Intro to Kidney Flashcards
What are the functions of the kidney?
1) Regulate body fluid volume
2) Regulate body fluid composition
3) Excrete metabolic waste and toxins
4) Endocrine functions
Key processes are filtration, reabsorption and secretion to eventually form urine which is excreted.
What is a uriniferous tubule?
Uriniferous tubule = nephron + collecting duct
Many nephrons drain into the same collecting duct
What is a nephron?
Nephron is a functional unit of kidney
Nephron = renal corpuscle + proximal convoluted tubule (PT) + Loop of Henle + distal convoluted tubule (DT)
~1 million per kidney
Many nephrons drain into the same collecting duct
What is the cortex made up of?
Mostly renal corpuscles, PT and DT
What is the medulla made up of?
Mostly loops of Henle and collecting ducts
What are the 2 different types of nephrons?
Cortical (~80%) or juxtamedullary (~20%) depending on position of renal corpuscle
What is the renal corpuscle made up of?
Glomerulus + Bowman’s capsule
Describe the blood supply to the kidneys
Renal artery –> Segmental arteries –> Interlobar arteries –> Arcuate arteries (run along corticomedullary junction) –> Interlobular arteries (give off afferent arterioles to the renal corpuscles)
Describe the two capillary beds that blood to the kidney passes through
1) High pressure glomerular capillaries (filtration)
2) Low pressure peritubular capillaries (reabsorption/secretion)
Describe the two layers of the Bowman’s capsule
Outer layer = parietal layer
Containment -> Simple squamous
Inner layer = visceral layer
Filtration -> Modified simple squamous (podocytes)
What are mesangial cells?
Mesangial cells provide support between the glomerular capillary loops
Why is there an arteriole at either end of glomerular capillary bed?
Allows high pressure for filtration
What is the filtration barrier formed by?
1) Glomerular capillary endothelium (fenestrated)
2) Basement membrane (negative charge)
3) Epithelial cells (podocytes) (interdigitating foot processes and filtration slits)
Limits passage of substances from blood based on their size, charge and shape
What type of filtrate is found in the proximal convoluted tubule?
- Unmodified filtrate
- Majority of water, sodium, chloride, amino acids, glucose reabsorption takes place here
- Secretion of some drugs and waste molecules
What type of cells are found in the proximal convoluted tubule?
Simple cuboidal cells with microvilli forming a ‘brush border’ to increase surface area
Describe the thin descending limb of loop of Henle
Permeable to water - no active reabsorption or secretion of solutes
Simple squamous epithelium
Describe the thin ascending limb of loop of Henle
Impermeable to water.
Essentially no active reabsorption or secretion of solutes
Simple squamous epithelium
Describe the thick ascending limb of loop of Henle
Impermeable to water.
Active reabsorption of sodium and other solutes.
Simple cuboidal cells
Describe the distal convoluted tubule
Divided into early and late parts
Active reabsorption of sodium and other solutes; secretion of potassium and hydrogen ions
Simple cuboidal cells
Variable water permeability depending on precise part of distal tubule and presence of antidiuretic hormone (ADH)
Early distal tubule passes back to the vascular pole of its own renal corpuscle to form part of juxtaglomerular apparatus
What is the purpose of the juxtaglomerular apparatus (JGA)?
Involved in tubuloglomerular feedback and control of blood pressure
What are the three components to the juxtaglomerular apparatus (JGA)?
1) Macula densa - specialised cells within part of early distal tubule that passes next to the vascular pole of its own renal corpuscle
2) Extraglomerular mesangial cells (Lacis cells)
3) Granular or juxtaglomerular cells in afferent artieriole
Describe the medullary collecting duct
Final site for urine processing
Water permeability of this part of nephron under hormonal control by antidiuretic hormone (ADH)
Surrounded by a medullary interstitium with a high concentration of solutes
Key role in regulating degree of urine concentration
Simple columnar cells
How much of the body weight is water?
~60% of body weight
Varies with age, gender and body fat
What are the main cations and anions in Extra Cellular Fluid?
Na+ is main cation
Cl- is main anion
What are the main cations and anions in IntraCellular Fluid?
K+ is main cation
PO4 is main anion
Define osmosis
Osmosis is movement of water across a semi-permeable membrane from an area of low solute concentration to a region of high solute concentration
Define osmoles
Osmoles refers to the number of osmotically active particles in a solution
