ANAPHY: U14 Urinary System

Urinary System

Essential for maintaining homeostasis by regulating body fluids, electrolyte balance, and waste elimination

Kidneys, Ureters, Urinary Bladder, Urethra

4 Primary Components of the Urinary System

Kidneys

One of the 4 Primary Components of the Urinary System

Filter blood and produce urine

Ureters

One of the 4 Primary Components of the Urinary System

Transport urine from the kidneys to the bladder

Urinary Bladder

One of the 4 Primary Components of the Urinary System

Stores urine until excretion

Urethra

One of the 4 Primary Components of the Urinary System

Eliminates urine from the body

WBEEPD

Acronym for the 6 Functions of the Urinary System

1. Water & Electrolyte Balance

2. Blood Pressure Regulation

3. Waste Excretion

4. Erythropoiesis Support

5. pH Homeostasis

6. Detoxification

6 Functions of the Urinary System

Waste Excretion

One of the functions of the urinary system

In which the urinary system removes nitrogenous wastes (urea, uric acid, ammonia) and eliminates toxins and drugs through urine

Urea, Uric Acid, Ammonia

What nitrogenous wastes does the urinary system remove?

Toxins and Drugs

Aside from nitrogenous wastes, what other substances are eliminated through urine?

Water & Electrolyte Balance

One of the functions of the urinary system

Regulates sodium (Na+), potassium (K+), calcium (Ca2+), and chloride (CI-); Maintains osmolarity for proper cellular function.

Sodium (Na+), Potassium (K+), Calcium (Ca2+), Chloride (CI-)

What ion levels does the urinary system regulate?

Osmolarity

What does the urinary system have to maintain for proper cellular function?

Blood Pressure Regulation

One of the functions of the urinary system

Releases renin to activate the renin-angiotensin-aldosterone system (RAAS); Adjusts blood volume by altering water reabsorption

Renin

What does the urinary system release to regulate blood pressure?

Renin-Angiotensin-Aldosterone System

What process does the urinary system activate to regulate blood pressure?

Water Rebsorption

What does the urinary system alter to adjust blood volume?

pH Homeostasis

One of the functions of the urinary system

Balances hydrogen ion (H+) and bicarbonate (HCO3-) levels; Prevents acidosis or alkalosis.

Hydrogen Ion (H+) and Bicarbonate (HCO3-) Levels

What pH-related ion levels does the urinary system balance?

Acidosis & Alkalosis

What pH-related conditions does the urinary system prevent?

Erythropoiesis Support

One of the functions of the urinary system

Produces erythropoietin (EPO), stimulating RBC production

Erythropoietin

What does the urinary system produce that stimulates RBC production?

Detoxification

One of the functions of the urinary system

Eliminates metabolic byproducts and foreign substances

Kidneys

Bean-shaped organs located retroperitoneally on either side of the spine; 10-12 cm long, 5 cm wide

10-12 cm

How long are the kidneys?

5 cm

How wide are the kidneys?

Ureters

Thin muscular tubes (25-30 cm long) that propel urine via peristalsis to the bladder

25-30 cm

How long are the ureters?

Peristalsis

How do the ureters propel urine to the bladder?

Urinary Bladder

Hollow, muscular organ capable of expanding; Stores ~400-600 mL of urine under normal conditions

400-600 mL

What volume of urine is the urinary bladder capable of storing?

Urethra

Single tube leading from the bladder to the external environment; 4 cm in females, 20 cm in males

4 cm

How long is the urethra in females?

20 cm

How long is the urethra in males?

Vascular Supply

Renal arteries deliver ~20-25% of cardiac output to the kidneys & Renal veins return filtered blood to systemic circulation.

Renal Arteries

What component of vascular supply deliver ~20-25% of cardiac output to the kidneys?

20-25%

What percentage of cardiac output do the renal arteries deliver to the kidneys?

Renal Veins

What component of vascular supply returns filtered blood to systemic circulation?

Renal Capsule, Adipose Capsule, Renal Fascia

3 Parts of the External Structure of the Kidney

Renal Capsule

Part of the external structure of the kidney

Fibrous outer layer for protection

Adipose Capsule

Part of the of external structure of the kidney

Cushioning layer of fat

Renal Fascia

Part of the of external structure of the kidney

Anchors kidneys to surrounding structures

Cortex, Medulla, Renal Pelvis, Major & Minor Calyces, Hilum

5 Main Parts of the Internal Structure of the Kidneys

Renal Cortex

One of the main parts of the internal structure of the kidney

Outer layer containing renal corpuscles

**Contain glomeruli, proximal and distal convoluted tubules, nephrons, and other blood vessels

Renal Cortex

What is the site of initial blood filtration in the kidneys?

Renal Medulla

One of the main parts of the internal structure of the kidney

Inner layer with renal pyramids and loops of Henle

**Beneath the renal cortex

Renal Pyramid

Part of the internal structure of the kidney

Cone-shaped structures in the renal medulla

Renal Papilla

Part of the internal structure of the kidney

At the apex of each renal pyramid; drains urine into the minor calyx

Minor Calyx

Part of the internal structure of the kidney

Where the renal papillae drain into

Renal Columns

Part of the internal structure of the kidney

Extensions of the cortex that separate the renal pyramids; provide passage for blood vessels

Major & Minor Calyces

One of the main parts of the internal structure of the kidney

Direct urine to the renal pelvis

Major Calyx

Part of the internal structure of the kidney

Formed by the convergences of minor calyces and empty into the renal pelvis

Hilum

One of the main parts of the internal structure of the kidney

Entry/exit for renal arteries, veins, lymphatics, and ureters

Renal Pelvis

One of the main parts of the internal structure of the kidney

Funnel-shaped cavity collecting urine

**Connects to the ureter

Nephron

Functional unit of the kidney

~1 million

How many nephrons are there per kidney?

Renal Corpuscle & Tubular System

2 General Components of the Nephron

Renal Corpuscle

One of the general components of the nephron

Composed of the Glomerulus & Bowman’s Capsule

**Initial filtering component located in the renal cortex

Glomerulus

Part of the renal corpuscle (one of the general components of the nephron)

Capillary tuft for filtration

Bowman’s Capsule

Part of the renal corpuscle (one of the general components of the nephron)

Encases glomerulus; collects filtrate

Podocytes

Specialized cells located in the inner layer of Bowman’s Capsule which further filtration of the blood

Tubular System

One of the general components of the nephron

Composed of the Proximal Convoluted Tubule, Loop of Henle, Distal Convoluted Tubule, Collecting Duct

Proximal Convoluted Tube (PCT)

Part of the tubular system (one of the general components of the nephron)

Reabsorbs most water, ions, and nutrients

**Located in cortex; first section after renal corpuscle; reabsorbs 70-80% water, sodiium, chloride, glucose, amino acids into blood stream; secretes waste products, like hydrogen ions and certain drugs into tubule

Loop of Henle/Nephron Loop

Part of the tubular system (one of the general components of the nephron)

Creates medullary osmotic gradient

**Dives into medulla and returns into cortex; has a descending limb that is permeable to water but not solutes, water leaves which concentrates the filtrate AND an ascending limb, which is permeable to solute, especially sodium and chloride, but not water

Distal Convoluted Tubule (DCT)

Part of the tubular system (one of the general components of the nephron)

Fine-tunes ion and pH balance

**Located in the cortex; regulates ion exchange, especially sodium, potassium, and calcium; regulates through hormonal control (ADH & aldosterone)

Collecting Duct

Part of the tubular system (one of the general components of the nephron)

Concentrates and transports urine to renal pelvis

**Reabsorbs water under ADH control to concentrate urine

Cortical & Juxtamedullary Nephrons

2 Types of Nephrons

Cortical Nephrons

One of the types of nephrons

Short loops; majority of nephrons

Juxtamedullary Nephrons

One of the types of nephrons

Long loops; critical for urine concentration

Renal Pyramid

What specific internal part of the kidney are nephrons located in?

1. Filtration

2. Reabsorption

3. Secretion

3 Steps in the Process of Forming Urine

Filtration

One of the stages in the process of forming urine

Blood enters the glomerulus through the afferent arteriole

High hydrostatic pressure forces plasma and small molecules through the glomerular membrane into the Bowman’s capsule and larger molecules like proteins and blood cells remain in the bloodstream

Glomerulus

Where does Filtration mainly occur?

Reabsorption

One of the stages in the process of forming urine

Filtrate moves into the renal tubules; essential substances are taken into the peritubular capillaries and Loop of Henle will establish a concentrated gradient in the medulla

Proximal Convoluted Tubule (PCT) & Loop of Henle

Where does Reabsorption mainly occur?

Secretion

One of the stages in the process of forming urine

Additional waste products, such as hydrogen ions, potassium, and ammonia are actively transported from the blood into the tubules, eliminating toxins and regulating blood pH

Proximal Convoluted Tubule (PCT) & Distal Convoluted Tubule (DCT)

Where does Secretion mainly occur?

Afferent Arteriole

What is the structure that brings the fluid from glomerulus to the renal tubules?

True

True or False: Loop of Henle is a convoluted tubule.

Aldosterone & ADH

Key Hormones that Regulates Nephrons

Aldosterone

One of the key hormones that regulates nephrons

Increases sodium/solute/ion reabsorption

Antidiuretic Hormone (ADH)

One of the key hormones that regulates nephrons

Enhances water reabsorption in collecting duct

PCT; collecting ducts

Ions are especially reabsorbed in the ___ and water in the ___

Parathyroid Hormone

Hormone that causes calcium reabsorption in the distal convoluted tubule (DCT)

Distal Convoluted Tubule (DCT)

Calcium reabsorption occurs in the ___

1. Glomerular Filtration

2. Tubular Reabsorption

3. Tubular Secretion

4. Excretion

4 Stages of Urine Formation

Glomerular Filtration

One of the 4 Stages of Urine Formation

In which ~180L of plasma is filtered daily; Hydrostatic pressure drives water and solutes into Bowman's capsule; Large molecules (e.g., proteins) and blood cells are excluded

~180 L

During glomerular filtration, what volume of plasma is filtered daily?

Hydrostatic Pressure

During glomerular filtration, what drives water and solutes into Bowman’s capsule?

Large Molecules (like proteins) & Blood Cells

During glomerular filtration, what are excluded from being filtered?

Tubular Reabsorption

One of the 4 Stages of Urine Formation

Reclaims -99% of filtered water, glucose, and ions; Occurs mainly in the PCT

~99%

During tubular reabsorption, how much filtered water, glucose, and ions are reclaimed?

Filtered Water, Glucose, Ions

During glomerular filtration, ~99% of what is reclaimed?

Tubular Secretion

One of the 4 Stages of Urine Formation

Occurs primarily in DCT and Collecting Ducts; Active transport of wastes (e.g., H+, K+, drugs) into tubular fluid; Final adjustments to urine composition

Excretion

One of the 4 Stages of Urine Formation

Urine is expelled from the body via the urethra

1. Fenestrated Endothelium

2. Basement Membrane

3. Podocytes

3 Layers the Filtration Membrane is Composed of

Fenestrated Endothelium

One of the 3 Layers the Filtration Membrane is Composed of

Allows passage of small solutes and water

Basement Membrane

One of the 3 Layers the Filtration Membrane is Composed of

Restricts larger molecules (like proteins).

Podocytes

One of the 3 Layers the Filtration Membrane is Composed of

Specialized epithelial cells with filtration slits