Urinary System Flashcards
What are the functions of the urinary system?
- Regulation of blood volume and composition
- Regulation of blood pH
- Regulation of blood pressure
- Release of hormones
How does the urinary system function to regulate blood volume and composition?
- Adjusts volume of blood: can only remove extra or prevent further loss
- Remove wastes from blood ((urea, bilirubin, uric acid, and creatinine)
- Regulate ionic composition (Na+, K+, Cl-, Ca2+, HPO3)
- Maintains osmolarity (number of dissolved particles in blood)
The urinary system is responsible for the release of what hormones?
- Calcitriol
- Renin
- Erythropoietin
What is the function of the kidney?
production of urine
What is the internal anatomy of the kidney?
- cortex
- medulla
- nephron
Kidney: Cortex
outer layer, granular texture
Kidney: Medulla
inner layer, consists of 8-18 renal pyramids
Kidney: Nephron
functional unit of kidney; responsible for urine formation
What are the organs associated with the urinary system?
- ureters
- urinary bladder
- urethra
Organs associated with the urinary system do not do what?
do not modify urine
Ureters
Collect urine from kidney and transport it to bladder
Urinary bladder
- Storage site for urine until
micturition - Composed of smooth muscle
- Holds 700-800ml
Urethra
- connects the bladder to the outside environment
- Controlled by 2 sphincters
- Outer sphincter is skeletal muscle for voluntary control
Renal arteries
receive 20-25% of resting cardiac output
Afferent arteriole
brings blood to nephron
Glomerulus:
ball of capillaries
Glomerulus function
filtration (taking ish out blood)
Efferent arteriole
glomerular capillaries rejoin to form this
- takes blood away from glomerulus
Peritubular capillaries (bed)
formed from efferent arteriole
- surround tubular portion of nephron
Peritubular capillaries function
reabsorption (bringing ish back in)
Peritubular venule
formed from peritubular capillaries
Renal vein
takes blood away from the kidney
Renal plexus
nerves that enervate the kidney
Renal plexus function
control diameter of blood vessels
What are the two parts of a nephron?
renal corpuscle and renal tubule
Renal corpuscle
where plasma is filtered; located in the cortex of kidney
What are the two parts of the renal corpuscle?
glomerulus and Bowman’s capsule
Glomerulus is composed of what kind of capillaries?
enestrated (holes) capillaries
Bowman’s capsule
double-walled cup that surrounds the glomerulus and collects the filtrate
Renal tubule
modifies the filtrate
- composed of 3 sections
What are the three sections of the renal tubule?
- Proximal convoluted tubule (PCT
- Loop of Henle
- Distal convoluted tubule (DCT)
Proximal convoluted tubule (PCT)
70% of reabsorption takes place here
Loop of Henle
water and NaCl (salt) reabsorption
What are the two parts of the Loop of Henle
Descending limb: water permeable only
Ascending limb: NaCl permeable only
What are the functions of the nephron?
Filtration: removal of materials from the blood
- Pressure driven
Secretion: adding materials to the filtrate
- Active transport
Reabsorption: removal of materials from filtrate to remain in body
What processes are used by the nephron when performing the function of reabsorption?
- osmosis
- facilitated transport
- secondary active transport
What are the two types of nephrons?
cortical and juxtamedullary
Cortical nephron
- 80-85% of all nephrons
- Almost, if not all, lies in the cortex of the kidney
- Short loop of Henle
Cortical =
cortex
Juxtamedullary nephron
15-20% of nephrons
Corpuscles are deep in cortex
Have long loop of Henle that extends deep into medulla
Used in formation of concentration gradient
What are the associated structures of the nephron?
collecting ducts and papillary ducts
Collecting ducts
- Collects urine from several nephrons
- Site of final modification of urine
Papillary ducts
- Convergence of many collecting ducts
- Eventually empty into minor calyx
Glomerular hydrostatic pressure (GHP)
- High blood pressure in glomerulus because efferent arteriole is smaller in diameter than afferent arteriole
- Forces water and solutes across the glomerulus
- Filtration
~50 mmHg (filtration pressure)
What two pressures oppose glomerular filtration?
- Capsular hydrostatic pressure (CHP)
- Blood colloid osmotic pressure (BCOP)
Capsular hydrostatic pressure (CHP)
- Opposes filtration
- Due to fluid already in renal tubule
- ~15 mmHg
Blood colloid osmotic pressure (BCOP)
- Opposes filtration
- Due to presence of proteins in blood
- ~ 25 mmHg
Net filtration pressure
GHP – (CHP + BCOP)
- 50 mmHg – (15 + 25) = 10 mmHg
Glomerular filtration rate (GFR)
Amount of filtrate formed in both kidneys per minute
- ~ 125 ml/min - 180 L/day (most of this gets reabsorbed)
How is GFR controlled?
Primarily achieved by adjusting blood flow into and out of the kidney
- Autoregulation
- Hormonal regulation
- Autonomic regulation
GFR/renal autoregulation occurs through the use of what?
Myogenic mechanism
Myogenic mechanism
Increase in blood pressure causes increase in GFR
Stretch of afferent arterioles due to increased blood pressure causes vasoconstriction of blood vessels
Vasoconstriction causes reduction in blood flow
Reduction in blood flow causes GFR to decrease
Opposite happens if blood pressure decreases
GFR hormonal control is done through the use of what?
Renin-Angiotensin system and Atrial natriuretic peptide (ANP)
Renin- Angiotensin system
In response to decrease in blood pressure/volume
Decrease in stretch of arterioles causes release of renin
Renin acts on peptide produced in the liver to form angiotensin I
Angiotensin I is converted to angiotensin II in the lungs
Effects of angiotensin II
Vasoconstriction
Release of aldosterone (salt balance)
Stimulates thirst centers
Release of ADH (anti-diuretic hormone)
Increased cardiac output
Overall increases blood pressure & water retention
Decreases urine output
Atrial natriuretic peptide (ANP)
Secreted by the heart in response to stretching of atria
Suppresses secretion of ADH and aldosterone
Increases GFR by increasing glomerular blood pressure (vasodialation)
For reduction of blood volume
Increases urine output
GFR neural control is done through the use of what?
Sympathetic nervous fibers
Sympathetic nervous fibers
Norepinephrine causes vasoconstriction of afferent arterioles
Reduction in GFR
Decreased urine output
60-70 % of all filtrate is reabsorbed where?
PROXIMAL CONVOLUTED TUBULE (PCT)
How does the Loop of Henle perform transport?
Water in the descending limb
- via Osmosis
NaCl in the ascending limb
- via Active transport
- not permeable to water
How does the Loop of Henle form a concentration gradient?
- Fluid flows in opposite directions
- Countercurrent multiplier
Countercurrent multiplier
refers to the process in which energy is used to create an osmotic gradient that enables the reabsorption of water from the tubular fluid, so that urine can be concentrated
Distal Convoluted Tubule
Movement of same materials as in PCT
Under hormonal influences
- aldosterone
- Parathyroid hormone and calcitrol
What materials are moved by the proximal and distal convoluted tubules?
Water, ions, glucose, amino acids
- secretes H+, K+
90-95% of all solutes and water from the filtrate have been returned by the time they reach what?
collecting ducts
What are the two types of water reabsorption
Obligatory reabsorption and Facultative reabsorption
Obligatory reabsorption
- Linked to reabsorption of solutes
- Cannot alter this
- Occurs in PCT and descending limb of Henle
Facultative reabsorption
Occurs primarily in collecting duct
Is controlled by ADH
- aquaporins
How does Antidiuretic Hormone (ADH) affect water reabsorption?
Regulates facultative water reabsorption
Stimulates water reabsorption in collecting ducts
Release is stimulated by an increase in blood osmorality
Release is inhibited by caffeine, alcohol, ANP
