Learning Objective: To Know The Function Of The Bowman’s Capsule Ultrafiltration Learning Objective: To Know The Function Of The Bowman’s Capsule

Spec (c) (i) the structure, mechanisms of action and functions of the mammalian kidney (ii) the dissection, examination and drawing of the external and internal structure of the kidney (iii) the examination and drawing of stained sections to show the histology of nephrons To include the gross structure and histology of the kidney including the detailed structure of a nephron and its associated blood vessels AND the processes of ultrafiltration, selective reabsorption and the production of urine. PAG1, PAG2

Success Criteria Describe the process of ultrafiltration in the production of urine

Starter: Label the Nephron

Nephron

Urine Formation Urine formation is a 2 stage process: Ultrafiltration: where the blood is filtered of small molecules: importanly Urea Selective Reabsorption: Where essential molecules are taken back into the blood from the nephron

Bowmans (Renal) Capsule & Glomerulus Ultrafiltration occurs at the renal capsule where the blood is filtered from the glomerulus into the proximal convoluted tubule.

Ultrafiltration Filtration at the molecular level In Glomerulus large molecules are left in blood Small molecules pass into Bowman’s capsule

Ultrafiltration 2 Afferent arteriole is wider than efferent Blood in glomerulus under higher pressure than B’sC Pressure difference pushes fluid from G to B’sC

Ultrafiltration 3 3 layers between Blood in G and fluid in B’sC All are adapted to allow ultrafiltration Endothelium: narrow gaps between cells Basement membrane: fine mesh of collagen fibres and glycoproteins Epithelial cells in B’sC (called podocytes) has finger-like projections (called major processes) these ensure gaps between cells 3 layers between Blood in G and fluid in B’sC Endothelium of capillary Basement membrane Epithelial cells in B’sC

Basement membrane around capillaries and podocytes of Bowman’s capsule improve filtration   Endothelium of Capillary of glomerulus Podocytes (wall of B’s C Glomerular flitrate

Ultrafiltration 4 Filtered out of blood Left in capillary Water Amino Acids Glucose Urea Inorganic ions Left in capillary Blood cells Proteins Some Water (proteins ensure very low water potential)

Glomerular Filtration Substance Concentration in blood plasma (g dm-3) Concentration in Filtrate (g dm-3) Water 900 Proteins 80.0 0.05 Amino acids 0.5 Glucose 1.0 Urea 0.3 Uric acid 0.04 Creatinine 0.01 Na+, K+, Cl- 7.2 Above Relative Molecular Mass of 69,000 cannot pass through!

Group Task Sketch the glomerulus and Bowman’s capsule, adding as much detail as you can

Factors Affecting RATE of Glomerular Filtrate Water potential of blood in capillaries & filtrate in the renal capsule (greater in blood due to….) Pressure of blood in glomerulus 125cm3min-1

PPQ

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