Z333 Lecture

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Chapter 27:
Circulation
Chapter 27: Circulation
Types of Circulatory Systems:
1) Open Circulatory System:
• Open space present (hemocoel); blood bathes organs
• Arthropods (e.g. insects, crabs); mollusks (e.g. snails, clams)
2) Closed Circulatory System:
• Blood confined to heart / vessels
• Invertebrates (e.g. earthworms); vertebrates (e.g. humans)
Benefits:
1) Efficient transport
2)  blood pressure
(Figure 27.1)
Chapter 27: Circulation
Heart: Pump propelling blood through vessels
2 chambered
heart
3 chambered
heart
More effecient transfer
of oxygenated blood
4 chambered
heart
Circuits of the
Circulatory System:
Chapter 27: Circulation
Chapter 27: Circulation
Heart Anatomy:
Right atrium
Right ventricle
Atria:
Collect blood
from body
Left atrium
Left ventricle
Ventricles:
Circulate blood
through body
Chapter 27: Circulation
Heart Anatomy:
Aortic Arch
Pulmonary
Arteries
• Carries blood to
lungs
Pulmonary
Veins (4)
• Returns blood
from lungs
Vena Cavas
• Return blood
from body
Aorta
• Largest vessel
• Carries blood to body
Chapter 27: Circulation
Heart Anatomy:
Tricuspid
Valve
Pulmonary
Semilunar
Valve
Bicuspid (Mitral)
Valve
Aortic
Semilunar
Valve
Atrioventricular
Valves:
Semilunar
Valves:
Prevent backflow into
atria
Prevent backflow
into ventricles
Heart Anatomy:
Chapter 27: Circulation
(Figure 27.3)
Pathway
of Blood
Myocardial Infarction
(Heart attack):
• Prolonged blockage
of coronary vessels
Chapter 27: Circulation
Cardiac Cycle:
• Heart beats ~ 100,000 times / day
“Lub” = closing of
AV valves
“Dub” = closing of
SL valves
3) Heart relaxes; blood
flows passively into
chambers
1) Atria contract; blood
pushed into ventricles
2) Ventricles contract; blood
pushed to lungs / body
Chapter 27: Circulation
(Figure 27.7)
Coordination of Heart Contraction:
• Gap junctions allow cardiac muscles to synchronize contraction
1) Sinoatrial Node (SA Node) initiates contraction:
• Pacemaker cells
• Located in wall of right atrium
2) Atria contract
3) Signal delayed at
Atrioventricular Node
(AV Node)
• Allows for atria to
finish contraction
4) Ventricles contract
 Fibrillation
• Uncoordinated, irregular
contractions of heart
Chapter 27: Circulation
Nervous System / Hormones Influence Heart Rate:
• SA Node = 100 beats / min
• Nervous System:
• Parasympathetic System = Decreased heart rate
• Usually in control
• Sympathetic System = Increased heart rate
• Exercise; stress
• Endocrine System
• Epinephrine = Increased heart rate
Chapter 27: Circulation
Blood (“River of Life”):
Components:
1) Formed Elements (living cells)
• Erythrocytes (RBC’s)
• Carry oxygen
• Produced in bone marrow
• Lifespan = ~120 days
• Leukocytes (WBC’s)
• Immune function
• Produced in bone marrow
• Lifespan = days - years
Formed
Elements
Buffy Coat
(~1%)
Erythrocytes
(~45%)
• Platelets
• Blood clotting
• Produced in bone marrow
• Lifespan = 10 - 12 days
Volume = 5 - 6 L
Chapter 27: Circulation
Blood (“River of Life”):
Components:
2) Plasma (Non-cellular - Fluid)
• 50 - 60% blood volume
• Composition:
Plasma
1) Water (90%)
2) Proteins (8%)
• Regulate osmotic pressure
• Transport nutrients
• Clot blood
3) Other solutes (2%)
Formed
• Nutrients, Gases
Elements
• Wastes
• Hormones
Buffy Coat
(~1%)
Erythrocytes
(~45%)
Chapter 27: Circulation
Erythrocyte = Red blood cell
• Biconcave shape (“certs”)
• Increased surface area for gas exchange
• No nucleus (anucleate)
• Contains Hemoglobin
• Iron-containing protein which binds oxygen
• 4 O2 molecules / hemoglobin
• RBC production regulated by erythropoietin (hormone)
• Produced in kidney; targets bone marrow
•  erythropoietin =  RBC count
• Contain unique proteins on cell surface
• A and B proteins (Type A, B, AB, O)
• Rh factor (Type + or -)
Chapter 27: Circulation
Leukocyte = White blood cell
• Protect body against foreign invaders (e.g. bacteria)
• Utilize blood for transport
Chapter 27: Circulation
Platelets:
• Formed from fragmenting
megakaryoctyes (bone marrow)
• Initiate blood clotting:
1) Platelets stick to ruptured surface (plug)
2) Platelets initiate production of thrombin (enzyme)
• Thrombin constructs protein
web (fibrin) to seal rupture
(Figure 27.13)
Chapter 27: Circulation
Chapter 27: Circulation
Blood Vessels:
Arteries
Arterioles
Arteries
• Carry blood away from heart
• Thick-walled:
• Smooth muscle / elastic fibers
• Withstand high pressure
Capillaries
Heart
Veins
Venules
Chapter 27: Circulation
Blood Vessels:
Arteries
Arterioles
Arterioles
• Control distribution of blood flow
• Smooth muscle expands / contracts
• Under hormone / NS control
Capillaries
Heart
Veins
Venules
Chapter 27: Circulation
Blood Vessels:
Arteries
Arterioles
Capillaries
• Nutrients / waste exchanged with cells:
• Vessel wall one-cell thick
• Blood flow very slow
Capillaries
• Materials exit / enter via diffusion
Heart
Veins
Venules
Chapter 27: Circulation
Blood Vessels:
Arteries
Arterioles
Veins
• Carry blood towards the heart
• Thin-walled; large diameter
• 65% blood volume in veins
Capillaries
Heart
Veins
Venules
Chapter 27: Circulation
Blood Vessels:
Arteries
Arterioles
Veins
• Carry blood towards the heart
• Thin-walled; large diameter
• 65% blood volume in veins
Heart
Capillaries
• Low pressure system
• Blood return to heart assisted by:
1) Valves
2) Skeletal muscle pumps
Veins
Venules
Chapter 27: Circulation
Skeletal Muscle Pump:
Vein Valve:
(Figure 27.17)
Chapter 27: Circulation
Cardiovascular Disorders:
• Leading cause of death in the United States
1) Hypertension = High blood pressure
•  Resistance in vessels =  work for heart
• Angina = Chest pain (heart lacks O2)
• Stroke = Vessel ruptures in brain
2) Atherosclerosis = Deposits (plaques) collect in vessels
Figure E27-2
Chapter 27: Circulation
Lymph System:
• Vascular system closely associated with circulatory system
• Function:
• Return fluids to blood (lymph)
• Transport fats (small intestine  blood)
• Defend body against bacteria / viruses (store leukocytes)
• Components:
• Lymph vessels (capillaries  large vessels)
• Empty into circulatory system near heart
• Lymph nodes / tonsils (house leukocytes)
• Thymus: Gland which activates leukocytes
• Spleen: Filters blood / houses leukocytes
Elephantiasis
(Figure 27.18)

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