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A&P Chapter 24 The Urinary System
The Urinary System
71
Biology
Undergraduate 2
05/04/2013

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Term
What are the homeostatic functions of the kidney?
Definition

To maintain:

 

blood composition

 

water balance

 

pH balance

 

electrolyte (Na) balance

Term
Where are the kidneys located?
Definition

retroperitoneal and at the level of the 12th rib

 

Right kidney is slightly lower

 

Term
What does retroperitoneal mean?
Definition
Outside and behind the peritoneal cavity
Term
What is the renal hilum?
Definition
medial cleft for the entrance and exit of blood vessels and the ureter
Term

What are the 3 layers around the kidney?

 

 

Definition

Renal Fascia: CT sheet that surrounds kidney and anchors kidney to the body

 

Perirenal fat capsule: protects kidney and helps hold it in place

 

Fibrous Capsule: on surface of kidney, prevents infections from getting to the kidney

Term
What is Renal Ptosis?
Definition

The kidney can drop due to loss of perirenal fat  and can cause a kink in the ureter.

 

this can cause presser inside the kidney.

Term
What is hydronephrosis?
Definition
hydronephrosis: "water in the kidney" Kidney cannot release contents (i.e. renal pstosis)
Term
What are the 3 internal regions of the kidney?
Definition

The Cortex

 

The medulla

 

The pelvis

Term

What region is deep to the Cortex? 

 

Some of it's features?

Definition

The Renal Medulla

 

Has cone shaped masses called medullary or renal pyramids

Term
What are significant features of the Renal Cortex?
Definition
Granular due to glomeruli
Term
What are significant features of the renal medulla?
Definition
Has renal pyramids which are striped due to collecting tubes
Term
What are significant features of the renal pelvis?
Definition

It is like a basin

 

Has Major Calyces which lead to minor calyses which connect to papillary area of renal pyramids

Term

What is the path of urine, from creation to excretion?

 

Definition
Renal pyramids-> Minor Calyce-> Major Calyce-> renal pelvis->ureter->bladder->urethra
Term
How much cardiac output do kidneys recieve?
Definition
Kidneys recieve 1/4 of CO
Term
What is the functional unit of the kidney?
Definition
the Nephron
Term
about how many nephrons in each kidney?
Definition
1 million
Term
What two parts does a Nephron consist of?
Definition

Glomerulus and renal tubule

 

[image]

Term
What is the Glomerulus?
Definition
A tuft of capillaries
Term
What is the Glomerular Capsule?
Definition
A filter that surrounds the glomerulus like a baseball glove around a baseball
Term
What is the renal corpuscle?
Definition
The glomerulus together with the glomerular capsule
Term
What is the fluid called that enters the glomerular capsule?
Definition
Filtrate
Term
What are the sections of the renal tubule?
Definition
  • Proximal Convoluted Tubule (PCT)
  • Loop of Henle (LOH)
    • Descending LOH
    • Ascending (LOH)
  • Distal Convoluted Tubule (DCT)
Term
Diagragm of a Nephron
Definition
[image]
Term
When does filtrate start to be called urine?
Definition
When it reaches the collecting duct
Term
What is the difference between cortical nephrons and juxtamedullary nephrons?
Definition

A cortical nephron has a short LOH and its glomerulus is further from the corticomedullary junction. Efferent arteriole serves peritubular capillaries.

 

A juxtamedullary nephron has a long LOH and its glomerulus is is close to the corticomedullary junction. Efferent arteriole serves the vasa recta

Term
Are there more cortical nephrons or juxtamedullary nephrons?
Definition

the cortical nephrons make up 85% of the nephrons.

 

juxtamedullary nephrons make up 15%

Term
What are the peritubular capillaries?
Definition
Peritubular capillaries form from the efferent arteriole that drains the glomerulus and they surround the renal tubules of cortical nephrons
Term
What is the vasa recta?
Definition
the vasa recta is formed from the efferent arteriole from the glomeruli of juxtamedullary nephrons and it is a capillary bed that surrounds the long loop of henle.
Term
How much filtrate does the glomerulus create each day?
Definition
180 L/ day
Term
How much of the water from the filtrate is reabsorbed?
Definition
99%
Term

What is the juxtaglomerular apparatus?

(JGA)

Definition
The juxtaglomerular apparatus is located near the afferent and efferent arterioles and has JG cells which have large secretory granules containing renin which act as mechanoreceptors that sense blood pressure.
Term
What is the filtration membrane?
Definition

A fenestrated membrane that lies between the blood and the interior of the glomerular capsule.

 

Allows water to pass through and solutes smaller than a plasma protein

Term

What are the 3 layers of the filtration membrane?

 

Definition
  • the fenestrated endothelium of the glomerular capillaries
  • the visceral membrane of the glomerular capsule which is made of podocytes
  • The basement membrane composed of the fused basal lamina of the other 2 layers[image]
Term
What two way are proteins held back from the filtrate?
Definition
  1. Mechanically: physically too large to pass fenestrations
  2. Electrically: Proteins and basement membrane are both negatively charged
Term
What are the three processes of urine formation?
Definition

Glomerular Filtration

 

Tubular Reabsorption

 

Tubular secretion

Term

How does renin control BP?

 

Definition

When BP is low, there isn't much stretch on the JG cells and causes them to release renin.

 

LOW BP->increases renin->angiotensin becomes angiotensin1 ->angiotensin2 by ACE in lung capillaries->vasoconstriction and increase in BP.

 

also causes aldosterone to be releases which increase BP

Term
Where does most of the reabsorption occur?
Definition
Most reabsorption occurs in the proximal convoluted tubule (PCT)
Term
What adaptation do the cells of the PCT have to aid in reabsorption?
Definition
microvilli
Term
What is the process of Primary Active Transport within the PCT
Definition

Sodium Potassium pump within PCT cells pump NA out of the cell. 

The lower concentration gradient within the cell allows Na from the filtrate to enter the cell

Term
What is the process of secondary active transport?
Definition
When Na enters the cells, There are carriers along the luminal membrane that allow Na to bring along with it other nutrients from the filtrate.
Term
What does Tm mean?
Definition

Tm=transport Maximum.

 

Each substance (glucose, amino acids, vitamins, etc.) has its own transport protein on the luminal surface of the PCT. When all the transport proteins are saturated, the rest of that substance is excreted in the urine.

Term
how much water and salt and nutrients are reabsorbed in the PCT?
Definition

Water=65%

 

Salt=65%

 

nutrients=100%

Term
How much H2O and Na does the Loop of Henle reabsorb from the filtrate?
Definition

H2O=15%

 

Na=25%

Term
What does the term Osmolality mean?
Definition

it refers to concentration, the # of particles in a liter.

Takes into account dissociation

Term
What does mOsm mean?
Definition

mOsm= milliosmol

 

Concentration in the renal medulla is measured in mOsm

Term
What is the osmolarity of solutes in the plasma and of filtrate in the renal cortex?
Definition
300 mOsm
Term
What is the range of osmolality in the renal medulla
Definition

300 mOsm at the corticomedullary junction

 

to

 

1200 mOsm at the medullary-pelvis junction

Term
What are the two mechanisms of Na and H2O reabsorption in the loop of Henle?
Definition

Countercurrent Multiplier

 

Countercurrent Exchanger

Term
What are the two factors that allow the countercurrent multiplier to function?
Definition
  • The descending limb is permeable to water
  • The ascending limb is permeable to Na, but not water.

Water leaves the descending limb so filtrate that rounds the bend is more concentrated

 

Because filtrate is more concentrated, salt removal is more efficient.

 

As a result the space surrounding the LOH is very salty, which creates an osmotic draw which pulls out more water= positive feed-back system

Term
How does the Counter Current Exchanger work?
Definition
  • NaCl diffuses into the descending limb of the vasa recta capillary
  • At the ascending limb, as it gets to less salty medullary tissue salt diffuses out.

therefore, salt is left in the medulla to provide the environment to reclaim water.

Term
The last 25% of water and 10% of salt reabsorption is regulated by what?
Definition

Na reabsorption regulated by Aldosterone and occurs in the DCT and Collecting duct

 

Water reabsorption regulated by ADH and reabsorbed from the collecting duct

Term
How does aldosterone regulate Na reabsorption?
Definition
  • Aldosterone secretion is controlled by the renin-angiotensin mechanism- conditions such as decreases BP, low extracellular Na concentration(hyponatremia) or high K concentration (hyperkalemia) triggger it.
  • Aldosterone from the adrenal cortex stimulates Na reabsorption in exchange for K
Term
How does ADH regulate water reabsorption?
Definition

In the absence of ADH, the collecting ducts are impermeable to water. ADH makes the collecting ducts more permeable to water by inserting auquaporins into the luminal membranes of the collecting duct.

 

Water then leaves the urine by osmosis due to the high Na concentration in the medulla

Term
What other component other than NaCl contributes to the high medullary osmotic gradient?
Definition
Urea: It diffuses out of the Collecting duct.
Term
What is the overall effect of the vasa recta as a counter current exchanger?
Definition
it takes away the reabsorbed water but leaves the salt in the medullary tissue.
Term
how is dilute urine formed?
Definition
Dilute urine is formed naturally, by lack of reabsorption (ADH) in the Collecting duct.
Term
What is Facultative Reabsorption?
Definition
Reabsorption according to body need. When water is reabsorbed from the Collecting duct due to the presence of ADH.
Term
What are diuretics?
Definition

substances or conditions that enhance urinary output

 

 

Term
What is an osmotic diuretic?
Definition
High blood glucose
Term
What are Loop Diuretics?
Definition

inhibit Na symporters in the Loop of Henle. Powerful because the inhibit formation of the medullary gradient.

 

ex: Lasix

Term
What is tubular secretion?
Definition

The last step in urine formation

 

substances pass from the blood into the nephron

Term
What various substances get secreted back into the nephron and where?
Definition

PCT: drugs and H+ to maintain blood pH

 

DCT: K+

 

Collecting ducts: K

Term
What are some drugs that are easily secreted into the urine?
Definition

Penicillin: have to give every 4 hrs

 

Phenobarbital

Term
How do the ureters excrete urine?
Definition
Smooth muscle in ureters causes peristalsis of urin
Term
What is the difference between the urethra of a male and female
Definition

Female urethra is 1.5inches

 

Male urethra: 8 inches

Term
What are the 3 regions of the male urethra?
Definition
  • Prostatic
  • Membranous
  • Spongy urethra
Term

What is Micturition

 

Definition
Urination
Term
Explain the anatomy of the urinary bladder
Definition

Located retroperitoneal on the pelvic floor

 

Smooth muscle sac

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