Kidney Flashcards
(9 cards)
Structure of kidney
1) Hilum (renal sinus):
it contains:
- Renal pelvis
- Renal blood vessels, lymphatic vessels, sympathetic nerves
- Renal pelvis divided into 2-3 major calyces, each of which divided into 3-4 minor calyces.
(2) Calyces:
- The collecting tubules open into a minor calyx as papillary ducts of bellini. The minor calyces
empty into major calyces which empty into renal pelvis to the ureter.
(3) Stroma:
- The kidney is covered with thin C.T. capsule which is attached to surrounding adipose C.T.
- There is no or little Septa
(4) Parenchyma:
- It is a large compound tubular gland which is highly vascular.
- It is formed of large number of uriniferous tubules. It is divided into:
• cortex It is outer dark granular region beneath the capsule.
It contains renal corpuscles, convoluted tubules, medullary rays
•Medulla
-It is inner radially striated region.
-The striations are due to the presence of loops of Henle, siraight collecting tubules
-The medulla consists of 10-18 medullary pyramids.
-The bases are oriented toward the cortex and their apices projects to hileum
What is
- medullary rays
- renal lobe
- renal lobule
- cortical column of bertin
Medullary rays:
- They are medullary projections that enter the cortex from the bases of renal pyramids. They
contain collecting tubules and ducts
- Renal lobe
Each lobe is formed of medullary pyramid and its associated cortex.
Renal lobule:
- It contains central medullary ray and the corresponding cortex.
Cortical columns of bertin:
• They are narrow cortical tissue between medullary pyramids.
Talk about the urinefrious tubules
Each kidney is formed of Uriniferous tubules.
- The uriniferous tubules are formed of;
a- Nephrons: They form and secrete urine.
b- Collecting tubules: they concentrate and excrete urine.
Talk about nephron
(10)
Each nephron is formed of:
• Renal malpighian corpuscle.
Each renal malpighian corpuscle is formed of:
1- Bowman’s capsule.
2- Glomerular capillaries.
3-Afferent and efferent arterioles.
4- Supporting mesangial cells.
Bowman capsule
-It surrounds the vascular glomerulus.
- It has an outer and an inner epithelial layers separated by Bowman’s or capsular space.
- The outer or parietal layer orurinary is lined with simple squamous epithelium
- The inner or vascular or visceral layer is lined with podocytes..
- They are termed podocytes because they have feet.
- Each podocyte is adherent to the outer surface of a glomerular blood capillary by means of
major and minor processes (Feet).
-The basement membranes of both podocytes and of the capillary endothelium are fused together to form a thick continuous basal lamina. 300 nm - The minor processes of podocytes are implanted on the basal lamina.
- There are minute areas between the implanted ends of these minor proceses, these areas of the basal lamina are called filtration slits.
- These filtration slits are covered by diaphragms and that play a role in filtration
Each malpighian renal corpuscle has vascular and urinary poles.
- Through the vascular pole an afferent arteriole enters the corpuscle where it divides into many
blood capillaries which are in contact with the podocytes. These capillaries then drain into an
efferent arteriole. And called glumorulas
Talk about juxta glomerulur complex ( appartus)
- It regulates bp and electrolyte balance.
- It is formed of macula densa, lacis cells and juxta glomerular cells.
Macula densa: (4)
• It is the part of the distal convoluted tubule with is in contact with the vascular
pole of a malpighian renal corpuscle.
•The cells of the distal convolute tubule at macula densa are columnar
•They rest on no basement membrane.
•Macula densa act as osmo-receptor cells for any decrease in sodium ion conc
Lacis cells or polar cushion or extra mesngaial cells (3)
they are cubical cells .
-They are present between the afferent and efferent arterioles and the macula densa.
- Phagocytosis
- Juxta glomerular cells: (3)
-They are epithelioid cells present in the media of the afferent arteriole.
- These cells act as mechano-receptors. They are stimulated in low blood pressure.
They secrete Renin Hormone.
- Functions of juxta glomerular complex:
1) It secretes rennin hormone which stimulates secretion of aldosterone
2) It also secretes erythropoietin factor which stimulates blood cell development from the
bone marrow.
Talk about renal blood capillaries
•The endothelium of these glomerular capillaries is fenestrated with pores which are not covered by diaphragms.
•Outside the endothelium of glomerular capillaries, there is a thick basement membrane formed of the following 3 layers:
a- A central dark layer called lamina densa.
b- An outer pale layer called lucida externa.
c- An inner pale layer called lucida interna.
•This basement membrane is essential for filtration selectivity. It is continually renewed by the mesangial cells.
The mesangial cells
They are adherent to the surface of glomerular blood capillaries.
Functions of Mesangial Cells:
1) They phagocytose the destructed old basement membrane and the foreign organism
2) They secrete supportive fibronectin substances needed for the renewal of glomerular basement membrane.
Talk about renal blood barrier
- The fenestrated simple squamous cells (endothelium) of the glomerular blood capillaries.
These fenestrated(pores) are not covered by diaphragms, through these pores blood plasma
and not blood cells can pass. - A continuous thick basal lamina (formed of fusion of the 2 basement membranes
of podocytes and of blood capillaries). - The (implanted feet) of podocytes with filtration slits between them which are
closed by slit diaphragms.
How many nephrins in one kidney
Around 1 million
What is the difference between afferent and efferent
•Lumen width is the same
•but diameter of afferent is larger
• due to thicker muscle layer to regulate hydrostatic pressure in glomerular capillaries.
