Functions of the Renal/Urinary Systems 

- filters blood 

-maintains water balance; plasma volume 

-maintains ionic balance 

*Chloride+

*Na, K, Ca, etc. 

* What stays in what goes out

-Acid base balance

*Ph levels 

 -Excretion of wastes

-Hormones 

*Erythropoeitin and Renin 

Medulla of Kidney 

Inner layer 

-renal pyramids (tubes lined up) 

-Renal Columns (in between pyramids) 

Functional unit of the kidney (does everything) 

IN ALL KIDNEYS 

@ million per kidney 

TUBULAR COMPONENT 

 (Order of operations in kidney) 

1st--Bowmans capsule :  filters blood, st. point 

2nd--Proximal Convoluted Tubule

3rd--Loop of Henle: Descending limb/ascending limb 

4th-- Distal Convoluted Tubule: Dumps into... 

5th-- Collecting duct: from cortex to medulla

creates renal pyramids, dumps into calyces 

6th-- juxtaglomerular Apparartus  (JG apparatus): specialized cells between the arterioles and distal tubule. 

Nephrons: 

Two different types 

Cortical Nephron: 

-Most abundant type 

-80% this type

Juxtamedullary Nephron: 

-Long looped nephron. important in establishing the medullary vertical osmotic gradient

-20% this type 

-conserve water for body 

Vascular Component 

(Order of Operations) 

1) Afferent Arteriole: 

-goes to each nephron 

-brings blood in 

2) Glomerulus: 

-Tuft of capillaries 

-site of filtration.. put into tubule 

-renal corpuscle 

3) Efferent Arteriole: 

-reconverge 

-takes blood away from Bowman's 

(UNIQUE FEATURE;because it comes after a capillary) 

4) Peritubular Capillaries:

-MOVEMENT!

RENAL PHYSIOLOGY

(Kidney function is the result of 3 processes) 

1. Glomerular Filtration 

2. Tubular Reabsorption 

3. Tubular Secretion

*end result is Urine Excretion*  

Filtration of plasma from blood into the tubular component. 

* this is NON SELECTIVE, anything and everything small enough can pass through*

Absorption of water and solutes from filtrete back into the blood. 

**Very Selective**

What is Tubular Secretion? 

Secretion of solutes from the blood into filtrate 

*Selective*

20% of cardiac output goes thru the kidneys 

Filtration of Plasma from Glomerulus into Bowman's 

Everything in the plasma (except proteins) 

*non selective*

ways to measure all of this. 

How well the kidneys are doing 

About 20% of renal plasma flow 

Glomerular Filtration Rate (GFR):

Volume 

GFR= 125ml./min=180L/ day 

-entire plasma volume is filtered 65x per day 

-Filtration occurs easily from glomerulus to capsule.

 *Even across 3 layers, endothelium of capsule, basement layer, and inner layer of capsule.* 

#1. Glomerular capillaries are @100x more porous than normal capillaries 

(UNIQUE REASON, #2) 

#2. Filtration Slits create a very porous membrane in capsule. 

* allows everything to pass through except cells and plasma proteins* 

*if infection, its from the blood*

Moving fluid from capillaries, out. Similar to Bulk Flow. 

GLOMERULAR FILTRATION 

result of 3 pressures 

1. Glomerluar Capillary Blood Pressure  

-55mmHg out 

2. Plasma-colloid Osmotic Pressure 

-30mmHg In 

3. Bowman's capsule Hydrostatic Pressure 

-15mmHg In 

(3rd UNIQUE, always out..) 

*Net filtration pressure= 10mmHg OUT*

55 out, 45 in

The ability to reabsorb solutes and water from filtrate back into the blood. 

*Occurs in the rest of the Kidney*

-Very selective process 

-Active/Passive transport 

-Reabsorbs: 99% water, 100% glucose, 99.5% NaCl, Phosphates

-Reabsorbs 178.5L/ DAY 

-It's either passive or active

-Most transport is sodium or sodium linked transport 

-->Water follows sodium 

-->Glucose and Amino Acids 

GLUCOSE AND AMINO ACID REABSORPTION 

-Both are filtered, but the body wants to keep them 

-carrier mediated transport 

(work in conjunction with sodium) 

-Transport Maximum: maximal rate at which glucose and Amino acids can be reabsorbed. 

--> If filled with too much glucose it causes diabetes 

--> can detected by glucose in Urine 

--filtrate as it leaves collecting ducts 

--through calyces and pelvis to ureter 

-- Travels down the ureter  (SM contractions, peristaltic waves) to bladder. 

has a folded wall to allow expansion (800-1000ml) 

stimulates process of urination 

process of bladder emptying 

MICTURITION REFLEX 

Controls the exit from bladder and entry into the urethra 

Smooth muscle (not voluntary) 

Skeletal muscle 

voluntary 

--yellow....Urochrome (chemical) 

--Ammonia Odor 

(from nitrogenous wastes, and sometimes high protein diet) 

--Ph=4.5-8

NORMAL characteristics of URINE 

SOLUTES 

--Urea....main thing to measure kidney function 

--sodium, potassium, phosphates, calcium, magnesium, and bicarbonate. 

**If levels are normal, the blood levels are normal.**

*IF levels are high it may be indicitive of disease*

-Glucose.. diabetes indicator 

-Proteins..Infection, damage to kidneys

-Ketones.. small amounts: low levels of carbs

-Hemoglobin..RBC destruction, Kidney issues

-RBC & WBC... damage to kidneys 

Aldosterone 

Vasopression (Anti-diuretic Hormone) (ADH) 

secreted from the adrenal cortex 

~~Stimulus... decreased sodium, decreased ECF, decreased Blood Pressure (Via RAAS) 

which increases potassium directly 

Stimulates increase in sodium reabsorption in the distal tubule and collecting duct. 

END RESULTS: 

increase Na+ reabsorption 

increases water reabsorption 

Increases Blood pressure

and Increases potassium secretion  

Vasopressin/ Anti-diuretic Hormone (ADH) 

Decreases Urination. 

--Hypothalmus is the homeostasis center. It monitors osmolarity of body fluids. 

* if too concentrated, we need to retain fluids.* 

--Hypothalmus....posterior pituitary....Secretes ADH

ADH--increases water permeability in the distal tubule and collecting duct  (More water is reabsorbed) 

--Alcohol inhibits the secretion of ADH from pituitary gland which increases urine volume 

Kidneys initiate and are effected. 

-maintain and raise BP 

-Seen as a prob. with heart probs

-can be turned off

RENIN-ANGIOTENSIN-ALDOSTERONE-SYSTEM

Juxtaglomerular  Apparatus 

specialized cells: Macula Densa...Osmoreceptors (these tell how concentrated the fluids are) distal tubule. 

Juxtaglomerular Cells...secrete Renin  (Line afferent arteriole, granular cells) 

RENIN-ANGIOTENSIN-ALDOSTERONE-SYSTEM

Initial stimulus 

decreased Na+ 

Decreased extra cellular fluid 

decrease Blood Pressure 

RENIN-ANGIOTENSIN-ALDOSTERONE-SYSTEM

Order of Operation 

-initial stimulus

-Macula Densa stimulates the granular cells to produce RENIN  (Hormone fucntions as an enzyme) 

-Renin converts/ splits Angiotensinogen (which is a plasma protein) to Angiotensin I. 

-Lungs Angiotensin Convertine Enzyme (ACE) converts ANG I to ANG II (which is a strong vasoconstrictor) 

-ANG II stimulates adrenal cortex to produce Aldosterone 

-Aldosterone increases in sodium reabsorption in distal tubule and collecting ducts. 

RENIN-ANGIOTENSIN-ALDOSTERONE-SYSTEM

End Results 

-increased na+ reabsorption

-Increased H2O Absorption 

-Increased BP

ANG II stimulates: 

*Vasopressin (ADH) increased WATER REABSORPTION

*Increased THIRST 

*VASOCONTRICTION 

---so BP gets increased 

---HIgh BP system doesn't help

---If we inhibit ACE we can decrease BP 

Which of the following substances should NOT appear in the urine?

Calcium, Potassium, Sodium, Proteins, Urea

Which of the following does the Renin-Angiotensin-Aldosterone-System NOT do?

--

 increase thirst

 vasoconstrict blood vessels

increase vasopressin (ADH) secretion

Which of the following stubstances is normally secreted by the kidneys?

Water

Amino Acids

Potassium Ions

Glucose 

Sodium Ions 

Which of the following hormones is DIRECTLY responsible for increasing sodium reabsorption?

Angiotensin II

Angiotensin I 

Vasopressin/ADH

Renin 

Aldosterone 

How would Glomerular Filtration Rate (GFR) be affected by a drop in blood pressure?

No change

Increase 

Decrease 

How would activation of R-A-A-S affect urine output?

No change

Increase

Decrease

Most water that is filtered will be reabsorbed.

True 

False 

The more reabsorption that occurs, the less urine is produced.

True 

False