12.1 Urinary system

functions of urinary sustem

• removes metabolic waste

• regulates fluid and electrolyte balance

• regulates blood pressure

• produces, transports stores and excretes urine (micturition)

kidney location

T12-L3 - either side

• right kidney slightly lower than left

• retroperitoneal organs

kidney anatomical relationships

• surrounded by fat = kepps in position

• medial- T12-L3 and psoas major

• posterior - quadratus lumborum, thoracic diaphragm and ribs 11-12

• anterior - peritonem and abdominal viscera

structures passing thru kidney hilum

anterior to posterior:

• renal vein

• renal artery

• renal pelvis

tissues of kidney

• renal cortex - outer layer beneath capsule

• renal medulla - inner layer

renal cortex

includes

• renal columns

• renal cortex - contains glomerulus, proximal and distal convoluted tubules

renal medulla

includes

• medullary pyramid - contains loop of Henle and collecting ducts

• medullary papilla - connects collecting ducts to minor calyx

kidney tubular system

1. minor calyx - receives finished urine from collecting ducts

2. major calyx - connects minor to pelvis

3. renal pelvis - channels urine into ureter

pathway of urine

renal papilla>minor calyx>major calyx>renal pelvis>ureter>bladder>urethra

renal blood supply

abdominal aorta>renal artery>segmental branches

renal artery

paired branches off abdominal aorta at L1-2

• enters kidneys thru renal hila and divide into segmental arteries

importance of segmental arteries in kidneys

each segmental artery supplies a distinct region of kidney = a diseased region may be removed while preserving remaining kidney tissue

ureters

paired smooth muscle tubes

• peristaltic contractions transport urine from kidney to urinary bladder

• retroperitoneal

common constrictions of ureter

• ureteropelvic junction - renal pelvis to ureter

• pelvic brim - crossing iliac vessels

• ureterovesical junction - entry into bladder

bladder sphincter

functional sphincter due to urinary bladder wall contraction

bladder

• hollow viscus

• highly distensible to store urine

• shape changes from empty (rugae/folded) to full (expanded)

• located anteriorly in pelvis

features of bladder

• ureters enter posterior bladder wall and open at 2 ureteric orifices

• trigone

• rugae

• detrusor

trigone

smooth triangular region of mucosa on internal bladder base - bounded by 2 orifices and internal urethral sphincter

• no rugae

rugae in bladder

folds in bladder’s mucosal lining that flatten as it fills

detrusor

smooth muscle forming the bladder wall including beneath trigone = contracts to expel urine into urethra

bladder during filling

• empty - lies within pelvis behind pubic symphysis

• as fills - bladder expands upwards while neck remains fixed - wall stretches and rugae flattens

how to empty bladder

detrusor contracts and outlet relaxes

bladder control

• storage - sympathetic = relaxes detrusor and helps keep bladder outlet closed

• voiding - parasympathetic = contracts detrusor to expel urine

• somatic - voluntary control - external urethral sphincter contracts to hold urine and relaxes to allow voiding

ureathra

muscular tube that carries urine from bladder to exterior

• terminal part of urinary system

• begins at internal urethral orifice of bladder

ureathra function

differs between sexes

• urinary in both

• additional reproductive in males e.g. semen

female urethra

• shorter = increased risk of urinary tract infection

• external urethral orifice located btwn labia minora and anterior to vaginal opening

male urethra

• longer

• curved pathway

• passes thru prostate and penis

regions of male urethra

1. preprostatic urethra - passes thru bladder wall

2. prostatic urethra

3. membranous urethra

4. spongy urethra

prostatic urethra

enlarged by prostate gland

• enlargment may obstruct urine flow

membranous urethra

surrounded by external urethral sphincter and important for voluntary control of urination

spongy urethra

• located within corpus spongiosum

• lumen remains open for urination and ejaculation

• surrounding tissue prevents urethral collapse