Kidneys and UrinationKidney

Location and blood supply

Internal anatomy

Microscopic anatomy and function

Ureter

Bladder and urethra

Location of kidney

Retroperotoneal at mid-abdomenT12-L3NAV enters at hilus

Renal aa. off aortaRenal vv to IVCNerves all autonomics--renal plexus

Ureter--exits at hilus“Ad”renal gland superior to kidney--unrelated in function

Own blood supplyEndocrine gland

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 tissueDarker

Pyramid-cone shape

Collecting tubules unite into ducts into ureter

Pg 679

Internal anatomy of kidney--details

Lobe of kidney is medullary pyramid plus cortex around it

Cortex contains urine-concentrating nephrons

Medullary pyramidsTubules receive concentrated urine from cortex

Appear striated because contains parallel converging urine-collecting tubules

Flow of urineCollecting tubes of medullary pyramid minor calyx major calyx renal pelvis ureter

Microscopic anatomy and functionNephron or urine-concentrating unit is in outer cortex--millionsCapillaries surround glomerulus (ball) and filtrate passes into ductCounter-current exchange in ducts (Loop of Henle) concentrates urine)

More details at “How Stuff Works”http://science.howstuffworks.com/kidney.htm/printable

Ureter--from kidney to bladderLAYERS 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

BladderMuscular (what kind?) sac that fills with urine from uretersAnterior against pubis in pelvis (more with pelvis)Filled with urine expands into abdomenBlood supply from internal iliac arteriesInnervation is autonomic from hypogastric plexus

Layers of bladder wallOuter connective tissue--adventitiaMiddle muscular layer (“detrusal” or expulsor)--inner and outer longitudinal fibers around middle circular fibersInner transitional (stretchy) epitheliumBladder can expand 15 times its empty volume to hold 500 ml of urineTrigone is triangle between ureters/urethra--persistent sight of infection

UrethraDrains urine from bladder to outside

Female = short tube

Males = long tubeProstatic, Membranous, Spongy (penile) portions

Also carries sperm

Internal Urethral SphincterBetween bladder + urethra

Thickening of detrusor (smooth muscle)

External Urethral SphincterWithin urogenital diaphragm

Skeletal muscle = voluntary control urination

External Urethral OrificeMales = end of penile urethra

Females = anterior to vaginal opening, posterior to clitoris

(more later with pelvis)

For nice review of kidneys and urinationhttp://webanatomy.net/anatomy/urinary_notes.htm

Micturition = UrinationEmptying bladder

Stretch receptors in bladder respond when bladder fullParasympathetic 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 pressureVoluntary relaxation of external urethral sphincter

See pg 692, M&M

Ascent of the kidney in developmentKidneys 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