Microanatomy 3 Flashcards
what is the glomerular filtration barrier made up of
1, podcyte foot processes with filtration slit diaphragm
2, glomerular basement membrane
3, fenestrated endothelium of the capillary tuft
what causes glomerulonephritis
immune complex deposition int he glomerulus causes most types of glomerulonephritis
what is minimal change glomerulonephritis due to
- appears to be due to a cell mediated immune response
- happens to children under the age of 6 after a respiratory infection or immunisation
what form does damage to the glomerulus result in
- it elicits a glomerular response which may take one or more form these are
1. swelling and proliferation of the capillary endothelial cells
2, proliferation of the podocyte epithelial cells investing the glomerulus or parietal layer of the bowman capsule
3. thickening of the glomerular basement membrane
4, proliferation of cells of the mesangium and increased production of the mesangial matrix
what hisotlogical changes are shown due to glomerulonephritis
1, diffuse affecting all glomeruli
2, focal affecting some glomeruli
3, global the entire glomerulus is abnormal
4, segmental - only part of the glomerulus is abnormal
what is a percutaneous needle biopsy of the kidney
- this is a safe and reliable method to obtain tissue specimens for histopathological analysis in order to diagnose different forms of glomerulonephritis and other renal disease
what allows the differ nation between various forms and causes of glomerular disease
- immunofluorescence for immune and complement molecules
- electron micropscopy for various forms and causes of glomerular disease
what is acute proliferative glomerulonephritis
- this a diffuse (affecting all glomeruli) glomerulonephritis which most commonly occurs in children
- often present 1-4 weeks after a streptococcal infection of the pharynx or skin (impetigo) (other infections can cause it)
what is the hypercellularity of acute proliferative glomerulonephritis due to
- it is due to proliferation of endothelial and mesangial cells as well as infiltration by leucocytes mainly neutrophils
- endothelial swelling in addition to increased cellularity reduce the capillary lumina
how do you treat acute proliferative glomerulonephritis
95% of people recover totally with treatment aimed at maintaining water and sodium balance
describe what the glomerulus looks like in minimal change glomerulonephropahty
- podocyte foot processes are flattened onto the basement membrane
- immune complexes are absent
- selective proteinuria with mainly loss of albumin
how do you treat minimal change glomerulonephropathy
- treat with corticosteroid treatment
what causes the podocyte foot processes to flatten in minimal change glomerulonphropathy
- epithelial cell damage as a result of a number of insulting factors is through to cause podocyte cell foot processes to flatten
- results in a leaky glomerular filtration barrier
what is membranous glomerulopahty
- this is a form of chronic immune complex mediated disease and is a common cause of nephrotic syndrome in adults
- prepays due to autoimmunity and antibodies are reactive against a renal auto antigen, complement activation also plays a role and affects permeability of the glomerular filtration barrier
describe what membranous glomerulopathy looks like
- ## diffuse membrane thickening due to subepithelail deposition of electron dense immune complexes with thickens basement membrane spikes
what is the most common cause of end stage renal failure in the US and Europe
diabetes
what does glomerular disease manifest as first and then progress to
manifests first as proteinuria and then leads to nephrotic syndrome
what has a role in glomerular disease
- hyperglycaemia that you get in diabetes
how does hyperglycaemia from debates effect glumarul disease
- increases severity
- causes intimal capillary wall thickening
- mesangial matrix expansion
- diffuse diabetic glomerulosclerosis
- arterial atherosclerosis leading to the reduction in blood flow to the glomeruli
- this can lead to ischemia which leads to chronic renal failure
what is the most common primary kidney tumour
renal cell carincoma - this is an adenocarcinoma derived from tubular epithelial cells that accounts for 90% of kidney timorous
where is renal cell carincoma derived from
derived from tubular epithelial cells
what accounts for 5-10% of primary renal tumour
- transitional cell carcinomas which originate form the renal pelvis
- they are the most common malignant bladder tumour
where do transitional cell carcinomas originate from
- originate form the renal pelvis
describe nephroblastoma or wilms tumour
- rare
- children between age of 1-4 affected
- embryological origin
- called small round blue cell tumour
what do renal carcinomas have a tendency to do
invade the renal vein
where is transitional cell epithelium (uroepithelium) found
- it is only found in the urinary tract
describe transitional cell epithelium (uroepithelium)
- it is distended and urine cannot leak through it
- has a thick plasma membrane and plaques these all rounding and flattening of the cells which allow distension
- tight junctions between cells prohibit passage of water or other materials between the cells
what does transitional cell carcinoma often present with
- it often present with papillary growth
what can bladder cancer arise from
- transitional epithelium
- squamous epithelium
what diseases is membranous glomerulonephritis associated with
causes
Infective - Hep B, Malaria, syphulis
drug related - gold therapy, penicillamine, captorpil, heroin
tumour associated - bronchial carcinoma and lymphoma
autoimmune - systemic lupus erythematousus
what haematological abnormalities do you get as a result of renal cell carcinoma
anaemia
polycythameia - EPO production decreased
where else can papillary transitional cell carcinomas occur
anywhere transitional epithelium is found
- kidney
- bladder
- reuters
- prostatic urethra (men)
- proximal urthrea (women)
what are the functions of the urinary system
maintenance of water and electrolyte homeostasis by removing excesses via urine.
maintenance of acid-base balance by secretion of H+ into the urine.
excretion of many toxic metabolic waste products from the body, such as urea and creatinine.
participation in other homeostatic mechanisms of the body through endocrine pathways:
- blood pressure regulation through the production of renin and the renin-angiotensin-aldosterone mechanism.
- maintenance of the oxygen-carrying capacity of the blood through the production of erythropoietin which stimulates erythrocyte production in the bone marrow.
- regulation of calcium balance through conversion of vitamin D to its active form.
what does the urinary system consist of
- consist of two kidneys that produce urine
the accessory organs
- two ureters
- bladder
- urethra
what is the kidney
- bean shaped organ invested in a tough fibrous capsule
where is the hilum of the kidney found
. The hilum, found in the centre of the medially-directed concave face
what is the hilum of the kidney
is the site of entry and exit of its major vessels and the renal pelvis
what is the renal pelvis
the distended intimal portion of the ureter
how many lobes does the kidney have
10-18 lobes
what are the two parts that make up the kidney
- outer cortex
- inner medulla
what does the each lobe of the kidney consist of
Each lobe consists of a medullary pyramid (conical in shape) that is capped by the cortical components of each lobe
what is the medullary pyramid of the kidney surrounded by
The pointed, centrally-oriented part of the medullary pyramid (the renal papilla) is surrounded by a branch of the renal pelvis called a calyx, this forms the initial portions of the lower urinary tract
what is the functional unit of the kidney
nephrons
where do nephrons originate from
Nephrons, the functional units of the kidney, originate in the cortex and loop down into the medulla for variable distances before returning to the cortex and draining provisional urine into the collecting duct system. The collecting ducts then extend back into the medulla merging successively to form the largest ducts (papillary ductsor ducts of Bellini) that open into the calyce
what does the renal cortex contain
The renal cortex contains the renal corpuscles where ultrafiltration of plasma occurs and the tortuous or convoluted portions of the renal tubule system.
Some collecting ducts are visible in the cortex and are called ‘medullary rays’.
what does the renal medulla contain
The renal medulla contains the straight looping portions of the tubule system as well as the collecting ducts
what does the main renal artery divide into
posterior and anterior branches
interlobar arteries that run between the medullary pyramids
arcuate arteries that run laterally where the renal cortex abuts the medulla (the corticomedullary junction)
interlobular arteries running upwards into the cortical tissue
afferent arterioles
the glomeruli, tufts of capillary loops within the renal corpuscle where plasma filtration occurs
efferent arterioles
two secondary capillary plexuses which provide the blood supply to the parenchyma of the kidney:
what are the two secondary capillary plexus
the vasa recta
the cortical capillary network
describe the two secondary capillary plexus
The vasa recta. Arising from efferent arterioles of juxtamedullary glomeruli (in the cortex near the medulla), this capillary system runs straight down into the medulla and loops back on itself ultimately draining into the veins at the corticomedullary junction. As well as providing the blood supply to the medulla, the vasa recta, help to generate the high osmotic pressure in the medulla necessary for concentration of urine.
The cortical capillary network. Arising from the efferent arterioles in the rest of the cortex, these capillaries allow the exchange of materials between the blood and cortical tubules (eg. oxygen to tubular cells; molecules reabsorbed from the provisional urine to blood).
how many nephrons are there in each kidney
approximately 1 million
what does then nephron consist of
The renal corpuscle (Bowman’s capsule and the glomerulus within it) which is the site of filtration of the blood.
The renal tubule, which is a long folded duct that processes the filtrate. The last portion of the tubule empties into the collecting duct. Collecting ducts ultimately merge to form the large papillary ducts (of Bellini) that open at the tips of the renal papillae.
what does the renal corpuscle consist of
consists of Bowman’s capsule
is the site of filtration of the blood
what does the Bowmans capsules structure
The outer, capsular epithelium (the parietal wall) is simple squamous epithelium and may be thought of as the funnel portion of the renal tubule.
The inner, podocyte layer (the visceral wall) forms part of the filtration barrier between blood plasma and provisional urine formed in the urinary space. The podocytes are so-named because they have interdigitating cytoplasmic extensions or ‘foot processes’ apposed to the basement membrane surrounding the glomerular capillaries.
what happens if the podyctes are damaged
- this is a disorder in children called minimal change neuropathy
- results in excessive protein loss in the urine (mainly albumin) and nephrotic syndrome
- this is usually resolved spontaneously
what is the glomerulus
is a tuft of capillary loops enclosed by the visceral layer of Bowman’s capsule. The capillaries have a fenestrated endothelium which lacks diaphragms
what cells is the glomerulus supported by
mesangial cells
what do mesangial cells do
synthesise a connective tissue matrix (mesangium).
phagocytise any particles trapped on the endothelial side of the glomerular filtration barrier and maintain its basement membrane (see below).
control glomerular blood flow by contracting or relaxing to make the glomerular capillaries narrower or wider.
what is the glomerular filtration barrier formed by
the podocyte layer of Bowman’s capsule
the fenestrated endothelium of the glomerulus
a thick, negatively charged basement membrane shared between the two cellular components
name the 4 parts of the renal tubule
- proximal convoluted tubule
- loop of Henle
- distal convulsed tubule
- collecting tubule
what parts of the renal tubule are in the Cortex
- proximal and distal convoluted tubule
what parts of the renal tubule are in the medulla
thin and thick segments of the loop of gene
- collecting duct
- vasa recta
describe the structure of the Proximal convoluted tubule
begins at the urinary pole of the renal corpuscle
is continuous with the parietal layer of Bowman’s capsule
is the longest, most convoluted portion of the tubule
name the functions of the proximal convoluted tubule
Na+ undergoes active transport via a Na+-K+ ATPase into the basolateral spaces between cells and then into peritubular capillaries. The reabsorption of water and negatively charged ions is driven by the osmotic and electrical forces created. 70-80% of the water, sodium and chloride ions are reabsorbed from the filtrate in the proximal convoluted tubule.
Bicarbonate ions are reabsorbed with H+ ion secretion.
Almost 100% of amino acids and glucose is also recovered by facilitated diffusion (using carrier proteins) driven by co-transport of Na+.
Larger proteins and carbohydrates undergo endocytosis and are degraded by lysosomal enzymes into amino acids and simple sugars which can then diffuse from the cells
what is the epithelium and micro anatomy of the proximal convoluted tubule
is lined by simple cuboidal epithelial cells
abundant mitochondria
a prominent brush border of microvilli and basolateral interdigitations of the plasma membrane which increase surface area.
what is a difference between juxtamedullary nephrons and normal nephrons
juxtamedullary nephrons may have long Loops of Henle reaching far into the inner medulla whereas other nephrons generally only extend a short distance in the medulla.
what are the four segments of the loop of Henle
the pars recta (straight portion) of the proximal tubule extends into the outer medulla and is similar in morphology and function to the rest of the proximal tubule.
the thin descending limb, lined by simple squamous epithelium, travels a variable distance into the medulla.
the thin ascending limb, also lined by simple squamous epithelium, begins immediately after the tubule loops back on itself. This segment may be quite short.
the thick ascending limb is similar in structure to the distal convoluted tubule being simple cuboidal with basolateral interdigitations and abundant mitochondria reflecting its ability to actively transport ions. It extends back to the cortex and is continuous with the distal convoluted tubule.
what is the main function of the loop of Henle
- it forms a counter current multiplier mechanism
- this is in order to produce an increasing osmotic gradient from the cortex to the tip of the renal papilla
describe how the loop of Henle forms a counter current multiplier system
descending limb is permeable to water and urea, but less permeable to NaCl. Water which moves into the surrounding tissue is removed by the vasa recta. As the urine moves in this tubule it gains urea and loses water.
The thin ascending limb is permeable to NaCl but not to water.
The thick ascending limb actively transports NaCl out of the tubule but limits diffusion of most other molecules including water, ions and urea. A high solute concentration (high osmotic pressure) is generated and maintained in the medullary interstitium and the tubule fluid becomes hypotonic.
describe the microanatomy of the distal convoluted tubule
is lined by simple cuboidal epithelium with basolateral interdigitations and abundant mitochondria.
lacks the extensive brush border of the proximal tubule.
forms part of the juxtaglomerular apparatus found at the vascular pole of the renal corpuscl
describe the functions of the distal convoluted tubule
reabsorbs Na+ ions through coupled secretion of H+ or K+ ions into the tubular fluid, a process which requires the presence of the adrenal hormone aldosterone. By acidifying the urine the distal convoluted tubule plays an important role in acid-base balance.
normally is relatively impermeable to water. However in the presence of antidiuretic hormone (ADH) its permeability to water increases permitting concentration of the urine.
secretes ammonium ions and some drugs
forms part of the juxtaglomerular apparatus.
describe the microanatomy of the collecting tubule
is the final segment of the nephron.
It is lined by simple cuboidal epithelium of varied functions and morphologies that overlap with those of distal tubules and collecting ducts.
describe the structure of the collecting duct
begin in the renal cortex as medullary rays (portions of cortex resembling the medulla).
merge to form larger ducts in the medulla and ultimately the papillary ducts that empty urine into the renal calyces.
describe the microanatomy of the collecting ducts
are lined by simple columnar cells with distinct lateral plasma membranes due to reduced interdigitation of these membranes with neighbouring cells.
describe the functions of the collecting duct
have similar functions to the distal tubule:
1) concentration of urine in the presence of ADH (which also increases their permeability to water).
2) regulation of acid base balance through secretion of H+ and reabsorption of bicarbonate ions.
3) secretion of ammonia ions and some drugs.
are permeable to urea which may leave down its concentration gradient from concentrated urine, thereby aiding the maintenance of the high solute concentration of the medulla.
what is the juxtaglomerular apparatus important in
the systemic control of blood pressure and volume
where is the juxtaglomerular apparatus found in
complex found at the vascular pole of the renal corpuscle
what does the juxtaglomerular apparatus consist of
juxtaglomerular cells
- which are modified smooth muscle cells in the walls of the afferent arteriole that sense changes in blood pressure and secrete the enzyme renin.
the macula densa,
- a region of the distal tubule that associates with the glomerulus as it loops back into the cortex.
- The cells at the side of the distal tubule closest to glomerulus become taller, more densely packed and possess prominent nuclei.
- The cells of the macula densa are thought to be able to detect Na+ concentration changes in the distal tubule and relay this information to juxtaglomerular cells.
extraglomerular mesangial cells (lacis cells) which support the complex.
what does the urinary contract consist of
renal calyces into which the large collecting ducts in the medullary papillae discharge their urine
the renal pelvis in the hilum of the kidney
the ureter, a muscular tube which conveys the urine toward the bladder
the bladder which acts as a reservoir for urine and a pump that expels the urine during micturition
the urethra, through which urine is voided from the body
