Human Circulation
The Need for Circulation
All living things must
be able to supply
their cells with
materials from the
surrounding
environment (Ex.
Oxygen, nutrients,
enzymes ,etc.)
Special Circulatory
Systems
In this case materials are
absorbed across the cell
membrane by diffusion.
For larger organisms,where
some cells may be located
far away from the outside,
a special circulatory system
is required.
These systems may be
open or closed.
Closed and Open Systems
A closed system, is one in which the blood is
always confined in vessels (Ex. Earthworm).
An open system, is one in which the blood is not
always enclosed in vessels, but flows into open
spaces where it bathes the tissues of the body
directly(Ex. Grasshopper).
Assignment: Write a detailed summary of open
and closed circulation in the earthworm and
grasshopper (pages 146-147). Also complete the
coloring sheet-Correlative Circulatory Patterns.
Components Involved
Three components:
1. A fluid to transport
dissolved materials (Blood)
See handout-Components
and Function.
2. A network of tubes (or
body spaces) to carry fluid
(Blood vessels).
A means of pumping the fluid
(Heart).
Blood
Blood is a special type
of connective tissue.
Two components;
Formed Elements
(the blood cells) and
Plasma (fluid).
Blood-Erythrocytes-Red
Blood Cells
Make up 44% of
blood.
Biconcave
no nucleus
contain the respiratory
pigment hemoglobin
(carries oxygen)
life span of 100-120
days
Blood-Erythrocytes-Red
Blood Cells continued
Lost cells are replaced by new
cells produced in the red bone
marrow.
The rate of RBC production is
called hemopoiesis, and is
controlled by the hormone
erythropoietin (released by
the kidneys in response to
decreasing oxygen levels in
the blood).
Blood- White Blood Cells
More like body cells.
Make up 1% of blood.
Have nuclei.
Produced by lymphatic
tissue.
Serve as a “movable
army”-protect the body
from bacteria, viruses
and tumor cells.
Blood - Platelets
Believed to be
fragments of other
blood cells formed in
red bone marrow.
Small, irregular
shapes.
Needed for clotting.
Blood Clots
A whole series of
reactions called the
blood clotting
cascade creates the
clot.
Reduces blood loss.
Clotting process
involves a number of
substances.called the
clotting factors.
Plasma
Liquid portion
Make up 55% of
blood.
Contains water, salts,
proteins, nutrients,
waste products and
hormones.
The Blood Vessels
There are three main types of blood
vessels:
1. Arteries
2. Veins
3. Capillaries
Arteries
Carry blood away
from the heart.
Thick muscular walls.
No valves.
Form arterioles that
join with capillaries in
the capillary network.
Blood pressure higher
than in veins.
Artery Structure
Connective tissue
Smooth muscle
Elastic fibers
Endothelium
Veins
Veins are the vessels that
carry the blood to the heart.
Thin muscular walls.
Valves to prevent back flow.
Venules that join capillaries
in the capillary network.
Blood pressure tends to be
lower than in arteries.
Veins Structure
Connective Tissue
Smooth muscle
Elastic Fibers
Valve
Endothelium
Capillaries
Capillaries connect
arterioles and venules.
The wall of a capillary is
made up of a single layer
of endothelial cells.
Thin walls allow for
nutrients and gases to
diffuse quickly between
the blood and body cells.
Single layer
of endothelium.
Blood Flow in the Heart
Deoxygenated blood from the
body enters the right atrium
and is pumped to the lungs by
the right ventricle.
Oxygenated blood returns to
the left ventricle under high
pressure and is pumped to the
body tissues.
Note the thicker walls in the left
ventricle that serve to handle
the higher pressure.
Blood Flow in the Heart
This animation shows
the flow of blood in
the heart.
The Heart Beat Cycle
(HBC)
The HBC refers to the periods of
contraction and relaxation of the
atria and ventricles in the heart.
Relaxation is known as diastole
and contraction is called systole.
The accompanying blood pressure
changes are called diastolic and
systolic.
See the handout called The
Heart Beat Cycle.
Pulmonary Circulation
Alveoli
Capillary
Network
Gas Exchange
Blood travels through
pulmonary arteries to the
lungs.
Gas exchange occurs at
the capillary level in the
alveoli.
Veins pick up the
oxygenated blood and
bring it back to the left
atrium via the pulmonary
vein.