Urinary System And The Adrenal Flashcards
How many lobes does a rat kidney have
1 - they are Unilobar
How many lobes does a human kidney have
8 - it is multilobar
Describe the lobar structure of the human kidney
It becomes indistinct on the surface at birth
Describe the kidney cortex
Has a profuse blood supply and contains units where ultrafiltration occurs
This is where the majority of reabsorption takes place
What are the units of the kidney cortex where ultrafiltration takes place
Malpighian/ renal corpuscles
Describe the renal medulla
Has a poorer blood supply that the cortex and contains tubules and blood vessels running in parallel bands
The medulla tapers down from the cortex to end in a blunt pyramid (the papilla)
True or false:
The number of cortical nephrons is much greater than that if juxtamedullary nephrons
True
How many nephrons are in the human kidney
1 million
What does each renal corpuscle consist of
A glomerulus and Bowman’s capsule
What does Bowman’s capsule consist of
2 epithelial layers with Bowman’s space between them
The inner epithelium is in close association with the glomerular capillaries and reflects at the vascular pole to form the parietal layer, which is continuous with the PCT
What forms the visceral layer of Bowman’s capsule
What about the parietal layer?
Podocytes
Squamous epithelium
Describe the podocytes of the inner epithelium of Bowman’s capsule
They have long cytoplasmic extensions (primary processes) that give rise to secondary foot processes, both of which embrace the capillary loops
What is the vascular pile of the renal corpuscle
Where the blood supply enters and leaves the glomerulus
What is the urinary pole
Where the PCT joins Bowman’s capsule
It is opposite the vascular pole
What distinguishes the PCT
A brush border
What is the macula densa
What does it look like in a LM
A distinct epithelial region found at the junction of the thick ascending limb and the DCT, closely opposing the glomerular vascular pole
Look for a distal tubule touching the outer glomerulus, showing many nuclei side by side or even overlapping
Which cells are the macula densa cells in contact with at the glomerular vascular pole
The extra glomerular mesangial cells
What does the macula densa do
Monitors the change in [NaCl] in tubular fluid
Mediates renin release by juxtaglomerular cells
What does the Mesangium consist of
Mesangial cells and mesangial matrix interposed between glomerular capillaries
The extra- and intraglomerular mesangial cells are continuous
What do mesangial cells do (5)
Produce mesangial matrix
They have contractile properties
provide structural support to the capillary network
Play an indirect role in glomerular filtration by regulating blood flow via endothelins
They are phagocytic and remove trapped residues and aggregated protein from capillary basement membrane to keep the filter free of debris
What is characteristic about where the renal papilla projects into the calyx
The presence of a high cuboidal epithelium, with no brush border and the lateral cells are distinctly visible with LM
What are the only tubules between the papillary ducts
Thin limbs of loops of Henle and capillaries
What does the glomerular barrier through which plasma is filtered consist of
Fenestrated capillary endothelium
A basement membrane
Podocyte layer
Describe the fenestrated layer of the filtration barrier of the glomerulus
Contains numerous fenestrations of ~50 -100nm in diameter
Describe the basement membrane of the filtration barrier of the glomerulus
Shared by endothelial and podocyte layer
Functions as a highly selective filter
Negatively charged meshwork of specialised extracellular matrix composed of type IV collagen, proteoglycans and glycoproteins
Describe the podocyte layer of the filtration barrier of the glomerulus
The podocytes have long branching foot like processes that encircle the glomerular capillary surface
The endings of the podocyte processes are separated by gaps (filtration slits) bridges by a thin porous diaphragm with pores of ~4-14nm
Which molecules are not easily filtered in the glomerulus
Negatively charged ones sir or the electrostatic repulsion by the negative charge of the basal lamina and podocyte layer
Where are umbrella cells found
Why do these cells contain vesicles
Urinary bladder
The vesicles are made up of plaques which fuse into the membrane when the area of the cell needs to increase to allow distension of the bladder
What are the layers of tissue in the bladder
Transitional epithelium
Lamina propria
Muscular coat (3 layers: inner longitudinal, middle circular and outer longitudinal)
Adventitia
What does the adrenal cortex secrete
Steroids:
Glucocorticoids
‘Mineralocorticoids
Sex hormones
What does the adrenal medulla secrete
Catecholamines
Eg adrenaline, noradrenaline, dopamine
What are the 3 layers of the adrenal cortex, from superficial to deep?
How much of the cortex does each take up
Zona glomerulosa (10-15%)
Zona fasciculate (75%)
Zona reticularis (5-10%)
What does the zona glomerulosa produce
What do these do
Eg
Mineralocorticoids
Regulate electrolyte and water balance
Eg aldosterone that promotes Na+ reabsorption in the kidney
What are steroid secreting cells characterised By
Numerous lipid droplets, mitochondria (with tubular cristae) and an extensive sER
Why do the steroid secreting cells have lots of mitochondria
Oxidation of fatty acids provides acetate for cholesterol synthesis by the sER
What 3 hormones are secreted by the kidney
Renin
1,25-DHCC
erythropoietin
What is 1,25-DHCC
1,25-dihydroxycholecalciferol
AKA: calcitriol
It is a hydroxylated derivative of vit D3
What is the juxtaglomerular apparatus made up of
The juxtaglomerular granular cells of the afferent arteriole
The extraglomerular mesangial cells
The macula densa
What do the juxtaglomerular cells do
They are modified smooth muscle cells that secrete renin
Where are extraglomerular mesangial cells found
They are found in the junction between afferent and efferent arterioles
What properties does the JGA have
Both chemoreceptor and baroreceptor properties
These are vital for control of GFR and renin secretion
What is ANP
When and where is it released
What does it do
Atrial natriuretic peptide
Released by atrial myocardial cells when distended as a result of increased blood volume
ANP promotes sodium excretion and inhibits production
Is the duct system more prominent in the salivary gland or pancreas
More prominent in salivary gland
What is a characteristic feature of secretory acini in the pancreas
They are composed exclusively of serous cells
The pancreas is a mixed exocrine and endocrine gland. Which component occupies most of the gland
Exocrine component
What are the exocrine components of the pancreas
The acini
What volume of the pancreas does the endocrine component make up
1-2%
These are the islets of Langerhans
What are secreted by the different cells of the islets of Langerhans
α cells: glucagon
β cells: insulin
Δ cells: somatostatin
F: pancreatic polypeptide
Why do pancreatic acinar cells have abundant rER
For protein synthesis
Name an endocrine function of the liver
Secretion of plasma proteins, lipoproteins and glucose into the space of Disse
