Transcript 6.2 – The Blood System

6.2 – The Blood System
I. Blood vessels
A. Arteries
1. Walls of smooth muscle and elastic fibers Helps maintain and withstand high pressure
2. Branch into arterioles, which branch into
capillaries
B. Capillaries
1. Form “beds” to allow gas exchange in all
areas of the body - diffusion of O2 and CO2
from high concentration to low
2. Merge to form venules
C. Veins – form from merged venules
Arteries
Capillaries
Veins
Carry blood away from
heart
Exchange of gases with
tissues
Carry blood back to the
heart
Thick walled
1 cell thick
Thin walled
No exchange
All exchange
No exchange
No valves
No valves
Valves
High pressure
Low pressure
Low pressure
Small lumen
Lumen 1 cell wide
Larger lumen
II.
The Heart -2 side-by-side pumps that take blood in and
pump it out, creating 2 circuits (William Harvey – 1628)
1. Pulmonary – to lungs and back
2. Systemic – to rest of body
-From body, blood enters heart through vena cava
-Collects in right atrium
-Atria contract and move blood through atrioventricular
valve to right ventricle
-Ventricle contracts – closes atrioventricular valve to
prevent backflow – increase pressure in ventricle and
opens semilunar valve, pushing blood into pulmonary
artery
-Blood goes to lungs where it drops off CO2 and picks up
O2-Returns to heart through pulmonary veins
-Enters left atrium, through atrioventricular valve to left
ventricle, through semilunar valve to aorta
-Aorta branches to send blood to rest of body where it
drops of O2 and picks up CO2
III. Blood – NOT blue!
A. Components
1.
2.
3.
4.
Plasma – liquid portion, mostly water
Erythrocytes – Red blood cells, carry O2 & CO2
Leucocytes – White blood cells
Platelets – cell fragments for clotting
B. Transports
1.
2.
3.
4.
5.
6.
7.
Nutrients – glucose, amino acids, etc.
O2 – reactant for cellular respiration
CO2 – waste product of cellular respiration
Hormones – transported from glands to target cells
Antibodies – proteins for immunity
Urea – nitrogenous waster
Heat- skin arterioles open/dilate to gain/lose heat
IV. Control of Heart Rate
A. Myogenic muscle contractions – contracts and relaxes
without nervous system control
B. Sinoatrial node (SA node) – mass of tissue located in
the right atrium
1. acts as a natural pacemaker
2. initiates contraction of both
atria and sends out signals to AV
node after .8 seconds
C. Atrioventricular Node (AV Node)
1. also in right atrium
2. Receives signal from SA node, waits .1 sec and
sends out its own signal to ventricles to contract
D. If there is an increased demand for O2 and to get rid of CO2
(ex. during exercise), brain gets involved
1. Medulla oblongata senses increase in CO2, sends
signal through cardiac nerve to SA node to increase rate
at which heart contracts
2. Once demand returns
to normal, medulla sends
message through vagus
nerve for SA node that
take back control
E. Chemicals can also increase heart rate
1. Adrenaline (epinephrine)
a. Secreted by adrenal glands (which sit on top of
kidneys) when stressed or excited
b. Causes SA node to fire more rapidly
V.
Pressure & Volume in the heart
A. Diastole – not contracting
B. Systole – contracting
C. As blood enters the atria, the atrioventricular valves
are closed. The increase in volume increases pressure.
D. Systole of atria pushes open atrioventricular valves
and moves blood into ventricles
E. Systole of ventricles forces atrioventricular valves
closed to prevent backflow (“lub”)
F. As ventricle contracts, pressure increase until
semilunar valves are forced open, pushing blood into
aorta/pulmonary artery
G. As contraction finishes, semilunar valve closes (“dub”)
VI. Heart Health
A. Atherosclerosis – build-up of plaque in the
arteries
1. Plaque is composed of lipids, cholesterol, cell
debris, calcium
2. Causes arteries to be less flexible
B. Heart attacks
1. Coronary arteries – 3, branch off aorta,
blood supply of heart muscle itself
2. Occlusion – when blood flow in an
artery is obstructed by plaque
3. Myocardial
Infarction – blood
supply to the heart
blocked -> dead
heart muscle