Renal Physiology Introduction

Study Notes

Renal Physiology

The renal system consists of 2 kidneys, 2 ureters, urinary bladder, and urethra.
Functions of the kidney include excretion of waste products, control of ECF volume, osmolarity, electrolytes, blood pressure, and pH, as well as endocrine functions such as synthesizing erythropoietin, activating vitamin D, and releasing renin enzyme.

Nephron Structure and Function

The nephron is the functional unit of the kidney, with approximately 1 million nephrons in each kidney.
Each nephron consists of the glomerulus, tubules, and Bowman's capsule.
The glomerulus is a tuft of capillaries enclosed within a Bowman's capsule.
The tubules are specialized for reabsorption and excretion, and include the proximal convoluted tubules (PCT), loop of Henle (LH), distal convoluted tubules (DCT), and collecting duct (CDs).

Functions of the Nephron

Four main processes occur in the nephron: filtration, reabsorption, secretion, and excretion.
Filtration is the first step in urine formation, involving the bulk transport of fluid from blood to kidney tubule, resulting in an isosmotic filtrate.
Reabsorption involves returning filtered material to the bloodstream, with 99% of what is filtered being reabsorbed.
Secretion involves adding material to the lumen of the kidney from the blood, usually through active transport of toxins and foreign substances.
Excretion involves the loss of fluid from the body in the form of urine.

Renal Blood Flow

Renal blood flow (RBF) is approximately 1.2 L/min, which is about 20-25% of the cardiac output.
RBF is directed mainly to the renal cortex (90%), with only 10% going to the renal medulla.
RBF is autoregulated, maintaining a constant flow despite changes in mean arterial blood pressure between 80-180 mmHg.
RBF is affected by sympathetic stimulation, catecholamines, and dopamine.

Description

Learn about the structure and functions of the renal system, including the kidneys, ureters, urinary bladder, and urethra. Understand the excretory and endocrine functions of the kidneys, including blood pressure control and vitamin D activation.