Urinary System
Urinary System Overview
Functions of the Urinary System
Removal of Waste Products: Primarily urea and uric acid.
Regulation of Electrolyte Balance: Involves sodium, potassium, and calcium.
Regulation of Acid-Base Homeostasis: Maintains the body's pH balance.
Organs of the Urinary System
Kidneys: Major organs of filtration.
Ureters: Tubes that connect the kidneys to the bladder.
Urinary Bladder: A storage tank for urine.
Urethra: The exit tube for urine from the bladder.
Anatomy of the Kidneys
Retroperitoneal Position
The kidneys are classified as retroperitoneal organs, meaning they are located behind the peritoneum, in the perirenal space.
The anatomical features include:
Parietal peritoneum
Fat layers (adipose tissue)
Renal vessels (artery and vein)
Hilum of the kidney
Location of the Kidneys
Positioned in the lumbar region above the waist, flanking the vertebral column.
The right kidney is typically located about 1cm lower than the left due to the liver's size.
External Anatomy of the Kidneys
Structure
Lateral Surface: Convex
Medial Surface: Concave, featuring the Renal Hilum where ureters and blood vessels enter.
Supported by three tissue layers:
Renal Fascia: Anchors the kidney.
Perirenal Fat Capsule: Fatty cushion.
Fibrous Capsule: Adheres directly to the kidney.
Internal Anatomy of the Kidneys
Regions
Cortex: The outer region of the kidney.
Medulla: Contains renal pyramids that produce urine.
Pelvis: Funnel-shaped area that collects urine and connects to the ureter.
Structure of the Medulla
Renal pyramids cone-shaped structures within the medulla.
Each pyramid empties into minor calyces, which lead to major calyces and then into the renal pelvis.
Urinary Bladder Anatomy
Structure and Function
A muscular sac located above and behind the pubic bone.
Normal bladder capacity is between 400-600 mL.
The bladder changes shape from pear-like when empty to spherical when full.
Positioned differently in males (anterior to rectum) compared to females (anterior to vagina and uterus).
Trigon of the Urinary Bladder
A triangular region formed by the ureteral orifices and internal urethral orifice, significant for urinary function.
Urethra
A smooth muscle tube that drains urine from the bladder to the outside.
Length varies: approximately 20 cm in males and 3-4 cm in females.
Blood Supply of the Urinary System
Renal Arteries and Veins
Arise from the abdominal aorta and drain into the inferior vena cava.
Each kidney has renal arteries and veins that supply and drain blood, with the left renal vein being longer than the right.
Ultrasound Imaging Techniques
Use of Doppler techniques to visualize blood flow.
Normally, a 3.5-5 MHz probe is utilized for kidney scanning.
Important findings include differentiation between renal cortex, medulla, and sinus on ultrasound.
Renal Variants and Anomalies
Common Variants
Dromedary Hump: Lateral bulge found on the kidney.
Fetal Lobulation: Indented kidney surface giving it a lobulated appearance.
Prominent Columns of Bertin: Invaginations of the renal cortex within the medulla.
Malformations
Junctional Parenchymal Defect: Triangular echogenic area indicative of renal fusion anomalies.
Duplex Collecting System: Abnormality with two renal sinuses.
Adrenal Glands Anatomy
Located above each kidney.
Comprised of two distinct parts: cortex and medulla, responsible for hormone production.
Right adrenal gland is positioned more superiorly than the left.
Measurements and Sizes
Normal Adult Kidney: Length 9-12cm, width 4-6cm, parenchyma width 13-25mm.
Measurements vary based on age, gender, and BMI.