Circulatory Systems Chapter 34. Circulatory Systems 2 Internal Transport in Animals The Problem: All...

Circulatory SystemsChapter 34

2Circulatory Systems

Internal Transport in Animals

The Problem:All animal cells need to acquire nutrients &

oxygen from the environment & give off carbon dioxide & other wastes to the environment.

How is this problem solved in different animals?Unicellular protists (Amoeba, Paramecium) - Use cell membrane to do these functions. - Have high surface area-to-volume ratio which allows sufficient materials to enter & exit

Small multicellular animals - May use exterior surface or branches of inside cavities (gastrovascular cavities) to do their exchanges Ex: Sea anemones & flatworms

3Aquatic OrganismsWithout a Circulatory System

4Circulatory Systems

Other Invertebrate Solutions

RoundwormsUse fluids in their body cavity as a means of transporting substances

5Circulatory Systems

Other Invertebrate Solutions

Echinoderms (Starfish)Also use fluids in their body cavity

6Circulatory Systems

Invertebrate Circulation

All other animals have a circulatory system in which a pumping heart moves a fluid into blood vessels.

Two types of circulatory fluids:Blood - which is always contained within blood vessels.

Hemolymph - blood analogue. It is a mixture of water, inorganic compounds & organic compounds. There are no blood cells.

- Hemolymph flows within a body cavity called a hemocoel.

7Circulatory SystemsOpen vs. Closed

Invertebrate CirculationOpen Circulatory System (Arthropods & most Mollusks)

Heart pumps hemolymph via vessels

Vessels empty into tissue spaces

Eventually hemolymph drains back to the heart

Grasshopper circulation (arthropod):

- Dorsal tubular heart pumps hemolymph into dorsal aorta which empties into hemocoel.

- When heart contracts, openings called ostia, are closed

- When heart relaxes, hemolymph is sucked back into heart by way of ostia.

- Hemolymph of insects is colorless due to lack of hemoglobin & it does NOT carry oxygen. Use

trachea.

8Open vs. Closed Circulatory Systems

9Circulatory SystemsOpen vs. Closed

Invertebrate Circulation

Closed Circulatory System

Found in segmented worms (annelids = earthworm) & molluscs like octopus & squid Heart pumps blood to system of blood vessels.

Valves prevent backwards flow of blood.

Blood is enclosed in either heart or blood vessels at all times.

Blood eventually reaches tiny capillaries where gases and materials diffuse to and from nearby cells

Veins return blood to heart for re-pumping

10Open vs. Closed Circulatory Systems

11Circulatory SystemsOpen vs. Closed

Invertebrate Circulation

Earthworms have red blood. Blood contains respiratory pigment, hemoglobin. Hemoglobin is dissolved in blood; not contained in cells There is no specialized gas exchange surface. Gas exchange takes place across the body wall, which must remain moist to function.

12Circulatory Systems

Transport in the Vertebrates

All vertebrates have a closed cardiovascular systemVertebrate heart:

Atria - chamber(s) of heart that receive blood from general circulation of body

Ventricles - chamber(s) of heart that pump blood out to the body through blood vessels

Vertebrate vessels: Arteries - Carry blood away from heart Arterioles – Small arteries whose diameters can change Capillaries - Exchange materials with body tissue fluid Venules - Small veins that lead back to veins Veins - Return blood to heart

13Transport in Birds and Mammals

14Circulatory Systems

Blood Vessels in the Vertebrates

•Arteries - Have thick walls. Have thick muscles in wall & elastic.

- Able to expand & contract to accommodate increased flow of blood after heart beats.

Capillaries

- Extremely narrow, microscopically small tubes

- Walls composed of only one layer of epithelial cells

- No cell is more than 60-80 m from a capillary

- Only about 5% of capillary beds are open at once

- Blood cells must pass through in single file

- Allow exchange of materials across their thin walls

15Transport in Birds and Mammals

16Circulatory Systems

Blood Vessels in the Vertebrates

•Venules - Collect blood from capillary beds

- Join to form veins Veins

- Walls of veins much thinner than in arteries

- Thinner muscle layer

- Have lower blood pressure than arteries

- Have valves which open towards the heart. These keep the blood from flowing backwards.

17Transport in Birds and Mammals

18Circulatory Systems

Comparison of Circulatory Pathways

Two types of circulatory paths are seen:Fish - Blood follows a one-circuit (single-loop)

pathway through the bodyHeart has a single atrium and single ventricle - Ventricle pumps blood to gills - Gas exchange occurs in gills - Blood returns to aorta which brings blood to body. Blood pressure is lower here.

- Veins return oxygen-poor blood to an enlarged chamber called the sinus venosus that leads to the atrium.

- Atrium pumps blood back to ventricle.

19Comparison of Circulatory Circuitsin Vertebrates

20Circulatory Systems

Comparison of Circulatory Pathways

All other vertebrates have a two-circuit (double-loop) pathway.

Heart pumps blood to two places:

•to the body tissues, called the systemic circuit.

•to the lungs, called the pulmonary circuit.

This double pumping system is an adaptation to breathing air on land.

21Comparison of Circulatory Circuitsin Vertebrates

22Circulatory Systems

Two-circuit Circulatory Pathways

Amphibians Two atria with a single ventricle Sinus venosus collects oxygen-poor, deoxygenated, blood & pumps it to right atrium.

Oxygen-rich, oxygenated, blood coming back from lungs passes to left atrium.

Both atria empty into single ventricle Oxygenated & deoxygenated blood is somewhat kept separate because O2 poor blood is pumped out of ventricle before O2 rich blood enters.

- Deoxygenated blood is pumped to lungs.

- Oxygenated blood is pumped to the body.

23Comparison of Circulatory Circuitsin Vertebrates

24Circulatory Systems

Two-circuit Circulatory Pathways

ReptilesA septum partially divides ventricle. Mixing of oxygen-poor & oxygen-rich blood is minimal

Crocodiles & alligators have a complete septum & thus have a true 4-chambered heart

25Comparison of Circulatory Circuitsin Vertebrates

26Circulatory Systems

Two-circuit Circulatory Pathways

Birds & MammalsA septum completely divides heart into left and right halves.

Right ventricle pumps blood to lungsLarger left ventricle pumps blood to rest of bodyThis provides good blood pressure in both the pulmonary and systemic circuits.

27Comparison of Circulatory Circuitsin Vertebrates

28Circulatory Systems

Transport in Humans

Human HeartFist-sized; cone-shapedMajor portion is called myocardium, and is composed of cardiac muscle.

- Muscle fibers are branched & tightly joinedHeart lies within a fluid-filled sac, the pericardium Inner surface of heart is lined with endocardium, composed of connective & epithelial tissue.

29External Heart Anatomy

30Circulatory SystemsHuman Heart:

Gross Anatomy

Septum separates heart into left & right halves

Each half has two chambersUpper two chambers are the atria­Thin-walled ­Wrinkled protruding appendages called auricles­Receive blood from rest of circulation

Lower two chambers are the ventricles­Thick-walled­Pump blood away from heart

31Internal View of the Heart

32Circulatory SystemsHuman Heart:

Valves

Valves open and close to direct blood flow through heart & prevent backward movement.Two atrioventricular valves: ­Tricuspid - between right atrium & right ventricle This valve has three flaps of tissue.­Bicuspid (mitral) - between left atrium & ventricle This valve has two flaps of tissue.

Two semilunar valves:­Pulmonary - between right ventricle & pulmonary trunk (artery)­Aortic - between left ventricle & aorta

33Internal View of the Heart

34Circulatory Systems

Transport in Humans

Blood returning to heart from systemic circuit Enters right atrium Right atrium pumps through tricuspid valve to right ventricle

Right ventricle pumps blood through pulmonary valve to the pulmonary circuit

Blood returning to heart from pulmonary circuit Enters left atrium Left atrium pumps through mitral valve to left ventricle Left ventricle pumps blood through aortic valve to the systemic circuit

Deoxygenated blood NEVER mixes with oxygenated blood (in humans)

35Circulatory Systems

Blood Flow Circuit in Humans

Right atrium tricuspid valve right ventricle pulmonary valve pulmonary artery capillaries around lung air sacs pulmonary veins left atrium bicuspid (mitral) valve left ventricle aortic valve aorta arteries to all parts of body capillaries in body tissues veins vena cava (superior or inferior) right atrium

Blue writing means deoxygenated bloodRed writing means oxygenated blood

36Circulatory Systems

Heartbeat & Cardiac Cycle

The average heart contracts, or beats, about 70 times a minute.

•Each heartbeat lasts about 0.85 seconds.Systole - Contraction of heart chambersDiastole - Relaxation of heart chambers

***See Cardiac Cycle Transparency here***

37Circulatory Systems

Cardiac Cycle

1. Atria contract (while ventricles relax)2. Ventricles contract (while atria relax)3. All the chambers rest

•The word systole, when used alone, refers to the left venticular systole.

- The volume of blood that is pumped out of left ventricle per minute is called the cardiac output.

- This is about 5.25 liters per minute; almost the amount of blood in the body.

- During exercise cardiac output can increase manyfold

38Circulatory Systems

Heart Sounds

When the heart beats a familiar “lub-dub” sound is heard. This is due to the valves of the heart closing.

•The longer & lower pitched “lub” is due to the atrioventricular valves closing.

•The shorter & sharper “dub” is due to the semilunar valves closing.

A heart murmur is a slight slush sound after the lub. It is often due to ineffective valves, which allows blood to flow backwards.

39Circulatory Systems

Conduction System of Heart

Rhythmic contraction of heart is due to its cardiac conduction system

Nodal tissue, which has both nervous & muscular characteristics, is located in two regions of heart:Sinoatrial node (SA), found in wall of right atrium, initiates the heartbeat & keeps it regular

- Every 0.85 seconds it sends out an excitation impulse which causes the atria to contract

- Thus, it is called the cardiac pacemaker.

40Conduction System of the Heart

41Circulatory Systems

Conduction System of Heart

•Atrioventricular node (AV), found in base of right atrium near septum, receives signal from SA node. - The AV node then signals the ventricles to

contract - It does this with the aid of special large fibers, called the bundle of His, which terminate in smaller Purkinje Fibers

- This allows both ventricles to contract simultaneously and very quickly.

Although the heartbeat is intrinsic it can be regulated by the nervous system to increase or decrease when necessary.

42Conduction System of the Heart

43Circulatory Systems

Conduction System of Heart

Electrocardiogram (ECG)A recording of electrical changes that occur in

myocardium during cardiac cycle When SA node triggers an impulse, the atrial fibers produce an electrical change called the P wave. This signals that the atria are about to contract.

The QRS complex signals that the ventricles are about to contract & the atria are relaxing.

The T wave is produced during the electrical changes that occur as the ventricles are recovering.

44Conduction System of the Heart

Ventricular fibrillation - caused by uncoordinated contraction of the ventricles. Most common cause of sudden cardiac death in seemingly healthy people.

45Circulatory Systems

Vascular Pathways

Human cardiovascular system includes two major circular pathways:Pulmonary Circuit­Takes deoxygenated blood to the lungs via pulmonary artery and returns oxygenated blood to the heart via the pulmonary veins. Only artery that carries deoxygenated blood & only vein that carries oxygenated blood.

Systemic Circuit­Takes blood throughout the body from the aorta to body & then back in the vena cava

46Path of Blood

47Circulatory Systems

Vascular Pathways

Coronary Arteries­Arise from aorta & come back to serve the heart.­Lie on exterior surface of heart & then branch into arterioles & capillaries.

Portal System­A blood vessel system that begins & ends in capillaries.

1. Hepatic Portal System – takes blood from intestines to liver without going back to

heart in between.

48Circulatory Systems

Blood Pressure

The beat of the heart supplies pressure that keeps blood moving in the arteriesSystolic Pressure results from blood being forced into the arteries during ventricular systole

Diastolic Pressure is the pressure in the arteries during ventricular diastole

Blood pressureNormally measured with a sphygmomanometer on the brachial artery in the upper arm.

Expressed in the form: Systolic “over” Diastolic - Normal blood pressure is 120/80 mmHg.

49Velocity and Blood Pressure

50Circulatory Systems

Blood Pressure

As blood flows from aorta into various arteries & arterioles, the blood pressure falls.

- The difference between systolic & diastolic gradually becomes less.

In capillaries there is a slow even flow of blood without systolic & diastolic differences.

Blood pressure in the veins is low & cannot move blood back to the heart from the limbs on its own.- Skeletal muscle contraction pushes blood in

the veins toward the heart with help of valves.

51Velocity and Blood Pressure

52Cross Section of a Valve in a Vein

53Circulatory Systems

Cardiovascular Disorders

Hypertension - High blood pressure. Can lead to stroke or heart attack.

Atherosclerosis - Accumulation of fatty materials, including cholesterol, in inner linings of arteries. These deposits are called plaque.

- This interferes with flow of blood. Can also lead to blood clots. Stationary clots are called

a thrombus. If clot dislodges & moves it is called an embolus.

54Circulatory Systems

Cardiovascular Disorders

Stroke - Cranial arteriole bursts or is blocked by an embolus. Lack of oxygen causes part of brain to die. Paralysis or death could result.

Heart attack – (Myocardial infarction) Due to coronary artery becoming completely blocked. Affected part of heart dies.

Angina pectoris –Due to partial blockage of coronary artery. Painful squeezing sensation from myocardial oxygen insufficiency.

55Circulatory Systems

Prevention of Cardiovascular Disease

Don’t:

- Smoke. Nicotine causes arteries to constrict & blood pressure to rise.

- Abuse drugs. Cocaine & amphetamines cause irregular heartbeats & can lead to heart

attacks & strokes.

- Drink too much alcohol. Can destroy just about any organ in body. 2-4 drinks a week might lower risk of heart disease.

- Gain too much weight. Heart has to work harder & blood pressure will rise.

56Circulatory Systems

Prevention of Cardiovascular Disease

Do: - Eat a healthy diet. Diet influences amount of

cholesterol. Two types plasma proteins “ferry” cholesterol:

HDL – “good” lipoprotein, transports cholesterol out of tissues to the liver.

LDL – “bad” lipoprotein, associated with high levels of plaque. Eating food high in saturated fats (red meat, cream, butter) & trans-fats (margarine, baked & fried foods) raises LDL. Eat more “healthy” fats: mono- & poly- unsaturated fats (canola oil, cold water fish)

Eat at least five servings of fruits & vegetables a day.

57Circulatory Systems

Prevention of Cardiovascular Disease

Do:

-Exercise regularly.

- Helps to keep weight under control, minimize stress, reduce hypertension.

58Circulatory SystemsBlood:

Homeostasis Functions

1. Transports gases, nutrients, wastes & hormones to and from capillaries for exchange

with tissue fluid

2. Helps to destroy pathogens

3. Distributes antibodies for immune system

4. Helps to regulate body temperature

5. Helps maintain water balance & pH

6. Carries platelets & factors to help clot blood

59Composition of Blood

60Circulatory Systems

Composition of Blood

4-6 liters of blood in normal human

Liquid part of blood is called plasma90% water10% is salts, nutrients, wastes & proteins Formed elements (cells) make up ~45% of bloodRed blood cells (erythrocytes)White blood cells (leucocytes)Platelets (thrombocytes)

61Circulatory Systems

Red Blood Cells (RBCs)

Small, biconcave disks that lack a nucleusMost numerous blood cells (approximately 25 trillion

in average adult). Contain hemoglobin, a respiratory pigment

Hemoglobin contains­Four globin protein chains­Each associated with an iron-containing heme which binds loosely with oxygen­Manufactured continuously in bone marrow of skull, ribs, vertebrae, and ends of long bones­Destroyed in liver & spleen after ~120 days.

Lack of RBCs or low hemoglobin leads to anemia

62Circulatory Systems

White Blood Cells (WBCs)

Usually larger than red blood cells & contain a nucleus. Lack hemoglobin.

Usually ~5-10,000 white cells per mL of blood

Important in inflammatory responseNeutrophils, macrophages & monocytes are phagocytes that eat foreign cells or materials

Lymphocytes play a role in fighting infection - T cells attack infected cells - B cells produce antibodies which combine with

foreign antigens (part of an invader)

63Circulatory Systems

White Blood Cells (WBCs)

Other white blood cells:Eosinophils release enzymes that fight parasites & destroy allergens (substances that start an allergic reaction)

Basophils contain the anticoagulant heparin which prevents blood clotting

- They also dilate blood vessels

64Circulatory Systems

Platelets (Thrombocytes)

Platelets result from fragmentation of large cells called megakaryocytes in the red bone marrow

Produce 200 billion a day.

Involved in blood clotting, coagulation12 clotting factors are involved in making a clot

Hemophilia - due to mutation in one clotting factorCan bleed into joints, muscles or the brain.

65Circulatory Systems

Coagulation of Blood

Steps involved:Platelets clump at site of vessel puncture. They partially seal the leak

Platelets & injured tissues release a clotting factor called prothrombin activator.

- Converts prothrombin to thrombin. Needs Ca2+. Thrombin acts as an enzyme that turns fibrinogen into long threads of fibrin.

- These threads wind around platelet plug and also trap red blood cells.

66Blood Clotting

67Circulatory Systems

Capillary Exchange

Two forces control movement of fluid through the capillary walls & allow exchange of materials:

1. Osmotic pressure •Tends to cause water to move from tissue fluid

to blood•Due to fact that blood has higher concentration of solutes than tissue fluid

2. Blood pressure•Tends to cause water to move from blood to tissue fluids

68Circulatory Systems

Capillary Exchange

At arterial end of capillary bed:•Blood pressure (~32 mmHg) exceeds osmotic

pressure (~22 mmHg) Water exits a capillary at this end.

In middle of capillary bed:•Osmotic pressure equals blood pressure Solutes move due to concentration gradients - Oxygen & nutrients move out of capillary into

surrounding tissues. - Carbon dioxide & wastes move back into

capillary from the surrounding tissues.

69Capillary Exchange

70Circulatory Systems

Capillary Exchange

At venule end of capillary bed:•Osmotic pressure (~22 mmHg) exceeds blood

pressure (~15 mmHg) Water enters a capillary at this end.

71Capillary Exchange

72Circulatory Systems

Capillary Closures

Not all capillary beds are open at the same time:•Capillary bed open when precapillary sphincters

(circular muscles) are relaxed. •Capillary bed closed when the sphincters are

contracted Then blood flows through a shunt directly from

arteriole into a venule.

73Capillary Bed