copyright 2005 pearson education, inc. publishing as benjamin cummings ch.34 circulatory system

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Ch.34 Circulatory System


Essential knowledge 4.B.2:

• Cooperative interactions within organisms promote efficiency in the use of energy and matter.

– a. Organisms have areas or compartments that perform a subset of functions related to energy and matter, and these parts contribute to the whole.


Essential knowledge 4.A.4:

• Organisms exhibit complex properties due to interactions between their constituent parts.

– a. Interactions and coordination between organs provide essential biological activities.

– b. Interactions and coordination between systems provide essential biological activities.


Essential knowledge 2.C.1:

• Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes.– a. Negative feedback mechanisms maintain dynamic

homeostasis for a particular condition (variable) by regulating physiological processes, returning the changing condition back to its target set point.

– b. Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set-point. Amplification occurs when the stimulus is further activated which, in turn, initiates an additional response that produces system change.


Essential knowledge 2.D.2:

• Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments.

• a. Continuity of homeostatic mechanisms reflects common ancestry, while changes may occur in response to different environmental conditions.

• b. Organisms have various mechanisms for obtaining nutrients and eliminating wastes.

• c. Homeostatic control systems in species of microbes, plants and animals support common ancestry.


Essential knowledge 3.D.4:

• Changes in signal transduction pathways can alter cellular response.

– a. Conditions where signal transduction is blocked or defective can be deleterious, preventative or prophylactic.


Ch.34 Circulatory System• The circulatory system functions to:

– Transport O2 and nutrients to the cells

– Carry metabolic wastes to waste disposal organs

– Help maintain homeostasis

– Transport hormones

– Fight infections

•


• Diffusion can only transport chemicals over distances of a few cell widths, so a transport system is necessary to move substances and make them available to all cells of the body

• Capillaries are microscopic blood vessels forming an intricate network of blood vessels that are closely associated with all cells of the body

•


•

• Substances like oxygen diffuse out of the capillaries into the interstitial fluid that surrounds a cell, then from the interstitial fluid into the tissue cells, not directly from the capillary to the body cell


• Most complex animals have internal transport systems

– That circulates fluid, providing a lifeline between the aqueous environment of living cells and the exchange organs, such as lungs, that exchange chemicals with the outside environment


Invertebrate Circulation

• The wide range of invertebrate body size and form

–


Gastrovascular Cavities

• Simple animals, such as cnidarians and platyhelminthes have a body wall only a few cells thick that encloses an elaborately branched gastrovascular cavity

•

• This cavity has only one opening to the outside. A digestive cavity of this sort, with a single opening that functions as both mouth and anus, is called a gastrovascular cavity.


• Some cnidarians, such as jellies

– Have elaborate gastrovascular cavities


Open and Closed Circulatory Systems

• More complex animals

–

• Both of these types of systems have three basic components

– A circulatory fluid (blood)

– A set of tubes (blood vessels)

– A muscular pump (the heart)


Open vs. Closed Invertebrate Circulation• Two types of circulatory fluids:

–Blood - contained within blood vessels

–Hemolymph - flows into hemocoel

• Open Circulatory System

–Heart pumps hemolymph via vessels

–Vessels empty into tissue spaces

• Closed Circulatory System

–Heart pumps blood to capillaries

–Gases and materials diffuse to and from nearby cells

–


• In insects, other arthropods, and most molluscs, hemolymph bathes the organs directly in an open circulatory system


• In a closed circulatory system, found in most vertebrates, blood is confined to vessels and is distinct from the interstitial fluid


• Closed systems

– Are more efficient at transporting circulatory fluids to tissues and cells


Survey of Vertebrate Circulation

• Humans and other vertebrates have a closed circulatory system

– Often called the cardiovascular system

• Blood flows in a closed cardiovascular system

–


• Arteries carry blood to capillaries

– The sites of chemical exchange between the blood and interstitial fluid

•


Fishes

• A fish heart has two main chambers

– One ventricle and one atrium

• Blood pumped from the ventricle travels to the gills, where it picks up O2 and disposes of CO2

•


Amphibians

• Frogs and other amphibians

– Have a three-chambered heart, with two atria and one ventricle which allows some mixing of oxygen-rich and oxygen-poor blood

• The ventricle pumps blood into a forked artery

–


Reptiles

• Reptiles have double circulation

–

• Turtles, snakes, and lizards

– Have a three-chambered heart with a ventricle that is partially divided by a septum which keeps mixing of oxygen-rich and oxygen-poor blood to a minimum


Mammals and Birds

• In all mammals and birds

– The ventricle is completely divided into separate right and left chambers

• The left side of the heart pumps and receives only oxygen-rich blood

–


• A powerful four-chambered heart was an essential adaptation of the endothermic way of life characteristic of mammals and birds

• Endotherms have a high metabolic rate and require much oxygen

• A rapid and efficient system to deliver oxygen-rich blood is needed

•


• Double circulation in mammals depends on the anatomy and pumping cycle of the heart

• Double circulation involves two circuits or pathways:

– Pulmonary circuit which carries blood between the heart and the lungs

– Systemic circuit which carries blood between the heart and the rest of the body

•


Human Heart: Gross Anatomy

• Septum separates heart into left & right halves

• Each half has two chambers

– Upper two chambers are the atria

• Thin-walled

• Receive blood from circulation

– Lower two chambers are the ventricles

• Thick-walled

•


Mammalian Circulation: The Pathway

• Heart valves

– Dictate a one-way flow of blood through the heart


Human Heart: Valves

• Valves open and close to control blood flow through heart

– Atrioventricular valves

• Tricuspid

• Bicuspid

– Semilunar valves

• Pulmonary

• Aortic


Heart murmurs• Heart murmurs are abnormal sounds during your heartbeat

cycle — such as whooshing or swishing — made by turbulent blood in or near your heart. These sounds can be heard with a stethoscope. A normal heartbeat makes two sounds like "lubb-dupp" (sometimes described as "lub-DUP"), which are the sounds of your heart valves closing.

• Heart murmurs are most often caused by defective heart valves. A stenotic heart valve has a smaller-than-normal opening and can't open completely. A valve may also be unable to close completely. This leads to regurgitation, which is blood leaking backward through the valve when it should be closed.


Vascular Pathways

• Human cardiovascular system includes two major circular pathways:

– Pulmonary Circuit

• Takes oxygen-poor blood to the lungs and returns oxygen-rich blood back to the heart

– Systemic Circuit

•


Transport in Humans - Pulmonary Circuit

• Blood returning to heart from the body

–Enters right atrium

–Right atrium pumps through tricuspid valve to right ventricle

–


Pulmonary circuit

• Blood begins its flow with the right ventricle pumping blood through the pulmonary artery to the lungs

•

• Blood flows through pulmonary vein back to the left atrium of the heart


Systemic Circuit

• Blood returning to heart from lungs

– Enters left atrium

– Left atrium pumps through mitral valve to left ventricle

– Left ventricle pumps blood through aortic valve to the systemic circuit

•


Systemic circuit

•

• Blood travel through arteries that branch off the aorta

• Arteries branch into smaller arterioles, then into capillaries, where exchange of materials occur

• Blood leaves capillaries as they join to form venules

• Venules join to form veins, which join to form large veins called vena cavas


• Blood from the upper body and head is collected by the superior (anterior) vena cava

• Blood from the lower body is drained into the inferior (posterior) vena cava

•


Cardiac Cycle

• The heart contracts and relaxes

–

• The contraction, or pumping, phase of the cycle

– Is called systole

• The relaxation, or filling, phase of the cycle

– Is called diastole


• The heart rate, also called the pulse

– Is the number of beats per minute

• The cardiac output

–


Maintaining the Heart’s Rhythmic Beat

• Some cardiac muscle cells are self-excitable

– Meaning they contract without any signal from the nervous system


• A region of the heart called the sinoatrial (SA) node, or pacemaker sets the rate and timing at which all cardiac muscle cells contract (upper wall of right atrium)

•

• At the AV node, the impulses are delayed 0.1 sec to allow the atria to empty and the ventricles to fill, and then travel down the bundle of His (specialized muscle fibers that carry impulses to the tip of the ventricles), which branch into the Purkinje fibers that make the ventricles contract


• The impulses that travel during the cardiac cycle

–


• The pacemaker is influenced by nerves, hormones, body temperature, and exercise

• The brain exerts control on the heart rate by sending impulses to the AV node telling the pacemaker to speed up or slow down the heart

• The brain does not control the heart beat, it influences the heart rate

• The pacemaker does not control the heart beat, it coordinates the heart beat

•


• Physical principles govern blood circulation

• The same physical principles that govern the movement of water in plumbing systems

–


• All blood vessels

– Are built of similar tissues

– Have three similar layers


• Structural differences in arteries, veins, and capillaries

– Correlate with their different functions

• Arteries have thicker walls

–


• In the thinner-walled veins

– Blood flows back to the heart mainly as a result of muscle action


Blood Flow Velocity

• Physical laws governing the movement of fluids through pipes

–


• The velocity of blood flow varies in the circulatory system

– And is slowest in the capillary beds as a result of the high resistance and large total cross-sectional area


Blood Pressure

•

• Pressure is created by the beating of the heart, which causes the blood to be forced into the arteries faster than it can flow into the arterioles

• Pulse is the rhythmic stretching of the arteries caused by the pressure of the blood forced through arteries by the powerful contractions of the ventricles during systole


Blood Pressure

• Measured in mm Hg

• Blood velocity expressed in cm/sec

•

• Blood pressure and velocity both decline rapidly as blood enters the arterioles

• Drop in blood pressure results mainly from a resistance to blood flow caused by friction between blood and the walls of the arterioles


• Resistance is high because the numerous small blood vessels (arterioles) have a large amount of surface area

•

• Because of the decline in velocity and pressure in the arterioles, there is a steady, leisurely flow of blood in the capillaries

• This gentle flow allows the exchange of substances between blood and the interstitial fluid


• By the time the blood reaches the veins, its pressure has dropped to near zero

• Veins are sandwiched between skeletal muscles, and blood is pushed along by the contraction of the muscles

•


• Systolic pressure

– Is the pressure in the arteries during ventricular systole

– Is the highest pressure in the arteries

• Diastolic pressure

– Is the pressure in the arteries during diastole

–


Capillary Function

• Capillaries in major organs are usually filled to capacity, but in many other sites, the blood supply varies

• At any given time, only 5-10% of the body’s capillaries have blood flowing through them

• Blood supply in the heart and brain is constant

•


•

• In one mechanism

– Contraction of the smooth muscle layer in the wall of an arteriole constricts the vessel preventing blood flow into the capillaries


• In a second mechanism, precapillary sphincters control the flow of blood between arterioles and venules


• The critical exchange of substances between the blood and interstitial fluid takes place across the thin endothelial walls of the capillaries

•


• Exchange of materials between blood in capillaries and tissue fluids occur in three ways

1. Diffusion across cell membrane of endothelial cells of capillaries

2. Transport by vesicles through endocytosis and exocytosis across cell membrane

3.


• The difference between blood pressure and osmotic pressure

–


Capillary Exchange

• Capillaries very narrow – Tiny RBCs must go through single file

• Wall of capillaries very thin to facilitate diffusion of nutrients, gases and wastes

– Oxygen and nutrients exit a capillary near the arterial end

–


• Fluid reenters the circulation

– Directly at the venous end of the capillary bed and indirectly through the lymphatic system


Fluid Return by the Lymphatic System

• The lymphatic system

– Returns fluid to the body from the capillary beds

–


Blood: Homeostasis Functions

• Transports substances to and from capillaries for exchange with tissue fluid

• Guards against pathogen invasion

•

• Buffers body pH

• Maintain osmotic pressure

• Clots prevent blood/fluid loss


BLOOD

• Blood is a connective tissue with cells suspended in a liquid matrix (plasma)

•


Blood Composition and Function

• Blood consists of several kinds of cells

– Suspended in a liquid matrix called plasma

• The cellular elements

–


Plasma

•

• Among its many solutes are

– Inorganic salts

– Plasma proteins

– Organic nutrients

– Nitrogenous wastes

– Hormones

– Dissolved gases


Cellular Elements

• Suspended in blood plasma are two classes of cells

– Red blood cells, which transport oxygen

– White blood cells, which function in defense

• A third cellular element, platelets

–


Red Blood (Corpuscles) Cells• Small, biconcave disks

• Lack a nucleus and contain hemoglobin

– Hemoglobin contains

• Four globin protein chains

• Each associated with an iron-containing heme

•


Erythrocytes

• Red blood cells, or erythrocytes

– Are by far the most numerous blood cells (25 trillion)

– Transport oxygen throughout the body

– Lose nuclei and mitochondria at maturity and thus survive only 3-4 months

– Contain 250 million molecules of hemoglobin/red blood cell

–


Erythrocytes

• Formed in red bone marrow

• Are convenient method of packaging hemoglobin so osmotic balance will not be disrupted

•


White Blood Cells

• Most types larger than red blood cells

• Contain a nucleus and lack hemoglobin

• Important in inflammatory response

– Neutrophils enter tissue fluid and phagocytize foreign material

– Lymphocytes (T Cells) attack infected cells

–


Leukocytes• The blood contains five major types of white blood

cells, or leukocytes

– Monocytes, neutrophils, basophils, eosinophils, and lymphocytes, which function in defense by phagocytizing bacteria and debris or by producing antibodies

– Basophils secrete histamine which dilates blood vessels allowing other WBC’s to move into surrounding tissues (swelling, allergy)

– Lymphocytes are the key cell in immunity or defense against specific invaders, some by producing antibodies

–


• Leukocytes spend most of time outside circulatory system, moving through interstitial fluid, and are also found in the lymphatic system


Platelets

• Platelets (thrombocytes)

– Result from fragmentation of megakaryocytes

–

• Blood clot consists of:

– Platelets

– Red blood cells

– All entangled within fibrin threads


Blood Clotting

• When the endothelium of a blood vessel is damaged

– The clotting mechanism begins


• A cascade of complex reactions

– Converts fibrinogen to fibrin, forming a clot


Blood Clotting

• Platelets and injured tissues release clotting factor called prothrombin activator

• Prothrombin activator converts prothrombin to thrombin (requires calcium)

• Thrombin converts fibrinogen into fibrin

•


Stem Cells and the Replacement of Cellular Elements

• The cellular elements of blood wear out

– And are replaced constantly throughout a person’s life


• Erythrocytes, leukocytes, and platelets all develop from a common source

– A single population of cells called pluripotent stem cells in the red marrow of bones


Cardiovascular Disorders

• Hypertension - High blood pressure

• Atherosclerosis - Accumulation of fatty materials in inner linings of arteries

• Stroke - Cranial arteriole bursts or is blocked by an embolus

• Heart attack – (Myocardial infarction) Coronary artery becomes partially blocked

•


Cardiovascular Disease

• Cardiovascular diseases

– Are disorders of the heart and the blood vessels

–


• One type of cardiovascular disease, atherosclerosis

– Is caused by the buildup of cholesterol within arteries


• Hypertension, or high blood pressure

–

• A heart attack

– Is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries

• A stroke

– Is the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head

copyright 2005 pearson education, inc. publishing as benjamin cummings ch.34 circulatory system

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