Pelvic Canal Anatomy

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Questions and Answers

What forms the dorsal boundary of the pelvic inlet?

Promontory of the sacrum (correct)

Pecten of the pubis

Arcuate line of the ilium

First caudal vertebra

Which muscle is located more medially within the pelvic diaphragm?

Superficial gluteal

Levator ani (correct)

Coccygeus

Rectococcygeus

What occupies the ischiorectal fossa normally?

Adipose tissue (correct)

Muscle tissue

Bone

Connective tissue

Which boundary of the pelvic outlet is absent in cats?

Sacrotuberous ligament Signup and view all the answers

What characterizes the internal anal sphincter?

Under autonomic nervous system control Signup and view all the answers

Which of the following muscles retains the pelvic viscera in the pelvic canal?

Levator ani Signup and view all the answers

What is the primary function of the external anal sphincter?

Controls the discharge of feces Signup and view all the answers

What forms the lateral boundary of the pelvic outlet?

Sacrotuberous ligament and pelvic diaphragm mm. Signup and view all the answers

What is the main blood supply to the middle and deep gluteal muscles?

Cranial gluteal a. Signup and view all the answers

Which nerve provides somatic innervation to the muscles of the pelvic viscera?

Pudendal nerve Signup and view all the answers

What type of innervation does the pelvic nerve provide?

Parasympathetic to the pelvic viscera Signup and view all the answers

Which lymph nodes drain the genital system and caudal digestive system?

Internal iliac lymph nodes Signup and view all the answers

Which nerve does NOT innervate the external urethral sphincter?

Genitofemoral nerve Signup and view all the answers

Where does the female urethra open?

Junction of the vestibule and vagina Signup and view all the answers

Which structure surrounds the pelvic urethra in males?

Urethralis muscle Signup and view all the answers

What is the function of the pudendal nerve concerning the urethra?

Innervates the external urethral sphincter Signup and view all the answers

Which artery gives off the cranial vesical artery in the fetus?

Internal iliac artery Signup and view all the answers

What is the colliculus seminalis?

An elevated region on the urethral crest Signup and view all the answers

What is a characteristic of the internal iliac artery?

It gives off the umbilical artery, which carries blood to the placenta in fetuses. Signup and view all the answers

Which of the following is NOT a branch of the internal iliac artery?

Femoral artery Signup and view all the answers

What does the median sacral artery supply?

The sacrum and becomes the median caudal artery Signup and view all the answers

What structure stabilizes the anal canal and rectum?

Pelvic diaphragm Signup and view all the answers

Which of the following is a clinical application related to failure of the pelvic diaphragm?

Perineal hernia Signup and view all the answers

The rectum is a continuation of which structure?

Colon Signup and view all the answers

Where are the paranal sinuses located?

Between the internal and external anal sphincters Signup and view all the answers

What can occur in the perineal body during parturition?

Tearing Signup and view all the answers

What does the median ligament of the bladder contain in the fetus?

Umbilical arteries and urachus Signup and view all the answers

Which layer is located lateral to the mesorectum?

Pararectal fossa Signup and view all the answers

What is the characteristic of the urinary bladder when it is full?

It remains fixed in the pelvic cavity Signup and view all the answers

Which portion of the urinary bladder does NOT typically contain any fetal structures in adults?

Median ligament Signup and view all the answers

What does the cutaneous zone of the anal canal contain?

Fine hairs and openings of paranal sinus Signup and view all the answers

Which structure is NOT supplied by the prostatic artery in male dogs?

Vagina Signup and view all the answers

What is the primary function of the artery of the clitoris/penis?

Providing blood to the clitoris/penis Signup and view all the answers

Which artery supplies the uterus in female dogs?

Vaginal artery Signup and view all the answers

What is the largest terminal branch of the internal iliac artery?

Caudal gluteal artery Signup and view all the answers

Which of the following structures is supplied by the vaginal artery?

Urethra Signup and view all the answers

Which muscle is NOT primarily supplied by the caudal gluteal artery?

Iliopsoas Signup and view all the answers

What role does the iliolumbar artery play in the vascular system?

Arises near the caudal gluteal artery Signup and view all the answers

Which of the following structures is NOT listed as being supplied by the prostatic artery?

Uterus Signup and view all the answers

Study Notes

Pelvic Canal

Pelvic inlet, outlet, and diaphragm play key roles in supporting pelvic viscera.

Pelvic Inlet

Dorsal Boundary: Promontory of the sacrum
Lateral Boundary: Arcuate line of the ilium
Ventral Boundary: Pecten of the pubis

Pelvic Outlet

Dorsal Boundary: First caudal vertebra
Lateral Boundary: Sacrotuberous ligament (absent in cats), pelvic diaphragm muscles (coccygeus, levator ani)
Ventral Boundary: Ischiatic arch

Pelvic Diaphragm

Comprised primarily of the coccygeus and levator ani muscles.
Coccygeus Muscle: More lateral, short, thick.
Levator Ani Muscle: More medial, thinner, extensive, partially covered by coccygeus muscle.
Muscle Tone: Essential for retaining pelvic viscera within the pelvic canal.

Ischiorectal Fossa

Space located between the anus and ischiatic tuberosity, filled with fat.
Lateral Wall: Ischial tuber, sacrotuberous/sacrosciatic ligament.
Medial Wall: Pelvic diaphragm.
Contains important vessels and nerves:
- Internal pudendal vessels
- Pudendal nerve

Muscles of Rectum & Anal Canal

Internal Anal Sphincter: Deep to anal sacs, smooth muscle, ANS innervation.
External Anal Sphincter: Superficial to anal sacs, striated muscle, voluntary control, somatic innervation.
Rectococcygeus Muscle: Stabilizes anal canal & rectum, smooth muscle, on ventral surface of tail.

Perineal Hernia

Occurs due to pelvic diaphragm failure.
Pelvic or abdominal viscera protrude through weakened or ruptured diaphragm.
Can be unilateral or bilateral.
Straining can exacerbate the condition.
Most commonly occur between the levator ani, external anal sphincter, and internal obturator muscles.

Rectum

Continuation of the colon.
Begins at the pelvic inlet.

Anal Canal

Continuation of the rectum to the anus.
Divided into three zones:
- Columnar: Longitudinal folds
- Intermediate: Between columnar and cutaneous zones
- Cutaneous: Fine hairs, paranal sinus openings

Anus

External opening of the anal canal.

Paranal Sinuses (Anal Sacs)

Paired structures with ducts inside the anus.
Located between the internal and external anal sphincters.
Contain anal glands.

Perineum

Perineum Wall: Surrounds anus and vulva/scrotum, covers pelvic outlet.
Perineal Region: Between tail and scrotum/udder.
Perineal Body: Between anus and dorsal commissure of vulva, can tear during parturition.

Peritoneal Reflections

Pararectal Fossa: Lateral to the mesorectum.
Rectogenital Pouch: Between rectum and genital fold/cranial vagina.
Vesicogenital Pouch: Between urinary bladder and cranial vagina/prostate and genital fold.
Pubovesical Pouch: Between urinary bladder and pubis.

Lateral Ligaments of the Bladder: Contain the caudal portion of the ureter and a portion of the umbilical artery in the fetus. In adults, contain the caudal portion of the ureter and the round ligament of the bladder (remnant of the umbilical artery).
Median Ligament of the Bladder: Contains portions of the umbilical arteries and urachus in the fetus. In adults, usually does not contain any structures.

Urinary Bladder

Distensible storage organ confined within the pelvic cavity when contracted.
The neck remains fixed within the pelvic cavity when distended.
3 portions: Apex, Body, Neck.

Female Urethra

Located on the pelvic floor.
Opens ventrally at the junction of the vestibule and vagina.
Suburethral Diverticulum: Blind pouch ventral to urethral opening in cows and sows.
Urethralis/Urethral Muscle: Surrounds urethra, external urethral sphincter, innervated by the pudendal nerve.

Male Urethra

Two parts: Pelvic urethra and penile urethra.
Colliculus Seminalis: Elevated region on the urethral crest, opening of deferent ducts and prostatic openings.
Urethralis/Urethral Muscle: Surrounds the pelvic urethra, voluntary sphincter, innervated by the pudendal nerve.

Blood Supply

Aorta: Gives rise to the external iliac artery (bilateral), internal iliac artery (bilateral), and median sacral artery.
- Median Sacral Artery: Unpaired, continuation of aorta, supplies sacrum and becomes the median caudal artery (supplies coccygeal vertebrae).
Internal Iliac Artery: Gives off the cranial vesical artery.
- Umbilical Artery: Carries blood to the placenta in the fetus. Remnant in adults is the round ligament of the urinary bladder.
- Terminal Branches:
  - Internal Pudendal Artery: Supplies vaginal/prostatic artery, caudal vesical artery, middle rectal artery, and terminates into three branches (ventral perineal artery, urethral artery, artery of the clitoris/penis).
  - Caudal Gluteal Artery: Larger than the internal pudendal artery, accompanies the sciatic nerve.
  - Iliolumbar Artery: Arises close to the caudal gluteal artery or directly from the internal iliac artery.
  - Cranial Gluteal Artery: Main blood supply to the middle and deep gluteal muscles.

Innervation

Pelvic Plexus: Comprised of the hypogastric nerve and pelvic nerve.
- Hypogastric Nerve: Supplies SNS to the pelvic viscera.
- Pelvic Nerve: Supplies PSNS to the pelvic viscera.
Genitofemoral Nerve: Somatic innervation to the cremaster muscle, sensory to skin of the proximal medial thigh and inguinal region.
Pudendal Nerve: Gives rise to caudal rectal nerve, perineal nerve, and dorsal nerve of the penis/clitoris. Somatic motor innervation to pelvic viscera muscles (external urethral sphincter, external anal sphincter), perineum, and internal and external reproductive organs. Sensory to pelvic viscera, rectum, anus, scrotum/vulva, penis, clitoris, perineum, and internal and external reproductive organs.

Lymphatics

Medial Iliac Lymph Node: Between the deep circumflex iliac artery and external iliac artery. Drains the dorsal abdomen, pelvis, pelvic limb, genital tract, and caudal urinary and digestive systems.
Internal Iliac Lymph Node: Between the internal iliac artery and median sacral artery. Drains the pelvic musculature, lumbar, sacral and caudal vertebrae, genital system, caudal digestive and urinary systems.
Sacral Lymph Node: Not always present, lies ventral to the sacrum. Drains similar structures to the hypogastric lymph node when present.

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Description

Test your knowledge of the pelvic canal anatomy, including the pelvic inlet, outlet, and diaphragm. This quiz covers the boundaries and muscles involved in supporting the pelvic viscera, as well as key structures like the ischiorectal fossa.