Renal system Flashcards
How is the kidney protected?
through it’s tough fibrous capsule
why is the renal cortex granular?
due to glomeruli filters and convoluted tubules and blood vessels
what are the functional units of the kidney?
nephrons
what is the outer portion of kidney lobes made up of? what is the inner portion?
outer is cortex inner is medulla
what does the nephron consist of?
the renal corpuscle, tubular component and vascular component
what is the nephron responsible for?
filtration, reasbsorption, secretion and excretion
what makes up the vascular component of the nephron?
-afferent arteriole
-glomerulus
-efferent arteriole
-peritubular capillaries
what does the afferent arteriole do?
carries oxygenated blood to the glomerulus
what does the glomerulus do?
filters large protein free plasma to the tubular componentw
what does the efferent arteriole do?
carries deoxygenated blood out from the glomerulus
what do the peritubular capillaries do?
supply renal tissue and are involved in exchanges with the fluid in the tubular lumen
what is the renal corpuscle of the nephron?
a compact mass of looped fenestrated capillaries being the glomerulus that is encapsulated by the proximal end of the renal tubule at the bowman’s capsule
what does the tubular component of the nephron consist of?
-bowman’s capsule
-promximal convoluted tuble
-loop of henle
-distal tuble, collecting tubule and collecting duct
what does the bowman’s capsule do?
collects the glomerular filtrate
what does the proximal convoluted tuble do?
reabsorbs water and solutes by passive and active transport and endocytosis of proteins
what does the loop of henle do?
establishes an osmotic gradient in the renal medulla, reabsorption of water and ions
what do the distal tubule, collecting tubule and collecting duct do?
can reabsorb na+ and h2o and secrete K+ and H+ so regulate water content
where does filtration of the blood plasma take place?
takes place in the renal corpuscle
where is the renal corpuscle found?
in the renal cortex
Q
Give the broad sequence of events in the kidney
A
- Ultrafiltration in the glomerulus
- Selective reabsorption in the proximal convoluted tuble
- Loop of henle maintains a sodium ion concentration gradient so water can be reabsorbed into the blood comcentrating the urine
- Water moves out of the distal convuluted tuble and into the collecting duct to return it back to the blood and the collecting duct carries the remaining liquid being urine to the ureter
give the steps to ultrafiltration
- There is a high hydrostatic pressure in the glomerulus
- This is because the efferent arteriole is narrower than the incoming afferent arteriole so have higher blood presure
- Water solutes pass out through the tiny endothelial pores
- Pass through a basement membrane which is a molecular filter
- Pass through the slits in the podocytes which prevent the capillary bursting as they grip it
- This forms a filtrate in the renal capsule
Give the steps to selective re absorption
- Na+ is actively transported out if the proximal convoluted tuble into the blood capillary (pct) by the active transport so ATP driven exchange pump
- This lowers the na+ conc in the pct so there is a higher concentration of na+ in the glomerular filtrate
3, the na+ diffuses down the concentration gradient from the filtrate into the pct via co transporter protein bringing in glucose with it - Glucose diffuses down the concentration gradient out of the the pct into the blood capillary via carrier protein in facilitated diffusion
- Water diffuses down the concentration gradient into the pct and into the blood capillary via osmosis
- Very dilute urine remains in the glomerular filtrate
why does RBP4 need to be bound to transthyretin?
because it is too small and glomerular filtration is a passive mechanism and transthyretin is larger and the transthyretin also binds to thyroxine
what percentage of blood plasma that enters the glomerulus in filtered into the bowman’s capsule?
20%
what is transepithelial transport?
where molecules must pass through the cells to leave the tubular lumin into the blood
what does blood plasma contain and in what percentages
-91.5% water
-7% proteins
-1.5% other solutes including NaCl, Na+, K+, Cl- and Ca2+, nutrients like glucose and amino acids and waste products like urea and creatinine
what are the two types of tubular reabsorption?
passive and active
what substances are actively reabsorbed?
-glucose
-amino acids
-other organic nutrients
-Na+
-other electrolytes such as PO43-
how does the brain respond to hyperosmolarity of the blood?
the hypothalamus secretes the antidiuretic hormone (ADH) of vasopressin into the blood at the axon terminals in the posterior pituitary
Give the steps of osmoregulation when the water potential is below the set point
- Stimulus is the water potential of the blood plasma being to low in dehydratiom
- osmoreceptors in the hypothalamus shrink due to the dehydration triggering the response
- Response being polypeptide hormone ADH (being vasopressin) is secreted from the posterior pituitary and directly diffuses into the blood capillary
- vasopressin binds to it’s protien receptors being V2 in the plasma membrane lining the collecting duct
- The tertiary structure of the protein receptors changes shape to activate specific phosphorylase enzyme
- Phosphorylase enzyme creates vesicles which fuse with the plasma membranes to form aquaporins increasing membrane permeability to water so water diffuses out by osmosis
- This means more water in the blood is retained so less is lost in urine
What are the steps of osmoregulation when water is above the set point?
- The stimulus is that the water potential of the blood plasma is too high
- Osmoreceptors in the hypothalamus swell and so trigger the response of the posterior pituitary secreting less of the polypeptide hormone ADH (being vasopressin)
- There is less vasopressin to bind to the protein receptors of V2 in the plasma membrane lining the collecting duct so less phosphorylase enzyme is activated and less vesicles fuse with the membrane so less aquaporins are inserted making the membrane less permeable to water
- This means the urine has a higher water potential as its more dilute and so more water leaves the body
where in the eye are aquaporins abundant?
-erythrocytes
-crystalline lens fibres and epithelium
-corneal endothelium
-trabecular meshwork
-ciliary body epithelium
-conjunctival epithelium
-retinal pigment epithelium
-lacrimal gland epithelium
what are the most important substances secreted by peritubular capillaries to the tubles?
-H+ for acid base balance
-K+ for nerve and muscle excitability
-organic compounds many of which are foreign to the body
what are the renal systems main functions in terms of hormones?
-to secrete renin a hormone which triggers a chain reaction important in the process of salt conservation by the kidneys
-to secrete erythropoietin a hormone that stimulates red blood cell production
-to covert vitamin D into it’s active form from calcidiol to calcitriol which is a hormone that regulates the calcium and phosphate ion
