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Excretory system - Coggle Diagram
Excretory system
Kidney
Outer cortex
Proximal convoluted tubule
Distal convoluted tubule
Inner medulla
Loop of Henle
Collecting duct
Consists of nephrons
Renal corpuscle
Cup-shaped chamber called the
Bowman's capsule
Contains a capillary network called the
glomerulus
(Above is the pathway of the filtered blood)
Renal artery
branches into
afferent arterioles
that brings blood to kidney
Afferent arterioles branches into the glomerulus where blood is filtered
Glomerulus combines back into the
efferent arterioles
where the filtered blood will flow to
Efferent arteriole branches into the
peritubular capillaries
and
vasa recta
1 more item...
Renal tubule (On the right is the pathway of urine/ filtrate)
Extends from the renal corpuscle as the
proximal convoluted tubule
where the
filtrate
will flow to from the lumen of the Bowman's capsule
The filtrate will then flow to the
loop of Henle
, first going through the decreasing loop before going to the ascending loop
This leads to the
distal convoluted tubules
Many distal convoluted tubules are connected to the
collecting duct
Many collecting ducts converge to form the
renal pelvis
Urine will then flow to the
ureter
, then the
bladder
and finally through the
urethra
.
Process of filtering and reabsorption (At the nephron)
Ultrafiltration
Requires a filtration barrier
Fenestrated walls
of the glomerular
endothelium
Prevents filtration of blood cells
Basal lamina
of glomerular capillary
Prevents filtration of large substances
Filtration slits
between pedicels of
podocytes
Prevents filtration of medium sized substances
Podocytes are
epithelial
cells lining the inside of the glomerular capillary
Slit membrane
between pedicels
Allows passage of small molecules like
water, glucose, vitamins, amino acids, ions
(Allows passage of useful substances) and waste products.
Does not allow most plasma proteins, platelets and blood cells.
The afferent arteriole is larger in diameter than the efferent arteriole
This maintains high
hydrostatic pressure
Drives fluid constituent of blood into the
lumen
of the Bowman's capsule
Selective reabsorption
Proximal convoluted tubule is primary site for reabsorption of solutes and water
Has microvilli
Increases surface area for selective reabsorption
Has mitochondria
Able to reabsorb water and solutes back into blood via active transport and cotransport
Proteins, amino acids, all glucose and fructose and ions
are transported into the peritubular capillaries
Loop of Henle where more water and solutes are reabsorbed
Descending limb
Is thin and permeable to water but less to solutes
As filtrate passes through, water is reabsorbed into the ascending vasa recta via osmosis
Ascending limb
Consists of a thick and thin portion that is not permeable to water but is permeable to solutes like ions
Solutes transported into interstitial fluid of the medulla via active transport, cotransport and facilitated diffusion.
Keeps concentration of solutes in the medulla high
The concentrated medulla can draw more water out of the descending limb of the loop of Henle into the vasa recta via osmosis
DCT and collecting duct
Regulates the reabsorption of water via osmosis and reabsorption of solutes
Is regulated via antidiuretic hormones.
Secretion
Help remove waste from the bloodstream into the filtrate in the nephron
Can passively diffuse into the lumen of the nephron like ammonia
Can be actively transported like creatinine and H+.
Secretion of H+ in DCT helps regulate body fluid pH
Homeostatic function of kidney
Blood osmolarity is the total concentration of solutes in the blood plasma
Blood osmolarity ↑ which is detected by osmoreceptors in the hypothalamus
↑ Antidiuretic hormones (ADH) released from posterior pituitary gland
Binds with ADH receptors on surface of collecting duct and triggers a cascade mechanism
↑ number of aquaporins inserted in walls of DCT and collecting duct
↑ their permeability to water and more water is reabsorbed from the filtrate into the blood
Smaller volume of concentrated urine and when blood osmolarity levels return to normal, production of ADH becomes inhibited via negative feedback
Blood osmolarity ↓ which is detected by osmoreceptors in the hypothalamus
↓ Antidiuretic hormones (ADH) released from posterior pituitary gland
3.↓ ADH binds with ADH receptors on surface of collecting duct and triggers a cascade mechanism
↓ number of aquaporins inserted in walls of DCT and collecting duct
↓ their permeability to water and less water is reabsorbed from the filtrate into the blood
Larger volume of dilute urine and when blood osmolarity levels return to normal, production of ADH becomes inhibited via negative feedback
Regulates blood pressure by adjusting volume of water lost in urine
Stabilise blood pH by controlling the loss of H+ and HCO3- ions in urine
Kidney failure and dialysis
Diabetes and high blood pressure are the two main causes of kidney disease
High blood glucose can damage the the nephrons and blood vessels that supply the kidneys with blood
High blood pressure reduces blood flow to the kidney and damages the glomeruli
Haemodialysis
Blood flows is drawn from an artery and pumped through a tube made of a
selectively permeable membrane
The tubing is bathed in
dialysis fluid
Fluid contains the
same concentration of useful substances
(Glucose, amino acids) as the blood and
completely no
waste products
Allows for waste products in the blood to diffuse into the fluid and
prevents net diffusion
of useful substances out of the blood into the fluid
Direction of blood flow is opposite to direction of flow of dialysis fluid, and this is called
countercurrent flow
(
"Adaptation"
)
This maintains the concentration gradient for waste products to continually diffuse out of the blood
The tube is long, narrow and coiled
This increases
surface area to volume ratio
which speeds up the rate of exchange of substances between blood and the dialysis fluid (
"Adaptation"
)