Urinary systems and electrolyte balance

Question 1

What are the functions of the urinary system?

Answer 1

• removal of waste products
• regulation of volume and solute concentration of blood plasma
• elimination of waste products into the environment

Question 2

What are the components of the urinary system?

Answer 2

• kidneys
• ureters
• bladder
• urethra

Question 3

Describe the anatomical location of the kidneys

Answer 3

• located on either side of the midline, on the posterior abdominal wall
• T12 - L3 (T= thoracic vertebra and L= lumbar vertebra)
• left kidney is located slightly higher than the right kidney
• lie behind the parietal peritoneum = retroperitoneal organs and are surrounded by adipose tissue

Question 4

Describe the anatomical location of the adrenal glands

Answer 4

not part of the urinary system and located on the superior pole of the kidneys

Question 5

What is the function of the cortex

Answer 5

• corticosteroids
• aldosterone
• sodium and water retention
• increases blood pressure and volume

Question 6

What is the function of the medulla

Answer 6

• secretes adrenaline and noradrenaline
• involved in fight or flight response

Question 7

Describe the size and shape of the kidneys

Answer 7

• 150g, 10cm long, 5 cm wide, 2.5cm thick
• indented ovoid - bean shaped

Question 8

Describe the components of the renal lobe

Answer 8

renal cortex –> proximal and distal parts of the nephron and collecting ducts (medullary rays)
renal medulla (pyramids) –> loop of henle and collecting ducts (collection and delivery of urine)

Question 9

Describe the ureters

Answer 9

• hollow muscular tubes, propel urine from the kidneys to the bladder
• located in both the abdomen and pelvis
• retroperitoneal
• congenital anomalies - duplex ureter
• enter bladder obliquely
• when bladder is full - prevent backflow of urine into the ureters, compression closes off the ureters acting as valves

Question 10

Describe the urinary bladder

Answer 10

• apex - points toward the pubic symphysis
• fundus - opposite the apex and formed by the posterior wall
• usual capacity of 0.75 liters- obstruction to outflow leads to enlargement of 6-7 liters
• world record of 21 liters

Question 11

Describe the female urethra

Answer 11

• 4-5cm long - urinary tract infection much more common
• passes through pelvic floor and opens anterior to vagina

Question 12

Describe the female urethra sphincters

Answer 12

• internal urethral sphincter - junction between bladder and urethra
• external urethral sphincter - immediately inferior to the internal urethral sphincter

Question 13

Describe the male urethra

Answer 13

• 20cm in length
• S- shaped
• 4 parts
• pre-prostatic
• prostatic
• membranous
• penile

Question 14

Describe the male urethral sphincter

Answer 14

• internal urethral sphincter - junction between the bladder and urethra
• prevents reflux of semen into the bladder
• external urethral sphincter - inferior to the prostate

Question 15

What are the two body fluid compartments?

Answer 15

• intracellular fluid
• extracellular fluid = interstitial fluid + blood plasma

Question 16

What are the major sites of ions and water exchange

Answer 16

• skin
• respiratory systems
• digestive systems
• excretory systems

Question 17

Describe osmoregulation in freshwater fish

Answer 17

• uptake of water and some ions in food
• osmotic water gain through gills and other parts of the body surface
• uptake of slat ions by gills
• excretion of large amounts of water in dilute urine from kidneys
• must continually use energy to expel water

Question 18

Where are aquaporins found?

Answer 18

prominent in brain, RBCs, kidney and skin and bladder of amphibians

Question 19

Describe how desert kangaroo rats do not dehydrate

Answer 19

they are able to gain metabolic water in a net fashion by metabolising barley

Question 20

What three types of regulation are possible?

Answer 20

• osmotic regulation
• ionic regulation
• volume regulation

Question 21

What is the difference between obligatory and regulated exchanges of ions and water

Answer 21

obligatory - responses to factors beyond animal’s physiological control
regulated - physiologically controlled and required for maintaining homeostasis

Question 22

Why are freshwater animals classified as hyperosmotic regulators?

Answer 22

They regulate their blood osmotic pressures at levels hyperosmotic to freshwater

Question 23

Describe the challenges freshwater organisms face

Answer 23

volume regulation - water constantly enters the body due to osmotic gradient
osmotic regulation - entering water decreases osmotic pressure of extracellular fluid
ionic regulation - ions are moving from the extracellular fluid to surrounding water and entering water dilutes extracellular fluid

Question 24

Why are the challenges to ionic regulation and osmoregulation greater for marine teleost fishes?

Answer 24

There is a higher osmotic gradient between the environment and intracellular fluids compared to freshwater teleost fishes

Question 25

Describe the prevention of water loss and the function of the kidneys in marine animals

Answer 25

- integuments and epithelia of marine fishes are poorly penetrable to water - marine fishes drink water and absorb it via gut epithelia, co-absorption of monovalent ions aggravates ionic regulation - kidneys of marine fishes produce small amounts of isosmotic urine - principal role of kidneys is excretion of divalent ions, while excretion of Na+, Cl- and nitrogenous products of metabolism takes place in gills

Question 26

Describe the difference between stenohaline animals and euryhaline animals

Answer 26

stenohaline animals - tolerate only narrow range of NaCl euryhaline animals - tolerate wide variance of NaCl

Question 27

Describe water loss on terrestrial animals

Answer 27

- low permeability of the integument - retention of water in the respiratory system - production of concentrated excretory fluids - reduction of the amount of solutes excreted with these fluids - tight regulation of fluid production in changeable conditions

Question 28

List the four processes involved in urine formation in the mammalian kidneys

Answer 28

- filtration - reabsorption - secretion - excretion (micturition)

Question 29

Describe filtration in the glomerulus

Answer 29

- glomerular tuft - capillary loops - constant vasoactivity - hydrostatic pressure gradient - filtration barrier consists of 3 layers - glomerular filtration rate is 180L/day - charge and size selectivity of basement membrane

Question 30

What is the starling principal of fluid exchange?

Answer 30

the direction of fluid flow across a capillary wall is the result of net filtration pressure

Question 31

Describe how blood pressure is maintained when osmolarity is reduced

Answer 31

- reduction in osmolarity of filtrate - vasodilation - macula densa cells sense - release of renin - blood pressure returns to normal

Question 32

Describe how blood pressure is maintained when osmolarity is increased

Answer 32

- osmolarity increases - vasoconstriction - blood pressure returns to normal

Question 33

Describe the regulation of glomerular filtration and tubular reclamation

Answer 33

- juxtaglomerular apparatus - macula densa - detect flow in tubule lumen - juxtaglomerular cells - line afferent arteriole - produce renin

Question 34

Describe the features of tubule epithelial cells

Answer 34

- relatively impermeable - composition of lipid bilayer - tight junctions - prevent paracellular transport - polarity - certain proteins can be directed to apical/basolateral membrane

Question 35

Describe the process of reabsorption in the PCT

Answer 35

- reabsorption of water, Na+ and Cl- from primary urine - at the end of the PCT the tubular fluid is isosmotic to ISF and plasma