IPHY 3410, Section 100
Lecture Date
Topic
L26
Urinary system
Tues 4/28
VOCABULARY
Spring, 2009
LOWRY
Reading in Marieb, Mallatt, and Wilhelm
Ch. 23, pp. 687-705
Urinary system
Kidneys
Function
filters blood, sending toxins, metabolic wastes, excess water, and excess ions out
of the body while returning needed substances from the filtrate back to
the blood
excretion of wastes
urea
uric acid
creatinine
regulate volume and chemical makeup of blood
water
salts
acids
bases
ureters
urinary bladder
urethra
Gross anatomy of the kidneys
External gross anatomy
hilum (where vessels, ureters, and nerves enter and leave the kidney)
fibrous capsule (dense connective tissue)
Internal gross anatomy
renal cortex
renal medulla
renal pyramids
apex (papilla)
renal columns
lobes (pyramid plus surrounding cortex)
renal sinus
renal vessels
renal nerves
fat
renal pelvis (expanded superior part of ureter)
major calices (singular, calyx)
minor calices
Gross vasculature and nerve supply
renal arteries (from abdominal aorta)
glomerular arterioles
peritubular capillaries
renal veins (empties into inferior vena cava
1
renal plexus (nerve supply)
Microscopic anatomy of the kidneys
uniferous tubules (structural and functional unit of the kidney)
Mechanisms of urine production
filtration
resorption (recovery of most of the nutrients, water, essential ions; ~99% of
volume)
secretion
uniferous tubules
1) urine-forming nephron (filtration, resorption, secretion)
2) collecting duct (concentrates urine by removing water from it)
lined by simple epithelium
Nephron
1) renal corpuscle (where filtration occurs)
located in cortex
glomerulus (tuft of capillaries)
fenestrated capillaries
allow passage of fluid and small molecules
capsular space
glomerular capsule (Bowman’s capsule)
parietal layer (structural only)
simple squamous
visceral layer
podocytes
foot processes
filtration slits
filtration membrane (filtration barrier)
1) fenestrated epithelium of capillary
fluid, small proteins
2) filtration slits between the foot processes of podocytes,
each covered by a thin slit diaphragm
water, ions, glucose, amino acids, urea
3) an intervening basement membrane, fused basement
membrane
2) tubular section
proximal convoluted tubule
in renal cortex
resorption
secretion
simple cuboidal epithelium with microvilli
loop of Henle
descending limb
thin segment
simple squamous epithelium
ascending limb
thick segment
distal convoluted tubule
in renal cortex
2
simple cuboidal epithelium
secretion and resorption
cortical nephrons
juxtamedullary nephrons
long loops of Henle contribute to ability to concentrate urine
Collecting duct
simple cuboidal epithelium
papillary ducts
simple columnar epithelium
concentrate urine (conserve body fluids)
antidiuretic hormone (ADH)
increases permeability of collecting duct and distal tubules to
water
Microscopic blood vessels associated with uriniferous tubules
capillaries in glomeruli
filtration
fed and drained by arterioles
afferent arteriole
efferent arteriole
more narrow diameter than afferent arteriole,
creates high pressure
peritubular capillaries
absorption, secretion
adjacent to convoluted tubules
vasa recta
urine concentrating
Juxtaglomerular apparatus
blood pressure regulation
Ureters
Gross anatomy
carry urine from kidneys to the bladder
Microscopic anatomy
mucosa
transitional epithelium
lamina propria (fibroelastic connective tissue)
muscularis
inner longitudinal layer of smooth muscle
outer circular layer of smooth muscle
adventitia
connective tissue
Urinary bladder
mucosa
transitional epithelium
lamina propria (fibroelastic connective tissue)
muscularis
inner longitudinal layer of smooth muscle
middle circular layer of smooth muscle
outer longitudinal layer of smooth muscle
3
adventitia
connective tissue
rugae
Urethra
smooth muscle
mucosa
transitional epithelium > stratified/pseudostratified columnar > stratified squamous
epithelium
internal urethral sphincter
external urethral sphincter
external urethral orifice
females
3-4 cm
males
20 cm
prostatic urethra
membranous urethra
spongy urethra
Micturition
urination
4