drains equivalent areas to the artery
  • Joins the external iliac veins to from the common iliac vein that meets its opposite to form the IVC at the level of L5
  • Most pelvic viscera have an extensive venous plexus that drains into the internal iliac or internal pudendal vein
  • Anal canal is a site of port-systemic anastomosis
47
Q

Venous drainage of the pelvis

A
  • Internal iliac vein drains equivalent areas to the artery
  • Joins the external iliac veins to from the common iliac vein that meets its opposite to form the IVC at the level of L5
  • Most pelvic viscera have an extensive venous plexus that drains into the internal iliac or internal pudendal vein
  • Anal canal is a site of port-systemic anatomosis

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