This is a simple ppt on Urinary System.

2. What is the difference between.....
Excretion is removal of Defecation is removal of
nitrogenous wastes undigested waste

3. Types of nitrogenous wastes
AMMONIA URIC ACID UREA
Some living beings waste in Some living Some living
the form of ammonia. organisms release organisms release
Ammonia is highly toxic. waste in the form of waste in the form
These organisms are known uric acid. of urea.
as ammoniotelic. uric acid is least toxic. Urea is neutral and
Examples- These organisms are less toxic.
Sponges, coelenterates and called uricotelic. These organisms
bony fishes. Examples- are called ureotelic.
insects, reptiles and Examples- desert
birds. mammals, cartilage
ous fishes and
humans

4. Excretory organs in
humans....Make a Guess

5. EXCRETORY SYSTEM IN
HUMANS
• The excretory system or the urinary system consists of
a pair of kidneys
• a pair of ureters
• urinary bladder
• urethra
Location of the Kidney-
In the abdominal cavity below the stomach, on either
side of the vertebral column.
The right kidney is placed slightly lower than the left
kidney as it is pushed down by the large right liver
lobe.

6. Blood vessels entering and leaving
the kidney
The descending aorta branches to form the renal artery that enters the kidney, and
the renal vein comes out of the kidney to join the inferior vena cava.
Kidneys are bean shaped structures about 10 cm long. The outer side is convex and
the inner margin is concave. In the middle of the concave side a notch is present
through which structures enter and leave the kidney. This is called Hilum.

7. Other Parts of the Urinary System
URETER URETHRA
10-12 inches length, half an inch Narrow tube from bladder to the
diameter. exterior.
Enters the bladder through
oblique tunnels that function as Sphincters control the urination.
valves. Female it is 3-4 cm long and males 18-
Carries urine from kidney to the 20 cm long.
urinary bladder.
URINARY BLADDER
Pear shaped highly distensible
sac-like reservoir, store urine
temporarily.
Present in the pelvic region
Opening to the urethra is guarded
by sphincter muscles.
Can hold about 0.5 to 1liter of
urine.

8. Internal Structure of the kidney
Two distinct regions are seen-
Cortex- Outer dark region has a dotted
appearance.
Medulla- Pale inner region has pyramid
like structures .
The pyramids open into small tube like
structures the minor calyx and two or
three minor calyx opens into the a major
calyx.
The all the major calyces opens into the
pelvis.
The pelvis is the proximal end of the
ureter that receives the urine from the
calyces.

9. Structure of the Kidney Tubule
• Each kidney is made up of
microscopic, coiled tube like units called
nephrons or uriniferous tubules.
• There are approximately 1.25 to 1.5
million nephrons in one kidney.
1. The nephron has two parts-
A cup shaped body called Malpighian
corpuscle or Renal corpuscle.
2. A tubular part called renal tubule.
Questions:
1. What gives Cortex its dotted
appearance?
2. What gives Medulla a Striated
appearance?

10. PARTS OF THE NEPHRON
• Branches of the renal artery within
the kidney produce afferent
arterioles.
• Each afferent arteriole leads to a
network of capillaries called
a glomerulus.
• Blood leaves the capillaries of the
glomerulus via an efferent
arteriole and enters capillaries in the
medulla called peritubular
capillaries, which collect much of the
water that was lost through the
glomerulus.
Venules from the peritubular
capillaries lead to the renal vein, which
exits the kidney and returns blood to
the inferior vena cava.

11. RENAL TUBULE
The tubular part of the nephron is known as
renal tubule.
It has three parts- Proximal convoluted
tubule, Loop of Henle and distal convoluted
tubule.
The proximal part of the renal tubule is highly
coiled and is present in the renal cortex. This part
absorbs water and all the useful salts, amino
acids and glucose.
The proximal part extends downwards to form a narrow tubular part- the descending
part, a loop and an ascending part. This lies in the medulla and mainly absorbs water
from the nephric filtrate.
The ascending limb leads to a convoluted part the which also lies in the cortex. This
opens into the collecting tubule. This part excretes some ions and ammonia into the
filtrate.
Try this link to lead yourself to a pretty good animation explaining the process.
Http://www.biologymad.com/resources/kidney.swf

12. Urine Formation
INVOLVES THREE PROCESSES:
ULTRAFILTRATION.- Filtration under
high pressure. Bowman's capsule acts
as ultra-filters. When blood flows
through glomerular capillaries- all
substances (except blood cells and
plasma proteins) are filtered. Main
reason for ultrafiltration is the
difference in the size of afferent and
efferent arterioles. The efferent
arteriole are narrower than the afferent
arteriole.
TUBULAR REABSORPTION.- TUBULAR SECRETION.- secretion of
absorption of useful substances from harmful substances from the blood into
the nephric filtrate into the blood. the nephric filtrate by the cells of DCT
(diffusion and active transport)

13. Urine Formation cont.
Steps of Urine Formation
•Reabsorption of
remaining water and
Chlorides.
BOWMAN’S •Re-absorbs most LOOP OF •Walls secrete K+ and
CAPSULE water about HENLE foreign chemicals such
•Ultrafiltration
2/3, and much of as penicillin and other
•Receives glucose/Na+ / •Some absorption drugus into the
glomerular Cl ion. of water and Na+
forming urine
Filtrate
Glomerulus
PCT
DCT

14. Role of Hormones in Urine
Formation
ADH- Anti Diuretic Hormone, Diuresis means increased production of urine
• Results in reabsorption in collecting tubule
• Secreted by posterior pituitary gland
• It is released in response to high blood Osmolarity.
• Increased osmolarity results from water loss and dehydration, thus body
needs to retain more water.
• ADH allows water to be reabsorbed from collecting tubule and not leave the
body.
• Water is absorbed by osmosis due to high Medullary hypertonicity.
• Lack of ADH causes large amount of dilute urine. A condition called diabetes
insipidus.
• Question: Why during workout you are suggested to drink limewater instead
of plain water?
Reabsorption of NaCl from the distal convoluted tubule is controlled by aldosterone
from the adrenal cortex. One of a group of hormones from the
adrenal cortex called mineralcorticoids which regulate salt levels in the body.

15. Constituents of Urine
Organic Gm/L Inorganic Gm/L
Urea 2.3 NaCl 9.0
Creatinine 1.5 KCl 2.5
Uric Acid 0.7 Ammonia 0.6
Others 2.6 Others 2.5
• Mainly Urine consists of about 95% WATER and 5% of SOLID wastes dissolved
in it.
• Abnormal Constituents in urine
1. Blood Cells- Blood passing thru’ Urine due to infection or kidney stone or
tumor.
2. Glucose/Glycosuria – Excess glucose passing through urine due to DIABETES
MELLITUS.
3. Albumin – Due to high BP or bacterial infection permeability of Bowman’s
Capsule membrane increases.
4. Bile Pigments- Anemia, Hepatitis (jaundice) or liver cirrhosis.

16. References
• Tges Biology Dept
• Science direct
• www.nature.com