EXTERNAL ENVIRONMENT Mouth Food CO 2 O2O2 ANIMAL Digestive system Respiratory system Circulatory system Urinary system Heart Interstitial fluid Body cells

EXTERNAL ENVIRONMENT

MouthFood

CO2 O2

ANIMAL

Digestivesystem

Respiratorysystem

Circulatorysystem

Urinarysystem

HeartInterstitialfluid

Bodycells

Intestine

Anus

Unabsorbedmatter (feces)

Metabolic wasteproducts (urine)

Nutrients

Blo

od

respiratory system exchanges gases between the external environment and blood.

digestive system acquires food and eliminates wastes

excretory system eliminates metabolic waste

circulatory system- distributes gases,nutrients, and wastesthroughout the body

- exchanges materialsbetween blood andbody cells through theinterstitial fluid

Every organism must exchange energy and nutrients/wastes with surroundings

Function of CV System

Circulatory systems facilitate exchange with all body tissues

All cells must

– receive nutrients,

– exchange gases, and

– remove wastes.

Diffusion alone is inadequate for large and complex bodies.

In most animals, circulatory systems facilitate these exchanges.

– Assists diffusion by moving materials between

– surfaces of the body and Internal tissues.

© 2012 Pearson Education, Inc.

Simple Gastrovascular Cavity is Found in Cnidarians and Flatworms

Gastrovascular cavity serves both in digestion and distribution of substances throughout body

This is adequate for these organisms as they are only two layers of cells thick - all cells can exchange materials directly with water.


medusapolyp

Cnidarians = jellyfish and hydraNotice only one opening in/out!

Flatworms - We’re so flat because we exchange materials directly with environment.


Gastrovascularcavity

Nerve cords

Bilateral symmetryNervoustissue clusters

Mouth/Anus

Eyecups

Only ONE entrance/exit! YIKES!!

Small organisms have sufficient SA:volume ratio that they do not require a specialized circulatory system.

Diffusion

Mouth

Diffusion

Two cell layersSingle cell

Diffusion

Gastrovascularcavity

Large, more complex organisms require a true circulatory system

Most animals use a true circulatory system that consists of a

– circulatory fluid (blood),

– muscular pump (heart), and

– set of tubes (blood vessels) to carry the fluid.


EXTERNAL ENVIRONMENT

MouthFood

CO2 O2

ANIMAL

Digestivesystem

Respiratorysystem

Circulatorysystem

Urinarysystem

HeartInterstitialfluid

Bodycells

Intestine

Anus

Unabsorbedmatter (feces)

Metabolic wasteproducts (urine)

Nutrients

Blo

od

But large, complex organisms require true CV system to maintain sufficient SA:volume ratio

2 Types of Circulatory Systems

Open circulatory systems are found in arthropods and many molluscs and consist of

– a heart,

– open-ended vessels, and

– blood that directly bathes the cells and functions as the interstitial fluid.


PoresTubularheart

LE 42-3

Hemolymph in sinusessurrounding organs

Heart

Anteriorvessel

Ostia

Tubular heart

An open circulatory system.

Lateralvessel

A closed circulatory system.

Auxiliary hearts Ventral vessels

Dorsal vessel(main heart)

Small branch vesselsin each organ

Interstitialfluid

Heart

Two Types of Circulatory Systems

Closed circulatory systems are found in vertebrates, earthworms, squids, and octopuses and consist of

– a heart and

– vessels that confine blood, keeping it distinct from interstitial fluid.


Three Types of Blood Vessels Found in CV Systems


Artery(O2-rich blood)

Artery(O2-poor blood)

Capillarybeds

Gillcapillaries

Arteriole

Venule

Vein

HeartAtrium

Ventricle

1. Arteries carry blood away from the heart.

2. Veins return blood to the heart.

3. Capillaries convey blood between arteries and veins.

Vertebrate cardiovascular systems reflect evolution

Closed circulatory systems may exhibit:

In single circulation blood moves

– from gill capillaries,

– to systemic (body) capillaries, and

– back to the heart.

– Blood pressure drops significantly as blood flows thru gill capillaries

– Single circuit would never provide enough pressure to push blood thru the lungs and rest of body in a terresterial (land) animal.

– Characteristic of fish.


Figure 23.2A

Gillcapillaries

Bodycapillaries

Heart:

Ventricle

Atrium

LE 42-4

FISHES

Gill capillaries

AMPHIBIANS

Lung and skin capillaries

REPTILES (EXCEPT BIRDS)

Lung capillaries

MAMMALS AND BIRDS

Lung capillaries

Gillcirculation

Heart:Ventricle (V)

Atrium (A)

Artery

VeinSystemic

circulation

Systemic capillaries Systemic capillaries

Systemiccircuit

Pulmocutaneouscircuit

Right Left

AA

V

A

V

A

V

Systemic capillaries

Right Left

Pulmonarycircuit

Rightsystemic aorta

V

A

V

Systemic capillaries

Right Left

Pulmonarycircuit

A

Systemiccircuit

Leftsystemic aorta

Systemic circuits include all body tissues except lungs. Note that circulatory systems are depicted as if the animal is facing you: with the right side of the heart shown at the left and vice-versa.

Double circulation

double circulation consists of a separate

– pulmonary circuit (heart to lungs and back to heart)

– systemic circuit (heart to body tissue and back to heart)

– Found in land animals - amphibians, reptiles, birds, mammals

– Allows for a second ‘push’ of blood returning from lungs to provide enough pressure for blood to travel without organism’s body.


Four Chambered hearts are essential for organism with high metabolic rates (energy demands)

Four-chambered hearts

– are found in crocodilians, birds, and mammals and

– consist of

– two atria and

– two ventricles.

– Birds, mammals and crocodiles are warm-blooded (endotherms) and thus require much greater rates of cellular respiration (thus more O2) to meet energy demands

– Prevents oxygen-rich and oxygen-poor blood from mixing and keeps pulmonary and systemic circuits completely separate

– oxygen-rich and

– oxygen-poor blood.


Blood flow through the human CV circuits

Blood flow through the double circulatory system of humans

– drains from the superior vena cava (from the head and arms) or inferior vena cava (from the lower trunk and legs) into the right atrium,

– moves out to the lungs via the pulmonary artery,

– returns to the left atrium through the pulmonary vein, and

– leaves the heart through the aorta.


Animation: Path of Blood Flow in Mammals

Figure 23.3A

Superiorvena cava

Pulmonary artery

Capillaries ofright lung

Pulmonary vein

Right atrium

Right ventricle

Inferior vena cava

Aorta

Capillaries ofhead, chest andarms

Pulmonary artery

Capillariesof left lung

Pulmonary vein

Left atrium

Left ventricle

Aorta

Capillaries ofabdominal regionand legs8

91

6

4

543 3

272

9

8

10

LE 42-6

Right atrium

Posteriorvena cava

Pulmonaryveins

Anteriorvena cava

Pulmonary artery

Pulmonaryveins

Rightventricle

Aorta

Semilunarvalve

Atrioventricularvalve

Pulmonaryartery

Left atrium

Semilunarvalve

Atrioventricularvalve

Leftventricle

The Cardiac Cycle

The repeated contraction and relaxation of pumping blood is called the cardiac cycle. The cycle consists of two main phases.

1. During diastole, heart relaxes and all chambers fill with blood

2. During systole, heart contracts and blood flows

– from atria into ventricles

– Then from ventricles into arteries


23.4 The heart contracts and relaxes rhythmically

Cardiac output is the amount of blood pumped per minute from the ventricles.

Cardiac output = Heart rate x volume of blood pumped with each contraction

Heart rate = is the number of heart beats per minute.

Heart rate and cardiac output vary with physiological conditions

Athletes have high CO even with low heart rates due to increased blood volume acquired from training


23.5 The SA node sets the tempo of the heartbeat

The SA (sinoatrial) node

– generates electrical signals in atria and

– sets the rate of heart contractions.

– Called the pacemaker of the heart

– SA Node receives nervous signal info from central nervous system and relays these changes in heart rate to rest of heart to coordinate cardiac cycle and heart rate.


1

ECG

Rightatrium

SA node(pacemaker)

Signals from theSA node spreadthrough the atria.

STRUCTURE AND FUNCTION OF BLOOD VESSELS


23.7 The structure of blood vessels fits their functions

Capillaries

– Function:

– only vessels involved in exchange of solutes and fluid between blood and interstitial fluid.

– Structure:

– have thin walls consisting of a single layer of epithelial cells,

– are narrow, about as wide as one red blood cell, and

– Structure allows for increased surface area to facilitate gas and fluid exchange


Capillary Red bloodcell

Capillary

Interstitialfluid

Tissuecell

Diffusion ofmolecules

23.7 The structure of blood vessels fits their functions

Arteries and veins

– are lined by a single layer of epithelial cells and

– connective tissue layer and smooth muscle that allows these vessels to recoil after stretching.

– Arteries:

– Largest in diameter of all vessels

– thickest layer of smooth muscle in their walls

– Allows them to constrict and reduce blood flow

– Deal with higher blood pressure and exhibit increased elasticity

– Veins:

– have one-way valves that restrict backward flow of blood.


Figure 23.7C

Capillary

Epithelium

Epithelium

Smoothmuscle

Epithelium

Smoothmuscle

Basal lamina

Connectivetissue Connective

tissueArtery

Arteriole Venule

Vein

Valve

23.8 Blood pressure and velocity

Blood pressure

– is the force blood exerts on vessel walls,

– depends on:

– cardiac output (volume of blood and heart rate)

– resistance of vessels to expansion

– decreases as blood moves away from the heart.


23.8 Blood pressure and velocity

Blood pressure is

– highest in arteries and

– lowest in veins.

Blood pressure is measured as

– systolic pressure — caused by ventricular contraction,

– diastolic pressure — low pressure between contractions.


Figure 23.8A

Systolic pressure

Diastolic pressure

Relative sizes andnumbers of bloodvessels

Pre

ssu

re(m

m H

g)

Vel

oci

ty(c

m/s

ec)

Ao

rta

Art

erie

s

Art

erio

les

Cap

illa

ries

Ven

ule

s

Vei

ns

Ven

ae c

avae

120100

806040200

50

3020100

40

23.8 Blood pressure and velocity reflect the structure and arrangement of blood vessels

How does blood travel against gravity, up legs?

– Veins are squeezed by pressure from muscle contractions between

– two muscles or

– muscles and bone or skin.

– One-way valves limit blood flow to one direction, toward the heart.


Direction ofblood flowin vein

Valve(open)

Contractingskeletalmuscle

Valve(closed)

Measuring blood pressure can reveal cardiovascular problems

A typical blood pressure for a healthy young adult is about 120/70.

Hypertension is a serious cardiovascular problem in which blood pressure is persistent at or above

– 140 systolic and/or

– 90 diastolic.


23.10 Smooth muscle controls the distribution of blood

Blood flow through capillaries is restricted by precapillary sphincters.

By opening and closing these precapillary sphincters, blood flow to particular regions can be increased or decreased.

Only about 5–10% of capillaries are open at one time.


Figure 23.10

2

1

Sphincters are contracted.

Sphincters are relaxed.

Precapillarysphincters

Thoroughfarechannel

ArterioleCapillaries

Venule

VenuleArteriole

Thoroughfarechannel

23.11 Exchange of materials between blood and interstitial fluid occurs at capillaries

Substances leave blood and enter interstitial fluid by

– diffusion (following concentration gradient) and

– pressure-driven flow through clefts between epithelial cells.

Blood pressure forces fluid (water) out of capillaries at the arterial end.

Osmotic pressure draws in fluid (water) at the venous end.


LE 42-14

Capillary Red bloodcell

15 µm

Tissue cell

CapillaryNet fluidmovement out

INTERSTITIAL FLUID

Net fluidmovement in

Blood pressureOsmotic pressure

Inward flow

Direction ofblood flow

Pre

ssu

re

Outward flow

Venous endArterial end of capillary

Glucose, O2, and other nutrients have greatest concentration in blood at arterial end so they move out by diffusion

CO2 and other wastes have greatest concentration in interstitial fluid at venous end so they move in by diffusion

Water moves by net effect of blood versus osmotic pressure

STRUCTURE AND FUNCTION

OF BLOOD


23.12 Blood consists of red and white blood cells suspended in plasma

Plasma (55%)

Cellular elements (45%)Constituent Major functions

Water Solvent forcarrying othersubstances

Ions (blood electrolytes)

SodiumPotassiumCalciumMagnesiumChlorideBicarbonate

Osmotic balance,pH buffering, andmaintaining ionconcentration ofinterstitial fluid

Plasma proteins

Fibrinogen

Immunoglobulins(antibodies)

Osmotic balanceand pH buffering

Clotting

Defense

Substances transported by blood

Nutrients (e.g., glucose, fatty acids, vitamins)Waste products of metabolismRespiratory gases (O2 and CO2)Hormones

Centrifugedblood

sample

Cell type Numberper L (mm3) of blood)

Functions

Transport of O2 and some CO2

5–6 million

Red blood cells(erythrocytes)

White blood cells(leukocytes)

5,000–10,000 Defenseand immunity

Platelets250,000–400,000

Blood clotting

BasophilsEosinophils

Lymphocytes

Neutrophils Monocytes

Figure 23.13

New Blood Cells are generated in bone marrow from stem cells

Multipotent stem cells

– are unspecialized and

– replace themselves throughout the life of an organism.

Multipotent stem cells can differentiate into two main types of stem cells.

1. Lymphoid stem cells can in turn produce two types of lymphocytes (T- and B-cells), which function in the immune system.

2. Myeloid stem cells can differentiate into– erythrocytes,

– other white blood cells, and

– platelets.© 2012 Pearson Education, Inc.

Figure 23.15

Lymphocytes Monocytes Neutrophils

Eosinophils

Basophils

Myeloidstem cells

Platelets

Erythrocytes

Lymphoidstem cells

Multipotentstem cells(in bone marrow)

Figure 50.17 Control of Blood Pressure through Local and Systemic Mechanisms

Figure 50.18 Regulating Cardiac Output

Documents

EXTERNAL ENVIRONMENT Mouth Food CO 2 O2O2 ANIMAL Digestive system Respiratory system Circulatory system Urinary system Heart Interstitial fluid Body cells