cgier 25 Flashcards
water and na+ undergo – but no —
- reabsortion
- no secretion
the Na+ reapsortion is an — requires all – except —-
- active process
- tubules
- descending limb of loop of henle
water reabsorption is by — and is dependent on —-
- osmosis , passive process
- na+ reabsorption
in primary active sodium reabsorption, the primary active transport of Na — and — the interstitial fluids
- out
- into
in primary active sodium reabsoription the transport is achieved by:
Na+ /K+ - ATPase pumps.
The active transport of Na+ out of the cell keeps the intracellular concentration of Na+ — compared to the tubular lumen so Na moves downhill from —- into —–
- low
- tubular lumen
- tubular epithelial cells
-The movement of Na+ across the apical membrane varies from segment to segment of the tubule.
MECHANISM OF 𝐍𝐚! REABSORPTION IN THE PROXIMAL TUBULE
- cotransport w/organic material as: glucose
- counter transport w/ h+
the main function of the reabsorption in the ascending limb of loops of henle is — and is done by —–
-reabsorption NaCl not water
- Na-K-2Cl cotransporter ( NKCC)
the NKCC is a — in — transport of —- and it depends on —-
- protein
- active
- na, k , chloride into the cell
na+ concentration created by Na/k-atpase pump
The K+ absorbed through the the NKCC from the tubular lumen and is recycled back
potassium channels
where does the event of diffuse through the sodium channels occur
cortical collecting duct
Na!, water, and other molecules absorbed into the interstitial space are now reabsorbed by
bulk flow into the blood
most secretion occurs in – and lesser in —
- distal convoluted tubule
- collecting duct though all parts of the nephrons may secrete small amount
active secretion is the reverse of — and is usually in —
- absorption
- basal channels
Active secretion requires active transport and is usually coupled to the
reabsorption of Na+
the principle secretion are
- k , potassium
- hydrogen
- urate ions
- drugs as penicillin
the level of – is important as the excess in the blood leads to — and eventually —
- potassium
- cardiac arrthmia
- cardiac arrest
Reabsorption and secretion is mainly controlled by these three hormones:
- ADH , anti-dirutic hormones
- Aldosterone
-ANP , artial natriuretic peptide
ADH is secreted in the —- under the control of the —- where the — are sensitive to the na+ levels in the blood
- pituitary glands
- hypothalamus
- osmoreceptor cells
the release of adh leads to
-increases the permeability of the collecting duct and
perhaps the distal tubule to water, so water is removed from the urine
- more water is reabsorbed , more hypertonic urine produced ,
-low urine volume
- High plasma volume
low levels of ADH leads to
- more diluted hypo-osmotic extracellular fluid
- less water absorbed
- more urine produced
- low na levels
— is a steroid hormone which stimulated the na reasobrotion in the —- and the —-
- aldeterson
- distal convoluted tubule
- cortical collecting duct
aldosterone is secreted by
adrenal cortex
low secretion of aldeteron leads to –
high secretion of aldosterone leads to –
- na is nor reabsorbed but is excreted
- na is reabsorbed
Factors that regulate aldosterone secretion:
Renin-angiotensin-aldosterone mechanism * Plasma concentration of K+
* ACTH
* Atrial natriuretic peptide
—-blood pressure stimulated special cells in kidney to produce — and they will convert —- to —-
- decreased
- renin
- angontensigon
- angisten ii
is a potent stimulator of aldosterone release
Angiotensin II
- which leads to vasoconstriction, na and h20 retention and increase of blood pressure )
increase of — directly stimualtes the release of — and low level of it — its
- k+
- aldertrons
imhibits the release of aldosterone
leads to small increase of aldosterone during increased stress
ACTH
secreted by the heart (arterial cardiac wall) in response to high blood pressure
ANP
ANP blocks — and — the blood pressure
- renin
- decreases
acts antagnositly to aldestrone
ANP
the effect of ANP:
Dilates afferent arterioles which increases Glomerular filtration rate – directly inhibiting sodium reabsorption in the collecting ducts
– inhibits the secretion of aldosterone by the adrenal cortex
– Decreases blood volume and pressure
the distal convoluted tube is in close contact with
afferent and efferent arterioles of the glomooirs
— is in the distal tubule are in close contact with cells in the afferent arteriole called the — and the whole structure is called
macula densa cells , juxtaglomerular cells, juxtaglomerular apparatus.
Afferent Arteriolar Vasodilator Feedback Mechanism
- Slow glomerular filtration (e.g. low blood pressure) and consequent over-reabsorption of Cl- ions reduces the Cl- concentration at the macula densa.
- this initiates a signal from the macula densa to the juxtaglomerular cells causing them to dilate.
- this increases blood flow in the glomerulus and thus increases filtration.
- a converse afferent arteriolar vasoconstrictor operates where too great a glomerular blood flow is reduced and consequently glomerular filtration;
B. Efferent Arteriolar Vasoconstrictor Feedback Mechanism
Again a slow glomerular filtration (when blood pressure falls) and consequent over-reabsorption of Cl- ions reduces the Cl- concentration at the macula densa.
* this causes the release of renin from the juxtaglomerular cells into the blood circulation.
* which initiates a cascade reaction from angiotensinogen (renin substrate) producing angiotensin I;
* this is converted to the active form by an enzyme in the lung:
B. Efferent Arteriolar Vasoconstrictor Feedback Mechanism
- angiotensin II has a number of general effects but in the kidneys it particularly constricts the efferent arteriole (Can you remember what its other major function is?).
- this reduces the peritubular blood flow while at the same time increasing the glomerular pressure and thus the filtration rate.
- however at the same time the afferent vasodilator mechanism dilates the afferent arteriole.
- thus the net effect is to maintain a constant glomerular filtration rate despite arterial pressure changes.
- glomerular filtration increases very little despite arterial pressure changes between 75 and 160mm Hg.
—- is a muscular tube about 25cm long, conveying urine from the renal pelvis to the urinary bladder.
uretur
The urinary Calyx, renal pelvis, ureter and bladder all have the same basic histological construction composed of three coats:
-A mucosa, ( is formed of stratified transitional epithelium)
-a muscularis layer and
-outer adventitia
The muscularis layer is unusual with an —- band and outer —- of — muscle
- inner longitudinal
- circular layer or smooth muscle
—- is composed of fibroelastic, loose connective tissue blending into the surrounding tissues
adventia
The urine is produced by the kidney in a continuous trickle and then conveyed to the bladder by
peristaltic waves
— lies posterior to the pubic symphysis in the anterior part of the pelvis
bladder
consist of:
-It has basically a similar construction to the ureter but with a thicker epithelium
- the mucosa layer has a transitional epithelium (6-8 cells) which allows the cells to slide past each other as the bladder fills
- This flexibility allows the bladder to reach a capacity of up to 800ml
the — is distinct from the rest of the extra renal collecting system
-urethra
— is the process of expulsion of urine from the bladder
urination or micturition
The exit of urine from the bladder is controlled by two sphincters:
-An internal urethral sphincter located at the upper end of the urethra
-An external urethral sphincter located at the urogenital diaphragm
-The former is of smooth muscle under autonomic control and the latter striated voluntary muscle
