Kidney and renal function Flashcards
The kidneys and urinary tract have a critical role in which four areas?
Excretion and elimination of waste products
Homeostasis
BP regulation
Endocrine function
What are the two main functions of the urinary system?
Excretion - removal of organic waste products
Elimination - Discharge of waste products into environment
What are the three broad functions of the kidney?
Homestasis
Excretion
Regulation
What does homeostasis help regulate in the kidneys?
Water and electrolyte balance
Acid-base balance
What is excreted from the kidneys?
Drugs and their metabolites
Endogenous waste products
The kidneys regulate and produce which hormones?
Erythropoietin
Renin
Prostaglandins
Active vit D
What vertebral level are the kidneys located at?
T12 to L3
What vertebral level is the renal hilum located at?
L2
What is renal agenesis?
born with one kidney
1 in 1000/2000 people
What are the two main layers of the kidney?
Cortex
Medulla
What is the cortex of the kidney and what does it contain?
Outer region
Glomerulus and convoluted tubules
What is the medulla of the kidney and what does it consist of?
Inner region
Pyramid-like structures
Consists of the bulk of the nephron structure
What is the nephron?
functional unit of the kidney
What is the nephron responsible for?
Urine formation/composition
During the early stages of CKD, the kidney can lose up to 50% of what?
Nephrons
What are the five distinct sections of the nephron?
Glomerulus Proximal Convoluted tubule Loop of Henle - descending and ascending limb Distal convoluted tubule Collecting duct
What capsule contains the glomerulus?
Bowman’s capsule
Where does filtration happen in the kidney?
Glomerulus
Where does selective reabsorption happen in the nephron?
Proximal tubule
Distal tubule
Where does osmoregulation happen in the nephron?
Loop of henle - salt gradient
Collecting duct - water retention
What are the two types of nephrons?
Cortical
Juxtaglomerular
Tubular fluid travels through the collecting ducts deep into what structure?
Inner medulla of kidney
The tubular fluid that exits the collecting duct at the tip of the renal pyramid enters what?
Renal papilla
Why is the renal papilla clinically important?
common site of drug induced nephrotoxicity
Can lead to renal papillary necrosis
Which is the most abundant nephron?
cortical - 70-80%
Where are cortical and juxtaglomerular nephrons located?
cortical - In the cortex
Juxtaglomerular - In cortex but closer to medulla
What is the structural difference between cortical and juxtaglomerular nephrons?
Cortical - short loop of henle into medulla. Small glomerulus
Juxtaglomerular - Loop of henle extends deep into renal pyramids. Large glomerulus and vasa recta.
What is the juxtaglomerular apparatus and what does it secrete?
Specialised region associated with the nephron but separate from it.
Secretes renin from macula densa within JGA
Where is the juxtaglomerular apparatus located?
Between thick ascending limb and afferent arteriole
What are the three components to the juxtaglomerular apparatus?
Macula densa
Juxtaglomerular cells
Extraglomerular mesangial cells
What are the main glomerular diseases?
Diabetic nephropathy
Glomerulonephritis
IgA Nephropathy
What are the main renal tubular diseases?
Acute tubular necrosis
Glomerulonephritis
IgA Nephropathy
What is the blood supply to the kidney?
Blood from renal artery
Into afferent arteriole to glomerulus
Exit through efferent arterioles into peritubular capillaries wrapped around tubules
Peritubular capillaries form vasa recta
Blood leaves through venues into renal vein
The kidneys receive what percentage of cardiac output?
20-25%
90% of blood in the kidneys supplies what?
The renal cortex
Why does the majority of blood in the kidneys supply the renal cortex?
To maintain high active tubular cells.
Required for energy-consuming transport processes
What is the major function of the cortical nephrons?
Regulate and excrete
What is the major function of the juxtaglomerular nephrons?
Concentrate or dilute urine
How does the sympathetic nervous system innervate the kidneys?
From the sympathetic chain and fibres from coeliac ganglion
What parts of the kidneys are innervated by the coeliac ganglion and what does this cause?
Arteries - afferent and efferent arterioles and granular cells
Reduces blood supply during fight or flight
What can the sympathetic supply to the kidneys be associated with?
HTN
How does the parasympathetic nervous system innervate the kidneys?
Efferent supply from vagus
ganglion located in hilum
What does the vagus nerve control in the kidneys?
Tone of efferent arterioles
Modifies GFR and renal blood flow
Where is erythropoietin and prostaglandin produced within the kidneys?
Interstitium surrounding glomerulus
what is the glomerular filtration barrier?
4 physical barriers ultra filtrate has to go through before it can enter lumen of bowman capsule
What are the four barriers in the glomerular filtration barrier?
Glycocalyx
Capillary endothelium
Glomerular basement membrane
Podocyte foot processes
What is glomerular filtration dependent on?
Blood pressure
Renal blood flow
For glomerular filtration, the filtrate has to pass through what?
Pores in glomerular capillary endothelium
BM of Bowman’s capsule (+ contractile mesangial cells)
Epithelial cells of Bowman’s capsule (Podocytes) via filtration slits in capsular space
How does filtrate pass through podocytes?
Through filtration slits
Can proteins pass through the glomerular barrier?
No
Where are mesangial cells located?
Centre of glomerulus
What is the role of mesangial cells?
Phagocytic - clear Ag/Ab complexes
Contract due to AT II and ADH -> reduces GFR by reducing filtration surface
What is the initial step in urine formation?
Glomerular filtration
Examples of small molecules <60 KDa filtered through the glomerulus?
Electrolytes Amino acids Glucose Metabolic waste Some drugs + metabolites
Examples of molecules that cannot be filtered through glomerulus and remain in the blood?
Cells and large molecules RBC Lipids Proteins Most drugs + metabolites
What is the basic structure of a nephron?
Glomerulus Proximal convoluted tubule Loop of henle Distal convoluted tubule Collecting duct
What is ultrafiltration?
Solution moves via a pressure gradient
What is the approx glomerular filtration rate?
125ml/min = 180L/day
Does GFR change with blood pressure?
No remains constant due to autoregulation of renal blood flow
What metabolite is affected first in AKI?
Creatinine
Which marker would you use in CKD as an indicator for renal function?
GFR
What are the three major functions of the nephron?
Filtration - of blood to produce filtrate
Reabsorption from filtrate
Secretion - of waste products into tubular fluid
What is transcellular transport?
Passive or active transport through channels
Many passive secondary to active transport
What is paracellular transport?
Movement driven by concentration, osmotic or electrical gradients
Through tight junctions between cells
Some endogenous substances and drugs cannot be filtered into glomerulus due to size/protein binding. How do these substances get into the nephron?
Pumps in proximal convoluted tubule transports from plasma into nephron
What are the two types of pumps in the proximal convoluted tubule for?
Organic acids or drugs (uric acid, diuretics, abx)
Organic bases or drugs (creatinine, procainamide)
Where is the majority of water reabsorbed in the nephron?
Proximal convoluted tubule
How is H20 reabsorbed into the tubules?
Passively along osmotic gradient created by solute (Na+)
Reuptake via aquaporins
What % in total of electrolytes, H2O and nutrients are reabsorbed by the renal tubules?
99%
What is the Glomerular Filtration Rate?
Rate the glomerulus filters per minute
What is osmosis?
Movement of water by concentration gradient
What is diffusion?
Movement of solute by concentration gradient
What do epithelial cells in the glomerular basement membrane of the glomerular filtration barrier secrete?
Collagen
Glycoproteins
What type of capillaries in the glomerulus helps facilitate filtration? (Continuous, fenestrated, or sinusoidal)
Fenestrated
How many loops are in the glomerulus?
40
What arteriole runs alongside the juxtaglomerular nephron to accommodate the longer loop of henle and supplies blood to the medulla?
Vasa recta
What is the main blood supply to the kidneys?
Renal artery
What problems can a reduced kidney function cause?
Anaemia - Reduced erythropoietin
Hypotension - reduced renin
Bone loss/fragility - Reduced Vit D
Toxin accumulation - uraemia
