Zoology 101 Exam 3: Gas Exhange Lecture

Gas Exhange

• The uptake of O2 from the environment (to produce energy) and the expulsion of CO2 into the environment (getting rid of waste)

• Requires specialized exchange surfaces

Which gases are exhanged during respiration

Oxygen (O2) and carbon dioxide (CO2)

Diffusion

• The passive movement of oxygen (O2) and carbon dioxide (CO2) across respiratory membranes driven by partial pressure gradient ( region of higher partial pressure to region of lower partial pressure - down the partial pressure gradient)

Where does O2 and CO2 move through in diffusion with gas exchange

• O2 moves into low concentration inside the blood cell

• CO2 moves from high pressure blood cell to outside of environment

What is required for gases to diffuse across a surface

Moist, thin membrane with large surface area

Passive Respiratory Systems

• Respiratory compartments open to environment across entire body

• Drives pressure gradient

• Gas exchange due to pressure gradients

Active Respiratory Systems

• Dedicated locations for respiratory compartments

• Gas exhchange requires ventilation: Movement of a respiratory medium across respiratory surface

What do insects use to extract gas from their environment?

• Spiracles

• Tracheal system

• Ventilation through movement

Spiracles - Insects

Holes in insect’s body surfaces that allow air to enter

Tracheal system - Insects

• Network of arborized tubes which brings air close to most of the body cells of the insect

• Carries gas to its needed location

How do insects perform gas exchange?

• Ventilation

• Tracheal system

How do animals with gills perform sufficient gas exchange?

1) Large surface area - Gill filaments (a lot of folds increases surface area) and lamellae

2) Ventilation - One-way flow of water (oxygen-containing medium) over gills (respiratory surface)

3) Gas exchange occurs via countercurrent exchange in the lamallea of the gills

Where does gas exchange occur via gills?

Lamella

Countercurrent Exchange

Water and blood flow in opposite directions setting up a concentration gradient that causes oxygen from water to enter the blood stream efficiently.

How do birds perform gas exchange?

• One-way flow of air (only use fresh air)

• Two-cycle ventilation (Require a breaths to move y units of air)

• Crosscurrent exchange

How do birds perform gas exchange (One-way flow of air)

Air sacs and lungs (infoldings of body) keep fresh air from mixing with stale air

How do birds perform gas exhange (Ventilation)

• Flow of oxygen-containing medium across respiratory surface

• One-way flow of air over blood capillaries through parabronchi within

Crosscurrent Exchange

• Air and blood pathways cross allowing oxygen to enter part of the capillaries efficiently

• Air and blood flow aren’t in opposite directions

How do amphibians perform gas exchange?

• Ventilation through passive diffusion, movement, and inspiration/expiration

• Skin, gills, and lungs all possible respiratory organs dependent on species and stage of life.

How do amphibians perform gas exchange - Large surface area

Skin as respiratory organ

How do amphibians perform gas exhange - Ventilation

• Passive diffusion from air contacting moist

Respiratory Medium - Fish

Water - Contains a lot less oxygen compared to air

Respiratory Surface - Fish

Lamella in Gills

Ventilation Mechanism - Fish

Mouth movements and swimming brings one-way flow of water over gills

Direction of Blood Flow - Fish

Blood flows through gill capillaries in the opposite direction to water flowing over gill lamellae (countercurrent exchange)

Respiratory Medium - Grasshopper

Air (atmospheric oxygen)

• Enters through spiracles

Respiratory Surface - Grasshopper

Parabronchi in lungs

Ventilation mechanism - Grasshopper

Body movement allows air to enter the body through spiracles

Respiratory Medium - Bird

Air

One-way flow of air

Two-cycle ventilation

One-way flow of air - bird

Use of fresh air only, no stale air (air that has already gone through gas exchange)

Two-cycle ventilation - Bird

Requires a amount of breaths to y unit of air

Respiratory Surface - Bird

first inhalation - posterior air sacs (store and move fresh air) - lungs - anterior air sacs (holds stale air thats released into environment)

Ventilation Mechanism - Bird

• Negative pressure

• One way air flow through air sacs and lungs

Respiratory Medium - Human

Air

Respiratory Surface - Human

Alveoli in lungs

Ventilation mechanism - Humans

• Negative pressure breathing

• Two-way tidal air flows through lungs

Negative pressure breathing - Humans

Pulling air - vaccum effect

Contraction - Atmospheric pressure is greater than lung interior pressure bringing air in

Relaxation: Atmospheric pressure is less than lung interior pressure allowing air to travel out

Tidal exchange - Humans

• Mixing of old and new air not as efficient method of exchange

• Only occurs across some legth of the alveolar capillary ( limited area)

• Oxygen enters the blood and carbon dioxide exits the blood in the lungs during in and out breathing

Ranking of modes of exchange (efficiency wise)

• Countercurrent exchange

• Cross-current exchange

• Tidal exchange

2 main functions of circulatory systems

• Transport and exchange respiratory gases

• Transport nutrients, hormones, and immune cells to critical sites

Do all animals have circulatory systems?

• No some use diffusion of gases and nutrients because they are thin, flat, and have a gastrovascular cavity inside of their body providing lots of exchange surface

• live in moist environments

• Gastrovascular cavity important

3 main features of circulatory systems?

• Circulating fluid (blood or hemolymph)

• Muscular pump (heart)

• Tubes/vessels

Open circulatory system

• Common in invertebrates (i.e. insects and other athropods)

• Fluid: Hemolymph

• Arteries but no veins

• Ostia

Primary function of open circulatory systems

Transport nutrients and waste (not gas exchange)

Ostia

Allow Hemolymph to diffuse back into the heart (valves close them when the heart contracts)

Open Circulatory System Visual

Closed Circulatory Systems

• Found in all vertebrates and some invertebrates

• Blood: Circualtory fluid

• Fluid is contained within/doesn’t leave vessels

• Pump: Heart

• Instertitual fluid surrounds cells that are outside of vessels/heart

Closed Circulatory Systems: Primary Functions

• Gas exchange

• Resource transport

Closed Circulatory System Diagram

Hemolymph

• Mixture of blood and interstitual fluid

• Distinct from blood and interstitual fluid found in organisms with closed circulatory systems

Arteries Function

Move blood away from the heart

Built to absorb and dampen busatile flow

Arteries Structure

Thick muscular walls (smooth muscle) that can withstand the pressure of blood coming from the heart.

Capillaries

Where exchange occurs C

Capillary Walls Structure

Single, thin layer of cells to facilitate exchange

Capillary beds

Provide a large surface area for exchangeW

Why does blood flow slow down when going through capillary beds?

when all of the capillaries in a bed are considered, the diameter through a capillary bed is larger, so the velocity decreases

Why is the slowed down blood flow through capillary beds advantegous for organisms?

The capillary beds are where exchange occurs

Slower flow = more time for exchange

Type of heart - Fish

Two-chambered heart

Structure of 2 chambered heart

One atrium (where blood enters; cycle restarts), one ventricle

Type of blood circulation in 2 chambered heart

Single, blood goes through two capillary beds, passes through the heart once per “turn” throughout the entire cirulatory system

Disadvantages of the 2 chambered heart

Sluggish blood flow through systemic capillaries

Where does oxygenated blood travel to in the fish circulatory system

• the body capillaries

• none in heart

• in capillary beds

Fish Two-chambered heart Visual

Which animals have a 3 chambered heart

Amphibians

Structure of the 3 chambered heart?

2 atria one ventricle

What type of circulation occurs within the 3 chambered heart?

Double circulation

Double circulation - 3 chambered heart

Blood goes through 2 capillary beds with pump of heart between each bed, pulmocutaneous and systemic circuit

Disadvantage of the 3 chambered heart

Mixing of oxygenated and deoxygenated blood, but allows for intermittent breathing

Advantage of the 3 chambered heart

More vigorous blood flow than single circuit, intermittent breathers

3 chambered heart visual

What animals have a 4 chambered heart?

Mammals, birds

Structure of the 4-chambered heart?

Two atria and two ventricles

What do the right ventricles do in the 4 chambered heart?

Sneds blood to lung

What do left ventricles do in the 4 chambered heart?

Sends blood to capillaries

What type of circulation do 4-chambered hearts use?

Double: Blood goes through two capillary beds with pump of heart between each bed, pulmonary and systemic circuit

Advantages of 4 chambered heart?

No mixing of oxygenated and deoxygenated blood, vigorous blood flow

Structure of 4 chambered heart

4 major components of Blood

• Plasma’

• Red blood cells

• Platelets

• White blood cells

Plasma (Blood component)

Liquid portion → Contains dissolved nutrients, hormones, gases

Red blood cells (Blood component)

Transports oxygen

Platelets (Blood component)

Helps form blood clots

White blood cells

Immune defenses against invaders

Function of red blood cell (erythrocite)

Transports almost all of the oxygen we bring into our body

Hemoglobin

Protein where majority of oxygen is bound to

Cooperative Binding of oxygen to hemoglobin

Hemoglobin has 4 subunits, each binds one molecule of O2

Once one molecule of oxygen binds, the next 3 molecules bind in quick succession

Binding of first O2 changes the shape of hemoglobin

Making hemoglobin have a higher affinity for O2 than when none is bound

O2 unbinds from hemoglobin in a cooperative manner - once the first O2 leaves, the others then leave in quick succession

Respiratory Adaptations found in deep-sea diving animals: Weddel Seal

More blood (can store more oxygen), more myoglobin, blood is not routed to muscles when they dive (muscles use oxygen stored in myoglobin, while other tissues use oxygen stored in hemoglobin to blood stream

Respiratory Adaptation found in Humans

Enlarged spleen leads to increased diving endurance

Spleen: Stores oxygenated blood cells, and then releases them into the bloodstream during dives.

Myoglobin

Oxygen-storing protein found in muscles

Cardiac Output

• Measure of the total volume the heart pumps every minute

• Heart rate to stroke volume

• CO = HR x SV

Stroke Volume (SV)

Volume of blood ejected from left ventricle/beat

Aerobic excercise training

Has been shown to increase SV which reduces resting Heart Rate

Increasing Cardiac output

Helps maintain elasticity of arteries

Heart Failure

Heart’s inability to provide enough blood ( and oxygen and nutrients) to the tissues

Left ventricular failure (heart failure)

• more common

• Can cause pulmonary edema

• Swelling/fluid retention

Right ventricular failure (heart failure)

Can cause swelling/edema in the legs

Other systemic circulation

Veins

Carry blood back to the heart

Capillaries/capillary beds

Small vessels in the tissues

Sites of gas and nutrient/waste exchange

Massive total surface area

Slowest blood velocity