Biology 218 – Human Anatomy
Clemens
Urinary System
Text: Ch. 25
Organs: kidneys
ureters
urinary bladder
urethra
fxns: urine production and elimination
- excretion (urea + other waste products)
- water balance
- electrolyte and acid-base balance
A. Kidneys
1. External anatomy
- retroperitoneal
3 external CT layers: renal capsule
adipose capsule
renal fascia
renal hilum - entry/exit of renal artery, renal vein, ureter
renal pelvis - connects kidney to ureter
2. Internal anatomy
renal cortex
renal columns
renal medulla
renal pyramids
renal papillae
nephrons - functional units of the kidneys, ~1 million per kidney
duct system: collecting duct → papillary duct → minor calyx → major calyx
→ renal pelvis → ureter
blood supply: renal artery
segmental arteries
interlobar arteries
arcuate arteries
interlobular arteries
afferent arterioles
glomerular capillaries
efferent arterioles
peritubular capillaries (includes vasa recta)
(veins correspond to arteries)
3. The Nephron
a. renal corpuscle
glomerulus
glomerular capsule (Bowman’s capsule)
b. renal tubule
proximal convoluted tubule (PCT)
loop of Henle (nephron loop)
descending limb
ascending limb; thin and thick regions
distal convoluted tubule (DCT)
c. collecting duct - joins to several nephrons
renal cortex contains renal corpuscles, PCTs and DCTs
renal medulla contains loops of Henle and collecting ducts
cortical nephrons - located mostly in cortex, short loops of Henle
juxtamedullary nephrons - go deep into medulla, long loops of Henle
Biology 218 – Human Anatomy
Clemens
3 processes: filtration
location: renal corpuscle
reabsorption
mostly in PCT; some in loop, DCT, collecting duct
secretion
mostly in DCT
4. Histology
a. glomerular capsule
parietal layer - simple squamous epithelium
visceral layer - podocytes cover glomerular capillaries
filtration membrane:
1. fenestrated capillaries (endothelium) of the glomerulus
2. basal lamina
3. filtration slits between podocyte foot processes
b. renal tubule
PCT - simple cuboidal epithelium, many microvilli
loop of Henle - simple squamous and simple cuboidal epithelium
DCT - simple cuboidal epithelium, few microvilli
juxtaglomerular apparatus - sensory/regulatory structure at beginning of DCT
macula densa - specialized epithelial cells in DCT adjacent to renal corpuscle
juxtaglomerular cells - modified smooth muscle cells of afferent arteriole
c. collecting duct - simple cuboidal epithelium
B. Ureters
~ 10-12” tubes between kidneys and urinary bladder; retroperitoneal
- thick muscular walls; star-shaped lumen
1. mucosa
transitional epithelium
lamina propria
2. muscularis - smooth muscle
inner longitudinal
outer circular
(distal ureter has 3rd outer layer of longitudinal muscle)
3. adventitia
C. Urinary Bladder
- located in pelvic cavity, below the peritoneum
rugae - folds in mucosa, enable expansion
ureteral openings - located posterior and inferiorly
internal urethral orifice → urethra
trigone - inner surface between ureteral openings and internal urethral orifice
3 coats, similar to distal ureter
1. mucosa - transitional epithelium
2. muscularis - very thick, 3 layers, = detrusor muscle
3. adventitia; serosa on superior surface (parietal peritoneum)
D. Urethra
females - short tube ~ 4 cm
internal urethral sphincter - smooth muscle (involuntary)
external urethral sphincter - skeletal muscle (voluntary), in urogenital diaphragm
external urethral orifice
males - long tube ~ 20 cm, 3 sections:
1. prostatic urethra
(through prostate gland)
2. membranous urethra (through urogenital diaphragm)
3. spongy urethra
(through penis)
Biology 218 – Human Anatomy
Clemens
Study Questions
1. Describe the major anatomical features of the kidney. Include the following regions
and structures: renal cortex, renal column, renal medulla, renal pyramid, minor calyx,
major calyx, renal pelvis.
2. Diagram the structure of the nephron showing its major components (glomerulus,
glomerular capsule, PCT, loop of Henle, DCT), and the collecting duct. Which parts
of the nephron are located in the renal cortex and which are located in the renal
medulla?
3. Summarize the renal blood supply and differentiate between the following
structures: afferent arteriole, glomerulus, efferent arteriole, peritubular capillaries,
vasa recta.
4. What are the three basic processes involved in forming urine? Which parts of the
nephron perform each process?
5. Describe the specific structures that make up the filtration membrane in the kidneys.
What type of capillaries comprise the glomerulus? What is a podocyte?
6. Identify the specific tissue types that are found in the nephron, ureters, and urinary
bladder, and identify the major structural features of the urinary bladder
7. Compare the anatomy of the female urethra and male urethra.