Structure of the kidneys Flashcards
Which structures make up the upper urinary tract?
Two kidneys
Two ureters
Which structures make up the lower urinary tract?
One urinary bladder
One urethra
What are the functions of the kidneys? (4)
- Maintainance of homeostasis
- Site of production
- Regukare the fluid and electrolyte balance
- Hydroxylates vitamin D3 to its active form
How do the kidneys maintain homeostasis?
Through filtration, absorption, and secretion
What are kidneys the site of production of?
Renin (causes it to be considered part of the endocrine system)
Erythropoietin
What is the function of erythropoietin?
Stimulates production of red blood cells
Which other organ is responsible for the production and hydroxylation of vitamin D3?
The skin
What are the kidneys?
Reddish brown bean-shaped organs on each side of the vertebral column
What is the location of the kidneys?
Posterior abdominal wall, primary retroperitoneal
Why is the right kidney lower than the left?
Because of the location of the liver on the right side
What is the movement of the kidneys like?
Limited, about 3cm in vertical dimension
Why is the movement of the kidneys limited?
Because of the diaphragm’s location
What are the coverings of the kidneys? (4)
Fibrous capsule
Perirenal fat
Renal fascia
Pararenal fat
Which organs have a fibrous capsule?
Presnet in all organs, naming just changes
What is the purpose of the perirenal fat?
Separates the kidneys from the adrenal glands (suprarenal gland)
Where is the perirenal fat located?
Perirenal is also known as perinephric fat, and it is located directly around the kidney
What is the renal fascia?
A continuous layer of the abdominal fascia covers both the kidneys and the suprarenal glands
What is the pararenal fat?
The outermost layer, continuous with retroperitoneal fat
In the case of perirenal abscess or injured kidney what is the direction/path of pus or blood?
Towards the infrarenal space, every other region is covered with renal fascia.
Infrarenal space will end up accumulating in the pelvis
What determines the direction of pus or blood determined by in the case of a perirenal abscess or injured kidney?
Attachments of the renal fascia
Which kind of organs have no direct contact with the kidneys?
Intraperitoneal they are covered by the peritoneum, examples are the spleen and stomach
What kind of structure is the suprarenal gland? (intra, retro, infra)
Retroperitoneal –> direct contact with the kidneys
What kind of structure is the second part of the duodenum? (intra, retro, infra)
Retroperitoneal
What are the relations of the right kidney? (5)
Right suprarenal gland (direct contact)
2nd part of duodenum (direct contact)
Liver (not direct contact)
Colon (direct contact)
Small intestine (not direct contact)
What are the relations of the left kidney? (6)
Left suprarenal galnd (direct contact)
Stomach (not direct contact)
Spleen (not direct contact)
Tail of pancreas (direct contact)
Colon (direct contact)
Small intestine (not direct contact)
What are the structures superior to the kidneys?
Right kidney –> Right lobe of liver and suprarenal gland
Left kidney –> Spleen and suprarenal gland
What are the strictures anterior to the right kidney?
The right lobe of the liver
Right colic flexure
2nd part of duodenum
What are the structures anterior to the left kidney?
Spleen
Left colic flexure
Stomach
Pancreas
What are the structures posterior to the kidneys?
Diaphgram
Psoas major
Quadratus lamborum
What are the structures posterior to the right kidney?
The 12th rib
What are the structures posterior to the left kidney?
The 11th and 12th rib
What is the Psoas major?
The innermost muscle, closest to the vertebral column
What is the location of Quadratus Lamborum?
Lateral to the Psoas major
Why is the right kidney only in contact with the 12th rib?
Because of its lower location, due to the presence of the liver
What is the renal hilum?
The point of entrance/exit of the kidneys, arteries, veins and lymphatic vessels
At which level is the renal hilum found?
At the level of the transpyloric plane (L1/L2)
The renal hilum is part of the?
Renal sinus
What are the structures of the renal hilum starting from most anterior to most posterior?
Renal vein (most anterior)
Renal Artery
Ureter (most posterior)
What happens if there is one singular renal aretry?
It will be posterior to the renal vein and anterior to the ureter
What happens to the renal artery some times?
It divides into segmental arteries. Thus, there usually will be a renal artery anterior and posterior to the ureter
These variations are considered normal
What are the renal columns?
Extensions of cortex into medulla
What are the two internal structures of the kidney?
Cortex and medulla
What is the cortex?
The outermost part of the kidney
What is the medulla?
The innermost part of the kidney
What are the different structures of the cortex?
Renal corpuscles
Cortical labyrinth
Medullary rays
What is the cortical labyrinth made of?
Proximal convoluted tubule
Distal convoluted tubule
What are the medullary rays?
Continuation of the medulla they are considered collecting ducts
What are the two zones of the medulla?
Outer and inner zones
What are the structures of the outer zone of the medulla?
Collecting ducts
Loop of Henle
What are the structures of the inner zone of the medulla?
Papillary ducts
Deep loop of Henle
What is the function of the draining system of the kidneys?
To collect urine from the nephrons and pass it all the way to the ureter
What is the draining system of the kidneys like?
Collecting ducts
Papillary ducts of Bellini
Renal papilla
Minor calyx
Major calyx
Renal pelvis
Ureter
What is the purpose of collecting ducts?
Collect urine from nephrons
What is the epithelium like all the way up to the minor calyx?
Simple columnar
What is the start point of the ureter?
The minor calyx
What is significant about the minor calyx?
The first part of the uroepithelium, the start of transitional epithelium
What is special about the uroepithelium?
It has the ability to stretch
What is the renal pelvis?
The upper extended part of the ureter
How many nephrons are there in each kidney?
About 1 million in each kidney
What is special about the blood supply of the kidneys?
Very rich in vasculature
Kidneys receive about 25% of the cardiac output
What is the main blood supply to the kidneys?
Renal arterial blood supply
What kind of branch is the renal artery?
The lateral branch of the aorta
At what point does the renal artery enter the hilum of the kidneys?
L2
Which renal artery will be shorter and why?
The left renal artery will be shorter because the aorta is located slightly to the left
What is the path of the renal arterial blood supply?
Renal arteries –> segmental arteries –> lobar arteries –> interlobar arteries –> arcuate arteries –> interlobular arteries –> afferent arterioles –> glomerulus –> efferent arterioles
Where do the lobar arteries run?
Between the pyramids, supply the whole lobe
Where are the interlobar arteries located?
Between the lobes
Where are the arcuate arteries located?
Between the medulla and the cortex
Which arteries give rise to the interlobular?
Arcuate arteries
Where is the glomerulus?
Inside the Bowman’s capsule
Why are there afferent and efferent arterioles?
The glomerulus has no veins, so there are efferent arterioles inside
What is the path of the renal venous drainage?
Pertibular capillaries –> Interlobular veins –> Arcuate veins –> Interlobar veins –> Lobar veins –> Segmental veins –> Renal veins
Which veins drain into the left renal vein specifically? Why?
Left inferior phrenic vein
Left suprarenal vein
Left gonadal vein
They drain into the left because the left renal vein is further away from the IVC
What is the location of the IVC in relation to the renal veins?
More towards the right, so the right renal vein drains directly to IVC as it is closer to it
Where is the left renal vein located?
Between the superior mesenteric artery and aorta, higher pressure compared to the right renal vein
What is the pathological name of the renal vein entrapment syndrome?
Nutcracker syndrome
What is the Nutcracker syndrome?
Compression of the left renal vein at midline between the superior mesenteric and the abdominal aorta –> Increase of the hydrostatic pressure in the kidney
What are the clinical manifestations of the Nutcracker syndrome?
Hematouria / proteinuria
Left flank pain
Nausea and vomiting
Left testicular pain in men
What are juxtamedullary nephrons? What are they supplied by?
Deep nephrons, supplied by longer vessels known as vasa recta
What is a renal lobe?
Each medullary pyramid with its superimposed cortical part & adjacent regions of cortical columns
What is a renal lobule?
A group of nephrons draining into the same single collecting duct
What are the different structures that make up the nephron?
Renal corpuscle
Renal tubules
What are the two parts of the renal corpuscle?
Vascular pole
Urinary pole
What makes up the corpuscle?
Glomerulus
Bowman’s capsule
What is the glomerulus?
Tuft of fenestrated capillaries
What are the two layers of the Bowman’s capsule?
Visceral and parietal layers
What is the visceral layer of the Bowman’s capsule formed of?
Podocytes
What is the parietal layer of the Bowman’s capsule formed of?
Simple squamous epithelium
What are the renal tubules of the kidneys?
PCT
Loop of Henle
DCT
What structure marks the start of the urinary pole?
PCT
What is the space between the parietal and visceral layers?
The urinary space
What are the filtration barrier membranes of the renal corpuscle?
Fenestrated endothelial cells of the capillary
Thin layer of basal lamina
Visceral layer of Bowman’s capsule
What do two basal laminae form?
A basal membrane
Where is the filtration slit diaphragm located?
Why are they important?
Between the pedicels
Important for filtration capability
What is the fenestrated endothelium covered by?
Basal lamina
What is the epithelium of the PCT like?
Simple cuboidal epithelium, absorption and secretion functions
Why does the PCT have high profiles?
Due to its tortious structure, more of them in a cross section
What are the characteristics present on the PCT?
Brush border
Well-defined basement membrane
Few basally placed nuclei
Indistinct layer membrane (no clear boundaries)
A lot of mitochondria
Why do the PCTs have a lot of mitochondria?
They require a lot of energy for transport
What is the epithelium of the loop of Henle like?
Simple squamous epithelium
Why are there not a lot of mitochondria in the loop of Henle?
There are not a lot of mitochondria or organelles because of the passive movement or reabsorption, and not a lot of energy is required
What is the function of juxtamedullary nephrons?
Establishing the gradient of hypertonicity in the medullary interstitium
What do the juxtamedullary nephrons consist of?
Short thick descending limb
Long, thin, descending, and ascending limbs
Thick ascending limb
What is the epithelium of DCT like?
Simple cuboidal epithelium
What are the profiles of DCT like in comparison to PCT?
Less
What are the characteristics of the DCT epithelium?
Low cuboidal
Apical nuclei
Few short blunt microvilli
No brush border
Why do DCTs stain lighter than PCTs?
Not as many mitochondria, less eosinophilic
What are the components of the juxtaglomerular apparatus?
Macula densa
Juxtaglomerular granular cells
Extraglomerular mesangial cells
What is the macula densa?
Part of the DCT
What are the juxtaglomerular granular cells part of?
The afferent arterioles
What is the function of the juxtaglomerular apparatus?
Regulate blood flow to the kidney, according to the blood pressure
What are the kinds of collecting tubules?
Cortcical and medullary
Where are the cortical collecting ducts?
In medullary rays
Where are the medullary collecting ducts?
In the outer layer of the medulla
What is the epithelium of the collecting ducts?
Simple columnar, very clear borders
Aqua chorea, a lot of water reabsorbed
What are collecting tubules affected by?
ADH
