Renal Flashcards
1 - Describe the structure of the kidney and define its main roles in the body 2 - Describe the structure and function of the nephron 3- Explain the roles and mechanisms of the kidney in maintaining fluid, electrolyte and acid/base homeostasis 4- Discuss the role of the kidney as an endocrine organ
What are the three layers of kidney tissue?
Renal capsule – deep layer, maintains kidney shape
Adipose capsule – a mass of fatty tissue that protects the kidney from trauma and holds it in place
Renal fascia – superficial layer – the thin layer of connective tissue that anchors kidney to surrounding structures and abdominal wall
What are the three sections of the internal kidney anatomy?
Renal cortex – superficial
Renal medulla – inner region
Renal lobe – renal pyramid
Functions of the kidneys
Regulation of water and electrolytes
Regulate pH of blood
Regulate blood volume
Contribute to regulating blood pressure
Control osmolarity of blood
Act as an endocrine organ (produces hormones)
Contribute to regulating blood glucose level (once the renal threshold is exceeded glucose is excreted in the urine)
Excretes waste and foreign substances (ammonia, urea, creatinine, bilirubin, drugs and toxins)
What artery does the kidneys receive blood from?
Renal artery
How does blood leave the kidneys?
Renal vein
What % of blood goes to the cortex?
99%
What % of blood goes to the medulla?
1%
How many nephrons in each kidney?
Approx 1 million
What are the 2 parts of a nephron? And functions?
Renal corpuscle - Filters blood plasma
Renal tubule - Receives filtered plasma
What does the renal corpuscle consist of?
Glomerulus - capillary network
Glomerular (Bowmans) capsule - double walled cup surrounding glomerulus
What does the renal tubule consist of?
Proximal convoluted tubule
Descending and ascending loop of Henle (nephron loop)
Distal convoluted tubule
What are the 2 types of nephrons?
Cortical nephron
Juxtamedullary nephron
What nephrons do we have more of?
Cortical nephron - 80-85%
Compare and contrast cortical nephrons and juxtamedullary nephrons
Cortical - 80-85% of nephrons in the kidney
Juxtamedullary - 15-20% of nephrons in the kidney
Cortical - short loop of Henle
Juxtamedullary - long loop of Henle
Cortical - loop of Henle penetrate only outer renal medulla
Juxtamedullary - Loop of Henle penetrate deep into the renal medulla
Cortical - Small glomeruli
Juxtamedullary - Large glomeruli
Cortical - Low glomerular filtration rate
Juxtamedullary - High glomerular filtration rate
Cortical - Perform excretory and regulatory function of the kidney
Juxtamedullary - Involved in concentrating or diluting urea
Cortical - no vasa recta network, only peritubular to receive blood
Juxtamedullary - Large network of vasa recta, and peritubular
Cortical - Ascending limb of loop of Henle straight
Juxtamedullary - Ascending limb had thick and thin regions
What does the renal corpuscle consist of?
Bowman capsule and a glomerulus (cluster of capillaries)
What % of filtered fluid goes back into the bloodstream?
99%
Name the 2 types of capillary beds, under high or low pressure?
Glomerular capillaries - Under high pressure for filtering
Peritubular capillaries - Around tubule at low pressure
What does GFR stand for?
Glomerular filtration rate
3 Steps of urine formation
Simple filtration
Selective and passive reabsorption
Excretion
Describe the glomerular filtration rate
It is the amount of filtration formed in all the renal corpuscle of both kidneys each minute
Watch the video about nephrons
https://www.youtube.com/watch?v=8UVlXX-9x7Q
What are the 3 mechanisms that regulate GFR?
Renal autoregulation
Neural regulation
Hormonal regulation
what is renal autoregulation? And the 2 mechanisms?
Kidney maintain blood flow and GFR by using:
Myogenic mechanism - Stretching triggers contraction of smooth muscle cells in afferent arterioles - which reduces GFR
Tubuloglomerular mechanism - macula densa provides feedback to glomerulus, inhibits release of NO causing afferent arterioles to constrict and decrease GFR
What is neural regulation? And the 2 types of stimulation?
Kidney blood vessels supplied by sympathetic ANS fibers that release norepinephrine causing vasoconstriction
Moderate stimulation – both afferent and efferent arterioles constrict to same degree and GFR decreases
Greater stimulation - constricts afferent arterioles more and GFR drops
What are the 2 hormones of hormal regulation? And what do the do?
Angiotensin II reduces GFR – potent vasoconstrictor of both afferent and efferent arterioles
Atrial natriuretic peptide increases GFR – stretching of atria causes release, increases capillary surface area for filtration
What is used to estimate GFR?
Creatinine
What does the proximal tubule reabsorb and how much?
Reabsorbs 60 % of all solute 100% glucose and amino acids 99% bicarbonate 80-90% inorganic phosphate and water
What is the counter current multiplier mechanism?
Uses energy to generate an osmotic gradient
Enables you to reabsorb water from the tubular fluid and produce concentrated urine
Prevents you from producing litres and litres of dilute urine every day, and is the reason why you don’t need to be continually drinking in order to stay hydrated.
What are the actions of the different parts of the loop of Henle?
Descending - impermeable to solutes but permeable to water. The tubular fluid becomes hypertonic because of water moves out
Thin section of ascending - Almost impermeable to water but permeable to solutes (Na & Cl ions). The tubular fluid becomes hypotonic
The thick section and early distal tubule are virtually impermeable to water, however Na and Cl are actively transported out of the tubule making the tubular fluid hypotonic
Distal tubule and collecting duct permeability depends on the amount of antidiuretic hormone secreted by the posterior lobe of the pituitary
What cells make up the juxtaglomerular apparatus?
Macula densa cells
What do the macula densa cells do?
Detect chloride concentration and modified smooth muscle cells in the walls of the afferent and efferent arteriole
Produce renin
What 3 hormones regulate renal sodium and water reabsorption?
Antidiuretic hormone
Renin-angiotensin-aldosterone system
Atrial natriuretic hormone
Steps of ADH secretion
Increased osmotic pressure due to low water intake
Osmoreceptors in hypothalamus stimulated
Nerve impulses from hypothalamus stimulate posterior pituitary
Posterior pituitary secretes ADH
Water reabsorbed in collecting duct
3 factors that stimulate ADH to be secreted
Increased osmolarity in ECF
Decreased circulating blood volume (detected by cardiovascular receptors)
Decreased arterial blood pressure (detected by cardiovascular baroreceptors)
3 factors that stimulate ADH to be secreted
Increased osmolarity in ECF
Decreased circulating blood volume (detected by cardiovascular receptors)
Decreased arterial blood pressure (detected by cardiovascular baroreceptors)
Actions of ADH
Increases permeability of the collecting duct and distal convoluted tubule
Promotes reabsorption of water so expanding extracellular fluid and reducing the osmolality of the ECF at the same time.
ADH called vassopressin as it also causes a raise in arterial pressure
3 reasons why renin is released from the juxtaglomerular apparatus
Activated by:
Decrease in afferent arteriolar pressure
Reduced plasma sodium concentration or reduced glomerular filtration
Stimulation of renal sympathetic nerves
What is the role of angiotensin II?
Promotes the release of the steroid hormone aldosterone
Stimulates arteriolar vasoconstriction
Promotes ADH release
Promotes drinking
What is the role of aldosterone?
Stimulates reabsorption of sodium from the distal convoluted tubule and collecting ducts
This leads to expansion of ECF and increased blood pressure
Main effect to reduce urine volume
Where is atrial natriuretic hormone release from?
The atria of the heart
What is the role of atrial natriuretic hormone?
It promotes glomerular filtration and inhibits tubular reabsorption of sodium
This leads to increased natriuresis (excretion of sodium) and diuresis (increased urine)
This results in a reduction in both extracellular and fluid volumes.
Where is in the nephron does potassium get absorbed by active transport?
proximal convoluted tubule and the ascending limb of the loop of Henle
What role role aldosterone have on potassium?
stimulates potassium secretion in the distal convoluted tubule
It is this that regulates plasma potassium
What part of the nephron are calcium and phosphate ion reabsorbed and what is the hormone controlling it?
Both are actively reabsorbed from the tubular fluid, particularly in the proximal convoluted tubule
Reabsorption is controlled by the hormone parathyroid hormone which promotes calcium reabsorption whilst inhibiting that of phosphate.
What gland secretes parathyroid hormone and where is it located?
Parathyroid glands located posterior to the thyroid gland
What stimulates the secretion of parathyroid hormone?
Stimulated by a fall in plasma calcium ion concentration
What 3 actions does parathyroid hormone have on the kidney?
Increases calcium absorption from renal tubules
Stimulates urinary phosphate excretion
Stimulates conversion of Vit D to active form so increasing gut absorption of calcium and phosphate
Name 3 ways acid/base balance is achieved?
Chemical buffers
Respiratory regulation
Renal regulation of bicarbonate ion
3 chamical buffer systems in the body?
Systems in body are
Bicarbonate
Phosphate
Protein
What system does respiratory regulation utilise? And what effect does acidosis and alkalosis have on respiritory regulation?
Utilises bicarbonate system
Acidosis activates respiratory system to increase respiratory rate and depth. This eliminates more carbon dioxide causing blood pH to rise.
Alkalosis depresses the respiratory centre causing carbon dioxide to build up and a fall in blood pH
How does the renal regulation of bicarbonate ions counteract acidosis and alkalosis?
To counteract acidosis, more bicarbonate ions are generated and the resulting secreted hydrogen and ammonia ions are excreted in the urine.
To counteract alkalosis, bicarbonate ions are secreted into the filtrate and hydrogen ions are reabsorbed.
Steps of tubular secretion of acid (H+)
The buffer sodium bicarbonate is filtered by the glomerulus and then reabsorbed in the proximal tubule
The sodium is absorbed by a sodium/hydrogen ion pump which exchanges sodium ions for hydrogen ions on the luminal proximal border of the tubular cell
A sodium/potassium pump forces sodium through the cell from the tubular fluid in exchange for potassium.
Where is most of the filtered bicarbonate reabsorbed and what %?
About 90% is reabsorbed in the proximal tubule
