HONORS BIOLOGY
Chapter 23
Circulation
MECHANISMS OF INTERNAL TRANSPORT
23.1 Circulatory systems facilitate exchange with all body
tissues
All cells need

Nutrients

Gas exchange

Removal of wastes
Diffusion alone is inadequate for large and complex bodies

An internal transport system assists diffusion by
moving materials between

Surfaces of the body

Internal tissues
A gastrovascular cavity in cnidarians and flatworms serves

Digestion

Distribution of substances
Most animals use a circulatory system

Blood

Heart

Blood vessels
Open circulatory systems

Arthropods and many molluscs

Heart pumps blood through open-ended vessels

Cells directly bathed in blood
Closed circulatory systems

Vertebrates, earthworms, squids, octopuses

Blood stays confined to vessels

A heart pumps blood through arteries to capillaries

Veins return blood to heart
23.2 EVOLUTION CONNECTION: Vertebrate
Cardiovascular systems reflect evolution
Two-chambered heart

Fish

Pumps blood in a single circuit

From gill capillaries

To systemic capillaries

Back to heart
Land vertebrates have double circulation

Separate pulmonary and systemic
circuits
Three-chambered hearts

Amphibians, turtles, snakes, lizards

Two atria

One undivided ventricle

Permits blood diversion away from lungs when diving

But some blood from body and lungs mixes in the
ventricle when not diving
Four-chambered hearts

Crocodilians, birds, mammals

Two atria and two ventricles

Two circuits that do not mix

Right side pumps blood from body to lungs

Left side pumps blood from lungs to body

Higher blood pressure

Supports more efficient movement of blood

Needed in endothermic animals
Mrs. Loyd
Page 1 of 2
7/12/2016
THE HUMAN CARDIOVASCULAR
SYSTEM
23.3 The human cardiovascular system illustrates the
double circulation of mammals
Blood flow through the double circulatory system of humans
The mammalian heart

Two thin-walled atria that

Pump blood

To ventricles

Thick-walled ventricles that

Pump blood

To lungs and all other body regions
23.6 CONNECTION: What is a heart attack?
A heart attack is damage to cardiac muscle
Typically from a blocked coronary artery
Stroke
Death of brain tissue from blocked arteries in the head
Atherosclerosis
Plaques develop inside inner walls of blood vessels

Plaques narrow blood vessels

Blood flow is reduced
23.7 The structure of blood vessels fits their functions
Capillaries

Thin walls—a single layer of epithelial cells

Narrow—blood cells flow in a single file

Increase surface area for gas and fluid exchange
Arteries and veins

Lined by single layer of epithelial cells

Smooth muscle in walls can reduce blood flow

Elastic fibers permit recoil after stretching

Veins have one-way valves that restrict backward flow
23.13 CONNECTION: Too few or too many red blood cells
can be unhealthy
Anemia: Abnormally low amounts of hemoglobin or red blood
cells

Causes fatigue due to lack of oxygen in tissues
Hormone erythropoietin (EPO)

Regulates red blood cell production
Some athletes artificially increase red blood cell production
By:

exercising at high elevations
o increases RBC count
o sea level exercise is then easier due to
increased # RBC’s

injecting erythropoietin
o “Blood Doping”

Can lead to
o Clotting
o Stroke
o Heart failure
o Death
Connecting the Concepts p. 482, #1 see diagram 
(Answers on p. 470, fig. 23.3A)
Mrs. Loyd
Page 2 of 2
7/12/2016