Download Renal Artery

Unit O: Urinary System
I. Function Of Organs:
Aorta: Brings blood to the renal
artery
Renal Artery: supplies blood to the
kidney to be “cleaned”.
Kidney: Organ that filters the
blood’s toxins and wastes,
transferring them to urine.
Ureters: Tubes that transfer the
urine to the bladder
Bladder: storage of urine. Contain
stretch receptors.
Urethra: Transfers urine from
bladder to the outside of the body.
Structure of Kidney
• Kidney organized into
three layers:
1. Renal cortex: outer
layer
2. Renal medulla: middle
area of kidney
3. Renal pelvis: inner area
of kidney where urine
collects.
II. Urinary System Removes
Metabolic Wastes:
• The functions of the urinary system are
many: the kidneys remove toxins and
wastes from the blood:
H+ ions
Urea
Water soluble vitamins
Histamines
Penicillin and other drugs
Salts: K+, Na+, HCO3-, if excess present.
III. Functional Unit of Kidney: The
Nephron: Label your diagram:
Parts of the Nephron:
1. Afferent arteriole: brings blood into the glomerulus for
pressure filtration.
2. Glomerulus: A special capillary where pressure filtration
takes place.
3. Efferent arteriole: take blood to the peritubular capillary
network.
4.Bowman’s Capsule (Glomerular capsule) Catches the fluids
removed from blood with pressure filtration.
5. Proximal convoluted tubule: The location of selective
reabsorption., where nutrients are returned to the blood.
6. Loop of Henle: Allows water to leave and reabsorb into
blood.
7. Distal convoluted tubule: Where Tubular secretion occurs.
8. Collecting Duct: Urine collects here at end of tube and is
passed to the renal pelvis of Kidney.
Animation:
IV. Urine Formation
•This process is complex. We divide it into several
stages, each occurring at different parts of the nephron.
• i) Pressure Filtration: This
occurs at the glomerulus. The high
blood pressure pushes the liquid
portion of blood out of the capillary
(glomerulus) and into the
Bowman’s capsule. This
liquid,called filtrate, contains all the
small molecules present in the
blood:
Nutrients:
Wastes.
Glucose
Fatty acids
Amino Acids
Urea
H+
Drugs
ii) Selective Reabsorption:
• Occurs at the Proximal
Convoluted Tubule (PCT)
• The “Good Stuff” that
was removed during
pressure filtration is
returned by active
transport to blood:
nutrients (glucose etc.) ,
some salts (Na+, Cl- )
and H2O.
• The cells of the PCT
contain many
mitochondria for ATP
production, and active
transport.
iii) Water Reabsorption: Loop of Henle
• The filtrate goes down
the descending loop of
Henle, water is drawn
out due to increasing
saltiness in the renal
medulla, moves by
osmosis into the blood.
• The filtrate becomes
more concentrated as
water leaves.
iv) Salt Balance
• The ascending loop of Henle moves Na+ out of the
filtrate, initially by diffusion, then by active transport.
This causes the medulla of kidney to be very salty.
Chloride ions follow sodium.
• The ascending loop is impermeable to water,
therefore filtrate remains concentrated.
• As filtrate reaches the cortex, most of the Na+ has
been removed by active transport and the filtrate is
isotonic with the extracellular fluid at the distal
convoluted tubule.
• The water that left the filtrate in the loop of Henle
diffuses by osmosis back into the blood at the
peritubular capillaries.
v) Tubular Secretion:
• At the distal convoluted tubule
(DCT) last minute adjustments
are made.
• Penicillin, histamines, vitamins
that are in excess in blood are
added to filtrate by active
transport (called secretion).
• Potassium and sodium
concentrations are similarly
adjusted.
• pH is balanced by secreting
excess H+ ions if blood is acidic,
or secreting HCO3- if blood is too
basic (high pH). Reabsorption of
H+ ions from filtrate to blood
also occurs here if pH of blood
is too high.
Tubule
Blood
vi) Collecting Duct:
• The urine is collected here and last minute
adjustments are made according to the
concentration.
• Water can be reabsorbed (added to blood) or
secreted under the action of antidiuretic
hormone (ADH)
• Urine from millions of collecting ducts
transfers to the renal pelvis and eventually to
the ureters.
V) Hormones: ADH
• Hypothalamus detects low blood volume (and low
pressure) and makes Antidiuretic Hormone (ADH),
also known as vassopressin, which is stored in the
posterior pituitary gland.
• Pituitary releases ADH into blood supply.
• ADH binds to receptors on the collecting duct’s cells,
causing more water pores (aquaporin) to be made in
cell membranes of duct.
• Results in more water reabsorbed into the blood and
blood volume increases.
• When blood volume increases -so does pressure.
Higher pressure shuts down ADH production.
With ADH secreted:
Water leaves
filtrate and
enters the
blood.
Urine is
more
concentrated.
Without ADH:
Less water
is reabsorbed
at collecting
duct.
Urine is more
dilute.
VI) Hormones:
Aldosterone
• Low blood pressure, detected at the
juxtaglomerular apparatus, initiates a series of
complex hormone interactions.
• Results in a steroid hormone: aldosterone:
made in adrenal gland
(cortex region) to be
released.
Aldosterone action:
• Targets the cells of the distal convoluted
tubule resulting in more Na+ reabsorption
(and K+ excretion) with Na+/K+ pump.
• Results in blood plasma being more salty,
therefore water is also reabsorbed by
osmosis and blood volume goes up.
VII) Substances Affecting
Urine Formation:
• Diuretics: A substance that increases urine
flow. Eg. Alcohol which inhibits ADH
synthesis therefore urine is dilute. (A
hangover is dehydration brought on by too
much urination combined with the need for
H2O for alcohol metabolism).
• Diabetes: excess glucose is secreted in the
urine of diabetics. The glucose also causes
more H2O to be excreted so urine flow is
frequent and high in hyperglycemia.