RENAL- Functional Histology of the Kidney Flashcards
what is the function of the kidney
homeostasis of blood
plasma composition - water, ions, organic waste products
blood pressure - through enzyme renin
erythrocyte content - secretion of erythropoietin
what is the functional unit of the kidney
the nephron - blood is filtered at a molecular level to produce urine - retains cells and large proteins - reabsorbs small molecules
describe the structure of the nephron
bowman capsules glomerulus proximal convoluted tubules loop of Henle -thin arm loop of Henle - thick arm distal convoluted tubule collecting tubule collecting duct papilla
what is the glomerulus
site of ultrafiltration - filtration / dialysis of blood through extremely fine molecular filter
what are the three layers of glomerular filter
cytoplasm of capillary endothelial cell of glomerulus
thick, fused basement membranes of capillary podocytes
what is the function of the proximal convoluted tubule
reabsorption from ultrafiltrate
active transport across membrane into the cell- small molecules like Na, glucose and amino acids
pinocytosis - macromolecules, broken down in lysosomes and returned to blood
passive influx - water, cl-
what is the structure of the renal tubule
long microvilli for high surface area, lytic enzymes on surface to break down macromolecules
pinocytotic vesicles carrying macromolecules to lysosomes
many mitochondria to duel active transport
what is the function of the loop of henle
reabsorption of water and salts from the filtrate
passive flux across the epithelium by osmosis and concentration gradients
what is the structure of the loop of henle
thin
squamous epithelium to allow passive flux
minimum of organelles
what is the function of the DCT
homeostasis by regulated active transport and exchange of ions (Na/K/H/HCO3)
what is the structure of the DCT
cuboidal epithelium - thicker than squamous to reduce passive flux and accommodate organelles
few, short microvilli
many mitochondria to fuel active transport
what are the functions of the collecting ducts
transport of urine to ureter
water homeostasis- passive reabsorption of water regulated through epithelial permeability
what is the structure of the collecting duct
cuboidal to columnal epithelium to prevent passive flux of water and urea
specialised dense membrane at cell contacts
what is the role of the macula densa
sensing Na in the DCT
what is the role of the juxtaglomerular cells
release renin - in response to lower Na in the DCT - renin indirectly increases vascular tone (blood pressure) and sodium resorption
name the cellular layers of the ureter
starting from inner - transitional epithelium
dense connective tissue (lamina propria)
layers of smooth muscle (peristalsis)
adventitia
describe some features of the transitional epithelium
only found in ureters and bladder
specialised - impermeable to urine (noxious)
changes appearance on stretching
what makes protects the cells from the toxic effects of urine
plaques of specialised (urine resistant) plasma membrane in apical cells of transitional epithelium
these plaques are made of transmembrane proteins called uroplakins
in a contracted bladder - the ridged plaques are invaginated forming irregular pits in the cytoplasm, allowing cell surface to decrease
what are the downside of the transitional epithelium
cystitis
urinary tract infections - the transitional epithelium are highly impermeable - leukocytes of the immune system cannot readily penetrate
why are UTIs common in women
female urethra is shorter
risk of contamination from anal region
how can UTI’s be prevented
plenty of fluids
