Ch 27 Urinary

kidneys, ureters, urinary bladder, and urethra

•Storage & Expulsion of urine

•Regulate blood volume under hormones

•Regulation of erythrocyte production by the release of erythropoietin (EPO)

•Regulation of ion levels, such as sodium, potassium, calcium, and phosphate

•Regulation of acid-base balance by altering levels of hydrogen and bicarbonate ions

retroperitoneal against posterior abdominal wall

-superior pole have adrenal glands left kidney is at T12

right kidney is lower for liver

Inferior pole at L3 vertebra

hilum— medial border where vessels, nerves, and the ureter connect

•The hilum is continuous with renal sinus

•Fibrous capsule: dense irregular CT

•Perinephric fat: adipose providing cushioning

•Renal fascia: dense irregular connective tissue anchoring kidney to posterior abdominal wall

Paranephric fat: adipose between renal fascia and peritoneum

-outer renal cortex and inner renal medulla

-Renal columns- extensions of renal cortex to create renal pyramids

-borer of cortex and medulla- corticomedullary junction

-apex (tip) of a renal pyramid renal papilla

minor calyx hollow funnel

form major calyx

form renal pelvis

• pelvis collect urine and transports it into the ureter

A kidney has 8 to 15 renal lobes

•Each lobe consists of a renal pyramid and cortical tissue surrounding

-Blood enters renal arteries

-branch into segmental arteries

- branch interlobar arteries

•Interlobar arteries travel in renal columns

- corticomedullary junction, interlobar arteries branch into arcuate arteries

branches interlobular arteries -radiate out to cortex

extend afferent arterioles

enters a renal corpuscle and forms tuft of capillaries glomerulus

Some plasma is filtered out of the capillaries into the capsular space within the renal corpuscle

- remaining blood exits glomerulus and the renal corpuscle via efferent arteriole

•Peritubular capillaries: surround convoluted tubules and reside in cortex

or

•Vasa recta: with nephron loop and reside in the medulla

Peritubular capillaries and vasa recta drain into a network of veins

smallest interlobular veins

form arcuate veins

form the interlobar veins

merge in renal sinus to form the renal vein

Kidney is innervated by sensory and autonomic fibers renal plexus- enters kidney at the hilum

Pain referred to dermatomes T10–T12

filtration unit of kidney

renal corpuscle and renal tubule (proximal convoluted tubule, a nephron loop, and a distal convoluted tubule)

two types

•Cortical nephrons: in kidney cortex; 85%

•Juxtamedullary nephrons: renal corpuscle near corticomedullary junction and nephron loop extends into medulla; 15% of all nephrons

•Filtration

only in the glomerulus.

•Water and some dissolved solutes move out of glomerulus and into capsular space of renal corpuscle

•Once fluid leaves plasma and enters capsular space filtrate

•Tubular reabsorption

(PCT)

•Substances in filtrate reenter to blood

•Most water and all needed solutes in filtrate are reabsorbed

•Tubular secretion

DCT

•Solutes transported out of blood and into tubular fluid

bulbous part of nephron

•Glomerulus: tangle of capillaries

•Glomerular capsule: an epithelial capsule surrounding glomerulus; made of two layers separated by capsular space

•Visceral layer -(contacting glomerulus) made of podocytes

•Parietal layer - simple squamous epithelium

vascular pole, afferent arteriole enters and efferent arteriole exits

tubular pole, proximal convoluted tubule(PCT) exits

1.Endothelium of glomerulus: fenestrated, allowing filtration but preventing passage of larger materials ( cells, platelets)

2.Basement membrane of glomerulus: porous; restricts passage of large proteins

3.Visceral layer of glomerular capsule: made of podocytes-cells with long processes called pedicels wrap around the glomerular capillaries

•Pedicels are separated by filtration slits

It is the role of the remainder of the nephron to adjust the contents of the filtrate

at tubular pole of renal corpuscle

Walls are simple cuboidal epithelium with tall microvilli

Cells reabsorb almost all nutrients leaked through the filtration membrane

•Reabsorbed nutrients and water enter peritubular capillaries and are returned to the general circulation

(loop of Henle) projects into the medulla

1.Descending limb: extends from cortex into the medulla

•simple cuboidal then simple squamous epithelia

2.Ascending limb: returns from medulla into cortex

•Lined with simple squamous then simple cuboidal epithelia

reabsorption of water and solutes (especially sodium and chloride ions)

in renal cortex and contacts afferent arteriole wall at the vascular pole

-simple cuboidal epithelium (microvilli sparse and short)

Secretes K⁺ and H⁺ from peritubular capillaries into tubular fluid

Responds to ADH and aldosterone by altering reabsorption

•ADH increased water reabsorption

•Aldosterone increased sodium reabsorption

DCT lead to collecting tubules that empty into collecting ducts

•Collecting ducts course through medulla toward renal papilla

•They are lined by simple cuboidal then simple columnar epithelia

Collecting ducts modify tubular fluid under the influence of aldosterone- Na^{+ reabsorption} and ADH -H₂O reabsorption

- tubular fluid leaves collecting duct and enters papillary duct, urine

•Collecting duct empties into papillary duct that opens into minor calyx

•Minor calyx leads to major calyx which leads to pelvis

•Calyces and pelvis are lined with transitional epithelium

regulate blood pressure

•Granular cells (juxtaglomerular cells): modified smooth muscle cells of afferent arteriole located at vascular pole of renal corpuscle

• release renin, increase in blood pressure

• response to drop in blood pressure or stimulation by sympathetic nervous system

•Macula densa: modified epithelial cells in distal convoluted tubule that contact granular cells

•Monitor NaCl concentration in tubular fluid and can stimulate granular cells

•Extraglomerular mesangial cells sit between granular cells and arterioles

•Can contract and phagocytize filtered particles

•Ureters

•Urinary bladder

•Urethra

urine from kidney to urinary bladder

renal pelvis at the hilum of the kidney

base of urinary bladder at its posterolateral wall

•Mucosa - transitional epithelium and lamina propria (dense irregular CT)

•Muscularis - inner longitudinal layer and outer circular layer of smooth muscle

•Adventitia of areolar connective tissue

storage of urine

posterior to pubic symphysis

females, lies anteroinferior to uterus and directly anterior to the vagina

males, anterior to the rectum and superior to the prostate gland

Only its superior surface is covered with peritoneum

Empty bladder -upside-down pyramidal shape

•Neck of bladder inferiorly and connects to urethra

triangular area of the urinary bladder is trigone

two ureteral openings

•Mucosa: Transitional epithelium that lines the internal surface of the bladder; rugae (mucosal folds) allow for further distension

•Submucosa: Dense irregular connective tissue that supports urinary bladder wall

•Muscularis: Three layers of smooth muscle collectively called the detrusor muscle

•A thickened internal urethral sphincter is present at urethral opening

•Adventitia: outer layer of areolar connective tissue

originating at urinary bladder, conducts urine to exterior of body

Lined with mucin-producing cells in mucosa

Has smooth muscle to help propel urine

control release of urine

•Internal urethral sphincter neck of bladder; involuntary

•External urethral sphincter urogenital diaphragm; voluntary

transports only urine

•Stratified squamous epithelium

urinary and reproductive functions

•three segments:

•Prostatic urethra: Through prostate gland; transitional epithelium lining

•Membranous urethra: Short segment through urogenital diaphragm; stratified columnar or pseudostratified epithelial lining

•Spongy urethra: Long segment through erectile tissue of penis; lined by pseudostratified epithelium proximally and stratified squamous distally

opening is called the external urethral orifice

(urination)expulsion of urine from bladder

Controlled by micturition reflex

•Extension of bladder excites its stretch receptors which signal spinal cord’s reflex center

•Parasympathetic signals are sent to internal urethral sphincter (to relax it) and detrusor muscle (to excite it)

•Voluntary relaxation of external urethral sphincter required

•Abdominal muscle contraction also helps empty bladder

Blood flow to kidneys decreases

Number of functional nephrons decreases

Decreased responsiveness to aldosterone and ADH

Less control of blood volume and pressure

Bladder decreases in size and loses muscle tone

Control of urethral sphinters may be lost leading to incontinence

Most of urinary system forms from intermediate mesoderm of embryo

Urogenital ridges are bilateral embryonic structures that give rise to pairs of:

•Pronephros: Vestigial organ that quickly degenerate in fourth week

•Mesonephros: saclike segments in thoracic and lumbar regions that appear in fourth week and persist until Week 10

•Metanephros: adult kidney; takes over urine production by Week 10

•Forms ureteric bud (gives rise to calyces, pelvis, ureter) and metanephric mesoderm (forms nephron parts)