The renal system consists of the kidneys and urinary bladder. The kidneys play a vital role in maintaining fluid balance and composition in the body, regulating the internal environment. The kidneys are composed of nephrons which filter blood, reabsorbing necessary substances and secreting waste products to produce urine. Urine is stored in the bladder and emptied during micturition.

1. Renal system
Roger Watson
Twitter: @rwatson1955

2. Renal system
The renal system is comprised of the kidneys and these are directly
linked to the urinary bladder.
The kidneys play a vital role in maintaining fluid volume and
composition in the body and are, thus, a major regulator of the
internal environment.
Referred to as:
“The ultimate regulator of homeostasis”

3. Bozeman biology You Tube link
The urinary system

8. The kidneys
•The kidneys are two paired organs situated in the retroperitoneum.
•They are supplied with blood by the renal arteries which are directly
linked to the aorta.
•25% of cardiac output goes to the kidneys
•The gross anatomy of the kidney is composed of:
• cortex
• medulla
•Each kidney has a ureter that connects it to the urinary bladder.

10. The kidneys: function
The kidneys undertake three processes:
•Filtration
•Secretion
•Reabsorbtion

11. The kidneys: microstructure
•The kidneys are composed of nephrons which extend from the cortex
into the medulla.

13. The kidneys: microstructure
•The kidneys are composed of nephrons which extend from the cortex
into the medulla.
•The nephrons are intimately associated with blood vessels called the
vasa recta.

16. The kidneys: microstructure
•The kidneys are composed of nephrons which extend from the cortex
into the medulla.
•The nephrons are intimately associated with blood vessels called the
vasa recta.
•At the top of each nephron – in the cortex - the Bowman’s capsule is
located.
•The Bowman’s capsule contains the glomerulus.

18. Glomerular filtration
Glomerular epithelium is permeable to water but but not to blood cells
and protein.

19. XXXX

20. Secretion
What is it?

21. Secreted: hydrogen ion, potassium, ammonia, drugs, toxins

22. Reabsorbtion
The majority of the water that is filtered out at the glomerulus is
reabsorbed.
Reabsorbed: sugar, sodium, vitamins, nutrients, water

27. Urinary bladder
Structure and function:
• bladder muscle known as DETRUSOR.

29. Internal
sphincter
(smooth muscle)
External
sphincter
(skeletal
muscle)
Prostate
gland

33. Micturition
The passing of urine.
Unable to control bladder fully until ~ 2 years old
• cannot inhibit spinal reflexes
When bladder contains 200-250 ml stretch receptors send signals to
the brain and we sense that the bladder is full.
Sensory impulses lead to relaxation of internal sphincter (smooth
muscle).
External sphincter relaxed when it is convenient to pass urine in
adults.

34. Micturition
Excellent animation of the micturition reflex:
http://www.youtube.com/watch?v=qMR-rAVlbV0

35. Renal system
The renal system is comprised of the kidneys and these are directly
linked to the urinary bladder.
The kidneys play a vital role in maintaining fluid volume and
composition in the body and are, thus, a major regulator of the
internal environment.
Referred to as:
“The ultimate regulator of homeostasis”

36. Questions
1. Describe the position and composition of the kidneys.
2. What vessels are attached to the kidneys? What fraction of the
cardiac output goes to the kidneys?
3. What three functions does the kidney undertake and in what
order?
4. What are the functional units of the kidneys? Name the regions of
this functional unit.
5. Describe the glomerulus.

37. Questions
6. Describe what happens at the glomerulus.
7. Name four things that are secreted into the nephron.
8. Name four things that are reabsorbed into the blood at the nephron.
9. Describe the urinary bladder. What is the major difference in males
and females?
10. Describe normal micturition.

38. r.watson@hull.ac.uk
Four things about…(a simple approach to
anatomy and physiology)
Special Senses
r.watson@hull.ac.uk
Four things about…(a simple approach to
anatomy and physiology)
The renal system