topic 7: urinary system Flashcards
list the main components of the urinary system
paired kidneys * paired ureters * the urinary bladder and * the urethra
where is the kidney located
- In dorsal lumbar area
- Between peritoneum and
dorsal abdominal muscles
(outside the peritoneal
cavity) - Right kidney is more cranial
than the left in most
domestic animals
tell me about the gross anatomy of the kidney
- Bean-shaped
structure in most
domestic animals - except in Cattle
(lobulated structures)
what are the different part of the kidney
Hilus: indented area in the
medial side
* At hilus, Ureters, nerves,
blood and lymph vessels
enter and leave kidney
* Renal Pelvis: funnel shaped area,
* Which forms the beginning
of the ureter
Renal cortex:outer portion of the
kidney
* Renal medulla: inner portion
around the renal
pelvis
Calyx (Calyces):cup-like structure
formed when renal
pelvis extends into
medulla pyramids
* Calyces act as
funnels to
direct/collect fluids
into renal pelvis
describe the general functions of each component of the urinary system
The kidneys produce urine by filtering the
blood
*
The urine produced will be transported via
the ureters to be stored in the bladder.
* It is finally excreted through the urethra
Basic functional unit of
kidneys
Nephron
what does the nephron consists of
- A renal corpuscle
- proximal convoluted tubule
(PCT) - loop of Henle (LOH)
- distal convoluted tubule (DCT)
what is the renal corpuscle made up of
Glomerulus (a cluster of
capillaries, tuft)
* Bowman’s capsule * Capsular space
what is the function of the renal corpuscle
- Function: filters blood in
first stage of urine
formation - Fluid filtered out of blood is
called glomerular filtrate
describe the blood supply of the kidney
- Renal artery enters
the kidney at the
Hilus
.Divides into smaller
arteries and even
smaller arterioles - Afferent glomerular arterioles
carry blood into the glomerular
capillaries of renal corpuscle - Glomerular capillaries filter some
of the plasma out of blood and put it
in the capsular space of Bowman’s
capsule - Efferent glomerular arterioles
receive blood from glomerular
capillaries - Efferent glomerular arterioles divide
further to form the peritubular capillaries
(small capillaries surrounding the
tubules), which allows following process
to happen at tubules - Oxygen supply to tubules
- Tubular reabsorption and
- Tubular secretion
Peritubular capillaries converge to form
larger veins, and finally the renal vein - The renal vein leaves the kidney at the
hilus and join the caudal vena cava
what part of the kidney is the proximal convoluted tubule, loop of henle and distal convoluted tubule located at
PCT: renal cortex
LOH: renal medulla
DCT: renal cortex
what are the two parts of the loop of henle
- descending from PCT
into medulla
(descending LOH) - Turning and heading
upward back into
cortex (ascending
LOH)
DCT of all the nephrons drain into what
collecting sucts
what are the three main steps of urine formation
glomerular filtration
(tubular) reabsorbtion
(tubular) secretion
describe the process of glomerular filtration
Glomerular capillaries contain many
large openings in capillary endothelium
*These openings are NOT large enough
to allow blood cells or large proteins to
pass through. substances bound to these protein are also retained (calcium, hormones)
* Blood enters the glomerulus, and due to the high pressure in the capillaries, any small molecules in plasma like water, ions (electrolytes), glucose, amino acids, drugs, and waste or toxic products such as urea are forced out of the capillaries and into the capuscular space in the of the Bowman’s capsule, forming the glomerular filtrate (primitive urine)
describe the process of reabsorption
Kidney tubules reabsorption
ensures the body gets back
the small useful molecules
from the filtrate
~65% of reabsorption takes
place in PCT, remaining in
DCT and LOH
* 80% of the water, sodium,
chloride, and bicarbonate,
and
* 100% of the glucose and
amino acids are reabsorbed
Sodium re-absorption
* Sodium ions are absorbed in PCT, LOH and
DCT
Ion re-absorption
Glucose and amino acid re-absorption
* Glucose and amino acids are absorbed in
PTC
Potassium and calcium re-absorption
* Take place mainly in the PCT
Chloride re-absorption
* Chloride diffuses through in response
to electrical imbalance created by (Na+)
removal (Chloride moves with sodium)
* Water is absorbed by following
osmosis (once sodium, glucose, amino
acids, and chloride have left the tubular
filtrate, water molecules follows)
describe the process of secretion
Secretion is the process by
which substances move into
tubules (urine) from blood
capillaries
Many substances, not
filtered from blood, are
eliminated by this process
* such as extra amount of
hydrogen, potassium,
ammonia, urea, certain drugs
and other wastes
* Occurs in PCT, LOH, DCT
how is urine volume regulated
Controlled by TWO hormones:
* ADH (antidiuretic hormone) from pituitary gland
* Aldosterone from adrenal cortex
* ADH acts on the DCT to promote water re- absorption (concentration)
* Aldosterone acts on the DCT to increases
reabsorption of sodium
* Causes osmotic imbalance that encourages water to
follow sodium into blood (concentration)
how does the body maintain water balance
Water is reabsorbed in the Proximal
convoluted tubules and the Loops of henle.
* Fine adjustments are made at the Distal
convoluted tubule and collecting duct under
the influence of Antidiuretic hormone (ADH)
(from Pituitary gland
how does the body maintain salt balance
In the Distal convoluted tubule and
collecting duct.
* Aldosterone (from adrenal gland) can
increase the reabsorption of Na+
back to the extracellular fluid, and K+
secretion.
what are the functions of kidneys
- Water balance
- Acid-base balance (H+, HCO3-)
- Electrolyte balance
- Hormone production (Erythropoietin, Calcitriol,
renin), Hormone removal (Gastrin) - Activation of Vitamin D3
how does osmoregulation of the blood occur
Renin: a hormone secreted in glomerulus in
response to low arterial pressure
* converting angiotensinogen (serum protein produced
in liver) to angiotensin.
* Angiotensin –causes vasoconstriction and
stimulates the release of aldosterone (from
adrenal cortex of kidney)
what are the different layers of the ureters
- Outer fibrous layer, middle smooth
muscle layer, and inner layer lined with
transitional epithelium - Transitional epithelium allows ureters to
stretch as urine passes through - Middle smooth muscle layer propels
urine through the ureters by peristaltic
contractions
Based on the structure of ureters, explain why urine cannot backflow from the bladder to ureters.
Ureters * Enter urinary
bladder at an
oblique angle
* Thus forming a
functional valve to
prevent backflow
into ureter
* When the bladder is
full, urine presses
the entrance to
close it
what are the different layers of the urinary bladder
Also Lined with transitional
epithelium that stretches as the
bladder is filled with urine
*The wall of the urinary bladder
contains smooth muscle
*Around the neck of the urinary
bladder are circular muscles
(sphincter muscles)
*Internal sphincter:
smooth muscle under
involuntary control
*External sphincter:
skeletal muscle under
voluntary control * Allow voluntary control of
urination
function and layer of urethra
function: Continuation of the neck of the urinary
bladder
* Carries urine from the bladder to the
external environment
Lined with transitional epithelium
which allows it to expand
Compare the female urethra to the male urethra.
length and function
*The female urethra is shorter and
straighter
* Compared to the long, curved urethra
in male
*In the female the urethra only serve as
urinary function
*In the male the urethra runs down the
centre of the penis and also functions
to carry semen
Explain how urination process is controlled
- Urination is the excretion of urine
from the urinary bladder into the
urethra - Building up of pressure in bladder
activates stretch receptors
(pressure sensor) in bladder wall - Which activate a spinal reflex that
cause bladder smoother muscles
to contract - Contraction gives the sensation of
having to urinate
Voluntary control of the external
sphincter around the neck of the bladder
allow the temporary control of urination - House-trained animals can exercise
voluntary control of the external sphincter
muscle to temporarily hold the urine - However, beyond a certain pressure limit,
the sphincter eventually relaxes to
release the urine.
