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Chapters 42 & 44 (Osmoregulation and Excretion (osmosis…
Chapters 42 & 44
Osmoregulation and Excretion
osmosis
osmoregulation: the process by which animals control solute concentration and balance water gain and loss
osmolarity: the unit of measurement solute concentration; the number of moles of solute per liter of solution
hyperosmotic: higher solute concentration, lower H2O concentration
hyposmotic: lower solute concentration, higher H2O concentration
isoosmotic; two solutions with the same osmolarity
moves from higher concentration to lower concentration; net flow
freshwater and marine animals
freshwater: body fluid must be hyperosmotic since the salt content around them is so low
water balance is achieved by excreting large amounts of dilute urine and drinking almost no water
salts lost by diffusion and in the urine are replenished by eating and by salt uptake across the gills
marine: osmolarity is the same as that of seawater
balance water loss by drinking seawater and the excess salts ingested with seawater are eliminated through the gills and kidneys
wastes produced by organism
urea: terrestrial animals that have a lot of energy; mammals, most amphibians, sharks, and bony fishes
the product of an energy-consuming metabolic cycle that combines ammonia with carbon dioxide in the liver
uric acid: birds, reptiles, insects, land snails
relatively nontoxic and does not dissolve in water; little water loss; need more energy to produce uric acid than urea
ammonia- animals that need access to lots of water; aquatic species, bony fishes
ammonia molecules pass through membranes and are lost by diffusion to surrounding water; toxic
excretory system
kidneys: a pair of organs that transport and store urine
ureter: two ducts connected to the kidneys that transport urine to the urinary bladder
urinary bladder: a common sac that holds urine
urethra: tube that drains urine from bladder and out of the body
nephron
functional unit of vertebrate kidneys that contains part of the renal cortex and renal medulla
renal cortex: outer layer
renal medulla: inner layer
cortical nephrons: reach only a short distance into the medulla; 85% of nephrons
juxtamedullary nephrons: extend deep into the medulla; production of urine that is hyperosmotic to body fluid, helps water conservation in mammals
Circulation and Gas Exchange
types of circulatory systems
open circulatory system
the circulatory fluid (hemolymph) is also the interstitial fluid that bathes body cells
arthropods (grasshoppers), molluscs (clams)
heart contractions pump hemolymph through the circulatory vessels into interconnected sinuses (spaces surrounding the organs
the hemolymph and body cells exchange gases and other chemicals within the sinuses
relaxation of the heart draws hemolymph back in through pores, which have valves that close when the heart contracts
body movements periodically squeeze the sinuses, helping circulate the hemolymph
benefits
open circulatory systems allow organisms with lower hydrostatic pressure to use less energy than closed systems
spiders: use hydrostatic pressure to extend their legs
doesn't have to have a large surface area
closed circulatory system
a circulatory fluid called blood is confined to vessels and is distinct from the interstitial fluid
chemical exchange occurs between
blood and interstitial fluid
interstitial fluid and body cells
one or more hearts pump blood into large vessels that branch into smaller ones that infiltrate the tissues and organs
annelids (earthworms), cephalopods (squids and octopuses), all vertebrates
benefits
blood pressure is high enough to enable the effective delivery of O2 and nutrients in larger and more active animals
squids and octopuses are speedy
regulating the distribution of blood to different organs
single circulation
blood travels through the body and returns to its starting point in a single circuit
heart consists of two chambers: atrium and ventricle
sharks, rays, bony fish
fish: gill capillaries, 2 chambered heart
blood entering the heart collects to the atrium before transfer to the ventricle
contraction of the ventricle pumps blood to capillary bed in the gills, where there is a net diffusion of O2 into the blood and of CO2 out of the blood
as blood leaves the gills, the capillaries converge into a vessel that carries oxygen-rich blood to capillary beds throughout the body
blood enters veins and returns to the heart after gas exchange in the capillary beds occurs
blood that leaves the heart passes through two capillary beds before returning to the heart
blood pressure drops when blood passes through a capillary bed which, in gills, limits the rate of blood flow in the rest of the animals's body
contraction and relaxation of muscles while swimming help accelerate the slow pace of circulation
double circulation
two circuits of blood flow
amphibians, reptiles, mammals
amphibian: pulmocutaneous circuit contains lung and skin capillaries, 3 chambered heart (2 atriums, 1 ventricle)
mammal: pulmonary circuit contains lung capillaries, 4 chambered heart
a single heart with both pumps simplifies coordination of the pumping cycles
in the pulmonary (reptiles and mammals) and pulmocutaneous (amphibians) circuit, the right side of the heart pumps oxygen-poor blood to the capillary beds of the gas exchange tissues
in the systematic circuit, the left side of the heart pumps oxygen-enriched blood from the gas exchange tissues to capillary beds in organs and tissues throughout the body
circulatory system
arteries: carry blood from the heart to organs throughout the body
arterioles: arteries branch into arterioles which branch into capillaries
veins: the vessels that carry blood back to the heart
venules: capillaries converge into venules which converge into veins
capillaries: microscopic vessels with very thin, porous walls
capillary beds: networks of capillaries that infiltrate tissues, passing within a few cell diameters of every cell in the body
dissolved gases and other chemicals are exchanged by diffusion between the blood and the interstitial fluid around the tissue cells, across the thin walls of capillaries
blood and lymph
blood- 55% plasma, 45% cellular elements
plasma
water: solvent
ions or blood electrolytes (sodium, potassium, calcium, magnesium, chloride, bicarbonate): osmotic balance, pH buffering, and regulation of membrane permeability
plasma proteins: albumin (osmotic balance, pH buffering), immunoglobulins or antibodies (defense), apolipoproteins (lipid transport), fibrinogen (clotting)
cellular elements
leukocytes (white blood cells): defense and immunity
platelets: blood clotting
erythrocytes (red blood cells): transport of O2 and some CO2
function: transportation (O2 and nutrients), protection, regulation
lymph- circulates within the lymphatic system before draining into a pair of large veins at the base of the neck
when the cardiovascular and lymphatic systems join, it completes the recovery of fluid lost from capillaries and the transfer of lipids from the small intestine to the blood
lymph vessels have valves that prevent backflow of fluid
rhythmic contractions of the vessel wall help draw fluid into the small lymphatic vessels
skeletal muscle contractions help move lymph
blood pressure- generated by contraction of a heart ventricle, which exerts a force in all directions
blood flows from areas of higher pressure (away from the heart) to areas of lower pressure
by the time the blood enters the veins, the resistance has dissipated much of the pressure generated by the pumping heart
normal BP for humans: 120/80
120 = contraction
80 = relaxation
respiratory system
gills
fish continuously pump water through its mouth and over its gill arches, using coordinated movements of the jaws and gill cover for ventilation
each gill arch has two rows of gill filaments, composed of flattened plates called lamellae; it has blood flowing through its capillaries which picks up O2 from the water
lungs
the circulatory system transports gases between the lungs and the rest of the body
in mammals, branching ducts convey air to the lungs, located in the thoracic cavity, enclosed by the ribs and diaphragm
nostrils -> nasal cavity -> pharynx -> larynx -> trachea-> bronchi -> bronchioles
skin
every cell in the body is close enough to the external environment that gases can diffuse quickly between any cell and the environment
breathing
muscles: diaphragm, rib muscles
positive pressure: inflate the lungs with forced air flow (how an amphibian ventilates its lungs)
negative pressure: pulling air through their lungs (mammals)
tracheal system
a network of air tubes that branch throughout the body
tracheae, the largest tubes, open to the outside
at the tips of the finest branches, a moist epithelial lining enables gas exchange by diffusion