1- Basic structural and functional unit of the kidney
(1 – 1.5 million/Kidney)
- Consists of Glomerulus and Renal tubules
Nephron
2TYPES OF NEPHRON
-Cortical Nephrons
-Juxtamedullary Nephrons
385%
- Situated in the cortex of the kidney
Responsible for:
• Removal of waste products
• Reabsorption of nutrients
Cortical Nephrons
415%
- Have a longer Loop of Henle – extends deep into the
medulla region of the kidney
Responsible for:
• Concentration of urinehat enzyme produced by the juxtaglomerular cellsRenal concentration begins in theAbility to produce an acid urine depends on tubular secretion of hydrogemn
Juxtamedullary Nephrons
5RENAL FUNCTION
1. Renal Blood Flow
2. Glomerular Filtration
3. Tubular Reabsorption
4. Tubular Secretion
6RENAL BLOOD FLOW
ORDER OF FLOW
1. Renal Artery
2. Afferent Arterioles
3. Glomerulus
4. Efferent Arteriole
5. Peritubular Capillaries
6. Vasa Recta
7. Cortex and Medulla
8 receives approximately 25% of the blood pumped through the heart at all times
Human kidney
9Second step of Renal Blood Flow
Blood enters the capillaries of the nephron through the afferent arteriole
10After the blood enters the capillaries through the afferent arterioles, it then flow through the?
glomerulus and into the efferent arteriole
11-Surrounds the proximal and distal convoluted tubes
• providing for the immediate reabsorption of essential substances
from the fluids in the Proximal Convulated Tubules
• final adjustment of the urinary composition in the Distal CT
Peritubular Capillaries
12- are located adjacent to the ascending and descending loops of Henle in
juxtamedullary nephrons.
Vasa Recta
13Function of Vasa Recta
• major exchanges of water and salts take place between the blood
and the medullary interstitium
• exchange maintains the osmotic gradient (salt concentration) in
the medulla, which is necessary for renal concentration.
14Total renal blood flow
1,200 ml/min
15This consists of a coil of approximately eight capillary lobes, the
walls of which are referred to as the glomerular filtration barrier.
Glomerulus
16Glomerulus is located within
Bowman’s capsule, which forms the beginning of the
renal tubule.
17THREE GLOMERULAR FILTRATION BARRIER CELULLAR LAYERS
1. Capillary Wall Membrane
2. Basement Membrane
3. Visceral Epithelium of Bowman’s Capsule
18This differ from those in other capillaries by
containing pores and are referred to as fenestrated.
endothelial cells of the capillary wall
19This increase capillary permeability but do not allow the
passage of large molecules and blood cells
Pores
20the thin membranes covering the filtration slits formed by the
inter twining foot processes of the podocytes of the inner layer of Bowman’s capsule
21 glomerular filtration barrier contains
shield of negativity – repels molecules with a
positive charge
22-The presence of this resulting from the smaller size of the
efferent arteriole and the glomerular capillaries enhances filtration.
Hydrostatic Pressure
23regulates the flow of blood to and within the glomerulus.
- The system responds to changes in blood pressure and plasma sodium
content that are monitored by the juxtaglomerular apparatus
Renin – Angiotensin – Aldosterone System (RAAS)
24This content decreases water retention within the circulatory
system, resulting in a decreased overall blood volume and subsequent decrease in blood pressure.
Low plasma sodium
25What enzyme produced by the juxtaglomerular cells
Renin
26This passes through the alveoli of the lungs
angiotensin I
27This enzyme changes Angiostensi I to the active form Angiotensin II.
angiotensin converting enzyme (ACE)
28This corrects renal blood flow in the following ways
Angiotensin II
29substances are removed from the glomerular filtrate and returned to
the blood
Tubular Reabsorption
30Responsible for:
• Reabsorption of glucose, amino acids, and salts
in the proximal convoluted tubule
• Chloride in the ascending loop of Henle
• Sodium in the distal convoluted tubule
Active Transport
31The movement of molecules across a membrane as a result
of differences in their concentration or electrical potential on
opposite sides of the membrane.
Passive Transport
32Passive reabsorption of water takes place in all parts of the
nephron except:
Ascending loop of Henle, the walls of which are
impermeable to water
33It is passively reabsorbed in the proximal convoluted
tubule and the ascending loop of Henle
Urea
34Active transport w/ carrier SUBSTANCE
Glucose, Amino acids, Salts, Chloride, Sodium
35Passive Transport SUBSTANCE
Water, Urea, Sodium
36Renal concentration begins in the
descending and ascending loops of Henle
37Water is removed by osmosis in the
descending loop of Henle
38sodium and chloride are reabsorbed in the
ascending loop of Henle
39selective reabsorption process is called the
-serves to maintain the osmotic gradient of the medulla
countercurrent mechanism
40The final concentration of the filtrate through the reabsorption of water begins in the late distal convoluted tubule and continues in the
collecting duct
41involves the passage of substances from the blood in the peritubular
capillaries to the tubular filtrate
Tubular Secretion
42TEST FOR RENAL FUNCTION
1. Glomerular Filtrations Tests
2. Tubular Reabsorption Test
3. Tubular Secretion and Renal Blood Flow Tests
43This test estimates how much blood passes through these filters each min.
GLOMERULAR FILTRATIONS TEST
44The standard tests used to measure the filtering capacity of the glomeruli
are termed
Clearance Test
45SUBSTANCES USED FOR CLEARANCE TEST
1. B2-Microglobulin
2. Cystatin C
3. Radioisotopes
4. Urea Obsoleted Method
➔ 40% of filtered urea is reabsorbed
5. Inulin Gold Standard
➔ Exogenous procedure (risky)
6. Creatinine Most Common
➔ 24-hour urine specimen (greatest source of error)
➔ Affected by medication (Gentamicin, Cephalosporin, and
Cietidine – Tagamet)
46Normal Volume of Creatinine
Male: 107 to 139 mL/min
Female: 87 to 107 mL/min
47Tests to determine the ability of the tubules to reabsorb the essential salts
and water that have been non-selectively filtered by the glomerulus are
called
Tubular Reabsorption Test
48METHODS USED TO PRODUCE WATER DEPRIVATION
OLD TEST
1. Fishberg Test - Patients were deprived of fluids for 24 hours before
measuring specific gravity.
2. Mosenthal Test - Compared the volume and specific gravity of day and night urine samples to evaluate concentrating ability.
NEW TEST
1. Osmolality - measures only the number of particles in a solution
2. Specific Gravity - is influenced by the number and density (molecular weight) of the particles.
49Tests to measure tubular secretion of nonfiltered substances and renal
blood flow are closely related in that total renal blood flow through the
nephron must be measured by a substance that is secreted rather than
filtered through the glomerulus.
Tubular Secretion and Renal Blood Flow Test
50Obsolete because results difficult to interpret.
Phenolsulfonphthalein Test
-Also called as “PSP Test”
51Not filtered by the glomerulus but is secreted by the
peritubular capillaries.
➔ The test most commonly associated with
tubular secretion and renal blood flow
p-aminohippuric acid Test
-also called as “PAH Test”
52The ability to produce an acid urine depends on tubular secretion of hydrogen ion and secretion of ammonia
-Titratable Acidity
-Urinary Ammonia