Circulation and Gas Exchange

The Respiratory System

What is its function? Why is it necessary? GETS oxygen for the body

Needed for cellular respiration GETS RID of carbon dioxide

Produced during cellular respiration Characteristics/Requirements of ALL Gas Exchange Mechanisms: MOIST membranes High surface area-to-volume ratio

An animal’s respiratory surfaces must be large enough to provide oxygen and expel carbon dioxide for the entire body

Respiration in Non-Mammals Small animals (earthworms, etc.) exchange gases by diffusion across its general body surface

Gills are outfoldings of the body surface specialized for gas exchange for aquatic organisms Blood flowing through the capillaries picks up oxygen from the water

Countercurrent Exchange- blood & water flow in opposite directions

Countercurrent Exchange (Aquatic Animals)

Countercurrent exchange allows for the efficient transfer of oxygen to the blood As blood flows through the capillary, it becomes more and more loaded with oxygen

Steep concentration gradient allows for efficient uptake of oxygen

Tracheae

The respiratory system used by insects

Tracheae are air tubes that branch throughout the insect body

The finest branches of the tracheae extend to the surface of nearly every cell, where gas is exchanged by diffusion

Lungs

Lungs are found in terrestrial vertebrates Reptiles, birds, mammals, amphibians

Lungs of mammals have a large enough surface area to carry out gas exchange for the entire body How do the gases get from the lungs throughout the rest of the body, though??

The circulatory system transports the gases throughout the body after they’re exchanged in the lungs

Human Respiratory System

Human Respiratory System

Air enters the lungs by a system of branching ducts Nostrils Pharynx Larynx Trachea (w/ cilia)

2 bronchi Bronchioles Alveoli

Alveoli

Alveoli are clusters of air sacs at the end of bronchioles Alveoli have thin epithelium, which serve as the respiratory surface

Oxygen diffuses from the alveoli into the web of capillaries around each alveolus

The capillaries then transfer the oxygen throughout the body, via the circulatory system

ALVEOLI/CAPILLARY DIAGRAM

Why is the circulatory system necessary?

TRANSPORTATION! Diffusion is not fast enough to transport chemicals throughout an animal’s body

The circulatory system transports fluid throughout the body This solves the problem of diffusion by ensuring that no substance had to diffuse far to enter or leave a cell

Open vs. Closed Circulatory Systems

In open circulatory systems, hemolymph bathes the internal organs directly Insects, arthropods, mollusks

In closed circulatory systems, blood is confined to vessels Blood exchanges materials with the ISF bathing the cells

Earthworms, squids, octopuses, vertebrates

Open vs. Closed Circulatory Systems

Adaptations of the Vertebrate Circulatory System

Fish - Heart with 2 chambers (one atrium, one ventricle)

Amphibians (frogs)- 3-chambered heart (two atria, one ventricle)

Reptiles – (3-chambered with partial septum) Birds/Mammals-4-chambered heart (two atria, two ventricles)

FISHES AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS

Systemic capillaries Systemic capillaries Systemic capillaries Systemic capillaries

Lung capillaries Lung capillariesLung and skin capillariesGill capillaries

Right Left Right Left Right Left

Systemic circuit

Systemic circuit

Pulmocutaneouscircuit

Pulmonarycircuit

Pulmonarycircuit

Systemiccirculation

Vein

Atrium (A)

Heart:ventricle (V)

ArteryGill

circulation

A

V VV VV

A A A AALeft Systemicaorta

Right systemicaorta

Figure 42.4

Vertebrate circulatory systems

Double Pump

Right side pumps to the lungs and back to left atrium (PULMONARY CIRCUIT)

Left side pumps to the entire body and returns blood to right atrium (SYSTEMIC CIRCUIT)

Oxygenated & deoxygenated blood never mix!

The mammalian cardiovascular system

Pulmonary vein

Right atrium

Right ventricle

Posteriorvena cava Capillaries of

abdominal organsand hind limbs

Aorta

Left ventricle

Left atriumPulmonary vein

Pulmonaryartery

Capillariesof left lung

Capillaries ofhead and forelimbs

Anteriorvena cava

Pulmonaryartery

Capillariesof right lung

Aorta

Figure 42.5

1

10

11

5

4

6

2

9

33

7

8

The Heart About the size of a clenched fist

Made up of mostly cardiac muscle tissue: striated with branches; involuntary

Atria have thin walls, ventricles have thicker walls Why?? Ventricles must pump blood through the pulmonary & systemic circuits. (LONG DISTANCE)

The Heart: Structure and Function

AV Valves: Located between each atrium and ventricle

Keep blood from flowing back into the atria

Semilunar Valves: Located at the exits of the heart (at the bottom of each ventricle)

Prevent blood from flowing back into the ventricles

The Human Heart

Blood Vessels

Arteries carry blood away from the heart to organs throughout the body Arteries are thicker than veins…why?? Thick layer of smooth muscle (nonstriated; involuntary)+ elastic tissue

Veins return blood to the heart Categorized by direction of flow, NOT whether or not they contain oxygen

Thinner layer of smooth muscle; VALVES to prevent back flow of blood; not very elastic

Capillaries are microscopic vessels with very thin, porous walls

Figure 42.9

Artery Vein

100 µm

Artery Vein

Arteriole

Venule

Connectivetissue

Smoothmuscle

Endothelium

Connectivetissue

Smoothmuscle

Endothelium

Valve

Endothelium

Basementmembrane

Capillary

Venous Transport

In the thinner-walled veins Blood flows back to the heart

mainly as a result of muscle action

Direction of blood flowin vein (toward heart)

Valve (open)

Skeletal muscle

Valve (closed)

Capillary Exchange

The capillary wall is a single layer of flattened cells

The transfer of substances occurs between the capillaries and the interstitial fluid (which bathes the cells) This occurs by bulk flow, the movement of fluid due to pressure

Water, sugars, salts, oxygen, and urea pass through the capillary walls

Capillary Exchange

Velocity, B. Pressure, & Area

The velocity of blood flow varies in the circulatory system And is slowest in the capillary beds as a result of the high resistance and large total cross-sectional area

Figure 42.11

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orta

Art

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Cap

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ies

Ven

ules

Vei

ns

Ven

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avae

Pre

ssur

e (m

m H

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eloc

ity (

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a (c

m2)

Systolicpressure

Diastolicpressure

50403020100

120100806040200

Blood Pressure Systolic pressure

Is the pressure in the arteries during ventricular systole

Is the highest pressure in the arteries Diastolic pressure

Is the pressure in the arteries during diastole

Is lower than systolic pressure

Measured with sphygmomanometer Normal pressure = 120/80 mm Hg

Control of the Heart

Cardiac muscles contract (systole) and relax (diastole) in a rhythmic cycle

The sinoatrial node (SA node), also known as the pacemaker, maintains the heart’s pumping rhythm by setting the rate at which all cardiac muscles contract

Control of the Heart

Cardiac Cycle

Atria VentriclesEKGSystole DiastoleP waveDiastoleSystole QRSwaveDiastoleDiastoleT wave

The cardiac cycle

Figure 42.7

Semilunarvalvesclosed

AV valvesopen

AV valvesclosed

Semilunarvalvesopen

Atrial and ventricular diastole

1

Atrial systole; ventricular diastole

2

Ventricular systole; atrial diastole

3

0.1 sec

0.3 sec0.4 sec

The Structure of Blood

Blood is made up of plasma, red blood cells, white blood cells, and platelets

Plasma, which makes up about 55% of blood volume, is mostly water Plasma also contains antibodies Plasma also contains fibrinogens, proteins that act as clotting factors

Fibrinogen (inactive) is a protein in blood that is converted into fibrin (active), when needed

Thrombin is the enzyme that activates the fibrinogen. K & Ca are important minerals for clotting reaction to occur.

Hemophilia is an inherited disorder, characterized by excessive bleeding from minor cuts and bruises

People with hemophilia can die from minor cuts

The Structure of Blood

Red Blood Cells (Erythrocytes) The human body contains 25 trillion red blood cells

Major function is to transport oxygen

Contains hemoglobin, an iron-containing protein that carries oxygen

Red blood cells are produced in the bone marrow

Hemoglobin Carries Oxygen

Like all respiratory pigments Hemoglobin must reversibly bind O2, loading O2 in the lungs and unloading it in other parts of the body

Heme group Iron atom

O2 loadedin lungs

O2 unloadedIn tissues

Polypeptide chain

O2

O2

Figure 42.28

Carbon Dioxide Transport

Small amount binds to hemoglobin to form carboxyhemoglobin.

MOST is transported as bicarbonate ion:

CO2 + H2O H2CO3H+ + HCO3-

Serves as a buffer to control pH of blood.

pH = 7.4

The Structure of Blood

White blood cells (leukocytes) Major function is to fight infection 5 major types

Monocytes, neutrophils, basophils, eosinophils, lymphocytes

White blood cells spend most of their time patrolling through the ISF and the lymphatic system, where most of the battles against pathogens are waged

The Structure of Blood

Platelets (Thrombocytes) Platelets are fragments of cells Platelets enter the blood and function in the process of blood clotting

Blood: An Overview

Cardiovascular Disease

Cardiovascular disease (diseases of the heart and blood vessels) cause more than half of all deaths in the US

Heart attack: Death of cardiac muscle tissue as a result of blockage of a coronary artery

Stroke: Death of nervous tissue in the brain, resulting from blockage of arteries in the head

Artherosclerosis

Plaque (cholesterol and triglycerides/fats) deposit in blood vessels

Can lead to stroke or heart attack.