1. The Urinary System Chapter 18

2. Overview of Urinary Anatomy
Play Urinary Anatomy movie

3. The organs of the urinary system include:

4. Functions of the urinary system (all done by kidneys):
Regulate the volume, concentration, pH and content of blood
Eliminate metabolic wastes as urine
3 processes occur within the kidneys to accomplish these goals

5. F
Filtration (F) – Pressure (blood pressure) forces some fluid (plasma) and small substances from blood to renal (kidney) tubules. Results in the formation of “filtrate” in the renal tubules; approx. 180 liters filtrate/day
blood
filtrate R
Reabsorption (R) – Movement (by passive & active means) of most fluid & many solutes from renal tubules back into the blood; approx. 99% filtate reabsorbed S
Secretion (S) – Selective movement of specific substances (e.g. H+, K+) from blood to tubules
urine
Filtered blood
Blood vessels (capillaries)
Renal tubules

6. Gross Anatomy of the Kidneys
Retroperitoneal organs
Left kidney more superior than right (due to liver)
Notch at medial border (hilus) for renal artery & vein, ureter
Each kidney surrounded by 3 layers of CT:
renal capsule – innermost layer of dense CT
adipose capsule – middle layer protecting & insulating kidneys
renal fascia – outer layer holding kidneys in place in abdominal cavity

7. Internal Anatomy of the Kidneys
Cortex
Medulla
pyramids
renal papillae
renal columns
Pelvis - collecting basin
minor calyces
major calyces
renal pelvis
where urine formation occurs

8. Microscopic Anatomy of the Kidneys
Functional unit of the kidneys is the “Nephron”
Nephron = renal corpuscle + renal tubules

9. glomerulus – capillary network
Renal corpuscle – 1st part of the nephron; site of filtration; comprised of
glomerulus – capillary network
Bowman’s capsule – double layered capsule of epithelial tissue (inner visceral (podocyte) layer/outer parietal layer), surrounding glomerulus
Bowman’s capsule (parietal (capsular) layer)
Visceral layer of Bowman’s capsule (podocytes)
glomerulus
capsular space
Filtration occurs across “endothelial capsular (filtration) membrane” – junction between glomerular endothelium & podocytes; results in formation of “filtrate” in capsular space

10. Representative Nephron
proximal convoluted tubule
reabsorption
Loop of Henle
more reabsorption
distal convoluted tubule
Secretion, some reabsorption
renal corpuscle
filtration
H2O
solutes
filtrate
COLLECTING SYSTEM
collecting duct
variable secretion &/or reabsorption
papillary duct
delivery of urine to minor calyx
Filtrate from renal corpuscle will move into PCT  loop of Henle DCT; and then into a collecting system of tubes  minor calyx)
Connecting tubule

11. Blood supply to Kidneys
Renal artery
Renal vein
Renal artery  afferent arterioles  glomerulus  efferent arterioles
Efferent arteriole
Afferent arteriole
glomerulus

12. Efferent arterioles branch into a second capillary network, the peritubular capillaries, which surround the renal tubules
Reabsorption & secretion occur between the renal tubules & peritubular capillaries
Peritubular capillaries  venules renal vein

13. Juxtaglomerular Apparatus (JGA)
Extremely important to regulate the rate of filtration that occurs at the glomerulus (glomerular filtration rate “GFR”)
GFR directly related to glomerular blood pressure –
increased BP  increased GFR
decreased BP  decreased GFR
To regulate glomerular BP, we have a feedback system – the juxtaglomerular apparatus (JGA)
JGA =
juxtaglomerular cells of the afferent arteriole – recognize if renal BP is too low & then can respond
macula densa cells of the distal convoluted tubule – recognize if decreased filtrate produced or too many solutes within filtrate & then can respond

14. Once urine is formed, it will move from the pelvis of the kidneys into the ureters
retroperitoneal, muscular tubes running from kidneys to urinary bladder
lined with transitional epithelium
transports urine primarily by peristalsis

15. Urinary bladder
Hollow muscular organ that temporarily stores urine prior to “micturition”
Lined with mucosa of transitional epithelium with rugae
Muscularis of 3 layers of smooth muscle known as “detrussor muscle”
Internally have “trigone” – triangular area formed by openings of ureters & urethra
Micturition reflex – stretch receptors in wall of bladder stimulate smooth muscle of detrussor muscle (involuntary); stimulation of external urethral sphincter of skeletal muscle (voluntary) & of internal urethral sphincter (involuntary)

16. Urethra Transports urine out of body
Inner urethral sphincter of smooth muscle; external urethral sphincter of skeletal muscle
Anatomically different in men & women

17. The End!!!