Lecture 16 - Introduction to the Kidney Flashcards
What % of blood flow does the kidney receive?
25%
Why does the kidney recieve a lot of blood?
Due to their important role in homeostasis - the kidney has regulation of composition and volume of body fluids.
How does the kidney control the composition and volume of bodily fluids?
They do this by filtering the blood and controlling what substances (including water) are excreted from the body.
What are the overall functions of the kidney? (5)
- Regulation of water and ion balance (body pH
- Excretion of metabolic wastes
- Excretion of foreign chemicals
- Endocrine functions (calcitriol, EPO, renin)
- Gluconeogenesis
How are toxins and (most) drugs removed by the body?
In the kidney by target proteins along the nephron.
How much plasma does the kidney filter per day?
180 L
What percentage of filtrate is reabsorbed?
99%
What is the basic anatomy of the kidney?
Cortex
Medulla
Pyramid
Capsule
Pelvis
What are the pyramids in the kidney?
Medullar pyramids - accumulated areas of nephrons
What is the blood supply of the kidney?
The kidney is supplied by the renal arteries
How does the renal artery divide in the kidney?
The renal artery divides to form small capillary structures which lead to the formation of the glomerulus capillaries, peritubular capillaries and vasa recta, which all surround the nephron
Which of the following statements is true?
A. The kidney filters about 200 litres of plasma per day.
B. The kidneys do not produce hormones.
C. The Urinary system has three ureters.
D. The kidneys excrete foreign chemicals.
D. The kidneys excrete foreign chemicals.
What is the nephron?
The smallest functional unit of the kidney
What are the two types of nephron?
Nephrons can either be superficial (cortical) or juxtamedullary
Where do the juxtamedullary nephrons expand?
The cortex and the medulla
Where do the superficial (cortical) nephrons expand?
Contained in the cortex
What are the components of the nephron? (7)
The nephron consists of the glomerulus, bowman’s capsule, proximal tubule, loop of Henle, distal tubule, and collecting duct.
Where is glucose reabsorbed in the nephron?
The proximal tubule
What are the two ways in which material can move from the blood to the lumen of the nephron?
Glomerular filtration or tubular secretion
Which of the following statements is false?
A. The Nephron is the smallest functional unit of the kidney.
B. The afferent arteriole branches to make the glomerulus.
C. Each kidney contains more that 1 million nephrons.
D. Reabsorption of material is from the blood to the lumen of the nephron.
Reabsorption of material is from the blood to the lumen of the nephron - filtration of blood occurs at nephron, not reabsorption
What is Glomerular Filtration (Ultrafiltration)?
The bulk flow of protein-free plasma into the Bowman’s space which forms the filtrate
What is filtrate composed of?
The filtrate contains everything in plasma except RBC and proteins
What are the structures of the Renal Corpuscle
Glomerulus (capillaries)
Bowman’s capsule - outer epithelium
(Podocytes - inner epithelium)
What is the glomerulus made up of?
Endothelium (capillary tuft) fenestrated with basement membrane - for sieve action
Describe the podocytes
Specialised epithelial cells of Bowman’s capsule. Podocytes have finger like structures (pedicels) which enhance filtration barrier - Filters small things
What is the filtration system composed of?
Macula densa (MD)
Granular cells (G)
Pedicels - Podocyte foot processes (FP)
Podocyte (P)
Endothelium (EN)
Basement membrane (BM)
What are the macula densa?
Series of cells in thick ascending limb which monitors the level of sodium - osmotically involved
What are the granular cells?
Cells the produce renin
Why is renin important?
For Na+/water balance
What forms the filtration barrier?
Together the endothelial cells of the glomerular capillaries, the basement membrane and the podocytes form the filtration barrier
What is the fenestrated endothelium permeable to?
Freely permeable to water, ions, and small solutes but not cells
What is the basement membrane in the filtration barrier?
Matrix of negatively charged proteins which acts as a charged-based filtration barrier to proteins
What is nephrotic syndrome?
The break down of the filtration barrier so we have less filtration and increase protein excretion - Inability to concentrate urine, low plasma proteins can lead to oedema
Which of the following statements is false?
A. The renal corpusle contains the glomerulus and the Bowman’s capsule.
B. Podocytes do not aid with filtration.
C. The basement membrane is negatively charged to assist filtration.
D. Jonah Lomu died from nephrotic syndrome.
B. Podocytes do not aid with filtration.
What are the pressures (forces) that make up the Glomerular Ultrafiltration Pressures?
Pressure Favouring filtration:
Glomerular capillary hydrostatic pressure (PGC) - Blood pressure
Pressures Opposing filtration:
Hydrostatic pressure – Bowman’s space (PBS)
Oncotic pressure due to proteins in the glomerular capillary (πGC)
What is the equation for the net glomerular ultrafiltration pressure?
(PUF) = PGC - PBS - πGC
What is Glomerular capillary hydrostatic pressure (PGC)?
Pressure that pushes fluid from the lumen into bowman’s capsule (high pressure in glomerular capillary wants to move fluid out)
What is Hydrostatic pressure – Bowman’s space (PBS)?
Pressure that opposes the movement of water from blood to LS (Bowman’s space pressure wants to move fluid out)
What is πGC?
Osmotic pressure (opposing filtration due to proteins in the glomerular capillary)
