URINARY SYSTEM

The urinary system or renal system is the system that produces, stores, and eliminates urine , a sterile liquid which contains a concentrate of various waste products that are filtered out of the blood system.

In humans it includes two kidneys, two ureters, the bladder and the urethra.

Kidneys and ureters form the upper urinary tract, whereas the bladder and the urethra belong to the lower urinary tract. URINARY SYSTEM

The female and male urinary system are very similar, differing only in the length of the urethra. URINARY SYSTEM: Clinical Anatomy

UROGRAPHY (CT) UROGRAPHY (X-ray)

The kidneys are a pair of reddish brown organs, situated on the posterior abdominal wall, one on each side of the vertebral column, behind the peritoneum (retroperitoneal). •Each kidney is bean-shaped. It has upper and lower poles, medial and lateral borders, and anterior and posterior surfaces.

•The upper pole is thick and rounded and it is in close contact with the corresponding suprarenal gland. The lower pole is is smaller and thinner than the upper pole.

•The anterior surface is irregular and flat.The posterior surface is flat.

•The lateral border is convex and the medial border is concave.

•The middle part of the medial border shows a depression called the hilus (hilum). In the hilus are seen: •the renal vein •the renal artery •the renal pelvis (upper expanded portion of the ureter) The hilum expands into a central cavity, the renal sinus, this contains the upper part of the renal pelvis and the calyces, surrounded by some fat in which are imbedded the branches of the renal vessels and nerves.

The renal sinus is lined by a prolongation of the fibrous tunic, which is continued around the lips of the hilum.

The renal calyces, from seven to thirteen in number, are cup-shaped tubes, each of which embraces one or more of the renal papillæ; they unite to form two or three short tubes, and these in turn join to form a funnel- shaped sac, the renal pelvis.

The renal pelvis, wide above and narrow below where it joins the ureter, is partly outside the renal sinus.

The renal calyces and pelvis form the upper expanded end of the excretory duct of the kidney. Each kidney is about 12 cm long, 6 cm broad and 3 cm thick, weighing 150 g males and 135 g in females.

the kidneys from behind

Vertically,the kidneys extend from the upper border of vertebra T12 to the centre of the body of vertebra L3. They are partially protected by the 11th and 12th pairs of ribs.

The right kidney is slightly lower than the left kidney because of the large area occupied by the liver.The left kidney is a little longer and narrower than the right kidney. KIDNEY LOBULATIONS

In the fetus the kidney is made up of 12 lobules.

After birth the lobules gradually fuse. KIDNEY MALFORMATIONS KIDNEY MALFORMATIONS: Horseshoe kidney COVERINGS OF KIDNEY

Innermost layer (fibrous membrane) - renal capsule.

It is continuous with the outer coat of ureter at the hilus.

Renal capsule serves as a barrier against trauma and the spread of infections to the kidney. COVERINGS OF KIDNEY

Middle layer (fatty tissue) - adipose capsule.

It protects from trauma and holds the kidney in place within the abdomen. COVERINGS OF KIDNEY

Outermost layer (perirenal fascia) The renal fascia or Gerota's fascia is a layer of connective tissue encapsulating the kidneys and the suuprarenal glands.

Anterior attachment (Toldt’s fascia): it passes anterior to the kidney, renal vessels, abdominal aorta and inferior vena cava and fuses with the anterior layer of the renal fascia of the opposite kidney.

Posterior attachment (Zuckerkandl’s fascia): it fuses with the psoas fascia and side of the body of the vertebrae.

The anterior fascia and posterior fascia fuse laterally to form the lateroconal fascia which fuses with the fascia transversalis.

Superior attachment: The anterior and posterior layers fuse at the upper pole of the kidney and then split to enclose the suprarenal gland. At the upper part of the suprarenal gland they again fuse to form the suspensory ligament of the suprarenal gland and fuse with the diaphragmatic fascia. Inferior attachment: The layers don't fuse. The posterior layer descends downwards and fuses with the iliac fascia. The anterior layer blends with the connective tissue of the iliac fossa. Transverse section, showing the relations of the capsule of the kidney (after Gerota)

Sagittal section through posterior abdominal wall, showing the relations of the capsule of the kidney (after Gerota) Floating kidney (nephroptosis)- it is a downward displacement/dropping of the kidney.

Individuals - especially thin people - in whom either the adipose capsule or the renal fascia is deficient, may develop nephroptosis.

KIDNEY: RELATIONS (anterior)

The anterior surfaces of the kidneys, showing the areas of contact of neighboring viscera CT

KIDNEY: RELATIONS (posterior)

The posterior surfaces of the kidneys, showing areas of relation to the parietes

KIDNEY: INTERNAL MACROSTRUCTURE The kidney is divided into two main areas, an external area (cortex) and an internal area (medulla), and contains a space, the renal sinus, in which the upper part of the renal pelvis is located.

Renal pelvis divides into 2-3 major calyces. These in turn divide into 7-13 minor calyces.

The cortex is dark and convoluted, the medulla is pale and striated.

Within the medulla there are 8 or more cone- shaped sections known as renal pyramids.

Narrow masses of cortical tissue extending between pyramids towards the renal sinus are called renal columns.

Radial, lighter-colored medullary rays project from the bases of the pyramids into the cortex.

Each pyramid along with the overlying cortical arch forms a lobe of kidney. KIDNEY: INTERNAL The apices of the pyramids (renal papillae) converge to the renal sinus where project into MACROSTRUCTURE calices. KIDNEY: INTERNAL MACROSTRUCTURE KIDNEY: INTERNAL MACROSTRUCTURE

ULTRASOUND KIDNEY: INTERNAL MICROSTRUCTURE

KIDNEY: VASCULAR SUPPLY

Because the major function of the kidneys is to filter the blood, a rich blood supply is delivered by the large renal arteries. Renal artery arising from the abdominal aorta. Accessory renal arteries are present in 30% of individuals. The renal artery for each kidney enters the renal hilus and successively branches into segmental arteries (5 segments: apical, upper, middle, lower, posterior) and then into interlobar arteries, which pass between the renal pyramids toward the renal cortex. The interlobar arteries then branch into the arcuate arteries, which curve as they pass along the junction of the renal medulla and cortex. Branches of the arcuate arteries, called interlobular arteries, penetrate the renal cortex. KIDNEY SEGMENTS Interlobular arteries

Afferent arterioles

Glomerular capillaries

Efferent arterioles

Peritubular Vasa rectae capillaries spuria (cortical (juxtamedullary nephrons) nephrons)

Interlobular veins

Arcuate veins

Interlobar veins

Segmental veins

Renal vein

The Lymphatic Vessels of the Kidney form three plexuses: one in the substance of the kidney, a second beneath its fibrous capsule, and a third in the perinephric fat; the second and third communicate freely with each other.

The vessels from the plexus in the kidney substance converge to form four or five trunks which issue at the hilum. Here they are joined by vessels from the plexus under the capsule, and, following the course of the renal vein, end in the lateral aortic nodes.

The perinephric plexus is drained directly into the upper lateral aortic nodes. The renal plexus is a dense nervous plexus of autonomic nerves around the renal artery.

It is supplied by rami from: celiac ganglion and plexus, aorticorenal ganglion, lowest thoracic splanchnic nerve, first lumbar splanchnic nerve, aortic plexus.

Autonomic nerves from the renal plexus follow the renal artery into the kidney through the renal hilus.

The nerve fibers follow the branching pattern of the renal artery and serve as vasomotor fibers that regulate blood volume. Sympathetic fibers constrict arterioles (decreasing urine output), while less numerous parasympathetic fibers dilate arterioles (increasing urine output).

The parasympathetic supply from vagus nerve explains the nausea and vomiting that may accompany renal pain. RENAL PELVIS AND CALYCES

Urography - CT Urography – X-ray RENAL PELVIS AND CALYCES

Within the sinus of each kidney there are short cup-shaped tubes, termed minor calyces, which encircle the renal papillæ. Since a single calyx may enclose more than one papilla the calyces are generally fewer in number than the pyramids — the former varying from seven to thirteen, the latter from eight to eighteen. The minor calyces join to form two or three short tubes, the major calyces, and these unite to form a funnel-shaped dilatation, wide above and narrow below, named the renal pelvis, which is situated partly inside and partly outside the renal sinus. It is usually placed on a level with the spinous process of the first lumbar vertebra. RENAL PELVIS AND CALYCES URETER

The ureters convey the urine from the kidneys to the urinary bladder.

Each ureter measures from 25 to 30 cm. in length, and is a thick- walled narrow cylindrical tube which is directly continuous near the lower end of the kidney with the tapering extremity of the renal pelvis.

It runs downward and medialward in front of the Psoas major and, entering the pelvic cavity, finally opens into the fundus of the bladder. 1

The ureter has 3 constrictions (like the oesophagus):

(1) at the pelvi-ureteric junction

(2) at the rim of the lesser pelvis 2 (3) at the passage through the bladder wall

3 URETER

The abdominal part (pars abdominalis) lies behind the peritoneum on the medial part of the Psoas major, and is crossed obliquely by the internal spermatic vessels.

It enters the pelvic cavity by crossing either the termination of the common, or the commencement of the external, iliac vessels (iliac part). At its origin the right ureter is usually covered by the descending part of the duodenum, and in its course downward lies to the right of the inferior vena cava, and is crossed by the right colic and ileocolic vessels, while near the superior aperture of the pelvis it passes behind the lower part of the mesentery and the terminal part of the ileum.

The left ureter, lateral to the aorta, is crossed by the left colic vessels, and near the superior aperture of the pelvis passes behind the sigmoid colon and its mesentery.

The pelvic part (pars pelvina) runs at first downward on the lateral wall of the pelvic cavity, along the anterior border of the greater sciatic notch and under cover of the peritoneum.

It lies in front of the hypogastric artery medial to the obturator nerve and the umbilical, obturator, inferior vesical, and middle hemorrhoidal arteries.

Opposite the lower part of the greater sciatic foramen it inclines medialward. At the distal end, the ureter reaches the lateral angle of the bladder, where (in the male) it is situated in front of the upper end of the seminal vesicle and at a distance of about 5 cm. from the opposite ureter; here the ductus deferens crosses to its medial side, and the vesical veins surround it.

Finally, the ureters run obliquely for about 2 cm. through the wall of the bladder and open by slit-like apertures into the cavity of the viscus at the lateral angles of the trigone. When the bladder is distended the openings of the ureters are about 5 cm. apart, but when it is empty and contracted the distance between them is diminished by one-half.

Owing to their oblique course through the coats of the bladder, the upper and lower walls of the terminal portions of the ureters become closely applied to each other when the viscus is distended, and, acting as valves, prevent regurgitation of urine from the bladder. URETER IN THE FEMALE URETER IN THE FEMALE

BLOOD SUPPLY:

Upper end - ureteral branch of renal artery.

Middle - testicular/ ovarian artery, abdominal aorta, iliac vessels.

In pelvis - branches from vescical artery, middle rectal or uterine arteries.

Venous drainage: It drains into veins that correspond to the arteries.

Lymphatic drainage: To the lateral aortic nodes and iliac nodes.

Nerve supply: The ureter is supplied by sympathetic (T10-L1) and parasympathetic (S2-S4) nerves. They reach the ureter through the renal, aortic and hypogastric plexuses. APPLIED ANATOMY renal colic – strong peristaltic waves of contraction pass down the ureter in an attempt to pass the ureteric stone forward. The spasm of the smooth muscle causes an agonizing colicky pain, which is referred to the skin areas that are supplied by these segments (T11,T12, L1 and L2) of the spinal cord, namely the flank, loin and groin.

When a stone enters the lower part of ureter, the pain is felt at a lower level and is often referred to the testes or the tip of the penis in the male and the labium majus in the female.

Sometimes, ureteral pain is referred along the femoral branch of genitofemoral nerve (L1 and L2), so that pain is experienced infront of the thigh.

Pain is often so severe that afferent pain impulses spread within the CNS, giving rise to nausea.

A ureteric stone is liable to become impacted at one of the sites of normal constriction of the ureter. An intravenous pyelogram is usually necessary. Stones in the ureter Megaloureter - may be unilateral or bilateral and shows complete absence of motility. The cause is unknown. Because of urinary stasis, ureters are prone to infection. URINARY BLADDER URINARY BLADDER

The urinary bladder is a musculomembranous sac which acts as a reservoir for the urine; and as its size, position, and relations vary according to the amount of fluid it contains, it is necessary to study it as it appears (a) when empty, and (b) when distended. In both conditions the position of the bladder varies with the condition of the rectum, being pushed upward and forward when the rectum is distended.

The Empty Bladder.—When hardened in situ, the empty bladder has the form of a flattened tetrahedron, with its vertex tilted forward. It presents a fundus, a superior and an inferior surface. When the bladder is empty it is placed entirely within the pelvis.

The Distended Bladder.— When the bladder is moderately full it contains about 0.5 liter and assumes an oval form; the long diameter of the oval measures about 12 cm. and is directed upward and forward. In this condition it presents a postero-superior, an antero-inferior, and two lateral surfaces, a fundus and a summit. MALE FEMALE

Ligaments.—The bladder is connected to the pelvic wall by condensations of pelvic fascia.

Pubovesical ligaments: in both sexes, they extend from the bladder neck to the inferior aspect of the pubic bones (extensions of pubourethral ligaments in the female and of puboprostatic ligaments in the male).

Lateral and posterior vesical ligaments (male): the former are reflections of the peritoneum from the bladder to the side-walls of the pelvis; Cardinal and uterosacral the latter correspond to the sacrogenital folds. ligaments (female) The vertex (apex) of the bladder is joined to the umbilicus by the remains of the urachus which forms the median (middle) umbilical ligament, a fibromuscular cord, broad at its attachment to the bladder but narrowing as it ascends.

The medial umbilical ligament (or cord of umbilical artery) is a paired structure covering bilaterally the obliterated umbilical arteries.

From the superior surface of the bladder the peritoneum is carried off in a series of folds which are sometimes termed the false ligaments of the bladder. The median umbilical fold covers the median umbilical ligament, and two medial umbilical folds cover the medial umbilical ligaments. There are also two lateral umbilical folds overlying the inferior epigastric vessels – arteries and veins.

Unlike the median and medial umbilical folds, the contents of the lateral umbilical fold remain functional after birth.

MALE FEMALE

In the newborn child the internal urethral orifice is at the level of the upper border of the symphysis pubis; the bladder therefore lies relatively at a much higher level in the infant than in the adult URINARY BLADDER: internal structure

Over a small triangular area, termed the trigonum vesicæ, immediately above and behind the internal orifice of the urethra, the mucous membrane is firmly bound to the muscular coat, and is always smooth.

The anterior angle of the trigonum vesicæ is formed by the internal orifice of the urethra: its postero-lateral angles by the orifices of the ureters. URINARY BLADDER: internal structure

Stretching behind the latter openings is a slightly curved ridge, the torus uretericus, forming the base of the trigone and produced by an underlying bundle of non- striped muscular fibers. The lateral parts of this ridge extend beyond the openings of the ureters, and are named the plicæ uretericæ.

Arterial supply main supply – from the superior and inferior vesical arteries, additional supply – from obturator and inferior gluteal arteries and (in females) from the uterine and vaginal arteries.

Venous drainage

To the vesical venous plexus, in turn into the internal iliac veins.

Lymphatic drainage

Mostly to external iliac nodes. A few vessels to internal iliac nodes or to the lateral aortic nodes.

Nerve supply

It is supplied by the vesical plexus of nerves which contains both parasympathetic and sympathetic components. MALE URETHRA

The urethra extends from the internal urethral orifice (at the neck of the urinary bladder) to the external urethral orifice at the tip of the penis.It is 20 -25 cm long in males.

Parts of the male urethra

1. Prostatic part (3 cm) – passes through the prostate.

2. Membranous part (1.5 – 2 cm) – surrounded by a thin voluntary muscle and its membrane.

3. Penile/spongy urethra (15 cm ) – traversing entire length of spongy body of penis.

Sphincters of the urethra

1.internal urethral sphincter – is involuntary in nature.It is supplied by sympathetic nerves(lower thoracic and upper lumbar). It controls the neck of the bladder and the prostatic urethra above the opening of the ejaculatory ducts.

2.external urethral sphincter – it is voluntary in nature and supplied by the perineal branch of pudendal nerve (S2- S4). It controls the membranous urethra and is responsible for the voluntary holding of urine. FEMALE URETHRA

It is only 4 cm long. It corresponds to the upper part of the prostatic urethra of the male. SPHINCTERS OF THE URETHRA

Male

Female Arterial supply

The male urethra is supplied by the the internal pudendal artery and by penile arteries. The female urethra is supply by vaginal artery and by inferior vescical artery.

Venous drainage

The veins drain in the prostatic plexus (male), in the vescical plexus (and in the internal pudendal veins (female)

Lymphatic supply

The lymphatics from prostatic and membranous parts of the urethra pass mostly to the internal iliac nodes and partly to the external iliac nodes. Those from the spongy parts pass mostly to the deep inguinal nodes.

Nerve supply

Male: Prostatic plexus, lesser and greater cavernous nerves. The latter carry the sympathetic supply which causes contraction of the prostatic sphincter during ejaculation, preventing ejaculate reflux into the bladder.

Female: Pelvic splanchnic nerves, vesical plexus