What are the Components of the Urinary Tract?
- Kidney
- Uretra
- Bladder
- Urethra
What are the Functions of the Kidney?
- Elimination of nitrogenous waste e.g. urea and other metabolic waste
- Elimination of toxins
- Maintenance of appropriate salt concentrations - osmoregulation
- Regulation of blood pressure
- Regulation of pH level in the blood
- Regulation of vitamin D activity and calcium levels
- Release of erythropoietin (hormone that stimulates RBC production in the bone marrow)
Where are the kidneys positioned?
- Lie just under and closely attached to lumbar hypaxial muscle
- Left further back “left behind”
Describe the Kidney Structure
- Bean shape
- Capsule
- Cortex
- Medulla
- Pelvis
- Renal Artery and Vein
Why is the kidney bean shaped?
The indentation is the hilum and blood vessels, nerves, ureters enter/leave here
What is the Capsule?
Irregular dense fibrous connective tissue
What is the Cortex?
This contains Bowman’s capsules and convoluted tubules
What is the Medulla?
Contains collecting ducts and loop of Henle
What does the Pelvis do?
Whitish, fibrous connective tissue - urine drains into pelvis and enters ureter
The Renal Artery and Vein Provide how much Cardiac Output to the two Kidneys?
1/4
What is the Nephron?
Tubule + Associated Blood Vessels
What are the Components of the Nephron?
- Bowman’s Capsule
- Proximal Convoluted Tubule (PCT)
- Loop of Henle
- Distal Convoluting Tubule (DCT)
- Collecting Ducts
What is the function of the Bowman’s Capsule?
- Plasma filtered – high pressure in leaky glomerulus sitting in Bowman’s capsule made of leaky podocytes → ultrafiltrate
- Most components filtered (NOT big proteins)
- Glomerular filtration rate (GFR) = volume of filtrate formed
What is the function of the PCT?
- Active uptake into blood (reabsorption) of Na+. Water follows by osmosis (70% water and Na + reabsorbed)
- Most bicarbonate (HCO3-) reabsorbed in exchange for H+ - acid-base balance
- All glucose and amino acids reabsorbed
- Some wastes e.g. creatinine not reabsorbed
- Some toxins (e.g. histamine) and drugs (e.g. penicillin) secreted into filtrate here
- Vit D converted to active form
What is the function of the Loop of Henle?
- To make medulla tissue very concentrated in salt
- Works with collecting duct to fine tune final volume of urine (see later)
What is Aldosterone and what does it do?
- A hormone (produced in adrenal cortex)
- Action:
1. Retain sodium
2. Excrete potassium in urine
What is the function of the DCT?
- Fine tuning of sodium levels – controlled by aldosterone. Helps to maintain blood pressure
- Fine tuning of pH
- Fine tuning of calcium levels: calcium reabsorbed under control of parathormone from parathyroid glands
What does ADH stand for?
Anti - Diuretic Hormone
What is the function of the Collecting Ducts in relation to ADH?
- ADH Present - Collecting Duct is permeable to water and a small volume of urine is produced
- No ADH Present - Collecting Duct is NOT permeable to water and large volume of urine is produced
What is Erythropoetin ?
- Hormone which acts in bone marrow to promote production of RBC
- Produced by cells in kidney cortex in response to low oxygen levels in blood
Describe the Structure and Function of Ureters
- Urine collects in renal pelvis of kidney
- Urine leaves each kidney by single ureter at hilum
- Smooth muscle in wall – moves urine to bladder
- Transitional epithelium
- Each ureter opens into bladder
Describe the structure and function of Bladders
- Pear-shaped hollow organ
- Collects and stores urine
- When empty mainly within pelvis, when full ventral surface touches abdominal floor
- Ureters enter bladder close to neck
What is Transitional Epithelium?
- Specialised, stratified (layered) epithelium lining urinary system which can change shape depending on degree of distension.
When the Bladder is empty, what do the Transitional Epithelium cells look like?
Cuboidal
