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Circulatory Circulatory SystemsSystems Circulatory^ Systems
Functions:
- Transportation
- Water & electrolytes (salts)
- Dissolved gases— O 2 & CO 2
- Nutrients
- Wastes
- Chemical messengers
(hormones)
- Defense (immune) systems
- Repair (clotting) factors
- Thermoregulation
- Hydraulics Cardiovascular System Lymphatic System
Circulatory Systems
- Ciliated Body Cavity
- Open Circulatory System
- Closed Circulatory System
Hemocoel
Size & System Development
• Diffusion is sufficient for small
organisms w/ low volumes &
metabolic demands (e.g.
protozoans and micrometazoans).
Ciliated Body Cavity
Cnidarians & Platyhelmintheans
- gastrovascular system
- ciliated digestive cavity w/ branching extensions.
- water vascular system
- ciliated coelom w/ extensions
(dermal branchae
& tube feet)
for respiration.
hydraulic functions
Echinoderms Vascular System Components
- Four components are
- circulatory fluids
- vessels
- pump
- valves
- Vasculature (vessels) may form open or
closed circulatory system
Open Circulatory Systems
- In arthropods & most molluscs.
- 4-part system - what are those parts?
- circulatory fluids mix w/ interstial fluids of
body cavity.
- Hence, “blood” is called hemolymph. Open Circulatory Systems
- Dorsal heart pumps
hemolymph out
vessels into body
cavity (= hemocoel )
compartmentalized
into sinuses
to heart via ostia or
veins.
Open Circulatory Systems
Dorsal Vessel as Pump
may act as a tubular
heart
specialized into a heart
Molluscs
hemocoel by veins to
gills to heart to arteries
to hemocoel
Limitations of Open Systems
- Difficult to regulate different perfusion of
different tissues.
- Great for small body plans; not so great for
big bodies with variable metabolic activities.
- How can it be enhanced for large bodies?
Closed Circulatory Systems in Vertebrates
Mammals
- 4-chambered heart
- Double circuit :
- Pulmonary circuit: blood flows from heart to lungs only
- Systemic circuit: repressurized blood flows from heart to systemic vessels
- No mixing of deoxygenated + oxygenated blood
- Pulmonary & systemic circuits are pressurized differently
10x more efficient systemic oxygenation Closed Circulatory Systems in Vertebrates - Crocodilians - 4-chambered heart - 2 atria/2 ventricles - Double circuit : - 1. Pulmonary circuit: blood flows from heart to lungs only - 2. Systemic circuit: repressurized blood flows from heart to systemic vessels - Shunt to divert pulmonary to
systemic flow when
underwater
Review of Designs Mammalian Cardiovascular System
- Two circuits, each with its own 2-chamber pump
- Different pressure
- Same flow rate Mammalian Cardiovascular System
- Pulmonary circuit:
- Right pump Æ lungs Æ left pump
q Deoxygenated systemic blood
fills right A&V
q Right A&V contract pushing
deoxygenated blood through
pulmonary artery to lungs
q Release CO 2 q Take up O 2
q Oxygenated blood from lungs
flows through pulmonary veins
to left atrium
Mammalian Cardiovascular System
- Systemic circuit:
- Left pump Æ body Æ right pump
q Oxygenated pulmonary blood
fills left A&V
q Left A&V contract pushing
oxygenated blood through
aorta to branching major
arteries to all other body
organs
q Release O 2 q Take up CO 2
q Deoxygenated blood from
body tissues flows through
branches of veins converging
on vena cava to right atrium
The Pump
- For any pump to function, it needs
two components:
1. Constriction (stroke) chamber
Øchamber volume fi ↑pressure
fi move fluid
2. Valves
fi direct fluid flow direction
Human Heart Anatomy
heart from front
heart’s “left”
filled sac behind
sternum
Human heart in chest cavity
Cardiac Contractions
- Sinus node (pacemaker) fires
- Signal spreads across atria
- Cardiac muscle in atria contract
- Signal reaches AV node; travels down Bundle of HIS to apex of heart
- Signal spreads across venticles
- Cardiac muscle in venticles contract - Arteries – carry blood away from the heart - Arterioles – smaller branches of arteries - Capillaries – thin, microscopic, with porous walls - Venules – smaller branches that converge into veins - Veins – carry blood back to heart The Vessels Artery Vein SEM (^100) μm Endothelium Artery Smooth muscle Connective tissue Capillary Basal lamina Endothelium Smooth muscle Connective tissue Valve Vein Arteriole (^) Venule Red blood cell Capillary 15 μm LM Vessel Structure & Function
- Arteries: blood away from heart
- Thick-walled and elastic to withstand higher pressure
- Smooth muscle in arteriole walls regulate selective blood flow
- Veins: blood toward heart
- Thin, compliant walls
- Internal valves prevent backflow
- Capillaries: thin-walled and highly branched
- Only vessels exchanging with tissue fluids!
- Walls only 1 cell thick to maximize diffusion rates
- Not permeable to blood cells & proteins; permeable to water and other solutes (^) Fig. 42. Poisseuille’s Law
The Hagen-Poiseuille Equation:
- Flow rate = f = ( Dy p)( p r^4 )/(8L h )
where
ßDyp= pressure difference
ß r = radius
ßh = fluid viscosity
ßL = length of tube
- NOTE: Df proportional with Dr^4!
capillaries goes to
lymphatics
- 85-90% fluid returned to blood circulation
- 10-15% taken up by lymphatic capillaries Capillary exchange Lymphatic System
- Recaptures lost
fluids & proteins
filtered through
lymphoid tissues
and monitored by
immune system
system in vena cava
Lymph node Fluid Flow in Veins — both Cardiovascular & Lymphatic Systems
- Fluids pumped by “skeletal muscle pumps”
- Valves prevent backflow
The composition of blood
Blood: Liquid Tissue
Cells Suspended in Plasma
Blood Structure and Function
“Formed Elements” — cells and cell-derivatives
Since erythrocytes and thrombocytes lose their nuclei,
they are no longer truly cells.
- Erythrocytes (red blood cells)
- Leukocytes (white blood cells)
- Thrombocytes (platelets)
Plasma
- 90% H 2 O
- 7–9% protein Human blood smear ClottingClotting
- • Leukemia victims lack plateletsLeukemia victims lack platelets
- •^ HemophiliacsHemophiliacs lacklack^ clottingclotting factors.factors.
PlateletesPlateletes
ClottingClotting FactorsFactors
ProthrombinProthrombin ThrombinThrombin
FibrinogenFibrinogen FibrinFibrin
