Transcript Circulatory System

The Heart
FUN FACTS
• Center of the circulatory system
• Beats over 100,000x/day
• Pumps 1835 gallons/day
• Study of the heart and
accompanying diseases
–cardiology
• Heart lies within the mediastinum
–Center of chest
• 2/3 lies to the left of the
mediastinum
Pericardium
• Prevents overdistension of the heart
• Anchors heart within mediastinum
Three layers to the heart
1. Epicardium: outer layer
2. Myocardium: middle layer made up of
cardiac muscle
3. Endocardium: inner lining of the heart,
covers valves and the tendons that hold
valves open
What is???
• Epicarditis
• Myocarditis
• Endocarditis
Four Chambers
• 2 atria (singular is atrium):
holding chambers of heart
• 2 ventricles: pump blood out of
heart to body
Blood Vessels
• Superior vena cava: brings oxygen-poor
blood to heart from upper portions of body.
• Inferior vena cava: brings oxygen-poor
blood to heart from lower portions of body
• Right and left pulmonary arteries: brings
oxygen-poor blood from heart to lungs
• Right and left pulmonary veins: brings
oxygenated blood from lungs back to heart
Question???
• How are pulmonary arteries and pulmonary
veins different from all other arteries and
veins in your body?
Valves
• Atrioventricular (AV) valves or cuspid
valves: between atria and ventricles
– Tricuspid: on right side of heart
– Bicuspid: on left side of heart
• Semilunar valves: between ventricles and
arteries leaving heart
– Pulmonary semilunar valve
– Aortic semilunar valve
Circulatory Problems
• Ischemia: reduced oxygen. Weakens
but does not kill heart cells
• Angina pectoralis: chest pain due to
ischemia
– Causes:
• Stress
• Over exertion
• Artherosclerosis
• Fever
• anemia
Myocardial Infarction
• Heart attack
• Infarction: death of tissue due to interrupted
heart flow
Conduction System
• Your heart is innervated by the autonomic
nervous system, but only to regulate speed
of contractions
• Heart has an internal conduction system
– Sinoatrial Node (SA node): special heart tissue
that causes heart to contract
A Cut To The Heart
SA node
• Called the “pacemaker”
• Self excitation about 75 times/minute
• Located in the right atrial wall just below
superior vena cava opening
• Initiates excitation…spreads to both atria.
– Causes them to contract
After spreading to atria
• AV node and bundle of His distribute
impulse to ventricles via Purkinje fibers
Blood Vessels
The 3 major types of vessels
Arteries – carry blood away from the heart
Veins – carry blood toward the heart
Capillaries – contact tissue cells (Serving cellular needs)
Capillaries
· Very narrow (10 µm diameter, the red blood cells that
travel through capillaries are 6 µm in diameter).
Blood
Functions
• Transports
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Dissolved gasses
Nutrients
Waste products to lungs and kidneys
Enzymes
Hormones from endocrine organs
Functions
• Regulates
• pH
• Electrolyte concentration of body fluids
• Body temperature
• Restricts fluid loss
• Defends pathogens and toxins
Components
• Blood is the body’s only fluid tissue
• It is composed of liquid plasma and formed
elements
• Plasma (55%)
– 90% water
– minerals, sugars, lipids, hormones,
proteins (fibrinogen, and albumen)
• Formed elements (45%) include:
– Erythrocytes, or red blood cells (RBCs)
– Leukocytes, or white blood cells (WBCs)
– Platelets
Physical Characteristics and
Volume
• Blood is a sticky, opaque fluid with a metallic taste
• Color varies from scarlet (oxygen-rich) to dark red
(oxygen-poor)
• The pH of blood is 7.35–7.45
• Blood accounts for approximately 8% of body weight
• Average volume of blood is 5–6 L for males, and 4–5 L
for females
Blood maintains:
• Appropriate body temperature by absorbing
and distributing heat
• Normal pH in body tissues using buffer
systems
• Adequate fluid volume in the circulatory
system
Protection
• Blood prevents blood loss by:
– Activating plasma proteins and platelets
– Initiating clot formation when a vessel is broken
• Blood prevents infection by:
– Synthesizing and utilizing antibodies
– Activating complement proteins
– Activating WBCs to defend the body against
foreign invaders
Erythrocytes (RBC’s)
Erythrocytes
• Biconcave discs & anucleate allow for a
huge surface area to volume ratio
• Hematocrit – percentage of RBCs out of the
total blood volume. (Ave) 46 adult men &
42 adult women.
• There are roughly 5 million RBCs in each
microliter of blood; they transport oxygen
and carbon dioxide, and have large surfaceto volume ratios.
• Red blood cells account for slightly less
than half the blood volume.
Erythrocytes
• Erythrocytes are unable to perform
normal maintenance operations and
usually degenerate after about 120
days in the circulation.
• Each red blood cell contains
molecules of hemoglobin (Hgb),
which can reversibly bind oxygen.
Leucocytes (White Blood Cells)
• Nuclei
• No hemoglobin
• Functions:
– leucocytes are phagocytic - What does that mean?
– effective against bacteria, viruses, fungi,
transplanted cells and cancer cells