Circulation

Did you know?

• In one day, blood travels 12,000 miles.• A capillary is just wide enough for cells to pass

through single file.• No blood flows through cartilage. This makes

cartilage slow to heal.• Grab a tennis ball and squeeze it tightly –

that’s how hard the human heart works.

Did you know?

• Bones of the rib cage are a major supplier of the body’s red blood cells.

• Adults have about 4 to 5 quarts of blood in circulation.

• A red blood cell makes approximately 250,000 trips around the circulatory system before dying

Did you know?

• Anger and fear increase the heart rate by about 30 to 40 beats per minute

• Individual heart muscle fibers grown in a cell culture beat spontaneously.

• All the blood vessels, laid end to end would measure 60,000 miles.

Do the math…

• Your heart beats about 100,000 times per day– 35 million times per year– Almost 3 billion times in an average lifespan

Did you know?

• Heart pumps blood through the aorta at about 1 mile per hour.

• The average blood temperature is 100.4oF• Blood leaving the lungs is bright red, blood

returning to the heart is dark maroon.• During exercise, more blood than usual flows

to skeletal muscles and less to the gut

Did you know?

• People giving CPR should focus on chest compressions; organs can live for several minutes on oxygen already in the blood.

• Fetal blood never carries sickle-cell anemia.• Heart disorders account for four out of five

hospitalizations in the elderly.• Heart patients have regrown healthy heart

tissue from their own stem cells.

Did you know?

• HUMAN BLOOD IS NEVER BLUE. – Does change color as it circulates– Veins look blue because the overlying tissues filter

out red light at that dedpth

Three basic jobs:

• Transportation– Oxygen, nutrients, hormones, waste products

• Protection– Immune cells, platelets, clotting agents

• Cooling– Disperses heat around the body

Superior vena cava

Pulmonaryartery

Capillariesof right lung

Pulmonaryvein

Aorta

Inferiorvena cava

Right ventricle

Capillaries ofabdominal organsand hind limbs

Right atrium

Aorta

Left ventricle

Left atrium

Pulmonary vein

Pulmonaryartery

Capillariesof left lung

Capillaries ofhead and forelimbs

Figure 42.6

Heart: central engine

• Left side pumps blood to all parts of the body except lungs– Oxygen rich blood from lungs

• Right side supplies lungs only– Collects oxygen-poor blood from blood and pumps

it to lungs for oxygenation

• Two closed networks of blood vessels

Figure 42.3

(a) An open circulatory system

Heart

Hemolymph in sinusessurrounding organs

Pores

Tubular heart

Dorsalvessel

(main heart)

Auxiliaryhearts

Small branchvessels ineach organ

Ventral vessels

Blood

Interstitial fluid

Heart

(b) A closed circulatory system

Open and Closed Circulatory Systems

• In insects, other arthropods, and most molluscs, blood bathes the organs directly in an open circulatory system

• In an open circulatory system, there is no distinction between blood and interstitial fluid, and this general body fluid is called hemolymph

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• In a closed circulatory system, blood is confined to vessels and is distinct from the interstitial fluid

• Closed systems are more efficient at transporting circulatory fluids to tissues and cells

• Annelids, cephalopods, and vertebrates have closed circulatory systems

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Back to mammalian circulatory system

• Largest blood vessels are arteries: carry blood away from heart

• Arteries branch out into arterioles, which lead to capillaries

• Capillaries: site of oxygen and nutrient exchange, tiniest pathways

• Capillaries merge into venules, which connect to larger veins

• Carry blood back to the heart

• Takes about one minute for each blood cell to make a circuit of the body.

Deep vein thrombosis

• Side effect of immobility• Caused by blood flowing slowly or pooling in deep

veins in lower legs or thighs• Unable to wash away clotting factors = blood clot

(thrombus) can form – blocks circulation• Limb becomes tender, swollen, hot, red• Clot can break away and travel to brain (cause stroke)

or to lung, heart, or other areas• Anticoagulants, compression stockings, periodic

breaks to stand up and get blood moving

Blood

• Connective tissue• Red blood cells, white blood cells, platelets• Cells float in a liquid (plasma)• Plasma: mostly water, includes nutrients,

hormones, gases, and other substances = 55% of bloodstream

Figure 42.17

Plasma 55%

Constituent Major functions

Water

Ions (bloodelectrolytes)SodiumPotassiumCalciumMagnesiumChlorideBicarbonate

Solvent forcarrying othersubstances

Osmotic balance,pH buffering,and regulationof membranepermeability

Plasma proteinsOsmotic balance,pH buffering

Albumin

Fibrinogen

Immunoglobulins(antibodies)

Clotting

Defense

Substances transported by blood

NutrientsWaste productsRespiratory gasesHormones

Separatedbloodelements

Basophils

Neutrophils Monocytes

Lymphocytes

Eosinophils

Platelets

Erythrocytes (red blood cells) 5–6 million

250,000–400,000 Bloodclotting

Transportof O2 and

some CO2

Defense andimmunity

FunctionsNumber per L(mm3) of blood

Cell type

Cellular elements 45%

Leukocytes (white blood cells) 5,000–10,000

Red Blood Cells

• Carry respiratory gases to and from the body’s tissues.

• Hemoglobin molecules within RBC = red pigment

• Lack a nucleus• Last only about 120 days• Die at a rate of 2 million per second• Produced in bone marrow

Heart

• 4 chambers• Size of a large fist• Weighs about 8 ounces in women and 10

ounces in adults• 2 atria (entry hall)

– Separated by thin wall called interatrial septum– Collecting room for returning blood– Pump through valves to ventricles

Heart continued

• 2 ventricles (little belly)– More muscular– Pump blood out of the heart– Separated by interventricular septum

Pacemaker

• Heart’s electrical signal begins in the sinoatrial node – heart’s natural pacemaker, located near top right atrium

• Made up of autorhythmic fibers – specialized heart cells that take in and expel calcium and other electrolytes to regularly change electrical charge

• Electrical impulse produced by cells of the SA node spread through walls of the atria by moving one cardiac cell to the next via gap junctions

• Signal makes muscle cells of atria contract in a sequenced fashion – presses blood into the ventricles

• The pacemaker is regulated by two portions of the nervous system: the sympathetic and parasympathetic divisions

• The sympathetic division speeds up the pacemaker• The parasympathetic division slows down the

pacemaker• The pacemaker is also regulated by hormones and

temperature

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Shoveling snow = deadly risks• ".... that when healthy young men shoveled snow, their heart rate and blood

pressure increased more than when they exercised on a treadmill. "Combine this with cold air, which causes arteries to constrict and decrease blood supply, you have a perfect storm for a heart attack," Dr. Barry Franklin, director of cardiac rehab at Beaumont Hospital says.

• "Shoveling snow raises blood pressure and heart rate more than some other forms of exercise cold air constricts blood vessels, cardiac risks are higher in early morning, rare exercise for sedentary over-55s.Snow shoveling is particularly strenuous because it uses arm work, which is more taxing than leg work. Straining to move wet and heavy snow is particularly likely to cause a surge in heart rate and blood pressure, Franklin says.

• Many people hold their breath during the hard work, which also puts a strain on the body. In addition, the prime time for snow clearance is between 6am and 10am which is when circadian fluctuations make us more vulnerable to heart attacks."

Circulation

• Blood moves from regions of higher pressure to regions of lower pressure

One heart beat = one cardiac cyle

• Oxygen-poor blood enters the right atrium• Pumped to right ventricle• Pumped through pulmonary artery to lung• Returns via pulmonary vein to left atrium• Enters left ventricle• Exits to the body via aorta

• Lasts about 0.8 seconds, pumps about 2 ounces (70 ml) of blood out of each ventricle

Superior vena cava

Pulmonaryartery

Capillariesof right lung

Pulmonaryvein

Aorta

Inferiorvena cava

Right ventricle

Capillaries ofabdominal organsand hind limbs

Right atrium

Aorta

Left ventricle

Left atrium

Pulmonary vein

Pulmonaryartery

Capillariesof left lung

Capillaries ofhead and forelimbs

Figure 42.6

Figure 42.10 Artery

Red blood cells

Endothelium

Artery

Smoothmuscle

Connectivetissue

Capillary

Valve

Vein

Vein

Basal lamina

Endothelium

Smoothmuscle

Connectivetissue

100 m

LM

Venule

15

mL

M

Arteriole

Red blood cell

Capillary

Figure 42.11

Aorta

Arterie

sArte

riole

s

Capill

arie

sVen

ules

Veins

Venae

cava

e

Systolicpressure

Diastolicpressure

020406080

100120

01020304050

Pre

ss

ure

(mm

Hg

)V

elo

cit

y(c

m/s

ec

)A

rea

(c

m2)

01,0002,0003,0004,0005,000

Figure 42.15

INTERSTITIALFLUID Net fluid movement out

Bloodpressure

Osmoticpressure

Arterial endof capillary Direction of blood flow

Venous endof capillary

Body cell

• Electrocardiogram (EKG): measures heart’s electrical conduction system

• Defibrillators restore normal rhythms to a stuttering heart

Blood maintenace

• Kidney: remove toxins and waste, maintain pH, regulate salt and water levels, maintain blood pressure

Stem Cells and the Replacement of Cellular Elements

• The cellular elements of blood wear out and are being replaced constantly

• Erythrocytes, leukocytes, and platelets all develop from a common source of stem cells in the red marrow of bones, especially ribs, vertebrae, sternum, and pelvis

• The hormone erythropoietin (EPO) stimulates erythrocyte production when O2 delivery is low = blood doping

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AP standard:

• Signal transduction pathways coordinate activities within individual cells that support the function of the organism as a whole.

– EPO hormone: more RBCs when low O2 levels

Signaling examples:

• Fight or flight response– Constriction of arteries: raise blood pressure– Dilation of arteries at muscles: delivers more

blood– Quickened heart beat and respiration– Rise in blood sugar– Suppresses immune system– Divert blood flow from other parts of body to

muscles

AP standard:

• Fish, amphibians, and mammal circulatory systems: support common ancestry

Figure 42.4

(a) Single circulation (b) Double circulation

Artery

Heart:

Atrium (A)

Ventricle (V)

Vein

Gillcapillaries

Bodycapillaries

Key

Oxygen-rich blood

Oxygen-poor blood

Systemic circuit

Systemiccapillaries

Right Left

A A

VV

Lungcapillaries

Pulmonary circuit

Amphibians

Pulmocutaneous circuit

Lungand skincapillaries

Atrium(A)

Atrium(A)

LeftRight

Ventricle (V)

Systemiccapillaries

Systemic circuit

Key

Oxygen-rich bloodOxygen-poor blood

Figure 42.5a

Figure 42.5b

Reptiles (Except Birds)

Pulmonary circuit

Systemic circuit

Systemiccapillaries

Incompleteseptum

Leftsystemicaorta

LeftRight

Rightsystemicaorta

A

V

Lungcapillaries

Atrium(A)

Ventricle(V)

Key

Oxygen-rich bloodOxygen-poor blood

Mammals and Birds

• Mammals and birds have a four-chambered heart with two atria and two ventricles

• The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood

• Mammals and birds are endotherms and require more O2 than ectotherms

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AP Standard: thermoregulation

• Ability of an organism to keep its body temperature within certain boundaries.– Ectotherms/thermoconformers: gain heat from

environment– Endotherms/thermoregulators: use internal

control mechanisms to moderate internal environment (heat: metabolism) = calorie expensive!

Advantages to endothermy:

• Perform vigorous activities (running/flight) longer than ectotherms

• Can withstand more severe environmental fluctuations of terrestrial environment (aquatic habitats tend to be stable – WATER PROPERTY!!)

Thermoregulation: countercurrent exchange mechanism = common ancestry

Other ways to control temps…

• Behavior (radiation, convection and conduction)

• Sweating (vaporization)• Goosebumps: hair/feather raising to gather

air: thermal insulation!• BLUBBER• shivering• Hibernation, estivation

Figure 40.16

Figure 40.14

Figure 40.15