The urinary system
Structure:
2 kidneys
2 ureters
1 bladder
1 urethra
Functions:
Forms urine to excrete waste
Regulates blood volume
Regulates electrolytes
Regulates acid-base balance
In other words, the process of urine formation helps
maintain the normal composition, volume, and pH of both
blood and body fluids by removing wastes and excess
substances
http://www.healthtoolsonline.com/flash-img/urology.swf
IVP - Intravenous
Pyelogram
Three Processes Occur
Filtration
Reabsorption
Secretion
Functionally, cortical and juxtamedullary nephrons have distinct roles. Cortical nephrons (85%
of all nephrons in humans) mainly perform excretory and regulatory functions, while
juxtamedullary nephrons (15% of nephrons in humans) concentrate and dilute urine
Why the difference in cortical and juxtamedullary nephrons?
In the descending limb (of the loop), water moves freely but
salt cannot. Longer descending limbs make the filtrate more
hypertonic than shorter limbs
In the ascending loop, salt is actively pumped out (no water
exchanges) which makes the filtrate hypotonic
http://www.youtube.com/watch?v=SoilI_J0Vq0&f
eature=related shows the medulla and cortex
and explains pyramids, calyces. 1.4 min
http://www.youtube.com/watch?v=8TXXIJGz4F4&feat
ure=related diagram and explanation of nephron,
show cortex, medulla, and the two types of nephrons,
collecting ducts 1.35 min
http://www.youtube.com/watch?v=6Wc4f2KnbYo&featu
re=related shows kidney cortex, medulla, nephron
function, chemistry, urine formation 8.5 min
http://faculty.southwest.tn.edu/rburkett/A&P2%20urinary_system
.htm nice site with lots of pictures including scanning electron
micrographs
http://video.google.com/videosearch?q=cystoscopy&site
search=# shows cystoscopy and biopsies. 4 min - watch
1 min then go to about 3.5 for bx
150-180 liters
filtered
99% reabsorped 1% becomes urine
Oh No! Not Hormones Again!!!
ADH - Antidiuretic Hormone increases reabsorption of water from
filtrate back to blood
PTH - Parathyroid Hormone increases reabsorption of calcium from
filtrate back to blood and excretes phosphate into filtrate
Aldosterone increases reabsorption of sodium from filtrate back to blood
and excretion of patassium into filtrate. Water follows sodium.
ANP - Atrial Natriuretic Peptide decreases reabsorption of sodium,
which remains in the filtrate. More sodium & water are eliminated in
urine
(Table 18-1, page 428 and Fig 18-5, page 429, Scanlon text)
Other Kidney Functions:
Secretion of renin
Production of erythropoietin
Activation of vitamin D
When BP goes down, kidneys secrete renin and BP goes up
The small print:
Renin converts angiotensin (from lungs and blood vessels) to angiotensin II. Angiotensin II
causes blood vessels to constrict and stimulates aldosterone (from adrenal glands)
Other Kidney Functions:
Secretion of renin
Production of
erythropoietin
Activation of vitamin D
When blood oxygen goes down, kidneys produce
erythropoietin and RBC production goes up
The small print:
Erythropoietin causes bone marrow to produce more red blood cells which can carry more
oxygen
Other Kidney Functions:
Secretion of renin
Production of erythropoietin
Activation of vitamin D
The kidneys activate vitamin D which increases absorption of
calcium and phosphate
The small print:
Vitamin D is converted to an active form called calcitriol (D2) which causes the small
intestines to take up more calcium from our food
Finally, elimination!
(sometimes called the home stretch)
Rugae
Detrusor muscles
Internal and external
sphincters
Page 432 of
Scanlon text
urination
Urination is a spinal cord reflex over which voluntary control
may be exerted
The bladder stretches as it fills.
The detrusor muscles are sensitive to the stretching
At about 300 ml, a message is sent to the spinal cord
A parasympathetic nerve impulse is sent back to the
detrusor muscles to contract *
* remember
The internal urethral sphincter relaxes
parasympathetic
nerve pathways?
If urination is desired or required, the external urethral
sphincter is voluntarily relaxed and the bladder empties
So what is this stuff called urine?
Review and Study Guide
Be able to spell and define terms related to the
urinary system
Be able to label a diagram/picture of the kidney, the
nephron, the urinary system, and the bladder as
shown on these PPT slides
Be able to clearly answer review questions on page
437 of your Scanlon text, specifically numbers 1, 3,
4, 7, 11, 12, 13, 14, 15
Be able to fully explain filtration, reabsorption and
secretion
Be able to discuss 4 mechanisms of tubular
reabsorption (425 & 427)
Let’s Review
1. name the three tubes that make up the urinary system
2. where are the kidneys located?
3. what is the functioning unit of the kidney
4. what is the name of the blood vessel the bring blood into the kidney?
5. what is the name of the cluster of blood vessels going into Bowman’s
capsule?
6. which arteriole enters Bowman’s capsule?
7. Which exits?
8. what is the name of the convoluted tubule between Bowman’s
capsule and the loop?
9. What is the name of the loop?
10. what is the name of the twisted tubule after the loop?
11. what is the name of the structure that all the nephrons drain into?
1. can you name the blood vessels from the abdominal aorta to the
vena cava?
2. must be present for filtration to take place?
3. what happens in the loop of the cortical nephron?
4. what happens in the loop of the juxtamedullary nephron?
5. how much filtrate do we process each day?
6. how much urine do we secrete each day?
7. what is the first stimulus for urination?
8. list the structures from the glomerulus to the collecting duct
9. list the structures from the collecting duct to the urethra
10. what is meant by tubular threshold?
11. can you give an example of threshold?
12. what substances are secreted from the tubules?
13. name one hormone that influences reabsorption of water
1. Name another hormone that influences the reabsorption of water
2. summarize the process of urine formation
3. what does renin do?
4. does the kidney have to do with vitamin D?
5. what is erythropoietin and what does it cause?
6. What is urine made of mostly?