1. Structure and Function of the Kidneys

2. Kidney External Structure
Renal Capsule - fibrous outer layer
Renal Hilum - indentation that gives it bean shape
Where renal arteries, veins, and ureters attach

3. Three Layers of Internal Anatomy
Renal Cortex: outer layer under the capsule where blood is actually filtered
Renal Medulla: middle layer that contains renal pyramids
Renal pyramids: collect urine once it is made in the cortex
Separated by renal columns which are extensions of the cortex
Renal Pelvis: innermost layer that contains large urine collecting cups
Large collecting cups are called major calyces and are made up of smaller ones called minor calyces

4. Blood Flow to the Kidney
Renal artery enters the kidney and then branches into smaller and smaller arteries inside the kidney
The smallest of the arteries is the arcuate arteries that arch around the base of the renal pyramids

5. Blood Flow Through the Kidney
Each capillary bed can be found in close association with a renal nephron, which is the filtration unit of the kidney

6. Nephron Structure Renal Corpuscle → Filter for blood
Enters via glomerulus, which is surrounded in a double-layered membrane called Bowman’s Capsule
Membrane filters out everything but blood cells and proteins into Bowman’s capsule
Called glomerular filtrate

7. Nephron Structure
Renal Tubule -> Series of tubes that filters the glomerular filtrate so all the bad stuff gets removed and all the good stuff goes back to the blood
Proximal Tubule → Loop of Henele → Distal Tubule → Collecting Ducts → Minor Calyces → Major calyces → Renal Pelvis → Ureter
Surrounding capillaries allow for reabsorption back into the bloodstream

8. Filtration
Glomerular Filtration: Blood filtered by glomerulus forms glomerular filtrate containing water, salts, nutrients, and waste
Tubular Reabsorption: Nutrients and salts are actively reabsorbed and some water is passively reabsorbed by the peritubular capillaries
Tubular Secretion: Substances such as urea and creatinine are actively secreted from the peritubular capillaries into the distal tubule for removal from the body via urine

9. Kidney Fluid Chemistry
Substance
Filtered, Reabsorbed, or Secreted
Amount in Plasma
(mg/100mL)
Amount in Glomerular Filtrate
Amount in Urine
Protein
Not Filtered
none
Glucose
Filtered and Reabsorbed
100
Sodium
Filtered and Mostly Reabsorbed
142
128
Potassium
Filtered and Secreted 5 60
Urea 26
1820
Creatinine
1.1
140

10. Control of Tubular Reabsorption and Secretion
Active and passive transport move substances across the tubular membrane to either secrete or reabsorb them
Hormones regulate blood pressure
Antidiuretic hormone: causes more water to be reabsorbed to increase blood pressure
Aldosterone: increase reabsorption of sodium and secretion of potassium to increase blood pressure
Atrial natriuretic peptide (ANP): protein secreted by the atria of the heart that decreases sodium reabsorption and increases urination to decrease blood pressure

11. Urinary Bladder
Once the glomerular filtrate leaves the collecting ducts is it called urine
→ Renal Pelvis → Ureters → Urinary Bladder
As urine accumulates the bladder stretches due to the transitional epithelial lining and the rugae within it

12. Urination
When the bladder is full it sends a signal up the spinal cord to the pons, which sends signals down the spinal cord to cause the contraction of the muscular walls of the bladder which causes it to empty through the urethra