Transcript Essentials of Biology Sylvia S. Mader

Essentials of Biology
Sylvia S. Mader
Chapter 23
Lecture Outline
Prepared by: Dr. Stephen Ebbs
Southern Illinois University Carbondale
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
23.1 Open and Closed
Circulatory Systems
• For some simple organisms, a circulatory
system is not necessary.
• Hydra and planarians are so small, for example,
that diffusion provides for the movement of
fluids, gases, and wastes.
• For nematodes and echinoderms, movement of
the organism provides for the movement of the
internal fluids.
23.1 Open and Closed
Circulatory Systems (cont.)
Open Circulatory Systems
• More complex organisms have a circulatory
system.
• A circulatory system involves a heart that pumps
fluid through the organism.
• In an open circulatory system, a tubular heart
pumps hemolymph through channels and
cavities throughout the body.
• The hemolymph is returned to the heart by
passive flow.
Open Circulatory Systems
(cont.)
Closed Circulatory Systems
• A closed circulatory system, or cardiovascular
system, includes a strong heart and blood
vessels.
• The heart pumps the blood to the body and
receives the blood returned to the heart.
• There are three types of blood vessels.
– Arteries
– Veins
– Capillaries
Closed Circulatory Systems
(cont.)
• Arteries carry blood away from the heart.
• Veins return blood to the heart.
• The capillaries are a fine network of
vessels between the arteries and
capillaries where fluid, gas, and waste
exchange take place.
Closed Circulatory Systems
(cont.)
Comparison of Circulatory
Pathways
• There are two
different types of
circulatory pathways
in vertebrate animals.
• In fish, the circulatory
pathway is a single
loop with a twochambered heart.
Comparison of Circulatory
Pathways (cont.)
• All other vertebrates have a double
circulatory system.
– The systemic circuit includes the blood
vessels that carry blood to the body.
– The pulmonary circuit includes the blood
vessels that send blood to the lungs.
• The double circulatory system helps
terrestrial organisms breathe air.
Comparison of Circulatory
Pathways (cont.)
• The amphibian and
reptilian heart has three
chambers.
• In amphibians, there are
two atria and a single
ventricle.
• In reptiles, the ventricle
has a partial dividing wall
(septa).
Comparison of Circulatory
Pathways (cont.)
• The hearts of birds
and mammals have
four chambers.
• The right side pumps
to the pulmonary
circuit.
• The left side pumps to
the systemic circuit.
23.2 Transport in Humans
• The mammalian cardiovascular system
pumps blood through the arteries to the
capillaries.
• After gases, nutrients, and wastes are
exchanged in the capillaries, the blood
returns to the heart in the veins.
The Human Heart
• The mammalian heart is a double pump.
– The right side pumps oxygen-depleted blood to the
lungs.
– The left side pumps oxygen-rich blood to the body.
• The two sides of the heart are separated by a
wall of tissue called the septum.
• This septum prevents the oxygen-depleted and
oxygen-rich blood from mixing.
The Human Heart (cont.)
• Each side of the heart has two chambers.
– An upper atrium that receives blood
– A lower ventricle that pumps blood out
• There are valves that regulate the flow of blood
through the heart.
– The atria and ventricles are connected by the
atrioventricular valves.
– The semilunar valves connect the ventricles to the
attached blood vessels.
The Human Heart (cont.)
• The right atria receives the blood returned to the
heart via the vena cava.
• The blood passes to the ventricle through the
tricuspid valve.
• The right ventricle pumps blood to the lungs
through the pulmonary semilunar valve, the
pulmonary trunk, and pulmonary arteries.
The Human Heart (cont.)
• After gas exchange in the lungs, the pulmonary
veins bring oxygen-rich blood back to the left
atria of the heart.
• The blood passes through the bicuspid valve to
the left ventricle.
• The left ventricle pumps the blood through the
aortic semilunar valve to the aorta.
• The aorta distributes the blood to the body.
The Human Heart (cont.)
The Human Heart (cont.)
• When one of the heart valves is defective,
the flow of blood is disrupted and backflow
occurs.
• The backflow creates an audible sound
called a heart murmur.
The Heartbeat
• The pumping of the heart consists of a series of
events called the cardiac cycle.
• The contraction of the heart during the heartbeat
is called systole.
• The relaxation of the heart during the heartbeat
is called diastole.
• The sound of the heartbeat is caused by the
closing of the heart valves.
The Heartbeat (cont.)
• The pulse is the wave effect that passes along
the arterial walls as the heart pumps blood
through the aorta to the body.
• The heartbeat is regulated by the sinoatrial (SA)
node, special cardiac muscle in the atrial wall.
• The SA node sends a regular signal that triggers
the atria to contract.
The Heartbeat (cont.)
• When the atrioventricular (AV) node
receives the SA signal, the AV nodes
causes the ventricle to contract.
• If there are defects in the SA node, an
artificial pacemaker may be required to
adequately regulate the heartbeat.
The Heartbeat (cont.)
The Heartbeat (cont.)
• The electrical signals generated by the SA
and AV nodes can be monitored with an
electrocardiogram (ECG).
The Heartbeat (cont.)
• An ECG reveals the normal pattern of electrical
activity as the heart beats.
The Heartbeat (cont.)
• Irregularities in the ECG can be used to
diagnose specific problems with the heart.
Blood Vessels
• Arteries carry blood away from the heart.
• The blood pressure is a measure of the
pressure of arterial blood flow.
• The structure of arteries includes muscle
tissue that allows them to expand as the
blood pressure changes.
Blood Vessels (cont.)
• This flexible arterial
structure includes
smooth muscle and
elastic fibers.
• The arterioles are
small arteries that
help regulate blood
pressure.
Blood Vessels (cont.)
• Arteries branch into
microscopic vessels
called capillaries.
• The capillaries have
only a thin layer of
epithelial cells to
facilitate exchange of
substances with the
tissues.
Blood Vessels (cont.)
• Venules are vessels
that drain blood from
the capillaries into
veins.
• Veins have a larger
diameter than
arteries, but have
thinner walls and
move blood under a
lower pressure.
Blood Vessels (cont.)
• The flow of blood
through veins is
driven by the
contraction of skeletal
muscle.
• The veins also have
valves which prevent
backflow of blood.
The Pulmonary and Systemic
Circuits
• The human cardiovascular system is a
double circuit.
• The pulmonary circuit circulates blood to
the lungs for gas exchange.
– The pulmonary arteries carry blood from the
right side of the heart to the lungs.
– The pulmonary veins returned oxygenated
blood to the left side of the heart.
The Pulmonary and Systemic
Circuits (cont.)
• The systemic circuit distributes the oxygenated
blood to the body.
• Oxygenated blood from the left side of the heart
is distributed to the body through the aorta.
• After passing through the arteries, capillaries
and veins, the vena cava returns the blood to the
right side of the heart.
The Pulmonary and Systemic
Circuits (cont.)
The Pulmonary and Systemic
Circuits (cont.)
• A portal system is
another group of
blood vessels that
begin and end at a
capillary bed.
Lymphatic System
• The lymphatic system has several functions in
the human body.
– This system returns excess fluid (lymph) from the
tissues to the heart.
– Fat is taken up from the digestive tract.
– The lymphatic system works with the immune system.
• The lymphatic vessels are an extensive network
of ducts and vessels throughout the body.
Lymphatic System (cont.)
Cardiovascular Disorders
• High blood pressure is a cardiovascular
disorder called hypertension.
• Several factors contribute to hypertension.
– Genetic factors
– Lifestyle
– Presence of atherosclerosis plaques.
Cardiovascular Disorders (cont.)
• A stationary plaque is
called a thrombus.
• A dislodged plaque in the
bloodstream is an
embolus.
• A stroke occurs when an
embolus blocks an
arteriole or an arteriole
bursts.
Cardiovascular Disorders (cont.)
• The coronary arteries are vessels that
provide oxygenated blood to the heart
muscle.
• Like any muscle, the heart requires
oxygen to survive.
• Blockage of these arteries deprives the
heart of oxygen and causes a heart attack
Cardiovascular Disorders (cont.)
• A coronary bypass
operation inserts a graft
to bypass blocked
coronary arteries.
• In balloon angioplasty, a
stent is often used to
keep the artery open.
23.3 Blood: A Transport Medium
• The blood serves several functions.
– Blood serves as a transport medium to
capillaries for fluid and solute exchange.
– The blood distributes components of the
immune system.
– The blood helps regulate body temperature.
– The blood can form clots to prevent excessive
blood losses from wounds.
23.3 Blood: A Transport Medium
(cont.)
• Human blood has two
main components.
– The liquid plasma
– The formed elements,
such as the cells and
platelets.
Plasma
• Plasma consists of two main components.
– Water (>90%)
– Protein (<10%)
• The plasma also contains nutrients,
wastes, and salts.
• The salts help buffer the blood pH and
maintain the osmotic potential of the
blood.
Formed Elements
• There are three types of formed elements.
– Red blood cells
– White blood cells
– Platelets
• The red blood cells are small cells that
contain hemoglobin for oxygen transport.
• A decrease in the number of red blood
cells in the body can lead to anemia.
Formed Elements (cont.)
• Red blood cells are produced by the marrow of
the skull, ribs, vertebrae, and long bones.
• The kidneys secrete erythropoietin, which
stimulates red blood cell production.
• As red blood cells are released from the bones,
they become specialized for oxygen transport.
• Red blood cells are eventually recycled to
produce new red blood cells.
Formed Elements (cont.)
Formed Elements (cont.)
• The white blood cells that fight infection
are also called leukocytes.
• White blood cells are found not only in the
blood but in the lymphatic system.
• The life span of white blood cells varies
from a few days to years.
Formed Elements (cont.)
• The body’s response to an infection begins with
an inflammatory response.
– The injured site swells and reddens.
– The damaged tissues release kinins to increase blood
flow through the capillaries.
– The damaged tissues release histamines to increase
capillary permeability
• White blood cells called neutrophils pass
through the capillary walls and phagocytize
foreign material.
Formed Elements (cont.)
• White blood cells called monocytes are
transformed into macrophages, another
type of phagocytizing cells.
• Macrophages also release growth factors
that increase the number of white blood
cells called lymphocytes.
• Lymphocytes called T cells specialize in
the destruction of virus-infected cells.
Formed Elements (cont.)
• Lymphocytes called B cells produce antibodies.
• The unique antibody produced by each B cell is
unique to a particular foreign protein or
polysaccharide, called an antigen.
• When an antibody combines with an antigen, the
complex is phagocytized by a macrophage.
Formed Elements (cont.)
Platelets and Blood Clotting
• Platelets, or thrombocytes, are fragments
of bone marrow cells called
megakaryocytes.
• The platelets are critical to blood clotting,
also called coagulation.
• Also important to blood clotting are 12
chemicals called clotting factors.
Platelets and Blood Clotting
(cont.)
• Hemophilia, a blood clotting disorder, is
due to the absence of one clotting factor.
• The liver produces two clotting factors.
– Prothrombin
– Fibrinogen
Platelets and Blood Clotting
(cont.)
• The formation of a clot begins when
platelets clump at the site of a puncture.
• The platelets and injured tissues release
prothrombin activator, which converts
prothrombin to thrombin.
• Thrombin is an enzyme that modifies
fibrinogen to become fibrin.
Platelets and Blood Clotting
(cont.)
• The fibrin threads wind around the
clumped platelets to form the framework of
the clot.
• During clot retraction, the clot gets smaller
as the cells shrink and are replaced by a
fluid called serum.
• When the blood vessel is repaired, the
enzyme plasmin destroys the fibrin.
Platelets and Blood Clotting
(cont.)
Platelets and Blood Clotting
(cont.)
Platelets and Blood Clotting
(cont.)
Capillary Exchange in the Tissues
• Two forces control the movement of fluid
through the capillary wall.
– The osmotic pressure drives tissue fluid into
the blood.
– The blood pressure drives fluid from blood
into the tissues.
Capillary Exchange in the Tissues
(cont.)
Capillary Exchange in the Tissues
(cont.)