Histology

Question 1

3 functions of kidney and urinary tract?

Answer 1

maintain water and electrolyte homeostasis, body fluid osmolality and acid-base balance
excrete toxic metabolic waste products (urea and creatinine)
acts as an endocrine gland producing renin and erythropoietin

Question 2

what is erythropoietin

Answer 2

related to RBC production and maintainance

Question 3

what are the papillae?

Answer 3

apices of medullary pyramids which point towards the hilum, ending on the minor calyces

Question 4

at what point does urine drip off from the kidney/

Answer 4

papillae

Question 5

what are the renal columns?

Answer 5

acts as conduit for renal blood supply

give structure

Question 6

blood supply to the kidneys?

Answer 6

arteries enter and travel up through renal columns to supply the renal capsule
the medulla receives its supply from the capsule

Question 7

basic functional unit of the kidney?

Answer 7

nephron

Question 8

what are nephrons composed of and how long are they?

Answer 8

renal corpuscle and renal tubules

each is around 45-65mm long

Question 9

nephrons empty into what?

Answer 9

collecting system

Question 10

what does the renal corpuscle do?

Answer 10

production and collection of glomerular filtrate

Question 11

structure of the renal corpuscle?

Answer 11

formed of a tuft of capillaries called the glomerulus and the cup of simple squamous epithelium at the blind end of the nephron which the capillaries invaginate into called bowmans capsule

Question 12

how does the renal corpuscle develop?

Answer 12

tuft of capillarie envaginate into bowmans capsule (cup of squamous epithelium)
coating the capillaries in the epithelium

Question 13

what 2 cell layers separate the blood from the glomerular filtrate?

Answer 13

capillary endothelium and a specialised epithelium which lies on top of the glomerular capillaries (made of podocytes)
the endothelium is fenestrated with pores and the podocytes have interdigiting cell processes forming filtration slits

Question 14

how much glomerular filtrate is produced per minute? how does this compare to urine production?

Answer 14

100-125ml/min

only 1ml/min of urine

Question 15

afferent vs efferent arteriole?

Answer 15

afferent is larger as some volume is lost from capillaries at bowmans capsule

Question 16

vascular vs urinary pole of glomerulus?

Answer 16

the beginning of the proximal renal tubule is opposite where the afferent and efferent arterioles enter and leave bowmans capsule
= vascular end and urinary pole

Question 17

what is the mesangium?

Answer 17

stalk like core of the renal corpuscle made of mesangial cells and their extracellular matrix

Question 18

what are podocytes?

Answer 18

cells which cover most of the capillary surface within the glomerulus

Question 19

structure of podocytes?

Answer 19

branch in large branches, then small brnaches, then small foot branches called pedicles which intertwine to form filtration slits for glomerular filtration

Question 20

filtrate from the capillaries must cross what 3 layers?

Answer 20

fenestrated endothelium of the capillary wall
thick basement membrane shared by endothelium and podocyte)
filtration slits between pedicles

Question 21

what does the proximal convoluted tubule do?

Answer 21

reabsorption of water, proteins, amino acids, carbohydrates and glucose

Question 22

what is resorbed in the proximal tubule?

Answer 22

70% of sodium (active transport) and water follows (diffusion)
almost all glucose and amino acids (by co-transport)

Question 23

why are tight junctions important in proximal tubule cells?

Answer 23

to prevent the nutrients which have been resorbed being released into the space between cells

Question 24

what lines proximal convoluted tubules?

Answer 24

cuboidal epithelium

Question 25

what lines the loop of henle?

Answer 25

cuboidal epithelium changes to simple squamous as it dives into the medulla as it has to be thinner becomes cuboidal again as it ascends out of the medulla

Question 26

what does the loop of henle do?

Answer 26

creates hyperosmotic environment in the medulla

Question 27

proximal vs distal tubule?

Answer 27

``` proximal = thicker and more fuzzy/wooly, many many microvilli distal = more smooth, less microvilli ```

Question 28

what are the components of the loop of henle?

Answer 28

thick descending limb thin descending limb which makes a hairpin turn and journeys back thin ascending limb thick ascending limb

Question 29

describe blood supply tot he medulla

Answer 29

loops of thin walled vessels that dip down into the medulla from above and then climb back up to the cortex = collectively called the vasa recta

Question 30

why is the vasa recta needed?

Answer 30

as a normal blood supply through the medulla would carry all the salts etc from the hyperosmotic environment created by the loop of henle around the body, destroying the osmotic gradient in the body

Question 31

what does the distal convoluted tubule do?

Answer 31

acid-base and water balance (absorption of water, Na and bicarbonate, excretion of K and H ions)

Question 32

what regulates reabsorption of Na in the distal convoluted tubule?

Answer 32

aldosterone

Question 33

what are medullary rays?

Answer 33

parallel bundles of collecting ducts, straight portions of the proximal tubules and distal tubules running perpendicular to the surface of the kidney visible to the naked eye as stripes in the cortex that point towards the medulla

Question 34

what happens in the collecting ducts?

Answer 34

ADH from the posterior pituitary increases the permeability of the collecting duct to water therefore permeability of the duct is high during passage through the medulla and because of the high salt content in the surrounding tissue, water passes out of the lumen and a concentrated urine results

Question 35

what structures open into the minor calyxes at the renal papillae?

Answer 35

collecting ducts

Question 36

all parts of the urinary tract are lined with what?

Answer 36

transitional epithelium (or urothelium) - stratified (3-6 layers) - very impermeable - contains umbrella cells at luminal surface - special thickened, flexible membrane facing lumen

Question 37

how does transitional epithelium change?

Answer 37

as the bladder fills the transitional epithelium thins and stretches out

Question 38

what sits below the transitional epithelium?

Answer 38

``` lamina propria of connective tissue 2-3 layers of smooth muscle - inner longitudinal - outer circular - another longitudinal layer (only in the bladder) ```

Question 39

describe female urethra

Answer 39

3-5cm | initial lined with transitional epithelium with transitions to stratified squamous near its termination

Question 40

describe male prostatic urethra

Answer 40

3-4cm extends from bladder and through prostate gland lined by transitional epithelium

Question 41

describe membranous urethra in males

Answer 41

1cm from prostate to bulb of penis transitional changes to stratified columnar

Question 42

penile urethra?

Answer 42

15cm | lined by stratified columnar epithelium which becomes stratified squamous near the tip of the penis