Slide Title Slide Number

Posterior Abdominal Wall Slide 2

Kidney Location Slide 3

Review: Lumbar Plexus Slides 4-8

Kidney Location Slide 9

Kidney Trauma & Horseshoe Kidney Slide 10

Review: Hepatorenal recess (Morrison’s Pouch) Slide 11

Introduction: Perinephric and Paranephric Spaces Slide 12

Perinephric (Perirenal) Space and Boundaries Slide 13

Paranephric (Pararenal) Spaces and Boundaries Slide 14

Renal and Suprarenal Arteries Slide 15

Renal and Suprarenal Veins Slide 16

Pathway of Ureter Slide 17

Natural Ureteric Constrictions Slide 18

Renal Calculus and Referred Pain Slide 19

Slide Title Slide Number

Kidney Anatomy Slide 20

Lymphatic Drainage of P Abdominal Wall Slide 21

Bladder Regions Slide 22

Retropubic Space of Retzius Slide 23

Pelvic Peritoneal Spaces Slide 24

Pelvic Peritoneal Fossae Slide 17

Extraperitoneal Spaces Slide 26

Bladder Wall and Bladder Interior Slide 27

Male Urethra Slide 28

Benign Prostatic Hypertrophy Slide 29

Female Urethra Slide 30

Bladder: Motor Innervation Slide 31

Bladder: Sensory Innervation Slide 32

Micturition Slide 33

PowerPoint Handout: Lab 1, Posterior Abdominal Wall & Urinary System Anatomy

Posterior Abdominal Wall

The physical boundary of the posterior abdominal wall is formed by the following osseous and muscular structures.• Osseous structures

• Five lumbar vertebrae and intervening intervertebral discs• Ilia of each coxal bones• Ribs 11 and 12

• Muscular structures• Superiorly: The diaphragm is attached to ribs 11 and 12. In

addition, the medial portion of the diaphragm attaches to the lumbar vertebral bodies via musculotendinous crura.

• The right crura is longer and attaches to the L1-L3 vertebral bodies.

• The left crura is shorter and attaches to the L1-L2 vertebral bodies.

• A midline tendinous connection (median arcuate ligament) courses between the crura to form the aortic hiatus at vertebral level T12, which the aorta passes through to enter the abdominal cavity.

• Medially: Psoas major and minor muscles• Laterally: Quadratus lumborum• Inferiorly: Iliacus

MUSCLE INNERVATION ACTIONPsoas major Anterior rami L1-L3 Flexion of thigh

Quadratus lumborum Anterior rami T12 & L1-L4 Lateral flexion vertebral column & stabilize rib 12 during inspiration

Iliacus Femoral nerve (L2-L4) Flexion of thigh

Four pairs of lumbar arteries typically branch from the aorta.

• The lumbar arteries in the abdominal wall are analogous to the intercostal arteries that course within the thoracic wall. • Path

• They branch from the aorta at the vertebral levels L1-L4 in a posterolateral direction and course along the posterior abdominal wall posterior to the psoas major and quadratus lumborum muscles.

• They pass between the internal oblique and transversus abdominus muscles to course along the anterolateral abdominal wall and terminate near the rectus abdominis muscles.

Lumbar Arteries

Lumbar aa.

Inferior Phrenic a.

Subcostal a.

Median Sacral a.

• Supply• They supply the posterior and anterior abdominal wall.• They directly supply the following muscles: quadratus lumborum, psoas

minor, and psoas major, transversus abdominis, and internal abdominal oblique.

• Dorsal branches of the lumbar arteries supply lumbar vertebrae, spinal cord, and back muscles.

Lumbar a.

Dorsal Branch

Review: Lumbar Plexus

The L1-L3 ventral primary rami and a portion of the L4 ventral primary ramus form the lumbar plexus. Branches of the lumbar plexus include the nerves that innervate structures of the ventrolateral body wall and lower extremity. The nerves of the lumbar plexus are listed below.• Iliohypogastric (L1)• Ilioinguinal (L1)• Genitofemoral (L1-L2)• Lateral femoral cutaneous (L2-L3)• Femoral (L2-L4)• Obturator (L2-L4)• Lumbosacral trunk

• The iliohypogastric (L1) nerve branches from the common trunk it shares with the ilioinguinal nerve at the lateral edge of the psoas major muscle. It then courses along the anterior surface of the quadratus lumborum on its path to pass through the transversus abdominis muscle. The nerve then courses between the transversus abdominis muscle and the internal abdominal oblique muscle where it branches above the iliac crest into the lateral cutaneous branch and the anterior cutaneous branch.

• The lateral cutaneous branch passes through the internal abdominal oblique and external abdominal oblique muscles to enter the skin where it provides sensory innervation to a small area of the gluteal region.

• The anterior branch continues in an anterior direction between the internal abdominal oblique and external abdominal oblique muscles. Ultimately, it passes through the aponeurosis of the external abdominal oblique to enter the skin where it provides sensory innervation to the pubic region.

• The ilioinguinal nerve (L1) nerve branches from the common trunk it shares with the iliohypogastric nerve at the lateral edge of the psoas major muscle. It crosses the iliacus muscle as it courses parallel, but inferior to iliohypogastric nerve. It pierces both the transversus abdominis muscle and the internal abdominal oblique muscle to pass between the internal abdominal oblique and the external abdominal oblique muscles where it enters the inguinal canal from the side (not through the deep ring). It exits the inguinal canal at the superficial ring to enter the skin where it provides innervation to the following areas: upper middle thigh.

• In males, it also supplies the skin over the root of the penis and anterior scrotum. • In females, it supplies the skin over mons pubis and labia majora.

NOTE: For completeness, the path of the ilioinguinal and iliohypogastric nerves is described in detail. Identification of each nerve branching from the lumbar plexus, the nerve root that contributes fibers to each nerve, and each nerve’s sensory distribution is the emphasis.

Lumbar Plexus: Iliohypogastric n. and Ilioinguinal n.

Genitofemoral nerve (L1-2): The genitofemoral nerve courses along the anterior surface of the psoas major muscle.• The femoral branch enters the femoral region by passing posterior to the inguinal ligament. It

is a sensory nerve that supplies the skin in the upper anterior thigh • The genital branch passes through the deep inguinal ring to enter the inguinal canal, and

exits the inguinal canal at the superficial ring. • In men, it innervates the cremaster muscle and terminates in the skin of the upper

anterior scrotum. • In women, it accompanies the round ligament of the uterus and terminates in the skin of

the mons pubis and labia majora.

CLINICAL ANATOMY: Contraction of the cremaster muscle can be elicited via a reflex arc, which is called the cremaster reflex. To elicit this reflex, the examiner strokes the superior and middle aspects of the inner thigh, which results in contraction of the cremaster muscle and an elevation of the testes within the scrotum.• The afferent limb of the reflex is the ilioinguinal nerve

and the femoral branch of the genitofemoral nerve.• The efferent limb is the genital branch of the

genitofemoral nerve, which supplies the cremaster muscle.

Lumbar Plexus: Genitofemoral n.

The lateral femoral cutaneous (L2-3) passes obliquely across the iliacus muscle, in the direction of the anterior superior iliac spine, on its way to the subinguinal space. The nerve enters the lateral thigh by passing posterior to the inguinal ligament and anterior to the sartorius muscle.

CLINICAL ANATOMY: The lateral femoral cutaneous nerve can be compressed where it passes between the inguinal ligament and the sartorius muscle of the anterior thigh. Such compression results in a condition called meralgia paresthetica, which manifests as numbness, tingling, and burning pain along the lateral aspect of the thigh.

Lumbar Plexus: Lateral Femoral Cutaneous n.

• The femoral nerve (L2-4) courses along the anterior surface of the iliacus muscle lateral to the psoas major muscle It passes through the subinguinal space to enter the anterior thigh.

• The obturator nerve (L2-4) is located medial to the psoas major muscle and courses along the lateral wall of the pelvis toward the obturator foramen to enter the medial compartment of the thigh.

• The lumbosacral trunk is a large nerve bundle, formed by a portion of the L4 ventral ramus and all of the L5 ventral ramus, joins the S1 ventral ramus and portions of the S2-3 ventral rami to form the lumbosacral plexus. Branches of the lumbosacral plexus innervate structure/regions of the lower extremity not innervated by branches of the lumbar plexus . This includes structures in the gluteal region, posterior thigh, most of the leg and all of the foot.

Lumbar Plexus: Femora n., Obturator n., and Lumbosacral Trunk

CLINICAL ANATOMY: During childbirth the fetal head may compress the mother’s lumbosacral plexus against the posterior rim of the pelvic bone, especially during forceps delivery. Lumbosacral plexus injuries can affect the quadricep muscles, hip adductors, and ankle dorsiflexors (foot drop). The obturator nerve can be compressed by the fetal head against the lateral pelvic wall resulting in paresthesia in the medial side of the thigh and weak hip adduction. The obturator nerve is also at risk of injury during surgery along the lateral wall of the pelvis, as when removing cancerous lymph nodes along the internal iliac artery.

Kidney Location

The Kidneys (right and left) are bean-shaped organs located within the posterior wall of the abdominal cavity. They are approximately 10 cm in length, 5 cm in width, and 2.5 cm thick. • Both kidneys are posterior to the parietal peritoneum, so their location relative to the

peritoneum is described as retroperitoneal.• They reside on either side of the vertebral column between the vertebral levels T-12

and L-3. However, it is typical for the right kidney to be situated slightly lower than the left kidney because of the right kidney’s anatomical relationship to the liver.

• The transpyloric plane of Addison (L1) bisects the left kidney at approximately the lower margin of its hilum.

• The transpyloric plane of Addison (L1) bisects the right kidney at approximately the upper margin of its hilum.

• From a posterior perspective, the kidneys have anatomical relationships with the ribs and muscles of the posterior abdominal wall

• The superior pole of the right kidney is located deep to the 12th rib and can project into the 11th intercostal space.

• The superior pole of the left kidney is often deep to the 11th rib.• The inferior pole of the right kidney is approximately one finger breadth superior

to the iliac crest.

CLINICAL ANATOMY: Injury to the kidneys can result from blunt trauma or penetrating trauma.

Blunt trauma to the kidneys can result from a variety of causes. The kidneys can be crushed against the ribs or vertebrae (deceleration injury from MVA) because the kidneys are mobile within the renal fascia. In addition, they can be directly injured by fractured ribs or lumbar transverse processes. Devascularization can result when the the kidney’s vasculature is exposed to excessive stretching forces. Right kidney trauma should be suspected with liver trauma, whereas left kidney trauma should be suspected with spleen trauma. Clinical signs include: flank mass, flank tenderness, flank ecchymosis, hypotension, and hematuria.

Kidney trauma should be suspected when penetrating gunshot wounds or knife wounds are located over the lower rib cage.

CLINICAL ANATOMY: Between the sixth and ninth weeks of development, the kidneys ascend to a lumbar site immediately inferior to the suprarenal glands, following a path just on either side of the dorsal aorta. Throughout their ascent the kidneys are progressively revascularized by a series of arterial sprouts from the dorsal aorta. As new, more superiorly located blood vessels are produced, the older vessels located more inferiorly degenerate. Several anomalies can arise during the process of kidney ascent. Occasionally, one or more of the transient inferior renal arteries fail to regress, resulting in the presence of accessory renal arteries. Rarely, a kidney completely fails to ascend, remaining as a pelvic kidney. In addition, the inferior poles of the two kidneys may come into contact and fuse during ascent, forming a U-shaped horseshoe kidney. During ascent, this single kidney becomes caught under the inferior mesenteric artery and therefore never reaches its normal location.

Kidney Trauma & Horseshoe Kidney

• The hepatorenal recess (Morrison’s Pouch) is a potential space located between the visceral surface of the posterior liver and the right kidney. Morrison’s pouch is a common place for excess fluid in the peritoneal cavity to accumulate in a supine patient. Fluid in Morrison’s pouch can be visualized on CT and/or ultrasound.

Review: Hepatorenal Recess (Morrison’s Pouch)Recall that the peritoneal cavity contains many named spaces that are located where the peritoneum reflects upon itself to form mesentery and peritoneal ligaments. These spaces, which are described as recesses, spaces, or gutters, transmit the normal flow of peritoneal fluid throughout the peritoneal cavity. In pathological situations, they can be sites fluid accumulation and function as conduits for the spread of fluid, infection, and neoplasms.

US Morrison’s Pouch

Introduction: Perinephric and Paranephric Spaces

Progressing from anterior to posterior, the posterior abdominal wall consists of the following layers and spaces.1. Parietal peritoneum2. Anterior pararenal space3. Anterior layer of renal fascia4. Perirenal space5. Posterior layer of renal fascia6. Posterior pararenal space7. Transversalis fascia laterally and anterior layer of

quadratus lumborum fascia medially

2. Anterior Para-renal space(containing pancreas, ascending colon, and descending colon)

6. Posterior Para-renal space

7. Transversalis fascia

1. Parietal Peritoneum

4. Peri-renal space

3. Anterior Layer Renal Fascia

5. Posterior Layer Renal Fascia

Pancreas

7. Anterior Layer Quadratus Lumborum Fascia

DescendingColon

• The left and right perirenal spaces extend superiorly to define different regions.

• On the right, the anterior layer of renal fascial fuses with the liver’s coronary ligament and the posterior layer of renal fascia fuses with the diaphragm. This connection to the liver allows for the the right perirenal space to be continuous with the bare area of the liver.

• On the left, the anterior layer and posterior layers of renal fascia both fuse with the diaphragm.

• The Perinephric space is located between the kidney and the surrounding renal fascia. This space is occupied by the following structures.

• Perinephric (perirenal) fat, which is important for keeping the kidney in its proper position. The perineprhic fat passes through the hilum to continue as fat within the renal sinus.

• Kidney• Adrenal gland• Renal vessels, perirenal vessels, and lymphatic vessels

• Surrounding the perinephric space is subserous fascia called renal fascia, which consists of an anterior layer and a posterior layer.

• The anterior layer (lamina) of renal fascia surrounds the perinephric fat on the anterior side of the kidney. Medially, it blends with the adventitia of the renal vessels, aorta, and vena cava. The anterior layer is also called Gerota’s fascia.

• The posterior layer (lamina) of renal fascia surrounds perinephric fat on the posterior and lateral sides of the kidney. The posterior layer is also called Zuckerkandl’s fascia.

• The posterior renal fascia and the anterior renal fascia join laterally to form the lateral conal(lateroconal) ligament, which continues anteriorly to fuse with the parietal peritoneum.

= Anerior Layer Renal Fascia (Gerota’s)

= Posterior Layer Renal Fascia (Zuckerandl’s)

DiaphragmDiaphragm

Bare Area of Liver

Sagittal Section: Right Side Sagittal Section: Left Side

Perinephric (Perirenal) Space and Boundaries

The paranephric space consists of two SEPARATE spaces that are external to the renal fascia. • Anterior paranephric space

• The anterior paranephric space consists of the following boundaries:• Anteriorly: parietal peritoneum • Posteriorly: anterior layer of renal (Gerota) fascia.• Laterally: Lateroconal ligament

• It contains the pancreas, duodenum, the ascending colon, and descending colon and is continuous with the space between the serosal layers of the mesentery.

• Posterior paranephric space • It consists of the following boundaries

• Anteriorly: posterior layer of renal (Zuckerandl) fascia AND lateroconal ligament• Posteriorly: Transversalis fascia

• It doesn’t contain visceral organs but does contain paranephric fat.

Paranephric (Pararenal) Spaces and Boundaries

The renal arteries branch from the aorta at approximately the L1-L2 intervertebral disc level. • The renal arteries typically divide into 5 segmental arteries at, or

prior to, passing through the kidney’s hilum. • Both the right and left renal arteries course to the kidney in a

position posterior to the accompanying renal veins. • The right renal artery is longer than the left and courses posterior

to the inferior vena cava.

The suprarenal glands receive an abundant arterial blood supply via the three vessels listed below. These three vessels branch extensively forming to 50-60 small vessels that penetrate the gland’s capsule. • Superior suprarenal arteries branch from the inferior phrenic

artery (branch of abdominal aorta).• Middle suprarenal arteries branch from the abdominal aorta.• Inferior suprarenal arteries branch from the renal arteries.

CLINICAL ANATOMY: In about 20-25% of people, more than one renal artery supplies the kidney. These "extra" renal arteries are described as accessory renal arteries.

Renal and Suprarenal Arteries

Several renal veins unite to form the right and left renal veins. • The right renal vein is shorter than the left due to the inferior

vena cava being located to the right of the midline. • The left renal vein must cross the midline to drain into the

inferior vena cava. In doing so, it takes a path between the abdominal aorta and the superior mesenteric artery.

• The longer left renal vein receives blood from the following vessels. (On the right, these vessels drain directly into the IVC.)

• Left suprarenal vein• Left gonadal vein (The right gonadal vein drains

directly into the inferior vena cava.)• Both the right and left renal veins are located anterior to the renal

arteries. • Both the right and left renal veins drain into the inferior vena

cava.

CLINICAL ANATOMY: Nutcracker syndrome (NCS) refers to the wide spectrum of clinical presentations caused by compression of the left renal vein between the abdominal aorta and the superior mesenteric artery. The condition can lead to hematuria and left flank pain. Also, because the left gonadal vein drains to the left renal vein, the condition can also result in left testicular pain or left lower quadrant pain in women.

Renal and Suprarenal Veins

The renal pelvis is a funnel-shaped structure that collects urine from the major calyces and drains it to the the ureter .• The distal end of the renal pelvis narrows to become the ureter at the

ureteropelvic junction.• The ureter is retroperitoneal along its path to the bladder. • The ureters cross the following structures as they course inferiorly toward

the pelvis.• Pass anterior to the psoas major muscle• Pass posterior to the gonadal arteries, which are branches from the

aorta.• Pass anterior to the common iliac (or external iliac) arteries and

veins • Pass anterior the pelvic brim to enter the lesser pelvis

• The ureter takes the following pathway through the pelvis on its path to the bladder.

• It courses posteroinferiorly along the lateral wall of the pelvis• Opposite the ischial spine, they curve anteromedially to enter the

urinary bladder.• In males, the ureter passes posterior to the ductus deferens.• In females, the ureter passes posterior to the uterine artery.

CLINICAL ANATOMY: Because of the close proximity of the ureters to the uterine artery, the ureters are in danger of being inadvertently clamped or severed when the uterine artery is tied off during a hysterectomy. A common mnemonic to remember the uterine artery crosses over the ureter is: "water under the bridge."

Female Pelvis Male Pelvis

Pathway of Ureterhttps://3d4medic.al/Ry1jspH1

CLINICAL ANATOMY: Along the length of the ureter, there are three sites of natural lumenal narrowing. These narrowed regions are common sites for renal stones to become lodged, which leads to intense pain. The three places of natural ureteric constrictions are listed below.• Uretopelvic junction• Pelvic brim where the ureter crosses either the common iliac or external

iliac artery• Location where the ureters enter the bladder (ureterovesicular junction)

Natural Ureteric Constrictions

CLINICAL ANATOMY: Pain associated with passage of a renal calculus (“kidney stone”) through the proximal and middle portions of a ureter is transmitted along visceral afferent fibers that follow the sympathetic outflow pathways.• The preganglionic sympathetic neurons in this pathway are located in the T12-L2/L3 spinal cord, with the upper spinal cord segments supplying the more

proximal aspects of the ureters (via lesser and least thoracic splanchnic nerves) and lower cord segments supplying middle portions of the ureters (via lumbar splanchnic nerves).

• Pain from distal portions of the ureter (i.e., inferior to the peritoneum) is transmitted along its parasympathetic outflow tract. Preganglionic parasympathetic neurons in this pathway derive from cells in the S2-S4 spinal cord region.

• As a renal calculus passes through a ureter the referred pain will migrate from the flank, down the abdomen and into the perineum, thigh, and genitalia. This is sometimes called “loin to groin” progression of pain.

Renal Calculus and Referred Pain

• The renal artery is a branch of the aorta and transports oxygenated blood to the kidney.• The renal vein is a tributary of the inferior vena cava and transports deoxygenated blood away from the kidney.• The renal capsule is a fibrous connective tissue capsule that is attached to the surface of the kidney.• The renal cortex is the outer zone of kidney tissue between the capsule and the bases of the medullary pyramids. It composes about ⅓ of the kidney's depth.• The renal medulla is the inner zone of the kidney tissue that that consists of the renal (medullary) pyramids and the renal columns. The renal columns are

extensions of the cortical tissue into the medullary region. The medulla composes about ⅔ of the kidney's depth).• The renal papilla is the apex of the renal pyramid, which projects into a minor calyx.• The renal hilum is a vertical passageway on the medial margin of the kidney through which structures pass to enter the renal sinus.

• Internally, the renal hilum is continuous with the renal sinus, which is the space within the kidney occupied by the renal pelvis, calices, vessels, nerves, and fat.

• The minor calyx is a cup-like hollow structure that receives urine from the renal papilla. It marks the beginning of the extrarenal duct system. Several minor calyces combine to form a major calyx.

• The major calyx is formed by the junction of several minor calyces. Major calyces receive urine from the minor calyces and drain the urine into the renal pelvis.

• The renal pelvis is a funnel-shaped structure that drains urine from the major calyces into the ureter. The portion of the renal pelvis receiving urine from the major calyces is located within the renal sinus. As urine flows distally, the renal pelvis narrows, exits the kidney at the renal hilum, and ultimately becomes the ureter.

• The ureter is a tubular structure with a muscular wall that is a continuation of the renal pelvis. It drains urine from the renal pelvis to the urinary bladder.

Kidney Anatomy

Lymphatic Drainage of Posterior Abdominal Wall

The thoracic duct begins in the abdomen as an extension of the cisterna chyli, which is an elongated lymphatic sac located just inferior to the diaphragm anterior to the L1 and L2 vertebral bodies. The cisterna chyli primarily receives lymph from the following trunks.

• Intestinal trunk: The intestinal lymphatic trunk receives lymph from preaortic lymph nodes. The preaortic nodes which are located near the vessel branches of the aorta that supply of the GI tract, which is how they are named (celiac, superior mesenteric, inferior mesenteric). These nodes receive lymph from the GI tract (lower third of esophagus to proximal ½ anal canal, spleen, pancreas, gallbladder, and liver).

• Right and left lumbar trunks: The lumbar trunks receive lymph from para-aortic (lateral) lymph nodes. The para-aortic nodes are located on the left and right sides of the aorta. They receive lymph from the following areas.

• Common iliac nodes, which receive lymph from the external and internal iliac nodes

• Directly from the following organs• Kidneys, suprarenal glands, deep abdominal wall• Male: testes and epididymis • Female: ovaries, uterine tubes, fundus of uterus

• Note that pre-aortic and para-aortic nodes do communicate with each other and aren’t entirely separate pathways.

P abdominal wall, kidney, suprarenal gland, testis, epididymis, ovary, uterine tube, fundus uterus

The urinary bladder is a hollow, sac-like expandable organ that is a temporary storage site for urine. Urine is drained from the kidney into the bladder by the ureters. The bladder is located within the pelvic cavity when it is empty, but when filled with urine, the superior wall of the bladder can expand into the abdominal cavity. The bladder consists of the following regions.• The apex of the bladder is its anterior end. At the very tip of the apex is the urachus, which is a thick, fibrous cord connecting the bladder to the

umbilicus (median umbilical fold). Initially during fetal development, the bladder lumen is continuous with the allantois, but this connection obliterates forming the urachus.

• The base (fundus) of the bladder is opposite the apex and forms the bladder’s posterior wall. Note: fundus is a term that means “opposite the opening.” For the bladder, the embryological opening is at the apex.

• The body of the bladder is the region between the apex and the base.• The muscular layer of the bladder wall is called the detrusor muscle. It consists of three layers of muscle whose boundaries are indistinguishable

because of the extensive intermingling of muscle fibers between the layers

CLINICAL ANATOMY: Remnants of the allantois occasionally persist in the urachus, forming urachal cysts and urachal sinuses. When the entire lumen of the intraembryonic portion of the allantois persists, a urachal fistula forms which may cause urine to drain from the umbilicus.

Bladder Regions

In men and women, the peritoneum passes from the internal surface of the anterior abdominal wall onto the superior surface of the urinary bladder. The peritoneum does NOT cover the bladder’s anterior surface. The fat-filled space inferior to the peritoneum between the pubic bones/pubic symphysis and the anterior wall of the bladder is the retropubic space (of Retzius). The retropubic space is continuous with the urogenital triangle superior to the perineal membrane (i.e., the deep perineal pouch).

RetropubicSpace

CLINICAL ANATOMY: As the urinary bladder fills, the the anterior wall of the urinary bladder (bare area not covered by peritoneum) is elevated above the level of the pubis. As a result, a full bladder can be punctured or approached surgically at this location without traversing the peritoneum and entering the peritoneal cavity. In these procedures the needle passes through the retropubic space.

Bare Area Superior to Pubis

Retropubic Space of Retzius

RetropubicSpace

The peritoneum continues posteriorly beyond the bladder to cover different structures in men compared to women.• In men, the peritoneum continues posteriorly to cover a small region of the base (fundus). It then continues posteriorly beyond the bladder to cover the

rectum. The space formed this peritoneal reflection is called the rectovesical space/pouch. • In women, the peritoneum continues posteriorly beyond the bladder to cover the uterus. The space formed by this peritoneal reflection is called the

vesicouterine space/pouch. (Note that in women the peritoneum does not cover any portion of the bladder base). After covering the uterus, the peritoneum reflects onto the rectum to form the rectouterine pouch (of Douglas), which is a midline space located between the rectum and the uterus.

CLINICAL ANATOMY: The rectovesical pouch and the recto-uterine pouch are the most inferior aspects of the peritoneal cavities in males and females, respectively. Excess peritoneal fluid will flow to these pouches when in a sitting or standing position. When supine, excess fluid within the peritoneal cavity will flow to the hepatorenal recess, regardless of sex.

Pelvic Peritoneal Spaces

Pelvic Peritoneal FossaeThe paravesical fossa is a gutter-like peritoneal reflection where the peritoneum extends from the lateral side of the bladder to cover the lateral pelvic wall. It varies in depth depending upon the fullness of the bladder.• In men, the lateral margin is the fold of peritoneum covering the ductus deferens• In women, the lateral margin is the broad ligament where it surrounds the round ligament

The pararectal fossa is a peritoneal depression on each lateral side of the rectum formed by peritoneal folds passing from the posterolateral pelvic wall to the centrally located pelvic viscera (bladder in men and uterus in women). These fossae vary in size with distension of the rectum by feces. • Men

• The sacrogenital fold passes from the sacrum to the bladder forming the lateral walls of the pararectal fossa.• The pararectal fossa is a lateral extension of the rectovesical pouch.

• Women• The uterosacral fold passes from the sacrum to the uterus to form the lateral walls of the pararectal fossa.• it is a lateral extension of the rectouterine pouch.

DuctusDeferens

Sacrogenitalfold

Pararectal Fossa

ParavesicalFossa

ParavesicalFossa

Pararectal Fossa

Round LigamentUterosacral

fold

Extraperitoneal Spaces

Previously in this handout, one extraperitoneal space (retropubic space of Retzius) and several intraperitoneal FOSSAE/POUCHES have been described. Surgeons have a particular interest in the extraperitoneal SPACES because they are filled with loose areolar connective tissue, but lack major blood vessels and nerves. This lack of neurovascular structures allows for blunt blunt surgical dissection without disrupting major vessels or nerves. Having an understanding of these spaces is fundamental for most major pelvic surgeries. The extraperitoneal spaces are listed below. • Retropubic• Paravesical• Pararectal• Presacral• Vesicovaginal• Rectovaginal

Note that the pararectal and paravesical SPACES are different from the FOSSAE that have the same name. The spaces are extraperitoneal while the fossa are intraperitoneal. For clarification, the boundaries of the pararectal and paravesicalSPACES are listed below. The purposes of this slide is to prevent confusion when you hear about these spaces on an OB/GYN clerkship. In addition, the structures forming the boundaries listed below will be viewed in Urogenital Lab 2.

Paravesical Space• Anterior: Pubic bone• Posterior: Cardinal ligament• Lateral: Obturator internus• Medial: Superior vesicle artery

Pararectal Space• Anterior: Cardinal ligament• Posterior: Sacrum• Medial: Rectum• Lateral: Internal iliac vessels

= Pararectal Space

= Paravesical Space

• When viewing the interior of the urinary bladder, the following features can be identified.• The openings of the ureters transmit urine from the ureter into the bladder. The

ureter passes through the wall for the urinary bladder at the uretovesicular junction in an oblique orientation. As a result of this oblique orientation, when the bladder is distended, the pressure of the accumulated urine flattens the uretovesicular junction to prevent the reflux of urine into the ureter.

• The internal urethral orifice is the exit pathway for urine to flow into the urethra from the bladder.

• The trigone is a smooth, triangular-shaped region inside the bladder formed by the two ureteric openings and the internal urethral orifice. The muscular region of the bladder wall consists of three smooth muscle layers collectively called the detrusormuscle.

• The neck of the bladder is the region surrounding the origin of the urethra where the inferolateral wall meets the fundus.

• Embedded within the wall of the bladder neck is involuntary smooth muscle. In men, this smooth muscle is organized into a sphincter called the internal urethral sphincter.

Bladder Wall and Bladder Interior

• Urine enters the urethra by passing through the bladder’s internal urethral orifice. The urethra in men consists of 4 named regions and is surrounded by two sphincters.

• The intramural (preprostatic) urethra is the short, proximal portion of the male urethra within the neck of the bladder.

• The preprostatic urethra is surrounded by the internal urethral sphincter, which is innervated by pelvic splanchnic nerves.

• The portion of the urethra within the prostate gland, is called the prostatic urethra. The ejaculatory ducts (right and left) connect to the urethra within the prostate gland.

• The mass of skeletal muscle fibers located immediately inferior to the prostate gland form the external urethral sphincter located within the deep perineal space/pouch (space superior to the perineal membrane in the region formerly known as the urogenital diaphragm ).

• The membranous urethra is the short section of the urethra surrounded by the external urethral sphincter as it courses through the “fibromuscular” region of the deep pouch (former urogenital diaphragm).

• The spongy (penile) urethra is the section of urethra coursing through the penis.

• The external urethral orifice is the opening of the urethra at its termination point.

Male Urethra

CLINICAL ANATOMY: A common condition leading to incontinence in men as they age is benign prostatic hyperplasia (BPH). Prostate gland enlargement can result in compression of the urethra, which increases the resistance to urine outflow from the bladder. In response to this increased resistance, the bladder must exert more pressure to force urine into the urethra. This chronic overexertion causes the muscular walls of the bladder to remodel and become stiffer. A variety of urinary tract symptoms result from the increased resistance and bladder remodeling. More details on BPH will be covered when we study the prostate gland in Lab 2 of the Urogenital System Labs. • Frequent nighttime urination (nocturia).• Urinary hesitancy or difficulty starting urine flow• Slow or intermittent urine flow• Sudden urge to urinate (Urinary urgency)• Leakage or uncontrollable urination• Sensation of incomplete bladder emptying

Benign Prostatic Hypertrophy

• Urine enters the urethra by passing through the bladder’s internal urethral orifice.

• The proximal urethra passes through the neck of the bladder. The smooth muscle within the wall of the bladder neck intermingles with detrusor muscle fibers but lacks a well-defined sphincter arrangement as is present in a man’s bladder neck. Technically speaking, women lack an internal urethral sphincter. However, physiological descriptions of micturition will describe the internal urethral sphincter needing to relax for urination to occur. Details of micturition are on an upcoming slide.

• The urethra courses in an inferior direction along a path that is parallel and anterior to the vagina.

• The external urethral sphincter, consisting of skeletal muscle, surrounds the urethra as it passes through the deep perineal pouch. The external urethral sphincter is innervated by the pudendal nerve (S2-4).

• The urethra opens into the vestibule (space surrounded by labia minora) at the urethra’s external urethral orifice.

• Ducts of the paraurethral (Skene’s) glands are located on either side of the external urethra orifice. These glands are the homologues of the prostate and are thought to secrete fluid to lubricate the urethral opening.

Female Urethra

Innervation of the bladder and urinary sphincters.• Internal urethral sphincter

• Sympathetic innervation • Contraction during filling• T11-L2 spinal cord levels • Hypogastric and vesical plexus

• Parasympathetic innervation • Relaxation during emptying• S2-S4 spinal cord levels• Pelvic splanchnic nerves

• Bladder (Detrusor Muscle)• Sympathetic innervation

• Relaxation during filling• T11-L2 spinal cord levels • Hypogastric and vesical plexus

• Parasympathetic innervation • Contraction during emptying• S2-S4 spinal cord levels• Pelvic splanchnic nerves

• External urethral sphincter • Somatic Innervation

• Stimulation = Contraction prevents urination• Inhibition = Relaxation promotes voiding of urine• S2-S4 spinal cord levels• Pudendal nerve

(Sympathetic Motor)

(Parasympathetic Motor)

(Somatic Motor)

Bladder: Motor Innervation

Pain Innervation of the bladder• Area of bladder in contact with peritoneum

• Traditional teaching on this topic is that the region of the bladder in contact with peritoneum will be innervated by pain fibers that course alongside sympathetic fibers to the cord levels of T-12-L2. The reality is that this “pelvic pain line” is not an absolute line, but a gray area similar to lines separating dermatomes.

• Pain fibers coursing alongside sympathetic fibers travel through the hypogastric plexus or sacral splanchnic nerves to the T12-L2 vertebral levels. However, suprapubic pain dominates as a site of bladder referred pain, which is the L1 dermatome.

• Area of bladder NOT in contact with peritoneum• Pain fibers innervating the areas of the bladder NOT in

contact with peritoneum course alongside parasympathetic motor axons.

• Pain fibers from bladder areas not in contact with peritoneum ultimately synapse at the S2-S4 dermatome levels by traveling within pelvic splanchnic nerves. Synapses of pain fibers in the S2-S4 region of the cord explain bladder pain that is referred to the perineum.

Mechanosensory Innervation of the bladder• Mechanosensory afferent fibers involved in the micturition reflex

course primarily alongside parasympathetic fibers in pelvic splanchnic nerves.

Pain fibers from bladder covered by peritoneum

Pain fibers from bladder NOT covered by peritoneum ANDMechanosensory

(Sympathetic Motor)

(Parasympathetic Motor)

(Somatic Motor)

Bladder: Sensory Innervation

• Bladder filling results in stretch sensation that is transmitted from the bladder wall to the spinal cord. This afferent pathway is via sensory neurons traveling with pelvic splanchnic nerves to spinal cord levels S2-S4.

• The motor pathway begins with preganglionic parasympathetic neurons whose cell bodies are located with the in S2-S4 levels of the spinal cord (intermediolateral column).

• The axons exit the cord bundled as pelvic splanchnic nerves that join the hypogastric nerves to form the inferior hypogastric plexus.

• The preganglionic axons traverse the inferior hypogastric plexus to synapse with postganglionic neurons at ganglia located within the vesical plexus or the bladder wall.

• Postganglionic parasympathetic neurons send efferent signals to the detrusor muscle, which results in contraction.

• Postganglionic parasympathetic neurons send efferent signals to the internal urethral sphincter, which results in relaxation. This signaling is due to non-adrenergic, non-cholinergic inhibitory transmission.

• The external urethral sphincter (skeletal muscle) is innervated by the pudendal nerve (somatic motor neurons), which requires voluntary relaxation for micturition to occur.

Micturition