Pelvic Planes: Inlet, Midcavity, Outlet

Pelvic Planes

• Pelvic planes allow for understanding of spatial relationships within the pelvis

Plane of Pelvic Inlet

• Bounded by the terminal line
• Terminal line is marked by the pubic crest, pectineal line of the pubic bone, arcuate line promontory, and pubic symphysis

Plane of Mid Cavity

• Also known as the plane of greatest pelvic dimensions or plane of amplitude
• Passes between the middle of the posterior surface of the pubic symphysis, the junction between the 2nd and 3rd sacral vertebrae, the center of the acetabulum, and the upper part of the greater sciatic notch

Plane of Obstetric Outlet

• Also known as the plane of least pelvic dimensions or plane of angustia
• Passes from the lower border of the pubic symphysis anteriorly, to the ischial spines laterally, and to the tip of the sacrum posteriorly

Plane of Anatomical Outlet

• Consists of 2 triangular planes with one base, which is the bituberous diameter
• Anterior sagittal plane apex is located at the lower border of the symphysis pubis
• Posterior sagittal plane apex is located at the tip of the coccyx

Internal Pelvic Dimensions

• Used for assessing the size and shape of the pelvic cavity
• Crucial in obstetrics for determining the feasibility of vaginal delivery

Anatomical Conjugate

• Measured from the superior border of the pubic symphysis to the promontory
• 11 cm in length

Obstetrical Conjugate

• Distance from the pubic symphysis 1 cm below the superior border to the promontory

Transverse Diameter (Inlet)

• Measured from the inferior border of the pubic symphysis to the promontory
• 13 cm in length

Sagittal Diameter of the Amplitudine Plane

• Measured between the middle part of the pubic symphysis and the junction of the 2nd and 3rd sacral vertebra
• Ranges from 12.0 to 12.5 cm

Sagittal Diameter of the Angustia Plane

• Measured between the inferior border of the pubic symphysis and the apex of the sacral bone
• 11 cm in length

Sagittal Diameter of the Exit Pelvic Plane

• Measured between the inferior border of the pubic symphysis and the apex of the coccyx

Pelvis Axis

• Imaginary line joining the center points of the planes of the inlet, cavity, and outlet
• Represents the path the fetus takes during birth

Transverse Diameter of the Amplitudine Plane

• Also known as the interacetabular diameter
• Represents the distance measured between the centers of both coxal joints acetabula
• 12 cm in length

Transverse Diameter of the Angustia Plane

• Also known as the ischial interspinous diameter
• Represents the distance measured between ischial spines of both ischial bones
• 10.5 cm in length

Transverse Diameter of the Pelvic Outlet Plane

• Also known as the ischial inter tuberous dimension
• The dimension is measured between both ischial tuberosities
• Ranges from 11 to 12 cm

Transverse Diameter of the Pelvic Inlet Plane

• Dimension measured between both terminal lines
• 13 cm in length

Oblique Diameter of the Inlet Plane

• The dimension is measured between the sacroiliac joint on one side and the iliopubic eminence on the other side
• 12 cm in length

External Pelvic Dimensions

• Measured externally to assess overall pelvic size and shape

Intercristal Distance

• Extends between the furthest lateral points of the iliac crests
• Ranges from 28 to 29 cm

Interspinal Distance

• Extends between the right and left anterior superior iliac spines
• Ranges from 25 to 26 cm

Intertrochanteric Distance

• Extends between the right and left greater trochanter of femur
• Ranges from 31 to 32 cm

External Conjugate

• Distance measured between the superior border of the pubic symphysis and the spinous process of the L5 vertebra
• Normal is ≥ 20 cm

Interpretation of External Conjugate

• Slightly shortened: 19 cm
• Shortened: < 19 cm

External Oblique Diameter (Right)

• Measured between the right posterior superior iliac spine and the left anterior superior iliac spine
• Normal: 22 cm

External Oblique Diameter (Left)

• Measured between the left posterior superior iliac spine and the right anterior superior iliac
• Normal: 21.5 cm

Pelvic Topography in Females

• Vagina penetrates the pelvic floor and connects with the uterus in the pelvic cavity
• Uterus is positioned between the rectum and the bladder
• A uterine fallopian tube extends laterally on each side toward the pelvic wall to open near the ovary

Pelvic Topography in Males

• The pelvic cavity contains the connection between the urinary and reproductive tracts
• Major glands associated with the reproductive system include the prostate and two seminal vesicles

Topography of Genital Organs in Both Genders

• The roots of the external genitalia, the clitoris, and the penis are firmly anchored to the bony margin of the anterior half of the pelvic outlet
• Also anchored to a thick, fibrous, perineal membrane, which fills the area
• Roots consist of erectile (vascular) tissues and associated skeletal muscles

Pelvic Floor

• Composed of muscles and connective tissues
• Supports pelvic organs

Levator Ani Muscles

• Attach peripherally to the pelvic walls
• Join each other at the midline by a connective tissue raphe

Pelvic Diaphragm

• Bowl- or funnel-shaped structure
• Formed by the levator ani muscles and completed posteriorly by the coccygeus muscles

Coccygeus Muscles

• Overlie the sacrospinous ligaments
• Pass between the margins of the sacrum and the coccyx and a prominent spine on the pelvic bone, which is the ischial spine

Pelvic Diaphragm Function

• Forms most of the pelvic floor
• Anterior regions contain a U-shaped defect, associated with elements of the urogenital system

Apertures in the Pelvic Wall

• Obturator canal
• Greater sciatic foramen
• Lesser sciatic foramen
• Allow communication with the lower limb

Obturator Canal

• Forms a passageway between the pelvic cavity and the adductor region of the thigh
• Formed in the superior aspect of the obturator foramen, between bone, a connective tissue membrane and muscles that fill the foramen

Lesser Sciatic Foramen

• Lies inferior to the pelvic floor
• Provides communication between the gluteal region and the perineum

Communication Between Pelvic Cavity and Perineum

• Occurs through a small gap between the pubic symphysis and the perineal membrane

Structures Intersecting at the Perineal Body

• Structures of the pelvic floor intersect with structures in the perineum at the perineal body
• Fibromuscular node lies at the center of the perineum, approximately midway between the two ischial tuberosities
• Converging at the perineal body are: the levator ani muscles of the pelvic diaphragm; and muscles in the urogenital and anal triangles of the perineum, including the skeletal muscle sphincters associated with the urethra, vagina, and anus

Perineum

• The perineum is a diamond-shaped outlet
• Divided into anal and urogenital triangles
• Sensory and motor innervation is provided by the pudendal nerve
• Blood supply is provided by the internal pudendal artery and internal pudendal vein

Anal Triangle

• Contains the anal canal
• Surrounded by the ischioanal fossa

Urogenital Triangle

• Forms the anterior aspect of the perineum
• Contains the superficial root structures of the external genitalia
• Subdivided into superficial and deep perineal pouches

Muscles of Pelvic Walls

• Obturator internus
• Piriformis
• Help with hip rotation and stabilization

Obturator Internus - Origin

• Anterolateral wall of true pelvis
• Deep surface of obturator membrane and surrounding bone

Obturator Internus - Insertion

• Medial surface of greater trochanter of femur

Obturator Internus - Innervation

• Nerve to obturator internus L5, S1

Obturator Internus - Function

• Lateral rotation of the extended hip joint
• Abduction of flexed hip

Piriformis - Origin

• Anterior surface of sacrum between anterior sacral foramina

Piriformis - Insertion

• Medial side of the superior border of the greater trochanter of the femur

Piriformis - Innervation

• Branches from L5, S1, and S2

Piriformis - Function

• Lateral rotation of the extended hip joint
• Abduction of flexed hip

Fasciae of Pelvic Floor

• Visceral pelvic fascia
• Parietal pelvic fascia
• Obturator fascia

Visceral Pelvic Fascia

• Begins with the tendonous arch of the pelvic fascia
• Covers the internal organs of the pelvis
• Helps to fix the organs

Parietal Pelvic Fascia

• Covers the pelvic walls and the pelvic wall muscles

Obturator Fascia

• Covers the obturator internus muscle
• Serves as an attachment to the levator ani muscle

Muscles of the Pelvic Diaphragm

• Levator ani
• Coccygeus
• Contribute to the pelvic floor and support pelvic viscera

Levator Ani

• Contributes to the formation of the pelvic floor, which supports the pelvic viscera
• Maintains an angle between the rectum and anal canal
• Reinforces the external anal sphincter
• Functions as a vaginal sphincter in women

Levator Ani - Origin

• A line around the pelvic wall beginning on the posterior aspect of the pubic bone
• Extends across the obturator internus muscle as a tendinous arch to the ischial spine

Levator Ani - Insertion

• Anterior part is attached to the superior surface of the perineal membrane
• Posterior part meets its partner on the other side at the perineal body, around the anal canal, and along the anococcygeal ligament

Levator Ani - Innervation

• Branches direct from the ventral ramus of S4
• Inferior rectal branch of the pudendal nerve (S2 to S4)

Coccygeus

• Contributes to the formation of the pelvic floor, which supports the pelvic viscera
• Pulls coccyx forward after defecation

Coccygeus - Origin

• Ischial spine and pelvic surface of the sacrospinous ligament

Coccygeus - Insertion

• Lateral margin of coccyx and related border of sacrum

Coccygeus - Innervation

• Branches from the anterior rami of S3 and S4

Fasciae of Pelvic Diaphragm

• Superior fascia of the pelvic diaphragm
• Inferior fascia of the pelvic diaphragm

Superior Fascia of the Pelvic Diaphragm

• Departs from the tendon arch of the levator ani muscle
• Covers the upper surface of the levator and coccygeal muscle to the terminal attachment of the diaphragm

Inferior Fascia of the Pelvic Diaphragm

• Covers the lower surface of the levator ani muscle

Urogenital Diaphragm

• Includes muscles that support the urethra
• Accessory muscles in women that support the vagina as well

External Urethral Sphincter - Origin

• Inferior ramus of the pubis on each side and adjacent walls of the deep perineal pouch

External Urethral Sphincter - Insertion

• Surrounds membranous part of the urethra

External Urethral Sphincter - Innervation

• Perineal branches of the pudendal nerve (S2 to S4)

External Urethral Sphincter - Function

• Constricts urethra

Deep Transverse Perineal - Origin

• Medial aspect of ischial ramus

Deep Transverse Perineal - Insertion

• Blends with partner on other side anterior to the urethra

Deep Transverse Perineal - Innervation

• Perineal branches of the pudendal nerve (S2 to S4)

Deep Transverse Perineal - Function

• Stabilizes the position of the perineal body

Compressor Urethrae - Origin

• Ischiopubic rami

Compressor Urethrae - Insertion

• Passes forward lateral to the vagina to blend with partner on other side anterior to the urethra

Compressor Urethrae - Innervation

• Perineal branches of the pudendal nerve (S2 to S4)

Compressor Urethrae - Function

• Accessory sphincter of the urethra
• May facilitate closing the vagina

Sphincter Urethrovaginalis - Origin

• Perineal body

Sphincter Urethrovaginalis - Insertion

• Surrounds urethra and vagina

Sphincter Urethrovaginalis - Innervation

• Perineal branches of the pudendal nerve (S2 to S4)

Sphincter Urethrovaginalis - Function

• Accessory sphincter of the urethra
• May facilitate closing the vagina

Perineal Membrane

• Supports muscles of the perineum and external genitalia

Perineal Muscles

• Muscles in the superficial perineal space
• Include superficial transverse perineal, ischiocavernosus, and bulbospongiosus muscles

Superficial Transverse Perineal Muscle - Origin

• Medial surface of the ischial tuberosity

Superficial Transverse Perineal Muscle - Insertion

• Perineal body

Superficial Transverse Perineal Muscle - Function

• Tightening the center of the perineal body

Superficial Transverse Perineal Muscle - Innervation

• Branch of the pudendal nerve

Ischiocavernosus Muscle - Origin

• Medial surface of the ischial tuberosity

Ischiocavernosus Muscle - Insertion

• Crus of clitoris (penis)

Ischiocavernosus Muscle - Function

• Compression of crus of clitoris (penis) during erection

Bulbospongiosus Muscle - Origin

• Perineal body

Bulbospongiosus Muscle - Insertion

• Cavernous body of clitoris (penis)

Bulbospongiosus Muscle - Function

• Closing the vaginal opening

Fasciae of Urogenital Diaphragm

• Superior fascia of the urogenital diaphragm
• Inferior fascia of the urogenital diaphragm

Urogenital Fasciae - Fusion

• The superior fascia of the urogenital diaphragm and the inferior fascia of the urogenital diaphragm fuse at the anterior and posterior margins
• Begin on the lower branches of the pubic bone

Urogenital Fasciae - Attachments

• The apex of the prostate penetrates the upper fascia
• The penile bulb fuses with the lower surface
• The crus of the penis (or clitoris) adhere laterally

Perineal Pouches

• Superficial perineal pouch
• Deep perineal pouch

Superficial Perineal Pouch - Location

• Between the perineal membrane and superficial perineal fascia

Superficial Perineal Pouch - Contents

• Crura of penis and clitoris
• Bulb of penis
• Bulbs of vestibule
• Ischiocavernosus muscle
• Bulbospongiosus muscle
• Greater vestibular (Bartholin) gland

Deep Perineal Pouch - Location

• Formed by the fasciae and muscles of the urogenital diaphragm

Deep Perineal Pouch - Contents

• External sphincter urethrae muscle
• Deep transverse perineal muscle
• Bulbourethral Cowper gland

Mechanics of Pelvic Floor

• Pelvic floor muscles are the lower closure of the pelvis, on which the viscera rest, exerting pressure
• Sucking action of the lungs and the tension of the abdominal wall relieve the pelvic floor

Division of the Pelvic Canal

• Divided into the supradiaphragmatic and subdiaphragmatic space via both muscle plates

Supradiaphragmatic Space

• Also called the subperitoneal space
• Muscles form the bottom of the supradiaphragmatic space, in which the organs of the pelvis lie

Subdiaphragmatic Part

• Does not contain organs
• Filled with adipose and connective tissue
• Connects with the cutaneous fat lining of the perineum

Deep Perineal Space

• Covered by both fascias of the urogenital diaphragm
• The urethra, and in women also the vagina, pass through the space

Deep Perineal Space - Contents

• Internal pudendal vessels and dorsal nerve of penis or clitoris from the pudendal nerve
• Deep transverse perineal muscle
• External urethral sphincter muscle
• Urethral clamping muscle
• Urethrovaginal sphincter muscle

Deep Perineal Space - Male Specific

• Bulbourethral glands

Deep Perineal Space - Female Specific

• The upper part of the major vestibular glands

Superficial Perineal Space

• The superficial fascia of the perineum limits the space closed posteriorly and laterally, open anteriorly
• Lies bilaterally between the bulb of penis (or bulb of vestibule) and the crus of penis (or clitoris)

Superficial Perineal Space - Boundaries

• Limited from above by the inferior fascia of the urogenital diaphragm
• Limited from below by the superficial fascia of the perineum

Superficial Perineal Space - Contents

• The superficial transverse perineal muscle
• Ischiocavernosus muscle
• Bulbospongiosus muscle
• Connective tissue and adipose tissue
• Branches of the internal pudendal vessels and pudendal nerve

Perineal Body

• Thick fibrous layer of fascia
• Lies in the median plane between the external anal sphincter and the posterior edge of the urogenital diaphragm and the bulb of the vestibule of the vagina or the bulb of the penis
• Connected to the levator ani muscle, the superficial transverse perineal muscle, the deep transverse perineal muscle, the bulbospongiosus muscle, and the external anal sphincter muscle

Ischioanal Fossa

• Lies between the lateral wall of the pelvic cavity (obturator fascia) and the pelvic diaphragm (inferior fascia)

Ischioanal Fossa - Boundaries

• Inferior fascia of the pelvic diaphragm (superiorly)
• Obturator fascia (laterally)
• Sacrococcygeal ligament and gluteus maximus (posteriorly)
• Perineal skin and deep layer of the superficial perineal fascia (inferiorly)

Ischioanal Fossa - Contents

• Ischioanal fat body
• Small vessels to the skin of the perineum and to the external anal sphincter muscle

Pudendal Canal

• Lies in the lateral part of the ischioanal fossa
• Ends under the posterior edge of the urogenital diaphragm

Pudendal Canal - Contents

• Internal pudendal artery and vein
• Pudendal nerve

Pelvic Floor Injury

• The perineum, levator ani, and ligaments of the pelvic fascia may be injured during childbirth
• Can lead to urinary stress incontinence due to weakening of the levator ani and pelvic fascia

Tearing

• The pubococcygeus and puborectalis, the main and most medial parts of the levator ani, are the muscles torn most often

Episiotomy

• Performed to prevent perineal tears
• Structures cut during episiotomy are: vaginal epithelium, superficial transverse perineal muscle, bulbospongiosus muscle, and skin of perineum

Reduced Resistance Points of Pelvis

• Suprapiriform foramen
• Obturator canal

Suprapiriform Foramen

• Sciatic hernias to the subbuttock space

Obturator Canal

• Obturator hernias to the muscle chamber of the medial group of the thigh
• Hernia sac is peritoneum
• Can cause compression of the obturator nerve

Other Areas of Reduced Resistance

• The space between the levator ani muscle and the coccygeal muscle as a pelvic hernia
• Pelvic floor passage sites for organs such as the urethra, rectum, and vagina

Ureters

• Flattened muscular tubes that drain urine from the kidneys to the bladder
• Approximately 30 cm long with a diameter of 4-7 mm

Ureters - Location

• Course retroperitoneally on the medial surface of the psoas major muscle
• Cross the common iliac artery or the external iliac artery at the border of the minor and major pelvis

Ureters - Constrictions

• At the junction of the renal pelvis with the ureter
• At the site of the junction with the common iliac artery
• At the entrance of the ureter to the bladder

Ureters - Course

• Drain the kidneys, course down the posterior abdominal wall, and cross the pelvic inlet to enter the pelvic cavity
• Continue inferiorly along the lateral pelvic wall and ultimately connect with the base of the bladder
• Have an abdominal pelvic part

Structure Crossing the Ureters in Males

• The ductus deferens crosses over the ureter just posterior to the bladder

Structure Crossing the Ureters in Females

• The uterine artery crosses the ureter laterally to the cervix of the uterus

Ureters - Arterial Supply

• Renal arteries supply the upper end
• Abdominal aorta direct branches supply the middle part
• Branches of the internal iliac arteries supply the pelvic part

Ureters - Lymphatic Drainage

• From the upper part to the lumbar nodes
• From the middle part to the lymph nodes associated with the common iliac vessels
• From the inferior part to the lymph nodes associated with the external and internal iliac vessels

Consideration During Surgery

• The ureter courses medial to the suspensory ligament of the ovary and must be protected when ligating the ovarian vessels, and inferior to the uterine artery, 1-2 cm from the cervix

Urinary Bladder

• Stores urine before it is excreted
• Located in the pelvic cavity

Urinary Bladder - Apex

• Directed toward the top of the pubic symphysis
• Connected to the median umbilical ligament (remnant of the urachus)

Urinary Bladder - Base

• Shaped like an inverted triangle and faces posteriorly
• The two ureters enter the bladder at each of the upper corners of the base
• The urethra drains inferiorly from the lower corner of the base

Urinary Bladder - Trigone

• The smooth triangular area between the openings of the ureters and urethra on the inside of the bladder
• Inferolateral surfaces are cradled between the levator ani muscles of the pelvic diaphragm and the adjacent obturator internus muscles above the attachment of the pelvic diaphragm

Urinary Bladder - Ligamentous Fixation

• Pubovesical(in women)/Puboprostatic (in men) to the pubic symphysis
• Vesicouterine (in women)/Rectovesical (in men) to the uterus/rectum

Key Bladder Muscles

• Detrusor muscle
• Internal urethral sphincter
• Trigone muscle

Detrusor Muscle

• Circular muscle fibers that make up the wall of the bladder

Internal Urethral Sphincter

• Smooth muscle encloses the origin of the urethra
• Innervated by lumbar splanchnics

Trigone Muscle

• Continuous with the internal urethral sphincter

Urinary Bladder - Arterial Supply

• Superior vesical artery from the umbilical artery
• Inferior vesical artery from the internal iliac artery

Urinary Bladder - Venous Drainage

• Vesical plexus to the internal iliac vein

Urinary Bladder - Lymphatics

• To the internal and external iliac lymph nodes, preaortic lymph nodes, and to the thoracic duct

Urinary Bladder - Parasympathetic Innervation

• From sacral segments S2, S3, and S4
• Preganglionic parasympathetic fibers travel in pelvic splanchnic nerves to reach the detrusor muscle
• Facilitates micturition

Urinary Bladder - Sympathetic Innervation

• Through fibers derived from L1 through L2 (lumbar splanchnics)
• Supplies the trigone muscle and urethral sphincter
• Inhibits micturition

Spastic Bladder

• Results from lesions of the spinal cord above the sacral spinal cord levels
• Parasympathetic nerve fibers are not inhibited so detrusor muscle contracts frequently resulting in frequent micturition

Atonic Bladder

• Results from lesions to the sacral spinal cord segments or sacral spinal nerve roots
• There is a loss of contraction of the detrusor muscle resulting in a full bladder with the dribble of urine from the bladder

Bladder Cancer

• Most common tumor of the urinary tract
• Usually a disease of the sixth and seventh decades, although there is an increasing trend for younger patients to develop this disease
• Tumors may spread through the bladder wall and invade local structures, including the rectum, uterus and the lateral walls of the pelvic cavity
• Large bladder tumors may produce complications, including invasion and obstruction of the ureters

Female Urethra

• Short (about 4 cm long)
• Travels a slightly curved course as it passes inferiorly through the pelvic floor into the perineum
• Passes through the deep perineal pouch and perineal membrane
• Opens in the vestibule that lies between the labia minora
• Urethral opening is anterior to the vaginal opening in the vestibule

Male Urethra

• Long (about 15–20 cm)
• Bends twice along its course

Male Urethra - Parts

• Preprostatic part
• Prostatic part
• Membranous part
• Spongy part

Preprostatic Part

• In the wall of the bladder
• Narrowing

Prostatic Part

• In the prostate gland
• Widening, 3-4 cm

Membranous Part

• Within the urogenital diaphragm
• Narrowing

Spongy Part

• In the spongy body of the penis
• Widening in the bulb

Male Urethra - Bends

• Forwards after passing through the urogenital diaphragm
• Backwards when passing through the spongy body of the penis
• Inferiorly, when passing from the root to the body of the penis in a flaccid state

Urethral Catheterization

• Performed to drain urine from a patient's bladder when the patient is unable to micturate

Urethral Wall at Bladder Level

• Made of smooth muscles forming the internal urethral sphincter muscle (smooth muscle; independent of will)

Urethral Wall Originating from Urogenital Diaphragm

• Striated muscle originating from the urogenital diaphragm forms the external urethral sphincter muscle (striated muscle; dependent on will)

Micturition Regulation

• Parasympathetic fibers facilitate micturition
• Sympathetic fibers inhibit micturition

Parasympathetic Fibers in Micturition

• Provoke constriction of the detrusor muscle
• Relaxation of the internal urethral sphincter and trigone muscle

Sympathetic Fibers in Micturition

• Provoke constriction of the internal urethral sphincter and trigone muscle

External Urethral Sphincter in Micturition

• Relaxation and constriction of the external urethral sphincter, which is part of the pelvic diaphragm, are provided by the pudendal nerve (somatic) making these functions voluntary

Male Urethra Structure

• Urethral crest runs on the posterior wall, which is an extension of the urinary bladder uvula (uvula vesicae)
• The crest thickens, forming the seminal colliculus, on which the ejaculatory ducts (ductus. ejaculatorii) open
• Ejaculatory ducts connect the ampulla of vas deferens (ductus deferens) and the excretory ducts coming from the seminal vesicles

Urethral Vascularization

• Branches of the inferior vesical artery
• Vaginal artery
• Internal pudendal arteries

Urethral Venous Drainage

• To the pudendal venous plexus

Urethral Lymphatic Drainage

• Superficial and deep inguinal lymph nodes
• Internal iliac lymph nodes

Urethral - Innervation

• Vesical plexus
• Branches of the pudendal nerve

Rectum - Location and Continuity

• Continuous above with the sigmoid colon at about the level of vertebra S3
• Continuous below with the anal canal as this structure penetrates the pelvic floor and passes through the perineum to end as the anus
• Immediately anterior to, and follows the concave contour of the sacrum

Anorectal Junction

• Pulled forward (perineal flexure) by the puborectalis part of the levator ani muscle
• Anal canal moves in a posterior direction as it passes inferiorly through the pelvic floor

Rectal Ampulla

• Superior, wider part of the rectum

Rectum Structure

• The pelvic part lies anterior to the sacrum and coccyx, is bent backward, and forms a sacral flexion
• The lower anal part lies in the perineal area, bent forward, forming the perineal flexion

Rectum Peritoneal Relation

• Lies extraperitoneally, adjacent to the anterior surface of the sacrum
• Covered with peritoneum from above on the anterior surface and in the lower part laterally

Rectovesical Pouch

• Formed by the peritoneum descending from the rectum in males
• Passes to the posterior surface of the bladder

Rectouterine Pouch

• Formed by the peritoneum descending from the rectum in females
• Passes to the posterior surface of the uterus

Anal Canal - Location

• Begins at the terminal end of the rectal ampulla where it narrows at the pelvic floor

Anal Canal - Sphincters

• Surrounded along its entire length by the internal and external anal sphincters, which normally keep it closed

Anal Canal - Structure

• Upper part is lined by mucosa similar to that lining the rectum
• Distinguished by a number of longitudinal folds known as anal columns, which are united inferiorly by crescentic folds termed anal valves

Anal Sinus

• Depression superior to each anal valve

Pectinate Line

• A circle formed by the anal valves around the anal canal
• Marks the position of the anococcygeal membrane

Anal Pecten

• Transition zone inferior to the pectinate line
• Lined by nonkeratinized stratified squamous epithelium
• The lining of the anal canal becomes true skin inferiorly

Rectum - Muscle Layers

• Outer longitudinal layer
• Inner circular layer
• The circular layer in the anal part forms the internal anal sphincter muscle
• Transversely striated external anal sphincter muscle covers the anal part externally

Transverse Folds of the Rectum

• Located in the mucous membrane lining the rectal bulb
• Two on the left, one on the right
• Located 8–10 cm above the anus

Anal Canal - Arterial Supply

• Superior rectal artery from the inferior mesenteric artery
• Middle rectal artery from the internal iliac artery
• Inferior rectal artery from the internal pudendal artery

Anal Canal - Venous Drainage

• Superior rectal vein to the inferior mesenteric vein
• Middle rectal vein to the internal iliac vein
• Inferior rectal vein to the internal pudendal vein

Anal Canal - Lymphatics

• Drainage mostly to the lymph nodes distributed along the internal iliac and external iliac arteries and along their way to the nodes associated with the aorta
• Lymph is transported to the lumbar trunks, which continue to the origin of the thoracic duct at T12

Digital Rectal Examination

• Affords access to several key structures
• Enables the identification of several disease processes pertaining to the rectum, the anus, the prostate, the seminal vesicles, the bladder, and the perineum

Rectal Plexus

• Inferior part of the rectal plexus around the anal canal has two parts, an internal and an external

Internal Rectal Plexus

• In connective tissue between the internal anal sphincter and the epithelium lining the canal
• Connects superiorly with longitudinally arranged branches of the superior rectal vein that lie one in each anal column
• Enlargement results in internal hemorrhoids, which originate above the pectinate line and are covered by colonic mucosa

External Rectal Plexus

• Circles the external anal sphincter and is subcutaneous
• Enlargement results in external hemorrhoids

Male Reproductive System - Major Components

• Testis
• Epididymis
• Ductus deferens
• Ejaculatory duct on each side
• Urethra and penis in the midline

Male Reproductive System - Accessory Glands

• Single prostate
• Pair of seminal vesicles
• Pair of bulbourethral glands

Testes - Structure

• Covered by tunica albuginea, passing into the testis mediastinum
• Testicular septa protrude from the testis mediastinum
• Septa divide the testicular parenchyma into lobules, of which there are about 200 in each testis

Seminiferous Tubules - Function

• Sperm are produced here

Seminiferous Tubules - Connection

• The convoluted seminiferous tubules are connected by the straight seminiferous tubules to the rete testis
• The rete testis is a network of channels within the testis mediastinum

Efferent Ductules

• Originate in the rete testis
• Pass into the head of the epididymis

Testes - Descent

Originally develop high on the posterior abdominal wall and then descend, normally before birth, through the inguinal canal in the anterior abdominal wall and into the scrotum of the perineum

Testes - Lymphatic Drainage

• Lymph drainage is to the para-aortic lymph nodes in the abdomen, not to the inguinal or pelvic lymph nodes

Testes - Function

• Responsible for sperm production
• Responsible for androgen production

Epididymis - Structure

• A single, long coiled duct that courses along the posterolateral side of the testis
• Efferent ductules form an enlarged coiled mass that sits on the posterior superior pole of the testis and forms the head of the epididymis
• True epididymis is a single, long coiled duct into which the efferent ductules all drain, and which continues inferiorly along the posterolateral margin of the testis as the body of the epididymis and enlarges to form the tail of the epididymis at the inferior pole of the testis

Epididymis - Fixation

• Fixed on the surface of the testis by two ligaments: the superior ligament of the epididymis and the inferior ligament of the epididymis
• Separated from the testis by the sinus of the epididymis

Epididymis - Function

• Spermatozoa acquire the ability to move and fertilize an egg during passage
• Stores spermatozoa until ejaculation
• Continuous with the ductus deferens

Ductus Deferens

• Long muscular duct transports spermatozoa from the tail of the epididymis in the scrotum to the ejaculatory duct in the pelvic cavity
• Ascends in the scrotum as a component of the spermatic cord
• Passes through the inguinal canal in the anterior abdominal wall

Seminal Vesicles

• Accessory gland of the male reproductive system that develops as a blind-ended tubular outgrowth from the ductus deferens
• The tube is coiled with numerous pocket-like outgrowths and is encapsulated by connective tissue to form an elongated structure situated between the bladder and rectum

Prostate Gland

• Unpaired accessory structure of the male reproductive system that surrounds the urethra in the pelvic cavity
• Lies immediately inferior to the bladder, posterior to the pubic symphysis, and anterior to the rectum

Vas Deferens - Structure

• Extension of the ductus of the epididymis
• Carries sperm from the scrotum to the abdominal cavity

Vas Deferens - Parts

• Scrotal part: inside the scrotum
• Funicular part: running in the spermatic cord
• Inguinal part: within the inguinal canal
• Pelvic part: within the pelvis reaching the prostate, widening in the final section in the ampulla of vas deferens

Spermatic Cord

• Testicular artery
• Pampiniform venous plexus
• Vas deferens and its artery
• Cremasteric muscle and its fascia
• Cremasteric artery
• Genital branch of the genitofemoral nerve
• Autonomic nerves
• Lymphatics

Spermatic Cord - Lymphatic Drainage

• Drains into lumbar (aortic) nodes of the lumbar region
• Does not drain to the superficial inguinal nodes which drain the rest of the male perineum

Spermatic Cord - Fascia Layers

• Skin of scrotum
• Tunica dartos
• External spermatic fascia
• Cremasteric muscle and fascia
• Internal spermatic fascia
• Tunica vaginalis testis parietal and visceral layer

Testis - Blood Supply

• Testicular artery
• Testicular vein
• Lymphatics
• Autonomic innervation

Testicular Artery

• Direct branch of the abdominal aorta at the level of L3

Testicular Vein

• Created by fusion of the elements creating the pampiniform plexus
• Drainage on the right side directly to the IVC
• Drainage on the left side to the left renal vein

Cryptorchidism

• Hidden or obscure testis
• Refers to an undescended or maldescended testis
• Untreated cryptorchidism clearly has deleterious effects on the testis over time

Hydrocele

• Painless buildup of watery fluid around one or both testicles that causes the scrotum or groin area to swell
• Common in newborns and can also occur at any age in later life

Varicocele

• Like varicose veins of the small veins (blood vessels) next to one testicle (testis) or both testicles (testes)
• Thought to increase the chance of being infer