Urinary System

What are the main functions of the urinary system?

Excretion of waste, regulation of blood volume/pressure, electrolyte balance, and acid-base homeostasis

What are the four main organs of the urinary system?

Kidneys, Ureters, Urinary Bladder, Urethra

Where are the kidneys located?

Retroperitoneal, surrounded by perirenal fat, deep to the 11th & 12th ribs

Retroperitoneal

The location of the kidneys behind the peritoneal cavity, meaning they are not enclosed within the peritoneum.

What are the three layers surrounding the kidney?

1. Renal fascia (outermost, anchors kidney)
2. Adipose capsule (cushions the kidney)
3. Fibrous capsule (innermost, prevents infection spread)

Hilum of Kidney

The concave medial part where the renal artery, vein, and ureter enter/exit.

What are the three main regions of the kidney?

1. Cortex (outer region)
2. Medulla (contains renal pyramids)
3. Renal pelvis (funnel leading to the ureter)

Renal Pyramids

Cone-shaped structures in the medulla that contain collecting ducts and are responsible for urine transport.

What is the function of the major and minor calyces?

Minor calyces collect urine from renal pyramids → Major calyces transport urine to renal pelvis.

Nephron

The microscopic functional unit of the kidney responsible for filtration and urine formation.

What are the two main components of a nephron?

1. Renal Corpuscle (Glomerulus & Bowman's Capsule)
2. Renal Tubule (PCT, Loop of Henle, DCT)

Glomerulus

A tuft of capillaries that filters blood to form the initial urine filtrate.

What are the three parts of the renal tubule?

1. Proximal convoluted tubule (PCT) – Reabsorbs nutrients
2. Loop of Henle – Concentrates urine
3. Distal convoluted tubule (DCT) – Regulates ions & pH

What is the function of the juxtaglomerular apparatus?

Regulates glomerular filtration rate (GFR) and blood pressure.

Macula Densa

Specialized cells that detect sodium (NaCl) concentration in filtrate and adjust blood flow accordingly.

What is the role of juxtaglomerular cells?

They secrete renin, which helps regulate blood pressure.

What is the pathway of renal blood flow?

Renal artery → Afferent arteriole → Glomerulus → Efferent arteriole → Peritubular capillaries/Vasa recta → Renal vein

Vasa Recta

Capillary network surrounding the nephron loop in juxtamedullary nephrons, essential for urine concentration.

What is the pathway of urine flow from formation to excretion?

Nephron → Collecting ducts → Minor calyces → Major calyces → Renal pelvis → Ureter → Bladder → Urethra

What is the function of the ureters?

Transport urine from kidneys to bladder using peristalsis.

What prevents urine backflow in the bladder?

The ureters enter at an oblique angle, compressing as the bladder fills.

What are the two urethral sphincters?

1. Internal urethral sphincter – Involuntary (smooth muscle)
2. External urethral sphincter – Voluntary (skeletal muscle)

What are the three sections of the male urethra?

1. Prostatic urethra
2. Membranous urethra
3. Penile (spongy) urethra

How does the female urethra differ from the male?

The female urethra is shorter (~3-4 cm), making women more prone to UTIs.

What are the three types of Acute Kidney Injury (AKI)?

1. Prerenal – Decreased blood flow to kidneys
2. Intrinsic – Damage to kidney itself
3. Postrenal – Obstruction of urine flow

Hydronephrosis

Swelling of the kidney due to urine buildup caused by obstruction (e.g., kidney stones).

What are the common sites of kidney stone obstruction?

1. Ureteropelvic junction
2. Crossing external iliac artery
3. Vesicoureteric junction

What is urinary retention, and what causes it?

Inability to empty the bladder, caused by prostate hypertrophy, kidney stones, neurological disorders.

Renal Papillae

The tip of the renal pyramid where urine is discharged into the minor calyx.

Minor Calyx

A small funnel-shaped structure that collects urine from a renal papilla.

Major Calyx

A larger collecting structure formed by multiple minor calyces, which drain urine into the renal pelvis.

Renal Pelvis

A funnel-shaped structure in the kidney that collects urine from major calyces and directs it to the ureter.

Renal Capsule

The thin, fibrous outer layer of the kidney that protects it from infection and trauma.

Renal Cortex

The outer region of the kidney containing nephrons responsible for filtration.

Renal Medulla

The inner part of the kidney, composed of renal pyramids and responsible for urine concentration.

Renal Pelvis

A funnel-shaped structure in the kidney that collects urine from major calyces and directs it to the ureter.

Renal Sinus

A cavity within the kidney that contains the renal pelvis, blood vessels, and fat.

Ureter

A muscular tube that transports urine from the kidney to the urinary bladder using peristalsis.

Parietal Layer of Glomerular Capsule

The outer layer of the Bowman’s capsule, composed of simple squamous epithelium, which helps structure the capsule.

Visceral Layer of Glomerular Capsule

The inner layer of the Bowman’s capsule, composed of podocytes, which help filter blood.

Podocyte

Specialized cells in the visceral layer of the glomerular capsule that wrap around capillaries and form filtration slits.

Capsular Space

The space between the parietal and visceral layers of the Bowman’s capsule where filtrate collects.

Ascending Limb of Nephron Loop

The part of the nephron loop that reabsorbs ions (Na+, Cl-), but not water, helping dilute urine.

Proximal Convoluted Tubule (PCT)

The first segment of the renal tubule, responsible for reabsorbing water, glucose, amino acids, and ions.

Distal Convoluted Tubule (DCT)

The last segment of the renal tubule, responsible for selective ion reabsorption and hormone regulation.

Abdominal Aorta

The major artery that supplies oxygenated blood to the kidneys via the renal arteries.

Renal Artery

The artery that delivers oxygen-rich blood from the abdominal aorta to the kidneys.

Inferior Vena Cava

The large vein that carries deoxygenated blood from the kidneys to the heart.

Renal Vein

The vein that drains deoxygenated blood from the kidney into the inferior vena cava.

Left Gonadal Vein

The vein that drains blood from the left testis or ovary and empties into the left renal vein.

Right Gonadal Vein

The vein that drains blood from the right testis or ovary directly into the inferior vena cava.

Left Gonadal Artery

The artery that supplies oxygen-rich blood to the left testis or ovary from the abdominal aorta.

Right Gonadal Artery

The artery that supplies oxygen-rich blood to the right testis or ovary from the abdominal aorta.

Detrusor Muscle

The smooth muscle of the bladder that contracts to push urine out during urination.

Urinary Bladder

A hollow, muscular organ that stores urine until it is excreted.

Opening of Ureter

The point where the ureters enter the bladder at an oblique angle to prevent urine reflux.

Internal Opening of Urethra

The entrance from the bladder to the urethra, controlled by the internal urethral sphincter.

Bladder Trigone

A triangular area in the bladder formed by the two ureter openings and the internal urethral orifice, which is sensitive to stretching.

Internal Urethral Sphincter

An involuntary smooth muscle that controls the release of urine from the bladder into the urethra.

External Urethral Sphincter

A voluntary skeletal muscle that allows conscious control over urination