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Circulatory Systems
Outline
Transport in Vertebrates
Transport in Humans
Heartbeat
Vascular Pathways
Blood Pressure
Blood
Components
Clotting
Transport in Invertebrates
Open versus Closed Circulatory Systems
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Transport in Humans
Circulatory Systems
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Human Heart
Cone-shaped
Size of a fist-14cm long and 9cm wide
Inner surface is lined with endocardium
Thick muscular organ (special cardiac fibers)myocardium
Lies within the pericardium, a thick membranous sac that
secretes a lubricating liquid.
Circulatory Systems
Thoracic cavity
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Heart-lies behind the sternum and between lungs.
Circulatory Systems
Circulatory Systems
External Heart Anatomy
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Circulatory Systems
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Vascular Pathways
Human cardiovascular system includes two major
circular pathways:
Pulmonary Circuit
- Takes oxygen-poor blood to the lungs and returns
oxygen-rich blood to the heart
Systemic Circuit
- Takes blood throughout the body from the aorta to
the vena cava
Circulatory Systems
Path of Blood
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Human Heart:
Gross Anatomy
Circulatory Systems
Septum separates heart into left & right halves
The heart has four chambers
Upper two chambers are the atria
- Thin-walled
- Receive blood from circulation
Lower two chambers are the ventricles
- Thick-walled
- Pump blood away from heart
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Human Heart:
Valves
Circulatory Systems
Valves open and close to control blood flow
through heart
Atrioventricular valves (between the atria and
ventricles
- Tricuspid
- Bicuspid
Semilunar valves (between the ventricles and
their attached vessels)
- Pulmonary
- Aortic
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Circulatory Systems
Internal View of the Heart
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Cross-section of the heart
Circulatory Systems
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Circulatory Systems
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Transport in the Vertebrates
All vertebrates have a Closed Circulatory System
Heart pumps blood to capillaries
Gases and materials diffuse to and from nearby cells
Vessels return blood to heart without it contacting tissues
Oxygen-poor blood never mixes with oxygen-rich blood
(in humans)
Vertebrate vessels:
Arteries - Carry blood away from heart
Arterioles – Lead to capillaries
Capillaries - Exchange materials with tissue fluid
Venules - Lead to veins
Veins - Return blood to heart
Circulatory Systems
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Transport in Humans
Blood returning to heart from systemic circuit
Enters right atrium
Right atrium pumps through tricuspid valve to right
ventricle
Right ventricle pumps blood through pulmonary valve to
the pulmonary circuit
Blood returning to heart from pulmonary circuit
Enters left atrium
Left atrium pumps through mitral valve to left ventricle
Left ventricle pumps blood through aortic valve to the
systemic circuit
Circulatory Systems
Blood Flow Through the heart
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Circulatory Systems 16
Cardiac Cycle-70 beats/min
100,000 x a day or 40 million x a year
A single cardiac cycle is made up of the events
associated with one heart beat. Each cardiac
cycle takes about 8 tenths of one second.
During each cardiac cycle pressure changes
occur within the chambers of the heart as they
relax and contract.
As the chambers relax, they fill with blood,
diastole. When the chambers contract, this is
called systole.
Cardiac cycle
When the AV-opens-blood flows
into the ventricles from the atria
(semilunar valves are closed).
Atrial contraction results from a
series of events beginning with the
spread of nerve impulses from the
SA-node across the walls of the
atria.
Ventricular filling is completed by
atrial systole.
Impulses from the AV-node travels
along the ventricular conduction
fibers leading to contraction of the
ventricles.
Circulatory Systems
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Heartbeat
In ventricular systole, increased
pressure forces the AV valves
closed, “Lub” semilunar valves
open and blood is ejected from
the ventricles.
Ventricular diastole, pressure in
the ventricles decrease and
blood in the aorta and
pulmonary flows back toward
the chambers, causing these
valves to close “dub”.
Ventricular pressure falls below
that of the atria, AV valves
open and cycle begins again.
Circulatory Systems
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Circulatory Systems
Heartbeat
Electrocardiogram (ECG) Fluids contain ions that
conduct electrical currents, electrodes placed on the
skin are connected to a instrument that detects
electrical changes of the myocardium.
P- Atrial depolarization/systole
QRS- Ventricular depolarization
T-wave- Ventricular repolarization
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Conduction System of the Heart
Circulatory Systems
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Circulatory Systems
One way venous valves
During muscle contraction,
venous diameter
decreases, and venous
pressure rises. The
increase in pressure forces
the flow toward the heart.
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Circulatory Systems
Cross Section of a Valve in a Vein
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Circulatory Systems
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Blood Pressure
The beat of the heart supplies pressure that
keeps blood moving in the arteries
Systolic Pressure results from blood forced into
the arteries during ventricular systole
Diastolic Pressure is the pressure in the arteries
during during ventricular diastole
Skeletal muscle contraction pushes blood in the
veins toward the heart
Blood pressure
Normally measured with a sphygmomanometer
on the brachial artery
Expressed in the form: Systolic “over” Diastolic
Circulatory Systems
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Transport in Invertebrates
Small aquatic animals with no circulatory system
May rely on external water in gastrovascular
cavity to service cells
Roundworms and other pseudocoelomates
Use a fluid-filled body cavity as a means of
transporting substances
Fluid-filled cavity can also act as a hydrostatic
skeleton
Animals that have a rigid skeleton
May still rely on body fluids for the purpose of
locomotion
Bivalves pump hemolymph into the foot for
digging into mud
Aquatic Organisms
Without a Circulatory System
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Open vs. Closed
Invertebrate Circulation
Circulatory Systems
Two types of circulatory fluids:
Blood - contained within blood vessels
Hemolymph - flows into hemocoel
Open Circulatory System
Heart pumps hemolymph via vessels
Vessels empty into tissue spaces
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Open vs. Closed Circulatory Systems
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Transport in Birds and Mammals
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Comparison of Circulatory Circuits
in Vertebrates
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Circulatory Systems
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Comparison of Circulatory Pathways
Fish - Blood flows in single loop
Single atrium and single ventricle
Amphibians - Blood flows in double loop
Two atria with single ventricle
Other vertebrates - Blood flows in a double loop
Heart divided by septum into separate sides
Blood:
Homeostasis Functions
Circulatory Systems
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Transports substances to and from capillaries for
exchange with tissue fluid
Guards against pathogen invasion
Regulates body temperature
Buffers body pH
Maintain osmotic pressure
Clots prevent blood/fluid loss
Circulatory Systems
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Red Blood Cells
Small, biconcave disks
Lack a nucleus and contain hemoglobin
Hemoglobin contains
- Four globin protein chains
- Each associated with an iron-containing heme
- Manufactured continuously in bone marrow of skull,
ribs, vertebrae, and ends of long bones
Circulatory Systems
White Blood Cells
Most types larger than red blood cells
Contain a nucleus and lack hemoglobin
Important in inflammatory response
Neutrophils enter tissue fluid and phagocytize
foreign material
Lymphocytes (T Cells) attack infected cells
Antigens cause body to produce antibodies
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Composition of Blood
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Circulatory Systems
Platelets
Platelets
Result from fragmentation of megakaryocytes
Involved in coagulation
Blood clot consists of:
Platelets
Red blood cells
All entangled within fibrin threads
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Blood Clotting
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Circulatory Systems
Capillary Exchange
Capillaries very narrow – Tiny RBCs must go
through single file
Wall of capillaries very thin to facilitate diffusion
of nutrients, gasses and wastes
Oxygen and nutrients exit a capillary near the
arterial end
Carbon dioxide and waste molecules enter a
capillary near the venous end
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Capillary Exchange
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Capillary Bed
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Circulatory Systems
Review
Transport in Invertebrates
Open versus Closed Circulatory Systems
Transport in Vertebrates
Transport in Humans
Heartbeat
Vascular Pathways
Blood Pressure
Cardiovascular Disorders
Blood
Components
Clotting
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