The Human Body

Urinary System and Excretion

Urinary System

• Why do we have the urinary system? (four main)

1. Excretion of Metabolic Wastes– Excretion v. Defecation– Metabolic wastes (been part of the body

metabolites)– Urea, is a by-product of amino acid metabolism.

AA’s are broken down in the liver to produce ammonia which is combined with CO2 to form urea. Why not just leave the ammonia?

– Uric Acid produced from breakdown of nucleotides• Not solluble, if there is too much could crystalize = gout

Urinary System

2. Maintenance of Water-Salt Balance– Blood volume - salt

concentration• More salt, what happens

to blood volume?

• More salt what happens to blood pressure?

• How do kidneys regulate blood pressure?

– Ions controlled by kidney (NaCl, HCO3, Ca2+)

Urinary System

3. Maintenance of Acid-Base Balance– Blood pH should be

7.4• Acidic or Basic?

– H+ and HCO3- (which makes blood acidic which makes it basic)

4. Secretion of Hormones– Secretes renin which

signals the secretion of aldosterone (reabsorbtion of Na+)

– Erythropoietin to increase red blood cell production

Urinary System

• What are the organs of the urinary system? And what do they do?– Kidneys– Renal artery– Renal vein– Ureters– Urinary bladder– Urethra

Urinary System

• Kidneys– Either side of the vertebral

column– Protected by muscles and

the lower rib cage, but vulnerable (Relation to sports?)

• Renal artery– Enters the kidney

• Renal vein and Ureters– Exit the kidney

Kidney Structure

• Microscopically the kidney is constructed of over one million nephrons– Produce urine and are

positioned so that urine flows into a collecting duct

Kidney Structure

• Nephrons are the functional unit of the kidney– Each has own blood

supply– Two capillary regions

• Glomerulus and Peritubular capillary network

– Structures relate to functions

Kidney Structure

• Glomerular capsule (Bowman’s)– Filters blood via porous nature

• Proximal Convoluted tubule– Mitochondrial rich and high surface area for active transport of

filtrate components

• Loop of the Nephron– Descending limb for water to leave and ascending limb to

extrude NaCl

• Distal convoluted tubule– Tubular secretion

• Collecting ducts– Transport of urine

BloodComponents

Filtrate Reabsortion Urine Disease

Reed Blood Cells

- - - If there =

Hematuria

Proteins - - - If there = Proteinuria

Water + 99% 95% is water *

Urea + - + *Salts + + + the

excess*

Nutrients

(Eg. Glucose)+ + - If there =

Glucosuria

Drugs + - + *

Urine Components

Urine Formation

• How do we make urine? (book has a very good diagram)

1. Glomerular Filtration• Occurs when whole

blood enters the afferent arteriole and the glomerulus.

• Divides blood into filtrate and non-filtrate through pressure

Urine Formation

• Filtrate includes – Water, nitrogenous

wastes, nutrients and salts

– End up in the inside glomerular capsule

• Nonfilterate includes– Flormed elements

(cells and platelets)– Proteins

Urine Formation

• What could be the problem for the body if urine formation ended here and we disposed of the filtrate?

2. Tubular Reabsorption• Occurs as molecules and

ions are both passively and actively reabsorbed from the nephron into the blood of the peritubular capillary network.

Urine Formation

– Why is one thing reabsorbed and other thing not?• Osmotic Balance (Na+ goes Cl- follows)• Active transport and carrier molecules (there is a max though

and the rest goes to urine)

– Reabsorbed Filtrate• Most water• Nutrients• Required salts

– Nonreabsorbed Filtrate• Some water• Nitrogenous waste• Excess salts

Urine Formation

3. Tubular Secretion• Is a second way by

which substances are removed from blood and added to the tubular fluid.

• Hydrogen ions, creatine and drugs such as penicillin are moved by active transport from blood into the distal tubule

Kidney Structure

• Renal cortex– Outer granulated layer that

dips down in between a radially striated, or lined, inner layer

• Renal medulla– Cone-shaped tissue

masses called renal pyramids

• Renal pelvis– Central space, or cavity

Maintaining Water-Salt Balance

• What does Alcohol do?

• What does caffeine do?

• When do we use diuretics?

Urinary System

• Ureters– Extend from the

kidneys to the bladder– Small muscular tubes

25 cm long– Peristalsis moves

urine within the ureters and peristaltic contractions cause urine to enter the bladder

Urinary Illnesses• Kidney Stones

– Symptoms• Forms like a pearl. Blood in the urine (hematuria) • Increased frequency of urination • Nausea and vomiting • Pain during urination (stinging, burning) • Tenderness in the abdomen and kidney region • Urinary tract infection (fever, chills, loss of appetite)

– Treatment• Various medical treatments (break down, increase urine, etc.)• Tube and Basket• Electric shock breakup internal• Needle then catheter to remove manually• Open surgery

– Prevention• Lemonade (acid)• Very related to individual

Urinary System

• Urinary Bladder– Can hold up to 600 mL

of urine– Hollow, muscular

organ– Two sphincters

regulate loss of urine to the urethra

• What is a catheter?• Why are they used?

Urinary System

• Urethra– Extends from the urinary

bladder to an external opening

– Length varies from men (long) to women (short) Important why?

– In men the urethra is encircled by the prostate (problem in later life?)

– Connection of reproductive system and urinary system in men

Urinary Illnesses• Urinary Tract Infections

– Symptoms and Cause• Escherichia coli (E. coli) causes about 80% of UTIs in adults. These bacteria

are normally present in the colon and may enter the urethral opening from the skin around the anus and genitals. Women may be more susceptible to UTI because their urethral opening is near the source of bacteria (e.g., anus, vagina) and their urethra is shorter, providing bacteria easier access to the bladder.

• More common in women and triggered by sexual intercouse but for an unknown reason.

– For Lower• Back pain • Blood in the urine (hematuria) • Cloudy urine • Inability to urinate despite the urge • Fever • Frequent need to urinate • General discomfort (malaise) • Painful urination (dysuria)

Urinary Illnesses– For Upper

• Chills • High fever • Nausea • Pain below the ribs • Vomiting

– Treatment• UTIs are treated with antibacterial drugs. The type of drug used and the duration of

treatment depend on the type of bacteria. – Prevention

• Avoid products that may irritate the urethra (e.g., bubble bath, scented feminine products).

• Cleanse the genital area before sexual intercourse. • Change soiled diapers in infants and toddlers promptly. • Drink plenty of water to remove bacteria from the urinary tract. • Do not routinely resist the urge to urinate. • Take showers instead of baths. • Urinate after sexual intercourse. • Women and girls should wipe from front to back after voiding to prevent contaminating

the urethra with bacteria from the anal area.

Urinary Illnesses

Urinary Illnesses

• Renal Failure– Symptoms

• decreased urine output – decreased urine volume (oliguria) – no urine output (anuria)

• urination, excessive at night (can occur in some types of renal failure)

• ankle, feet, and leg swelling • generalized swelling, fluid retention • decrease in sensation, especially the hands or feet

– Treatment• Dialysis

– Prevention• Treating any causative disorders may help to prevent acute renal

failure. Many cases may not be preventable.

Urinary Illnesses

Urinary Illnesses

• Diabetes mellitus– What is it?

• Diabetes means that your blood glucose (often called blood sugar) is too high. Your blood always has some glucose in it because your body needs glucose for energy to keep you going. But too much glucose in the blood isn't good for your health.

– Symptoms• being very thirsty • urinating often • feeling very hungry or tired • losing weight without trying • having sores that heal slowly • having dry, itchy skin • losing the feeling in your feet or having tingling in your feet • having blurry eyesight

Urinary Illnesses

– Types• I – Juvenile (take insulin (pancreas) to offset a lack and

ensure sugar gets from food to systems)• II – Adult Onset (life style change)• Gestational Diabetes

– Treatment• Healthy eating, exercise, and losing weight • Insulin• Diabetes Pills (non-insulin)

– Prevention• Often none• Lifestyle changes