Urinary System (Topic 13) Flashcards
Where do kidneys lie? (2)
back of the abdominal wall
- retroperitoneal
What does the ureter do? (2)
transport urine from kidneys to bladder
What does the bladder do? (2)
stores urine until voided from the body
What does the urethra do? (2)
carries urine from the bladder tot he outside of the body
What are the functions of the kidneys? (3)
- regulates water
- removes waste from blood
- gluconeogenesis
- secretes hormones (renin and calcium)
What is a nephron? (4)
functional unit of kidney (forms urine)
- each kidney has 1 million nephrons
What is the renal cortex? (4)
The outer portion
- contains renal corpuscles
What is the renal medulla? (4)
inner portion
- Loops of Henle extend into medulla.
- Contains the medullary collecting ducts.
What does a nephron consist of? (5)
- renal corpuscle
- renal tubule
What does a renal corpuscle consist of? (5)
- glomerulus: tuft of capillary loops
- Bowman’s capsule: cup shaped around the glomerulus
What are the two types of nephrons? (7)
- juxtamedullary
- cortical
What is a juxtamedullary nephron? (7)
- long loop of henle
- concentration of urine
- found at the border between cortex and medulla
- about 15% of all nephrons
What is a cortical nephron? (7)
- 85% of all nephrons
- short loop pf Henle
- reabsorption and secretion
What is glomerular filtration? (8)
a passive process in which hydrostatic pressures force the fluids and solute through a membrane.
- ~20% of plasma filters into Bowman’s Capsule
- Forms a filtrate that is free of cells & proteins
What is special about golmerular capillaries? (8)
are specialized for filtration. These are the only capillaries in the body that are fed and drained by an arteriole (afferent and efferent).
How do glomerular capillaries affect pressure? (8)
they maintain and increase blood pressure
What affects the rate of filtration? (10)
- permeability of the capillaries
- surface area available for filtration
- constriction or dilation of the arterioles
What is the most abundant cation in filtrate? (13)
sodium
Na+ reabsorption is passive across luminal membrane and active _______________ across basolateral membrane. (13)
Na/K pump
What does the active pumping of sodium generate? (13)
generates a gradient that couples to passive entrance of other substances (glucose, etc.) via co-transporters across the luminal membrane.
Where does substances like H+, K+, and organic anions move? (14)
from the peritubular capillaries into the tubular lumen
What does tubular secretion do? (14)
removes more of a substance than filtration alone
- Regulation of reabsorption and/or secretion is in response to hormones and paracrine/autocrine factors.
Tubular secretion is an important mechanism for: (14)
- Disposing of drugs and drug metabolites
- Eliminating undesired substances or end products that have reabsorbed by passive processes (urea and uric acid).
- Removing excess K+
- Controlling blood pH
What is urine? (15)
filtrate + secretum - reabsorption
- formed in the renal tubules
Where does urine drain into? (15)
renal pelvis -> ureter -> bladder
What is the reflex that makes you pee? (15)
micturition reflex
- initiated by a nervous reflex
(smooth muscle of the bladder walls to contract and the expel the urine)
What is the external sphincter? (15)
- skeletal muscle
- Contraction prevents urination even when smooth muscle contraction is strong
What is incontinence? (18)
inability to control urination
- More common in women
What are common types of incontinence? (18)
stress incontinence (due to sneezing, coughing, or exercise)
- Treatment: Medications (such as estrogen replacement), therapy (to improve vaginal tone), Surgery (improve vaginal support of the
bladder and urethra)
urge incontinence (associated with the desire to urinate).
- Any irritation to the bladder or urethra (e.g., with a bacterial infection)
- Treatment: Medication (that antagonize the effects of the parasympathetic nerves on the detrusor muscle)
How does antagonizing the parasympathetic nervous system help incontinence? (18)
Na+ reabsorption occurs in all tubular segments except what? (19)
the descending limb of the loop of henle
By what process is water reabsorbed? (19)
osmosis (passive)
What does water move through? (19)
aquaporin channels
- presence of these aquaporins varies throughout the tubule segments.
- highly expressed in the proximal tubule.
- Varies in different segments of loop of Henly
- absent in the collecting ducts unless Anti-diuretic hormone (ADH) is active.
go over slide 21 & 22
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Why is it important that our bodies can make a concentrated urine? (23)
- to reduce water loss
The descending limb of the loop of Henle is ___ (23)
- impermeable to solutes
- permeable to water
The ascending limb of the loop of Henle is ___ (23)
- impermeable to water
- permeable to solutes
Medullary interstitial fluid is _____ (23)
hyperosmotic
- Partially due to urea recycling
Go over slide 24
thumbs up
Why is the osmolarity of the interstitial fluid always slightly higher? (24)
the active pumping of salt, increases the osmolarity of the interstitial fluid which allows for the passive reabsorption of water
What is urea? (25)
- Helps maintain hyperosmotic medullary interstitial fluid
- Urea is freely filtered in glomerulus
- 50% is reabsorbed in proximal tubule
- Various stages of secretions and reabsorption.
- ~15% of that originally filtered is excreted in urine
What are juxtaglomerular cells? (26)
enlarged smooth muscle cells that secrete the hormone renin
What do JG cells do? (26)
mechanoreceptors (sense blood pressure) in the afferent arteriole
What are macula densa cells? (26)
group of tall, closely-packed cells that line a portion of the distal tubule.
-These cells work in tandem and are critical regulators of blood pressure.
How can glomerular filtration rate be reduced? (27)
can be reduced in response to increase Na+ and water loss. (ex. Diarrhea)
What are the mechanisms of glomerular filtration rate? (27)
- Activation of sympathetic nerves
- Reduction of arterial blood pressure
If your body is trying to increase fluid, does your body increase or decrease glomerular filtration? (27)
decrease filtration
What are three inputs to juxtaglomerulary cells? (28)
- Sympathetic nerves
- Arterial pressure
- Sodium sensors in macula densa
Go over slide 29 & 30
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