Renal anatomy Flashcards
role of renal system
maintain water and chemical balance in body by expelling excess water. salts, wastes of metabolism, toxins and drugs. Also has endocrine functions to produce EPO and renin
requirements of renal system
delivery system for blood
selective filtration system
filtrate recovery mechanism
system to remove filtrate from body
protection; ability to communicate
structure of renal system
2 kidneys, 2 ureters, urinary bladder, urethra, regulatory nerves and muscles
location of kidney
located between T12-L3 vertebrae and underneath 11th and 12th ribs.
Located on posterior abdominal wall covered on anterior side by peritoneum.
Surrounded by protective renal fat.
Right kidney slightly inferior because of liver
gross structure of kidney
fibrous capsule - outermost, protection
cortex - outer, renal columns between medullary pyramids
medulla - inner, divided into medullary pyramids, each pyramid ends in papilla
renal lobe
one emdullary pyramid and surrounding cortex
usually between 5 and 11 per kidney
path of urine out of kidney
urine drains from each papilla and collects in a calyx
calyxes join to form renal pelvis
pelvis narrows as it exits the hilum to become the ureter
ureters flow into bladder
urethra exits bladder
blood supply into the cortex
Abdominal aorta –> renal artery –> Series of arteries –> afferent arteriole –> glomerular capillary
blood flow away from cortex after being filtered
Glomerular capillary –> efferent arteriole –> peritubular capillaries –> series of veins –> renal vein –> inferior vena cava
peritubular capillaries
specialised for absorption
adjacent to renal tubules
at low pressure and porous
innervation of kidneys
innervated by a network of autonomic nerves and ganglia called renal plexus
supplied by sympathetic nerve fibres from splanchnic nerves
determines diameter of renal arterioles so regulates blood flow
what is a nephron and functions
microscopic functional unit of kidney
functions are:
- filter blood
- reabsorb certain substances
- secrete into filtrate
- excrete waste
cortical nephron
85% of nephrons
Lie mainly in the cortex - do not extend far into the medulla
juxtamedullary nephrons
Extend deep into the medulla
Important for the formation of concentrated urine - the deeper a nephron penetrates into the medulla, the more concentrated the urine it will produce.
Their loop of Henle’s are associated with a vasa recta
structure of nephron
bowman’s capsule - filtration
proximal convoluted tubule - bulk reabsorption
loop of Henle - HOMG
distal convoluted tubule - fine tuning
collecting duct
glomerular capillaries
Specialised for filtration
Thin walled single layer of fenestrated endothelial cells
Fed and drained by arterioles
High pressure and tightly regulated
two layers of Bowman’s capsule
- Outer parietal layer of simple squamous epithelium
- Inner visceral layer of podocytes
Between two layers is Bowman’s space
podocytes
Surround glomerular capillaries
Very branched, specialised epithelium
Branches form intertwining foot processes called pedicels
Filtration slits form between pedicels
Filtered blood goes through these slits and passes into Bowman’s space
filtration barrier
Lies between blood and Bowman’s space
Allows free passage of water and small molecules
Restricts passage of most proteins
RBCs are not filtered into nephron
3 layers of filtration barrier
- Fenestrated endothelium of glomerular capillaries
- Fused basement membrane of glomerular capillaries and podocytes
- Filtration slits between pedicels of the podocytes
structure and function of proximal convoluted tubule
Cuboidal epithelial cells
Brush border (dense microvilli) on the luminal membrane
Highly folded basolateral membrane
Many mitochondria for active transport
Leaky epithelium to facilitate bulk reabsorption
function = bulk reabsorption
structure and function of thick ascending limb of LoH
Structure: similar to PCT (cuboidal epithelial cells with a brush border on the luminal surface, a highly folded basolateral membrane, and many mitochondria)
Function: reabsorption of water from filtrate
structure and function of thin descending limb of LoH
simple squamous epithelium
reabsorption of water from filtrate
structure and function on thin ascending limb
simple squamous epithelium
reabsorption of salt (NaCl) from filtrate
structure and function of thick ascending limb
similar to DCT (thinner cuboidal epithelial cells with no
brush border, and fewer mitochondria than the PCT)
reabsorption of salt (NaCl) from filtrate
distal convoluted tubule
cuboidal epithelial cells but thinner than those in PCT
few microvilli - no brush border
fewer mitochondria than PCT
function of DCT
reabsorption of various substances - fine tuning influenced by aldosterone
structure of collecting duct
wall of simple cuboidal epithelial cells - 2 types:
- principal cells - reabsorption
- intercalated cells - acid/base balance
filtrate from several DCTs drains into one collecting duct, which then empties into a papilla
function of collecting duct
fine tuning of urine
Reabsorption is influenced by antidiuretic hormone (ADH) through the use of aquaporins
juxtaglomerular apparatus
specialised zone in every nephron, located where the
DCT lies against the afferent arteriole.
Both vessels have specialised cells that control the glomerular filtration rate (GFR).
stabilises blood pressure
juxtaglomerular cells
found on afferent arteriole
mechanoreceptors
release renin in response to BP, which stimulates formation of angiotensin II
macula densa
found on DCT
chemoreceptors
sense NaCl concentrations
transitional epithelium
epithelium of urinary system
specialised type of stratified epithelium
It is made up rounded cells that flatten when they are stretched
Transitional epithelium functions to protect the structures that it lines
3 layers of ureters
- transitional epithelium - innermost
- muscularis - inner = longitudinal, outer = circular
- adventita - outer, FCT
also have protein plaques on luminal surface
entry of ureters into bladder
Enter bladder at an oblique angle, which acts as a sphincter/valve as it can be compressed by increased bladder pressure when full to prevent backflow
exit of ureters from kidney
Arise from each renal pelvis at each hilum
Descend retroperitoneally through abdomen, vertically from hila
triangular region between 3 openings of bladder
trigone - often does not fully empty so prone to infection
expansion of bladder
When empty the bladder collapses along folds or rugae
When full, the bladder expands without great increase in pressure
features of empty bladder
pyramidal
lies in pelvis
features of full bladder
more spherical
expands superiorly into abdominal cavity
location of bladder in males and females
males: anterior to rectum, superior to prostate
females: anterior to vagina and uterus
3 layers of bladder wall
- transitional epithelium
- detrusor muscle
- adventitia
detrusor muscle
specialised type of smooth muscle that squeezes urine from the bladder during urination
It is composed of longitudinal, circular and oblique fibres in a disorganised arrangement
urethra
thin-walled muscular tube that drains urine from the body and expels it out of the body
changes in epithelium in urethra
Transitional epithelium near the bladder
Columnar epithelium in the middle
Stratified squamous epithelium near the external opening - for protection
2 urethral sphincters
internal urethral sphincter - junction of bladder and urethra, detrusor muscle under parasympathetic control (involuntary)
external urethral sphincter - where urethra passes through urogenital diaphragm, skeletal muscle under somatic control (voluntary)
urination reflex
Bladder fills with urine and expands
AP to brain
Urgency increases as signals increase
Inner sphincter relaxes
Conscious relaxation of external sphincter
Issues with control - pregnancy, other issues leading to incontinence
male urethra
longer (25cm)
part of reproductive system
3 sections: prostatic, membranous, spongy/penile
urethra in females
shorter (5cm)
separate from reproductive system
