Kidney Flashcards
What are the functions of the kidney?
- ) excrete waste products into urine. Excretion of various waste products by metabolism into the urine. These include the nitrogenous wastes urea, from protein catabolism and Uric acid from nucliec acid metabolism
2) homeostasis - regulation of overall fluid balance and regulation of minerals from blood. Reg acid base balance, electrolyte conc, blood pressure, extra cellular fluid volume
3) secretion of hormones
Calcitriol - promotes bone health
Erythropoietin - rbc and bp
What parts of the nephron are in the medulla
Loops of henle and collecting duct
Describe the events that occur at the bowmans capsule
Ultrafiltration occurs between the bowmans capsule and the glomerus. This is the removal of small solutes from the blood into the glomerular filtrate
The capillary walls of the glomerulus are made up of a single layer of endothelium which contains fenestrations which makes it highly permeable (not RBC)
The basement membrane is a negatively charged glycoprotein and stops the removal of proteins into the filtrate
The postcards are cells in the bowmans capsule that wrap around the glomerulus- the foot projections wrap around the capillaries leaving slits between them through which blood is filtered out. They also play an important role in strength
Describe events at proximal tubule
Selective reabsorption occurs at the PCT.
Microvilli increase the surface area for the reabsorption of solutes
Mitochondria present to provide ATP for the reabsorption of solutes by facilitated diffusion via carrier proteins
Short diffusion pathway between the peri tubular capillaries and the tubule
Different types of carrier proteins assist different molecules across the membrane
All glucose and amino acids are reabsorbed
85% sodium
50% urea
This lowers the water potential of the blood and drives about 85% of the water back into the blood by osmosis
Na+ moves into the interstitial fluid so a conc gradient is creased
Organic phosphates / solutes move into the blood
Describe the loop of Henle
Counter current multiplier - aim is to make the medulla salty! Or to make medullary gradient salty for later reabsorption from collecting ducts
Descending limb - highly permeable to water impermeable to solutes
Ascending limb - impermeable to water but permeable to solutes
Active transport of sodium out of lumen followed by cl-
Vasa texts flows in opposite direction to loop of henle- allowed removal of substances
Role of ADH
Water reabsorption in the collecting ducts is regulated by ADH
It increases water permeability of collecting ducts for reabsorption
Increases urea permeability of medullary secretion of collecting duct for reabsorption assisted by conc gradient by h20 absorption
Function of ADH
Short term- insertion of aquaporin 2 into the apical membrane of the collecting duct cells by exocytosis
Long term- ADH increases aquaporin 2 gene expression so more aquaporin 2 channels are synthesised
How does ADH work
Osmolarity of extracelluar fluid
Hypothalamus - osmoreceptors detect and respond
Activity of neurosecretory cells in hypothalamus
Post pituitary - ADH secretion
Kidneys - more aquaporin 2 inserted into the apical membrane of the collecting duct cells by exocytosis
Leads to increased water absorption and decreased water excretion - conservation of body water
Process is NEGATIVE FEEDBACK
Ureter function
Moves urine from the kindeys to the back of the bladder
Pass urine by peristaltic waves in smooth muscle - involuntary
Urine backflow prevented by ureterovesical valves mm
Control over bladder
The bladder is an involuntary
organ that can be voluntarily controlled
All humans are born incontinent
Activation of numerous neurological reflexes learnt in early life to control it
Over 35 reflexes coordinate the activities of the bladder smooth muscle and urethra skeletal and smooth muscle
Micturition reflex - 2 stages
Storage phase
As bladder fills pressure stays low due to highly elastic nature
As pressure increases radius increases
Bladder full - wall tension is detected
Messages sent to the brain (voluntary) or locally (involuntary)
Voiding phase
Voluntary signals relax external sphincter (somatic) autonomic contraction of detrusor muscle
Urethra plays an excitatory role which mains flow until bladder is empty - positive feedback m
Nervous control of the bladder
1) viscerosensory nerves sense detrusor stretch (bladder full)
Either
2) sympathetic - this can wait
3) parasympathetic - need to go now
But
4) somatic innervation of the external sphincter allows voluntary control
How do we learn to control peeing
Skeletal muscle is under voluntary control
Somatic nerve control is not part of the autonomic nervous system and is somatic so it is voluntary
Sympathetic control
This can wait
Detrusor muscle relaxes and internal sphincter contacts
From the lumbar region of spinal cord
Neurotransmitter is noradrenaline and acts on
a1 - inhibition of micturition
b2 - relaxation of wall
The pre ganglionic Neuron is short and post ganglionic is long
Parasympathetic contro
From the sacral region
Urgency / must go
Contracts detrusor muscle and relaxes internal sphincter
M3 receptor - initiation of micturition
Acetylcholine acts on nicotinic and muscarinic receptors
Pre ganglionic neuron is long and post is short
