CIRCULATORY SYSTEM

FUNCTIONS OF CIRCULATORY SYSTEM

1. Transport of Nutrients to all body parts* Glucose, amino acids, lipids, inorganic salts and water

2. Transport of Oxygen & Carbon Dioxide* Carried as free dissolve in Plasma* Hemoglobin (RBC)

3. Transport of Hormones

4. Transport of Excretory Products*Urea, uric acid, creatines , and wastes from Liver

5. Fight against Infections and Toxins* WBC’s of Blood * Monocytes – Phagocytosis* Lymphocytes – cooperate in Phagocytosisa. T-Lymphocytes – heart of cell-mediated immune responseb. B- Lymphocytes – heart of antibody immune response

6. Maintains acid-base balance through the buffer system w/c neutralizes acids and bases.

*Buffer – a chemical substance that resist changes in the pH of a solution when an acid or base is added on it.

COMPONENTS OF CIRCULATORY SYSTEM

1. Blood Vascular Systema. Heartb. Blood vessels c. Blood

2. Lymphatic System – a cooperating system, the function of which is to turn lymph to the blood.

a. Lymph – form from blood plasma that filtered from the blood vessels.

b. Body fluids – related to fluid balance in the body.

c. Intracellular – within the cell (40%)d. Extracellular – outside the cell (20%)e. Plasma – found in blood vessels (5%)f. Intercellular – tissue fluid in interstitial

compartment.

Unicellular• Single-celled organisms obtain oxygen and nutrients

directly across the surface of the cell.• Exchanges occur directly with environment.

Ex. Amoeba, Euglena

Multi-cellular• Multi-cellular organisms require methods for transporting

materials to and from cells which are far removed from the external environment.

CIRCULATORY SYSTEMSUnicellular and Multi-cellular

TYPES OF CIRCULATORY SYSTEMS

1. OPEN CIRCULATORY SYSTEMA system made up of well-developed blood vessels which pass from the heart to body tissues.

A tubular muscle, or heart, pumps hemolymph through a network of channels and body cavities, before draining back to the central cavity

Ex. Mollusk and Arthropods

2. Closed Circulatory SystemThe blood is confined in tubes throughout its course from the heart to the tissues and back to the heart.

Ex. All vertebrates (Human)Annelids and Cephalopods

INVERTEBRATE CIRCULATORY SYSTEM

Sponges and most Cnidarians- use water from the environment as a circulatory fluid.

Pseudocoelomate Invertebrates - use the fluids of the body cavity for circulation = Gastrovascular cavity

VERTEBRATE CIRCULATORY SYSTEM

I. HEARTThe main propulsive organ of the circulatory system/ pumping organ.

Layers of the Heart

1. Endocardium (inner)

2. Myocardium (middle)

3. Epicardium (outer)

TYPES OF HEART:a.TWO-CHAMBERED HEART

Ex. Fishes

b.THREE-CHAMBERED HEART

Ex. Amphibians and Reptiles

c.FOUR-CHAMBERED HEART Ex. Aves and Mammals

TWO-CHAMBERED HEARTEx. Fishes

The development of gills required a more efficient pump.The first chamber – sinus venosus and atrium; second chamber –

conus arteriosus and ventricle.

The evolution of lungs in amphibians involved a major change in the pattern of circulation – a second pumping circuit.

After blood is pumped from the heart through pulmonary arteries to the lungs, it is returned to the heart via pulmonary veins.

Double circulation – gives boost to speed or pressure at which blood is transported to the rest of the body.

Pulmonary circulation moves blood between the heart and lungs.

Systemic circulation moves blood between the heart and the rest of the body.

THREE-CHAMBERED HEARTEx. Amphibians and Reptiles

Amphibians and most reptiles have a 3-chambered heart.

• Amphibians obtain additional oxygen via diffusion through their (moist) skin.

• Reptiles have a septum that partially subdivides the ventricle.

• CAVUM VENOSUM• CAVUM ARTERIOSUM

• Separation is complete in Crocodilians (septum divides ventricle into 2 separate ventricles; a 4-chambered heart)

• Further reduces mixing of blood in the heart.

• Atria receive blood returning to the heart• Ventricles pump blood out of the heart

AMPHIBIAN AND REPTILIAN CIRCULATION

FOUR-CHAMBERED HEART

The heart functions as a two-cycle pump.

Both atria fill with blood and simultaneously contract, emptying the blood into the ventricles (atrial contraction)

Both ventricles also contract at the same time, pushing blood into the pulmonary and systemic circulations (ventral contraction)

The cardiac cycle includes the atrial and ventricular contraction, and the resting period between these two

Atrioventricular (AV) valves maintain unidirectional flow between the atria and the ventricles: tricuspid (right) and bicuspid (left)

Semilunar valves maintain unidirectional flow out of the ventricles to the arterial systems

Pulmonary valve located at exit of the right ventricle

Aortic valve located at the exit of the left ventricle

Valves open and close as the heart goes through its cycle.

The closing of the valves produce the “lub-dub” sounds heard with a stethoscope.

Diastole (Resting) Phase

Blood returns to the resting heart through veins that empty into the right and left atriaAs blood fills the atria and pressure rises, the AV valves open and blood flows into the ventriclesThe ventricles become ~80% full from this process; contraction of the atria fills the remaining 20%

Ventricles are relaxed = diastole phase

Systole (Ventricle Contraction) Phase

Following a slight delay from the diastole phase, the ventricles contract = systole phaseContraction of the ventricles increases the pressure within each chamber, causing the AV valves to forcefully close; this forces the semilunar valves open and blood flows into the arterial systemsAs the ventricles relax, closing of the semilunar valves prevents backflow

Four-Chambered Heart and its Blood Vessels

Arteries – carry blood away from the heart; branch into arterioles.

“Elastin” – a protein in connective tissue.

Capillaries – where materials (O2, CO2, nutrients, metabolic wastes) are exchanged.

Veins – carry deoxygenated blood back towards the heart.

Coronary arteries are the first branches off the aorta and supply the heart muscle with

oxygenated blood.

Blood from the body’s organs (now low in O2) returns to the heart via systemic veins, which empty into 2 major veins:

Superior vena cavaInferior vena cava

MEASURING BLOOD PRESSURE

• As the ventricles contract, they generate tremendous pressure, which is transferred through the arteries once the AV valve opens

• Arteries contain large amounts of elastin, an elastic protein which allows for dilation/stretching and rebound.

• A pulse results from changes in pressure as arteries expand and contract with blood flow.

Blood Pressure Is a general indicator of cardiovascular health.Arterial blood pressure can be measured with a sphygmomanometer at the

brachial artery on the inside part of the armA tightened cuff stops the flow of blood to the lower part of the arm; As the

cuff is loosened, blood begins pulsating through the artery = systolic pressure; ventricles are contracting

As the cuff is loosened further, the vessel is no longer distorted and the pulsing stops = diastolic pressure; ventricles are relaxed

MEASURING BLOOD PRESSURE

• Systolic pressure is the peak pressure at which ventricles are contracting

• Diastolic pressure is the minimum pressure between heartbeats at which the ventricles are relaxed

• Written as a ratio of systolic over diastolic

• Typical blood pressure is 120/75; >150 systolic or >90 diastolic = hypertension

MEASURING BLOOD PRESSURE

CONTRACTION OF CARDIAC MUSCLE

• Each cell in heart produces an action potential (electrical signal that is stimulus for cell to contract); fairly long in duration; 250 milliseconds from start to finish

• Can’t start another action potential until the other is completely finished

• The sinoatrial (SA) node located in the wall of the right atrium acts as a pacemaker by producing spontaneous action potentials

• Action potentials are generated by a constant leakage of Na+ ions into the cell that depolarize the membrane

• When the threshold is reached, the action potential occurs• Allows heart muscle to carry signal over distance; conducted

rapidly over both ventricles by a network of fibers, including Purkinje fibers, which spread electrical activity to rest of heart

• An electrocardiogram (ECG or EKG) records the electrical activity of the heart.

• Illustrates via electrodes how the cells of the heart depolarize and repolarize during the cardiac cycle (action potentials)– Depolarization causes contraction of the heart– Repolarization causes relaxation– Depolarization of the atria produces first peak; depolarization of

ventricles produce second, larger peak– Repolarization produces third peak

CONTRACTION OF CARDIAC MUSCLE

BLOOD VESSELS: ARTERIES• Arteries have thicker walls than veins; arterioles have less elastin than arteries; Arteries deeply set, no valves.

BLOOD VESSELS: VEINS

• Less muscle is needed in veins because the pressure in veins is only ~1/10th of that in the arteries

• Venous pressure alone is not sufficient to return blood to the heart

• Thus, skeletal muscles surrounding the veins contract to move blood by squeezing the veins; the venous pump

• Internal valves in veins (venous valves) ensure that blood continues to heart; operate as one-way swinging doors

• Skeletal muscles on outside of vein contracts, pushes against vein, causing blood to flow towards heart; this opens one-way valves up, pressure is released and cannot return through valves (one-way transport to heart)

BLOOD VESSELS: VEINS

• Capillaries bridges the gap between the arteries and veins; only have the inner epithelium layer (site of gas/nutrient/waste exchange)

• Blood flows slower through capillaries because of larger total cross-section

– Enables materials to be exchanged– By the time blood reaches the end of the capillary, it

releases some of its oxygen and nutrients and picks up CO2 and waste products

BLOOD VESSELS: CAPILLARIES

TYPES OF CAPILLARIES

1. CONTINUOUS CAPILLARIES2. FENESTRATED CAPILLARIES3. SINUSOIDS/DISCONTINOUS CAPILLARIES

Blood serves to transport, regulate, and protects.

Blood is composed of a fluid-matrix known as plasma, within which reside different cells and other ‘elements’.

•Plasma - 55%of the blood - consisting 90% - water 8-10%solid elements

Normally, the following are present in the plasma of the blood:a.Calciumb.Prothrombinc.Heparin (anti-prothrombin)d.fibrinogen

COMPONENTS OF BLOOD

• Blood corpuscle cells – 45% of the blood- RBC, WBC and platelets

–Ions, proteins–Nutrients, wastes and hormones

• Red Blood Cells (Erythrocytes)Most numerous: 5 million/mL

–Transport O2 and CO2

(hemoglobin in vertebrates)–Mammalian erythrocytes lack nuclei

COMPONENTS OF BLOOD

• White Blood Cells (Leukocytes)– Fewer in number; 1-2 for every 1000 erythrocytes– Larger in size, and have nuclei– Not confined to blood as erythrocytes are; can migrate out of

blood into surrounding interstitial fluid or into the lymphatic system – where your body fights infection

– Function in body’s defense

Lymphocytes – produced in lymphoid tissue; 20-25% of WBC.

- forms the basis of immunity by producing antibodies.

COMPONENTS OF BLOOD

• Platelets (Thrombocytes)– Cell fragments that pinch off from larger cells in the bone

marrow– Following injury to a blood vessel, platelets release clotting

factors (proteins) into the blood– When platelets contact collagen, they stick to it ; results in

release of several factors which activate other platelets.

Conversion of fibrogen (soluable) to fibrin (insoluable); fibrin threads cross-link, connecting platelets and trapping other cells in network = blood clot

Blood Clotting – primary intended to prevent excessive loss of blood from the body.

COMPONENTS OF BLOOD

FORMATION OF BLOOD CLOT

BLOOD TYPES

• Type A, B, O (and AB)– Each contains antibodies of other types

• Agglutinogens or antigen A or B- CHON present normaly in cells of erythrocytes

• Agglutinis (antibodies) or anti-serum A or B – CHON present in serum or plasma in blood.

• Rh factor – presence or absence of Rh protein– Positive (have) or negative (do not have)– Negatives will form antibodies against Rh blood upon exposure