Exam 2: The Urinary System

Urinary System components

kidneys, ureters, urinary bladder, urethra, and lots of blood vessels

The urinary system contains how many kidneys?

2 kidneys

The urinary system contains how many ureters?

2 ureters (1 for each kidney)

The urinary system contains:

A urinary bladder, 1 urethra, and lots of blood vessels

Functions of the kidney include:

- filters toxins from the blood (accumulate from metabolism)
- filters excess ions (Sodium, Potassium, Chlorine, Magnesium, etc.)
- adjusts blood ph. (removing/conserving Hydrogen)
- removes drugs
- helps adjust/control blood glucose levels
- control the manufacture of RBC
- adjusts water levels in the blood to control blood pressure

Erythropoietin

A hormone produced and released by the kidney that stimulates the production of red blood cells by the bone marrow.

Kidney Anatomy

renal cortex, renal medulla, renal pelvis

hilum of kidney

indented region on the kidney that faces the midline of the body (where blood vessels and ureter attach)

retroperitoneal of the kidney

posterior to the abdominal-pelvic wall

The kidneys are protected by:

renal capsule, adipose capsule, renal fascia

renal capsule

covers the exterior of the kidney, a thin/tough covering that holds the microscopic units of the kidney (nephron) together and helps prevent infection
Example: this covering is like a sandwich bag

nephron

functional unit of the kidney

adipose capsule

Layer of fat that cushions the kidney and holds it in place

renal fascia

tough connective tissue that holds kidney in place (most superficial covering

nephrotosis

injury to the kidney's that occurs when either the adipose capsule is depleted or when the renal fascia tears (kinking the ureter and stopping kidney function)

kidney gross anatomy

renal cortex, renal pyramids, and renal columns

renal cortex

outer zone of the kidney (looks grainy)

renal pyramids

8-18 triangular shaped area, looks straited due to lots of straight tubes inside

renal columns

grainy areas between the renal pyramids

renal medulla

part of the kidney made of the pyramids and columns

The base of the renal pyramid faces the \___

renal cortex and pointed at the renal papillae

renal papilla

tip of renal pyramid

Where is urine formed?

renal cortex and renal medulla

Where is urine released?

renal papillae

The kidney cavity

a bunch of tubes that transports urine

minor calyx

drains urine from each renal papillae

major calyx

bigger tubes formed by merger of minor calyces

renal pelvis

funnel shaped area where major calyces merge (opens into ureter)

How to trace newly formed urine:

Renal Papillae
Minor Calyx
Major Calyx
Renal Pelvis
Ureter

Urine is formed at the Renal Papillae and moves to...

Minor Calyx

After urine moves to the Minor Calyx it moves to...

Major Calyx

Next urine moves from the Major Calyx to...

Renal Pelvis

Finally urine moves from the Renal Pelvis to...

Ureter

Nephrons are made up of

glomerulus, bowman's capsule, PCT, Henle's Loop, DCT, collecting duct

glomerulus

a capillary knot

Bowman's capsule

2 layered epithelial cup, has two layers: parietal and visceral

parietal layer

outer layer of bowman's capsule

visceral layer

made of special epithelium that have tiny extensions that form openings

podocytes

special epithelium found in the visceral layer

pedicels of podocytes

extensions of podocytes that wrap around glomerulus;
contain filtration slits that permit only small molecules to pass through

fenestrations

pedicels interlaced to form openings called

proximal convoluted tubule (PCT)

highly folded tube leading out of bowman's capsule

Henle's Loop

straight loop with a hairpin turn connecting the PCT to DCT

distal convoluted tubule (DCT)

highly folded tube that connects to the collecting duct

collecting duct

long straight tube w branches that connect to other nephrons DCT and ends and opens at the Renal Papillae

What are nephrons in the cortex called?

cortico nephrons

What are nephrons in the medulla called?

medullary nephrons

Urine Formation is a 3 step process:

1. Glomerular Filtration
2. Tubular Reabsorption
3. Tubular Secretion

Glomerular Filtration

The movement/force that drives filtrate from blood into the capsular space

capsular space

space between the parietal and visceral layers of Bowman's capsule

Glomerular filtration is controlled by 3 pressures:

1. Glomerular blood hydrostatic pressure
2. Capsular hydrostatic pressure
3. Blood colloidal osmotic pressure

glomerular blood hydrostatic pressure

the forces/pressure of blood in the glomerulus pushing some filtrate OUT of the glomerulus (60mm Hg)

Under normal conditions what is the pressure of glomerular blood hydrostatic pressure?

60mm Hg (can increase or decrease with blood pressure change)

capsular hydrostatic pressure

the force of bowman's capsule driving some filtrate back INTO glomerulus (18mm Hg)

What pressure is capsular hydrostatic pressure?

18mm Hg

Blood colloidal osmotic pressure

The osmotic pressure of the blood that pulls some filtrate back INTO the glomerulus (32mm Hg)

What pressure is blood colloidal osmotic pressure?

32mm Hg

What is net filtration pressure?

10 mmHg

How do you calculate the net filtration pressure?

Glomerular blood hydrostatic pressure- (capsular hydrostatic pressure + blood colloidal osmotic pressure)
Example: 60 - (18 + 32)

What happens if the pressure is 0mm Hg in a nephron?

The nephron has failed

How to keep net filtration rates at 10mm Hg?

Using several different mechanisms

What are the different mechanisms to keep net filtration at 10mm Hg?

1. Renal Autoregulation
2. Systemic Regulation

renal autoregulation

This involves dilation and/or constriction of afferent and/or efferent arterioles to return glomerular blood hydrostatic pressure to 60mm Hg (net filtration rate of 10mm Hg)

What happens if renal autoregulation is not sufficient enough?

systemic regulation mechanisms are utilized to return pressure to 10mm Hg

Systemic regulation has 2 different outcomes?

1. When blood pressure is too high
2. When blood pressure is too low

When blood pressure is too high...

cells in the wall of the right atrium (of the heart) stretch and release Atrial natriuretic peptide (ANP)

Atrial natriuretic peptide (ANP)

A hormone, secreted by the heart, that normally reduces blood pressure, inhibits drinking, and promotes the excretion of water and salt at the kidneys.

What does ANP do?

limits sodium ion reabsorption from filtrate INTO the vasa recta.

As a result to ANP what occurs?

Sodium ions remain in filtrate, as sodium levels increase its osmotic pressure increases pulling water into the filtrate which decreases blood volume and blood pressure

What decreases blood volume and blood pressure?

sodium levels in the filtrate increases osmotic pressure, which pulls water into the filtrate

When blood pressure is too low...

in the wall of the afferent arteriole and in the wall of the DCT close to the glomerulus are pressure sensitive cells

juxtaglomerular cells

pressure sensitive cells that measure blood pressure in the afferent arteriole and filtrate pressure in DCT

When pressure is low an enzyme is released called?

renin

renin

enzyme that converts angiotensinogen to angiotensin II

Angiotensin II

- enhances dilation of afferent arteriole
- enhances constriction of efferent arteriole
- stimulates thirst centers in the hypothalamus
- stimulates the adrenal gland to release aldosterone

Aldosterone

hormone that prevents loss of sodium ions from the blood of the vasa recta INTO the filtrate to conserve Sodium ions

As sodium ions increase the osmotic pressure pulls water...

from the filtrate into vasa recta blood, which increases blood volume, blood pressure and constricts blood flow to peripheral organs

tubular reabsorption

"Keeps the good stuff"
Moves beneficial molecules from tubules INTO surrounding vasa recta blood vessels

Stuff that is reabsorbed by tubular reabsorption include:

Glucose, Sodium, Potassium, Chlorine, Calcium, Magnesium, and Water

How is Glucose reabsorbed during tubular reabsorption?

reabsorbed at the PCT using carrier protein molecules, to shuttle glucose (excess glucose is released though urine)

tubular maximum

The maximum rate of reabsorption by active transport through the nephron tubules

How are Ions reabsorbed during tubular reabsorption?

reabsorbed through diffusion

How is Water reabsorbed during tubular reabsorption?

reabsorbed through osmosis, depends on the osmotic pressure of the blood/filtrate, and by antidiuretic hormone

When aldosterone is present more \_________ is absorbed

water

Antodiuretic Hormone (ADH)

Hormone from the pituitary gland, makes the DCT and collecting tubule more permeable so that water exits these tubes and enters the vasa recta

When antidiuretic hormone (ADH) levels are high \________.

Urine volume is low and concentrated

How much filtrate is moved from the tubes to the vasa recta in tubular reabsorption?

99% of filtrate

tubular secretion

moves "bad stuff" or excess stuff from the blood in vasa recta into the tubes

Stuff that is secreted by tubular secretion include:

Nitrogen, Urea, Potassium, Sodium, Chlorine, Magnesium, Calcium, Hydrogen, Excess Water, and drugs

Why is Nitrogen secreted during tubular secretion?

contains waste that accumulates in blood from metabolism, the waste first flows into the liver and then it is procced into urea

Urea

waste product formed in the liver, filtered out of the blood by the kidneys, and excreted in urine (Urea is toxic and must exit blood and enter filtrate)

Why is Hydrogen excess secreted during tubular secretion?

to control blood ph.
(Kidney's work to keep hydrogen ions levels correct)

metabolic acidosis

hydrogen ions are NOT excreted properly and hydrogen remains in the blood and the blood becomes acidic

metabolic alkalosis

The blood is too basic due to the loss of hydrogen through vomiting

Why is excess water secreted during tubular secretion?

to help control blood volume and blood pressure

What drugs are secreted during tubular secretion?

morphine and penicillin

Where does filtrate exit?

Exits the collecting tubule at the Renal Papillae

After the fluid reaches the Renal Papillae the fluid is called?

Urine

Urine flows through:

Renal Papillae
Minor Calyx
Major Calyx
Renal Pelvis
Ureter
Bladder
Urethra

Urine begins at the renal papillae then moves to the

minor calyx