Flashcards in Renal Deck (85)
How is blood supplied to kidneys?
-via the renal arteries (they arise from the aorta).
How does venous drainage of kidneys occur?
- via the renal veins into the inferior vena cava.
What are the functions of the kidney?
- excretion of waste products (nitrogen containing compounds urea and creatinine - which arise from the metabolism of proteins and muscle: these substances are measured in blood as a way of assessing renal function) and toxins.
- water, electrolytes and acid-base homeostasis are dependent on renal function.
- kidney also has endocrine functions: it secretes renin which plays a vital role in maintaining blood pressure.
- it also produces hormone erythropoietin which stimulates the production of RBC in bone marrow.
- renal tissue is responsible for he activation of vitamin D through hydroxylation at carbon 1 (1 alpha) and therefore has an important role in calcium metabolism.
What are the functional units for production of urine?
- Nephrons (healthy human kidney has around 1 million nephrons).
- each nephron can be regarded as a filter (the bowmans capsule) which drains into a lengthy tube.
- the filtrate is modified as it passes along the tube until it enters the collecting duct and is carried to the ureter for excretion.
Where does filtration take place?
- it takes place in the bowmans capsule (which is like a cup containing a knot of capillaries which are known as the glomerulus).
- blood is carried to the glomerulus by the afferent artery and leaves via the efferent artery.
- as it travels through glomerular capillaries blood is filtered: large structures such as blood cells and large proteins are retained within capillaries while water and smaller molecules pass through capillary walls to form the glomerular filtrate which is collected in bowmans capsule and then passes into proximal tubule.
What is the function of the distal tubules?
- most of the fine tuning of renal excretion takes place in the distal tubules.
- they are involved in acid-base homeostasis, sodium-potassium exchange and regulation of calcium and phosphate excretion.
Where is antidiuretic hormone secreted (ADH)?
- secreted by posterior pituitary gland.
What is major difference between intracellular and extracellular fluid?
- electrolyte content.
- sodium is main cation in extracellular fluid.
- potassium is main cation in intracellular fluid.
How can extracellular fluid be divided?
- 1/3 (5L) in blood circulation (intravascular fluid).
- 2/3 (10L) in spaces between cells (interstitial fluid).
Where does most water intake come from?
- drinks (1500).
- water content of food (600).
- water generated by metabolism during oxidation of glucose and fatty acids (400).
- = 2500ml.
Where does most water output come from?
- urine (1500).
- faeces (larger if dihorreha) (100).
- skin (400).
- lungs (500).
- = 2500mls.
What is the ureter?
- duct by which urine is carried from kidneys to bladder.
What is intake of fluid regulated by?
- thirst centre in hypothalamic region of brain.
- it responds to changes in extracellular osmolality and also large alterations of circulating fluid volumes.
What is excretion of water regulated by?
- antidiuretic hormone (ADH) which is released from the posterior pituitary gland.
- this is sensitive to changes in osmolality and also responds to alterations in circulating fluid volume.
What releases renin, why does it release it, and what is the function of renin?
- renin is released from juxtaglomerular cells in response to a fall in renal perfusion pressure.
- renin triggers the cascade which results in sodium and water retention.
- this expands extracellular fluid volume resulting in improved renal perfusion.
What is increased plasma osmality an indicator of?
- dehydrated patient.
How many kidneys do we have?
What is a ureter?
- tubes that carry urine from kidneys to bladder.
Which arteries/veins enter and leave the kidney?
- renal artery enters the kidney.
- ureter and renal vein leave the kidney at the helium.
On sectioning of the kidney what are the two distinct areas of tissue?
- outer cortex.
- inner medulla.
Urine which is produced by the renal tissue is collected where?
- urine is collected in a branched system of ducts.
- these empty via the renal papillae into the cup-like cavities (calyces) where the urine gets accumulated before passing into the bladder through the ureter.
What happens as glomerular filtrate passes through the proximal tubule?
- active transport mechanisms reabsorb glucose, amino acids, proteins, bicarbonate and other electrolytes.
- water is reabsorbed along with electrolytes following the osmotic gradient.
How is an osmotic gradient across the kidney created?
- differential reabsorption of electrolytes do water within the loop of henle and surrounding blood vessels which are known as the vasarecty creates an osmotic gradient across the kidney.
- this is known as counter-current mechanism.
Where are the most highly concentrated fluids (both within the tubule and blood vessels surrounding the tubule) found?
- they are found in the medulla at the tip of the loop of henle.
The creation of an osmotic or concentration gradient within the kidney is an essential mechanism for ...
- diluting and concentrating urine in the collecting ducts.
Tubular fluid enters collecting ducts which are responsive to ...
- antidiuretic hormone (ADH).
What is the function of ADH in the collecting ducts?
- ADH determines the degree to which collecting ducts are permeable to water.
What happens if collecting ducts are permeable/impermeable to water in response to ADH?
- if collecting ducts are permeable to water in response to ADH: water leaves ducts along concentration gradient and will not be excreted (in other words, a concentrated urine will be produced).
- if collecting ducts are impermeable to water due to the absence of ADH: water is retained within the collecting ducts and excreted as a dilute urine.
Describe the water content of the body.
- approximately 45L in adult.
- 1/3 outside cells (extracellular): 15L.
- remaining 2/3 inside cells (intracellular): 30L.