Urinary System Flashcards
Location of the Kidneys
- Lower thoracic and upper lumbar region
- Posterior abdomen behind the peritoneum (retroperitoneal)
Paranephric Fat (pararenal fat body)
Located external to the renal fascia- the exztraperitoneal fat of the lumbar region most obvious posterior to the kidney
Renal Fascia
A membranous layer that encloses the kidneys, suprarenal glands, and perinephric fat, sends collagen bundles through the perinephric fat
Perinephric fat (perirenal fat capsule)
Surrounds the kidneys their vessels
Suprarenal Glands
- Positioned between the diaphragm and superomedial aspects of kidneys
- Enclosed by renal fascia
- Right gland: contact the liver and IVC
- Left gland: contacts the stomach, spleen, and pancreas
Surface Anatomy of Kidneys and Ureters
- Lateral to T12-L3 vertebrae
- Deep to 11th and 12th ribs
- Kidney levels change during respiration and posture alteration by 2-3 cm vertically
External Anatomy of Kidneys
Kidneys lie in the superior lumbar region of the posterior abdominal wall in a retroperitoneal position
Each Kidney has?
Anterior/posterior surfaces, medial and lateral margins, and superior/inferior poles
Hilum
The concave surface of the kidney where vessels and nerves enter and exit
Surgical approach to the kidneys
Usually through the posterolateral abdominal wall where the kidneys lie closest to the surface; incisions must be made inferior to T12 to avoid puncturing the pleural cavity
Structures found at the hilum (anterior to posterior)
- Renal vein
- Renal artery
- Renal pelvis
- Ureter
Superficial Outer Cortex
Light in color with a granular appearance and inner medulla (darker)
Medulla
Consists of 6+ renal pyramids
What is in the Renal Pyramids?
Contain urine-collecting tubules (concentration of urine by removing water)
Cortex
Composed of nephrons
Nephrons
Responsible for urine production through filtration, resorption, and secretion
What drains into the ureters?
Minor and major calices, alongside the renal pelvis
In living persons, the renal pelvis and calicos are?
Usually collapsed
Renal Arteries
Arise at the IV disk level between L1 and L2; located posterior to the renal veins
Renal Veins
The longer left renal vein passes anterior to the aorta; drain into the IVC
The renal arteries divide…
Close to the hilum into 5 segmental end arteries
Segmental end arteries
Vessels that do not significantly anastomose with other segmental arteries
Renal Segment
The area supplied by each segmental artery is an independent, surgically resectable unit
Which renal vein is longer?
The left renal vein is longer
Normal kidney function relies on?
A large volume of blood flow through the kidneys
Kidney vessels have?
Large diameters when compared to surrounding vessels
What two parts do nephrons have?
- Corpuscles
- Tubules
Corpuscle
The site of filtration
Tubules
Responsible for resorption and secretion
Each kidney has how many nephrons?
More than 1 million
The length of the nephron is lined by? Why?
Simple epithelium, allows the three processes of urine production (filtration)
Cortical Nephron
- Has short nephron loop and glomerulus further from the corticomedullary junction
- Efferent arteriole supplies peritubular capillaries
Juxtamedullary Nephron
- Has long nephron loop and glomerulus closer to the corticomedullary junction
- Efferent arteriole supplies vasa recta
The longer nephron loops allow for?
The ability to produce a concentrated urine (more resorption/secretion)
Urine Excretion
- Urine leaves the collecting system
- Enters the renal pelvis
- The remainder of the urinary system transports, stores, and eliminates urine
Ureters
A pair of muscular ducts extending from the renal pelvis to the bladder (about 25-30 cm)
Ureters run…
- Inferomedially along the transverse processes of the lumbar vertebrae
- Crosses the external iliac artery
- Run along the lateral wall of the pelvis to enter the bladder
Oblique entry into the bladder prevents?
The backflow of urine as any increase in pressure within the bladder compresses its wall and closes the distal ureters
The ureters are normally constricted in 3 places (potential sites of obstruction by ureteric stones)
- The junction with the renal pelvis
- Site of crossing the pelvic brim
- Passage through the bladder wall
Urinary Bladder
- A hollow collapsible organ with strong muscular walls composed of the detrusor muscle
- Retroperitoneal, developed by loose connective tissue, superior surface covered by peritoneum
Main parts of the urinary bladder
- Apex (anterior end)
- Fundus
- Body (lies between the apex and fundus)
- Neck
Function of Urinary Bladder
Stores and expels urine
The empty bladder lies within…
The lesser pelvis and has the shape of an inverted pyramid
As the bladder fills…
It ascends superiorly into the extraperitoneal fatty tissue of the anterior abdominal wall and enters the greater pelvis
Toward the neck of the male bladder:
Muscle fibers form the involuntary internal urethral sphincter
Urethra
- A thin-walled tube that extends from the urinary bladder to the exterior of the body
- Differs in length and function in males and females
Female Urethra
Short: ~3-4cm in length, 6mm in diameter
The female urethra passes from…
The internal urethral office of the urinary bladder to the external urethral orifice in the vestibule of the vagina; musculature surrounding the internal urethral orifice not organized into an internal sphincter
Trigone
Smooth triangular region defined by the ureteric orifices and the internal urethral orifice
Male Urethra
- 18-22cm in length
The male urethra is divided into 4 regions
- Intramural (preprostatic)
- Prostatic urethra
- Intermediate (membranous) urethra
- Spongy (penile) urethra
Intramural (preprostatic)
Surrounded by an internal urethral sphincter composed of sympathetically innervated smooth muscle
Prostatic Urethra
Passes through the prostate gland
Intermediate (membranous) urethra
Surrounded by the somatically innervated external urethral sphincter
Spongy (penile) urethra
Passes through the length of the penis
UTIs
Women may be up to 30x more likely to get them than men
- Length of the urethra (women’s is shorter)
- Placement of urethra (women’s is located closely to anus/rectum)
- Sexual contact
- Sensitive perineum in women
- Contraception (spermicide)
Effects of the Sympathetic Stimulation
- Vasoconstriction of renal vessels slows urine formation
- Internal sphincter of bladder contracted to maintain urinary continence
Effects of the Parasympathetic Stimulation
- Inhibits contraction of internal sphincter of bladder
- Contracts detrusor muscles of bladder wall, causing urination
Nerves to the kidneys and ureters arise from?
The renal nerve plexus, and consist of sympathetic, parasympathetic, and visceral sensory fibers
The renal plexus is supplied by fibers of the?
Abdominopelvic splanchnic nerves (particularly the least, T12 level)
Sympathetic Innervation
Constricts blood flow to kidneys, decreasing overall kidney output
Parasympathetic Innervation
Increases blood flow to the kidneys
Medical imaging
MRI shows the kidneys close relationship to surrounding viscera
Pyelonephritis
An infection of the kidneys that has spread from the renal pelvis and calyces to the entirety of the kidney
- Bloodborne bacteria multiplying in the kidneys
- Fecal bacteria traveling up urinary tract (Escherichia coli)
- Pus may fill in worst case scenario
Renal Transplantation
- The transplanted kidney is in the iliac fossa of the greater pelvis
- The renal artery and vein are joined to the external iliac artery and vein, the ureter is sutured into the urinary bladder
Renal and Ureteric Caluli
Excessive dissension of the ureter due to a renal calculus (kidney stone) causes severe intermittent pain (ureteric colic)
- May cause complete obstruction of urinary flow
- Pain may be inferred elsewhere
