To maintain:

blood composition

water balance

pH balance

electrolyte (Na) balance

retroperitoneal and at the level of the 12th rib

Right kidney is slightly lower

What are the 3 layers around the kidney?

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

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.

The Cortex

The medulla

The pelvis

What region is deep to the Cortex? 

Some of it's features?

The Renal Medulla

Has cone shaped masses called medullary or renal pyramids

It is like a basin

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

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

Glomerulus and renal tubule

[image]

• Proximal Convoluted Tubule (PCT)
• Loop of Henle (LOH)
• Descending LOH
• Ascending (LOH)
• Distal Convoluted Tubule (DCT)

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

the cortical nephrons make up 85% of the nephrons.

juxtamedullary nephrons make up 15%

What is the juxtaglomerular apparatus?

(JGA)

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

What are the 3 layers of the filtration membrane?

• 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]

1. Mechanically: physically too large to pass fenestrations
2. Electrically: Proteins and basement membrane are both negatively charged

Glomerular Filtration

Tubular Reabsorption

Tubular secretion

How does renin control BP?

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

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

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.

Water=65%

Salt=65%

nutrients=100%

H₂O=15%

Na=25%

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

Takes into account dissociation

mOsm= milliosmol

Concentration in the renal medulla is measured in mOsm

300 mOsm at the corticomedullary junction

to

1200 mOsm at the medullary-pelvis junction

Countercurrent Multiplier

Countercurrent Exchanger

• 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

• 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.

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

Water reabsorption regulated by ADH and reabsorbed from the collecting duct

• 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

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

substances or conditions that enhance urinary output

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

ex: Lasix

The last step in urine formation

substances pass from the blood into the nephron

PCT: drugs and H+ to maintain blood pH

DCT: K+

Collecting ducts: K

Penicillin: have to give every 4 hrs

Phenobarbital

Female urethra is 1.5inches

Male urethra: 8 inches

• Prostatic
• Membranous
• Spongy urethra

What is Micturition

Located retroperitoneal on the pelvic floor

Smooth muscle sac