The Excretory System

Excretion- removal of waste produced during body functions Occurs through: 1.Intestine- digestive wastes, salts 2.Skin (sweat glands)- water, electrolytes 3.Lungs- carbon dioxide, water 4.Kidneys- toxins, water, N cmpds, electrolytes

Urinary System Functions A.maintain water concentration in blood B.maintain concentration of ions like Na & K C.form urine D.influence rate of secretion of hormones like ADH E.alter pH (acid- base balance) Why bother with all of these?

Basic Anatomy of the Urinary System

Gross Anatomy- KIDNEY 1.lie in retroperitoneal position 2.Fat cushion holds it in position 3.medial surface with concave hilus Not that type….

Gross Anatomy- KIDNEY 4.Cortex- outer and lighter 5.Medulla- inner and darker 1. Cortex region of kidney 2. Medulla region of kidney

Gross Anatomy- KIDNEY 6. Most of the medulla is made up of RENAL PYRAMIDS with a base facing outward and papilla facing the hilus

Gross Anatomy- KIDNEY 7. Cortical tissue dips into the medulla between the pyramids, forming RENAL COLUMNS

Gross Anatomy- KIDNEY 8. Each renal papilla juts into a cup-like CALYX –Urine leaving the renal papilla collects here before leaving the body

Gross Anatomy- KIDNEY 9. The calyces join to form the renal pelvis. It narrows as it exits the hilum to become the ureter.

10. BLOOD VESSELS Renal artery brings ¼ of all blood to kidney/min. Branches into Interlobar arteries- extend toward the cortex Changes names Arcuate arteries- base of pyramids Changes names Interlobular arteries- afferent arterioles that branch into the glomerulus where blood is filtered

10. BLOOD VESSELS (continued) Efferent arterioles Peritubular capillaries (vasa recta)  Interlobular vein  Arcuate vein  Interlobar vein  renal vein Blood flows into But, I am not going to test you on this stuff!

Macroscopic Kidneys A. Capsule & hilus B. Renal sinus 1. renal pelvis 2. major calyces 3. minor calyces C. Renal medulla 1. renal pyramids a. papilla 2. Renal column D. Renal cortex

B. Gross Anatomy- URETER 1.28 cm long 2.Allows urine to travel from kidney to urinary bladder 3.3 layers of tissue: –Mucous lining –Smooth muscle middle –DWF outer layer

C. URINARY BLADDER 1.behind symphysis pubis 2.mostly smooth muscle aka detrusor muscle lined with transitional epithelium 3.3 openings: 2 from ureters and one into the urethra 4.Has valve to prevent backflow into kidney 5.Functions –urine reservoir –aided by urethra, expels urine from body

Male Urethra Female Urethra

Gross Anatomy- URETHRA 1.3 cm in females; 20 cm in males 2.Male urethra (URINE) passes through prostate gland where it is joined by 2 ejacuatory ducts (SEMEN) then travels through penis and ends at the urinary meatus at the tip of the penis. 3.In females, completely separate from vagina

4. Micturition- urination 1.Voluntary relaxation of external sphincter muscle of bladder 2.Detrusor muscle contracts 3.Parasympathetic nerve control 4.Incontinence

Microscopic Structure of the NEPHRON Filtering unit of kidney Process blood plasma Form urine 1.25 million per kidney Looks like a funnel with a long, winding stem

NEPHRON Components 1. renal corpuscle 2. PCT 3. loop of Henle 4. DCT 5. Collecting tubule & duct

The Nephron The nephron is the functional unit of the kidney, responsible for the actual purification and filtration of the blood. About one million nephrons are in the cortex of each kidney.

The NEPHRON RENAL CORPUSCLE- in the cortex 1.Bowman’s capsule Cup-shaped mouth of nephron 2.Glomerulus capillaries in BC Pores (fenestrations) Basement membrane

The Glomerulus

Microscopic Structure of the NEPHRON PROXIMAL TUBULE- in cortex –Closest to BC (“proximal”) –Aka PCT (proximal convoluted tubule) –Brush border (microvilli) face lumen- increase surface area

The NEPHRON LOOP OF HENLE (LOH) Renal tubule beyond the PCT –Descending limb (thin) –Sharp turn –Ascending limb (thick) –Dips into medulla cortex medulla

THE NEPHRON DISTAL TUBULE Aka DCT (distal convoluted tubule) Beyond LOH (“distal”) Juxtaglomerular apparatus

THE NEPHRON COLLECTING DUCT –Straight tubule joined by distal tubules of several nephrons –Fuse to form papillary ducts which deliver urine to the calyces

Overview of KIDNEY FUNCTION 1. FILTRATION –Occurs in glomerulus –Dependent on Glomerular Filtration Rate (GFR) –Filter water and solutes from blood into renal tubule Glucose Amino acids Nitrogen wastes

KIDNEY FUNCTION-Filtration FILTRATION –What’s left in the blood? Blood cells Most plasma proteins –What causes it? Pressure gradient (high to low) Related to blood pressure

Filtration GFR is directly dependent on blood pressure. a. If GFR (BP) is too high, filtrate flows too fast and substances are NOT reabsorbed urine flow increases  water is lost  blood volume drops  blood pressure drops. b. If GFR (BP) is too low, filtrate flows too slow and substancesare retained too much urine flow decreases  water is preserved  blood volume increases  blood pressure increases.

Overview of KIDNEY FUNCTION 2. REABSORPTION –Occurs in mostly in PCT and little in LOH, DCT, CD –Put good things in the renal tubule back into the blood (peritubular capillaries) Water Electrolytes Nutrients

Overview of KIDNEY FUNCTION REABSORPTION –Healthy kidneys reabsorb Glucose (if not…) Amino acids Sodium Water

Overview of KIDNEY FUNCTION REABSORPTION –Substances that are NOT reabsorbed fully Things that lack carriers Things that are not lipid soluble Things that are too large Examples: urea, creatinine, uric acid

Overview of KIDNEY FUNCTION REABSORPTION –ADH causes the distal and collecting tubules to become more permeable to water –This allows hypertonic urine to be formed

Overview of KIDNEY FUNCTION SECRETION –PCT mostly –Reabsorption in reverse –Movement of small molecules out of the peritubular blood and into the tubule for excretion Including K, H, urea, ammonia Dispose certain drugs Helps control blood pH

Review Questions Do you know the names of the structures? What is GFR? What regulates it? Why is reabsorption important? Where is the only place glucose is reabsorbed? Where does ADH act? What does it do?

Making Urine Choose your water solution (Normal or Dehydrated) Fill the cup 2/3 of the way with that solution Add ½ dropper of Urea + vitamins Add ½ dropper of acid Check pH with pH paper If you desire, pimp your urine with 1 dropper of the following: Condition/ Substance Diabetes Urinary Tract Infect Kidney Failure Glucose+-+ Blood-++ Protein--+

Answer the following questions on a piece of paper and turn it in? 1.Did you drink the urine? 2.What type did you make? 3.How did it taste? 4.Did it taste like you expected? 5.If you did not drink it, why not? (please provide at least three reasons)

URINE COMPOSITION Water- 95% Other substances- 5% –Nitrogen wastes –Electrolytes –Toxins –Pigments –Hormones –Abnormal stuff like blood, glucose, casts, calculi

URINE COMPOSITION Characteristics –Color –Compounds –Slight odor – pH (fresh is acidic) – specific gravity

FLUID, ELECTROLYTE, and ACID-BASE BALANCE FLUID –Water accounts for 50-60% total weight (why less in obese people?) 37% of this is ECF 63% of this is ICF

FLUID, ELECTROLYTE, and ACID-BASE BALANCE Mechanisms to maintain fluid balance –Volumes of ICP, ECF, plasma, and total volume of water relatively constant –Adjust output (urine volume) to intake –Adjust fluid intake (liquids we drink, water in food we eat, water formed by catabolism)

Anatomy of Micturition & Incontinence Detrusor muscle with an External and Internal sphincter Normal capacity cc First urge to void cc CNS control –Pons - facilitates –Cerebral cortex - inhibits Harmonal effects - estrogen

Bladder Pressure-Volume Relationship: Or how to hold it

Treatment Options Reduce amount and timing of fluid intake Avoid bladder stimulants (caffeine) Use diuretics judiciously (not before bed) Reduce physical barriers to toilet (use bedside commode) 1

Pessaries

Predisposing conditions to UTI Female Short urethra, proximity to anus, termination beneath labia Sexual activity Pregnancy –2-3% have UTI in preg, % with asx bacteriuria decreased ureteral peristalsis, temp. incomp ofvesicoureteral valves

Urethritis Acute dysuria, frequency Often need to suspect sexually transmitted pathogens esp. if sx more than 2 days, no hematuria, no suprapubic pain, new sexual partner, cervicitis

Cystitis Sx: frequency, dysuria, urgency, suprapubic pain Cloudy, malodorous urine (nonspec.) Leukocyte esterase positive = pyuria Nitrite positive (but not always) WBC (2-5 with sx) and bacteria on urine microscopy

Nephrolithiasis: kidney stones Supersat. of urine by stone forming constituents Freq. stone types: Calcium (most common), struvite, oxalate, uric acid Risk factors: metabolic disturbances, previous UTI, gout, genetic Incidence = 2-3% Hematuria (rarely dangerous by itself) Dangerous combo = obstruction + infection

Addison’s Disease Addison's disease occurs when the adrenal glands do not produce enough of the hormone cortisol and, in some cases, the hormone aldosterone

Cystocele mild—grade 1—when the bladder droops only a short way into the vagina. severe—grade 2—the bladder sinks far enough to reach the opening of the vagina. advanced—grade 3—cystocele occurs when the bladder bulges out through the opening of the vagina. the wall between a woman’s bladder and her vagina weakens and allows the bladder to droop into the vagina

Nocturnal enuresis Hormonal problems. Bladder problems. Genetics. Sleep problems. Medical conditions Psychological problems.