CAHP 463 - Urinary System and Electrolyte Balance

What filters blood and forms urine?

Kidneys

What transports urine from kidneys to urinary bladder?

Ureters

What collects and stores urine?

Urinary bladder

What transports urine from the urinary bladder to outside the body?

Urethra

What type of capsule is the kidney enclosed in?

Renal capsule (thick, fibrous)

Where do the kidneys lie?

 Either side of vertebral column & high in a depression on the posterior abdominal wall 

What type of connective tissue surrounds each kidney?

Renal fascia and renal fat

The kidneys are _____ meaning behind the parietal peritoneum

retroperitoneal

T/F - The left kidney is 1.5-2cm higher than the right

True

The ___ kidney is slightly inferior to the __ kidney

right, left (liver pushes down on right kidney)

What is the main function of the kidneys?

 Regulate volume and composition of body fluids

Kidneys remove metabolic waste and excess water and electrolytes from the?

Blood

What part of the kidney is a hollow chamber in the medial depression?

 Renal sinus

What part of the kidney is the area of entrance to the renal sinus?

Hilum

What part of the kidney is a funnel shaped sac located at the superior end of the ureter?

Renal pelvis

What part of the kidney are large tubes that merge to form renal pelvis?

Major calyces

What part of the kidney are smaller tubes that merge to form major calyces?

Minor calyces

What part of the kidney are small projections extending into each major calyx?

 Renal papilla

What part of the kidney are conical masses of tissue?

Renal pyramid

The bases of the renal pyramid orientate toward?

 Convex surface

The apices of the renal pyramid form?

Renal papilla

What part of the kidney is the inner region composed of renal pyramids?

Renal medulla

What part of the kidney is the outer region of the kidney?

Renal cortex

What part of the kidney are extensions of the cortex that dip into the medulla?

Renal columns

What part of the kidney is a fibrous capsule around the kidney?

Renal capsule 

Nephrons lie within the _____ and _____

 renal cortex, renal medulla

Where is urine formed?

Nephron

___ is the function unit of the kidney

nephron

What two parts is the nephron made up of?

Renal capsule and renal tubule

The nephron works to filter ___ by reabsorbing what is needed and excreting what is not

blood

How many nephrons does each kidney contain?

1 million

The renal tubule extends from ___ to ___

glomerular capsule, collecting duct

Filtered fluid enters the renal tubule from the?

 Glomerular capsule

The pathway through the renal tubule is?

1. Proximal convoluted tubule

2. Nephron loop

3. Distal convoluted tubule

From the distal convoluted tubules the filtered fluid emptied into?

Collecting duct → renal papillae

The renal corpuscle is made up of?

Glomerulus and glomerular capsule

The glomerulus is a cluster of capillaries that _____

filters blood

The glomerular capsule is an expansion on the end of?

The renal tubule

What receives fluid filtered at the glomerulus to be transported to the proximal convoluted tubule?

glomerular capsule

Blood flow through Glomerulus

• Blood enters glomerulus through afferent arteriole and exits after filtering through efferent arteriole

• Filtered fluid from blood is collected in glomerular capsule and heads to proximal convoluted tubule 

What type of nephron sits high in the cortex?

Cortical nephron

Cortical nephrons have ___ nephron loops

short

Most nephrons are what type?

Cortical nephrons

What type of nephron sits low in the cortex and projects deep into medulla?

Juxtamedullary nephron

Juxtamedullary nephron have ___ nephron loops

long

What type of nephrons are important in regulating water balance?

 Juxtamedullary nephron

The renal artery branches many times into small arteries leading to?

Afferent arteriole → glomerular capillaries —> efferent arteriole 

Where does the renal artery arise from?

Abdominal aorta

Where does the renal vein drain into?

IVC

T/F - the left renal vein is longer than the right?

True

Urine formation begins with?

Glomerular filtration 

What filters plasma in urine?

Glomerular capillaries

The process where the kidney selectively reclaims substances (water, electrolytes, glucose) from glomerular filtration back into the body is called?

Tubular reabsorption 

What is the movement of substances out of the peritubular capillaries into the renal tubule for excretion in the urine?

Tubular secretion

Steps of Glomerular Filtration

1. Substances move from the blood into the glomerulus into the glomerular capsule 

2. Within the glomerular capsule the glomerular capillaries are many times more permeable than other capillaries due to denestrae (tiny openings in walls) 

3. Water and small dissolved molecules and ions can be filtered, large proteins remain in blood (too large to pass through

4. Glomerular filtrate is formed as substances filter the glomerulus into the glomerular capsule → moves into renal tubule for tubular reabsorption

What is the main force that moves substances by filtration through glomerular capillary walls called?

Hydrostatic pressure of the blood inside the glomerulus 

In hydrostatic pressure of the blood inside the glomerulus the afferent arterioles has a ___ diameter than the efferent arteriole

larger

What drives filtration pressure?

 Resistance in the efferent arteriole because its diameter is smaller than the afferent arteriole which causes resistance and ultimately increases blood pressure inside the glomerulus 

Net filtration pressure = forces favoring filtration - ?

forces opposing filtration

 What are the forces favoring filtration?

Glomerulus capillary hydrostatic pressure (positive)

The Glomerular Filtration Rate (GFR) is directionally proportional  to the?

Net filtration pressure

What is the average adult GFR?

125mL/min or 180L/day

How many times is blood plasma filtered in a day?

60

T/F - Only a small percentage of filtrate is actually secreted as urine?

 True, most fluid that passes through the renal tubules is reabsorbed and re-enters plasma

What is the most commonly measured index of kidney function?

GFR 

What happens when afferent arterioles are constricted?

Less blood flows through the glomerulus, filtration pressure decreases → decrease in filtration 

What happens when efferent arterioles are constricted?

Blood backs up into the glomerulus and filtration pressure increases → increase in filtration

What is the most important in determining net filtration pressure and GFR?

Glomerular hydrostatic pressure

Why does GFR remain relatively constant?

Because of autoregulation

What is the ability of an organ to maintain a local process despite changing local conditions?

Autoregulation

What is produced by the juxtaglomerular cells and macula densa?

Renin

Renin is secreted in response to what receptors?

Baroreceptors responding to drop in blood pressure or decreasing levels of ions in nephron loop

What are the renal effects of angiotensin II?

• Help maintain sodium balance, water balance, blood pressure

• Act as a vasoconstrictor

• Stimulate aldosterone discretion → reduces sodium excreted in urine 

  • Stimulating ADH (antidiuretic hormone) secretion → helps retain water

____ is the transport of substances out of the renal tubule into the interstitial fluid which substances then diffuse into peritubular capillaries

tubular reabsorption 

What are the steps of tubular reabsorption?

1. Sodium ions are reabsorbed in the bloodstream by active transport

2. Negatively charged ions are attracted to positively charged ions 

3. As concentration of ions (solute) increases in plasma, osmotic pressure increases

4. Water moves from the proximal tubule to the capillary by osmosis 

What types of transportation is involved in tubular reabsorption?

• Active transport 

  • Renal plasma threshold reached when there is more transported substance in plasma than active transport mechanism can handle (excess spills into forming urine) 

• Osmosis

• Endocytosis : small proteins 

Tubular secretion is movement of wastes from ___ into ___

peritubular capillaries, renal tubules 

Tubular secretion of potassium ions occurs in the _____ as sodium ions are reabsorbed?

Distal convoluted tubule 

T/F - Secretion of H+ ions are important in regulating pH of body fluids

True

What substances are secrets in tubular secretion?

Drugs and ions

T/F - Active transport in tubular secretion works in the same direction as tubular reabsorption

False, opposite directions

Most tubular reabsorption (70%) occurs in the ____ tubule?

Proximal convoluted

Tubular reabsorption is the movement of substances form the ___ into the ___

 renal tubules, interstitial fluid 

The volume of substances excreted in urine is?

Glomerular filtration + tubular secretion - tubular reabsorption

 Where is ADH produced?

Hypothalamus

When is ADH released in response to?

Decreasing concentration of water in body fluids or decreasing blood volume and blood pressure

When ADH reaches the kidney it causes what to be permeable to water?

 Distal convoluted tubule → leads to urine becoming more concentrated before excreted

In the presence of no/low ADH what happens?

 Water stays in tubule leading to dilate urine

In the presence of high ADH what happens?

Distal convoluted tubule and collecting duct become permeable and water is allowed to be reabsorbed by osmosis into medullary interstitial fluid → urine is concentrated because water leaves tubule 

Urea is the byproduct of what?

 Amino acid Catabolism

The plasma concentration of urea reflects the amount of ___ in diet

protein

Urea enters renal tubules through?

 Glomerular filtration 

How much urea is reabsorbed and/or excreted?

80% is reabsorbed and 20% excreted in urine

uric acid is the product of what?

 Nucleic acid metabolism 

Uric Acid enters the renal tubules through?

Glomerular filtration

T/F - Active transport completely reabsorbs the filtered uric acid

True

How much uric acid enters urine through secretion and is excreted?

 10% 

Excessive uric acid can lead to?

Gout

Crystallized uric acid deposited in the joints can lead to?

Inflammation and extreme pain, common in great toe

What is the composition of urine?

 95% water, metabolic waste products (urea, uric acids, creatinine), small traces of amino acids and varying electrolytes