Osmolarity Osmolarity is the solute concentration of a solution Animals are either: Osmoregulators: maintain a constant internal solute concentration. Most terrestrial animals & some marine organisms (bony fish). Osmoconformers: organisms whose internal solute concentration is the same as the environments. Starfish, crabs.

Malpighian tubule system

Excretion Removal of waste products from the body e.g. urea Draw and label fig. 4, pg. 487

KidneyFilter waste products from blood Renal arteryBlood to kidney Renal veinBlood away from kidney Renal pelvisArea urine collects in Renal medullaArea surrounding renal pelvis Renal cortexArea outside renal medulla UreterTube connecting kidney and bladder BladderStore urine before excretion

Renal arteryRenal vein Blood enters the kidney Variable levels Higher levels of: Urea, toxins, or any other substance which is not fully metabolised by the body e.g. drugs, excess water, excess salt Blood leaves the kidney Constant levels Although the blood in the renal viein will still contain these substances, it will be at a lower rate.

Nephrons How many nephrons are in each kidney? 1.25 million (approx.) What is the purpose of these nephrons? Filtration!

Afferent arteriole has a slightly larger diameter than the efferent arteriole this increases the pressure of the blood inside the glomerulus The glomerulus (capillary bed) has fenestrations (slits which open with high blood pressure) Ultrafiltration removal of substances within the glomerulus/fenestrations Basement membrane prevents larger molecules (e.g. proteins, blood cells etc.) being filtered out Filtrate passes into proximal convoluted tubule Substances such as water, salt ions & glucose are reabsorbed from the proximal convoluted tubule into the peritubular capillary bed

A common kidney question, could be interpreting a table like this one.. So explain the information in this table MoleculeAmount in blood plasma (mg 100 ml -1 ) Amount in glomerular filtrate (mg 100 ml -1 ) Amount in urine (mg 100 ml -1 ) Proteins>70000 Glucose>90 0 Urea30 >1800

Proximal convoluted tubule Selective reabsorption by active transport First part of the nephron Pg. 491 for diagram

Substance being reabsorbed Mechanism Salt ionsActive transport from tubule  peritubular capillary bed e.g. NA +, Cl -, K + WaterOsmosis from tubule  peritubular capillary bed GlucoseActive transport, all glucose is reabsorbed if the nephron is healthy Active or Passive?

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The Loop of Henle Maintains hypertonic conditions in the medulla Descending portion of the loop is permeable to water, but impermeable to salt ions The opposite is true in the ascending portion of the loop Hypotonic – lots of water present Hypertonic – many ions present (typically the medulla region is hypertonic) Antidiuretic hormone (ADH) is another hormone produced by the pituitary gland, transported in the blood stream. The collecting duct will reabsorb water depending on the presence or absence of ADH Permeability of the collecting duct determined by this hormone