The urinary system includes the kidneys, ureters, bladder, and urethra. The kidneys filter the blood to remove wastes and regulate fluid, electrolyte and acid-base balance. The kidneys contain nephrons that filter blood in the glomerulus and reabsorb nutrients in the tubules. The remaining fluid becomes urine and drains into the bladder via the ureters. When full, the bladder empties urine through the urethra and out of the body. The urinary system works to regulate blood volume and pressure, maintain electrolyte and acid-base balance, conserve nutrients, and remove wastes and toxins from the body.

1. Urinary System-
Anatomy and Physiology
Zoe McCarthy
1

2. Urinary System in Context
2

3. Urinary System in Context
System How does it do it?
3

4. Functions of the Urinary system
• 1. Regulating blood volume and pressure
• 2. Regulating plasma concentrations of sodium,
potassium, chloride and other ions
• 3. Stabilising blood pH
• 4. Conserving nutrients
• 5. Detoxifying poisons (with the liver)
4

5. Organisation of the Urinary System
• Kidneys
• Ureters
• Urinary bladder
• Urethra
5

6. Position of the Kidneys
CT abdomen with contrast MRI coronal abdomen
6

7. Protection of the Kidneys
• 3 layers of connective
tissue:
– Inner layer- Renal capsule
– Middle layer- Adipose
capsule
– Outer layer-Renal fascia
Renal cortex
Retroperitoneal space
7

8. Surface anatomy of the Kidney
• Hilum is located on
the medial surface
10 cm
5.5cm
3cm
8

9. Internal Structure of the Kidney
Renal pyramids
Renal papilla
Renal Columns
Renal Lobe
9

10. Microscopic structure of the Kidney
and Urine Production
10

11. Renal Corpuscle and Filtration
11

12. Nephron-Tubular System
1. Proximal convoluted
tubule
2. Descending loop of
Henle
3. Ascending loop of
Henle
4. Distal convoluted
tubule
5. Collecting duct
12

13. Summary so far…..
Blood enters the kidney
through the renal artery at
the site of the hilum
The renal artery divides in
to ever smaller arteries and
arterioles
Afferent arterioles take blood to
the glomerulus to be filtered
Once blood is filtered
efferent arterioles take blood
away from the glomerulus
The glomerulus is a
network of capillaries
which filters the blood
Products which are filtered out:
water, mineral salts, amino acids,
glucose, hormones, urea, toxins
Products which do not filter
and remain in the blood:
Leukocytes, erythrocytes,
platelets, plasma proteins
The filtered substances
move into the proximal
convoluted tubule
The PCT is concerned with
reabsorption- organic nutrients are
reabsorbed and water follows
because there is a concentration
gradient
The remaining filtrate moves
into the descending loop of
henle. This is lined with thin
cells so water moves out
Because water has been
reabsorbed the concentration
of the filtrate is not very high
The walls of the ascending loop
of henle are lined with thicker
cells, so water can’t pass in or
out. Instead sodium and
chloride is pumped out actively
The filtrate now enters the
distal convoluted tubule- is it
now only 20% of what it
In the DCT the volume and originally was.
composition of the filtrate
can be adjusted but this is
controlled by hormones
From the DCT the filtrate now
passes into the collecting duct.
A number of other nephrons join
up to the cleectig duct which
travels through the medulla to the
renal papilla wher the filtrate is
emptied in the minor calyx
4-5 minor calyces join up to
make a major calyx
2-3 major calyces join up
to form the renal pelvis The renal pelvis joins the
ureter at the hilum
The ureter transport the
filtrate/urine from the kidney
to the bladder
13

14. The Formation of Urine
• 3 processes involved in the formation of
urine.
– Simple filtration
– Selective reabsorbtion
• Hormonal control-
» Parathyroid hormone, calcitonin
» Anti diuretic hormone
» Aldosterone
– Secretion
14

15. Ureters
• Superiorly
• Continuous with the renal
pelvis
• Inferiorly
• Pass through the abdominal
cavity, behind the
peritoneum, infront of the
psoas muscle, into the
pelvic cavity ehere they
enter the posterior wall of
the bladder
• 25-30 cm in length
15

16. Ureter- Cross Section
• 3 layers of tissue
– Outer layer
• Fibrous tissue
– Middle layer
• Muscle
– Inner layer
• Epithelium
16

17. Bladder
17

18. Bladder- structure of
• 3 layers
– Outer layer
• Loose connective
tissue
– Middle layer
• Smooth muscle and
elastic fibres
– Inner layer
• Lined with transitional
epithelium
18

19. Urethra
• Extends from the
base of the bladder to
the outside world.
• Anatomical
differences mean that
male and female
urethras are different.
– Female: 4cm
long
– Male: 14cm
long
19

20. Urethra- structure of
• Muscle layer
• Submucosa layer
• Mucosa
20