AUBF 20: RENAL FUNCTION

Each kidney contains approximately 1 to 1.5 million functional units called

nephron

what are the two types of nephron

cortical and juxtamedullary

responsible for removal of waste products and reabsorption of nutrients

cortical nephron

which make up approximately 85% of nephrons, are situated primarily in the cortex of the kidney

cortical nephron

have longer loops of Henle that extend deep into the medulla of the kidney

juxtamedullary nephron

primary function is concentration of the urine

juxtamedullary nephron

The ability of the kidneys to clear waste products selec ively from the blood and simultaneously to maintain the body's essential water and electrolyte balances is controlled in the nephron by the following renal functions

renal blood flow glomerular filtration tubular reabsorption tubular secretion

who supplies blood to the kidney

renal artery

the human kidney receives approximately _____ of the blood pumped through the heart at all time

25%

renal blood flow path

1. blood enters the capillaries of the nephron through the afferent arteriole

2. it then flows through the glomerulus and into the efferent arteriole

3. before returning to the renal vein blood from efferent arteriole enters the peritubular capillaries and the vasa recta and flows slowly through the cortex and medulla of the kidney close to the tubules

4. through the cortex and medulla of the kidney close to the tubules. 5.The peritubular capillaries surround the proximal and distal convoluted tubules, providing for the immediate reabsorption of essential substances from the fluid in the proximal convoluted tubule and final adjustment of the urinary composition in the distal convoluted tubule

5. The vasa recta are located adjacent to the ascending and descending loops of Henle in juxtamedullary nephrons. In this area, the major exchanges of water and salts take place between the blood and the medullary interstitium ​

the varying sizes of these arterioles help to create the _________ differential important for glomerular filtration and to maintain consistency of glomerular capillary pressure and renal blood flow within the glomerulus

hydrostatic pressure

what increases the glomerular capillary pressure

smaller size if the efferent arteriole

major exchanges of water and salts take place between the blood and the medullary interstitium

loop of henle in juxtamedullary nephrons

the exchange of water and salts maintains the ____ in the medulla which is necessary for renal concentration

osmotic gradient

it provides the immediate reabsorption of essential substances from the fluid in the ____

proximal convulated tubulue

final adjustment of the urinary composition is in the _____

distal convulated tubule

what is the total renal blood flow

1200 mL/min

total renal plasma flow ranges

600 to 700 mL/min

normal values for renal blood flow and renal function tests depend on the

body size

what is the average body surface

1.73 m2

When dealing with sizes that vary greatly from the average 1.73 m2 of body surface, a correction must be calculated to determine whether the observed measurements represent normal function, the calculation is in the

glomerular filtration rate

what are the important function of the kidney

1. elimination of the end product of metabolism

2. elimination of the excess body water

3. elimination of foreign substances like drugs

4. maintenance of electrostatic balance

5. secretion of hormone (erythropoietin)

outer area of kidney

cortex

inner area of kidney

medulla

striated, triangular structure within the medulla whose bases face the cortex and tips point to the center of the kidney (renal papillae)

renal pyramid

cortical material that extends between the pyramids

renal columns

funnel-shaped structures that surround the tip of renal pyramid

minor calyx

union of minor calyces

major calyx

union of major calyces, large collecting funnel which narrows to form ureter

renal pelvis

notch in the concave center of the kidney through which a ureters leaves the kidney and blood vessels, nerve, lymph vessels enter and exit the kidney

hilus

Responsible for selective clearing of the waste product from blood

nephron

Responsible for the maintenance of essential water and electrolyte balance

nephron

Filtering apparatus of the kidney

glomerulus

Tuft of capillary blood vessels located in Bowman's capsule where filtration process occur

glomerulus

Containing glomerulus

Bowman's Capsule

Important in order for the glomerulus to form bundles of capillaries

Bowman's Capsule

Refers to small artery

Afferent Arteriole

Small branch of renal artery through which the blood flows to the glomerulus of the kidney

Afferent Arteriole

Smallerthan the afferent arteriole (for the creation of hydrostatic pressure necessary for the filtration process to occur

efferent arteriole

Branch of renal artery through which blood flows away from the kidney

efferent arteriole

parts of renal tubular system

pct dct loop of henle cd

Part of nephron where the final concentration of the urinary filtrate begins

distal convoluted tubule

Under the influence of the hormone aldosterone, reabsorbs sodium and secretes potassium

distal convulated tubule

Also regulates pH by secreting hydrogen ion when pH of the plasma is low

distal convoluted tubule

Only 10% of the filtered NaCl and 20% of water remains

distal convoluted tubule

tubules that are found nearest to the glomerulus

proximal convoluted tubule

Part wherein the reabsorption of essential substances begin

proximal convoluted tubule

Reabsorbs: water, glucose, amino acids, and sodium.

proximal convoluted tubule

the only tubule reabsorbs glucose

proximal convoluted tubule

PCT % in Na reabsorbed

65%

PCT % in H20 reabsorbed

65%

PCT % in filtered bicarbonate (HCO3)

90%

PCT % in Cl and K reabsorbed

50%

U-shaped structure of the renal tubule

loop of henle

It contains thin descending limb and thick ascending limb

loop of henle

Control the retention of water

loop of henle

Creates a gradient of increasing sodium ion concentration towards the end of the loop within the interstitial fluid of the renal pyramid

loop of henle

thin loop of henle

descending

thick loop of henle

ascending

impermeable to water

ascending

reabsorption of water without reabsorption of salt

descending

no reabsorption of water with reabsorption of salt

ascending

Loop of Henle % in Na reabsorbed

25%

Loop of henle % in water reabsorbed

15%

Loop of henle % in K reabsorbed

40%

Where the final concentration of urine takes place through the reabsorption of water

collecting duct

Allows for the osmotic reabsorption of water

collecting duct

makes collecting ducts more permeable to water-- produce concentrated urine

ADH

Non-selective process of filtration

glomerular filtration

In glomerular filtration, what are the several factors that affect the actual filtration process

1. cellular structure of the capillary walls and bowman's capsule

2. hydrostatic and oncotic pressure

3. feedback mechanism of the renin-angiotensin-aldosterone system

Controlsthe regulation of the flow of blood to and within the glomerulus

Renin-Angiotensin-Aldosterone System

how the RAAS system respond

The system responds to changes in blood pressure and plasma sodium content that are monitored by the juxtaglomerular apparatus

juxtaglomerular apparatus consists of ______

juxtaglomerular cells in afferent arteriole macula densa of DCT

Low plasma sodium content decreases _____within the circulatory system, resulting in a decreased overall blood volume and subsequent decrease in blood pressure

water retention

Renin secreted and reacts with the blood-borne substrate _______produce the inert hormone angiotensin I

angiotensinogen

passes through the lungs ------ angiotensin converting enzyme (ACE) changes it to the active form ______

angiotensin II

Angiotensin II corrects renal blood flow in the what ways

1. causing vasodilation of the afferent arterioles and constriction of the efferent arterioles

2. stimulating reabsorption of sodium in the proximal convoluted tubules, and triggering the release of the sodium-retaining hormone aldosterone by the adrenal cortex and antidiuretic hormone by the hypothalamus

Selective filtration

tubular reabsorption

The body cannot lose 120 mL of water-containing essential substances every minute. Therefore, when the plasma ultrafiltrate enters the proximal convoluted tubule, the nephrons, through cellular transport mechanisms, begin reabsorbing these essential substances and water

tubular reabsorption

reabsorption mechanism

active transport passive transport

The substance to be reabsorbed must combine with a carrier protein contained in the membranes of the renal tubular cells

active transport

Active transport is responsible for the reabsorption of

glucose, amino acids and salts ---- PCT chloride ----- ALH sodium ---- DCT

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

Passive reabsorption of water takes place in all parts of the nephron except _______the walls of which are impermeable to water

ascending loop of henle

is passively reabsorbed in the proximal convoluted tubule and the ascending loop of Henle

urea

passive reabsorption of sodium accompanies the active transport of _____ in the ascending loop

chloride

renal threshold for glucose

160-180 mg/dL

The plasma concentration at which active transport stops is termed

renal threshold

When the plasma concentration of a substance that is nor ally completely reabsorbed reaches an abnormally high level, the filtrate concentration exceeds the ________ of the tubules, and the substance begins appearing in the urine

maximal reabsorptive capacity (Tm)

Part/mechanism wherein there is a creation of acid-base balance

tubular secretion

Several parts of kidney will produce hydrogen ion

tubular secretion

Elimination of waste products not filtered by the glomerulus

tubular secretion

Many foreign substances cannot be filtered by the glomerulus because they are bound to plasma proteins. However, when these protein-bound substances enter the peritubular capillaries, they develop a stronger affinity for the tubular cells and dissociate from their carrier proteins, which results in their transport into the filtrate by the tubular cells

tubular secretion

The major site for removal of these nonfiltered substances is the

proximal convoluted tubule

Renal concentration begins in the descending and ascending loops of Henle, where the filtrate is exposed to the high _____ of the renal medulla

osmotic gradient

This selective reabsorption process is called the ________ and serves to maintain the osmotic gradient of the medulla

countercurrent mechanism

The sodium and chloride leaving the filtrate in the ascending loop prevent dilution of the medullary interstitium by the water reabsorbed from the _______

descending loop

Maintenance of this osmotic gradient is essential for the final concentration of the filtrate when it reaches the _______

collecting duct

The final concentration of the filtrate through the reabsorption of water begins in the late distal convoluted tubule and continues in the

collecting duct

Reabsorption depends on the osmotic gradient in the medulla and the hormone

vasopressin