Urinary System/Water Physiology

70-80% water

vertebrate bodies contain __________.

salt ions

Many ________ important for body function are dissolved in water.

Water balance

keeping from drying out or getting flooded

Salt balance

keeping from getting to salty or not salty enough

Osmosis

movement of water along solute concentrations

Kidneys

Key osmoregulator; main organ for excretion of nitrogenous wastes (filtration, reabsorbtion, secretion)

Nephron

Functional unit of the kidney; contains glomerulus (filter), Bowmans capsule (collects ultrafiltrate), proximal tubule (site of reabsorbtion), Loop of Henle (water reabsorbtion and release of excess ions), distal tubule (site of waste secretion), collecting ducts (collects urine and directs it to urinary system, controls the concentration)

glomerulus

filters the blood, leaky capillaries produce ultrafiltrate

Bowmans capsule

site of collection for ultrafiltrate

proximal tubule

site of reabsorbtion for nutrients and ions

Loop of Henle

Descending limb: main site of water resorbtion, ascending limb: active removal of exvess ions

Distal tubule

site of waste secretion (nitrogenous wastes, urine volume reduction)

Collecting ducts

collects urine, controls concentration, sends to urinary system

Discharged through urethra

where does the urine exit the body in mammals

Birds have _____ urinary bladders?

zero (adaptation for flight)

Solutions of marine fish to maintain osmotic balance

1) Be as salty as the environment (hagfish) 2) Have as high osmotic pressure as the environment (cartilagenous fish using urea) 3) Have mechanisms to counteract water loss and salt gain (bony fish using chloride cells to pump out salt)

Solutions of freshwater fish to maintain osmotic balance

do not drink water, kidney produces large amounts of dilute urine, salt is actively pumped through skin by chloride cells (trying to maintain levels of salt)

Osmotic regulatory mechanisms in amphibians

do not drink water, kidney produces large amounts of dilute urine, salt is actively pumped through skin (trying to maintain levels of salt)

Stenohaline (narrow salt)

cannot tolerate a large range of salinity and live in constant environments (marine or freshwater)

Euryhaline (wide salt)

Can tolerate a large range of salinity and can move between marine and freshwater environments

Diadromous

migrate between fresh and salt water

catadromous

life mostly in freshwater than migrate to spawn in saltwater (Atlantic eel)

anadromous

most adult life in saltwater then migrate to spawn in freshwater (salmon)

Osmostic regulation of terrestrial vertebrates

1) produce concentrated urine 2) produce very dry feces 3) decrease evaporative water loss through lungs and skin

10-20% of their body mass

Mammals cannot tolerate losses of water over __________.

Adaptations of mamals to prevent water loss

Resistant skin (scales, plates, hair, feathers), behavioral adaptations (nocturnal, burrowing), reducing moisture of exhaled air (turbinates and concurrent heat exchange), Poikilothermy (little need to eliminate excess heat)