Unit 5 Flashcards
How is water added to the body?
Ingestion
Oxidation of CHO
What % of bodyweight is water?
60%
What % of bodyweight is intracellular fluid?
40%
What % of bodyweight is extracellular fluid?
20%
How do plasma and interstitial fluid differ?
Higher protein in plasma
Higher cations in plasma (Donnan effect)
Higher anions in interstitial fluid
Ddx hyponatraemia
Dehydration - adrenal insufficiency, diuretic overuse, v/d
Overhydration - ADH excess, bronchogenic tumours
Ddx hypernatraemia
Dehydration - DI
Overhydration - HAC, hyperaldosteronism
What are the causes of intracellular oedema?
Hyponatraemia
Depression of metabolic systems
Lack of cellular nutrition
Which part of the LOH is the ‘thin’ segment?
Descending and lower end of ascending
Where is the macula densa located?
At the end of the thick, ascending LOH
What are cortical and juxtaglomerular nephrons? How are they different?
Cortical nephron - glomeruli in outer cortex, short LOH than penetrate a short distance into medulla
Juxtaglomerular nephron - glomeruli deeper in cortex, long LOH
JG nephrons have vasa recta
Describe the neuroanatomy of the bladder
Supplied by pelvic nerves via the sacral plexus (S2-3)
Contains sensory + motor fibres
Motor n - parasympathetic fibres
Pudendal nerve - external sphincter (skeletal)
Hypogastric nerves - sympathetic - blood vessels
What innervates the a)detrusor, b)internal sphincter, c)external sphincter
a)pelvic n
b)pelvic n
c)pudendal n
What is the structure of the glomerular capillary membrane?
1 - endothelium
2 - basement membrane
3 - epithelial cells (podocytes)
How does efferent arteriolar constriction affect GFR?
Biphasic
Mild/moderate - slight increase in GFR
Severe - reduces GFR
How does afferent arteriolar constriction affect GFR?
Reduces
What is anatomy of the juxtaglomerular complex?
Macula densa cells in proximal distal tubule
Juxtaglomerular cells in afferent/efferent arteriole
Describe tubuloglomerular feedback
Reduced GRF => slow flow in LOH => increased Na/Cl reabsorption => reduced Na/Cl at macula densa => afferent arteriolar dilation + ^ renin release => efferent arteriolar constriction
What substances are found in higher quantities in plasma than glomerular filtrate?
Albumin
Calcium
Fatty acids
Describe the structure of the glomerular capillary membrane and how they alter filtration
Endothelium (with fenestrate). Endothelial proteins negatively charged - repeals plasma proteins
Basement membrane - mesh of collagen and proteoglycans. PGs negatively charged
Podocytes (with slit pores) - epithelium negatively charged
What conditions are associated with a reduction in glomerular capillary filtration coefficient?
CKD (reduced number of glomerular capillaries)
Systemic hypertension
How if filtration fraction calculated?
FF = GFR/RBF
What factors influence the glomerular capillary colloid osmotic pressure?
Arterial plasma osmotic pressure
Filtration fraction (affected by GFR and RBF)
How does efferent arteriolar constriction affect GFR?
Biphasic
If mild/moderate, slight increase
If severe, decreases (due to increased FF and glomerular colloid oncotic pressure)