11.3 the kidney and osmoregulation Flashcards
define excretion
the removal from the body the waste products of metabolism
define homeostasis
stable internal environment of an organism is maintained despite changes in external conditions
define osmoregulation
maintainence of a proper balance of water and dissolved substances in the organism
if water intake is excessive, the _________ _________ that develops stretches the _________ __________ to the point of bursting.
hydrostatic pressure
plasma membrane
osmoconformers maintain the ______ of their cells and body fluids at the _____ concentration as that of the ___________
osmolarity
same concentration
environment
why do osmoconformers maintain the osmolarity of their cells at the same concentration as the environment 2
- no tendency of water uptake/loss from cells and tissues
- less energy is used to maintain internal osmotic conditions
what are osmoregulators
organisms able to regulate solute concentration of bodily fluids INDEPENDENTLY of external conditions
= changes in environment have no effect/small flucturations on internal solute conc
unit of measurement of osmolarity
mOsmdm/3
animals are either osmo_______ or osmo_________
osmoregulators or osmoconformers
how is osmolarity maintained in humans 3
- regulation of the balance of dissolved substances and water in body fluids: conc of inorganic ions, sugars, amino acids, water content
- osmolarity of these maintained at same level as cell cytoplasm
- kidneys: excess solutes and water removed
describe the role of kidneys
to regulate the bodys internal environment by constantly regulating the composition of blood
- conc of inorganic ions and water maintained
- waste products of metabolism removed from blood, excereted as urine
each kidney is served by a _____ artery and drained by a _____ vein
renal !
what structure filters the blood and produces urine!
nephrons
imgaine a diagram of the human kidney + 6 required labels
- cortex not more than 20% of width
- medulla pyramids point towards pelvis
- renal artery = narrow, vein = broad
- required labels: cortex, medulla, pelvis, ureter, renal artery and vein 6
blood in the renal vein will have: (blood composition) 5
- less urea
- less water and solutes/ions
- less glucose (/same) (used for metabolic processes)
- less oxygen (used for metabolic processes)
- more co2
6 important components of the nephron
- bowman’s capsule
- proximal convoluted tubule
- loop of henle
- distal convoluted tubule
- collecting duct
- glomerulus (blood vessel)
4 types of blood vessels in the nephron
- afferent arteriole
- glomerulus
- efferent arteriole
- capillary bed
function of the bowman’s capsule
highly porous wall which collects the filtrate
function of the glomerulus
knot-like capillary bed where high pressure filtration takes place
function of proximal convoluted tubule
water, nutrients. and salts reabsorbed back into blood
- contains many mitochondria and microvilli
function of loop of henle
has a descending and ascending limb
- water and salt reabsorption takes place
function of distal convoluted tubule
water and salts reabsorbed back into the blood
- contains many mitochondria and microvilli
function of collecting duct
tube that carries the filtrate to the renal pelvis
function of afferent arteriole
brings blood from renal artery to nephron
function of efferent arteriole
narrow blood vessel – restricts blood flow, generating pressure needed for filtration
function of vasa recta
unbranched, shaped like loop of henle
descending limb brings blood deep into medulla
5 basic steps in the formation of urine
- ultrafiltration in the renal capsule
- selective reabsorption in the proximal convoluted tubule
- water conservation in the loop of Henle
- blood pH and ion conc regulation in distal convoluted tubule
- water reabsorption in the collecting ducts
describe the process of ultrafiltration in the renal capsule 3
- glomerulus: water and useful molecules + urea forced into capsule lumen
- powered by the pressure of the blood (Afferent wider than efferent)
- basement membrane = filter
describe the barrier between the blood plasma and lumen of the bowmans capsule – what are the 2. layers of cells + extra thing
- endothelium of the capillaries of the glomerulus
- epithelium of capsule wall
+ basement membrane between
what are podocytes
cells of the inner wall of the bowmans capsule
- wrap around glomerulus
- leaves a network of slits between extensions
endothelium of the capillaries in the glomerulus has ____
PORES
- lets fluid thru but not rbcs
what is the basement membrane
layer that surrounds and supports capillary walls
- mesh of glycoproteins
- allows filtrate to pass
- retains almost all plasma proteins
whats the difference between filtrate and blood plasma
filtrate does not contain proteins
which structure is the longest section of the nephron
proximal convoluted tubule
what occurs during selective reabsorption
- large part of filtrate reabsorbed
- active transport is a key mechanism
structure of walls of proximal convoluted tubule 3
- one cell thick
- many mitochondria (for active transprot)
- cell membranes all have microvilli (incr surface area)
how are sugars and amino acids in the filtrate reabsorbed
active transport
- thru co-transport, by action of special carrier proteins (sugars)
how are ions in the filtrate reabsorbed
combination of active transport, facilitated diffusion and some exchange of ions
through what mechanism is urea in the filtrate reabsorbed
diffusion
explain the mechanism of active transport in selective reabsorption in the proximal convoluted tubule 3
- pumps use ATP for active transport: Na out, K in, Cl attracted to tubule exterior
- glucose and AA reabsorbed — by specific carrier proteins down a conc gradient (powered by transport of Na into blood, hence called secondary AT)
- glucose and AA conc in proximal ct incr = higher than blood plasma = diffusion
how does the structure of the proximal convoluted tubule incr rate of diffusion
microvilli in the wall cells = incr surface area
by the end of the proximal convoluted tubule, approx ____% of water, glucose, and mineral ions are reabsorbed
80%
during active transport in the proximal convoluted tubule, what substances are pumped out + what substance during secondary active transport
at: sodium ions
secondary at: glucose
describe the process of co-transport 2
facilitates movement of sugars during reabsorption in PCT
- carrier protein uses diffusion of H+ ions down their electrical gradient (into cell)
- drives molecule uptake as H+ flow down gradient via co-transporter pump
what is the function of loop of Henle
to enable the kidneys to conserve water
strcutre of loop of Henle 3
descending and ascending limbs + vasa recta (blood supply)
the loops of henle and their capillary loops create and maintain an _______ gradient in the _______ of the kidney
osmotic
medulla
what is the concentration gradient of the salt solution across the medulla
- less conc: near cortex
- most conc: tips of medulla pyramid
what does the pyramid region of the medulla consist mostly of
collecting ducts
the loop of henle maintains _____tonic conditions around the collecting ducts
hypertonic
what does the osmotic gradient in the loop of henle + collecting ducts allow for
allows water to be drawn from collecting ducts when required
what is counter current exchange
involves exchange between fluids flowing in opposite directions in 2 systems
loop of Henle: which parts of the ascending limb are thick and which are thin
upper part = thick walled
lower part = thin walled
what happens in the upper (thick) part of the ascending limb of the loop of henle
Na, Cl ions pumped out of filtrate into fluid between cells of medulla (interstitial fluid)
- energy to pump: from ATP
what is interstitial fluid
fluid between the cells of the medulla
what happens in lower (thin walled) parts of the ascending limb of the loop of henle
Na and Cl diffuse out into interstitial fluid
- movement out helps maintain osmolarity of interstitial fluid
the ascending limb of the loop of henle is _____ to water
impermeable
- water is hence retained in filtrate as salt is pumped out
unusual thing about the ascending limb of the loop of henle?
the walls are impermeable to water
- water is retained in filtrate as salt is pumped out
characteristics of the descending limb of the loop of henle
- fully permeable to water
- very low permeability to solutes
- water passes into interstitial fluid by osmosis
at each level in the loop, the salt conc in the descending limb is _____ than the adjacent ascending limb
slightly higher
the fluid in and around the hairpin being of the loops of Henle is the ____ _________ / _______
most concentrated / saltiest
what is the purpose of the vasa recta 2
- delivers o2 to and remove co2 from metabolically active cells of loop of henle
- absorbs water that passed into the medulla at the collecting ducts
incr need of water = _________ loop of henle
longer
= thicker medulla!
what occurs in the distal convoluted tubule
blood ph and ion conc regulation
how is K+ ion concentration adjusted in the distal convoluted tubule
secretion of excess in the plasma into filtrate
how is Na+ ion concentration adjusted in the distal convoluted tubule
varying the amt of NaCl that is reabsorbed from the filtrate
what is the main purpose of the collecting ducts
water reabsorption
what is the hypothalamus’s role in osmoregulation
- monitors composition of the blood as it circulates thru hypothalamus
- receives info from sensory receptors located in the body
- hence controls activity of pituitary gland
what is the role of the posterior pituitary gland in osmoregulation
- below and connected to hypothalamus
- stores and releases antidiuretic hormone (ADH)
what does ADH stand for
antidiuretic hormone
where is ADH produced, stored, and released
prod: hypothalamus
stored: posterior pituitary gland (vesicles at the ends of neurosecretory cells)
released: posterior pituitary gland
where is the target of ADH
the walls of the collecting ducts of the kidney tubules
when is ADH secreted
when the water content of the blood is low
what do the cells of the collecting duct walls contain that make them succeptible to ADH
cell surface membranes have high proportion of channel proteins
how does ADH change permeability of the walls of collecting ducts 4
- cell surface membranes have high no. of channel proteins
- excess ADH binds to receptor molecules in the collecting duct membrane = protein channels in membranes OPEN
- water diffues into medulla, is reabsorbed and redistributed via circulation
- small amt of conc urine forms
possible causes of kidney failure 3
- bacterial infection
- external mechanical damage
- high blood pressure
consequence of kidney failure (short)
urea, water, Na ions start to accumulate in blood
what are samples of urine tested for 3
- abnormal components eg blood cells, proteins
- drugs (anti-doping investigations)
- glucose (suspected diabetes)
how is kidney failure treated 3
- mild = diet regulation
- > 50% function lost = haemodialysis per few days + diet
- donor: requires compatible cell type
how does kidney transplant work out
- donor requires sufiently compatible cell type
- transplantation: antibody producing cells supressed
- drugs that supress response to foreign proteins have to be administered permanently
how does kidney dialysis work
- blood connected to dialysis machine, repeatedly circulated for 6-10h thru partially permeable membrane
- bathed in dialysate (sol. equal solute pot. and comp. to that of blood from healthy kidney)
- prevents net outward diffusion of useful components + allows diffusion of urea and other toxic substances
what is dialysate
fluid of equal solute potential and similar composition to blood leaving healthy kidney
what is the point of dialysate being similar to blood leaving healthy kidney
- prevents net outward diffusion of useful components
- allows diffusion of urea, other toxic substances OUT
define overhydration and dehydration
excessive intake of water
use/lose more fluid than taken in = body not enough water to carry out normal functions
consequences of overhydration
swelling of body cells
- in brain – intracranial pressure = dysfunction in CNS
- normal balance of electrolytes exceeds safe limits (too low) = death
consequence of dysfunction in CNS as a result of swelling body cells bc of overhydration 4
- seizures, coma, death
- nausea, vomiting
- changes in mental state
- muscle cramps, weakness
consequences of dehydration 7
- electrolyte imbalance
- darker urine
- less elastic skin
- incr heart and breathing rate
- blood pressure decr
- affect ability to sweat
- (severe) brain damage, death
testing for drug abuse: test kits using _________ _________ techniques are used
monoclonal antibody
what does the kidney function / diabetes test for
tests for presence of cells + range of compounds
what do the results of the urine test mean 3
- too much glucose = diabetes
- blood or leucocytes = infection/ kidney tumour
- too much protein = failing ultrafiltration (advanced hypertension)
what is urea and what is it for
a chemical compound synthesized from co2 and ammonia
removal of amino grps from body as a less dangerous nitrogenous excretory product
the insects body has ____ blood circulation
open
what does open blood circulation in insects mean for their circulation
blood does not circulate in discrete blood vessels
insects cells form ____ ____ as the nitrogenous excretory material
uric acid
where is uric acid removed in insects
malpighian tubes
how is water loss reduced from an insects body
- waxy cuticle over external surface of exoskeleton
- tracheae pipe oxygen to body tissues, /w openings (spiracles): valves control movement of gases + reduce water loss
what happens at the upper malpighian tubule
- secretes potassium urate into the tubule lumen
- co2 and water diffuse in
what happens at the lower malpighian tubule
- contents react = form uric acid +potassium hydrogencarbonate + water
- uric acid passes to gut, others back into blood
what happens in an insects rectum
- water withdrawn from faeces
- uric acid becomes solid pellets (leave body w faeces)
mammals adapted to drier habitats have ____ loop of henle lengths and _______ medulla region
LONGER. THICKER!!!!!!
three common products of nitrogenous excretion in animals + their differences
ammonia, urea, uric acid
diff: amt of water required for safe disposal of each is diff – ammonia > urea > uric acid
route of nitrogenous wastes in insects 4
hemolymph –> malpighian tubule –> hindgut –> rectum
