Exam 3 | Renal Flashcards
What functions does the renal system perform?
filtration of blood & fluid homeostasis
osmoregulation
maintaining blood & plasma volumes
removing toxins from body
producing and secreting peripheral hormones and enzymes
What’s osmoregulation?
the maintenance of water retention and ion/metabolite concentrations in the blood and other body fluids
What are the 2 peripheral hormones/enzymes the renal system assists in?
Erythropoietin which is a protein that assists in the production of erythrocytes in response to cell loss/ damage
Renin is an enzyme that participates in the renal angiotensin-aldosterone system (RAAS)
Where are the kidneys located?
lower thoracic/ upper abdominal cavity towards the dorsal/posterior region
How does blood travel in the kidneys?
Renal artery: how the kidney receives blood
Renal vein: how blood travels out of the kidney
How does filtrate (urine) leave the kidneys?
Urine leaves the body via 2 ducts, the ureters (1 per kidney), which carry urine to the bladder
Describe the bladder
A semi-muscular sac that stores urine until the necessary/ appropriate time for voiding
Describe the structure of the kidney.
The outer layer is the cortex & the inner layer is the medulla.
The nephron runs through both
What is the smallest functional unit of the kidney?
the nephron
What’s the nephron’s job?
It is the site of blood filtration in the kidney
How many nephrons are in each kidney?
roughly 1 million
Describe the structures of the nephron
Glomerulus: which actually filters unnecessary molecules out of the blood
Descending & ascending tube (tubule): relays the remaining filtrate (which eventually becomes urine) to the ureter
What are the steps of blood filtration & urine formation?
- Filtration
- Reabsorption
- Secretion
- Excretion
What happens in the first step (filtration)?
Blood enters the nephron via the renal artery where it encounters the glomerular capillaries. These are adjacent to the entrance to the loop of Henle (Bowman’s capsule). Here, only small molecules/ions pass through the glomerular capillaries
What happens in the second step (reabsorption)?
After filtration, the filtrate is transferred to the descending loop where most of the water filtered out of the blood at the glomerulus returns to the body by diffusing out of the loop. Water is reabsorbed back into the body leaving high concentrations of small molecules/ions remaining in the filtrate as it is then transferred to the ascending loop.
Why is the reabsorption step so important?
If it weren’t for reabsorption, we’d end up voiding a dangerous amount of water during a 24-hour period
What happens in steps 3 and 4 (secretion & excretion)?
After the majority of the water leaves, the remaining filtrate passes through the ascending loop and collecting duct. Here, the osmolarity of the filtrate is rebalanced through some water returning to the filtrate as well as active transport of ions out of the ascending loop. Here, filtrate is mixed with urea to be excreted via the ureter to travel to the bladder
How does water return to the filtrate?
By specialized protein pumps, aquaporins
What ions are being actively transported out?
Sodium and chloride
What is urea?
A stable nitrogenous molecule compared to ammonia
What hormone is responsible for regulating urine volume (water retention)?
The posterior pituitary hormone, antidiuretic hormone (ADH or vasopressin; for male reproductive system), is critical for adjusting the permeability of the collecting duct in the loop of Henle to water
What are diuretics?
chemicals that result in less water retention; this leads to an increases volume of urine and an increased rate of voiding
coffee and alcohol are 2 common diuretics
What happens when concentrations of ADH are high?
The amount of water reabsorbed into the collecting duct in the loop of Henle increases, resulting in a smaller volume of urine (more concentrated urine, darker in color)
What happens when concentrations of ADH are low?
The amount of water reabsorbed into the collecting duct in the loop of Henles decreases, resulting in a larger volume of urine (more diluted and lighter in color)
What roles do angiotensin and aldosterone play?
They play a critical role in helping to maintain a certain threshold of blood pressure by adjusting blood volume at the level of the nephron
What happens when there’s a decrease in blood pressure?
The kidneys will secrete the protein renin, which triggers the production and secretion of angiotensin 1 (inactive); once acted upon by the enzyme, angiotensin-converting enzyme (ACE), it converts to angiotensin 2 (active protein); angiotensin 2 triggers the release of aldosterone and ADH both which act on collecting duct and loop of Henle.
