Anatomy of he Urinary System

The urinary system consists of the following

• Kidneys• Ureters• Urinary bladder• Urethra

The Kidney• Bean-shaped organ • It lies on the posterior

abdominal wall at the side of vertebral column

• It measures 4x2x1 inches• It has anterior and posterior

surfaces and medial and lateral borders

• Right kidney is lower than the left because of the liver

• The level of kidneys varies with respiration of about 1 inch

The Kidney Cont.,

Renal hilum • Is found at the medial concave surface• Renal vein, renal artery and ureter are

found in the hilum in anterior posterior order

• Lymphatics and sympathetic nerves pass through the hilum

Renal sinus All structures pass through the hilum in

addition to small amount of fat and the pelvis are found in the sinus

• Suprarenal glands, kidneys, and ureters and their vessels are retroperitoneal structures

• Renal capsule formed of dense connective tissue surrounding the kidneys for support and protection

• Perirenal fat a layer of fat surrounds the kidney outside the renal capsule

• Kidneys, suprarenal glands, and perirenal fat are enclosed by fascial membrane called Renal fascia

• The two layers extend medially to enclose the renal vessels and blend with vascular fascia

• The two layers extend inferiorly to enclose the ureters as as Periuretric fascia

• A layer of fat surrounding the kidneys, ureters, suprarenal glands external to renal fascia called Pararenal fat

• Perirenal fat, renal fascia, pararenal fat and some collagen fibers hold the kidneys in fixed position

• Superiorly, renal fascia is attached to inferior diaphragmatic fascia

Internal structure of the Kidney

Each kidney consists of:• Outer cortex• Inner medulla formed of

renal pyramids with apex forming renal papilla

• Cortex extends into medulla as renal columns

• Renal pelvis fills most of the sinus

• Major calyces• Minor calyces

Anterior relation of the Kidney Right kidney:• Suprarenal gland• Liver• Duodenum• Right colic flexure• Ileum Left kidney• Suprarenal gland• Stomach• Spleen• Splenic artery• Pancreas• Jejunum• Left colic flexure

Anterior relation of the Kidney

Right Kidney Left Kidney

Posterior Relation of the Kidney

• Diaphragm separates the kidney from the pleural cavity and 11th and 12th ribs

• Psoas major medially• Quadratus lumborum in

the middle, transversus abdominis laterally

• Subcostal, iliohypogastric and ilioinguinal nerves descend obliquely behind the kidney

The Ureter

• It is a muscular organ• Extends from renal pelvis in

abdomen, crosses the pelvic brim at common iliac artery bifurcation to the urinary bladder

• It 10 inches in length• On the back, extends along a

line from a point 5 cm from spine of L1 to posterior superior iliac spine

The Ureter Cont.,• The abdominal part is retroperitoneal• It runs close to the tips of transverse

processes of lumbar vertebrae as seen in contrast radiographs

• It passes vertically on psoas muscle• It enters the pelvis crossing the external

iliac artery• It shows three constriction along its course: Between ureter and pelvis At crossing the external iliac artery At entrance to urinary bladder• They are the sites of obstruction by renal

calculi

The Ureter Cont.,• Ureter runs on the lateral part of

lesser pelvis• It runs parallel to medial part of

greater sciatic notch • At level of ischial spine, it turns

anteromedially to enter the inferior surface of the bladder in inferiomedial dirction

• The enterance is 5 cm a part on external surface and 2.5 cm a part at internal surface

• Oblique passage creates a sphincter like structure at lower end of ureter

Anterior Relation of the Ureter

Sigmoid colon and mesocolon

Left gonadal vessels

Left colic vessels

Right colic vessels

Ileocolic vessels

Right gonadal vessels

Duodenum

Terminal Ileum

The Urinary Bladder• It is a hollow muscular organ• It is a pelvic organ after puberty• It lies behind and superior to pubic

bones leaving retropubic space in between

• It is divided into apex, fundus and body

• It has 4 surfaces, superior, posterior (base) and two inferiolateral

• It is freely movable except at the neck that is attached by lateral ligaments of bladder and puboprostatic ligament in male and pubovesical ligament in female

Apex

Body

Fundus

The Urinary Bladder Cont., Posterior relation in male:• Vas deferens• Seminal vesicle• Rectum• Rectovesical fascia• Peritoneum Posterior relation in female:• Vagina and part of uterus Superior relation in male:• Peritoneum• Coils of ileum• Sigmoid colon Superior relation in female:• Uterus Lateral relation• Obturator internus muscle• Levator ani muscle

The Urinary Bladder Cont., Anterior relation• Symphysis pubis• Retropubic fat Inferior relation:• Prostate gland

• The muscle of the bladder wall is called Detrusor muscle

• It is thickened at the neck to form involuntary internal urethral sphincter

• Trigone is triangular area where the two ureters and urethra open into its angles

Blood Supply of the Urinary System

Kidney:• Renal arteries are paired branches

arise from aorta at the level of intervertebral disc between L1,2

• Right one longer than the left, passes behind IVC

• At the hilum, each one divides into 5 segmental arteries each supplies a renal segment

• Renal segments are independent in their blood supply

• Blood is drained by segmental veins to renal veins

Blood Supply of the Urinary System Cont., Abdominal part of ureter:• Uretric branches from the renal

artery are constant ones.• Other branches from gonadal, aorta

and common iliac arteries• They give ascending and descending

branches that anastomose with each other

• Veins are drained by renal and gonadal veins

Blood Supply of the Urinary System Cont.,

Pelvic part of ureter• Uretric branches of common iliac, internal iliac and gonadal

arteries• Constant branches come from inferior vesical and (in female)

uterine arteries• Veins are corresponded to arteries

Blood Supply of the Urinary System Cont., Urinary bladder• Superior vesical artery• Inferior vesical artery• Vaginal artery replace inferior vesiacal

artery in female• In male, venous plexus around the

bladder and prostate drain into inferior vesical vein

• Also, superior vesical vein drains the bladder

• Both veins drain into internal iliac vein • In female, venous plexus around bladder

drain into vaginal or uterovaginal vein and then to internal iliac vein

• Also, superior vesical vein drains the bladder

Lymphatic drainage Kidney• Into left and right lumbar (aortic and caval) lymph nodes Upper ureter• To kidney lymphatics or to lumbar lymph nodes Middle ureter• To common iliac lymph nodes Lower ureter• To common , external, and internal iliac lymph nodes Pelvic ureter and bladder• To internal iliac lymph nodes

Nerve Supply • Parasympathetic fibers leads to

contraction of smooth fibers in ureter and bladder and relaxation of smooth fibers in internal urethric sphincter

• Sympathetic fibers cause the opposite effect

• Sympathetic fibers to kidney are vasomotor comes from renal plexus

• Parasympathetic fibers from S2-4 form pelvic splanchnic nerve

• Sympathetic fibers from L1-2 form inferior hypogastric plexus

Male Urethra• It is 20 cm long in male from the bladder

neck to external urethral meatus• It has a tortous course• It divides into three parts:1. Prostatic part: widest portion It is 3 cm long Most dilatable part Ducts of prostate gland and ejaculatory ducts open in it2. Membranous part: Lies within urogenital diaphragm It is 1.5 cm long Least dilatable part

Male Urethra cont.,

3. Penile part: It is 15.5 cm Is surrounded by erectile

tissue of bulb and corpus spongiosum

It is dilated at the end as navicular fossa

Bulbourethral and penile glands open in it

Female Urethra

• It is 4 cm in length and 6 mm in diameter

• Extends from neck of bladder to external meatus

• It passes under the symphysis pubis• It lies anterior to vagina• It opens in the vestibule anterior to

vaginal opening• Paraurethral glands They are mucus secreting glands located

at the sides of external meatus • It is easily dilatable• It is straight

Blood Supply of Urethra

Male Urethra• Prostatic branches of

inferior vesical and middle rectal arteries

• Dorsal artery of the penis• Arteries of the bulb of the

penis

Female Urethra• Internal pudendal artery• Vaginal artery

Nerve Supply of Urethra

• Parasympathetic supply From pelvic plexus made of S2-4 roots to form pelvic

splanchnic nerve• Sympathetic supply T12-L1-2 Form hypogastric plexus and then form pelvic• Somatic supply Pudendal nerve from sacral plexus Sensory and motor to external urethral sphincter

Surface AnatomyKidney

• Hilum of each kidney is three finger breadth from the midline in transpyloric line (L1)

• On the back, kidney extends from spine of T12 to spine of L3

• Kidney move about one inch on respiration

• Right kidney is one inch lower than the left because of liver

Ureter

• Anteriorly is represented by a line from a point 5 cm from the midline at level of L2 to a point at anterior iliac spine and from there a curved line is drawn anterior and medially to pubic tubercle

• Posteriorly is represented by a line from spine of L1 to posterior inferior iliac spine