Urinary System Flashcards
What are the main functions of the kidneys?
+ Urine excretion
+ Endocrine organ
+ Homeostatic role controlling blood pressure, tissue osmolality, electrolyte & water balance, pH
What are the functions of the kidneys in regards to maintaining/maintenance?
Maintain: Blood/water homeostasis by production of urine
- i.e removal from circulating blood of excess water and electrolytes and toxic, metabolic waste products such as urea and creatinine
What are the functions of the kidneys in regards to monitoring/affecting?
Monitor/affect: acid/base balance by excreting hydrogen ions during acidosis or bicarbonate ions during alkalosis
What are the functions of the kidneys in regards to secretion?
Secrete:
Renin
- indirectly raises blood pressure
Erythropoietin
- accelerates red blood cell production
What is the function of ureters?
Conduct urine to the bladder, where it is stored
What is the function of the urethra?
For passage of urine out of the body
What is the anatomical position of the kidneys?
+ Lie one on each side on the posterior abdominal wall, high up under the diaphragm
+ Retroperitoneal
+ Encapsulated and protected by layers of fascia and fairly firm renal fat
What are the major structures within the kidneys?
\+ Papilla (opening into a Minor Calyx) \+ Pyramid in Medulla \+ Cortex, extending between medullary pyramids as a renal colum \+ Minor Calyx \+ Major Calyx \+ Renal Sinus \+ Ureter \+ Pelvis
What is the role of the pelvis in the kidneys?
The pelvis becomes the ureter that transports urine to the bladder
What is the relationship betwen the minor calyces and the major calyces?
The minor calyces converge on major calyces, which themelves form the renal pelvis at the hilum of the kidney
What does the nephron consist of?
\+ Renal corpuscule (glomerulus and Bowman's capsule) \+ Proximal convoluted tubule (PCT) \+ Loop of Henlé \+ Distal convoluted tubule (DCT) \+ Collecting duct
What are the two different types of nephron?
+ Juxtamedullary
+ Superficial cortical
What are functions/features of juxtamedullary nephrons?
+ Receive ~10% renal supply
+ Designed to concentrate urine
+ Glomeruli in inner corical regions; long nephron loops
+ Associated with vasa recta
What are the functions/features of superficial cortical nephrons?
+ Receive ~90% renal supply
+ Reabsorb large % of fluid that filters from vasculature
+ Glomeruli in outer cortical regions; short nephron loops
Where does the ureter in females pass in relation to surrounding structures?
+ Passes posteriotl to ovary
+ Passes lateral to cervix and vagina
What are features of the male urethra
+ Passes through the prostate into the penis
+ Longer than female urethra
+ Dual purpose; conduit for urine and semen ejaculation
What are the features of the walls of the ureters and bladder?
+ Essentially muscular
- peristaltic waves propel urine down the ureter
- bladder fills by relaxation of its muscular wall (known as DETRUSOR muscle)
How does emptying of the bladder occur?
By muscular (detrusor) contraction, aided by raised intra-abdominal pressure
Describe the epithelial lining of the ureter and bladder
Transitional epithelium or urothelium, which is “urine-proof” and allows distension:
- the cells are rounded and piled on top of each other, but flatten and spread out to cope with distension
Where does the ureterin males pass in relation to surrounding structures?
Passes posteriorly to bladder
The bladder and ureter contain what type of muscle?
Smooth and involuntary
- controlled autonomic (particularly PSNS)
- but external sphincter around urethra is striated and under voluntary control
What percentage of cardiac output does the kidney recieve?
20%
How effective is the proximal tubule (PT) in reabsorption?
Recovers ~2/3 of the fluid and up to 100% of some solutees filtered into renal tube by glomerulus
What are the features of the PT cells that allow it be effective in reabsorption ?
PT epithelial cells have apical microvilli that increase surface area and junctions between cells that are leaky to maximize free flow of water and dissolved solutes
What are the underlying mechanisms involved in reabsorption and sectretion?
+ Na reabsorption by PT is driven by the basolateral Na-K ATPase through co-transport with organic solutes in exchange for H+
+ Cl- absorption occurs principally in the later PT by the paracellular route or by a Cl- base exchanger
+ Water reabsorption occurs by osmosis, driven by influx of Na, Cl and solutes
Via what structure is reabsorbed fluid returned to the vasculature?
Via the peritubular network
What is micturition?
It is the ejection if urine frm the urinary bladder through the urethra to outside of the body
Where/when is there no modification of urine?
En route to or in bladder
What happens to formed urine?
Channeled by renal calyces and the renal sinus into ureters and conveyed to the urinary bladder, where it is stored until micturiton
What is the bladder?
+ Bladder is a hollow muscular organ that stores urine until micturition is convenient
+ Valves prevent urinary reflux into the ureters, whereas inner and outer sphincters control the outflow via the urethra
What are the functions of valves and sphincter in the urinary system?
Valves prevent urinary reflux into the ureters, whereas inner and outer sphincters control the outflow via the urethra
How are the outer and inner sphincters controlled?
+ Outer sphincter is under voluntary control
+ Inner sphincter and bladder contraction is controlled by spinal relfexes and the CNS
What is the capacity of the bladder?
~500ml
What does the filling of the bladder do?
+ Stretches its muscular wall and initates a spinal micturition reflex, which causes PS motor efferents to stimulate bladder contraction
How is micturition prevented?
Prevented by the CNS until the outer sphincter is relaxed voluntarily
Where is the bladder in males located in relation to surrounding structures?
+ Superior to the prostate
+ Anterior to the rectum
+ Extends upward from pelvis into lower abdomen
+ Just above and behind pubic bone
Where is the bladder in females located in relation to surrounding structures?
+ Inferior and anterior to the cervix and uterus
+ Anterior to the vagina
What are features of the female urethra?
+ Situated between the clitoris and the vagina
+ Shorter than male urethra
+ More prone to infections due to shorter length
