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Circulatory System
Mr. O. Tada
Dept of Livestock & Wildlife Management
Circulatory System
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Function
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Components
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Transport (nutrients, waste)
Transport media (blood or lymph fluid)
Vessels (arteries --bring blood away from heart)
Capillaries --In close contact with tissues for exchange
Veins--bring blood back to heart
Heart (pumps blood throughout the body)
Lymphatic system
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auxillary system of vessels
returns fluids from interstitial spaces to blood
Heart
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Cone-Shaped, Hollow, Muscular Structure
Base of cone (dorsal-cranial) enter large arteries
and veins
Other end is Apex of Heart (ventral-caudal)
Located in thoracic cavity
Pericardium
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Connective Tissue Sac in which the Heart lies
Two Layers: visceral (Epicardium) & Parietal
Slightly Fluid Filled (lubrication)
Heart cont’d
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Myocardium
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Muscular Part of Heart
Forms walls of Chambers
Four Chambers:
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Left and Right Atria
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Receive Blood From Veins
 Left from Pulmonary Vein
 Right from Vena Cava
Left and Right Ventricles
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Receive Blood From Atria
 Left Pump Blood through Aorta
 Right Pump Blood through Pulmonary Artery
Heart cont’d
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Endocardium
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Innermost Layer
Endothelium
Heart Valves
Atrioventricular Valves (A-V valves)
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Located between Atria and Ventricles
Right valve is tricuspid
Left valve is bicuspid/mitral valve
Prevent expulsion of ventricular blood in the atria
during heart contraction
Cordae Tendinae keep valves from inverting
Heart cont’d
Semilunar Valves
a. Located at exits of Ventricles
b. Both Tricuspid
c. Right Valve (--Pulmonary Semilunar)
d. Right Valve (--Aortic Semilunar)
Blood flow through the Heart
A. Vena Cava [Venous Blood, lost O2, gained CO2]
B. Right Atrium
C. Right Ventricle
D. Pulmonary Artery [still Venous Blood]
E. Lungs
F. Pulmonary Vein [oxygenated (Arterial Blood)]
G. Left Atrium
H. Left Ventricle
I. Aorta
The Heart Structure
Heart Valves
Blood Vessels
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General Structure
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Continuation of Heart
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Lined with endothelium
Order
Arteries
 Arterioles
 Capillaries
 Venules
 Veins
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Structure of an artery
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Help with pumping
Smaller arteries gain
more smooth muscle.
Control Blood Flow
Arterioles
Muscular just prior to
Capillaries
Precapillary Sphincters
Regulate Blood Flow to
Capillary beds
Capillaries
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Endothelial Tubes
Contain Slit Pores (Clefts)
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Diffusion
Transport of small particles (<4 nm)
Pinocytotic Vesicles
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Transport of larger particles (Proteins)
Structure of a vein
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Contain Smooth
Muscle
Increase resistance to
regulate blood flow
Increase Blood
Pressure
Backflow prevented
by Valves
Blood Circulatory System
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Systemic Circulation (Whole body except Lungs)
Aorta
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First Branch  Coronary Arteries (to Heart)
Second Branch  Carotids (to Brain)
Pulmonary Circulation (Lungs)
Portal Systems (Vein  Capillary  Vein)
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Hepatic Portal System
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Liver
Blood Cleansing
Hypothalamic-Pituitary Portal System
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Hormones Transport
Lymphatic System
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Lymph Vessels
 Blind beginnings in interstitial space (Lymph Capillaries)
 Vessels tend to parallel veins
 A few large vessels empty into veins
 Contain Valve to inhibit backflow
Lymph
 Fluid of Lymph Vessels
 Composition is similar to interstitial fluid
 Return proteins to Veins (Proteins don't normally diffuse well
back through the capillaries)
 Movement through vessels controlled by:
 Smooth muscle contraction
 Skeletal muscle movement
Lymphatic System cont’d
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Lymph Nodes
 Areas of concentrated lymphocytes and macrophages along
the lymphatic veins.
 Nodular structures located along lymph vessels
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Functions:
 Lymphocyte production
 Clean-up lymph
 Contain Fixed Macrophages
 Enlarge during infection
 Entrapment of bacteria and infection by-products
 Cancer cells can get entrapped
 Increase Lymphocyte production
Lymph Organs
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Absorbs excess fluid & its return to blood stream.
Absorbs fat in the villi of the small intestine
Vessels are closely associated with the circulatory system vessels.
Lymph capillaries are scatted throughout the body.
Lymph organs include the bone marrow, lymph nodes, spleen, and
thymus.
Bone marrow contains tissue that produces lymphocytes.
B-lymphocytes (B-cells) mature in the bone marrow.
T-lymphocytes (T-cells) mature in the thymus gland.
Other blood cells such as monocytes and leukocytes are produced in
the bone marrow.
Spleen
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If damaged or removed, individual more susceptible to
infections.
The thymus secretes a hormone, thymosin, that causes preT-cells to mature (in the thymus) into T-cells
Larger lymphoid organ of the body filled with blood.
Circulates blood rather than lymph
Functions:
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Filtration
 Removes old red blood cells
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Lymphocyte production
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RBC storage and release
Heart Rate and its Control
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Metabolic Rate
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Smaller animals faster rate (beats per minute) than larger animals
Younger faster than older animals
Autonomic Nervous System
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Sympathetic
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Parasympathetic
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Decreases rate
Auto-regulation
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Starling's Law
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Increases rate
Larger volume of diastole, greater strength of contraction
Reflexes
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Stretch & Pressure Receptors cause heart to increase/decrease rate
 Carotid Sinuses, Aortic Arch, Right Atrium