Circulatory System

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Chapter 42

• Circulatory System

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Learning Objectives

• TBD

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Invertebrates with No Circulatory Systems

• Simple invertebrates sponges, cnidarians, and
  flatworms

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Animal Circulatory Systems

• Muscular heart pumps specialized fluid (such as
  blood) through tubular vessels
• Blood
• Carries O2 and nutrients to body tissues
• Carries away CO2 and wastes

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Open and Closed Circulatory Systems

• Open circulatory system
• In most invertebrates
• Heart pumps hemolymph into vessels that empty
  into body spaces (sinuses) before returning to
  the heart
• Closed circulatory system
• In some invertebrates and all vertebrates
• Blood is confined in blood vessels throughout the
  body (does not mix with interstitial fluid)

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Open and Closed Circulatory Systems
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Invertebrate Circulatory Systems

• Open circulatory systems occur in arthropods and
  most mollusks
• Closed circulatory systems occur in annelids and
  in mollusks such as squids and octopuses

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Vertebrate Circulatory Systems

• Evolved from a heart with a single series of
  chambers (single circuit) to a double heart that
  pumps blood through separate pulmonary and
  systemic circuits

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d. Circulatory system of crocodilians, birds, and
mammals
Lung capillaries
PULMONARY CIRCUIT
Right atrium
Left atrium
Left ventricle
Right ventricle
SYSTEMIC CIRCUIT
Capillary networks in other body tissues
In the four-chambered heart of crocodilians,
birds, and mammals, a complete septum forms two
ventricles and keeps the ?ow of oxygenated blood
from the lungs and deoxygenated blood entirely
separate from the rest of the body.
Fig. 42.5d, p. 952
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42.2 Blood and Its Components

• Plasma is an aqueous solution of proteins, ions,
  nutrient molecules, and gases
• Erythrocytes are the oxygen carriers of the blood
  
• Leukocytes provide the bodys front line of
  defense against disease
• Platelets induce blood clots that seal breaks in
  the circulatory system

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Mammalian Blood

• A fluid connective tissue
• Blood cells (erythrocytes, leukocytes, platelets)
• Suspended in a fluid matrix (plasma)

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Plasma and Plasma Proteins

• Contains water, ions, dissolved gases (O2 and
  CO2), glucose, amino acids, lipids, vitamins,
  hormones, and plasma proteins
• Plasma proteins
• Albumins (transport, osmotic balance, pH)
• Globulins (transport, immunoglobins)
• Fibrinogen (blood clotting)

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Blood Cells

• Erythrocytes
• Contain hemoglobin (transports O2 from lungs to
  body)
• Leukocytes
• Defend body against infecting pathogens
• Platelets
• Functional cell fragments that trigger clotting

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Erythrocyte (red blood cell)
Leukocyte (white blood cell)
Platelets
Fig. 42.6a, p. 954
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Plasma
Leukocytes and platelets
Packed cell volume, or hematocrit
Erythrocytes
Fig. 42.6b, p. 954
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Fig. 42.6c, p. 954
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Leukocytes
Monocyte/macrophage
Eosinophil
B lymphocyte
Basophil
T lymphocyte
Platelets
Neutrophil
megakaryocyte
Erythrocyte
Natural killer (NK) cell
Lymphoid stem cell
Myeloid stem cell
(marrow)
(lymph)
Pluripotent stem cell
Fig. 42.7, p. 955
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Types of Defense

• Non-specific
• Specific (antibody-mediated)

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Bacteria at injury site
1
Macrophages
Mast cells
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Cytokines
Capillary
Neutrophils
Chemokines
2
Histamine
4
3
Neutrophils sticking to wall
Endothelial cell of capillary
1. A break in the skin introduces bacteria.
2. Activated mast cells release histamine.
3. Histamine and cytokines dilate local blood
vessels.
4. Chemokines attract neutrophils, which pass
between cells of the blood vessel wall.
5 Neutrophils engulf the pathogens and destroy
them.
Fig. 43.1, p. 974
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Adaptive (Acquired) Immunity

• Triggered by antigens
• Exogenous or endogenous macromolecules (proteins
  or polysaccharides)
• Recognized by B cells and T cells via antibodies
• Targets particular pathogens or toxin molecules

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Light and Heavy Polypeptide Chains in an Antibody
Molecule
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b. Agglutination
Antibody
Antigen
Bacterium
Fig. 43.11b, p. 985
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Immunological Memory

• First encounter with an antigen elicits a primary
  immune response
• Later exposure to the same antigen elicits a
  rapid secondary immune response with a greater
  production of antibodies

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The Mammalian Heart

• A four-chambered pump
• Two atria at top of heart
• Two ventricles at bottom of heart
• Atrioventricular (AV) valves between atria and
  ventricles
• Semilunar (SL) valves between ventricles and
  aorta / pulmonary arteries
• Blood is pumped into two separate circuits
• Pulmonary circuit (right heart)- to the lungs
• Systemic circuit (left heart)- to the body

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Blood Vessels

• Blood leaves the heart in large arteries
• Branch into smaller arterioles
• Arterioles deliver blood to capillary networks
• Capillaries exchange substances between blood and
  interstitial fluid
• Small venules collect blood from capillaries
• Join into larger veins that return blood to heart

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To systemic circuit
To body
Aorta
Pulmonary arteries (to lungs)
VC-from body
Superior vena cava (returns blood from head,
upper limbs)
Left pulmonary veins (return blood from
lungs)From pulmonary circuit
Right pulmonary veins (return blood from lungs)
PV
Left atrium
Right atrium
AV
AV (MV) valve (shown open)
AV (TV) Valve (shown open)
Left ventricle
Right ventricle
Septum
Inferior vena cava (returns blood ?ow from trunk,
legs)
KEY
Semilunar (SL) valves Atrioventricular (AV) valves
To systemic circuit
Fig. 42-9, p. 957
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systemic circuit
Capillary networks of head and forelimbs
Superior vena cava
Pulmonary artery
Pulmonary artery
pulmonary circuit
pulmonary circuit
Aorta
LA
RA
LV
RV
Capillary network of right lung
Capillary network of left lung
Pulmonary vein
Pulmonary vein
Inferior vena cava
To lower body parts
Capillary networks of abdominal organs and lower
limbs
systemic circuit
Fig. 42.10, p. 958