The Excretory System

By Leigh Berndsen, Harry Yao, and Josh Silver

The Urinary system

• It is made of two kidneys, Ureters, bladder, and Urethra.

• The Kidneys produce urine.• The urine passaess though the urerter into the

urinary bladder.• It is stored in the bladder, and excreted though

the urethra.• The kidneys remove watses from cellular

resperation and reglulate the blood concentrations

Kidneys

• Kidneys is located against the mussles of the back just below the diaphrgme, and are 10 cm long.

• Kidney is made of three parts, outer cortex, mudulla, pelvis.

• the blood is filleted in the cortex, the mudula is made of collecting ducts, and the pelvis is a cavity connected to the ureter.

• The collecting ducts carry the fillrate to the pelvis.

Nephrons• Fillisters the waste from the blood.• Each kidney has 1.25 million nephrons.• some nephrons are in the cortex, but the majority are in the

medulla.• Part of a nephron is a glomerulus, which is a group of capillaries.• Bowman’s capsule is a double walled surrounding of the

glomerulus.• The blood in the glomerulus is filleted into the Bowman’s

capsule.• The filtrate exits the Bowman's capsule though the renal tubule.• The center section of the renal tubule is the loop of henle, which

goes to the medulla• Slight reabsorption happens int eh loop of henle• Cortical nephrons have reduced loops of Henle and

jutamedullary nephrons have long loops which extend to the inner medulla.

Nephron 

 

Blood in the Kidneys• Blood enters through the renal arteries and exits through the

renal veins.• Nephrons have arteriole, which carry the blood from the renal

arteries to the nephron.• Prior to leaving the Bowman's capsule the capillaries join into an

arteriole.• The Bowman's capsule receves filtrate from the blood.• These arterioles subdivide into into a second capillary network

aroun the renal tubule.• Those caperlarses merge into a venule.• The golmerulus is a ball of capcapillieraies from the Bowman's

capsule.•  Afferent artiole is a renal artery that supplies blood to the

nephrons.•  Efferent artiole is when the capillaries converge and leave the

capsule.•  After the Efferent artiole, the network of capillaries subdivide into

the peritubular capillaries.

Renal tubules

• There are three main section to this tubule: Proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule.

• The fillterate is emptied into the collecting ducts from the renal tubules. 

Urine formation

• Formation of urine is in the nephrons during two processes.

• Filtration and reabsorption.• Filtration is a process of removing the wates

from the blood. Useful substances can be removed from the blood.

• Reabsorption is when the useful substances reenter the blood.

Filtration

• Filtration takes place in the glomeruli and Bowman’s capsules.

• The blood in the glomerulus is under pressure.• The pressure causes the filtrate which is water, urea,

glucose, amino acids, and salts though the permeable walls of the glomerulus into the Bowman's capsule.

• Blood cell and proteins are two big to pass though the walls of glomerulus

• Kidneys form around 180 liters of filtrate in a day• Only about 1-1.5 liters of urine are produced, this is

because if all the filtrate is excreted, the body will lose too much water.

Reabsorbtion

• Reabsorbtion occurs in the renal tubule.• Reabsorbtion reduceses volume of the filtrate, and resumite important

molecues into the blood.• When the filtrate goes though the renal tubes of the nephron, almost all

the water, guloces, amino acids and salts are reaborbted.• They enter though the caperallierys around the tubales.• The reabsorbtion of water is essentral to mammals, due to the fact of

Hemostasis.• While osmosis occures, guloce, amino acids, and salts use active tranport

and ATP is supplyed by the mytocondria in the renal tubuales. The tubuales have microvilli which increses the surface area in order to absorb.

Reabsorption 

• Kidney threshold level, is when the concentration is too high the is can not be absorbed.

• The excess substances that were not reabsorbed remains in the urine and is excreted from the body

• urine flows from the tubules to the collecting ducts. then the kidneys, then the ureters t the bladder, which is disposed of through the urethra

• Crystallization in the urine is called a kidney stone

Transport in the renal tubule

• proximal convoluted tubule (cortex):• plays a role in homeostasis by altering volume and

composition of filtrate through reaborbtion and secreation• regulates the pH throughout body fluids by secreating

hydrogen ions• nutrients such as glucose, amino acids, and potassium are

actively tranported into the interstitial fluid and then blood• microvilli on epithical cells compose the brush border allow

for reabsorbtion of nutrients such as NaCl and water • both active and passive transportation occur  • water enters the capillaries through osmosis becasue the

solution in hypotonic compared to the cell

Descending Limb of Loop of Henle

• Epithelium is permeable to water and not permeable to salt and other small solutes

• The interstitial fluid surrounding the tubule is hyperosmotic compared to the filtrate

• Water departs filtrate through osmosis (passive transport)

Ascending limp of loop of Henle

• epithelia relativley impermable to water• Thin segment:

o permeable to NaCl o NaCl diffuses out of tubule and into interstitial fluid via

passive transporto allows for high osmolarity in kidney

• Thick segment:o loses NaCl to interstitial fluid through active transport

without giving up watero filtrate is more diluted as it moves up cortex

Distal Convoluted Tubule

• It is a region of controlled reabsorption and secretion.• Contributes to pH regulation by quantitative secretion of H+

and reabsorption of bicarbonate (buffer in blood and intestitial fluid).

• It controls the K+ and Na+ homeostasis .• In order to control K+, it controls the the amount secreted

into the filtrate.• As for Na+, it does so though reabsorption.

Collecting Duct

• The collecting ducts carries the filtrate back in the direction of the medulla and renal pelvis.

• The epithelium of duct is permeable to H2O, not salt.• The filtrate becomes more concentrated because of the loss

of water though the process of osmosis (because of a hypertonic fluid outside the duct).

• Passive transport • The bottom of the duct epithelium is permeable to urea

(which will be explained in the next slide), thus using passive transport.

•  Due to the bodies need to keep homeostasis when a substance has a high concentration some of the urea diffuses from the duct

Nitrogenous wastes  

• Due to the metabolism of the body, nitrogenous wastes are formed.  They generally takes the form of ammonia (NH3) and are extremely toxic to the body therefore creating a need for the body to expel it.

• The human body does this though a detoxification process which results in a type of waste called Urea.  This is more efficient then just ammonia exreaction via water (which it is extremely soluble to) because it allows a conservation of water and therefore helps the human body to retain homeostasis.

• Kidney has high osmolarity 

Figue of the nephron.

Bibliogrpahy

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