Renal System: Functional unit is the Nephron. Kidneys (2) Ureter (2) Bladder (1) Urethra (1)

Functions of the Renal System 1) Regulates ECF volume: a) Regulates Osmolarity: b) Regulates ion balance: 2) Regulates pH of body fluids: 3) Eliminates metabolic waste: 4) Removes foreign substances: 5) 2o Endocrine gland:

Outer renal cortex Inner renal medulla ~ 1.25 million nephrons in each kidney ~ 180 Liters of Filtrate made each day ~ 1.5 Liters of urine excreted each day

The Nephron 1. Renal Corpuscle 2. Renal Tubule a) Glomerulus b) Bowman’s Capsule c) Bowman’s Space 2. Renal Tubule a) Proximal CT b) Loop of Henle c) Distal CT

In Human Renal System ~85% are Cortical nephrons Renal corpuscle higher in cortex. Shorter loop of Henle. ~15% are Juxtamedullary nephrons Renal corpuscle closer to medulla. Loop of Henle extends deep into medulla.

1. Renal Corpuscle (3 parts)  Glomerulus   Bowman’s Capsule Bowman’s Space

2. Renal Tubule a) Proximal Convoluted Tubule (PCT) b) Loop of Henle c) Distal Convoluted Tubule (DCT)

Filtration: Reabsorption: Secretion: Excretion:

Overview of the Renal Process in Nephron

Barriers to Filtration 1. Endothelium Restricts cells 2. Basement Membrane Restricts proteins 3. Podocytes Changes Glomerular Filtration Rate (GFR)

Filtration is favored by Hydrostatic Pressure (HP) of Glomerulus. Opposed by Colloid Osmotic Pressure (COP) of blood. Opposed by Hydrostatic Pressure of Bowman’s capsule.

Glomerular Filtration Rate (GFR) e.g., normally GFR is 180L/day (or 125ml/min) Things that can influence GFR: Changes in blood pressure can change GFR but this is autoregulated.

Autoregulation of Renal System

Autoregulation 1. Myogenic Stretch 2. Tubuloglomerular Feedback If ↑ blood pressure in afferent arteriole, this stretches smooth muscle and it contracts in response, thus vasoconstricts. This decreases blood flow (↓ pressure and GFR)

Arteriole Resistance Changes Blood flow and GFR

Autoregulation 2. Tubuloglomerular Feedback Macula Densa JG Cells Juxtaglomerular Apparatus JG Cells

ANS-Sympathetic Modulation Both Afferent and Efferent Arterioles are innervated by SYM neurons. NE binds to  receptors on smooth muscle, causing vasoconstriciton. e.g., if hemorrhage or dehydration, ↑ Sym, vasoconstriction, ↓GFR, conserves fluid volume. Hormones Angiotensin II – vasoconstrictor. Prostaglandins – vasodilator.