Lecture Notes on Kidney Structure and Function

Overview of Arterioles

Arterioles: Small arteries important in kidney function.
Afferent Arteriole:
- Connects to the glomerulus, a knot of capillaries.
- Larger diameter compared to the efferent arteriole.
- Direction of blood flow is indicated with arrows in diagrams.
Efferent Arteriole:
- Smaller diameter than the afferent arteriole.
- Blood exits the glomerulus through this vessel.
- Diameter difference causes pressure aiding in filtration.

Proximal Convoluted Tubule (PCT):
- A twisted segment of the nephron.
- Abbreviated as PCT.
Loop of Henle (Nephron Loop):
- Consists of a descending and ascending limb.
- Thick segment present in the ascending limb.
Distal Convoluted Tubule (DCT):
- Connects to the collecting duct.
Collecting Duct:
- Multiple nephrons drain into it.
- Ends at the papillary duct, leading to the renal papilla.
- Leads to the minor calyx, then the major calyx, renal pelvis, ureter, and finally the bladder.

Filtration: Removal of waste and fluids into the tubule system.
- Occurs exclusively at the glomerulus.
- Is size-dependent, filtering substances based on size, not necessity.
Reabsorption:
- Returns essential substances to the blood.
- Happens via peritubular capillaries that surround the tubules.
- Converts filtrate back into valuable blood components like glucose and amino acids.
Secretion:
- Additional process not covered fully in this excerpt but involves the removal of certain waste products and excess ions from blood into urine.

Filtrate vs. Urine:
- Fluid is termed 'filtrate' while within the nephron tubules.
- Once it reaches the collecting duct, it is called 'urine'.
Peritubular Capillaries:
- Surround tubules and are crucial for reabsorption and secretion processes.