aubf prelim 2

kidney

Primary organs of the system; filter blood and form urine

Ureters

Tubes that transport urine from each kidney to the bladder

bladder

Hollow muscular organ that stores urine

Urethra

Tube that expels urine from the bladder to the external environment

sphincter muscles

Circular muscles located at the bladder neck control the opening of the urethra during urination

bean-shaped, size of an adult's fist

Shape & Size of kidney

in the retoperitoneal

Location of the kidneys

continuous filtering of the body's blood

Blood Filtration of the Kidneys

Receive up to 25% of the total cardiac output

Blood Supply in the Kidney

the kidney is Highly vascular organ.

the is is due to:

- Need for oxygen and nutrient supply

- Role in filtration of toxins and metabolic waste

- Ability to reabsorb essential substances (e.g., glucose, electrolytes)

daily filtration: 200L, urine output: 2L/day

Blood Filtration Capacity of the kidney

Nephrons

Each kidney contains approximately 1 to 1.5 million functional units called

cortical nephrons

responsible for removal of waste products and reabsorption of nutrients

cortical nephrons, 85%

______________ make up approximately _____ of the nephrons

cortex of kidney

Where are the cortical nephrons situated?

juxtamedullary nephrons

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

concentration of urine

What is the primary function of the juxtamedullary nephron

urine formation pathway

glomerulus,

proximal tubule,

loop of hence, distal convoluted tubule,

collecting duct

calyx

renal pelvis

glomerulus,

proximal tubule,

loop of hence, distal convoluted tubule,

collecting duct

calyx

renal pelvis

what is the urine formation pathway

filtration to reabsorption to secretion to excretion

major steps in urine formation

albumin

negatively charged, 69k daltons that repel the glomeruli.

25%

The kidneys receive approximately _____ of the blood pumped through the heart at all times.

pathway of blood to the kidneys

renal artery

afferent arteriole

glomerulus

efferent arteriole

peritubular capillaries

vasa recta

renal vein

renal artery, afferent arteriole, glomerulus, efferent arteriole, peritubular capillaries, vasa recta, renal vein

pathway of blood to the kidneys

hydrostatic pressure

created due to varying sizes of the arterioles, and maintains consistency of glomerular capillary pressure and renal blood flow within the glomerulus

glomerular hydrostatic pressure (55mmhg)

pushes fluid out of the glomerulus

capsular hydrostatic pressure (15mmhg)

opposes filtration

Blood Colloid Osmotic Pressure (30mmHg)

draws fluid back into capillaries

peritubular capillaries

The proximal and distal convoluted tubules is surrounded by the?

vasa recta

located adjacent to the ascending and descending loops of Henle in the juxtamedullary nephrons.

osmotic gradient

Where major exchanges of water and salts take place between the blood and medullary interstitium, maintaining?

1200ml/min

Renal Blood Flow:

600-700 ml/min

Renal Plasma Flow:

Glomerulus

filtering unit of the kidney

8 cappillary lobes capillary tuft)

How many capillary lobes does the glomerulus have?

plasma, 70k daltons

The only thing that can pass through the glomerulus with a molecular weight less than?

glomerular filtration barrier

walls of the glomerulus is called?

Bowman's capsule

where is the glomerulus located?

Three Glomerular Filtration Barrier

capillary endothelium

trilayer basement membrane

filtration diaphragm

capillary endothelium

has large open pores

trilayer basement membrane

lamina rara interna, lamina densa, lamina rara externa

filtration diaphragm

found between the podocytes of Bowman's capsule

Shield of negativity

repels molecules with positive charge even though they are small enough to pass the three layers of the barrier

podocytes

twinning foot processes form a thin membrane covering the filtration slits to further restrict large molecules of the filtrate. surround the bowman's capsule

Hydrostatic pressure

is necessary to overcome the opposition of pressures of unfiltered plasma proteins in the glomerular capillaries

juxtaglomerular apparatus

maintains the glomerular blood pressure at a relatively constant rate regardless of fluctuations in the systemic blood pressure.

Renin-Angiotensin-Aldosterone System (RAAS)

regulates 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

An enzyme produced by the juxtaglomerular cells that is secreted and reacts with the blood-borne substrate angiotensinogen, producing angiotensin I.

angiotensin I

An inert hormone that passes through the lungs and reacts with ACE to produce angiotensin II

Angiotensin-converting enzyme

ACE

Angiotensin II

corrects renal blood flow through causing vasodilation of the afferent arterioles and constriction of the efferent arterioles

Aldosterone

released by the adrenal cortex triggered through the stimulation of reabsorption of sodium and water in the PCT

tubular reabsorption

first to be affected in renal disease

The body cannot lose 120 mL of water-containing essential substances every minute

active transport

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

passive transport

movement of molecules across a membrane as a result of the differences in their concentration or electrical potential on opposite sides of the membrane.

160-180 mg/dl

Renal Threshold for Glucose:

proximal convoluted tubule

Major site of reabsorption of plasma substances

active transport

sabstances: glucose, amino acid, salts, chloride, sodium

PCT

location of glucose, amino acid, salts

ascending LOH

location of chloride

PCT, DCT

location of sodium (active)

passive transport

substance: water, urea, sodium

PCT, Descending LOH, CD

location of water

PCT, Ascending LOH

location of urea

Ascending LOH

location of sodium (passive)

TUBULAR CONCENTRATION

begins in the descending and ascending loops of Henle, where the filtrate is exposed to the high osmotic gradient of the renal medulla

countercurrent mechanism

Excessive reabsorption of water as the filtrate passes through the highly concentrated medulla is prevented by the water impermeable walls of the ascending loop

collecting duct

Where final concentration of the filtrate through reabsorption of water continues from the late DCT.

Antidiuretic hormone

"vasopressin" regulates water reabsorption in the DCT & CD through increasing or decreasing permeability

high adh

increased permeability = increased reabsorption of water = low-volume concentrated urine

Low ADH

decreased permeability = high-volume diluted urine

body's state of hydration

what is adh production determined by?

TUBULAR SECRETION

Involves the passage of substances from the blood in the peritubular capillaries to the tubular filtrate

- Eliminating waste products

- Regulating the acid-base balance

2 major functions of tubular secretion

Creatinine

waste product of muscle metabolism that is produced enzymatically by creatine phosphokinase from creatine

Glomerular Filtration Rate (GFR)

Measure rate of removal of filterable substance from blood by the kidney

INULIN clearance

reference method for clearance test

Creatinine clearance

What is the most common method to measure GFR

creatinine clearance formula

Ccr = (UR mg/dl)(UV ml/CT min)/PC mg/dl x 1.73m^2/BSA m^2

Estimated GFR (eGFR)

calculated using age, sex, and body weight in kg

0

lbs to kg

Estimated GFR (eGFR) formula

eGFR = (140-age)(weight kg )/(72)(SC mg/dl) ~ x 0.85 ~

~ if female

specific gravity and osmolality

Concentration Tests for Tubular Reabsorption

specific gravity

number and density of particles in solution

osmolality

number of particles in solution

- more preferred

1-3x (275 mOsm/kg)

normal value of osmolality

Test for Tubular Secretion & Renal Blood Flow

p-aminophippuric acid (PAH) test

phenolsulfonphthalein (PSP) test

p-aminophippuric acid (PAH) test

most commonly used; reference method

phenolsulfonphthalein (PSP) test

obsolete test; hard to interpret