Renal system 1 Flashcards
Urinary system structure
2 kidneys
2 ureters
1 bladder
1 urethra
kidney functions
- excreting metabolic wastes, toxins, drugs (urine)
- regulating total water volume and total solute concentration in water
- regulating ion concentrations in ECM fluid
- ensuring long-term acid base balance
- activation of vitamin D
- carrying out gluconeogenesis
Endocrine function
- Erythropoietin (regulating the RBC production_
- Renin (regulating the BP)
Kidney gross anatomy
Urine flow: renal pyramid -> minor calyx -> major calyx -> renal pelvis -> ureter
The nephron
Consists of
Structural and functional units that form urine
Approx. 1 million per kidney
Blood in -> filtrate out
Consists of: corpuscle and renal tubules
4 things of the nephron
- filtration
- reabsorption
- secretion
- excretion
Renal corpuscle
Bowman’s capsule + glomerulus, site where blood is filtered
Glomerulus
- afferent arteriole enters glomerulus
- capillaries highly porous and speciiased for filtration
- blood pressure in glomerulus high
- filter allows molecules smaller than 3nm to pass (water, glucose, amino acids, nitrogenous wastes)
- filter retains: cells, most proteins -> some blood leaves via efferent arteriole
- everything past the filter = filtrate = plasma = derived fluid that renal tubules process to form urine
Renal tubule
- long coiled tube that collects filtrate 4 parts 1. proximal convoluted tubule 2. loop of henle: concentration gradient 3. distal convoluted tubule: secretion 4. collecting duct: excretion
Nephron location
- Cortical nephrons
- almost entirely in renal cortex
- make up 85% of nephrons
- Only tip of loop of Henle dip into medulla - Juxtamedullary nephrons
- renal corpuscle near the medulla
- loop of Henle dips deep into the medulla
- function in maintain osmotic gradient
four major renal processes
- glomerular filtration: produces cell and protein free filtrate
- tutbular reabsorption: selectively returns 99% of substances from filtrate to blood in renal tubules and collecting duct
- tubular secretion: selectively moves substances from blood to filtrate in renal tubules and collecting ducts
- excretion: removal of urine from the body
glomerular filtration
in the glomerulus -> site where blood is filtered
blood into glomerulus -> afferent arteriole
blood out of glomerulus -> efferent arteriole
Efferent arteriole carred blood from glomerulus that gives rise to 2 types of capillary beds: peritubular capillary, vasa recta
- cortical radiate vein
blood vessels of the kidney
- Arterial flow: aorta -> renal artery -> segmental -> interlobar -> arcuate -> cortial radiate artery
- Glomerulus capillaries - afferent and efferent arteriole
- venous flow: cortical radiate vein -> arcuate -> interlobar -> renal veins -> inferior vena cava
Pertiubula capillaries
in the cortex
low-pressure, porous capillaries adapted for absorption of water and solutes
Vasa recta
In the medulla
Straight capillaries, function in formation of concentratied urine
Cells of the glomerulus
Capillary epithelial cells - make up blood vessels of the glomerulus
Podocytes - make up the filter
Mesangial cells - keeping the filter free of debris
Podocytes
In glomerulus Spider shaped cells Prevent passage of proteins through filter Each glomerulus 500-600 podocytes Have limited ability for self-renewal Support capillary loops
Mesangial cells
Specialised cells around blood vesses in the glomerulus -> support capillary loops
Macromolecules stuck in filtration membrane are engulfed by glomerular mesangial cells
Keep the filter free of debris
Bowman’s capsule
Cup-shapes, hollow structure surround glomerulus
Consists of 2 layers: parietal layer (simple squamous epithelium)
Visceral layer (glomerular capillary covered by podocytes)
Clings to glomerular capillaries
Branching epithelial podocytes
Glomerular filtration barriers
Filtrate must cross 3 barriers to enter glomerular capsular space
- capillary epithelial cell layer
- basement membrane
- surrouns epithelial cell layer of visceral layer
Glomerular filtration
Movement of protein-free plasm from glomerulus to Bowman’s capsule
Passive process, filtered under pressure (hydrostatic pressure to force fluid and solutes through)
Fluid entering Bowman’s is ultra-filtrate or filtrate - no reabsorption into capillaries occurs
Glomerular filtration pressure
Driven by starling forces:
- hydrostatic pressure
- oncotic pressure
Hydrostatic pressure
Pressure any fluid exerts in a confined space
Pressure that blood exerts = BP
When blood moves, fluid moces out throug pores and into the interstitial space across a semi-permeable from high to low p
Pressure exerted by blood will become lower from the arterial to the venous end
Oncotic pressure
Presence of non-permeating solutes exert on oncotic pressure
Created predominanty by proteins
Draws water from areas of low solute concentration to high
Starling’s forces
Hydrostatic p pushes water out, while oncots pulls it back
Difference between the measures of pressure decides whether water leaves the capillary or not
Renal hydrostatic pressure
Glomerular capillary
Bowman’s capsule
G: favours filtration from glomerulus, ghier than normal BP as resistance in efferent arterial creates built up pressure 60 mmHg
B: opposes filtration from glomerulus 60mmHg
Renal oncotic pressure
Glomerular
Bowman’s
G: opposes filtration
Presence of proteins in the plasma draws fluid back to glomerulus
B: very little osmotic force normally as proteins are not normally present in filtrate
Glomerular filtration rate
- Volume of plasma filtered through both kidneys per unit of time
- GFR in an average is 125ml/min
99% filtrate is reabsorbed by renal tubules
GFR determined by
- net glomerular filtration pressure
- permeability of filtration barrier
- sufrace are available for filtration
Filtered load
Quantity of a particular solute that is filtered per unit time
