histology of the urinary tract

Question 1

functional unit of the kidney + what it consists of

Answer 1

uriniferous tubule consisting of the nephron and collecting tubules

Question 2

renal corpuscle structure

Answer 2

bowman’s capsule and glomerulus

two poles- vascular pole containing the afferent and efferent arteriole and the urinary pole where the proximal tubule leaves

Question 3

what is the glomerulus?

Answer 3

knot of blood vessels

afferent glomerular arterioles supply it and efferent drain

Question 4

structure of glomerulus capillaries

Answer 4

fenestrated, with large pores- 60-90 nm diameter- lacking diaphragms

Question 5

structure of Bowman’s capsule

Answer 5

parietal layer, outside of capsule, formed of simple squamous epithelium

visceral layer envelops the capillaries, containing highly specialised epithelial cells called podocytes

bowman’s space, where fluid enters from the glomerulus

Question 6

three layers of the filtration apparatus

Answer 6

fenestrated capillary, basal lamina and podocytes

Question 7

function of fenestrated capillary

Answer 7

barrier to large macromolecules such as red blood cells

Question 8

three layers of basal lamina + important molecules in each

Answer 8

lamina rara interna

lamina densa- collagen

lamina rara externa- heparin sulphate

Question 9

function of basal lamina

Answer 9

collagen- separates molecules due to size

heparin- separates molecules due to charge

larger and more negatively charged molecules (proteins) are impeded

only small molecules and positive ions can pass through

Question 10

structure of podocytes

Answer 10

envelop the capillaries with slit pores

interdigitate to cover basal lamina

primary processes- long cytoplasmic extensions

secondary processes- pedicels which completely envelop most of the capillaries

pedicels form narrow clefts that are covered by a thin diaphragm

Question 11

how are pedicels attached?

Answer 11

attached to the basement membrane to laminin by integrins and attached to alpha actinin

Question 12

pedicel functions

Answer 12

nephrin molecules from adjacent pedicels interact to form negatively charged slit pores

nephrin prevents the passage through endothelial fenestrations

Question 13

what occurs in the renal corpuscle?

Answer 13

filtration

Question 14

where does reabsorption take place?

Answer 14

tubular part of the nephron

Question 15

three parts of the tubular system

Answer 15

proximal tubule, loop of Henle and distal tubule

Question 16

two parts of proximal tubule

Answer 16

pars convoluta- tortuous region

pars recta- straight, descending portion that forms the first part of the descending loop of Henle

Question 17

type of epithelium

Answer 17

leaky cuboidal

Question 18

structure of the epithelium

Answer 18

brush border formed of abundant microvilli

canaliculi, invaginations of the plasma membrane

eosinophilic granular cytoplasm

long mitochondria

abundant lysosomes

Question 19

type of epithelium in loop of Henle

Answer 19

simple squamous epithelium

number of tight junctions an composition of cells depends upon the function of that portion of the loop

Question 20

three regions of the distal tubule

Answer 20

pars recta, macula densa and pars convoluta

Question 21

distal tubule epithelium structure

Answer 21

cuboidal apart from macula densa where cells are tall and thin

shorter cuboidal cells and no brush border compared to PCT

elaborate basal membrane invaginations for ion transport

Question 22

important blood vessel in the nephron

Answer 22

vasa recta

Question 23

what is the vasa recta?

Answer 23

straight vessels that branch from the glomerular artery and surround the loop of Henle

Question 24

vasa recta function

Answer 24

generate a hypertonic interstitium by counter current exchange

Question 25

vasa recta structure

Answer 25

descending- continuous endothelial cells ascending- fenestrated endothelial cells

Question 26

explain vasculature of the kidney

Answer 26

interlobular arteries pass from the pelvis between the lobes form the arcuate arteries at the cortico-medullary junction afferent arterioles arise from the interlobular arteries in the cortex glomerulus in the cortex efferent arterioles drain the glomerulus to form the peritubular capillary network in the medulla that then form vasa recta

Question 27

collecting duct structure

Answer 27

begin in medullary rays of cortex principal cells with single cilium intercalated cells with microvilli several collecting ducts fuse at the ducts of bellini which terminate at the area cribosa

Question 28

juxtaglomerular apparatus definition

Answer 28

structure in the kidney that regulates the function of each nephron

Question 29

JGA function

Answer 29

cells that synthesise, store and secrete the enzyme renin regulate blood pressure and blood flow regulate glomerular filtration rate

Question 30

JGA structure

Answer 30

formed of the macula densa, extraglomerular mesangial cells and juxtaglomerular cells of the afferent glomerular arteriole

Question 31

mesangial cell definition

Answer 31

specialised smooth muscle

Question 32

two types of mesangial cells + location and function

Answer 32

extraglomerular- at vascular pole that relay information from macula densa intraglomerular- situated within renal corpuscle, have pericytes that have a phagocytic role and respond to vasoactive hormone and contract to narrow capillaries

Question 33

macula densa definition

Answer 33

region of the distal convoluted tubule area in contact with the glomerulus at the vascular part tall columnar cells

Question 34

macula densa function

Answer 34

cells sensitive to the ion content and water volume of the fluid in the distal convoluted tubule detect sodium, potassium and chloride concentrations signal by releasing prostaglandins when they detect a fall

Question 35

prostaglandin function

Answer 35

activate extraglomerular mesangial cells

Question 36

ureter definition

Answer 36

muscular tube that delivers urine from collecting tubules to the urinary bladder

Question 37

ureter structure

Answer 37

lined by mucosa muscularis muscular coat- 2/3 layers fibrous connective tissue- fibroelastic lamina propria transitional epithelium lining 3-5 layers thick

Question 38

bladder structure

Answer 38

transitional epithelium thickened plaque regions within plasma membrane contain glycoproteins which protect cells interplaque regions - where folding occurs reserve membrane stored in vesicles for when bladder is stretched

Question 39

plaque function

Answer 39

act as an osmotic barrier- impermeable to water and salt

Question 40

urethra structure

Answer 40

longer in males than females extrenal and internal sphincters contain glands of litre and intrepithelial glands that secrete mucus, aiding the passage of urine

Question 41

urethra epithelium

Answer 41

starts off as transitional as it exits the bladder then becomes pseudostratified/stratified columnar

Question 42

detrusor muscle location

Answer 42

smooth muscle found in the wall of the bladder

Question 43

structure of detrusor muscle

Answer 43

fibres arise from the posterior surface of the body of the pubis in both sexes fibers pass in a longitudinal manner up the inferior surface of the bladder, over its apex, descend along the fundus become attached to prostate in the male and front of vagina in the female three layers of muscle arranged longitudinal- circular- longitudinal arranged obliquely and intersect one another

Question 44

parasympathetic innervation of bladder + function

Answer 44

branches of pelvic splanchnic nerves to empty bladder

Question 45

sympathetic innervation of bladder + function

Answer 45

branches of inferior hypogastric plexus relax muscle, allow bladder to fill