Co-ordination and Regulation of Processes 4.6 Control Systems Co-ordination and Regulation of Processes

Homeostasis What is homeostasis? Mechanisms by which a constant internal environment is maintained.

The urinary system Aorta Renal vein Kidney Renal artery Vena cava Ureter Aorta Renal vein Bladder Renal artery Vena cava Urethra © 2008 Paul Billiet ODWS

Kidney – structure and function Deamination in Liver produces Urea… Kidney – structure and function Biological principles in action

Human kidney ureter renal artery renal vein attached here

1 – Filtration by the Kidney cortex Supplied with blood from renal artery Inside it splits into many fine capillaries Each capillary supplies blood to hundreds of thousands of tiny filtration units called nephrons Renal artery Renal vein Ureter Medulla

The blood supply

The cortex (view x100) Tubule (Malpighian) renal corpuscles

The corpuscle (view x400) Glomerulus – a ball of capillaries Bowman’s capsule

Medulla (view x400) Tubules Capillaries

The nephron In the cortex In the medulla

The nephron Bowman’s capsule Branch of renal artery Glomerulus Branch of renal vein Branch of renal artery proximal (1st) convoluted tubule Capillary Distal (2nd) convoluted tubule Collecting duct Loop of Henlé

2. Liquid filtered from blood under pressure (filtration) Glomerulus brings a large surface area of blood capillaries in close contact with Bowman’s capsule 2. Liquid filtered from blood under pressure (filtration) Glomerular filtrate produced containing: -water -glucose -salts -urea (Protein molecules and red blood cells do not pass into tubule as they are TOO BIG!!!!) Blood from renal artery enters wide capillary Blood travels through narrow capillary towards renal vein Filtration Glomerular filtrate The blood plasma is filtered at about 150 litres per day

Blood plasma v Filtrate Component Plasma / mg 100cm-3 Filtrate Urea 0.03 Glucose 0.10 Amino acids 0.05 Salts 0.72 Proteins 8.00

The nephron functions Freely permeable to water Impermeable to water Variable permeability to water

The nephron osmoregulation Active reabsorption Variable permeability to water Impermeable to water Freely permeable to water Na+ Na+ Na+ H2O H2O Passive osmosis Ultrafiltration under pressure 80% of water reabsorbed

The nephron osmoregulation Variable permeability to water Impermeable to water Freely permeable to water Collecting duct More and more salty Loop of Henlé Na+ H2O H2O

The nephron osmoregulation The blood concentration is monitored by osmoreceptors in the hypothalamus If the concentration rises the hypothalamus releases ADH ADH makes the collecting duct walls more permeable More water is reabsorbed from the filtrate as the ducts pass through the salty tissues of the medulla

The nephron osmoregulation The urine released into the pelvis is more or less concentrated depending upon the blood concentration Excessive sweating and eating salty food will produce concentrated urine Drinking and cold weather will produce dilute urine

Kidney reabsorption Component Filtrate / mg 100cm-3 Urine Urea 0.03 2.00 Glucose 0.10 Amino acids 0.05 Salts 0.72 1.50 Proteins © 2008 Paul Billiet ODWS

Reabsorption Microvilli on cuboidal epithelial cells Dr Millet USC Med schooll Kidney tubule with brush border © 2008 Paul Billiet ODWS

The afferent tubules reabsorb: 80% of water All of the glucose All of the amino acids Blood pH is regulated Blood salt levels are regulated Urea is left behind and even secreted into the tubules Reabsorbed molecules pass into the surrounding capillaries

Summary of kidney function

Controlling Water Concentration Blood -important part of internal environment -constantly changing water concentration -e.g. exercising drinking lots of water The body uses negative feedback control to regulate water content of the blood

How does it work?

Control of Water animation