Urinary System

Question 1

Functions of Urinary System

Answer 1

• Removal of waste products from bloodstream
• Production of urine
• Storage and excretion of urine
• Blood volume regulation
• Regulation of erythrocyte production
• Regulation of ion balance/acid-base balance

Question 2

Urinary system components

Answer 2

• kidneys
• ureters
• urinary bladder
• urethra

Question 3

Location of kidneys

Answer 3

• retroperitoneal on posterior abdominal wall
• superior pole of left kidney is at level of T12 - right kidney 2 cm lower due to presence of liver
• concave medial border = hilum (where vessels, nevers and ureter connect w/ kidney)
• hilum continuous w/ renal sinus (internal space)

Question 4

Kidneys

Answer 4

• each kidney surrounded & supported by several tissue layers (deepest to most superficial);
• Fibrous capsule (direct contact w/ outer surface - maintains shape, protects)
• Perinephric fat (Provides cushioning and insultion
• Renal fascia - anchors kidney to posterior abdominal wall
• paranephric fat: outermost layer surrounding kidney between renal fascia and peritoneum

Question 5

Regions of Kidney (2)

-where regions meet

Answer 5

• Divided into outer renal cortex and inner renal medulla
  
  • extensions of renal cortex (renal columns) project into renal medulla and subdivide medulla into renal pyramids
• 8-15 renal pyramids per kidney
• Wide base of renal pyramid makes contact w/ cortex = CORTICOMEDULLARY JUNCTION
• apex of renal pyramid = renal papilla

Question 6

Tubing w/in renal sinus

• minor & major calyx
• renal pelvis

Answer 6

• Each renal papilla projects into hollow funnel-shaped structure = Minor calcyx
• Several minor calyces fuse to form major calyx
• major calyces fuse to form renal pelvis (collects total urine output from one kidney and transports it to ureter)

Question 7

Arterial Supply to Kidney (to cortex)

Answer 7

• Blood enters kidneys via renal arteries
• w/in renal sinus, renal arteries branch into interlobar arteries (b/w renal pyramids)
• interlobar branch into arcuate arteries (follow corticomedullary junction)
• arcuate arteries branch into interlobular arteries (when in cortex)

Aorta -> Renal -> Segmental -> Interlobar -> arcuate -> interlobular

Question 8

Arterial supply to Kindey (from cortex)

Answer 8

• as interlobular arteries enter kidney cortex, extend small branches called afferent arterioles
  
  • enter renal corpuscle (struct.) and form a tuft of capillaries called glomerulus
• remaining blood exits glomerulus and renal corpsule as efferent arteriole
• Blood filtration occurs at glomerulus

interlobular -> afferent -> glomerulus -> efferent

Question 9

Capillary supply to Kidney (2)

Answer 9

• efferent arterioles branch into one of two capillary networks: (where exchange of gases occur)
• Peritubular capillaries: surround convoluted tubules and reside primarily in cortex
• Vasa recta - ass. mainly w/ nephron loop and primarily reside in medulla (recta = straight)

Question 10

Venous Return from the Kidney

Answer 10

-Peritubular capillaries & vasa recta drain into network of veins;

• smallest veins are interlobular veins
• merge to form arcuate veins (corticomedullary junction)
• merge in renal sinus to form renal vein

Interlobular -> arcuate -> interlobular -> renal vein

*all this blood is deoxygenated

Question 11

Nephron

Answer 11

• is functional filtration unit of kidney
• approx. 1.25 million nephrons in each kidney
• Form urine in 3 processes (related);
  
  • filtration
  • tubular reabsorption
  • tubular secretion

*final product is formation of urine (from filtrate)

Question 12

2 types of nephrons

Answer 12

1. Cortical nephrons: approx. 85% of all nephrons
   - bulk of nephron resides in cortex - small component enters medulla (nephron loop)
2. Juxtamedullary nephrons: renal corpuscle lies near corticomedullary junction and their long nephron loops extend deep into medulla

-long medulla in animals in dry areas - really conc. urine

Question 13

4 components of a nephron

Answer 13

• Renal corpuscle
• Proximal convoluted tubules
• nephron loop
• Distal convoluted tubule

Question 14

Renal corpuscle

-2 structures

Answer 14

• composed of 2 structures;
  1. Glomerulus: thick tangle of fenestrated capillaries (studded by lots of holes)
  2. flomerular capsule (Bowman’s capsule): epithelial covering over glomerulus
• corpuscle has vascular pole where afferent arteriole enters and efferent arteriole exits
• tubular pole = proximal convoluted tubule exits

Question 15

2 layers of Glomerular Capsule

-podocytes

Answer 15

1. Visceral layer: directly overlies and comes in contact w/ glomerulus
   
   • composed of specialised cells called PODOCYTES (have little projections that help them wrap around capillaries)
2. Parietal layer: formed from simple squamous epithelium

Question 16

Podocytes - pedicels (function)

Answer 16

• Have long processes called pedicels that wrap around glomerular capillaries (don’t completely ensheathe)
• pedicels separated from each other by filtration slits
• filtration slits and fenestrated capillary wall makes up filtration membrane - mostly leaks indiscriminate contents from plasma
  
  • role of remainder of nephron = adjust contents of nephron

Question 17

Proximal Convoluted Tubule

Answer 17

• Walls of simple cuboidal epithelium w/ tall microvilli
• reabsorb almost all nutrients leaked through filtration membrane
• reabsorbed nutrients and water enter peritubular capillaries - returned to general circulation in vascular system

Question 18

Nephron Loop

Answer 18

• AKA loop of henle
• projects into medulla
• 2 limbs (descending [from cortex] and ascending [to cortex])
• both limbs facilitate reabsorption of water and solutes
  
  • enter vasa recta capillaries and returned to general circulation

Question 19

Distal Convoluted Tubule

Answer 19

• Found in renal cortex
• Secretes K and H ions from peritubular capillaries into tubular fluid
• reabsorption of water also occurs
• lined w/ simple cuboidal epithelium - but smaller and sparse amounts of microvilli (doesn’t seem fuzzy like proximal)
• makes contact w/ afferent arteriole at vascular pole - gives feedback to rest of system - to either increase or decrease filtration)

Question 20

Collecting tubules & ducts

Answer 20

• project through medulla toward renal papilla
• lined by simple epithelium (cuboidal to columnar)
• last structures to modify tubular fluid
• when tubular fluid leaves collecting duct at papilla, called urine

Question 21

Juxtaglomerular Apparatus - 2 components

-function

Answer 21

-Is important in regulation of blood pressure
Comprised of;-
-juxtagomerular cells - modified smooth muscle cells of afferent arteriole located at vascular pole of renal corpuscle
-macula densa cells - group of modified epithelial cells in distal convoluted tubule - come into contact w/ juxtaglomerular cells

• help regulate sodium and other things in distal tubule
• both cells in contact - communicate info to each other

Question 22

Urinary Tract components

Answer 22

• Ureters
• urinary bladder
• urethra

Question 23

Ureters

-3 layers

Answer 23

-Fibromuscular tubes that conduct urine from kidney to urinary bladder
-originate at renal pelvis as it exits hilum of kidney
3 layers;
-mucosa (inner lining)
-muscularis (need to close off ureter and move urine along)
-adventitia (connective tissue that attaches it to body wall)

Question 24

Urinary Bladder- function

• trigone
• location in females and males

Answer 24

• Main function = reservoir of urine
• located immediately posterior to pubic symphosis
• trigone - posteroinferior triangular area - defined by two ureteral opening and urethral opening

Females: anteroinferio to uterus and directly anterior to vagina
Males: anterior to rectum and superior to prostrate gland

Question 25

Wall of urinary bladder (4 layers)

Answer 25

- Mucosa: transitional epithelium that lines internal surface of bladder; rugae allow distension of bladder - Submucosa - suuports urinary bladder wall - Muscularis - 3 layers o smooth muscled called detrusor muscle; an internal urethral sphincter muscle present at urethral opening - Adventitia - outer layer of areolar connective tissue

Question 26

Urethra -2 sphincters

Answer 26

- fibromuscular tube that originates at neck of urinary bladder and conducts urine to exterior of body - 2 sphincters control release: - Internal urethral sphincter - external urethral sphincter

Question 27

Female Urethra

Answer 27

- has single function of transporting urine | - very short & close to anus

Question 28

Male urethra - 3 segments

Answer 28

- 2 functions: urinary & reproductive - partitioned into three segments; 1. Prostatic urethra (trigone opening thru prostate) 2. Membranous urethra (continues from prostatic to body diaphragm) 3. Spongy urethra (through shaft of penis) *ends in opening called eternal urethral orifice

Question 29

Micturition

Answer 29

-AKA urination -initated by micturition reflex Controlled by 2 nervous systems; 1. Parasympathetic (rest/digest): allows internal sphincter to relax & contracts detrusor muscle - results in micturition/urination) 2. Sympathetic (fright/fight/flight): contracts internal sphincter & inhibits detrusor muscle - prevents urination

Question 30

Process of micturition (6 steps)

Answer 30

1. bladder fills and distends - activates stretch receptors which signal micturition reflex 2. impulses sent via parasympathetic axons to internal sphincer and detrusor muscle 3. internal urethral sphincter smooth muscle relaxes and detrusor muscle contracts 4. Person's conscious decision to urinate causes relaxation of external urethral sphincter 5. Contractions o abdominal and respiratory muscles help empty/void bladder 6. Detrusor muscle relaxes and micturition reflex centre is inactivated