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Transcript
The Human Circulatory System
Introduction

Humans and other vertebrates have a closed
circulatory system:
–
This means that circulating blood is pumped
through a system of vessels
–
This system consists of the heart (pump), series
of blood vessels and the blood that flows through
them.
The Truth
About Your
Heart
The Heart

Located near the center of
your chest

Hollow structure

Composed almost entirely of
muscle

About the size of your
clenched fist
The Heart

Enclosed in a protective
sac called the
pericardium
The Heart

In the walls of the heart, two layers of tissue
form a sandwich around a thick layer of
muscle called the myocardium.

Contractions of the myocardium pump blood
through the circulatory system.
The Heart

The heart contracts about 72 times per
minute

Pumps about 70mL of blood with each
contraction.
The Heart

The right and left sides of
the heart are separated
by a septum, or wall.

The septum prevents the
mixing of oxygen rich and
oxygen poor blood.
The Heart

On each side of the septum
are two chambers.

The upper chamber
(receives blood) is the
atrium.

The lower chamber (pumps
blood out of heart) is the
ventricle.
The Heart

The heart has a total of
4 chambers:

2 atriums
2 ventricles

Pathway of Blood

Deoxygenated blood passes
from the right atrium into the
right ventricle and then goes
to the lungs.

From the lungs, blood
moves back toward the
heart into the left atrium to
the left ventricle and then
passes into the aorta to go
to the rest of the body
Valves

As the heart contracts, blood flows into the ventricles
and then out through the ventricles.

Flaps of connective tissue, called valves, are located
between the atria and ventricles.

Blood moving keeps the valves open.

When the ventricles contract, the valves close which
prevent blood from flowing back into the atria.
Valves


There are also valves that stop blood from
re-entering the ventricles after the blood has
left.
This system of valves keeps blood moving in
one direction which increases the pumping
efficiency of the heart.
Heart Beat

Heart muscles are
composed of individual
fibers

Each atrium and ventricle
contracts as a unit.

Each contraction begins with
a group of cardiac muscle
cells in the right atrium
known as the sinoatrial node
(SA node)
Heart Beat

Because the SA node paces the heart it is known as
the pacemaker.

The impulse spreads from the pacemaker to the rest
of the atria.

From the atria, a signal is sent to the atrioventricular
node and then to a bundle of fibers in the ventricle.

When the ventricle contracts, blood flows out.
Blood Vessels

As blood moves
through the circulatory
system it moves
through 3 types of
blood vessels:

Arteries
Capillaries
Veins


Arteries

Large vessels

Carry blood from heart to tissues of body

Carry oxygen rich blood, with the exception of
pulmonary arteries.

Thick walls-need to withstand pressure produced
when heart pushes blood into them.
Capillaries

Smallest blood vessels

Walls are only one cell thick and very narrow.

Important for bringing nutrients and oxygen
to tissues and absorbing CO2 and other
waste products.
Veins

Once blood has passed through the capillary systems it must
be returned to the heart.

Done by veins

Walls contains connective tissue and smooth muscle.

Largest veins contain one way valves that keep blood flowing
toward heart.

Many found near skeletal muscles. When muscles contract,
blood is forced through veins.
Blood Pressure

The heart produces pressure

The force of blood on the wall of the arteries
is known as blood pressure.

Blood pressure decreases as the heart
relaxes, but the rest of the circulatory system
is still under pressure.
Blood Pressure

When blood pressure is taken, the cuff is wrapped
around the upper portion of the arm and pumped
with air until blood flow in the artery is blocked.

As the pressure in the cuff is relaxed, 2 numbers are
recorded.
–
Systolic pressure- the first number taken, is the force felt in
the arteries when the ventricles contract.
–
Diastolic pressure- the second number taken, is the force of
the blood on the arteries when the ventricles relax.
Disorders of Circulatory System

Atherosclerosis
–
Fatty deposits (plaque) in walls of arteries
–
Deposits can obstruct flow of blood which can raise blood
pressure
–
Increases risk of blood clots
–
If clot breaks free it can obstruct blood flow to tissues.
Disorders of Circulatory System

Heart Attack
–
Due to atherosclerosis, coronary arteries may
become blocked (blood can’t get to heart muscle)
–
Heart muscle begins to die due to lack of O2
Disorders of Circulatory System

Stroke
–
Blood clot may break free and block a vessel leading to the
brain.
–
Brain cells are starved of oxygen and nutrients
–
Loss of function may occur
–
Can cause paralysis, loss of ability to speak or death.
Blood


Composed of plasma and blood cells
Types of Cells are:
–
–
–
Red Blood Cells
White Blood Cells
Platelets
Blood

Plasma
–
Straw colored
–
90% water
–
10% dissolved gases, salts, nutrients, enzymes,
hormones, wastes, and proteins.
Blood

Plasma proteins
–
3 Types: Albumins, globulins and fibrinogen.
–
Albumins and Globulins- transport substances
such as fatty acids, hormones and vitamins.
–
Fibrinogen- Responsible for blood’s ability to clot
Blood

Red Blood Cells
–
–
–
–
–
–
Most numerous type
Transport oxygen
Get color from
hemoglobin
Disk shaped
Made in red bone
marrow
Circulate for 120 days
Blood

White Blood Cells
–
Guard against infection,
fight parasites, and attack
bacteria
–
Number of WBC’s
increases when body is
fighting
–
Lymphocytes produce
antibodies which fight
pathogens and remember
them
Blood

Platelets
–
Aid the body in clotting
–
Small fragments
–
Stick to edges of broken blood cell and secrete
clotting factor to help form clot.
Blood Clotting Problems

Hemophelia
–
Genetic disorder that disrupts clotting
–
People must be very careful to avoid injury
–
Can be treated by injecting extracts that contain
the missing clotting factor.