Genitourinary system Flashcards
What is the typical liquid intake daily?
1200ml water, 1000ml food, 300ml metabolic=2.5L/day
What is the typical liquid output daily?
1500ml urine, 100ml sweat, 200ml faeces, 700ml insensible loss=2.5L/day
What is ‘insensible’ water loss?
Water loss due to:
-Transepidermal diffusion: water that passes through the skin and is lost by evaporation, and
-Evaporative water loss from the respiratory tract
It is termed insensible as we are not aware of it.
What is the glomerular filtration rate governed by?
The arterial blood pressure arriving at the glomerulus. This pressure is highly regulated by systemic and local control of the diameter of the afferent/efferent arterioles.
What is the macula densa?
A unique group of 15-20 cells that are located at the end of the cortical thick ascending limb. The cells sense changes in tubular fluid composition, generating and sending signals to the juxta-glomerular apparatus that controls renal blood flow and GFR through tubuloglomerular feedback and renin release.
What is ‘auto regulation?
The process by which the afferent arterioles response to the changes in pressure in the glomerulus by dilating or constricting. This maintains the pressure constant between 60-70mmHg.
What does atrial natriuretic peptide do?
When the atria of the heart are distended (increased venous return), they release ANP, which does the following:
-dilation of the afferent arteriole, constriction of the efferent arteriole.
-decreases Na+ reabsorption in the distal tubule.
-inhibits renin release from the macula densa.
Overall the effects of ANP include an increase in the volume of primary urine, reduced Na+ and reduced blood volume.
What happens if the afferent arterioles constrict?
The filtration pressure drops and filtration in the glomerulus is reduced.
What happens if the efferent arterioles constrict?
The filtration pressure increases and filtration in the glomerulus is increased.
Describe capacity and affinity in the proximal tubule
There is high capacity (Vmax) and low affinity. There is bulk reabsorption of solutes and water. Mainly amino acids and glucose are 100% reabsorbed.
Describe capacity and affinity in the distal tubule
There is low capacity and high affinity transporters. This is where fine tuning of solutes and water occur, under the influence of aldosterone.
What does aldosterone done?
Causes reabsorption of Na+ but not of K+.
When is anti-diuretic hormone produced and what does it do?
ADH is produced by the posterior pituitary gland in response to: dehydration, haemorrhage, low blood volume, when extracellular osmolarity of Na+ rises and stress. Increase ADH-increase channels- increased reabsorption of water. Decreased ADH-decreased channels-decreased water reabsorption- water loss.
What do diuretics do?
Increase the volume of urine produced. Therefore there is: decreased plasma volume, decreased venous return and decreased arterial and venous blood pressure. Patients with hypertension, congestive heart failure and oedema benefit from diuretics.
What does Furosemide do?
It is a loop diuretic that increases the rate of urination. It acts on the thick ascending limb of the Loop of Henle and inhibits Na+/Cl-/K+ symports.
