Special pathology - renal pathology Flashcards
Name the main parts of a nephron in order: (6)
- Glomerulus
- Proximal convoluted tubulue
- Descending loop of Henle
- Ascending loop of Henle
- Distal tubule
- Collecting duct
Function of the 2. Proximal convoluted tubule (3)
reabsorbs ions, water and nutrients;
actively transports toxins and drugs from the interstitial fluid into the filtrate.
adjusts filtrate pH
Function of the 3. Descending loop of Henle
aquaporins, water reabsorption
Function of the 4. Ascending loop of Henle
Na+ and Cl- reabsorption
Function of the 5. Distal tubule
selective secretion
ion reabsorption for pH and electrolyte balance
Function of the 6. Collecting duct
reaborbs more solutes and water
What are macula densa?
in the wall of the distal tubule, are salt sensors that detect filtrate Na+ concentration in tubule, and then generate paracrine chemical signals in the juxtaglomerular apparatus to control renin release from the juxtaglomerular epithelial cells
(thus renal blood flow and glomerular filtration is controlled by macula densa)
an increase in sodium chloride concentration in the distal tubule detected by macula densa cells would result in
reduced paracrine stimulation of juxtaglomerular cells and thus vasoconstriction of afferent arterioles.
This demonstrates the macula densa feedback, where compensatory mechanisms act in order to return GFR to normal.
Constriction of the afferent arterioles has two effects: it increases the vascular resistance which reduces renal blood flow, and it decreases the pressure downstream from the constriction, which reduces the GFR.
A decrease in sodium chloride concentration in the distal tubule detected by macula densa cells initiates a signal that has two effects:
(1) it decreases resistance to blood flow in the afferent arterioles, which raises glomerular hydrostatic pressure and helps return the glomerular filtration rate (GFR) toward normal, and
(2) it increases renin release from the juxtaglomerular cells of the afferent and efferent arterioles, which are the major storage sites for renin.
renin increases blood pressure
The renin-angiotensin-aldosterone system is a
series of reactions designed to help regulate blood pressure.
When blood pressure falls, the kidneys release the enzyme
renin into the bloodstream.
What happens next?
Renin splits angiotensinogen, a large protein that
circulates in the bloodstream, into pieces.
angiotensin I is produced.
Angiotensin I, which is relatively inactive, is split by
angiotensin-converting enzyme (ACE) into angiotensin II, a hormone, which is very active.
Angiotensin II causes? (3)
the muscular walls of arterioles to constrict, increasing blood pressure.
Also triggers the release of aldosterone from the adrenals and the release of vasopressin/ADH from the pituitary.
Aldosterone and vasopressin cause the kidneys to do what
retain sodium.
(Aldosterone also causes the kidneys to excrete potassium.)
The increased sodium causes water to be retained, thus increasing blood volume and blood pressure.
Aldosterone causes the kidneys to retain sodium.
How does it affect potassium?
Aldosterone also causes the kidneys to excrete potassium.
Renal diseases can be divided in two ways. What are they?
Into either;
1. Glomerular diseases
2. Tubular diseases
Or into;
1. ACUTE KIDNEY INJURY
2. CHRONIC KIDNEY DISEASE
Polyuria
production of abnormally large volumes of dilute urine.
urine output greater than 2 ml/kg/hour
Oliguria
the production of abnormally small amounts of urine.
urine output less than 1-2 ml/kg/hour in a well-hydrated patient.
no urine output
anuria
the production of abnormally small amounts of urine is known as
oliguria
Azotemia
High concentrations of nitrogen-containing compounds in
the blood.
Either N as Blood urea nitrogen
(BUN – nitrogen product from liver) or
creatinine (metabolic product of nitrogen from muscles).
azotemia can be further described as one of 3 options
Pre-renal
Renal
Post-renal
examples of Pre-renal causes of azotemia (5)
Dehydration
Heart diseases (hypotension – low filtration rate)
Shock
A diet rich in protein (only elevated BUN)
Bleeding in the digestive tract (only elevated BUN)
examples of renal causes of azotemia (1)
renal failure
examples of post-renal causes of azotemia (2)
Urinary tract obstruction
Bursting of the bladder
What is uremia?
azotemia + clinical signs
(loss of appetite, vomiting, diarrhea, bleeding in the
stomach and intestines, mouth
What is the difference between uremia and azotemia?
Pretty much means, azotemia with clinical signs.
So azotemia only describes increased concentration of nitrogenous compounds in blood but its without clinical signs.
Describe Assessment of GFR in clinical practice
(glomerular filtration rate)
Estimation of GFR is done using circulating biomarkers.
creatinine is the most important one but many things influence this marker so interpretation can be tricky