Histology Flashcards
what are the functions of the kidneys and urinary tract
maintain water and electrolyte homeostasis, body fluid osmolarity and acid base balance
excrete toxic metabolic waste products (urea and creatinine)
act as an endocrine gland producing renin and erythropoietin
what covers the kidney
thin but strong capsule of dense collagen fibres (is continuous with the connective tissue of the renal sinus)
what is the hilum of the kidney
site of entry of renal artery and exit of renal vein and ureter
what makes up the medulla
medullary pyramids with apices pointing towards the hilum (papillae) (where urine drops off into the minor calyx)
what is a lobe of the kidney
a medullary pyramid and its associated cortical tissue
where does the medulla gets its blood supply from
the cortex
what fills the renal sinus
fat
what is the nephron
the basic functional unit of the kidney
what makes up the nephron
renal corpuscle and renal tubules
what makes up the renal corpuscle
glomerulus (capillaries) and bowens capsule (cup of simple squamous epithelium at the end of the nephron that the capillaries invaginate into)
what is the function of the renal corpuscle
production and collection of glomerular filtrate
what supplies and drains the glomerulus
afferent (supplies) and efferent (drains) arteries
what are podocytes
specialised epithelium cells that line bowmans capsule (lie of top of the capillaries of the glomerulus)
how does blood get from the glomerulus capillaries to the tubules (aka what are the three layers of the glomerular filter)
- endothelium (is fenestrated)
- thick basal lamina
- pododcytes (pedicles which form filtration slits)
what is the mesagium
made of mesangial cells, is the stalk like core of the glomerulus
provides support and removal of debris within the renal corpuscle
what is the is the glomerular filrate rate
100-125 ml/min
what are the two poles of the renal corpuscle
vascular pole (where afferent/efferent arteries connect) urinary pole (where glomerular filtrate leaves)
what cells have a saw tooth appearance
podocytes
what is the role of the proximal convoluted tubule
reabsorption of water, proteins, amino acids, carbs and glucose
70% of sodium (active transport) and water (diffusion) is reabsorbed as is almost all amino acids and glucose (co-transport)
what is a PCT cell, what is it like
cell of the proximal tubule
cuboidal epithelial cell
has extensive brush border (microvilli) and invaginated basal lamina to increase SA
what makes up the medulla
parallel tubules, the loops of henle and the collecting ducts + looping vascular network
what lines the loop of henle
thick limbs- simple cuboidal epithelium
thin limbs- simple squamous epithelium
what are the parts of the loop of henle
thick descending limb (proximal straight tubule)
thin descending limb
thin ascending limb
thick ascending limb (distal straight tubule)
what is the role of the loop of henle
creation of the hyperosmotic environment in the medulla
what is hyperosmotic
a fluid having a great conc of solutes than a normal extracellular fluid (more salty), increased osmotic pressure (water moves into capillaries (like oncotic)
how does the loop of henle create and maintain a hyperosmotic interstitium
as permability to water and ion and active transport of ions varies in the different parts
explain the blood supply of the medulla
vasa recta- loops of thin vessels that come down from the cortex and then go back up
normal vessels going through would carry away the salts in the interstitium and reduce high osmotic gradient
what is the role of the distal convoluted tubule
acid base and water balance (absorption of water, Na and bicarbonate. excretion of K and H ions)
how do the proximal and distal convoluted tubules differ
distal has smaller/ lacks a microvillus border
distal small tubules that proximal
what controls the re absorption of Na in the distal convoluted tubule
aldosterone - causes greater Na+ and water retention (increases BP)
what controls the reabsorption of water
ADH
what joins into the collecting duct
connecting tubules
what forms medullary rays (stripes in medulla)
the straight segments of the proximal and distal tubules
the collecting ducts
how does ADH work
(from post pit)
increases the permeability of the collecting duct to water
in high ADH, because of the high salt content of the interstitial fluid, water passes through the lumen as is goes through the medulla
ADH= concentrated urine
what is the function of the collecting tubules and collecting ducts
controlled reabsorption of water under the control of ADH
carries urine out into calyces
describe the flow of urine
produce at renal papilla minor calyx major calyx renal pelvis ureter bladder urethera
what lines (almost) all of the conducting parts of the urinary tract
transitional epithelium (uroepithelium)
(cells at luminal surface are domed a.k.a umbrella cells)
highly IMpermeable
why does the epithelium of the conducting parts of the urinary system has variable thickness
to allow for different states of distention
what is below the epithelium of the conducting parts of the urinary system
lamina propria of connective tissue
2-3 layers of smooth muscle
what ganglia in the muscle of the bladder
parasympathetic from sacral spine (provide micturition relfex)
how long is the urethra in femaled
4cm
what lines the female urethra
transitional epithelium
stratified near its termination
what lines the male urethra
prostatic urethra- transitional epithelium
membranous urethra- stratified columnar
penile urethra- stratified columnar epithelium, becomes stratified squamous at tip
how long is the male urethra
20cm
prostatic (from bladder through prostate) 3-4cm
membranous (from prostate to bulb) 1cm
penile urethra 15cm
