Urinary System Ch 25

Function Remove nitrogenous wastes Maintain electrolyte, acid-base, and fluid balance of blood Homeostatic organ Acts as blood filter 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 178-179 liters are reabsorbed back into blood Excrete a protein free filtrate

Renal Artery Segmental Arteries Interlobar Arteries Arcuate Arteries Cortical Radiate Arteries Afferent Arterioles Glomerular Capillaries Efferent Arterioles Peritubular Capillaries Cortical Radiate Vein Arcuate Veins Interlobar Veins Renal Veins

Nephron consist of a long tubule & a ball of capillaries called a glomerulus the end of the tubule that surrounds the glomerulus is called Bowman’s capsule the remaining parts of the tubule are called the: proximal tubule loop of Henle distal tubule the tubule empties into a collecting duct that leads to the renal pelvis the renal pelvis opens to the ureter

Nephron Each kidney contains over 1 million nephrons and thousands of collecting ducts

Nephron’s functions: glomerular filtration tubular reabsorption 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

Boman’s Capsule filtration occurs as blood pressure in the capillaries of the glomerulus forces filtrate into Bowman’s capsule the process is passive (diffusion) the filtrate includes: water, salts, bicarbonate (HCO3–), H+, urea, glucose, amino acids

Proximal Convoluted Tubule Reabsorbs: water, glucose, amino acids, and sodium. 65% of Na+ is reabsorbed 65% of H2O is reabsorbed 90% of filtered bicarbonate (HCO3-) 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

Loop of Henle: Descending Limb is impermeable to salts but permeable to water as filtrate moves through the descending limb, water steadily moves out making the filtrate more & more concentrated this occurs because the osmolarity (salt concentration) of the interstitial fluid in the renal medulla becomes increasingly greater the further down you go 20

Loop of Henle: Ascending Limb is permeable to salts but impermeable to water as filtrate moves through the ascending limb, NaCl moves out making the filtrate more & more dilute basically, the purpose of the loop of Henle is to keep the renal medulla region of the kidney at a high osmolarity so water can move passively out of the filtrate in the collecting duct (as we’ll see shortly) 21

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

ADH Antidiuretic hormone: Produced by posterior pituitary Targets collecting ducts to be more permeable to water Results in more concentrated urine

Collecting Duct Allows for the osmotic reabsorption of water. the collecting duct carries the remaining filtrate back through the renal medulla which is now very high in salt (high osmolarity) as the filtrate passes through the collecting duct, water can passively move out how much water moves out depends on the amount of water needed by the body this is controlled by the hormone ADH

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

Nitrogenous Wastes Proteins Amino acids COOH -NH2 Ammonia Urea Uric Acid

Hormonal Control of Kidney Function ADH ANP Renin-Aldosterone-Angiotensin

Fig. 18.09 ADH

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

ANP aldosterone

Regulation of Aldosterone secretion by renin-angiotensin-aldosterone (RAA) pathway Fig. 18.16

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

Hormonal Control of Kidney Function angiotensinogen angiotensin I renin angiotensin II

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

Urinary Bladder ureters urethra internal sphincters external sphincters

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

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

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

Urinalysis Why do doctors ask for a urine sample? characteristics: smell- ammonia-like pH- 4.5-8, ave 6.0 specific gravity– more than 1.0; ~1.001-1.003 color- affected by what we eat: salty foods, vitamins

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

pH- range 4.5-8 ave 6.0 vegetarian diet- urine is alkaline protein rich and wheat diet- urine is acidic

Color 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

Specific Gravity Water: s.g. = 1g/liter; Urine: s.g. ~ 1.001 to 1.030 When urine has high s.g.; form kidney stones Diabetes insipidus- urine has low s.g.; drinks excessive water; injury or tumor in pituitary

Normal Constitutes of Urine

Normal Constitutes of Urine

Abnormal Constitutes of Urine  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

Abnormal Constitutes of Urine 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- not normal in urine 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

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

Moment of Zen KIDNEY

Moment of Zen