Post on 23-Feb-2017
Renal system
Roger WatsonTwitter: @rwatson1955
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”
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.
The kidneys: function
The kidneys undertake three processes:
• Filtration• Secretion• Reabsorbtion
The kidneys: microstructure
• The kidneys are composed of nephrons which extend from the cortex into the medulla.
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.
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.
Glomerular filtration
Glomerular epithelium is permeable to water but but not to blood cells and protein.
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Secretion
What is it?
Secreted: hydrogen ion, potassium, ammonia, drugs, toxins
Reabsorbtion
The majority of the water that is filtered out at the glomerulus is reabsorbed.
Reabsorbed: sugar, sodium, vitamins, nutrients, water
Urinary bladder
Structure and function:
• bladder muscle known as DETRUSOR.
Internal sphincter (smooth muscle)
External sphincter (skeletal muscle)
Prostate gland
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.
Micturition
Excellent animation of the micturition reflex:
http://www.youtube.com/watch?v=qMR-rAVlbV0
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”
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.
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.
r.watson@hull.ac.uk
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r.watson@hull.ac.uk
Four things about…(a simple approach to anatomy and physiology)
The renal system