Pelvic Fascia, Rectum & Anal Canal; Urinary Bladder & Female Urethra

Question 1

Identify the structures indicated in pink & green.

How are they formed?

What are their functions?

Answer 1

• Green: Pararectal fossae
• Pink: Paravesical fossae
• The peritoneum reflects laterally over the bladder & the rectum forming the shallow fossae
• Allow for bladder & rectum to distend when needed

Question 2

What peritoneal pouches exist in the female & male bodies respectively?

How are they formed?

Answer 2

• Peritoneum continues posteriorly & reflects over the rectum making these pouches
• Female
  
  • vesicouterine pouch
    
    • betweent the bladder & uterus
  • rectouterine pouch (pouch of Douglas)
    
    • between rectum & uterus
• Male
  
  • rectovesical pouch
    
    • between rectum & bladder/prostate

Question 3

What structures are depicted by the blue & yello lines?

How are the different?

They are what component of the pelvic fascia?

What structure exists between them?

Answer 3

• Membranous component
  
  • Visceral layer
    
    • directly ensheaths pelvic organs
  • Parietal layer
    
    • lines inner aspect of the pelvic floor & pelvic walls
    • continuous with transverslis fascia of the abdomen
• Between those two membranous layers is the endopelvic fascia
  
  • ​loose areolar tissue

Question 4

What is the function of septa and ligaments in the pelvic fascia?

Answer 4

• Septa: are located between viscera (rectovaginal septum, rectovesical septum)
• ligaments help suspend viscera (puboprostatic ligament, pubovesical ligament)

Question 5

What are the two potential spaces in the endopubic fascial?

What are the septa between viscera?

Answer 5

• Potential space (Female + Male)
  
  • retropubic space
    
    • between pubis & bladder
  • retrorectal space
    
    • between rectum & sacrum
• Septa - between viscera
  
  • Female: rectrovaginal septum
    
    • between rectum & vagina
    • prevents rectum from bulging in towards the vagina
  • Male: Rectovesical septum
    
    • between rectum & prostate
    • helps support those two organs

Question 6

What are the ligaments of the pelvic fasia?

Answer 6

• Female
  
  • pubovesical ligament
    
    • from pubis to bladder
• Male
  
  • puboprostatic ligament
    
    • from pubis to prostate

Question 7

Describe the relationship between the peritoneum & the rectum

Answer 7

• Superior 1/3
  
  • anterior
  • lateral
• Middle 1/3
  
  • anterior
• Inferior 1/3
  
  • none

Question 8

How long is the rectum?

What are its functions?

Answer 8

• Length: 12-15 cm
• Function
  
  • accumulate & temporarily store feces
  • defecation adn fecal continence
  • water absorption

Question 9

What are the difference between the anatomy of the colon & rectum?

Answer 9

• Rectum
  
  • no tenia, haustra or appendices
  • tenia coli from sigmoid colon spread out to form longitudinal outer layer or smooth muscle
    
    • this occurs at the rectosigmoid junction ~S3

Question 10

Describe the course of the rectum

Answer 10

• Two anterior-posterior flexure
  
  • Sacral flexure
    
    • follows curve of sacrum (concave anteriorly)
  • Anorectal flexure
    
    • sharp posterioinferior bend
    • rectum is ending, anal canal is beginning
    • formed by puborectalis muscle
• 3 lateral flexures (formed by transverse folds)
  
  • superior
  • middle (intermediate)
  • inferior

Question 11

What are the three internal transverse folds of the rectum?

They create what lateral flexures?

What structure exists right above the pelvic floor?

Answer 11

• Folds
  
  • Semi-circular
  • Permanent
  • Form sharp lateral flexures
• Lateral flexures
  
  • upper lateral curvature
  • middle lateral curvature
  • lower lateral curvature
• Above pelvic floor
  
  • rectal ampulla (enlargement of the rectum)
  • continuous with anal canal

Question 12

What visceral structures are in direct contact with the rectum in female & male bodies?

Answer 12

• Female
  
  • vagina
• Male
  
  • Urinary bladder
    
    • terminal ureters
    • ductus deferens
    • seminal glands
    • prostate

Question 13

Identify the indicated features of the provided image

Describe the importance of each feature

Answer 13

• Anorectal line
  
  • where anal canal begins (in line with puborectalis)
• Pectinate line
  
  • divides anal canal in half
  • each half supplied by different neurovascular structures
• anal columns
  
  • separated by anal sinus
  • pectinate runs along the bottom of this
• White line of Hilton (intersphincteric groove)
  
  • where internal & external anal sphincters meet up
  • anal verge = junction of mucosa & pure anal skin

Question 14

Identify the indicated features of the provided image

Answer 14

Question 15

What are the muscle layers of the rectum?

Answer 15

• Outer longitudinal layer
  
  • taenia coli of the sigmoid colon as they spread out at the rectosigmoid junction
• Inner circular layer

Question 16

How are the structures of internal and external anal sphincer different?

Answer 16

• Internal Anal Sphincter (IAS)
  
  • thickening of inner circular muscle layer
  • upper 2/3 of anal canal
  • smooth muscle, involuntary
    
    • maintains normal resting tone & will relax under parasympathetic influence when there is solid stool w/in the rectum
• External Ana Sphincter (EAS)
  
  • entire length of anal canal
  • skeletal muscle, voluntary
    
    • keeps anal canal closed & relaxes during defacation
    • innervated by branches from pudendal nerve

Question 17

Identify the indicated features of the provided image

Answer 17

Question 18

What arteries supply the rectum & anal canal?

Answer 18

• Superior rectal artery (from IMA)
  
  • main supply to rectum
• Middle rectal arteries (R/L) (from Internal Iliac)
  
  • supply muscle layers
• Inferior rectal arteries (R/L) (from Internal Pudendal, form Internal Iliac)
  
  • supply anal canal
• All of these branches form an anastamoses along the rectum, making incidence of rectal ischemia relatively low

Question 19

What veins drain the rectum & anal canal?

What is a unique features of these veins?

Answer 19

• Veins accompany arterial supply
  
  • superior rectal
    
    • drain into inferior mesenteric – to portal system
  • middle rectal
    
    • drain into internal iliac – to caval system
  • inferior rectal
    
    • drain internal pudendal – to caval system
• Since veins draining the rectum & anal canal are entering two differen system, Portal and Caval, this creates a site of portosystemic anatomosis
  
  • ​portal hypertension can result in dilation of these vessels

Question 20

Where does lymph from the differnt segments of the rectum & anal canal drain?

Answer 20

• Superior rectum drains into inferior mesenteric lymph node
• Anal canal above pectinate line & inferior rectum drain to internal iliac lymph node
• Anal canal below pectinate line, will drain into superficial inguinal lymph node

Question 21

What is the innervation of the anal canal above & below the pectinate line?

Answer 21

• Above pectinate line
  
  • autonomic innervation from inferior hypogastric plexus
    
    • sensitive to stretching, but not to pain
• Below pectinate line
  
  • somatic innervation from pudendal nerve (inferior rectal nerve)
    
    • sensitive to pain, temp, touch

Question 22

What are the two diferent types of hemorrhoids & how are the different?

Answer 22

• Internal hemorrhoids
  
  • above pectinate line (prolapse rectal mucosa)
  • superior rectal veins
  • visceral innervation: not painful
• External hemorrhoids
  
  • below pectinate line
  • inferior rectal veis
  • somatic innervation: painful

Question 23

Describe the descent of the ureters & where stones are most likely to get stuck

Answer 23

• descend through abdomen
• cross the common iliac artery
• continue down the lateral walls of the pelvis
• turn anteromedially & enter the base of the bladder
  
  • Females: crossed by uterine artery
  • Males: crossed by ductus deferens
• Places stones are likely to get stuck:
  
  • crossing into the pelvis over common iliac
  • coming into bladder wallD

Question 24

Arterial supply of ureters?

Venous drainage of ureters?

Answer 24

• Arterial supply (variable)
  
  • distally from interal iliac artery
    
    • anastamose along the course of the ureter
  • more proximally from abdominal aorta & renal arteries
• Venous drainage
  
  • parallels arteries

Question 25

Where in the pelvis is the bladder located when it is empty vs. full?

Answer 25

* Empty * lesser pelvis * just behind/level with pubic symphysis * Full * enters grater pelvis (can rise all up to level of umbillicus) * peritoneum is pulled away fromt eh anterior abdominal wall as the bladder expands * helpful when placing a catheter & understanding how to access the bladder without perforating the peritoneum

Question 26

Identify the external features of the bladder

Answer 26

* superior surface * 2 inferolateral surfaces * Base (fundus)

Question 27

Where and how do the ureters pierce the bladder? In males, what feature is continuous with the prostate?

Answer 27

ureters pierce the posterolateral aspect inan oblique manner In males, the neck is continuous with the prostate

Question 28

What are the defining landmarks of the Trigone?

Answer 28

Internal featues of the bladder * openings of ureters * interureteric ridge * internal orifice of the urethra

Question 29

What is the main function of the detrusor? It is innervated by what nerve?

Answer 29

* Muscular wall of the bladder -- multidirectional fibers * Function: * contract during urination, which pushed urine out of the bladder into the urethra * Innervation: * Pelvic splanchnic nerves (parasympathetic) * Inferiorly, detrusor muscles form the internal sphincter of urethra (involuntary)

Question 30

An obstruction to urination can have impact to the detrusor muscle?

Answer 30

can cause hypertrophy

Question 31

What is the major arterial supply to the blader? How does arterial supply vary by sex? What about venous drainage?

Answer 31

* Arterial Supply * Both sexes: * superior vesical arteries from umbilical artery * Females: inferior vesical arteries from internal iliac artery * Males: unnamed branches from vaginal artery * Venous drainage * Both sexes * vesical venous plexus to the internal iliac veins * Females: communicates with vaginal/uterine venous plexus * Males: communicates with prostatic venous plexus

Question 32

What lymphatic nodes drain the bladder?

Answer 32

* _Superior surface_ of bladder is drained by **external iliac nodes** * _Base of the bladder_ is drained by **internal iliac nodes**

Question 33

The female urethra is fused to what structure? Where does originate & terminate? Why are UTIs more common in females?

Answer 33

* Originates at internal urethral orifice & terminates at external urethral orifice * Passes in atero/infero direction fused to anterior wall of vagina * UTIs are more common in females because * urethra opens into the vestibule of the vagina - direct exposure to pathogens * the urethra is not very long, so the pathogens do not have to travel very far to get to the bladder

Question 34

Whta muscles control the female urethra?

Answer 34

* both sphincters compress the urethra * urinary incontenence is oftern associated with dysfunction of these sphincters * Internal sphincter * involuntary * prevents urine from leaving the bladder & entering the urethra * External urethral sphincter - fused to vagina * voluntary * helps stop urine from escaping the urethra * innervated by pudendal nerve

Question 35

Autonomic innervation of the bladder?

Answer 35

* Parasympathetic * S2-S4 * Pelvic Splanchnic * Sympathetic * lower thoracic/upper lumbar spinal nerves in the hypogastric plexus

Question 36

Identify the indicated features of this sagital MRI

Answer 36