Function 1.Remove nitrogenous wastes 2.Maintain electrolyte, acid-base, and fluid balance of blood 3.Homeostatic organ 4.Acts as blood filter 5.Release hormones: calcitriol & erythropoietin

Kidneys as Filters Diuretic- lose water; coffee, alcohol Antidiuretic- retain water; ADH Aldosterone- sodium & water reabsorption, and K + excretion GFR= 180 liters (50 gal) of blood/day liters are reabsorbed back into blood Excrete a protein free filtrate

renal cortex renal medulla Each kidney contains over 1 million nephrons and thousands of collecting ducts Collecting duct Loop of Henle PCT DCT Glomerulus

Nephron’s functions: 1.glomerular filtration 2.tubular reabsorption 3.tubular secretion

Histology of a renal corpuscle

Pressures that drive glomerular filtration

The filtration membrane

Nephron

Composition of Glomerular Filtrate Water Small Soluble Organic Molecules Mineral Ions

Proximal Convoluted Tubule Reabsorbs: water, glucose, amino acids, and sodium. 65% of Na + is reabsorbed 65% of H 2 O is reabsorbed 90% of filtered bicarbonate (HCO 3 - ) 50% of Cl - and K +

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. 25% Na+ is reabsorbed in the loop 15% water is reabsorbed in the loop 40% K is reabsorbed in the loop

Distal Convoluted Tubule Under the influence of the hormone aldosterone, reabsorbs sodium and secretes potassium. Also regulates pH by secreting hydrogen ion when pH of the plasma is low. only 10% of the filtered NaCl and 20% of water remains

Collecting Duct Allows for the osmotic reabsorption of water. ADH (antidiuretic hormone)- makes collecting ducts more permeable to water-- produce concentrated urine

From the original 1800 g NaCl, only 10 g appears in the urine Urine Water- 95% Nitrogenous waste: urea uric acid creatinine Ions: sodium potassium sulfate phosphate

Nitrogenous Wastes ammonia urea uric acid

Hormonal Control of Kidney Function

Fig

Hormonal Control of Kidney Function hypothalamus posterior pituitary antidiuretic hormone collecting ducts

aldosterone

Fig Regulation of Aldosterone secretion by renin-angiotensin- aldosterone (RAA) pathway

Hormonal Control of Kidney Function reduced blood pressure and glomerular filtrate juxtaglomerular apparatus renin

Hormonal Control of Kidney Function renin angiotensinogen angiotensin I angiotensin II

Hormonal Control of Kidney Function adrenal cortex aldosterone angiotensin II convoluted tubules

Urinary Bladder ureters internal sphincters external sphincters urethra

Bladder 1.Mucosa (transitional epithelium) 2.Muscular layer (detrusor muscle): 3 layers of smooth muscle 3.Fibrous adventia

Internal urethral sphincter: Smooth muscle Involuntary control More superiorly located External Urethral sphincter: Skeletal muscle Voluntary control Posteriorly located Sphincter Muscles on Bladder

When bladder fills with 200 ml of urine, stretch receptors transmit impulses to the CNS and produce a reflex contraction of the bladder (PNS) Diuresis (Micturition) When is incontinence normal?

Why do doctors ask for a urine sample? Urinalysis characteristics: smell- ammonia-like pH , ave 6.0 specific gravity– more than 1.0; ~ color- affected by what we eat: salty foods, vitamins

odor- normal is ammonia-like diabetes mellitus- smells fruity or acetone like due to elevated ketone levels diabetes insipidus- yucky asparagus--- Odor

pH- range ave 6.0 vegetarian diet- urine is alkaline protein rich and wheat diet- urine is acidic

Color- pigment is urochrome Yellow color due to metabolic breakdown of hemoglobin (by bile or bile pigments) Beets or rhubarb- might give a urine pink or smoky color Vitamins- vitamin C- bright yellow Infection- cloudy Color

Water: s.g. = 1g/liter; Urine: s.g. ~ to Pyelonephritus- urine has high s.g.; form kidney stones Diabetes insipidus- urine has low s.g.; drinks excessive water; injury or tumor in pituitary Specific Gravity

Glucose- when present in urine condition called glycosuria (nonpathological) [glucose not normally found in urine] Indicative of: Excessive carbohydrate intake Stress Diabetes mellitus Abnormal Constitutes of Urine

Albumin-abnormal in urine; it’s a very large molecule, too large to pass through glomerular membrane > abnormal increase in permeability of membrane Albuminuria- nonpathological conditions- excessive exertion, pregnancy, overabundant protein intake-- leads to physiologic albuminuria Pathological condition- kidney trauma due to blows, heavy metals, bacterial toxin Abnormal Constitutes of Urine

Ketone bodies- normal in urine but in small amts Ketonuria- find during starvation, using fat stores Ketonuria is couples w/a finding of glycosuria-- which is usually diagnosed as diabetes mellitus RBC-hematuria Hemoglobin- Hemoglobinuria- due to fragmentation or hemolysis of RBC; conditions: hemolytic anemia, transfusion reaction, burns or renal disease Abnormal Constitutes of Urine

Bile pigments- Bilirubinuria (bile pigment in urine)- liver pathology such as hepatitis or cirrhosis WBC- Pyuria- urinary tract infection; indicates inflammation of urinary tract Casts- hardened cell fragments, cylindrical, flushed out of urinary tract WBC casts- pyelonephritus RBC casts- glomerulonephritus Fatty casts- renal damage Abnormal Constitutes of Urine

INQUIRY 1.List several functions of the kidneys. 2.What does the glomerulus do? 3.What are several constitutes you should not find in urine? 4.What is specific gravity? 5.What two hormones effect fluid volume and sodium concentration in the urine? 6. Where are the pyramids located in the kidney? 7.What vessel directs blood into the glomerulus? 8.Where does most selective reabsorption occur in the nephron?

Moment of Zen KIDNEY