The Circulatory System

The Heart, Blood Vessels, Blood Types

The Closed Circulatory System

•Humans have a closed circulatory system, typical of all vertebrates, in which blood is confined to vessels and is distinct from the interstitial fluid.

–The heart pumps blood into large vessels that branch into smaller ones leading into the organs.

–Materials are exchanged by diffusion between the blood and the interstitial fluid bathing the cells.

The Cardiovascular System

•Three Major Elements –Heart, Blood Vessels, & Blood

–1. The Heart- cardiac

muscle tissue

–highly interconnected cells

–four chambers

•Right atrium

•Right ventricle

•Left atrium

•Left ventricle

Pathway of the blood•Superior Vena Cava

•Right Atrium

•Tricuspid Valve

•Right Ventricle

•Pulmonary Semilunar Valve

•Lungs

•Pulmonary Vein

•Bicuspid Valve

•Left Ventricle

•Aortic Semilunar Valve

•Aorta

•To the bodies organs & cells

Circuits

•Pulmonary circuit

–The blood pathway between the right side of the heart, to the lungs, and back to the left side of the heart.

•Systemic circuit

–The pathway between the left and right sides of the heart.

The Cardiovascular System2. Blood Vessels -A network of tubes

–Arteriesarterioles move away from the heart

•Elastic Fibers

•Circular Smooth Muscle

–Capillaries – where gas exchange takes place.

•One cell thick

•Serves the Respiratory System

–VeinsVenules moves towards the heart

•Skeletal Muscles contract to force blood back from legs

•One way valves

•When they break - varicose veins form

• Some tissues do not have capillaries; these are

the epidermis, cartilage, and the lens and

cornea of the eye.

• Most tissues, however, have extensive capillary networks.

• The qtty/volume of capillary =metabolic activity of the organ.

• The functioning of the kidneys, for example, depends upon a good blood supply=more capillaries

• Achilles tendon at the heel is less metabolically active

= fewer capillaries

• Blood flow into capillary networks is regulated by smooth muscle cells called precapillary sphincters, found at the beginning of each network.

• Precapillary sphincters are not regulated by the nervous system but rather constrict or dilate depending on the needs of the tissues.

• In an active tissue that requires more oxygen, such as exercising muscle, the precapillary sphincters dilate to increase blood flow.

• Some organs have another type of capillary called sinusoids, which are larger and more permeable than other capillaries.

• The permeability of sinusoids permits large substances such as proteins and blood cells to enter or leave the blood.

• Sinusoids are found in

red bone marrow

spleen

liver and pituitary gland

HYDROSTATIC PRESSURE VRS COLLOID OSMOTIC PRESSURE

OTHER TYPES OF CIRCULATION

• Hepatic portal circulation - subdivision of systemic circulation in which blood from the abdominal digestive organs and spleen circulates through the liver before returning to the heart.

• Blood from the capillaries of the stomach, small intestine, colon, pancreas, and spleen flows into two large veins, the superior mesenteric vein and the splenic vein, which unite to form the portal vein

• The portal vein takes blood into the liver, where it branches extensively and empties blood into

the sinusoids, the capillaries of the liver

• From the sinusoids, blood flows into hepatic

• veins, to the inferior vena cava

• Glucose

• Alcohol

• TOXINS/POTENTIAL POISONS

Are removed before blood gets to the heart and kidney (rest of body organs)

OTHER TYPES OF CIRCULATION

• Fetal circulation involves pathways that are

present only before birth

OTHER TYPES OF CIRCULATION (cont. )

The Cardiovascular System

3. The Blood

A. Plasma

Liquid portion of the blood.

Contains clotting factors, hormones, antibodies, dissolved gases, nutrients and waste

The Cardiovascular System

•The Blood

B. Erythrocytes - Red Blood Cells

–Carry hemoglobin and oxygen. Do not have a nucleus and live only about 120 days.

–Can not repair themselves.

The Cardiovascular System

•The Blood

C. Leukocytes – White Blood cells

–Fight infection and are formed in the bone marrow

–Five types – neutrophils, lymphocytes, eosinophils, basophils, and monocytes.

The Cardiovascular SystemThe Blood

•D. Thrombocytes –Platelets.

–These are cell fragment that are formed in the bone marrow from magakaryocytes.

–Clot Blood by sticking together – via protein fibers called fibrin.

Disorders of the Circulatory System

• Anemia - lack of iron in the blood, low RBC count

• Leukemia - white blood cells proliferate wildly, causing anemia

• Hemophilia - bleeder’s disease, due to lack of fibrinogen in thrombocytes

• Heart Murmur - abnormal heart beat, caused by valve problems

• Heart attack - blood vessels around the heart become blocked with plaque, also called myocardial infarction

Unit 9 – The Heart

Cardiovascular System

The Heart

Functions of the Heart

• Generating blood pressure

• Routing blood– Heart separates pulmonary and systemic

circulations

• Ensuring one-way blood flow– Heart valves ensure one-way flow

• Regulating blood supply– Changes in contraction rate and force match

blood delivery to changing metabolic needs

Size, Shape, Location

of the Heart

•Size of a closed fist

•Shape–Apex: Blunt rounded point of cone

–Base: Flat part at opposite of end of cone

•Located in thoracic cavity in mediastinum

Heart Cross Section

Pericardium

Heart Wall

• Three layers of tissue

– Epicardium: This serous membrane of smooth outer surface of heart

– Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting

– Endocardium: Smooth inner surface of heart chambers

Heart Wall

External Anatomy

•Four chambers–2 atria

–2 ventricles

•Auricles

•Major veins–Superior vena cava

–Pulmonary veins

•Major arteries–Aorta

–Pulmonary trunk

Coronary Circulation

Heart Valves

•Atrioventricular

–Tricuspid

–Bicuspid or mitral

•Semilunar

–Aortic

–Pulmonary

•Prevent blood from flowing back

Heart Valves

Function of the Heart Valves

Blood Flow Through Heart

Systemic and Pulmonary

Circulation

Heart Skeleton

•Consists of plate of fibrous connective tissue between atria and ventricles

•Fibrous rings around valves to support

•Serves as electrical insulation between atria and ventricles

•Provides site for muscle attachment

Cardiac Muscle

• Elongated, branching cells containing 1-2 centrally located nuclei

• Contains actin and myosin myofilaments

• Intercalated disks: Specialized cell-cell contacts

• Desmosomes hold cells together and gap junctions allow action potentials

• Electrically, cardiac muscle behaves as single unit

Conducting System of Heart

Electrical Properties

• Resting membrane potential (RMP) present

• Action potentials

– Rapid depolarization followed by rapid, partial early repolarization. Prolonged period of slow repolarization which is plateau phase and a rapid final repolarization phase

– Voltage-gated channels

Refractory Period

• Absolute: Cardiac muscle cell completely insensitive to further stimulation

• Relative: Cell exhibits reduced sensitivity to additional stimulation

• Long refractory period prevents tetanic contractions

Electrocardiogram

• Action potentials through myocardium during cardiac cycle produces electric currents than can be measured

• Pattern

– P wave

• Atria depolarization

– QRS complex

• Ventricle depolarization

• Atria repolarization

– T wave:

• Ventricle repolarization

Cardiac Arrhythmias

• Tachycardia: Heart rate in excess of 100bpm

• Bradycardia: Heart rate less than 60 bpm

• Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration

• Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people

Cardiac Cycle

• Heart is two pumps that work together, right and left half

• Repetitive contraction (systole) and relaxation (diastole) of heart chambers

• Blood moves through circulatory system from areas of higher to lower pressure.

– Contraction of heart produces the pressure

Heart Sounds

• First heart sound or “lubb”– Atrioventricular valves and surrounding fluid

vibrations as valves close at beginning of ventricular systole

• Second heart sound or “dupp”– Results from closure of aortic and pulmonary

semilunar valves at beginning of ventricular diastole, lasts longer

• Third heart sound (occasional)

– Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

Location of Heart Valves

Mean Arterial Pressure (MAP)

• Average blood pressure in aorta

• MAP=CO x PR– CO is amount of blood pumped by heart

per minute• CO=SV x HR

– SV: Stroke volume of blood pumped during each heart beat

– HR: Heart rate or number of times heart beats per minute

• Cardiac reserve: Difference between CO at rest and maximum CO

– PR is total resistance against which blood must be pumped

Regulation of the Heart

• Intrinsic regulation: Results from normal functional characteristics, not on neural or hormonal regulation– Starling’s law of the heart

• Extrinsic regulation: Involves neural and hormonal control– Parasympathetic stimulation

• Supplied by vagus nerve, decreases heart rate, acetylcholine secreted

– Sympathetic stimulation• Supplied by cardiac nerves, increases heart rate and force of

contraction, epinephrine and norepinephrine released

Heart Homeostasis

• Effect of blood pressure

– Baroreceptors monitor blood pressure

• Effect of pH, carbon dioxide, oxygen

– Chemoreceptors monitor

• Effect of extracellular ion concentration

– Increase or decrease in extracellular K+ decreases heart rate

• Effect of body temperature

– Heart rate increases when body temperature increases, heart rate decreases when body temperature decreases

Baroreceptor and Chemoreceptor

Reflexes

Effects of Aging on the Heart

• Gradual changes in heart function, minor under resting condition, more significant during exercise

• Hypertrophy of left ventricle

• Maximum heart rate decreases

• Increased tendency for valves to function abnormally and arrhythmias to occur

• Increased oxygen consumption required to pump same amount of blood

ACIDS

• Physiologically important acids include:

–Carbonic acid (H2CO3)

–Phosphoric acid (H3PO4)

–Pyruvic acid (C3H4O3)

–Lactic acid (C3H6O3)

• These acids are dissolved in body fluids

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Lactic acid

Pyruvic acid

Phosphoric acid

BASES

• Physiologically important bases include:

–Bicarbonate (HCO3- )

–Biphosphate (HPO4-2 )

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Biphosphate

BUFFERS

• Buffering systems provide an immediate response to fluctuations in pH

–1) Phosphate

–2) Protein

–3) Bicarbonate Buffer System

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PHOSPHATE BUFFER SYSTEM

• 1) Phosphate buffer system

Na2HPO4 + H+ NaH2PO4 + Na+

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H+ Na2HPO4+

NaH2PO4Click to animate

Na++

PHOSPHATE BUFFER SYSTEM

Na2HPO4 + H+ NaH2PO4 + Na+

• Alternately switches Na+ with H+

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H+ Na2HPO4+

NaH2PO4Click to animate

Na++

Disodium hydrogen phosphate

PROTEIN BUFFER SYSTEM• 2) Protein Buffer System

–Behaves as a buffer in both plasma and cells

–Hemoglobin is by far the most important protein buffer

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PROTEIN BUFFER SYSTEM

• The most plentiful buffer of the body

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BICARBONATE BUFFER SYSTEM

• 3) Bicarbonate Buffer System

HCO3- + added H+

H2CO3

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HCO3-

H2CO3

BICARBONATE BUFFER SYSTEM

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Loss of HCl

Addition of lactic acid

H+ HCO3-H2CO3H2OCO2 + +

Exercise

Vomiting

IMMUNITY

•CELLS: LYMPHOCYTES, MACROPHAGES, PLASMA

CELLS, NK CELLS

•CYTOKINES/CHEMOKINES

•PLASMA PROTEINS:Complement, Coagulation Factors