Circulatory System
Circulatory System Directs blood from
the heart to the rest of the body;
and back again
3 Types of Blood Vessels
Arteries  carry blood away from the heart
Veins carry blood to the heart
Capillaries  allow for the exchange of
blood with tissue
Arteries
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Arteries have very thick walls and are
lined with squamous epithelial cells
Middle wall of the artery is composed
of elastic tissue and smooth muscle
Outer wall is made from
fibrous connective tissue
Arterioles are small arteries that
transport blood by constricting
and squeezing the blood
The more arterioles that are constricting,
the higher the blood pressure
Coronary Artery- Artery that
delivers blood to the heart
Veins and Capillaries
Veins
Take blood from the tissue back to the heart
Small veins (called venules) drain blood from the muscles
Veins often have valves that open and close; allows blood
to travel in 1 direction
Capillaries
Arteries dump blood into capillaries
Capillaries are extremely narrow (1 cell thick) tubes that
connect to muscles.
Located everywhere in the body; when cut you bleed
Primary role of capillaries is to bring oxygen, nutrients,
and water to tissue; take waste away from tissue
Veins and Capillaries
Veins often lie superficial to arteries in
the body, which is why we can
sometimes see them through the skin
Capillaries serve as the
dump- off point for O2 and
the pick up point for CO2
They also serve of the
cross-over between flow
from arteries to veins
The Heart
Size of your fist
Major portion of the heart is called the myocardium; made from cardiac muscle
Pericardium clear membrane “bag” that surrounds the heart
Inner surface of the heart consists of connective tissue
Right and left sides of the heart are separated by the septum
2 upper compartments are called atria
2 lower compartments are called ventricles
Blood moving from atria to ventricles must move through atrioventricular valves
AV valve on the right side is called the tricuspid valve (has 3 flaps)
AV valve on the left side is called the bicuspid valve (has 2 flaps)
Pulmonary semilunar valve directs blood from right ventricle to lungs
Aortic semilunar valve directs blood from left ventricle to body
The Heart
Views of the human heart
Path of the Blood through the Heart
Superior and Inferior vena cava send blood to right atrium
Right Atrium sends blood through tricuspid valve to right ventricle
Right Ventricle sends blood through pulmonary semilunar valve to
pulmonary arteries
Pulmonary arteries carry blood to the lungs
Pulmonary veins carry oxygenated blood (yes, that’s right) from the
lungs to the left atrium
Left atrium sends blood through bicuspid valve to left ventricle
Left ventricle pumps blood through aortic semilunar valve to the aorta
Aorta takes blood and distributes it to the body
Oxygenated and deoxygenated blood never mix!
Systemic Circuit
Heartbeat
Average heart beat lasts about .85
seconds
2 atria contract at the same time
2 ventricles contract at the same time
All chambers then relax
Systole  contraction of heart muscle
Diastole  relaxing of the heart
muscle
Normal Heart rate is anywhere
between 60-100 beats/minute
The Lub-Dub of the Heart
Lub AV valves close and atria contract
Dub  semilunar valves close
Surge of blood as left ventricle contracts causes the walls of the
arteries to stretch
The stretching of the walls is your pulse
Conduction of the Heartbeat
Nodal Tissue  Tissue that has both muscle and nervous
characteristics. It conducts electrical impulses that stimulates the
heart to beat
Sinoatrial Node  Found in the upper wall of the right atrium. SA
node initiates the heartbeat by sending out an electrical signal that
causes the atria to contract. Called the pacemaker of the heart
Atrioventricular Node found in the lower wall of the right atrium.
When electrical impulse reaches AV node, stimulates the ventricles
to contract
How Does the AV Node Tell the Ventricles to Contract?
Message is conducted from atria to ventricles
by small nerves called Purkinje Fibers
Recording the Heart’s Beat
When the heart beats, there are ionic changes
(Na+, Cl-, Ca+2) that can be detected and recorded
Electrocardiagram (EKG)
P Wave  Represents the contraction of the atria
QRS Wave  large spike which shows ventricular
contraction
T Wave  shows ventricular recovery
Nervous System Control of Heartbeat
Heart rate is controlled by the medulla oblongata (part of the brain stem)
MO regulates the Autonomic Nervous System, which has 2 divisions
Sympathetic Nervous System --> Fight or flight response; coordinates activities in
times of stress
Parasympathetic Nervous System  Coordinates normal activities, like sleep
Blood Pressure
BP is a measure of blood against the wall of a blood vessel
Systolic  Pressure during ventricular contraction
Diastolic -> pressure during ventricular relaxation
Blood pressure decreases as you move away from the left
ventricle
Sphygmomanometer measures brachial blood pressure
When cuff is tightened, it closes off the brachial artery
Systolic pressure is determined as pressure is released from
cuff; brachial artery is opening and closing, causing a pulse
Diastolic pressure is measured when artery is fully opened
(no pulse is heard)
Circulatory Disorders
Hypertension High blood pressure due to stress, vessel
constriction
Women: 160/95
Men 130/90
Atherosclerosis  accumulation of cholesterol in the arteries;
interferes with blood flow
Stroke -> Blood clots prevent blood from entering the brain; no
oxygen, part of the brain dies
Heart Attack  arteries that lead to the heart (coronary arteries)
are blocked; no oxygen to the heart; part of the heart dies
Varicose Veins  dilated veins in superficial areas.
Varicose veins in rectum = hemorrhoids
Your Heart & Medicine
Clearing Clogged Arteries
Angioplasty  plastic tube inserted into arm and run to the heart;
balloon is inflated, forcing the vessel to open
Coronary Bypass  vessel taken from another part of the body; then
used to connect the aorta to the unclogged portion of the coronary
artery
Dissolving Blood Clots
The drugs Streptokinase and tissue plasminogen activator (tPA) contain
plasminogen (found naturally in blood), which dissolves blood clots.
Usually given after a clot is already formed
People with symptoms of stroke or heart attack are usually given
aspirin, which reduces the “stickiness” of blood, lowering the
probability that a clot would form
Blood
Functions of Blood
Transport of gases, nutrients, waste
Regulate body temperature
Clotting to prevent infection
Fighting infections
2 Parts to Blood
Lower (dense) Layer  red blood cells, white blood cells, platelets
Upper Layer  plasma; water and suspended molecules (55% of total
blood)
Red Blood Cells  biconcave discs; lack nucleus; contains hemoglobin
Hemoglobin
Respiratory pigment that carries oxygen (red)
Each RBC contains 200 million hemoglobin molecules
Each hemoglobin molecule contains 4 protein molecules called heme
groups, which contain iron
Each heme group carries 1 oxygen molecule
Each 100 ml of blood carries 20ml of oxygen
Life Cycle of RBC’s
All RBC’s are made in bone marrow stem cells
As they mature, RBC’s lose their nucleus and gain hemoglobin
After 120 days, they are destroyed in the liver and the spleen
Red Blood Cells and Hemoglobin Molecules
Typical Red Blood Cells
Hemoglobin Molecule; Each molecule
can hold 4 oxygen molecules
Anemia
Insuffucient RBC’s, or lack of hemoglobin, results in
anemia
Individuals suffering from anemia often have tired, run
down feeling
Pernicious anemia  digestive tract can’t absorb B12,
which contributes to RBC formation
White Blood Cells
Nucleated cells that appear white in color
Not as numerous as RBC’s
Made by stem cells in bone marrow
Found in blood and tissue fluid
May live for days or years
Types of WBC’s
Granular leukocytes  contain large number of enzymes
+ antibodies
Agranular leukocytes  contain small number of enzymes
+ antibodies
White Blood Cells
The Fuzz Balls are White Blood Cells!
Granular Leukocytes
Neutrophils  most abundant WBC; first cells to respond to
an infection; Engulf bacteria via endocytosis
Eosinophils  Not much is known; tend to increase when
during large parasitic infections (tapeworms, liver flukes)
Basophils  Release histamine during allergic reactions.
Histamines dilate blood vessels increases fluid production
Neutrophils
Eosinophils
Agranular Leukocytes
Monocytes  largest of white blood cells
Form macrophages, which eat larger microbes in the body
Also stimulates other RBC’s to defend the body
B-Lymphocytes  produce antibodies that bind to, and kill,
antigens (chemical markers on bacteria)
T-Lymphocytes Kill any cell that has an antigen inside of it
Purple Cell = Monocyte
Green Cells = T-Lymphocytes
Blood Clotting and Platelets
Platelets  also known as thrombocytes
Made from fragmented cells in the bone marrow
Plug the blood vessels after an injury + aid in blood clotting
Clotting
After a cut
Platelets clump at the site of the puncture
Platelets also release prothrombin, which is converted to thrombin
Thrombin activates a chemical reaction that produces fibrin (a protein)
Fibrin wraps around the platelets at the site, trapping the red blood cells
around
the site + constricting the broken vessel
After the vessel is repaired, Fibrin is replaced by plasmin, which restores
the fluidity of the vessel