Excretory System (pg 378)

Maintain equilibrium by eliminating waste Lungs-CO2, H2O, heat (breath) Skin-H2O, salt, heat (sweat) Large intestines- indigestible materials (feces) Liver-toxins, heavy metals (urine) Kidneys- urea, uric acid (urine)

Urinary SystemMaintains water balance, ion balance and

eliminates metabolic wastes Metabolic wastes are byproducts of cellular

respiration that have been converted to toxins by the liver Ammonia (NH3) VERY TOXIC must convert to urea Urea (blood to kidneys) Uric acid (blood to kidneys)

Regulates the composition of blood

Principle StructuresRenal Artery/Renal VeinUreterUrinary BladderUrethraKidneysNephron

Renal Artery/Renal Vein

Renal Artery-Branches from the aorta to carry blood to kidneys to be cleaned

Renal Vein-Joins with inferior vena cava to carry cleaned blood back to heart

UreterTubes which carry urine from kidneys to

urinary bladderLined with cells that secrete mucus to

protect wallsOutside walls are smooth muscle for

peristalsis

Urinary BladderTemporary storage of urine by muscular

organ behind pubic bone Empty looks like a deflated balloon Full about the size of a pear

2 rings of muscle at junction Internal sphincter-involuntary External sphincter- voluntary

200-400ml max vol over 600ml control is lost

1.5 L empties in 24 hours

UrethraTube from bladder to exterior of body

Longer in males Shorter in females

Kidneys (pg 379)2 half kilogram fist sized on either side of

the spine on the back wall of the ab. cavityMay hold up to ¼ of body’s blood Filters waste from blood and produces

urine3 layers

Outer connective tissue-renal cortex Inner connective tissue-renal medulla Inner hollow chamber –renal pelvis

NephronFunctional part of the kidneyApprox 1 million slender tubules partly in

cortex and partly in medulla

Parts of the Nephron that carry blood

Renal ArteryAfferent arteriolesGlomerulusEfferent arteriolesPeritubular capillaries-wrap around the

kidney tubuleRenal vein

Parts that carry “urine”

Bowman’s capsuleProximal tubuleLoop of henleDistal tubuleCollecting ducts

Nephron Functional RegionsA FilterA TubuleA Duct

A FilterFiltration structure at top of each nephron

is Bowman’s capsuleRenal artery enters and splits into

glomerulusWalls of glomerulus act as a filter

impermeable to proteins, large molecules and red blood cells

Permeable to water, small molecules, ions and ureaFiltered fluid that leaves glomerulus and

enters Bowmans capsule is called filtrate

A TubuleBowman’s capsule connects to small long

narrow tube that is twisted back on itself to form a loop

This loop is a reabsorption device and has three sections: proximal (nearby) tubule, loop of Henle, distal (distant) tubule

Tubule absorbs substances that are useful to body (glucose, ions) from filtrate and secretes substances into surrounding tissue

A DuctTubule empties into larger channel called

the collecting ductCollecting duct reclaims water from filtrate Filtrate that remains in collecting duct is

now called urineSolids and water reclaimed during

reabsorption returned to body via renal veins

Formation of Urine1. Glomerular filtration

Movement of water and solutes from blood into nephron

2. Tubular reabsorption Transfer essential solutes from nephron back into

blood

3. Tubular secretion Transport of additional waste materials from blood

into nephron filtrate

4. Water reabsorption Removes water from filtrate and returns it to blood

Glomerular FiltrationProcess that forces waste from blood

plasma into Bowman’s capsuleFiltrate is identical to blood plasma minus

proteins and blood cells Plasma protein, blood cells, platelets are too large

to move through Water, sodium chloride, glucose, amino acids, H

ions, urea are small enough to move through

Tubular Reabsorption

Proximal TubuleMitochondria in walls use ATP for active

transport of nutrients (Na+, glucose, amino acids, K+) back into blood

Negatively charged ions (Cl-) tag along passively, attracted by electrical charge on transported ions

Water follows by osmosis

Tubular Reabsorption

Loop of HenleReabsorb water and ions from filtratePermeability of loop changes and water is

reabsorbed on the descending side and sodium ions reabsorbed on the ascending side

Tubular Reabsorption & Secretion

Distal Tubule (under control of hormones)Active reabsorption of sodium depends on

needs of bodyPassive reabsorption of negative ions like

chloride because of attractionDecreases concentration of filtrate so water

reabsorbed by osmosisPotassium and hydrogen (pH regulation) is

actively secreted back into nephronOther substances not normally part of body

also secreted

Water Reabsorption Collecting DuctFiltrate still contains lots of water Passive reabsorption of water from filtrate

by osmosisPermeability to water will depend on body

conditionsFiltrate is 4x more concentrated by the

time it leaves duct and is approx 1% of original filtrate volume now its called urine

Water regulation (osmoregulation)Blood pressure regulation

Maintaining the Excretory system

Water regulationDecrease of H2O in bloodMore H2O moves from cells to blood increasing the

osmotic pressureCells shrink Osmoreceptors located detect pressure change in

blood Triggers thirst and the release of ADHADH (antidiuretic hormone)moves to distal tubule

and collecting duct to make them more permeable to water which will increase reabsorption into blood

More water in blood means more water to the cells returning the osmotic pressure to normal

Negative feedback loop

Change in osmotic pressure

Cells shrink

Drinking

Release of ADH to encourage reabsorption

Blood Pressure Regulation

Blood volume influences blood pressureKidneys also play a role by adjusting blood volumeBlood pressure receptors near glomerulus called

detect low pressureRelease enzyme rennin which activates angiotensinAngiotensin constricts blood vessels and initiates

release of aldosterone produced in adrenal gland above kidney travels to kidney to act on distal tube and collecting duct to increase sodium transport which causes fluid level to increase

Increase fluid level means higher blood voluem therefore pressure change

Negative Feedback loop

Change in blood pressure

Renin initiates activation of Angiotensin

Constrict blood vessels

Release of Aldosterone

Increase in NaCl reabsorption and

Fluid level in body increases

Disorders of Urinary System

Diabetes mellitusDiabetes insipidusBright’s DiseaseKidney StonesGoutNephrosisToxemia