Flashcards in Kidney Anatomy, Embryology and Physiology Deck (137)
which horizontal plane crosses both kidneys?
at which vertebral level does the transpyloric plane lie?
what vertebral levels do the kidneys occupy?
at which vertebral level do the renal arteries come off the abdominal aorta?
what are the relations of the R kidney from top to bottom?
- R adrenal gland
- ascending colon
what are the relations of the L kidney from top to bottom?
- L adrenal gland
- small intestine
- descending colon
what are some of the main structures that the transpyloric plane passes through?
- kidney hilum (L and R)
- pylorus of stomaach
- neck of pancreas
- start of duodenum and duodenal flexure
- start of superior mesenteric artery
- end of spinal cord
what are the posterior relations of both kidneys?
- psoas major muscle
- quadratus lumborum muscle
what are the 5 segments of each kidney?
- A: apical
- AS: antero-superior
- AI: antero-inferior
- I: inferior
- P: posterior
what are the different layers and coverings around the kidney, in their exact order?
- renal capsule
- perirenal fat
- renal fascia
- pararenal fat
what is the renal fascia made up of and what is its purpose?
fibrofatty tissue, attaches the kidneys to the anterior body wall
what is the purpose of the peri and pararenal fat?
protection for kidneys
what are the main structural areas in the kidney?
cortex and medulla
what structures are found in the cortex of the kidney?
renal corpuscles, proximal and distal convoluted tubules
what are the renal corpuscles composed of?
glomerulus + Bowman's capsule
histologically, how can the kidney cortex be identified?
through the presence of renal corpuscles and convoluted tubules
what structures are found in the medulla of the kidney?
Loops of Henle and collecting ducts
what constitutes a nephron?
collection of renal corpuscles and convoluted tubules (+loop of Henle)
why is the right kidney lower than the left kidney?
because the liver takes up the space higher up
in what order do the main structures enter and exit the hilum of the kidney?
- renal vein
- renal artery
- renal pelvis/ureter
how are the kidneys peritonised?
retroperitoneal, but covered by peritoneum in the areas which come into contact with peritonised structures (eg liver, small intestine, stomach and spleen)
what is another name for the renal fascia?
what are two common congenital anomalies in the kidneys?
- double ureter
- horseshoe kidney
in the kidney, what is the name for the areas of cortex that project towards the hilum of the kidney?
what are the areas of renal medulla in between renal columns called?
what structures are contained in renal pyramids?
loops of Henle and collecting ducts
what is the course of waste products from the collecting ducts in the kidney to the ureters?
- pyramids to minor calyces (through papillae)
- minod calyces to major calyces
- major calyces to renal pelvis
- renal pelvis to ureter
how is the renal medulla arranged structurally?
in pyramids containing loops of Henle and collecting ducts, sitting in between renal columns
what are the layers of Bowman's capsule?
parietal and visceral layers of Bowman's capsule
what is found between the visceral and parietal layers of Bowman's capsule, and what is contained in it?
Bowman's space - contains filtered plasma from the blood in the glomerulus
what is found inside each Bowman's capsule in the kidney?
what are the important areas of narrowing in the course of the ureters, and why are they relevant?
1. narrowing at renal pelvis; 2. crossing over the iliac arteries; 3. narrowing at urinary bladder
- common areas of obstruction for renal calculi
which blood vessel coming from the kidney passes in front of the abdominal aorta?
left renal vein
what are the four main structures in the urinary system?
- urinary bladder
what are the 5 main functions of the urinary system?
- excretion of waste products through plasma filtration
- reabsorption of important molecules
- plasma electrolyte and BP control (through RAAS)
- pH control
- erythropoietin production
which nerves are closely related to the posterior aspect of the kidney?
- 12th subcostal nerve
- iliohypogastric nerve
- ilioinguinal nerve
which blood vessel coming up from the pelvis drains into the left renal vein?
left testicular vein
where do the testicular veins drain?
R into IVC
L into L renal vein
what structures pass over the ureter in males and females?
males: vas deferens
females: uterine/ovarian vein
what is the blood supply to the kidneys?
what happens to the renal artery once it reaches the hilum of the kidney?
it divides in 5 segmental branches
how are the segmental branches of the renal artery arranged in the kidney?
interlobar branches, arcuate branches and interlobular branches
what is the name for the branches of the renal arteries that supply individual nephrons?
what blood vessels drain the kidneys?
where does the nerve supply for the kidneys come from?
afferent sensory: T12-L2
which lymph nodes drain the kidney?
left lateral aortic lymph nodes
right lateral caval lymph nodes
what type of tissue makes up the majority of the urinary bladder wall?
what is the name of the smooth muscle found in the urinary bladder?
what is the trigone of the urinary bladder?
a flat area of the bladder found between the openings of the ureters and the opening of the urethra
what type of epithelium covers the urinary bladder and the ureters?
what is the characteristic of transitional epithelium?
it's able to expand as necessary whilst being very tightly arranged to keep urine in
on which aspect of the bladder are the ureteric and urethral openings found?
ureteric - posterior
urethral - inferior
what attaches the apex of the bladder the anterior body wall?
median umbilical ligament
what is the embryonic derivation of the median umbilical ligament?
embryonic urachus (remnant of allantois)
how is the urinary bladder peritonised?
only superior surface peritonised
what is the recto-uterine pouch, other names for it and what is its clinical significance?
aka Douglas' pouch;
lowest fold of peritoneum, found between the bladder and the rectum;
common spreading site for pus, infection and tumours, and can be used in peritoneal dialysis
which sex has a longer urethra?
males have a longer urethra
what are the four sections of the male urethra?
- preprostatic (intramural)
- membranous (intermediate)
- spongy (penile)
what is the longest section of the male urethra?
the spongy/penile part
what is the widest section of the male urethra?
the prostatic part
what is the narrowest section of the male urethra?
the membranous part
in the female urethra, what is the nerve supply of the internal and external urethral sphincter?
external urethral sphincter: somatic control, S2-S4
internal urethral sphincter: sympathetic control, T12-L1
what is the nerve supply of the detrusor muscle?
parasympathetic control: pelvic splanchnic nerves (S2-S4)
sympathetic control (T10 - L2)
what is found at the beginning of the spongy part of the male urethra?
opening of the ejaculatory duct
what is the average length of the male urethra?
what fibres carry pain sensation from the urinary bladder?
parasympathetic fibres (S2-S4)
what is the name of the somatic nerve supply to the urinary bladder?
pudental nerve (S2-S4)
what is the blood supply and drainage of the urinary bladder?
branches of the internal iliac arteries and veins
where does the lymphatic drainage of the urinary bladder go to first?
internal and external iliac lymph nodes
why does the sympathetic system control the internal urethral sphincter?
because it also controls ejaculation, therefore in males it can block off the bladder from the urethra to allow for ejaculation from the ejaculatory duct
what happens to the male urethra in the prostatic part?
it is joined by the ejaculatory duct
what is the ejaculatory duct made up of?
vas deferens + seminal vesicle
which nerve causes detrusor muscle contraction during urination?
parasympathetic nerves from S2-S4
what is the uriniferous tubule made up of?
nephron + collecting duct
which types of cells make up the parietal and visceral layers of Bowman's capsule?
parietal layer: simple squamous epithelium
visceral layer: podocytes
on a histological slide, how can a ureter be identified?
it looks like a circular tube with a star-shaped lumen with transitional epithelium and smooth muscle
what are the main physiological processes involved in the kidneys?
what is the average percentage of blood volume that is distributed to the kidneys?
what is the average GFR for kidneys?
what percentage of renal blood flow is filtered through the glomeruli into Bowman's capsule?
what basic physical principles govern the glomerular filtration rate?
Starling forces: hydrostatic and oncotic pressure
how does each Starling law affect the movement of plasma in and out of the nephron?
hydrostatic forces - promote filtration
oncotic forces - promote reabsorption
what are the three layers in the glomerulus which assist the highly controlled filtration of substances?
- fenestrated endothelium of capillary
- basal lamina of capillary
- slit membrane of podocyte
what are the structural and functional characteristics of the afferent and efferent arterioles in the glomerulus?
afferent arteriole: wide and short (high pressure, low resistance)
efferent arteriole: narrow and long (low pressure, high resistance)
which Starling force is highest at the glomerular capillaries?
how does the shape/size of the glomerular afferent and efferent capillaries affect filtration?
increased resistance of the efferent arteriole, added to the high pressure from the wide/short afferent arteriole, contribute to maintaining increased hydrostatic pressure in the glomerular capillaries, promoting filtration into Bowman's space
what is the only physical mechanism which occurs at the glomerulus of the kidney?
what are the extrinsic factors that affect GFR?
- sympathetic system
- circulating catecholamines
- angiotensin II
how does the sympathetic system affect GFR?
constricts afferent and efferent arterioles
has higher sensitivity for afferent arterioles
how do circulating catecholamines affect GFR?
constrict mainly afferent arterioles
how does angiotensin II affect GFR?
- constricts efferent arterioles if glomerular pressure too low
- constricts efferent and afferent arterioles if glomerular pressure too high
what is the intrinsic action of the kidneys to autoregulate the GFR?
automatic afferent arteriole constriction if MAP rises too much, and dilatation if MAP drops
at which range of MAP does autoregulation of GFR work best?
why is autoregulation of GFR important?
because it acts independently of neural or hormonal input
below what blood pressure does GFR stop altogether?
how would a haemorrhage affect GFR?
during a haemorrhage, extrinsic control of GFR would override autoregulation of the glomerular activity, therefore reducing blood flow to the kidney and redirecting it to more immediately important organs
how do peritubular capillaries promote reabsorption?
through being long and narrow they maintain high resistance, therefore causing a drop in hydrostatic pressure which then becomes lower than oncotic pressure, driving molecules back into the capillaries
why is oncotic pressure higher in peritubular capillaries?
because 20% of plasma has been filtered into Bowman's capsule, therefore there is a higher concentration of plasma proteins in the peritubular capillaries drawing fluid back in
what are the two main forces causing reabsorption in the nephron, and how do they achieve it?
- reduced hydrostatic pressure due to long narrow peritubular capillaries
- increased oncotic pressure due to filtered plasma causing high plasma protein concentration left over in capillaries
what facilitates reabsorption of substances from the renal convoluted tubules?
through carrier mediated transport mechanisms (eg ion channels and carrier proteins)
what determines the amount of particles that are reabsorbed from the kidney tubules?
the maximum transport capacity (Tm)
what is the renal threshold?
plasma threshold at which saturation of transport molecules occurs
how do the kidneys ensure that valuable molecules (eg glucose and amino acids) are always reabsorbed in full?
Tm threshold for that molecules is higher than its average plasma concentration
how do the kidneys regulate the amount of plasma phosphate and potassium?
they have a Tm threshold equal to the normal plasma concentration of potassium and phosphate, therefore any excess amount is not reabsorbed after filtration
where does the majority of sodium transport occur in the kidney?
in the proximal convoluted tubule
what mechanisms are used for sodium reabsorption from the kidney tubules?
active transport out of tubular cells
passive transport from tubule into tubular cells
how does PTH reduce reabsorption?
through reducing the amount of available transport channels
what happens to other molecules as a result of active sodium transport out of the tubules?
chloride and water follow out of the tubule
how is glucose transport dependent on sodium transport out of the renal tubules?
glucose is transported into the tubule cells through SGLT, which is a symport molecule which only transports glucose in presence of sodium
how are the kidneys able to excrete drug and toxic metabolites?
because the carrier transporters in the tubule cells are not very specific, so drugs and toxins fit into the same transporters that allow other organic molecules through
where in the nephrons does secretion of toxic metabolites occur?
in the proximal tubule
how is the reabsorption of sodium in the proximal tubule of the nephron increased?
by increasing surface volume with lots of villi, and large numbers of sodium channels
where is the majority of potassium reabsorbed from the nephron?
in the proximal tubule
where does most secretion of electrolytes occur in the nephron?
in the distal tubule
what does the secretion of potassium depend on in the tubule?
depends on the levels of potassium in the tubular cells
what is the basic principle of the counter current multiplier in the loop of Henle?
removal of sodium from ascending limb
removal from water at descending limb
what is the range of osmolarity in the renal medullary interstitium from the top of the loop of Henle to the deepest part?
300mOsm - 1200-1400mOsm
where is the loop of Henle permeable to water in the loop of Henle?
in the descending part
how does loss of sodium at the ascending limb of the loop of Henle affect the filtrate?
renders it more diluted
what is the osmolarity of filtrate when it reaches the distal tubule?
it's hypo-osmotic - 100mOsm
what is the overall purpose of the counter current multiplier in the loop of Henle?
it maintains a steep osmotic gradient for concentration of filtrate
what is the maximum osmotic difference achieved as the filtrate progresses down the loop of Henle?
200mOsm difference at a time
what types of channels are present or lacking in the descending limb of the loop of Henle?
lots of aquaporin channels, few sodium chloride channels
what types of channels are present or lacking in the ascending limb of the loop of Henle?
lots of sodium chloride channels, very few aquaporin channels
what is the main determinant of the counter current multiplier system?
sodium chloride reabsorption at the ascending limb
where in the hypothalamus is ADH secreted?
supraoptic (SO) and paraventricular (PVN) nuclei
what controls the release of ADH from the posterior pituitary?
osmoreceptors with stretch-sensitive ion channels in hypothalamus
what triggers the release of ADH from the posterior pituitary?
increase in plasma osmolarity
how does ADH promote reabsorption of water from the collecting duct of the nephron?
through increasing expression of aquaporins on the lumen surface of the tubular cells
why is urea reabsorption important along with ADH secretion in the collecting duct?
because it helps the body retain more water by being reabsorbed and further concentrating the urine in the collecting duct
where are the low pressure baroreceptors located?
in the atria and great veins
where are the high pressure baroreceptors located?
in the carotid sinus and aortic arch
how do low pressure baroreceptors in the atria and great veins trigger ADH secretion?
by reducing their inhibitory firing to ADH neurons
what is the effect of alcohol on ADH?
suppresses its secretion, causing more water to be kept in collecting duct
how is continence maintained by neural controls?
sympathetic system maintains detrusor relaxation and internal urethral sphincter contraction; voluntary contraction of external urethral sphincter
how is voiding of urinary bladder achieved?
parasympathetic system causes detrusor contraction and internal urethral sphincter relaxation; voluntary relaxation of external urethral sphincter