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CH 23- Circulation/Valves/Heart

Every organism must exchange materials with its
environment.
 The purpose of the circulatory system is to facilitate this
exchange.

All but the simplest animals have circulatory systems
with three main components:
 A central pump
 A vascular system
 The circulating fluid

Open circulatory system
 The heart pumps blood into large open-ended vessels.
 Fluid circulates freely among cells.
 Many invertebrates, such as molluscs and arthropods have
open circulatory systems.

Closed circulatory system
 Blood is confined to vessels and is distinct from the
interstitial fluid.
 Earthworms, octopuses, and vertebrates have closed
circulatory systems.

The closed circulatory system
in vertebrates is called a
cardiovascular system.
 This system includes the heart
and blood vessels.

In the human cardiovascular system,
 The central pump is the heart.
 The vascular system is the blood vessels.
 The circulating fluid is the blood.

In humans and other vertebrates, the three components
of the cardiovascular system are organized into a
double circulation system.
 There are two distinct circuits of blood flow.

The pulmonary circuit carries blood between the heart
and the lungs.

In the human cardiovascular system,
 The central pump is the heart.
 The vascular system is the blood vessels.
 The circulating fluid is the blood.

In humans and other vertebrates, the three components
of the cardiovascular system are organized into a
double circulation system.
 There are two distinct circuits of blood flow.

The pulmonary circuit carries blood between the heart
and the lungs.

The systemic circuit carries blood between the heart
and the rest of the body.
Figure 23.4

The human heart is a muscular organ about the size of
a fist.
 It is located under the breastbone.
 It has four chambers.
http://www.youtube.com/watch?v=H04d3rJCLCE
Figure 23.5

The heart relaxes and contracts regularly:
 Diastole is the relaxation phase of the heart cycle.
 Systole is the contraction phase.
http://www.youtube.com/watch?v=4jRy-YlZONA
http://www.youtube.com/watch?v=PgI80Ue-AMo
Figure 23.6


The pacemaker, or SA (sinoatrial) node, sets the tempo
of the heartbeat.
The pacemaker is composed of specialized muscle
tissue in the wall of the right atrium.

The impulses sent by the pacemaker produce electrical
currents that can be detected by electrodes placed on
the skin.
 These are recorded in an electrocardiogram (ECG or EKG).

In certain kinds of heart disease, the heart’s electrical
control fails to maintain a normal rhythm.
 The remedy is an artificial pacemaker.

If the heart is the body’s “pump,” then the “plumbing”
is the system of arteries, veins, and capillaries.
 Arteries carry blood away from the heart.
 Veins carry blood toward the heart.
 Capillaries allow for exchange between the bloodstream
and tissue cells.
Figure 23.8

The force that blood exerts against the walls of your
blood vessels is called blood pressure.
 Blood pressure is the main force driving the blood from
the heart to the capillary beds.
 A pulse is the rhythmic stretching of the arteries caused by
the pressure of blood forced into the arteries during
systole.


Optimal blood pressure for adults is below 120 systolic
and below 80 diastolic.
High blood pressure is persistent systolic blood
pressure higher than 140 and/or diastolic blood
pressure higher than 90.
 It is also called hypertension.

At any given time, about 5–10% of your capillaries have
a steady flow of blood running through them.
Figure 23.9a

The walls of capillaries are thin and leaky.
 As blood enters a capillary at the arterial end, blood
pressure pushes fluid rich in oxygen, nutrients, and other
substances into the interstitial fluid.
 At the venous end of the capillary, CO2 and other wastes
diffuse from tissue cells and into the capillary
bloodstream.
Continuous flow
 Volume of fluid that flows past any crosssection of a pipe in a given time is the same as
that flowing past any other section of the pipe
even if the pipe widens or narrows.
 Fluid speeds up when it flows from a wide to
narrow pipe
 Motion of fluid follows imaginary streamlines


A1V1 = A2V2
http://www.aplusphysics.com/courses/honor
s/fluids/continuity.html
Figure 23.9b

After chemicals are exchanged between the blood and
body cells, blood returns to the heart via the veins.
 By the time blood exits the capillaries and enters the veins,
the pressure originating from the heart has dropped to
near zero.
 Blood still moves through the veins against the force
of gravity.
 As skeletal muscles contract, they help squeeze the
blood along.
Veins not arteries,
have one-way valves

The circulatory system of an adult human has about 5 L
(11 pints) of blood.
 Just over half of this volume is plasma.
 Suspended within the plasma are several types of cellular
elements.
Figure 23.11

Red blood cells are by far the most numerous type of
blood cell.
 They are also called erythrocytes.
 Carbohydrate-containing molecules on the surface
determine the blood type.
Figure 23.12a

Each red blood cell contains large amounts of the
protein hemoglobin.
 Hemoglobin contains iron and transports oxygen
throughout the body.
 Anemia is an abnormally low amount of hemoglobin or a
low amount of red blood cells.

White blood cells fight infections and cancer.
 They are also called leukocytes.
 There are about 700 times fewer white blood cells than red
blood cells.
Figure 23.12b

Blood contains two components that aid in clotting:
 Platelets (thrombocytes) are bits of cytoplasm pinched off
from larger cells in the bone marrow.
 Fibrinogen is a membrane-wrapped protein found in
plasma.

Platelets release molecules that convert fibrinogen into
fibrin.
 Fibrin is a threadlike protein.
 Fibrin forms a dense network to create a patch.
Figure 23.12c

New blood cells are continually formed from
unspecialized stem cells found in red bone marrow.
 Stem cells differentiate into red and white blood cells and
the cells that produce platelets.
 Bone marrow cells show great promise for the treatment of
disease.

Leukemia is cancer of the white blood cells.
 A person with leukemia has an abnormally high number
of white blood cells, most of which are defective.
 Leukemia is usually fatal unless treated.
 Not all cases respond to treatment.

The cardiovascular system performs several
homeostatic functions:
 Controlling chemical balance
 Controlling the composition of the blood
 Regulating body temperature
 Distributing hormones
 Defending against foreign invaders
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Cardiovascular disease accounts for 40% of all deaths in
the United States.
 The leading cause of death in the United States is heart
attack.

When blood exits the heart, several coronary arteries
immediately branch off to supply the heart muscle.
 If one or more of these arteries is blocked, the heart muscle
cells will quickly die.
 This is called a heart attack.
Figure 23.13

Atherosclerosis is a chronic cardiovascular disease.
 The blood vessels become impaired gradually.
 Vessels are narrowed by plaques of cholesterol and other
substances that form in the inner walls of arteries.
Figure 23.14

How can you avoid becoming a heart disease victim?
 Don’t smoke.
 Exercise.
 Eat a heart-healthy diet.

Recall that cellular respiration uses oxygen and glucose
to produce water, carbon dioxide, and energy in the
form of ATP.
 Cells need a constant supply of oxygen and must
continuously dispose of CO2.
 The respiratory system facilitates this gas exchange.
Figure 23.UN1