Urinary System Flashcards
What are the 4 overall steps of the urinary system?
- a pair of kidneys produce urine
- a pair of ureters transport urine to the urinary bladder
- urinary bladder temporarily stores the urine
- urethra conducts urine to the exterior
What are functions of the kidney?
- produces urine
- eliminate nitrogenous waste (protein metabolism)
- maintains electrolytes and water balance
- releases renin for regulation of blood pressure
- releases erythropoietin for stimulation of RBC production
Where are the kidneys?
in the posterior abdominal wall behind the peritoneum on each side of the vertebral column (T12-L3)
What 4 parts of the abdomen do the kidneys occupy?
epigastric, hypochondriac, lumbar and umbilical regions
Why is the right kidney slightly lower than the left?
due to the presence of the liver
What is the left kidney closer to?
the median plate
What does the transpyloric plane pass through?
- upper part of the hilum of the right kidney
- lower part of the hilum of the left kidney
What are the 4 external features of the kidney?
- 2 poles (superior and inferior)
- 2 surfaces (anterior and posterior)
- 2 borders (medial and lateral)
- hilum
From the deepest to most superficial, what are the 4 capsules/coverings of the kidney?
- fibrous (true) capsule
- perirenal fat
- renal fascia (false capsule)
- pararenal fat
What passes through the kidney hilum from anterior to posterior?
- renal vein
- renal artery
- renal pelvis
Why is the true capsule of the kidney fibrous?
due to condensation of the organ stroma
What does the perirenal fat of the kidney do?
give support to the kidney
What are the 5 anterior relations of the right kidney?
- suprarenal area
- hepatic area
- duodenal area
- colic area
- jejunal area
What are the 6 anterior relations of the left kidney?
- suprarenal area
- gastric area
- splenic area
- pancreatic area
- colic area
- jejunal area
What are the 4 posterior muscle relations of both kidneys?
- diaphragm
- psoas major
- quadratus lumborum
- transversus abdominus
What are the posterior nerve relations of both kidneys?
subcostal, iliohypogastric and ilioinguinal nerves
What is the only difference between the posterior relations of both kidneys?
right kidney is related to 1 rib and the left is related to 2
What is the kidney proper composed of?
outer cortex and inner medulla
Where is the outer cortex of the kidney proper?
just below the renal capsule and extends between the renal pyramids and renal columns
What is the inner medulla of the kidney proper composed of?
5-11 dark conical masses called renal pyramids
What do the apices of renal pyramids form?
renal papillae that invaginate the minor calyces
What does a minor calyx do?
surround the renal papillae of each pyramid and collect urine from that pyramid
Where does the renal sinus open?
at the medial border of the kidney as hilus
What does the renal sinus contain?
- greater part of the renal pelvis, major and minor calyces
- renal vessels
- lymphatics and nerves
- fat
What is a nephron?
the structural and functional unit of the kidney
What does each nephron consist of?
a glomerulus and a tubule system
What is a glomerulus?
a tuft of capillaries surrounded by Bowman’s capsule
What does a renal tubular system consist of?
- PCT
- loop of Henle
- DCT
Where do collecting tubules begin?
from the DCT
Where do collecting ducts open?
on the apex of the renal papilla
What are the 3 main functions of nephrons?
- filtration of metabolic end products from the blood
- selective reabsorption of useful substances back into the blood
- secretion of some materials into renal tubules
What are the 2 types of nephron?
- cortical involved in sodium reabsorption
- juxtamedullary involved in water reabsorption
Where are renal corpuscles mainly found and what do they consist of?
found in the cortical arches and consist of capillaries and Bowman’s capsule
What is Bowman’s capsule made up of?
visceral and parietal layers and Bowman’s space
What is the vascular pole?
where the afferent and efferent arterioles enter and leave the glomerulus in the Bowman’s capsule
What structures are between the glomerular capillaries and Bowman’s space?
- flattened endothelium of the capillary
- continuous basement membrane
- foot plate of podocyte cells
How much filtrate is collected in Bowman’s space?
~170L (10% of total filtrate over 24h)
How much urine is formed in 24 hours?
1.5L
What is the main function of the PCT?
active reabsorption of:
- glucose and amino acids
- sodium, chloride and bicarbonate
- majority of water
What does the loop of Henle consist of?
a descending limb (thin segment) and ascending limb (thick segment)
What is the main function of the loop of Henle?
reabsorption of water, sodium and chloride
Where does the DCT begin?
from the vascular pole of the nephron
What is the main function of the DCT?
reabsorption of water, sodium and chloride
What is the blood supply of the kidney?
the renal artery, which is a direct branch of the abdominal aorta
What is the venous drainage of the kidney?
the renal vein into the inferior vena cava
What is the order of branching of the renal artery?
aorta → renal artery → segmental artery → interlobar artery → arcuate artery → cortical radiate artery → afferent arterioles
What is the juxtaglomerular apparatus involved in?
regulation of blood pressure
What are the 3 components of the juxtaglomerular apparatus?
- juxtaglomerular (JG) cells
- macula densa
- Lacis/Polkissen cells
What are JG cells?
modified smooth muscle cells present in the tunica media of the afferent arteriole at the point of contact with the DTC
What do JG cells secrete?
renin
What are JG cells sensitive to?
changes in blood pressure in the afferent arterioles
What is the macula densa?
a specialised region in the wall of the DCT that comes into contact with the JG cells
What is the macula densa sensitive to?
the concentration of sodium ions in the fluid present in the DCT
What are Lacis/Polkissen cells?
extraglomerular mesangial cells found at the vascular pole in close relationship with the macula densa
What are the 7 steps of the RAAS?
- kidneys sense a drop in blood pressure or low sodium levels
- renin is released into the bloodstream
- renin converts angiotensinogen (from the liver) into angiotensin I
- angiotensin-converting enzyme (ACE), mainly from the lungs, converts angiotensin I into angiotensin II, a powerful vasoconstrictor
- angiotensin II narrows blood vessels, raising blood pressure
- angiotensin II stimulates the adrenal glands to release aldosterone, a hormone that increases sodium and water reabsorption in the kidneys
- sodium and water retention raises blood volume, which helps restore blood pressure to normal
What is the ureter?
a narrow, thick-walled, expansile muscular tube that is 25cm in length and 3-4mm in diameter made up of an abdominal and pelvic part
What are the sites of anatomical constrictions in the ureter?
- pelviureteric junction
- pelvic brim where it crosses the common iliac artery
- utero-vesical junction i.e. where the ureter enters the bladder
What is the blood supply of the ureter?
the branches of all the arteries related to it (renal, testicular/ovarian, internal iliac, vesical, middle rectal, uterine)
Where is the urinary bladder?
in the anterior part of the lesser pelvis immediately behind the pubic symphysis
What are the posterior relations of the urinary bladder in males and females respectively?
- males - rectum
- females - anterior wall of vagina
What are the anterior relations of the urinary bladder?
muscles of the pelvic diaphragm and pelvic bone
What are the 3 external surfaces of the urinary bladder?
- superior
- posterior
- inferolateral
When are the rugae of the urianry bladder visible?
when the bladder is empty
What is the bladder trigone?
a triangular area at the base of the bladder bounded by the internal urethral meatus and the two ureteric orifices that has no rugae
What are the 3 components of the male urethra?
- prostatic urethra
- membranous urethra
- spongy urethra
What muscles are the internal and external urethral sphincters derived from respectively?
- internal - bladder musculature of trigonal region
- external - sphincter urethrae muscle
What are the internal and external urethral sphincters innervated by respectively?
- internal - sympathetic fibres (T11-L2)
- external - somatic fibres (S2-S4)
Describe the epithelium of the 5 parts of the nephron
- Bowman’s capsule - simple squamous epithelium
- PCT – simple cuboidal epithelium with a microvilli brush border
- loop of Henle – simple squamous epithelium (thin) and simple cuboidal epithelium (thick)
- DCT – simple cuboidal epithelium without microvilli
- collecting ducts – simple cuboidal to columnar epithelium
Describe the epithelium of the ureter and urinary bladder
transitional epithelium
What cells are in the epithelial layers of the ureter and bladder?
basal cells, intermediate cells and umbrella cells
