Deep Water Circulation Also known as thermohaline circulation.
Circulation
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Transcript of Circulation
Circulation
Chapter 32 Pages 617-639
Major Features and Functions of Circulatory Systems
Circulatory systems evolved to bring the outside world to each cell in a multicellular organism The earliest cells were nurtured by the primordial sea
in which they evolved In complex organisms, individual cells are farther
away from the outside world, but require diffusion for adequate nutrients and to ensure they aren’t poisoned by their own waste
With the evolution of the circulatory system, a sort of “internal sea” was created, which transports food and oxygen close to each cell and carries away wastes
All circulatory systems have three major parts
A pump, the heart, that circulating
Blood – liquid that serves as a medium of transport
A system of tubes, blood vessels, to conduct the blood throughout the body
Two types of circulatory systems
Open circulatory systems - invertebrates, including arthropods and mollusks
One or more simple hearts, network of vessels, and series of interconnected spaces within the body called a hemocoel
Tissues and organs in the hemocoel are directly bathed by hemolymph - acts as both blood and the extracellular fluid that bathes all cells
Insect Example Heart is a modified blood
vessel with a series of contracting chambers
When chambers contract, valves in the heart are pressed shut, forcing the hemolymph out through vessels and into hemocoel spaces throughout the body
When the chambers relax, blood is drawn back into them from the hemocoel
Animation: Open Circulatory Systems
Closed Circulatory Systems Invertebrates - earthworm and
active mollusks (squid and octopuses) and all vertebrates Blood is confined to heart
and blood vessels, which branch throughout the organs and tissues of the body more rapid blood flow more efficient transport of
dissolved substances higher blood pressure than in
open systems
Animation: Closed Circulatory Systems
Functions of Vertebrate Circulatory System
Transport O2 from lungs or gills to tissues
Transport CO2 from tissues to lungs or gills
Distribution of nutrients from the digestive system to
body cells
Transport of wastes and toxic substances to the liver, where they are detoxified, and to the kidneys for excretion
Distribution of hormones from the glands and organs to the tissues
Regulation of body temperature by adjustments in blood flow
Wound healing and blood clotting to prevent blood loss
Protection against disease by circulating white blood cells and antibodies
Vertebrate Heart
The vertebrate heart consists of muscular chambers capable of strong contractions
Chambers called atria collect blood
Atrial contractions send blood into ventricles,
chambers whose contractions circulate blood through the lungs and to the rest of the body
Evolution of the Vertebrate Heart
Increasingly complex and efficient hearts The heart has become increasingly complex
Separation of oxygenated and deoxygenated blood
Fish (first vertebrates to evolve) has two chambers: a single atrium that empties into a single ventricle Blood from the ventricle passes first through the gills,
where it picks up O2 and gives off CO2 Blood then travels from the gills through the rest of the
body, picking up CO2 and returning it to the single atrium
(a) Fish
gill capillaries
body capillaries
ventricle
atrium
Fish Heart
Animation: Two-Chambered Hearts
Three Chambered Hearts
Fish gave rise to amphibians and amphibians to reptiles Three-chambered hearts consist of two atria and one
ventricle Amphibians, snakes, lizards, and turtles Deoxygenated blood from the body is delivered to the right
atrium, blood from the lungs enters the left atrium Both atria empty into the single ventricle Although some mixing occurs, deoxygenated blood remains
in the right portion of the ventricle and is pumped into vessels that lead to the lungs, while most of the oxygenated blood remains in the left portion of the ventricle and is pumped to the rest of the body
(b) Amphibians and somereptiles
lung capillaries
atria
ventricle
body capillaries
Three Chambered Heart
Animation: Three-Chambered Hearts
Four Chambered Hearts
Some reptiles - crocodiles, birds, and mammals have separate right and left ventricles
Completely isolate oxygenated and deoxygenated blood
(c) Mammals, crocodiles,and birds
lung capillaries
body capillaries
atria
ventricles
Four Chambered Heart
Four Chambers – Two Pumps An atrium collects the blood before passing it to a
ventricle which propels it into the body
One pump, the right atrium and ventricle, deals with deoxygenated blood Oxygen-depleted blood enters the right atrium through
two large veins - the superior and inferior vena cava After filling with blood, the right atrium contracts,
forcing blood into the right ventricle Contraction of the right ventricle sends the oxygen-
depleted blood to the lungs through the pulmonary arteries
Two Pumps, part II
The second pump, the left atrium and ventricle, deals with oxygenated blood Oxygen-rich blood from the lungs enters the left
atrium through the pulmonary veins and is squeezed into the left ventricle
Contraction of the left ventricle sends the oxygenated blood through the aorta to the rest of the body
Heart Valves
Maintain the direction of blood flow When the ventricles contract, blood must be prevented from
flowing back into the atria Blood entering the arteries must also be prevented from
flowing back into the ventricles as the heart relaxes Pressure in one direction opens valves easily, but reverse
pressure forces valves closed Atrioventricular valves blood flows from atria into the
ventricles Semilunar valves blood enters the pulmonary artery and
aorta when ventricles contract, but prevent blood from returning as the ventricles relax
aorta
left atrium
pulmonary artery(to left lung)
semilunar valves
pulmonary veins(from left lung)
atrioventricular valve
left ventricle
thicker muscleof left ventricle
descending aorta(to lower body)
rightventricle
inferiorvena cava
atrioventricular valve
superiorvena cava
pulmonary artery(to right lung)
pulmonary veins(from right lung)
rightatrium
The Human Heart
Animation: The Human Cardiovascular System
Cardiac Muscle Cells
Cardiac muscle cells are small, branched, and striated Linked to one another via intercalated discs, appear as
bands between the cells
Adjacent cell membranes are attached to one another by desmosomes, prevent heart contractions from pulling muscle cells apart
Intercalated discs also contain gap junctions to allow the electrical signals that trigger contractions to spread from one muscle cell to another, producing synchronous heart muscle contractions
The Structure of Cardiac Muscle cell nucleus
Intercalated discscontaining desmosomesand gap junctions link adjacent cardiac musclecells
Cardiac Cycle
The coordinated contractions of atria and ventricles produce the cardiac cycle
The heart beats in a coordinated fashion Both atria contract and pump blood into the ventricles Both ventricles contract and pump blood into the
arteries that exit the heart All chambers relax briefly before the cycle repeats
This cardiac cycle lasts less than 1 second Cardiac Cycle
The Cardiac Cycle
Atria contract, forcingblood into the ventricles
Then the ventriclescontract, forcing bloodthrough the arteries tothe lungs and the restof the body
The cycle ends asthe heart relaxes
Deoxygenated blood ispumped to the lungs
Blood fills theatria and beginsto flow passivelyinto the ventricles
Deoxygenatedblood from thebody enters theright ventricle
Oxygenated blood from thelungs enters the left ventricle
Oxygenated bloodis pumped to thebody
321
Blood Pressure
The cardiac cycle generates the forces that are measured when blood pressure is taken
Systolic pressure, the higher of the two readings, is measured during ventricular contraction
Diastolic pressure is the minimum pressure in the arteries as the heart rests between contractions
A BP reading of less than 120/80 is healthy; higher than 140/90 is defined as high
High blood pressure, or hypertension, is caused by the constriction of small arteries, which causes resistance to blood flow and strain on the heart
Animation: Blood Pressure
Electrical Impulses Coordinate the Contractions The contraction of the heart is initiated and coordinated by a
pacemaker, a cluster of specialized muscle cells that produce spontaneous electrical signals at a regular rate
The heart’s pacemaker is the sinoatrial (SA) node, located in the upper wall of the right atrium
Electrical signals from the SA node pass freely into the connecting cardiac muscle cells and then throughout the atria
The electrical signal then passes from the right atrium to a specialized group of muscle cells between the right atrium and right ventricle called the atrioventricular (AV) node
The signal to contract spreads along specialized tracts of rapidly conducting muscle fibers called the atrioventricular bundle, which sends branches to the lower portion of both ventricles
Here, the bundles branch further, forming Purkinje fibers that transmit the electrical signal throughout the ventricle
Inexcitable tissueseparates the atria and ventriclesAV node
SA node
AV bundle
AV bundlebranches
An electrical signalfrom the sinoatrial (SA)node starts atrialcontraction
1
The signal entersthe atrioventricular(AV) node, whichtransmits it to theAV bundle with aslight delay
3
The signal travelsthrough the AV bundlebranches to the baseof the ventricles
4
Purkinje fibers transmitthe signal to ventricularcardiac muscle cells,causing contraction fromthe base upwards
5
The electricalsignal spreadsthrough the atria,causing them tocontract
2
Purkinjefibers
The Pacemaker and Its Connections
Disorders
When the pacemaker fails, rapid, uncoordinated, weak contractions called fibrillation may occur
Treated with a defibrillating machine, which applies a
jolt of electricity, synchronizing the contractions of the ventricular muscle cells, and the pacemaker resumes its normal coordinating function
Heart Rate
Influenced by nervous system and hormones On its own, the SA node pacemaker maintains a heart
rate of 100 beats per minute
Nerve impulses and hormones alter the heart rate At rest, the parasympathetic nervous system slows
the heart rate to about 70 beats per minute During exercise and stress, the sympathetic
nervous system increases the heart rate to meet the demand for greater blood flow to the muscles
What Is Blood?
Blood has two major components
A liquid or plasma, 55% of total volume
The cellular portion, 40–45% of total volume Red blood cells White blood cells Platelets
platelets
megakaryocyte
neutrophil neutrophil
basophil
monocyte
eosinophil
lymphocyte
red blood cells
(a) Erythrocytes (red blood cells)
(b) Leukocytes (white blood cells) (c) Megakaryocyte forming platelets
Types of Blood Cells
Plasma
Water with proteins, salts, nutrients, and wastes
90% water, > 100 different molecules - hormones, nutrients, cellular wastes, ions
Proteins are the most abundant dissolved molecules by weight and include: Albumin, maintains the blood’s osmotic strength Globulins, antibodies - important in immune
response Fibrinogen, important in blood clotting
Cellular Components of Blood
Formed in bone marrow Of the 3 cell-based components - only the white blood
cells are complete, functional cells Mature RBCs are not cells because they lack a
nucleus, which is lost during development Platelets are small fragments of cells
All 3 components originate from blood stem cells or megakaryocytes Stem cells are unspecialized cells that can divide to
produce one or more types of specialized cells
Red Blood Cells
Carry oxygen from the lungs to the tissues 99% of all blood cells, and 45% total volume Oxygen-carrying red blood cells or erythrocytes Red color of erythrocytes is caused by the protein
hemoglobin, each binds to 4 oxygen molecules, one on each iron-containing heme group Oxygenated hemoglobin is bright cherry-red color Hemoglobin becomes bluish as it releases O2 and
picks up CO2 at tissues
Hemoglobin
Red Blood Cells Life span of 4 months,
replaced by new cells from bone marrow
Macrophages (white blood cells) in spleen and liver engulf and break down dead red blood cells
Iron from erythrocytes is returned to the bone marrow and recycled into new red blood cells
Regulated by Negative Feedback
Red blood cell count is maintained by a negative feedback system involving hormone erythropoietin Erythropoietin is produced by the kidneys and
released into the blood in response to O2 deficiency Stimulates rapid production of new RBC by bone
marrow When the 02 level is restored, erythropoietin
production declines and rate of RBC production returns to normal
Oxygen deficiency
Erythropoietinproduction
by the kidneys
Red bloodcell production
in the bone marrow
Restored oxygen level
inhibits
stimulates
causes
stimulates
Red Blood Cell Regulation
White Blood Cells
Defend the body against disease Five types of white blood cells or leukocytes
Neutrophils Eosinophils Basophils Lymphocytes Monocytes
WBC Details
Cell life spans range from hours to years
<1% of the cellular portion of blood
All WBC help to protect the body against disease
Monocytes, enter tissues and transform into macrophages that engulf bacteria and cellular debris
Platelets
Cell fragments that aid in blood clotting
Megakaryocyte pieces, reside in bone marrow Megakaryocytes pinch off
membrane-enclosed pieces of cytoplasm to form platelets, which enter the blood
Platelets survive 10 days
How it works…
Blood clotting plugs damaged blood vessels Complex process that plugs damaged blood vessels and
protects excessive blood loss
Clotting begins following a break in a blood vessel wall, exposing collagen fibers that attract platelets, which form a platelet plug
The platelets and ruptured cells release chemicals that initiate a series of reactions, producing the enzyme thrombin from its inactive form, prothrombin
Blood Clotting
collagenfibers
prothrombin fibrinogenthrombin
thrombinredbloodcells
bloodvessel
plateletsplateletplug
fibrin
Damaged cells exposecollagen, which activatesplatelets, causing them tostick and form a plug
1 Both damaged cellsand activated plateletsrelease chemicals thatconvert prothrombininto the enzyme thrombin
2 Thrombin catalyzes theconversion of fibrinogeninto protein fibers calledfibrin, which forms ameshwork around theplatelets and traps redblood cells
3
Functions of Blood Vessels
Arteries to arterioles to capillaries, then into venules, to veins, blood returns to the heart
Except for capillaries, blood vessels have three
cellular layers Lined with endothelial cells The second layer is smooth muscle cells The outermost layer is connective tissue
precapillarysphincter
arteriole
venule
veinartery
capillary
to heartfrom heart
endotheliumvalve
smooth muscleconnective tissue
capillary networkwithin body tissues
Structures of Blood Vessels
jugular vein
aorta
superiorvena cava
carotid artery
lung capillariespulmonary artery
heart
kidney
femoral vein
intestine
inferiorvena cava
liver
femoral artery
The Human Circulatory System
Arteries and Arterioles
Arteries and arterioles carry blood away from the heart The walls are thicker and more elastic than veins With each heart beat, the arteries expand slightly,
like thick-walled balloons Arteries branch into smaller diameter vessels
called arterioles, which play a major role in determining how blood is distributed in the body
Capillaries
Exchange of nutrients and wastes Arterioles conduct blood into networks of capillaries,
microscopically thin vessels Capillaries allow individual body cells to exchange
nutrients and wastes with the blood by diffusion So numerous that most of the body’s cells are no
more than 100 μm from a capillary, close enough for diffusion
Capillaries are so narrow that red blood cells pass through them single file
Red blood cells mustpass through capillariesin single file
Capillary walls are thinand permeable to gases,nutrients, and cellularwastes
Red Blood Cells Travel Through a Capillary
Leaky Blood Vessels
Blood pressure within capillaries causes fluid to leak into the space surrounding the capillaries
Resulting in extracellular fluid, resembles plasma without the proteins Primarily water containing dissolved nutrients,
hormones, gases, cellular waste, and WBC This fluid provides body cells with nutrients and
accepts their wastes
How to Diffuse thru Capillaries
Gases, water, lipid-soluble hormones and fatty acids diffuse through the endothelial cell membranes
Small water-soluble nutrients, (salts, glucose, and amino acids) enter the extracellular fluid through narrow spaces between adjacent capillary cells
Some proteins are carried across the endothelial
cell membrane as vesicles
Osmotic Pressure and Capillaries
Pressure within the capillaries drops as blood travels toward the venules, and the high osmotic pressure of the blood that remains inside the capillaries draws water back into the vessels by osmosis as blood approaches the venous side of the capillaries
As water enters the capillaries (diluting the blood), dissolved substances in the extracellular fluid tend to diffuse back into the capillaries
Thus, most of the extracellular fluid is restored to the blood through the capillary walls on the venous side of the capillary network
Veins and Venules
Carry blood to the heart
After picking up CO2 and wastes from cells, capillary blood drains into larger vessels, called venules, which empty into larger veins Walls of veins are thinner, less muscular, and more
expandable than arteries When veins are compressed, one-way valves keep
blood flowing toward the heart
valveclosed
valveclosed
valveopen
relaxedmuscle
muscle contractioncompresses vein
Valves Direct Blood Flow in Veins
Moving Blood thru Veins
Pressure changes in the body caused by breathing, as well as contractions of skeletal muscle during exercise, help return blood to the heart by squeezing the veins and forcing blood through them
Prolonged sitting or standing can cause swollen ankles, without muscle contractions to compress the veins, venous blood pools in the lower legs
Varicose veins may result from permanently swollen veins in the lower leg as a result of stretched and weakened vein valves
Controlling Blood Flow
Arterioles carry blood to capillaries; their muscular walls are influenced by nerves, hormones and chemicals
Arterioles contract and relax in response to the needs of the tissues and organs they supply
Examples of Arteriole Control
In cold weather, fingers and toes can become frostbitten because arterioles that supply blood to the extremities constrict Blood is shunted to vital organs (heart and brain)
which cannot function at low temperatures
On a hot summer day, arterioles in the skin expand to bring more blood to the skin capillaries, so excess heat is dissipated to the air outside
Precapillary Spincters
Blood flow to capillaries is further regulated by tiny rings of smooth muscle called precapillary sphincters
They surround junctions between arterioles and capillaries
Open and close in response to local chemical changes that signal the needs of nearby tissues
The Lymphatic System Includes organs and a system of lymphatic vessels,
feeds into the circulatory system Return excess extracellular fluid to the bloodstream
Transport fats from the small intestine to the bloodstream
Filter old blood cells and other debris from the blood
Defend the body by exposing bacteria and viruses to
white blood cells
thymus
superiorvena cava
spleen
bonemarrow
thoracicduct
lymph vessels
lymph nodes
The thoracic ductenters a vein thatleads to the superiorvena cava
The Human Lymphatic System
Lymphatic Vessels
Lymphatic capillaries resemble blood capillaries that branch throughout the body.
Their walls are only one cell thick, but they are more permeable than blood capillaries
Unlike blood capillaries (form continuous interconnected network) lymphatic capillaries “dead-end” in the extracellular fluid surrounding body cells
Lymph Capillary Structure
lymphcapillary
extracellularfluid
Pressure forces fluid from the plasmaat the arteriole end of the capillary network
Extracellular fluid enters lymph vessels and the venous endsof capillaries
Lymph is transported into larger lymph vessels and back to the bloodstream
arteriole
capillary venule
1
2
3
Lymph
From the lymphatic capillaries, the lymph lymphatic vessels increasingly large lymphatic vessels Vessels resemble veins -
similar walls and one-way valves that control the direction of flow
Flow of lymph is regulated by internal pressures from breathing and muscle contraction
Elephantiasis Results from Blocked Lymphatic Vessels
Transporting Fat from Small Intestine
The small intestine is supplied with lymph capillaries called lacteals
After absorbing digested fats, intestinal cells release fat-transporting particles into the extracellular fluid
These particles are too large to diffuse into blood capillaries, but can move through the openings in lymphatic capillary walls
They are eventually released into the venous blood along with the lymph
Defend Body and Filter Blood
Tonsils, thymus, spleen, and hundreds of lymph nodes located along lymphatic vessels
Spleen, located between the stomach and diaphragm and supplied by vessels of both the lymphatic and circulatory systems, filters the blood It has a porous interior that is lined with white blood
cells, which engulf old red blood cells and platelets, fragments of dead cells, and foreign matter