Histology of renal system Flashcards
What is the urinary system composed of?
2 kidneys, 2 ureters.
1 urinary bladder.
1 urethra.
What are the functions of the urinary system?
Urine formation - filtration, secretion and reabsorption of fluid from renal corpuscles and tubules.
Excreting waste products.
Regulating water/salts, and therefore blood pressure.
Endocrine - erythropoietin, renin.
What is the parenchyma?
The functional part of the kidney, for filtering blood into urine.
There are two layers:
The renal cortex
The renal medulla, where there are 10-18 pyramids containing many tubules.
The nephrons are here.
What is the pathway of urine from the kidney?
Urine goes from the tubules into collecting ducts, then leaves via holes in the renal papilla.
The filtrate then travels via the minor calyx, then major calyx to the renal pelvis.
Urine goes down the ureters and into the bladders for storage until the need to excrete.
What is the nephron?
The functional unit of the kidney.
Comprised of the renal corpuscle and the tubular system.
Split into the cortex, which is mainly the glomerulus and convoluted tubules, and the medulla, which is the straight portions of tubules.
What is the renal corpuscle?
The glomerulus - capillary bed.
The glomerular/ Bowman’s capsule, collects from the glomerulus.
What is the tubular system of the nephron?
Proximal tubule, which is close to the renal corpuscle,, then goes to the Loop of Henle, which has a thin descending and thick descending limb.
Filtrate then goes to the distal tubule, then the collecting ducts, then the papillary duct and leaves the medulla.
What does the nephron system look like?
See picture.
What does the nephron look like grossly?
See picture.
There are red dots which are the glomerulus - the highly concentrated capillaries.
There are striations in the medulla, as there are lots of straight tubules.
What does the nephron look like histologically?
See picture.
The capsule is the supporting connective tissue on the outside of the kidney.
The cortex contains the glomeruli and Bowman’s capsule - the renal corpuscle.
The cortex may have medullary ray - tubes leading to the medulla.
The worm structures are convoluted tubules.
What is the structure in the red circle?
See picture.
The renal corpuscle.
This contains the glomerulus and Bowman’s capsule.
What are the components of the renal corpuscle?
The glomerulus - a fenestrated capillary network.
The Bowman’s capsule surrounding:
Parietal layer, simple squamous.
Visceral layer, podocytes.
The space between the layers is the Bowman’s space.
What is the flow of blood in the renal corpuscle?
Blood enters the glomerulus via the afferent arteriole.
Blood leaves via the efferent arteriole.
This maintains a high pressure in the capillaries, which aids the high volume of blood to be forced through the capillaries.
What does the renal corpuscle look like basically?
See picture.
The vascular pole is where the afferent and efferent arterioles are.
The urinary pole is where the filtrate foes to the PCT.
What does the renal corpuscle look like histologically?
See picture.
S is the parietal layer of the Bowman’s capsule, made from squamous epithelium, this becomes thicker and cuboidal when it goes to the PCT.
The capillaries are made from squamous endothelial cells.
What are the cells present in the glomerulus?
Endothelial cells
Podocytes
Mesangial cells
What are the endothelial cells in the glomerulus?
These are fenestrated and line the capillaries.
The holes allow components of the blood to filter through into the filtrate.
What are the podocytes?
Modified epithelial cells that are the visceral layer of the Bowman’s capsule.
Primary processes come from the cell body.
Secondary processes are pedicles, which have direct contact with the basement membrane.
What is the function of the podocytes?
Form interlocking structures - filtration slits - that allow the movement of water, ions, small molecules, but not proteins.
So provide an extra layer of filtration.
What is the slit diaphragm?
The capillaries prevent large molecules (e.g. RBCs) from passing.
The basement membrane blocks intermediate and negatively charged molecules (albumin).
Podocytes block the smaller molecules.
Only small positively charged ions can pass, so ultrafiltrate contains little protein.
What are the structures in this picture?
See picture.
A are the fenestrations of endothelial cells.
B is the basement membrane.
C are the foot/secondary process of the podocytes that creates the slit barrier.
D is the lumen of the capillary.
E is the glomerular filtrate.
What are the mesangial cells of the glomerulus?
Intra mesangial cells are inside the glomerulus, produce the matrix, have a contractile, supportive role to change the pressure in the glomerulus.
Continuous mesangium - supportive matrix and cells.
Extraglomerular, Lacis cells found in the juxtaglomerular apparatus, cause contraction.
What is the juxtaglomerular apparatus?
Formed where DCT comes close to afferent arteriole
Regulate blood pressure and filtration rates.
See picture.
What are the cells in the juxtaglomerular apparatus?
Macula densa
Juxtaglomerular cells
Lacis cells
Specialised for regulating blood pressure and filtration.
