Ohhh,$it’s$on$alright….$!  9"classes"of"Biology"12"left!!!"

"  Urinary"system"

"  Reproductive"system"

!MONDAY!JUNE!15!-!BIOLOGY!12!FINAL!!

12:00-2:00pm!!

! view"KhanAcademy’s"“The"

Kidney"&"Nephron”"over"the"

weekend"

!  http://www.khanacademy.org/video/theI

kidneyIandInephron?playlist=Biology""

THE$URINARY$SYSTEM$Excretion$

!  The"removal"of"nitrogenIcontaining"waste"

products"of"metabolism"and"any"excess"

substances"due"to"cell"metabolism"

"  E.g."Urea"

The$Urinary$System$ Organs$of$the$Urinary$System$!  Kidneys"

"  main"excretory"organ,"helps"maintain"

homeostasis"through"regulation"of"H2O"and"

ions"

Organs$of$the$Urinary$System$!  Kidneys"

"  main"excretory"organ,"helps"maintain"

homeostasis"through"regulation"of"H2O"and"

ions"

!  Ureters""  Transports"urine"from"kidney"to"bladder"

"  Conveys"urine"by"peristalsis"

Cont’d$!  Urinary"Bladder"

"  Stores"urine""  Expandable""  2"sphincters"to"control"release"of"urine"into"the"urethra"

"

Cont’d$!  Urinary"Bladder"

"  Stores"urine""  Expandable""  2"sphincters"to"control"release"of"urine"into"the"urethra"

!  Urethra""  Small""tube"from"bladder"to"external"opening"

"  In"males,"also"transports"semen""

"

Kidney$Function$1.  Produce"urine"

2.  Maintain"H2O"/"salt"balance,"adjust"blood"

tonicity""

"  more"salts"in"blood"causes"osmosis"which"

increases"blood"volume"and"BP"

Kidney$Function$3.  Regulate"concentrations"of"ECF"

(extracellular"fluid)"ions"

"  Na+,"K

+,"Cl

I,"H

+",Ca

+2,"HCO

3

I,"Mg"

+2,"SO

4

I,"PO

4

I3"

4.  Maintains"blood"pH"by"regulating"levels"of"H

+"and"HCO

3

I"

a)  If"blood"is"acidic,"H+"is"excreted"and"HCO

3

I"is"

reabsorbed"

b)  If"blood"is"basic,"H+"is"not"excreted"and"HCO

3

I"is"

not"reabsorbed"

"

Kidney$Function$(cont’d)$5.  Maintains"blood"plasma"volume"�"regulates"

arteriole"BP"

6.  Filter"blood"by"excretion"of"nitrogenous"wastes"

(urea,"uric"acid,"creatinine)"

"  Urea"–"breakdown"of"AA"creates"NH3""(in!the!liver) "

"NH3""+"""CO

2"�"urea"(less"toxic"than"NH

3)"

"  Uric!acid"="breakdown"of"nucleotides"(can"form"

crystals)"

"  Creatinine="breakdown"of"creatine"phosphate"–"

synthesized"by"AA"in"liver"�high"energy"reserve"

molecule""for"muscles"(like"ATP)"

"

Cont’d$7.  Secretes hormones (assist the endocrine

system) a.  erythropoietin → stimulates RBC production b.  renin →releases Aldosterone when BP is low

for reabsorbing Na+ 8.  Excretes foreign substances i.e.) drugs,

food additives, pesticides!

Kidney$Structure$!  Two bean shaped organs lying at the back

of the abdominal cavity •  Composed of 3 main parts:!1. Renal cortex = outer region (red because

many capillaries)!2. Renal medulla = inner area (striped

because of tubules and blood vessels)!

Kidney$Structure$!  Two bean shaped organs lying at the back of

the abdominal cavity •  Composed of 3 main parts:!1. Renal cortex = outer region (red because

many capillaries)!2. Renal medulla = inner area (striped because

of tubules and blood vessels)!3. Renal pelvis = innermost portion where urine

collects before leaving kidney!

Cont’d$!  Made up of about 1 million tiny NEPHRONS

"  A nephron is composed of a system of tubules"

Anatomy$of$a$Nephron$!  Each"nephron"has"its"own"blood!supply!

"  From"renal!artery!(high"O2,"glucose,"AA,"wastes),"

afferent!arteriole"leads"into"the"glomerulus!

Renal$Cortex$&$Medulla$

Anatomy$of$a$Nephron$!  Each"nephron"has"its"own"blood"supply"

"  From"renal!artery!(high"O2,"glucose,"AA,"wastes),"

afferent!arteriole"leads"into"the"glomerulus!

"  Blood"leaves"the"glomerulus"via"an"efferent!arteriole!"(narrower"in"size)!

Anatomy$of$a$Nephron$"  Efferent"arteriole"takes"blood"to"peritubular!capillary!network!(PCN)!

! These"surround"rest"of"the"nephron""

Anatomy$of$a$Nephron$"  Efferent"arteriole"takes"blood"to"peritubular!capillary!network!(PCN)!

! These"surround"rest"of"the"nephron"! Blood"then"goes"to"renal"venule"→ renal

vein → vena cava !  High in CO2, glucose, AA

!  Low in wastes & O2"

Parts$of$a$Nephron$!  Bowman�s"capsule"

"  Cuplike"structure"

"  Surrounds"glomerulus"

Parts$of$a$Nephron$!  Proximal"convoluted"tubule"(PCT)"

"  Cuboidal"epithelial"cells"with"microvilli"

!  Increased"surface"area"for"absorption"

Cont’d$–$parts$of$a$nephron$!  Loop"of"Henle"(or"loop"of"nephron)"

"  UIshaped"tube"

"  Dips"into"renal"medulla"

Cont’d$–$parts$of$a$nephron$!  Distal"Convoluted"tubule"(DCT)"

"  Lack"microvilli"

"  Designed"for"tubular"excretion"rather"than"

reabsorption"

"

Cont’d$–$parts$of$a$nephron$!  Collecting"Ducts"

"  Transports"urine"through"medulla"&"delivers"it"to"

renal"pelvis"

"  Usually"impermeable"to"water"but"ADH"increases"its"

permeability"