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

Functions of the Renal System 1) Regulates ECF volume: a) Regulates Osmolarity: 2) Regulates pH of body fluids: b) Regulates ion balance:

Functions of the Renal System 3) Eliminates metabolic waste: 4) Removes foreign substances: 5) 2 o Endocrine gland: a) erythropoietin b) renin

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

~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. In Human Renal System

Nephrons

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

Filtration: Reabsorption: Secretion: Excretion:

Overview of the Renal Process in Nephron

Barriers to Filtration 1. Endothelium 2. Basement Membrane 3. Podocytes Restricts cells Restricts proteins 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

Juxtaglomerular Apparatus is: Macula Densa - specialized portion of the DCT that sits in between the Afferent and Efferent arteriole Juxtaglomerular (JG) cells - cells predominantly around afferent arteriole to adjust diameter.

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

Arteriole Resistance Changes Blood flow and GFR

2. Tubuloglomerular Feedback Juxtaglomerular Apparatus

ANS-Sympathetic Modulation Hormones –Angiotensin II – vasoconstrictor. –Prostaglandins – vasodilator. 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.