Chapter 42: Circulation and Gas Exchange

Ms. KlinkhachornApril 29, 2011

AP Biology

The need for a circulatory system

• Need to exchange gases, nutrients, and wastes

• BUT Diffusion is slow and only occurs over small distances

• How do we get around this?

Two Solutions in Nature

1. Organisms with body shapes and sizes that keep almost all of their cells in contact with the environment

– Can have a gastrovascular cavity that help a dual-function (digestion and distribution)

Two Solutions in Nature

2. Organism has a circulatory system– More complex species

• Circulatory systems have 3 parts:– Blood (circulatory fluid)– Vessels (tubes that move the fluid)– Heart (structure that pumps the fluid)

Main Blood Vessel Types

• Arteries– Carry blood away from the heart

• Capillaries– Microscopic vessels (one cell layer thick)– Sites of diffusion

• Veins– Carry blood back to the heart

Parts of the Heart

• Atria (atrium) are heart chambers that receive blood from veins

• Ventricles take blood from the atria and then pump the blood back out

Circulatory Systems Can Vary

• Vary based on the organism• Mammals and birds have hearts with 4

chambers– Reptiles and amphibians have 3– Fish have 2

• In mammals, left side of the heart deals with oxygen-rich blood while right side deals with oxygen-poor blood

Fig. 42-5

Amphibians

Lung and skin capillaries

Pulmocutaneouscircuit

Atrium (A)

Ventricle (V)

Atrium (A)

Systemiccircuit

Right Left

Systemic capillaries

Reptiles (Except Birds)

Lung capillaries

Pulmonarycircuit

Rightsystemicaorta

Right LeftLeftsystemicaorta

Systemic capillaries

A A

VV

Systemic capillaries

Pulmonarycircuit

Systemiccircuit

Right Left

A A

VV

Lung capillaries

Mammals and Birds

Fig. 42-6

Superiorvena cava

Pulmonaryartery

Capillariesof right lung

3

7

3

8

9

24

11

51

10

Aorta

Pulmonaryvein

Right atrium

Right ventricle

Inferiorvena cava

Capillaries ofabdominal organsand hind limbs

Pulmonaryvein

Left atrium

Left ventricle

Aorta

Capillariesof left lung

Pulmonaryartery

Capillaries ofhead andforelimbs

Steps of Circulation in Mammals

1. Blood is pumped from right ventricle to the lungs via the pulmonary artery

2. Blood picks up oxygen in capillary beds of lungs and releases carbon dioxide

3. Blood returns to the left atrium via the pulmonary vein and move into the left ventricle

4. Blood moves through the aorta and ultimately to other places in the body

Steps of Circulation in Mammals

5. Blood travels through body and, in capillary beds, releases oxygen and picks up carbon dioxide

6. Blood returns back to the right atrium of the heart via the vena cava

7. Blood flows into the right ventricle and the cycle restarts

Fig. 42-7

Pulmonary artery

Rightatrium

Semilunarvalve

Atrioventricularvalve

Rightventricle

Leftventricle

Atrioventricularvalve

Leftatrium

Semilunarvalve

Pulmonaryartery

Aorta

Cardiac Cycle

• Cycle of contraction and relaxation = cardiac cycle (time from one beat to the next)– Systole: contraction (pumping) phase – Diastole: relaxation (filling) phase

• Heart rate = beats per minute• SA node is the pacemaker of the heart

– This controls the heart contractions

Blood Pressure

• Typical blood pressure for a 20 year old at rest is 120/70– First number is the systolic pressure– Second number is the diastolic pressure

Blood Components

• Suspended in blood plasma are two types of cells:– Red blood cells (erythrocytes) transport oxygen

via hemoglobin– White blood cells (leukocytes) function as defense

in the immune system• Platelets are fragments of cells that are involved

in clotting

Fig. 42-17

Plasma 55%

Constituent Major functions

Water Solvent forcarrying othersubstances

Ions (blood electrolytes)

Osmotic balance,pH buffering, andregulation ofmembranepermeability

SodiumPotassiumCalciumMagnesiumChlorideBicarbonate

Osmotic balancepH buffering

Clotting

Defense

Plasma proteins

Albumin

Fibrinogen

Immunoglobulins(antibodies)

Substances transported by blood

Nutrients (such as glucose, fatty acids, vitamins)Waste products of metabolismRespiratory gases (O2 and CO2)Hormones

Separatedbloodelements

Cellular elements 45%

Cell type FunctionsNumberper µL (mm3) of blood

Erythrocytes(red blood cells)

5–6 million Transport oxygenand help transportcarbon dioxide

Leukocytes(white blood cells)

5,000–10,000 Defense andimmunity

Basophil

Neutrophil

Eosinophil

Lymphocyte

Monocyte

Platelets Blood clotting250,000–400,000

RBC Structure and Function

• Disc shaped– Maximize surface area for oxygen to bind to

hemoglobin

• Lack nuclei– Gives more space

• Lack mitochondria– Oxygen held isn’t used

Collagen fibersPlateletplug

Platelet releases chemicalsthat make nearby platelets sticky

Clotting factors from:PlateletsDamaged cellsPlasma (factors include calcium, vitamin K)

Prothrombin Thrombin

Fibrinogen Fibrin5 µm

Fibrin clot

Red blood cell

Fig. 42-18-4

Fig. 42-20

Connectivetissue

Smoothmuscle Endothelium Plaque

(a) Normal artery (b) Partly clogged artery50 µm 250 µm

Fig. 42-20a

Connectivetissue

Smoothmuscle Endothelium

(a) Normal artery 50 µm

Fig. 42-20b

Plaque

(b) Partly clogged artery 250 µm

Countercurrent Exchange

• Gills in fish– Water flow through, opposite the direction of

blood flow– Picks up oxygen from the water

Fig. 42-21a

Parapodium (functions as gill)

(a) Marine worm

Fig. 42-21b

Gills

(b) Crayfish

Fig. 42-21c

(c) Sea star

Tube foot

Coelom

Gills

Fig. 42-22

Anatomy of gills

Gillarch

Waterflow Operculum

Gillarch

Gill filamentorganization

Bloodvessels

Oxygen-poor blood

Oxygen-rich blood

Fluid flowthrough

gill filament

Lamella

Blood flow throughcapillaries in lamella

Water flowbetweenlamellae

Countercurrent exchange

PO2 (mm Hg) in water

PO2 (mm Hg) in blood

Net diffu-sion of O2

from waterto blood

150 120 90 60 30

110 80 20Gill filaments

50140

Flow of Oxygen

• Into your mouth or nose• Past the voice box (larynx)• Into the trachea (windpipe)• Into one of the two bronchi• Into a branch called a bronchiole• Into an alveoli

Fig. 42-24

Pharynx

Larynx

(Esophagus)

Trachea

Right lung

Bronchus

Bronchiole

DiaphragmHeart SEM

Leftlung

Nasalcavity

Terminalbronchiole

Branch ofpulmonaryvein(oxygen-richblood)

Branch ofpulmonaryartery(oxygen-poorblood)

Alveoli

ColorizedSEM50 µm 50 µm