Pelvic Anatomy and Muscles Quiz

Pelvic Diaphragm

• The pelvic diaphragm is made of muscle
• It stabilizes the anal canal and rectum
• The pelvic diaphragm is made up of the coccygeus and levator ani muscles
• The levator ani muscle is more medial and the coccygeus muscle is more lateral
• The levator ani muscle is responsible for holding the pelvic viscera in the pelvic canal

Ischiorectal Fossa

• The ischiorectal fossa is a space between the anus and the ischiatic tuberosity
• It is excluded from the pelvic cavity by the pelvic diaphragm
• The ischiorectal fossa is made up of fat
• It is located between the anus and the ischiatic tuberosity
• Contains the internal pudendal vessels and pudendal nerve

Muscles of the Rectum and Anal Canal

• The internal anal sphincter is made of smooth muscle and is located deep to the anal sacs
• The internal anal sphincter is innervated by the autonomic nervous system and is responsible for maintaining tone in the anal canal
• The external anal sphincter is made of striated muscle and is located superficial to the anal sacs
• The external anal sphincter is innervated by the somatic nervous system and is responsible for voluntary control of the anal canal

Female Urethra

• The female urethra opens ventrally at the junction of the vestibule and the vagina
• The female urethra is surrounded by the urethralis/urethral muscle, which is the external urethral sphincter
• The external urethral sphincter is innervated by the pudendal nerve
• The suburethral diverticulum is a blind pouch ventral to the urethral opening in cows and sows

Male Urethra

• Two parts: pelvic urethra and penile urethra
• The colliculus seminalis is an elevated region on the urethral crest
• The colliculus seminalis contains the opening of the deferent ducts and many prostatic openings
• The pelvic urethra is surrounded by the urethralis/urethral muscle, which is the voluntary sphincter
• The urethralis/urethral muscle is innervated by the pudendal nerve

Pelvic Viscera Blood Supply

• The aorta sends branches to the pelvic viscera
• The external iliac artery is bilateral and supplies the pelvic limb
• The internal iliac artery is bilateral and supplies the pelvic viscera
• The median sacral artery is unpaired and supplies the sacrum and continues as the median caudal artery which supplies the caudal vertebrae (coccygeal)
• The umbilical artery carries blood to the placenta in the fetus and becomes the round ligament of the bladder in the adult

Terminal Branches of the Internal Iliac Artery

• The internal pudendal artery supplies the vagina/prostate, uterus/ductus deferens, caudal vesical artery, middle rectal artery, and the ventral perineal artery
• The ventral perineal artery supplies the caudal rectal artery
• The cranial gluteal artery supplies the middle and deep gluteal muscles

Pelvic Viscera Innervation

• The pelvic plexus supplies both the sympathetic and parasympathetic nervous systems to the pelvic viscera
• The hypogastric nerve supplies the SNS to the pelvic viscera
• The pelvic nerve supplies the PSNS to the pelvic viscera
• The genitofemoral nerve supplies somatic innervation to the cremaster muscle and sensory innervation to the proximal medial aspect of the thigh, and the inguinal region
• The pudendal nerve supplies somatic motor innervation to the muscles of the pelvic viscera (external urethral sphincter, external anal sphincter), the perineum (muscles of the penis and clitoris, scrotum) and sensory innervation to the pelvic viscera, rectum, anus, scrotum/vulva, penis, clitoris, perineum, and internal and external reproductive organs

Pelvic Viscera Lymphatics

• The medial iliac lymph nodes are located between the deep circumflex iliac artery and the external iliac artery
• The medial iliac lymph nodes drain the dorsal aspect of the abdomen, the pelvis, pelvic limb, genital tract, and caudal aspect of the urinary and digestive systems
• The internal iliac lymph nodes are located between the internal iliac artery and the median sacral artery
• The internal iliac lymph nodes drain the musculature in the area, pelvis, lumbar, sacral, and caudal vertebrae, genital system, caudal digestive and urinary systems
• The sacral lymph nodes are not always present. They drain similar structures as the hypogastric lymph nodes.