urinary system

What organs make up the urinary system?

• Kidneys

• Ureters

• Urinary bladder

• Urethra

What are the six major functions of the urinary system?

• Excretion of wastes/toxins

• Regulation of blood pressure

• Regulation of blood pH

• Electrolyte balance

• Endocrine function (EPO & Renin)

• Vitamin D activation

Which hormone regulates blood pressure?

Renin

Which hormone stimulates red blood cell production?

Erythropoietin (EPO)

Where is Vitamin D activated?

Kidneys

Where are the kidneys located?

Which kidney sits lower?

Right kidney (because of the liver).

What covers the kidney?

• Fibrous (renal) capsule

• Perirenal fat

• Renal fascia

• Pararenal fat

What is the function of the renal capsule?

Protects the kidney and helps prevent infection.

What is a renal pyramid?

Cone-shaped area of the renal medulla containing collecting ducts.

What is a renal papilla?

The tip of a renal pyramid where urine drains into the minor calyx.

What are renal columns?

Extensions of the renal cortex between the pyramids.

What is a minor calyx?

Collects urine from one renal papilla.

What is a major calyx?

Receives urine from several minor calyces.

What is the renal pelvis?

Funnel-shaped structure that drains urine into the ureter.

What is a renal lobe?

One renal pyramid plus the surrounding cortex.

Trace urine flow from the kidney to the outside.

Minor calyx
→ Major calyx
→ Renal pelvis
→ Ureter
→ Urinary bladder
→ Urethra
→ Outside (atmosphere)

Trace blood flow into the kidney.

Renal artery
→ Segmental artery
→ Interlobar artery
→ Arcuate artery
→ Cortical radiate artery
→ Afferent arteriole

Which arteriole enters the glomerulus?

Afferent arteriole

Which arteriole leaves the glomerulus?

Efferent arteriole

What are the three capillary systems of the kidney?

• Glomerulus

• Peritubular capillaries

• Vasa recta

Function of the glomerulus?

Filters blood to form filtrate.

Function of peritubular capillaries?

Reabsorb water and nutrients; secrete wastes.

Function of the vasa recta?

Maintains the concentration gradient in the renal medulla and supplies blood to juxtamedullary nephrons.

What is a nephron?

The functional unit of the kidney that filters blood and forms urine.

What are the two main parts of a nephron?

1. Renal corpuscle

2. Renal tubule

What structures make up the renal corpuscle

• Glomerulus

• Glomerular (Bowman’s) capsule

What is the function of the renal corpuscle?

Filters blood plasma to begin urine formation.

What is the glomerulus?

A tuft (ball) of fenestrated capillaries where filtration occurs.

Why is the glomerulus called a tuft of capillaries?

Because it is a cluster of intertwined capillaries that increases surface area for efficient filtration.

What is Bowman’s (glomerular) capsule?

Cup-shaped structure that surrounds the glomerulus and collects filtrate.

What are the parts of the renal tubule?

• Proximal convoluted tubule (PCT)

• Nephron loop (Loop of Henle)

• Distal convoluted tubule (DCT)

• Collecting duct

Which part of the nephron reabsorbs the most water and nutrients?

Proximal convoluted tubule (PCT)

What is the function of the Loop of Henle?

Creates the concentration gradient needed to concentrate urine.

What is the function of the distal convoluted tubule (DCT)

Fine-tunes electrolyte and acid-base balance through selective secretion and reabsorption.

What is the function of the collecting duct?

Collects urine and adjusts water reabsorption under the influence of ADH.

What are the two types of nephrons?

• Cortical nephrons

• Juxtamedullary nephrons

Which type of nephron is most common?

Cortical nephrons (~85%)

What is the function of cortical nephrons?

Carry out most filtration and urine formation.

What is the function of juxtamedullary nephrons?

Produce concentrated urine because they have long loops of Henle extending deep into the medulla.

What are the three layers of the filtration membrane?

1. Fenestrated capillary endothelium

2. Basement membrane

3. Podocyte filtration slits (visceral layer of Bowman’s capsule)

Which layer prevents blood cells from being filtered?

Fenestrated capillary endothelium

Which layer is the main filter for proteins?

Basement membrane

What are podocytes?

Specialized cells with filtration slits that help filter blood into Bowman’s capsule.

What is Glomerular Filtration Rate (GFR)?

The amount of filtrate produced by both kidneys each minute.

What factors increase GFR?

• Increased blood pressure

• Dilation of the afferent arteriole

• Constriction of the efferent arteriole

What factors decrease GFR?

• Low blood pressure

• Constriction of the afferent arteriole

• Dilation of the efferent arteriole

What are the three processes of urine formation?

1. Glomerular filtration (blood → Bowman’s capsule)

2. Tubular reabsorption (filtrate → blood)

3. Tubular secretion (blood → tubule)

What is the Juxtaglomerular Apparatus (JGA)?

A structure where the distal convoluted tubule (macula densa) contacts the afferent arteriole. It helps regulate blood pressure, blood volume, and GFR by releasing renin.

What are the functions of the macula densa and granular (juxtaglomerular) cells?

Macula densa: Detects sodium (NaCl) concentration in the filtrate.

• Granular cells: Release renin when blood pressure or sodium is low.

When is renin released, and what is its function?

Renin is released when blood pressure, blood volume, or sodium levels are low. It activates the Renin-Angiotensin-Aldosterone System (RAAS) to increase blood pressure.

What is the trigon of the urinary bladder

: A smooth triangular area with three openings:

• Two ureter openings

• One internal urethral opening

What type of epithelium lines the ureters and urinary bladder?

Transitional epithelium (urothelium), which stretches as the bladder fills.

Name the three parts of the male urethra in order.

1. Prostatic urethra

2. Membranous urethra

3. Spongy (penile) urethra

What is the function of the detrusor muscle?

The detrusor muscle contracts during urination to empty the bladder.

What is the function of the rugae in the urinary bladder?

Rugae are folds in the bladder wall that allow the bladder to expand as it fills with urine.

What type of epithelium lines the ureter, bladder, and urethra?

• Ureter: Transitional epithelium (urothelium)

• Urinary bladder: Transitional epithelium (urothelium)

• Urethra: Mostly stratified or pseudostratified columnar epithelium, changing to stratified squamous epithelium near the external opening.

Name the three parts of the male urethra in order.

1. Prostatic urethra – passes through the prostate gland.

2. Membranous urethra – shortest segment; passes through the urogenital diaphragm and external urethral sphincter.

3. Spongy (penile) urethra – longest segment; runs through the penis and ends at the external urethral orifice.