Pathology and Physiology Flashcards
In the bladder, the first urge to void is felt at, and a marked sense of fullness is at ?
150mls and 400mls
What is permeable in the thin descending portion of the loop of Henle?
Highly permeable to H2O and only slightly permeable to NACL
Due to the presence of aquaporin-1 in both the apical and basolateral membrane
What is permeable in the thin ascending portion of the loop of Henle
Not permeable to H2O
Highly permeable to NaCl
What is permeable in the thick ascending portion of the loop of Henle
Not permeable to H2O
Only slightly permeable to NaCl
What is permeable in the collecting tubules of the kidneys?
highly permeable to water in the presence of vasopressin
How is sodium transported in the renal tubule
Actively transported out of all parts of the renal tubule except the thin portions of the loop of Henle
Filtration fraction of Kidney is?
0.16-0.20
Explain the control of the external urethral sphincter
Controlled by the pudendal nerves which are somatic
Contraction of the perineal muscles and external sphincter can be contracted voluntarily, preventing urine from passing down the urethra or interrupting flow once urination has begun
What happens to the kidneys during a fall in systemic blood pressure?
Renal plasma flow decreases more than eGFR
Filtration fraction increases
Both afferent and efferent arterioles are constricted, efferents to a greater degree
Sodium retention is marked
Nitrogenous products of metabolism are retained in the blood giving rise to azotaemia and uraemia
Prolonged can cause renal tubular damage and acute renal failure
Osmolality of the pyramidal papilla
1200mosm/kg
What is the best substance to measure eGFR?
Eg, Inulin
a substance that is freely filtered, niether reabsorbed nor secreted, is nontoxic and not metabolised by the body
Proximal convoluted tubule reabsorbs how much filtered sodium ?
60%
How does sodium move through the nephron?
PCT reabsorbs 60% of filtered sodium
It is pumped back into the interstitium by the Na/K/ATPase
It does share a common carrier with glucose
30% is absorbed via the Na/2Cl/K cotransporter in the thick ascending limb of the loop of Henle
7% via the NaCL contransporter in the DCT
3% via the ENaC channels in the collecting duct
In osmotic diuresis what causes increased urine flow?
Decreased water reabsorption in the PCTs and loop of Henle
Renal acid secretion is altered by?
Changes in the intracellular pCO2
Potassium concentration
Carbonic anhydrase level
adrenocorticol hormone concentration including aldosterone
Describe glucose absorption in the kidneys?
Glucose reabsorption is an active process
Closely associated with sodium
Occurs predominantly in the proximal convoluted tubule
Sodium Glucose Linked Transporters actively reabsorb glucose (SGLT)
excreted in urine if renal threshold is exceeded
Urea in the kidneys
Passively crosses biological membranes, permeability is low because of its low solubility in lipid bilayer
Urea transporters (4) move urea by facilitated diffusion out of the proximal tubule.
Urea plays a role in the establishment of an osmotic gradient in the medullary pyramids.
Increases the ability of the kidney to concentrate urine in the collecting ducts .
Where in the kidney is the tubular fluid isotonic?
Proximal convoluted tubule
In the PCT water moves passively out of the tubule along the osmotic gradient.
Conditions that increase renin secretion
Sodium depletion, diuretics, hypotension, haemorrhage, upright posture, dehydration, cardiac failure, cirrhosis, constriction of renal artery or aorta
Factors that inhibit renin secretion
Increased Na and Cl reabsorption across macula densa
Increased afferent arteriolar pressure
Angiotensin II
Vasopressin
Describe the cells that make up the proximal convoluted tubule?
Made up of a single layer of cells that interdigitate with one another and are united by apical tight junctions
Luminal edges of the cells had a striate brush border due to microvilli
Describe the renal handling of potassium?
Potassium (K) is actively reabsorbed in the proximal convoluted tubule
K is secreted in the distal tubular cells
In the collecting ducts K is secreted
The rate of K secretion is proportionate to the rate of flow of the tubular fluid through the distal portions of the nephron, because with rapid flow there is less opportunity for the tubular K concentration to rise to a value that stops further secretion
Describe Vasopressin
AKA Antidiuretic Hormone
Released from posterior pituitary
Increases the permeability of the collecting ducts so that water enters the hypertonic interstitium of the renal pyramids.
urine becomes concentrated and volume decreases.
standing increases vasopression secretion
There are 3 vasopressin receptos V1a, V1b, V2
Describe the Proximal Convoluted Tubule
15mm long
55um in diameter
wall is made up of single cell layer, united by tight apical junctions.
Luminal edges have a brush border due to microvilli
Found in the cortex of the kidney