Download circulatory system

THE CIRCULATORY
SYSTEM
Agriscience 332
Animal Science
#8646-A
TEKS: (c)(2)(A)
Introduction
The circulatory system is
comprised of the heart, veins,
capillaries, arteries, lymph vessels,
and lymph glands, which work
together to supply the body
tissues with nourishment and
collect waste materials.
Functions of the circulatory system:
Distribute nutrients,
Transport and exchange oxygen
and carbon dioxide,
Remove waste materials,
Distribute secretions of endocrine
glands,
Prevent excessive bleeding,
Prevent infection, and
Regulate body temperature.
Anatomy and Physiology
of the Heart
The heart is a funnel-shaped,
hollow, muscular organ that is
responsible for pumping blood
to all parts of the body.
The heart is located near the
center of the thoracic cavity
between the lungs and is
contained in the pericardial sac.
The pericardial sac supports the
heart and contains some fluid
for lubrication.
The broad end, or base, of the
heart is also supported by large
arteries and veins.
The pointed end, or apex, of the
heart is directed toward the
abdomen.
The heart wall is made up of three
layers:
• Epicardium – outer layer of heart
wall, which is also the inner layer
of epicardial sac;
• Endocardium – inner layer that
consists of endothelial cells, which
line the heart, cover the heart
valves, and line the blood vessels:
• Myocardium – middle layer
composed of cardiac muscle.
The cardiac muscle is an
involuntary, striated muscle
with fibers that intertwine.
In mammals and birds, the heart
is divided into a right and left side
and each side is divided into an
atrium and ventricle.
Therefore, the heart is said to
have four chambers (right atrium,
right ventricle, left atrium, and left
ventricle).
The atrioventricular valves
(AV valve) separate the atrium and
ventricle on each side of the heart.
The AV valves have flaps of tissues,
called leaflets or cusps, which open
and close to ensure that the blood
flows only in one direction and does
not backflow into the atriums.
The AV valve on the right side of the
heart is called the tricuspid valve
because it has three leaflets (cusps).
The AV valve on the left side of the
heart is called the bicuspid valve
(or mitral valve) because it has two
leaflets.
The pulmonary valve and the
aortic valve prevent blood from
back-flowing into their respective
ventricles.
The pulmonary valve is located
between the right ventricle and the
pulmonary artery.
The aortic valve is located
between the left ventricle and the
aortic artery.
Following the path that the blood
takes as it flows through the heart
and lungs is the best way to
understand the heart’s operation.
(This process will be discussed later in
the topic of pulmonary circulation.)
A group of cells called the sinoatrial
node (SA node) control the beat of
the heart by sending out electrical
signals to make the heart pump.
Anatomy and Physiology
of the Vascular System
The vascular system is made up
of three types of blood vessels:
• Arteries,
• Capillaries, and
• Veins.
Blood Vessels
Photo from U. S. Federal Government courtesy of Wikipedia.
Arteries are blood vessels that
carry blood, rich in oxygen, from the
heart to other parts of the body.
The large arteries have thick walls of
elastic-like tissue that enables them
to withstand the blood pressure
created by the heart’s beating.
As the arteries extend away from
the heart, they branch out into
smaller arteries called arterioles.
The smaller arteries’ walls are
composed of large amounts of
smooth muscle instead of the
elastic tissue.
Arterioles branch into smaller
vessels called capillaries.
At this junction, the arterioles have
an especially thick layer of smooth
muscle in their walls that carefully
controls the amount of blood each
capillary receives.
Blood pressure for the entire
circulatory system is maintained by the
tension at the end of the arterioles.
Shock is a serious condition that
occurs when the arterioles dilate
(relax) and allow a large volume of
blood into the capillary beds.
The reduced blood flow that occurs
with shock jeopardizes vital organs.
Capillaries are tiny, thin-walled
blood vessels that connect arteries
to veins and are located in all body
tissues.
Capillaries are so small in diameter
that blood cells pass through in a
single file.
The semi-permeable membrane of
capillary walls allows nutrients,
oxygen, and water to diffuse
from the blood to the tissues.
Waste products, like carbon
dioxide, diffuse from the tissues
into the blood.
Capillary Bed
Interaction of molecules flowing in and out of blood at a capillary bed.
Larger tubular connectors, which
also connect arterioles to venules,
are located within the capillary beds.
These tubules allow more blood to
flow through an area, help warm
tissues, and increase the return of
blood pressure to the heart.
Once blood passes through the
capillary beds, it begins its return
to the heart.
Veins are the blood vessels that
return blood to the heart from all
parts of the body.
Capillaries unite to form small
veins called venules.
The venules join together to form
larger veins, which have thin walls
and are collapsible.
For each artery, there is a much
larger vein counterpart.
Veins have valves that aid the
return flow of blood and prevent
the blood from reversing flow.
These valves allow for muscle
contractions and movement of
body parts.
The valves also assist the return
flow of blood to the heart when
blood pressure is low.
Parts of the
Circulatory System
The total circulatory system is
divided into two main parts:
• Pulmonary circulation, and
• Systemic circulation.
Pulmonary Circulation System
Red portion of heart and red blood vessels carry oxygen-rich blood.
Blue portion of heart and blue blood vessels carry oxygen-poor blood.
Pulmonary circulation is the part
of the circulatory system that takes
the blood from the heart to the
lungs, where it is oxygenated, and
returns it to the heart.
The main parts of the pulmonary
circulation system include the heart,
pulmonary arteries, capillaries of the
lungs, and pulmonary veins.
Flow of Blood in Pulmonary Circulation
Blood that is low in oxygen returns to
the heart through two large veins
called the superior (or cranial) vena
cava and the inferior (or caudal)
vena cava.
The un-oxygenated blood enters the
right atrium of the heart.
The blood then passes through the
right atrioventricular (tricuspid)
valve into the right ventricle.
The right ventricle pumps the
blood through the pulmonary
valve into the pulmonary artery.
The pulmonary artery quickly divides
into two branches.
Each branch of the pulmonary artery
carries blood to a lung.
In the lungs the pulmonary arteries
branch into capillaries that
surround the alveoli.
Through diffusion, carbon dioxide
moves from the blood into the
alveoli and oxygen moves from the
alveoli into the blood.
The oxygenated blood then returns
to the heart through the
pulmonary vein into the left
atrium.
From the left atrium, the blood
flows through the left atrioventricular
(bicuspid) valve into the left
ventricle.
The thick-walled left ventricle pumps
the blood through the aortic valve
into the aorta.
The amount of pressure that is
required for pulmonary circulation is
much less than what is required for
systemic circulation.
Therefore, the muscle mass developed
in the right ventricle is much less than
that of the left ventricle.
Un-oxygenated blood is dark or
brownish red, while oxygenated blood
is bright red.
In the pulmonary system,
un-oxygenated blood is carried by the
pulmonary arteries and oxygenated
blood is carried by pulmonary veins.
In the systemic system, arteries carry
oxygenated blood and veins carry unoxygenated blood.
The Systemic Circulation System
The systemic circulation includes
the flow of oxygenated blood from
the heart to the tissues in all parts
of the body and the return of
un-oxygenated blood back to the
heart.
The blood vessels, including the
arteries, capillaries, and veins,
are the main parts of systemic
circulation.
Through systemic circulation,
oxygen and nutrients are delivered
to the body tissues via the arteries.
Blood is filtered during systemic
circulation by the kidneys (most of
the waste) and liver (sugars).
The systemic circulatory system is
complex and its functions vary.
The systemic circulatory system is
divided into subsystems for particular
regions of the body.
The Flow of Blood Through the
Systemic Circulatory System
Oxygenated blood
leaves the left
ventricle of the heart
through the aorta,
the largest artery in
the body.
The left and right coronary
arteries immediately branch from
the aorta and carry fresh blood to
the heart muscle itself.
The coronary veins quickly return
that blood back to the heart.
A heart attack often involves a
clot in the coronary arteries or their
branches.
In this illustration, a
clot is shown in the
location of #1. Area
#2 shows the portion
of the damaged heart
that is affected by
the clot.
Image by J. Heuser courtesy of Wikipedia.
The brachiocephalic trunk is the
next branch from the aorta.
The carotid arteries branch off
the brachiocephalic trunk and carry
oxygenated blood to the neck and
head region.
Blood from the neck and head
region is returned by the jugular
veins.
The left and right brachial
arteries also branch from the
brachiocephalic trunk to supply
blood to the shoulders and forelegs.
The thoracic aorta refers to the
portion of the aorta that goes from
the heart, through the thoracic
cavity to the diaphragm.
The portion of the aorta that goes
from the diaphragm, through the
abdominal region, to the last
lumbar vertebrae is called the
abdominal aorta.
Branches from the thoracic aorta
supply oxygenated blood to the
lungs (via bronchial arteries),
esophagus, ribs, and diaphragm.
The celiac artery branches from
the aorta immediately past the
diaphragm and itself branches into
the gastric, splenic, and hepatic
arteries.
The gastric artery supplies blood
to the stomach.
The splenic artery supplies blood
to the spleen.
The hepatic artery supplies blood
to the liver.
The cranial and caudal mesenteric
arteries branch from the abdominal
aorta and carry blood to the small
and large intestines.
The renal arteries are next to
branch from the abdominal aorta.
The renal arteries have two
important functions:
• supply blood to the kidneys, and
• carry large volumes of blood to
the kidneys for filtration and
purification.
From the renal arteries arise
arteries that supply blood to the
testicles in males (internal
spermatic arteries) and parts of
the reproductive system in females
(uteroovarian arteries).
The abdominal aorta ends where it
branches into the internal and
external iliac arteries.
The internal iliac artery supplies
blood to the pelvic and hip region.
The external iliac artery branches
into the femoral arteries.
The femoral arteries and their
branches supply oxygenated blood
to the hind legs.
Veins normally accompany arteries
and often have similar names.
Veins are always larger than the
arteries and are sometimes more
visible than arteries because they
are closer to the skin surface.
Most veins eventually empty the
un-oxygenated blood into the vena
cavas.
The cranial veins return the blood
from the head, neck, forelegs, and
part of the thoracic cavity to the
right atrium of the heart via the
superior vena cava.
These cranial veins include the
jugular vein, brachial veins,
internal thoracic veins, and the
vertebral veins.
The caudal veins return blood
from the iliac, lumbar, renal,
and adrenal veins to the right
atrium of the heart via the
inferior vena cava.
Before blood is returned to the
heart from the stomach, pancreas,
small intestine, and spleen, it goes
through the liver for filtration.
This portion of the systemic system
is known as the hepatic portal
system.
The gastric vein (stomach),
splenic vein (spleen), pancreatic
vein (pancreas), and mesenteric
veins (small intestines) empty into
the portal vein that carries the
blood to the liver.
In the liver, the portal vein branches
into smaller venules and finally into
capillary beds.
In the capillary beds of the liver,
nutrients are exchanged for storage
and the blood is purified.
The capillaries then join into venules
that empty into the hepatic vein,
which carries blood to the inferior
(caudal) vena cava.
Photo from Wikepedia.
Liver of a sheep: (1) right lobe, (2) left lobe, (3) caudate lobe, (4) quadrate
lobe, (5) hepatic artery and portal vein, (6) hepatic lymph nodes, (7) gall
bladder.
Anatomy and Physiology of
the Lymphatic System
The lymphatic system is part of
the immune system and acts as a
secondary (accessory) circulatory
system.
Functions of the lymphatic system:
• remove excess fluids from body
tissues,
• absorb fatty acid and transport
fat to circulatory system, and
• produce immune cells
(lymphocytes, monocytes,
and plasma cells).
Blood fluid escapes through the
thin-walled capillaries into spaces
between body tissue cells.
Lymph vessels, which have very
thin walls, pick up these fluids
called lymph.
Flow of Blood & Lymph Within Tissue
The lymph vessels join to form
larger ducts that pass through
lymph nodes (or glands).
Each lymph node has a fibrous
outer covering (capsule), a
cortex, and a medulla.
Photo from U. S. Federal Government courtesy of Wikipedia.
Lymph nodes filter foreign
substances, such as bacteria and
cancer cells, from the lymph before
it is re-entered into the blood
system through the larger veins.
Lymph nodes, which are scattered
among the lymph vessels, act as
the body’s first defense against
infection.
Lymph nodes produce the following
cells:
• Lymphocytes – a type of white
blood cell,
• Monocytes – a leukocyte that
protects against blood-borne
pathogens, and
• Plasma cells – produce antibodies.
Each lymph node has its own blood
supply and venous drainage.
The lymph nodes usually have names
that are related to their location in
the body.
When a specific location gets
infected, the lymph nodes in
that area will enlarge to fight
the infection.
If the lymph node closest to an
infected area is unable to
eliminate the infection, other
lymph nodes in the system will
attempt to fight the infection.
This is particularly critical in the
case of cancer, which can be
spread from its point of origin to
all parts of the body through the
lymphatic system.
Anatomy and Physiology
of the Blood
Blood is an important component
of the circulatory system.
Anatomically and functionally,
blood is a connective tissue.
The amount of blood that a
domestic animal has is expressed in
terms of percentage of body weight.
EXPECTED VOLUME OF BLOOD IN
DOMESTIC ANIMALS
Domestic Animal
% of Body Weight
Cattle
7.7 %
Sheep
8.0%
Horses
9.7%
Components of Blood
Plasma, which makes up 50 –
65% of the total volume of blood, is
a straw-colored liquid containing
water (90%) and solids (10%).
The solids in plasma include
inorganic salts and organic
substances such as antibodies,
hormones, vitamins, enzymes,
proteins, and glucose (blood sugar).
The non-plasma, or cellular, portion
of blood is composed of red blood
cells, white blood cells, and platelets.
From left to right:
Red blood cell
(erythrocyte);
Platelet
(thrombocyte);
White blood
cell (leukocyte).
Photo from U. S. Federal Government courtesy of Wikipedia.
Red blood cells, called erythrocytes,
are responsible for carrying oxygen
from the lungs to various body
tissues.
Red blood cells contain hemoglobin,
which gives them their characteristic
red color and helps them carry the
oxygen.
Red blood cells are biconcave discs, a
shape that provides a large area for
oxygen exchange.
Red blood cells are produced in the
red marrow of bones.
Most domestic animals have a red
blood cell count of seven million
cells per cubic millimeter of blood.
Red blood cells will last from 90 to
120 days and are removed from
the blood by the spleen, liver, bone
marrow, or lymph nodes when
they are worn out.
Anemia is a condition caused by low
levels of red blood cells and
hemoglobin.
Anemia can be caused by the following:
• Loss of blood due to injury,
• Infestations of blood-sucking
parasites, or
• Low levels of red cell production due
to poor nutrition.
Hemoconcentration is a
condition in which there is an above
normal level of red blood cells.
Hemoconcentration is normally
caused by dehydration (loss of body
fluid), which can be the result of
vomiting, diarrhea, or any chronic
disease characterized by high body
temperatures.
Blood platelets, or thrombocytes,
are oval-shaped discs that are
formed in the bone marrow.
Blood platelets help prevent blood
loss from injuries to blood vessels
by forming clots (white thrombus).
Platelets may secrete a substance
that causes the clot to contract
and solidify.
Platelets may also secrete a
substance that causes an injured
vessel to constrict at the injury.
White blood cells, or leukocytes, are
divided into two general categories:
• Granulocytes, and
• Agranulocytes.
Granulocytes are the category of
leukocytes that contain granules
within the cytoplasm.
Granulocytes include:
• Neutrophils,
• Eosinophils, and
• Basophils.
Neutrophils – produced by bone
marrow, neutrophils fight disease by
migrating to the point of infection,
absorbing bacteria, and destroying
them.
Neutrophil (purple) migrating through tissue
to engulf bacteria through phagocytosis.
Neutrophils dissolve
dead tissue resulting
in a semi-liquid
material called pus.
Courtesy of Wikipedia.
Abscess – a concentrated area of pus.
Eosinophils - a type of granulocyte
that plays a role in combating
infection by parasites, as well as,
impacting allergies and asthma.
They contain most
of the histamine
protein in the blood,
which is an
indication of allergic
reaction when elevated.
Images courtesy of Wikipedia.
Basophils – rare granulocytes that
are responsible for the symptoms
of allergies, including inflammation.
Basophils
Image courtesy of Wikipedia.
Agranulocytes are the category
of leukocytes that contain very
little, if any, granules.
Agranulocytes are produced by
the lymph nodes, spleen, thymus,
and other lymphoid tissue.
There are two types of agranulocytes:
• Lymphocytes, and
• Monocytes.
Lymphocytes – agranulocytes that
produce and release antibodies at
site of infections to fight disease.
Lymphocytes also
produce antibodies
that allow an animal
to build up immunities
to a particular disease.
Image from U. S. Federal Government courtesy of Wikipedia.
Monocytes are agranulocytes that
absorb disease-producing materials,
such as bacteria that cause
tuberculosis, through phagocytosis.
Unlike neutrophils,
monocytes do not
produce pus.
Image courtesy of Wikipedia.
Monocytes join body tissue to form
larger, disease-absorbing masses
called macrophages.
In domestic animals, approximately
85% to 90% of the leukocytes in
domestic mammals are neutrophils
and lymphocytes.
The total number of neutrophils and
lymphocytes are about equal, but
temporary stress increases the ratio
of neutrophils to lymphocytes until
that stress is removed.
When bacterial infections occur,
the number of white blood cells
normally increases.
When viral infections occur, the
number of white blood cells
normally decreases.
Therefore, the concentration of
white blood cells can help
diagnose disease.
Blood clotting is called
coagulation and is important in
reducing blood loss caused by
injury and in healing the injury.
Fibrin is a thread-like mass
produced by fibrinogen (fibrous
protein in blood) and thrombin.
Fibrin holds the red blood cells,
white blood cells, and platelets
together to form a blood clot.
White Cell Counts and Coagulation
Times for Domestic Animals
Species
Normal White Cell Count
Coagulation Time
( Per Cubic Millimeter)
Cattle
9,000
6 ½ Minutes
Swine
15,000
3 ½ Minutes
Sheep
8,000
2 ½ Minutes
Horses
9,000
11 ½ Minutes
Vitamin K helps maintain
Antithromboplastin and
antithrombin, which are two
substances that prevent blood
from clotting within the
circulatory system.
Blood types are classified based on
certain antigens and antibodies
found on surface of red blood cells.
For example, in humans there are a
total of 29 blood group systems based
on antigens on the surface of the red
blood cells, but the ABO and Rhesus
factor (positive or negative) are the
commonly used groups to determine
blood type.
Human ABO Blood Types
Image courtesy of Wikipedia.
Young animals can receive certain
antibodies from their mothers.
These antibodies must be passed
on to the young animal through
the colostrum milk because the
placental membrane is fairly
impermeable.
When two different blood types, an
antigen and its antibody, combine
as a result of mating, the reaction
would cause agglutination or the
clumping together of red blood
cells.
This may cause some deaths
during the early embryonic
development in animals.
Many blood types and groups have
been identified in domestic animals.
• Cattle have 9 recognized blood
groups;
• Horses have 8 recognized blood
groups; and
• Canine have 13 described groups,
but only 8 recognized groups.
Some blood types can cause disease
in the offspring of animals.
Individual animals and their parents
can be identified using blood-typing.
Bulls used for commercial artificial
insemination must be blood-typed.
Certain blood types may be
connected to superior production
and/or performance in animals.
For example, egg production and
hatchability can be improved in
chickens and Pork Stress Syndrome
(PSS) can be identified in swine.
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2007