Kidney Anatomy and Function

• Kidneys are highly vascular organs receiving 25% of cardiac output
• Kidney tissue is glandular, containing modified secretory units and specialized ducts
• Kidneys excrete urine which is produced from filtered blood plasma

Endocrine Functions of Kidneys

• Kidneys secrete erythropoietin
• Kidneys synthesize and secrete renin
• Kidneys perform hydroxylation of 25-OH vitamin D3

Urinary System Development

• The kidney is the urinary system's functional organ
• The kidneys develop from intermediate mesoderm
• Kidneys initially develop in the pelvis, ascending during development

Gross Anatomy of the Urinary System

• The kidneys are retroperitoneal
• The kidneys are positioned between T12 and L3, with the right kidney slightly lower
• The kidneys are surrounded by a renal capsule and covered by a perirenal fat capsule
• A fascial septum separates the kidneys from the adrenal glands
• The kidneys are superiorly associated with the diaphragm

Posterior Relations

• Kidneys are surrounded by perirenal fascia
• Kidneys are located against the posterior abdominal wall, overlying the quadratus lumborum, psoas major, and transversus abdominis

Movement of the Kidneys

• On inspiration, the kidneys move 2-3cm

Macroscopic Kidney Anatomy

• The kidney has a concave renal hilum
• The renal artery and vein are located at the hilum, with the vein positioned anteriorly
• The kidney consists of an outer cortex and inner medulla

Renal Structures

• Renal pyramids are present
• Renal columns are present
• Major and minor calyces are present
• Renal papillae are present
• Renal pelvis is present

Blood Supply and Drainage

• Paired renal arteries arise between L1 and L2
• The right renal artery passes posterior to the inferior vena cava (IVC)
• Renal arteries divide into 5 segmental arteries
• Renal veins lie anterior to the renal arteries
• The left renal vein is longer and receives the gonadal vein
• Renal veins drain into the IVC

Renal Columns

• Caps of cortical tissue spill over the renal pyramids forming renal columns
• Renal columns are regarded as part of the cortex

Ureters

• Ureters are paired retroperitoneal structures carrying urine to the bladder
• Ureters measure 25-35cm in length and are lined by transitional epithelium

Bladder Functions

• The urinary bladder serves as a storage reservoir for urine
• It is subperitoneal in position
• The muscular walls of the bladder allow for distension
• The bladder shape and size varies in relation to fullness

Urinary Bladder (Female)

• In females, the urinary bladder is anterior to the vagina and inferior to the uterus
• The recto-uterine and vesico-uterine pouches are related to the bladder

Urinary Bladder (Male)

• In males, the urinary bladder is directly anterior to the rectum
• The recto-vesical pouch is related to the bladder

Male Urethra

• The male urethra conveys urine from the internal urethral orifice to the external urethral orifice
• The male urethra is divided into 4 parts: pre-prostatic, prostatic, membranous, and spongy (penile)