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Circulation
Chapter 42
The Need for a Circulatory
System?
• One celled organisms (bacteria) do not have a
circulatory system—they rely solely on diffusion
• Cnidarians (hydra, jelly fish) do not have a true
circulatory system- the gastrovascular cavity
branch throughout the organism relying on
diffusion to distribute nutrients
• So why do other organisms need a circulatory
system?
The Basics of a Circulatory
System
• Circulatory fluid (ie: blood)
• Vessels
• A muscular pump (ie: a heart)
Invertebrate Circulation - Open
• Open Circulatory System –blood and interstitial
fluid (together called hemolymph) bathe organs
directly, blood is pumped to the spaces (sinuses)
around the organs and returns to the heart through
pores called ostia
• ex: mollusks and arthropods
• Advantage: requires less energy to maintain (as
compared to closed)
Open Circulatory System- the
grasshopper
Invertebrate Circulation - Closed
• Blood is moved through blood vessels and
is separate from interstitial fluid
• ex: earthworm, squid, octopi
• Advantage: more effective, faster
Closed Circulatory System – the
earthworm
All Vertebrate Circulation Has:
•
•
•
•
Closed circulatory system
AKA cardiovascular system
Heart- has atria and ventricles
Vessels: have arteries, veins and capillaries,
along with arterioles and venules
Parts of the Circulatory System
• Atria – chamber of heart that receives the blood
• Ventricles – chamber of heart that pumps blood
out of heart—more muscular
• Artery – pumps blood away from heart, flows into
arterioles then to capillaries
• Vein – capillary blood flows into venules which
turn into veins, then bringing blood to the heart
• Capillary – very thin vessels that allow for quick
diffusion
Fish Circulation
• Heart: one ventricle and one atria
• Gill Circulation: blood pumped from heart
to gills where gas exchange occurs
• Systemic Circulation: blood from gills gets
carried to all the other parts of the body
Amphibian Circulation
• Heart: 2 atria and one ventricle
• Artery out of ventricle splits into two:
pulmocutaneous circuit and the systemic
circuit – double circulation
Reptile Circulation
• Heart:3 chambers (ventricle is separated by
septum to prevent mixing of blood)
• Pulmonary and systemic (double
circulation) circuits
Mammals and Birds
• Heart: 4 chambered (completely separates
oxygen rich and poor blood), double
circulation
Vertebrate Circulation
Simple Diagram of Blood Flow
through Heart
• Superior and inferior
vena cava
• Pulmonary artery
• Pulmonary vein
• Aorta
Blood Flow through a
Mammalian Heart
The Heart
•
•
•
•
Cardiac Cycle – complete sequence of pumping and filling
Systole – contraction phase of heart
Diastole – relaxation phase of heart
Semilunar Valves –stop backflow of blood out of heart
“dub”
• Atrioventricular (AV)Valve – separate and stop backflow
of blood between atria and ventricles “lub”
• Sinoatrial (SA) Node – in RA, pacemaker, coordinates
contraction of atria
• Atrioventricular (AV) Node - receives message from SA
node and contracts ventricles
The Cardiac Cycle
• Diastole – during
relaxation phase blood
flows into the atria
• Atrial Systole –
contracts blood from
atria into ventricle
• Ventricular Systole –
contracts ventricular
blood into arteries
The Control of Heart Rhythm
Blood Vessels
• Arteries and veins made up of connective tissue
outside, smooth muscle in the middle and
endothelium in the middle
• Arteries – pump blood away from heart, have
more muscle, helps maintain blood pressure
• Veins – bring blood to the heart, valves, associated
with the skeletal muscles
• Capillaries – consist of only endothelium, very
thin to allow for diffusion between blood and ISF
Artery to Vein
Blood Pressure
• Blood Pressure – pressure blood puts on its vessels, highest
in arteries
• Systolic – pressure in arteries when heart contracts
• Diastolic – pressure when heart is relaxed
• Stress, high sodium diet, etc. can raise blood pressure
Lymphatic System
• Capillaries lose fluid as they diffuse materials
from blood to ISF
• The lymphatic system recycles this lost fluid
through lymph vessels- carries fluid called lymph
and returns it to circulatory system
• Lymph nodes are filled with WBC’s that attack
viruses and bacteria
• Why would your lymph nodes (“glands”) be
swollen when you are sick?
• What are the two major roles of the lymphatic
system?
The Fluid of the Blood
• Plasma – mainly water, also contains
proteins, ions, antibodies, fibrinogen,
nutrients, wastes, hormones; serves to
maintain osmotic balance and buffer the
blood
RBC’s
• AKA erythrocytes
• Small and biconcave to allow the most
surface area for oxygen transport
• Contain hemoglobin (contains iron) that
binds to oxygen
• Lack nuclei and mitochondria
• Why is it important that RBC’s do not have
mitochondria?
WBC’s
• AKA Leukocytes
• Involved in immune
system
• Found in blood, lymph
and ISF
• You can wait to learn
these cells until next
chapter!!!
Platelets
• Involved in clotting by serving as a physical barrier (plug)
to the wound, and by secreting chemical clotting factors
(prothrombin, thrombin and fibrinogen) that make fibrin
(a fibrous network)
Circulatory Diseases
• Hemophilia – genetic disease that results in
improper clotting
• Murmor – defect in heart valves, usually harmless
• Artherosclerosis – plaques narrow coronary
arteries
• High Cholesterol – HDL and LDL
• Hypertension – high blood pressure
• Heart Attack – blockage that stops blood flow to
heart, could result in death of the cardiac muscle
• Stroke – blockage in artery of head, result in death
of nervous tissue
The Respiratory System
• Gas exchange – uptake of oxygen and
release of carbon dioxide
• Need a respiratory surface- the place where
gases are exchanged
• Respiratory surface should be
high in surface area and moist
• COUNTERCURRENT
EXCHANGE
Respiratory Adaptations
• Respiratory Surface/ Organism
• Cell Membrane/ Unicellular and Simple
Animals
• Skin/earthworm (amphibians)
• Gills/aquatic organisms
• Tracheae/ insects
• Lungs and alveoli/ vertebrates
Gills as a Respiratory Surface
• Aquatic organisms
have no problem with
moisture, but water
has a low oxygen
content, therefore
ventilation (increasing
the flow) is necessary
• Countercurrent
exchange-blood flows
opposite to water flow
Countercurrent Exchange
Tracheal System as a Respiratory
System
Made up of air tubes which branch
to the surface of every cell
Alveoli are
interface between
the respiratory
system and the
circulatory system –
they are closely
related to capillaries
Lungs as a
Respiratory Surface
Parts of Mammalian Respiratory
System
Nose/Mouth
Larynx
Trachea
Bronchi
Bronchiole
Alveoli
Negative Pressure Breathing
• Pulls air into lungs (like a suction pump)
• Aided by the contraction of the diaphragm
Negative Pressure Breathing
Autonomic
Control of
Breathing
Pons and medulla
regulate breathing
Sensors respond
to pH changes –
lowered pH
signals increase
breathing
Respiratory Pigments
• Carry oxygen to increase efficiency
• Hemocyanin- contains copper, found in
arthropods
• Hemoglobin – contain iron, found in
vertebrates