circulation & gas exchange

what does the interstitial fluid do

1. provides o2 & nutrients to cells

2. allows co2 & waste to be removed from cells

what does the gas/nutrient exchange system include

• respiratory organ for gas exchange — gills, lungs, skin, tracheal system

• digestive system for nutrients — alimentary canal

purpose of circulatory system

moves the exchanged materials around the body to the interstitial fluid that bathes cells

• consists: blood — pumped through vessels by a heart (2,3 or 4 chambered)

how does a closed circulatory system work

• blood remains in vessels — exchanges 02/co2 with lungs or gills

• nutrients are absorbed from digestive system & delivered into blood

• wastes are delivered to liver & kidneys by the blood

• blood delivers o2 & nutrients to interstitial fluid (not cells)

arterioles

are the smaller branches to arteries (which carry o2 rich blood away from heart)

• are further divided into capillaries (one-celled thick vessels)

  • infiltrate tissues as capitllary beds

  • exchange between blood & intersitial fluid (across capillary walls)

capillaries

converge & form venules — converge to form veins: bring de-oxygenated blood back to the heart

fish circulatory system

2-chambered heart — one atrium & one ventricle

• atria: heart chambers that receive blood & transfer to ventricles

• ventricles: heart chambers that pump blood to capillary beds (against high resistance)

  • pump blood to capillary beds of gills to pick up o2, dumps o2 then picks up co2, then return to atrium

amphibian circulatory system

• 2 atria

• 1 ventricle

  • pump de-oxygenated blood from tissues to skin/lungs — pick up o2

  • comes back to heart & is pumped to tisses

  • o2-rich & o2-poor blood does mix

reptile circulatory system

3-chambered heart, ventricle is almost separated by septum or membrane, almost 4-chambered

• separation of o2-rich & o2-poor is better, but still some mixing

bird & mammal circulatory system

most efficient delivery system — bc high demands, endotherms

• 4-chambered heart

  • right side: handles o2-poor blood (right atrium/ventricle)

  • left side: handles o2-rich blood (left atrium/ventricle)

gas exchange

uptake of o2 from & discharge of co2 to the environment

gas exchange in unicellular & simple animals

occurs over entire surface of the animal — cells are in direct or nearly direct contact to external environment for diffusion

gas exchange in complex animals

need gills or lungs to exchange gases & circulatory system to move gases — lack direct contact to the outside

• respiratory surface = moist, thin layer of cells — separates medium from capillaries

• entire skin can be used as respiratory surface

• movement of o2 & co2 = simple diffusion

advantages & disadvantages of water as respiratory medium

• advantages: respiratory system is easily kept moist

• disadvantages: o2 concentration is relatively low & water is viscous so it takes more energy to move it over gills

advantages & disadvantages of air as respiratory medium

• advantages: relatively high o2 concentration & less dense, less energy needed to move it over the respiratory surface

• disadvantages: respiratory system will continually lose water by evaporation

gills

respiratory structure of aquatic animals — can be simple (everywhere) or confined

• not suited for land: would lose too much water & would collapse bc no force form water

ventilation

process of moving air into & out of respiratory organs

ventilation of gills

ventilate as they swim — water enters mouth, passes through slits in pharynx, flows over gills & exists

• prevents a region of low o2 & a high co2 from forming over gills, maintains concentration gradient

trachael system of insects

system of tubes that branch throughout the body

• large tubes: trachea — open to outside air, have fine tubes to reach each cell

• no transport of o2 or co2 — diffusion brings o2 for respiration

how do different insects ventilate

• large insects: rhythmic body movements — squeeze & expand the trachea

• flying insects: ventilate by contracting & relaxing flight muscles

lungs

invaginated respiratory surfaces restricted to one location from which o2 is transported to the rest of the body by a circulatory system

• amphibians: lungs = small, gas exchange supplemented by diffusion

• birds/most reptiles/mammals: rely only on lungs

how to mammals increase their surface area for gas exchange

lungs branch out to tiny sacs of epithelial tissue — alveoli

process of air passage from environment to lungs

in through nostrils

• passes through pharynx & enters trachea

  • trachea branches into two bronchi — branch into bronchioles

    • tips of bronchioles = alveoli (one cell thick, have capillary bed

positive pressure breathing in frogs

lowers floor of the mouth & expands it — draws in air

• raise the floor of the mouth & push the air into the lungs

negative pressure breathing — mammals

diaphragm & rib muscles contract — expands the chest cavity, increases the volume in lungs

• lowers air pressure — draws in air

• relaxing the diaphragm/rib muscles compresses lungs — increased pressure & forces air out

gas exchange at the lungs

blood entering capillaries of lungs comes from body tissues has lost oxygen & picked up co2

• co2 diffuses out of the blood & into lungs

• oxygen will diffuse into the blood

gas exchange at the tissues

blood entering the tissue capillaries is pumped from left side of heart — coming from lungs, is loaded with oxygen & has dumped co2

• o2 will diffuse into the tissue & co2 into the blood

hemoglobin

carries oxygen — is four subunits with an iron atom — binds oxygen

• when one oxygen binds it creates an affinity for oxygen to bind

relationship between oxygen concentration & % o2 saturation of hemoglobin

small change in o2 concentration causes a huge change in % saturation of hemoglobin

• allows it to load up & give it up

bohr shift

hemoglobin o2 saturation drops when pH drops bc of increased co2 concentration

• give up o2 to raise pH