Download Structural Biochemistry/Cell Signaling Pathways/Circulatory System

Structural Biochemistry/Cell Signaling Pathways/Circulatory System
Structural Biochemistry/Cell Signaling
Pathways/Circulatory System
Circulatory System
The Circulatory System is an organ system that transfers the body's
essentials such as blood cells, nutrients, gases, and etc. to and from the
cells in order to maintain homeostasis. Under the circulatory system,
there are two systems: cardiovascular system and the lymphatic
system. The cardiovascular system consists of the heart, blood, and
blood vessels, while the lymphatic system is composed of the lymph,
lymph nodes, and lymph vessels.
Not all organisms require a circulatory system. Its primary purpose is
to distribute nutrients and essential elements like oxygen throughout
the cell. Smaller organisms, or those with a high surface area relative
to their volume, do not need a circulatory system because transfer can
take place directly across their cellular membranes. Flatworms are an
example of this; due to their size and shape, cells can obtain nutrients
and remove waste without the need for an extensive circulatory system
because diffusion is sufficient. Human beings, however, require a
circulatory system due to their size; for example, oxygen would not be
The human circulatory system.
able to effectively diffuse into organ cells without a circulatory system
because oxygen would have to go through our skin and into organ cells
for them to receive oxygen. In such a case, an internal circulatory system, a network of blood vessels, veins, and
arteries, is beneficial because nutrients and oxygen can be gathered at a central location and distributed throughout
the body.
In open circulatory system is the circulatory fluid bathes the organs directly. In these animals, the circulatory fluid,
called hemolymph is the same as interstitial fluid. The heart pumps hemplymph thorugh vessels into sinuses,
fluid-filled spaces where materials are exchanged between the hemolymph and cells. Arthropds and most mollusks
have an open circulatory system.
A closed circulatory system circulates blood entirely within vessels, so the blood is distinct from the interstial fluid.
One ore more hearts pump blood into large vessles that branch into smaller ones and the interstitial fluid bathing the
cells. For example, annelids, such as earthworms have closed circulatory system.
Pulmonary Circulation
Pulmonary circulation is the portion of the circulatory system which
carries oxygen-depleted blood away from the heart, to the lungs, and
then returns oxygenated blood back to the heart. The pathway that
blood takes in the pulmonary circuit starts at the right section of the
heart. Oxygen-depleted blood from the body enters the the heart
The pulmonary circuit.
through the right atrium where it pumped through the right
atrioventricular valve and into the right ventricle. The blood is then pumped into the two pulmonary arteries, one for
each lung, and travels into the lungs. The pulmonary arteries carry the deoxygenated blood to the lungs while the
pulmonary veins carry oxygenated blood to the red blood cells. There they release carbon dioxide and then pick up
oxygen during respiration. Now that the blood has been oxygenated, it leaves the lungs via the pulmonary veins and
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it returns to the left heart, completing the pulmonary cycle. The blood enters the left atrium and is pumped through
the left atrioventricular valve and into the left ventricle. From here, the blood is distributed to the body via the
systemic circulation before once again returning to the pulmonary circulation to pick up more oxygen.
Systemic Circulation
Systemic circulation, as indicated with the word "system" in the title itself, is all throughout the body. This
circulation's key role is to provide nourishment to all of the tissues located throughout your body. However, it does
not benefit the heart and lungs because they have their own systems. Nonetheless, systemic circulation is a vital
supporting piece of the circulatory system as a whole. The blood vessels, which consist of the arteries, veins, and
capillaries, are responsible for the delivery of oxygen and nutrients to the tissue. Oxygen rich blood enters the blood
vessels through the heart's major artery called the aorta. There exists the application of forceful contraction of the
heart's left ventricle which compels the blood to flow through the aorta and into smaller arteries to distribute
throughout the body. As a matter of fact, the inside layer of an artery is very smooth, thus allowing blood to flow
rather quickly. As the atrium contracts in the heart, more blood is filling the ventricles. Eventually, the
atrioventricular valve closes. The ventricles undergo isovolumetric contraction, which is when the ventricles contract
but the volume does not change. Once the pressure in the ventricles exceeds the pressure in the aorta will that aortic
valve open. In comparison to the inside layer of the artery, the outside of the artery is relatively strong, allowing
blood to flow forcefully. As the blood flows through the arteries, the velocity of flow is fast. This is because the
cross-sectional area of the arteries is small, and linear velocity is inversely proportional to the cross-sectional area.
Once blood reaches the capillaries, the velocity decreases because capillaries have a large cross-sectional area. The
second to last step of this systemic process involves oxygen-rich blood entering the capillaries where the oxygen and
nutrients are then released. The process concludes with the collection of waste products and waste-rich blood that
flow into veins to be taken back to the heart. The rest of the work is left to pulmonary circulation, which is
mentioned in the section above. Other key aspects of systemic circulation include the fact that blood passes through
the kidneys, which is known as renal circulation. During this phase, the kidneys filter as much of the waste from
blood as possible. Blood also makes its way through the small intestine, which is known as portal circulation. In this
phase, the blood from the small intestine collects in the portal vein which then passes through the liver. To explain
with more specificity, the liver filters sugars from blood, storing them for later.
Coronary Circulation
While pulmonary and systemic circulation provide oxygen and nutrients for the rest of the body, it is crucial not to
forget about the heart's everlasting desire for nutrients as well. This is pursued through coronary circulation which
refers to the movement of blood through the tissues of the heart. Despite the fact that blood fills the chambers of the
heart, the muscle tissue of heart which is referred to as myocardium, is so thick to the point that it requires blood
vessels to deliver blood deep into it. These blood vessels, responsible for delivering oxygen-rich blood to the
myocardium, are known as coronary arteries. The vessels responsible for the removal of deoxygenated blood from
the heart muscle are known as cardiac veins. The coronary arteries, when healthy, are capable of autoregulation to
maintain coronary blood flow at levels appropriate to the needs of the heart muscle. The critical nature of coronary
arteries are illustrated by means of classification as the "end circulation" because they represent the only source of
blood supply to the myocardium.
The coronary circulation of the heart consists of blood (a fluid that carries materials between the outside world and
the cells of the body), a lot of blood vessels (carrying blood throughout the body to deliver those nutrients to the
various cells), and the main component of the coronary circulation system, the heart (which forces blood into the
blood vessels. The pressure that the heart produces to push blood through the blood vessels is called the blood
pressure. If the blood pressure becomes inadequate to produce a large enough force for the blood to move into the
vessels, certain cells become starved for Oxygen, a condition referred to as ischemia.
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In coronary circulation, in order to understand how the heart and the blood vessels can respond to autonomic and
endocrine input and how they change their behavior, it is essential to look carefully at each of the components in the
cardiovascular system. The heart consists of two separate pumps, joined together. These two halves of the heart are
connected by parallel sets of blood vessels in series with one another. The right heart receives blood from most of the
body and pumps the blood into the vessels of the lungs (the pulmonary circulation); the left heart receives blood
from the lungs and pumps the blood into vessels into the rest of the body (the systemic circulation). Both the right
and left heart are separated in themselves into two subsections, the atriums and ventricles. Veins leading to the right
heart are connected to the right atrium at first. The bloods that enters the right atrium is then pumped into the right
ventricle, which is separated from the right atrium by the bicuspid valve. Once in the right ventricle, the blood
circulates through arteries and veins in the pulmonary circulation into the left atrium. Once in the left atrium, the
blood is allowed into the left ventricle as the mitral (tricuspid) valve opens and closes due to blood pressure
differences in the two compartments.
After release into the left ventricle, blood is propelled past the aortic valve to flow to the rest of the body. For the
reason that the left ventricle must produce enough force to send the blood through the rest of the body, the muscles
of the left ventricle are much stronger than the muscles of the right ventricle.
The output of blood in the two halves of the heart must be exactly equal to one another on a minute-to-minute basis
or else blood will be backed up in either the systemic or pulmonary circulation, which leads to major problems for
the entire circulatory system. Damage to the heart results in a heart pump with less efficiency. In congestive heart
failure, the left heart forces more blood than the right heart, a condition that is referred to as systemic edema. This
condition can be treated with drugs that increase fluid excretion and that increase the strength of the heart as a whole.
In left heart failure, the right heart pumps more blood than its counterpart, a condition referred to as pulmonary
edema. This condition interferes with gas exchange in the lungs and can produce suffocation. If the heart becomes
extremely weak overall, a condition referred to as congestive heart failure occurs. In congestive heart failure,
residual blood pressure in the heart causes the heart to become abnormally full, greatly stretching the heart muscles.
Under this condition, the heart becomes unable to even contract strongly and is unable to force any blood into the
great arteries. This situation must be remedied immediately or death follows.
Body Fluids
Body fluids are primarily distributed among three major compartments in the circulatory system. These three
compartments are the volume inside of the cells (the intracellular compartment), the volume inside the circulatory
system itself (the plasma compartment), and the volume that lies between the circulatory system and the intracellular
compartment (the interstitial compartment). Under normal conditions, the three different compartments are in
osmotic equilibrium with one another, but thy do contain different distributions of solutes. There is a lot of organic
anion (mostly proteins) inside cells, essentially none in the interstitial fluid, and a little in the plasma. Sodium and
potassium ions are distributed with the inverse concentration profiles across cell membranes. The total number of
millimoles of solute is equal in each of the three compartments. Cell membranes separate the intracellular and
interstitial compartments. Capillary walls separate the interstitial and plasma compartments. Materials that must be
exchanged between the different compartments must cross these barriers in order to reach the other side.
In all cases, the basic techniques of measuring body fluids consists of diluting an appropriate marker molecule
(Evan's blue, inulin, H2O) into the volume that you would like to measure, allowing it to mix thoroughly in the
compartment, and then measuring the concentration of the marker. The basic calculation is based on the equation
volume = (quantity/concentration). There are, however, several possible sources of error tin this method.These errors
include an inadequate mixing of the marker within the compartment, loss of the molecule marker by metabolism or
excretion, and leakage into other compartments. an ideal marker substance for these measurements has the
characteristics of going only into the compartment that is measured, is broken down or excreted very slowly
compared to mixing time, and is lost as a simple exponential function of time (therefore allowing the extrapolation
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Structural Biochemistry/Cell Signaling Pathways/Circulatory System
back to its initial concentration from the data. the plasma volume is measured using Evan's blue, which binds to
blood cells and plasma proteins. The interstitial volume is measured using molecules that equilibrate between the
plasma and the interstitial fluid, but that won't enter cells (inulin). Total body water is measured by deuterated or
tritiated H2O, and with subtraction an intracellular volume is measured.
Body fluid compartments are separated by layers composed of cells that are arranged side-by-side with one another.
The layer of cells that solutes and water traverse as they move between compartments are epithelia cells or
endothelia cells. Chemical species move across there cell walls driven by concentration gradients or pressure
gradients. These chemical species may traverse the capillary walls by either a transcellular pathway of through a
paracellular pathway, or even both. Most cells of the epithelial layer are polarized, meaning that the properties of the
cell membrane facing the interstitial fluid are different from the properties of the cell membrane of the very same
cells facing the lumen of the tube. Chemical species can cross the paracellular pathway if there is a driving force on
them and if they aren't too big. Passage through the transcellular pathway is more complex in that a transporter
molecule may be needed to facilitate diffusion across the cell membrane.
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Article Sources and Contributors
Article Sources and Contributors
Structural Biochemistry/Cell Signaling Pathways/Circulatory System Source: http://en.wikibooks.org/w/index.php?oldid=1988369 Contributors: A8shah, Adrignola, Asitangg,
CommonsDelinker, Dhalim, Eikim, Mlesaca, Rehwang, Rmhsu, 2 anonymous edits
Image Sources, Licenses and Contributors
Image:Circulatory System en.svg Source: http://en.wikibooks.org/w/index.php?title=File:Circulatory_System_en.svg License: Public Domain Contributors: User:LadyofHats
File:Illu_pulmonary_circuit.jpg Source: http://en.wikibooks.org/w/index.php?title=File:Illu_pulmonary_circuit.jpg License: Public Domain Contributors: Arcadian, Pieter Kuiper, 2
anonymous edits
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