1. Kidneys and Urination Kidney Ureter Bladder and urethra
Location and blood supply
Internal anatomy
Microscopic anatomy and function
Ureter
Bladder and urethra

2. Location of kidney Retroperotoneal at mid-abdomen T12-L3
NAV enters at hilus
Renal aa. off aorta
Renal vv to IVC
Nerves all autonomics--renal plexus
Ureter--exits at hilus
“Ad”renal gland superior to kidney--unrelated in function
Own blood supply
Endocrine gland

3. Internal anatomy of kidney
NAV branch out from hilus
Collecting ducts unite and urine leaves through ureter at hilus
Cortex is outer/superficial tissue
Light, granular
Functioning nephrons here
Medulla is inner/deep tissue
Darker
Pyramid-cone shape
Collecting tubules unite into ducts into ureter

4. Internal anatomy of kidney--details
Lobe of kidney is medullary pyramid plus cortex around it
Cortex contains urine-concentrating nephrons
Medullary pyramids
Tubules receive concentrated urine from cortex
Appear striated because contains parallel converging urine-collecting tubules
Flow of urine
Collecting tubes of medullary pyramid minor calyx major calyx renal pelvis ureter
Pg 679

5. Microscopic anatomy and function
Nephron or urine-concentrating unit is in outer cortex--millions
Capillaries surround glomerulus (ball) and filtrate passes into duct
Counter-current exchange in ducts (Loop of Henle) concentrates urine)
More details at “How Stuff Works”

6. Ureter--from kidney to bladder
LAYERS OF URETER
External connective tissue--adventitia
Middle muscular layer--muscularis
Smooth Muscle
Inner Longitudinal
Outer Circular
External longitudinal (on distal third)
Peristaltic action moves urine to bladder (and stones!!)
Inner lining of transitional (stretchy) epithelium--Mucosa

7. Bladder Muscular (what kind?) sac that fills with urine from ureters
Anterior against pubis in pelvis (more with pelvis)
Filled with urine expands into abdomen
Blood supply from internal iliac arteries
Innervation is autonomic from hypogastric plexus

8. Layers of bladder wall Outer connective tissue--adventitia
Middle muscular layer (“detrusal” or expulsor)--inner and outer longitudinal fibers around middle circular fibers
Inner transitional (stretchy) epithelium
Bladder can expand 15 times its empty volume to hold 500 ml of urine
Trigone is triangle between ureters/urethra--persistent sight of infection

9. Urethra Drains urine from bladder to outside Female = short tube
Males = long tube
Prostatic, Membranous, Spongy (penile) portions
Also carries sperm
Internal Urethral Sphincter
Between bladder + urethra
Thickening of detrusor (smooth muscle)
External Urethral Sphincter
Within urogenital diaphragm
Skeletal muscle = voluntary control urination
External Urethral Orifice
Males = end of penile urethra
Females = anterior to vaginal opening, posterior to clitoris
(more later with pelvis)

10. Micturition = Urination
Emptying bladder
Stretch receptors in bladder respond when bladder full
Parasympathetic signals detrusor muscle to contract and internal urinary sphincter to open (also inhibits sympathetic pathways that would prevent urination)
Other brain receptors can inhibit urination by relaxing detrusor, and keep external urinary sphincter closed
Voluntary contraction of abdominal wall muscles increases abdominal pressure
Voluntary relaxation of external urethral sphincter
For nice review of kidneys and urination
See pg 692, M&M

11. Ascent of the kidney in development
Kidneys from intermediate mesoderm
Pronephric kidney in fetus shows segmental body plan
Fish with dorsal renal tissue lateral to vertebral column for most of length
In human, metanephric kidney migrates from inferior to superior
Variation in kidney shape not uncommon (horseshoe kidney
Ureter also from intermediate mesoderm