The Urinary System Flashcards
List the organs included in the renal system
- 2 kidneys
- 2 ureters
- 1 bladder
- 1 urethra
State the role of the 2 ureters
transport urine from the kidneys to the bladder
State the role of the bladder
temporary urine storage
State the role of the urethra
transports urine from the bladder to outside the body
Where is urine formed?
In the kidneys
What waste products are eliminated through the renal system?
drugs
toxins
nitrogenous wastes
What aspects of homeostasis is regulated by the renal system?
- water balance
- electrolyte balace
- acid balance in blood
- blood pressure regulation
- red blood cell production
- activation of Vitamin D
Describe the positioning of the kidneys?
- upper, posterior abdominal wall
- left kidney slight higher than right due to the liver sitting above the right kidney
What are the kidneys protected by?
thick outer fibrous capsule, surrounded by bed of fat, protected by lower limbs
What is the ‘hilum’ and what happens there?
The concave border of the kidneys that renal arteries and nerves enter and renal veins and ureters exit
What are the two main parts of the kidney
cortex (inner)
medulla (outer)
Kidney structures: describe the renal or medullary pyramids
triangular regions of tissue in the medulla (outer)
Kidney structures: describe the renal columns
extensions of cortex-like material inward that separate the pyramids
Kidney structures: describe the calyces
cup-shaped structures that funnel urine towards the renal pelvis
Kidney structures: describe the renal pelvis
funnels urine toward the ureter
What does the ureters do?
drain urine from the kidneys to the bladder
Explain the muscle within the ureters
Layers of both longitudinal and circular smooth muscle which propels the urine along the structures
What does the mucosal membrane line?
Renal pelvis and ureters
What does the layers of mucous protect within the pelvis and ureters?
Protects the epithelial cells form urine as the pH of urine can differ drastically and would damage cells
What is the bladder?
A reservoir for urine
A muscular sac that can expand considerably
Where is the bladder situated?
the pelvic cavity but when full it expands not the abdominal cavity
What are the 3 layers of the bladder?
1 - inner and outer layers of longitudinal muscle fibres
2 - middle layer of circular muscle fibres
3 - lined with mucosal membrane
What is the urethra?
A muscular tube that carries urine from the bladder and out of the body
What is a nephron?
the basic functional unit of the kidneys where plasma is filtered and urine is formed
How many nephrons are in each kidney?
about 1 million
What are the 4 main parts of a nephron?
- Glomerular capsule/Bowman’s capsule
- Proximal convoluted table
- Loop of henle
- Distal convoluted tubule
Simplify the blood flow in the kidneys
1 - renal artery enters the kidney
2 - arteriole enters the glomerular capsule of each nephron and divides into capillary network called the glomerulus:
- afferent and efferent arterioles
3 - efferent arterioles forms another capillary network which surrounds the rest of the nephron before reforming as veins
Explain the formation of urine
- the first stage is filtration: water and solutes in blood are filtered out of the blood stream - the filtered fluid is called ‘filtrate’
- filtrate flows out of glomerular capsule through tubule
- most of filtrate is reabsorbed back into blood as it passes through the tubule
- some substances pass from blood into filtrate
3 simple steps for formation of urine
- filtration
- reabsorption
- secretion
Explain when filtrate becomes ‘urine’
After leaving the collecting duct the processes of reabsorption and secretion are completed, the fluid is now classed as ‘urine’
What is urine?
Urine is what remains after the filtrate has lost most of its water, nutrients and necessary ions
What does urine contain?
Water (95%) Nitrogen wastes (5%) urea, creatinine, ammonia, uric acid Electrolytes Hydrogen ions
Define electrolytes
Inorganic compounds which dissociate into ions in solution
What do electrolytes do?
dissociate in solution to form +charged ion and - charged
What is a ‘cation’?
Positively charged ion
What is an ‘anion’?
Negatively charged ion
What is the role of the kidneys?
filter the blood and bi-products, produce urine
What is the role of the right and left renal arteries?
supplies oxygenated blood to the kidneys
What is the role of the right and left renal veins?
returns oxygenated blood to the heart from the kidneys
Function: what does the urinary system excrete from the plasma?
nitrogenous waste, toxins and drugs
Function: what does the urinary system regulate in the body?
plasma electrolyte, fluid balance and plasma pH acid-base balance (7.35-7.45)
Function: what does the urinary system regulate long term?
blood pressure through regulating blood volume
Function: what does the urinary system produce?
erythropoietin and renin
What is erythropoietin?
a hormone that regulates the production of red blood cells in the bone marrow
What is renin?
an enzyme that helps regulate blood pressure
What percentage of cardiac output occurs in the kidney? Why?
20% - high blood supply in order to effectively filter the blood
Why is there a high blood supply in the kidneys?
to maintain a high glomerular filtration rate
Why is blood supply to the kidneys vital?
failure to supply blood to the kidneys can lead to kidney failure
How is blood supplied to the kidneys?
via left and right renal arteries, branch from aorta
What are the 3 processes undertaken by nephrons?
1 - glomerular filtration
2 - tubular reabsorption
3 - tubular secretion
What is glomerular filtration?
blood is filtered into the kidney tubules from the glomerulus
What is tubular reabsorption?
substances are reabsorbed back into the blood from the kidney tubules
What is tubular secretion?
substances are secreted from the blood into the kidney tubules
Adaptations: approx. how long are the ureters?
25-30cm
Adaptations: What is the inner lining of the ureters referred to as?
transitional epithelium
Adaptations: What is the middle layer of the ureters referred to as?
muscular layer and an outer fibrous coat
What does the membraneous sphincter of the urethra do during pregnancy?
helps control urine flow and maintain continence
How is urination/micturition controlled?
by the higher brain centre, via the nerve impulses, via spinal cord
In order to urinate co-ordinated activity between autonomic part of the system and voluntary control.. describe the sympathetic and parasympathetic action
sympathetic - relaxation of bladder wall and increased tone of internal urethral sphincter - inhibiting micturition
parasympathetic - relaxation of internal urethral sphincter and contraction of muscular bladder wall
Describe step by step the process of micturition
as urine accumulates, bladder wall descends, stretch receptors stimulated, message sent via parasympathetic nerve to sacral region of final cord and back to the bladder causing reflex contractions, as contractions increase, urine enters the urethra and past the internal sphincter
In pregnancy there is an increase in renal plasma (blood) flow. Why?
substantial vasodilation of renal circulation
Pregnancy increases both cardiac output and blood volume. True or false?
true
In pregnancy, kidneys increase in size by how much?
lengthen by approx. 1cm
volume increase up to 30%
Bladder capacity increases in pregnancy by how much and why?
1000mls, due to relaxing effects of progesterone on the smooth muscle
Why is there an increased likelihood for STI’s in pregnancy?
alkaline urine, increased bladder volume, reduced muscle tone
In pregnancy, ureters act as a reservoir for urine. How do they change in state for this role?
dilate, curve, become ‘turtuous’
What are the effects of dilated ureters in pregnancy?
reduced peristalsis and enlarging uterus is urinary static and increased likelihood of UTI’s
Why is glucose excretion in urine increased in pregnancy?
glomerular filtration rate
What percentage of women are effected by ‘glycosuria’ in pregnancy?
50%
How does the bladder change in pregnancy?
more tortuous, larger blood vessel in mucosa, trigone elevated, deep and wider, reduced capacity
Why does the ureters become as reservoir for urine in pregnancy?
the capacity of the bladder (normal urine reservoir) reduces, ureters compensate
What percentage of women are effected by increased urinary output in pregnancy?
81%
What percentage of women are effected by nocturnal diuresis?
66% - overnight dilute urine
Oedema of lower extremities in pregnancy is caused by…
pressure impairing the drainage of blood and lymph - potential for trauma or infection
What percentage of women are effected by asymptomatic bacteriuria in percentage?
5%
Define asymptomatic bacteriuria
bacteria in urine without symptoms of infection
Define pyelonephritis
kidney and ureter inflammation due to infection
Why does blood pressure in the glomerulus need to be higher?
in order to generate a filtration pressure
What is the glomerular pressure in mmHg?
48mmHg
What does GFR stand for as a measurement?
the volume of filtrate production each minute
What does GFR indicate?
how well the kidneys are functioning based on
- creatinine clearance
- volume of urine and plasma
What is the process of tubular reabsorption?
selective reabsorption - selectively reabsorbs what the body needs and leaves the waste products
What does tubular secretion rely on?
transporter protein to actively move substances from the peri-tubular capillaries into tubular filtrate
Although tubular secretion appears opposite to tubular reabsorption, why is it just as important?
secretion can further lower plasma concentration of undesirable material
