circulatory systemstaff.camas.wednet.edu/.../10/32-circulatory-system1.pdf · 2019-03-06 ·...
TRANSCRIPT
Chapter 32
Circulatory System
Invertebrates w/o a Circulatory System
If an organism has a sac body plan, circulatory systems are
not necessary.
Sac body plans mean cells are capable of gas and nutrient exchange
individually
Simple diffusion and osmosis principles are all that is necessary
Single-celled organisms or members of the cnidarian phyla (sea
anemones, jellyfish, etc)
For other organisms, cells do not always have direct access to
nutrients and gasses.
These organisms need a circulatory system, or a system of
transporting water, gasses, and nutrients throughout an organism
from specified entry and exit points.
Open Circulatory System
In open circulatory systems the circulatory fluid itself makes
contact with the environment.
Most mollusks and arthropods have open circulatory systems
with hemolymph (a mixture of blood and interstitial fluid)
instead of pure blood
The hearts of these organisms pump hemolymph into body cavities
called hemocoels.
The hemolymph contains nutrients, but no oxygen. Eventually, the
hemolymph releases its nutrients then makes it’s way back to the heart
for circulation.
For oxygen, organisms have special air tubes called trachea.
Trachea flow all throughout the body, providing gas exchange for
individual cells that is independent from the blood and heart.
Closed Circulatory System
A few members of the mollusk and arthropod classes have a
closed circulatory system.
Blood (a mixture of cells and plasma) is pumped by the
heart into a system of branching blood vessels.
Some organisms, like earthworms, even contain multiple hearts
Red blood cells contains a pigment called hemoglobin, which
turns the blood of closed circulatory systems red.
Blood is capable of carrying both nutrients and oxygen to the
cells of the organism.
Some gas exchange always occurs through the body wall or epidermis
in organisms. For humans, hardly any. For earthworms, it’s a much
higher percentage.
Cardiovascular System All vertebrates have a closed circulatory system called a
cardiovascular system.
The cardiovascular system uses an organ called a heart for
pumping substances, and contains 3 types of vascular tissue
called blood vessels (vascular=transport)
Arteries: carry blood away from the heart
Capillaries: exchange materials with tissue fluid
Veins: return blood to the heart
Arteries have thick walls that are able to expand and aid in
pumping blood.
Arterioles are smaller arteries that branch into capillaries
Capillary beds allow for exchange of nutrients and waste for the cells
Veinules carry deoxygenated blood and waste materials into veins
Heartarteryarteriolecapillariescapillary bedscellscapillary
bedscapillariesveinulesveinsheart
Circulatory System Pathways
Vertebrates show three separate circulatory pathways
1) One-circuit (single-loop) system (Fishes)
The heart has a single atrium and a single ventricle.
Blood is oxygenated at gills then carried throughout the body.
2) Two-circuit (double-loop), single ventricle system (Amphibians and most reptiles)
The heart pumps blood to the tissues (the systemic circuit) and also to the lungs (the pulmonary circuit)
This is an evolutionary trait of air-breathing organisms
3) Two-circuit, double ventricle system (Crocodiles, birds and mammals)
A separate atrium and ventricle for each circuit.
Helps to ensure the blood pressure is adjustable for both the systemic and pulmonary circuit)
The Human Heart
The human heart is located between the two lungs and is tilted
toward the left side of the organism (all directions are from the
perspective of the organism the heart belongs to)
The major portion of the heart is the myocardium, which
contains the cardiac muscle that pumps the blood
The heart lies within the pericardium, a membranous sac that
secretes lubricating fluid (like engine oil).
The inner heart itself is separated by a septum, a wall dividing
the heart into the right and left sides.
The two upper chambers of the heart are the atria, while the
lower chambers are the ventricles
The Human Heart
The heart has four valves which direct the flow of blood and prevent
its backward movement.
Between the atria and ventricles the valves are called the atrioventricular
valves.
Between the ventricles and their attached vessels, the valves are called the
semilunar valves
They look like half-moons.
The vein carrying blood from the body to the heart is the Vena Cava
(Inferior/Superior)
The vein carrying blood from to lungs to heart is the Pulmonary Vein
The artery carrying blood from heart to lungs is the Pulmonary
Artery
The artery carrying blood from the heart to the rest of the body is
the Aorta
The Human Heart
The two Vena Cava veins carry
O2-poor and CO2-rich blood
from the body where it enters
the right atrium.
The tricuspid valve opens and
allows a specific amount of
blood to enter the right
ventricle
The right ventricle pushes the
blood through the pulmonary
valve into the pulmonary artery,
where it will travel to the lungs
for oxygenation
The Human Heart
Four pulmonary veins bring O2-
rich blood back from the lungs
to the left atrium
The bicuspid valve opens and
lets blood flow into the left
ventricle
The left ventricle pushes blood
through the aortic valve into the
aorta, where it takes blood
throughout the body
Heartbeat
Each heartbeat lasts around .85 seconds, for 70 beats per minute
Systole refers to when the heart chambers contract, while
diastole refers to when the chambers relax.
The heartbeat’s familiar “lub dub” sound is the valves opening
and closing
“lub”—the atrioventricular valves closing
“dub”—the semilunar valves closing
“pause”—while the atria fill with blood
The rhythmic contraction of the heart is due to the cardiac
conduction system, run by nodal tissue
SA node (sinoatrial): pacemaker
AV node (atrioventricular): opens the ventricle valves
Blood Pressure
As blood is pushed out of the ventricles, blood pressure
rises.
As blood flows from the aorta into the arteries and
arterioles, blood pressure falls.
Veins, however, have too low of blood pressure to push
blood back toward the heart. Instead, skeletal muscles aid
the veins
Veins also have tiny valves which prevent blood from
flowing backwards
Blood pressure is measured with a sphygmomanometer and
recorded in mm HG (millimeters of mercury)
Cardiovascular Disorders
Hypertension
Hypertension is high blood pressure
Hypertension is usually not detected until a stroke or heart attack
occurs
Atherosclerosis
Accumulation of soft masses of fatty materials such as cholesterol
The plaque causes clots to form, which can either remain stationary
(thrombus) or move with the blood (embolus)
Stroke
An embolus blocks the cranial artery, preventing oxygen from getting
to the brain
Heart attack
When a portion of heart muscle dies due to blockage
Blood
Blood consists of
1) transport substances for the capillaries,
2) immune agents for fighting off foreign invaders and transporting
combative agents,
3) body temperature regulators
4) clotting factors
Formed Elements
The red and white blood cells (discussed in ch 33)
Plasma
Water, proteins, salts, gases, nutrients, wastes and
hormones
Red Blood Cells
There are 6 million blood cells for every cubic mm of blood.
Each blood cell contains 250 million hemoglobin molecules
Hemoglobin, a combination of protein and iron, is able to
electrically hold 4 oxygen molecules/molecule of hemoglobin.
RBC’s are manufactured in the marrow of the skull, ribs,
vertebrae and long bones.
RBC’s contain no nucleus. They live for 120 days and then are
swallowed by the liver or spleen for recycling
The iron is returned to marrow for reuse; the heme of the
blood is released as waste
Hence, the reddish-brown hue of feces
Platelets
Platelets are small factors that are involved in the 12 steps of
blood clotting.
When a blood vessel is damaged, platelets clump at the site and
partially seal the leak.
Cell tissues release prothrombin, which activates the production
of thrombin.
Thrombin then activates fibrins, which will thread around a
platelet until the injury is sealed.
The process is complicated because formation of clots (scabs) can be
deadly if it happens at the wrong time.
The complicated process virtually ensures clotting only occurs when
necessary, never by accident.
Extra Credit Question
This question is worth an extra 5% on your essay
exam
You may check your answers with me ahead of
time for a yes or no response as many times as you
like.
•Acetomenaphin is a common drug for pain relief. It works by reducing areas of inflammation, and is powerful enough to survive gastric acid in the stomach. Yet, even a slight overdose can be fatal to a cell. How does acetomenaphin know how to target only “sick” cells and not overdose “healthy” cells?