Week 12 - Urinary System Flashcards
Locate the following structures on a diagram: • Glomerulus • Glomerular capsule • Proximal convoluted tubule (PCT) • Loop of henle • Distal convoluted tubule (DCT) • Collecting ducts
N/A
What is the glomerulus ?
Is a series of capillaries that allows the flow of blood into the glomerular capsule.
What two components make up the renal corpuscle?
- Glomerulus
* Glomerulus capsule
What are the three components of the renal tubules and their respective functions?
- PCT - Bulk absorption of nutrients and fluids (passive)
- Loop of henle - concentration and dilution of filtrate
- DCT - Fine tuned absorption of substances (hormonal)
What are the role of collecting ducts?
To receive filtrate from multiple nephrons and transport them to the renal pelvis.
What are the functional units of the kidneys?
Nephrons
What are the different cell types found in: • Glomerular capsule: • PCT • Loop of Henle: • DCT:
• Glomerular capsule:
• Parietal layer - simple squamous that from the
capsule
• Visceral layer - podocytes to allow passage of
filtrate
• PCT - simple cuboidal (increased SA)
• Loop of Henle - simple squamous (water reasbsorption)
• DCT - simple cuboidal
What are the two types of capillaries associated with nephrons and briefly describe them
- Glomerular capillaries - Arise from the afferent arteriole, responsible for producing filtrate from the blood stream
- Peritubular capillaries - arise from the efferent arterioles and are responsible for reclaiming filtrate back into the blood from the renal tubules.
What is the difference between filtrate and urine?
Filtrate is what enters the glomerular capsules from the glomerular capillaries, whereas urine is what is actually secreted from the body.
List the 3 processes performed by nephrons to produce urine
1) Glomerular filtration
2) Tubular reabsorption
3) Tubular secretion
Why is glomerular filtration a passive process?
Substances move passively into the glomerular capsule due to differences in pressure - moves down the pressure gradient.
Why are large molecules such as blood cells and plasma proteins excluded from the filtrate?
The are too large to pass from the capillaries into the glomerular capsule
How is glomerular pressure regulated?
The dilation and constriction of the afferent and efferent arterioles.
Glomerular filtration depends on 3 main pressures. List them and indicate whether they promote or oppose the formation of filtrate
- Glomerular hydrostatic pressure - Promote
- Capsualr hydrostatic pressure - Oppose
- Blood colloid osmotic pressure - Oppose
The ascending loop concentrates filtrate and thus is permeable to _______ but is impermeable to ______
- Water
* Solutes
The ascending loop dilutes the filtrate and thus is permeable to _______ but is impermeable to ______
- Solutes
* Water
The reabsorption of filtrate in the PCT is under what kind of control?
passive
The reabsorption in the DCT is under what kind of control?
hormonal
What hormones are associated with the DCT and what are there functions?
- Aldosterone - promotes sodium reabsorption and thus the reabsorption of water
- ADH - promotes water reabsorption by inserting aquaporins into the kidney tubules.
Why is Na+ reabsorption the driving force for water and solute reabsorption.
Na+ is the main extracellular ion and this its concentration gradient drives the movement of water and consequently other ions.
Where is the nephron does tubular secretion occur?
PCT and DCT
Why is tubular secretion important?
Allows for the disposing of unwanted waste products and for the regulation of various substances in the body.
What structure carried the urine from the kidneys to the bladder?
ureters
What structure stores urine?
bladder
What structure carries urine from the bladder to the external environment?
urethra
Where is the detrusor muscle found
middle layer of bladder
The internal urethral spincter is composed of _____ muscle and this is under _______ control
Smooth, involuntary
The external urethral spincter is composed of _____ muscle and this is under _______ control
Skeletal, voluntary
What triggers micturition
The detection of stretch in the bladder as it fills with urine
What three things must occur for micturition to occur?
- Detrusor muscle contraction
- Internal urethral sphincter opens
- External urethral sphincter opens
Why are infants unable to control urination?
At this age micturition is purely a spinal reflex
Stretch receptors > Sacral spinal cord > parasympathetic stimulation causes detrusor muscle contraction and the opening of the internal urethral sphincter.
What area of the brain stem controls micturition?
pons
What are the two areas of the pons that participate in micturition and do they inhibit or promote micturition?
• Pontine storage centre - inhibits
• Suppresses parasympathetic stimulation and
enhance sympathetic stimulation to internal
urethral sphincter
• Pontine micturition centre - promotes
• Inhibits sympathetic stimulation and enhances
parasympathetic stimulation to the internal
urethral sphincter
• When there is decreased somatic stimulation to
the external urethral sphincter, urination occurs
Complete the innervation and nervous system activity for urination to occur:
• Detrusor muscle:
• Internal urethral sphincter:
• External urethral sphincter:
• Detrusor muscle: Sympathetic (decreased),
Parasympathetic (increased)
• Internal urethral sphincter: Sympathetic (decreased),
Parasympathetic (increased)
• External urethral sphincter: Somatic (decreased)
What intake is used to crudely regulate water levels
Thirst
What are the three main stimuli for initiating the thirst mechanism?
- Low saliva levels
- Decreased blood volume / blood pressure
- Rising plasma osmolarity
Where are the osmoreceptors for thirst located?
hypothalamus
What is the major stimulus for ADH secretion?
Changes in blood osmolarity
Where is ADH secreted from?
Posterior pituitary gland
What area of the of the nephron is targeted by ADH
DCT and collecting ducts
What is the general mechanism for regulating dehydration with ADH?
Dehydration > High blood osmolarity > ADHsecretion from posterior pituitary > Insertion of aquaporins into DCT and collecting ducts
Why is it important to maintain the pH of our body fluids?
Metabolic processes are dependent on the activity of enzymes which are highly sensitive to changes in pH
Where are the majority of acids in the body derived from?
Metabolic byproducts
What are the three mechanisms that help regulate the pH levels of the body. Compare there rates
- Respiratory mechanisms -Medium
- Buffer systems - Fast
- Renal mechanisms - Slow
What are the three major buffer systems in the body?
- Protein buffer system - intracullar and extracellular
- Phosphate buffer system - intracellular
- Carbonic acid buffer system - extracellular
What buffer mechanism regulates plasma pH?
Carbonic acid - bicarbonate ion buffer system
What is the relationship between carbonic acid and bicarbonate ions?
H2CO3 <> HCO3 - + H+
What is the relationship between CO2, water and bicarbonate ions
CO2 + H2O <> H2CO3
What receptors detect pH changes and where are the located?
Chemoreceptors located in the aortic arch, corotid body and medulla.
How does the respiratory system respond if the levels of CO2 in the extracellular fluid rise
Increases ventilation rate
How does the respiratory system respond if the levels of CO2 in the extracellular fluid decline
Decrease ventilation rate
How do the kidneys help with the long term regulation of blood ph?
Secrete H+ and retrieve HCO3-
