Unit 7: Circulatory System

Circulatory System

Multicellular organisms (above the level of roundworms) rely on a circulatory system to bring nutrients to, and take wastes away from, cells.

The Circulatory System consists of:

•Blood vessels: Includes Arteries, arterioles, capillaries, venules, and veins. (In the order from leaving to arriving heart)

•Heart:

Muscular organ about the size of a fist. Pumps blood.

Blood Vessels

•Arteries and arterioles carry blood from heart to tissues.

•Veins and venules carry blood from tissues back to heart.

•Capillaries connect the arterioles to venules, and exchange material with the tissues.

Arteries and arterioles

•Arteries carry blood away from the heart.

• Thick walls composed of elastic and muscular fibers (plus supporting tissue).

•Arteries branch into Arterioles, which are small branches of arteries that are about 0.2 mm in diameter or smaller.

Capillaries

•Arterioles branch into small vessels called capillaries. Capillaries are very narrow, microscopic tubes.

• The walls of these tubes are one cell layer thick.

•Gases and small molecules like glucose exchange across the walls of the capillaries.

Capillaries

• Sphincter muscles encircle the entrance to each capillary. • In a capillary bed (networks

of many capillaries), some, many, or most of these sphincter muscles may be closed off so that less or more blood flows to that area, as needed (e.g. more blood to muscles when they are working).

Veins and venules

• Take blood from the capillaries to the heart.

•Venules drain the blood from capillaries and then join to form a vein.

•Walls are thinner than arterial walls.

Veins

•Veins have valves. Valves allow blood to flow only toward the heart when the are open and prevent the backward flow of blood when they are closed

• Skeletal muscle also contract to aid in blood movement against gravity

Cross-sectional area, pressure, and velocity

At any one time the

• veins contain about 75% of the body's blood.

•About 20% of the body's blood is in the arteries

• and only about 5% is in the capillaries.

Heart

• The major portion of the heart is called the MYOCARDIUM, and is mostly composed of CARDIAC MUSCLE.

Heart

• Epithelial and fibrous tissue called pericardium covers the heart.

Heart

•Heart is TWO SEPARATE PUMPS: one (on the right side of the heart) pumps blood to the lungs, and the other (on the left side of the heart) pumps blood to the rest of the body.

Heart

• The left and right side of the heart is divided by the SEPTUM.

Heart

•On each side are two chambers. The smaller

•one, located on the top, is called the ATRIUM (plural = “atria”).

• The larger one, on the bottom, is called the VENTRICLE.

Heart

• There are VALVESbetween the atria and ventricles, collectively referred to as ATRIOVENTRICULAR VALVES. These valves control the flow of blood between the chambers, and prevent "backflow."

Heart

• The atrioventricular valve separating the Right Atrium from the Right Ventricle is called the TRICUSPID VALVE (has 3 flaps or "cusps"), • The atrioventricular valve

between the left atrium and left ventricle is called the BICUSPID VALVE or MITRAL VALVE (has 2 cusps).

Heart

•Very strong, fibrous strings called the CHORDAE TENDINAE support the valves and prevent them from inverting. The chordae tendinae are firmly attached to muscular projections of the ventricular wall.

Heart

• Each ventricle also has a SEMILUNAR VALVE

• The right ventricle then, has a pulmonary semilunar valve

• The left side has an aortic semilunar valve

• The semilunar valves have no chordae tendinae. Why?

• the path of blood from the heart through the LUNGS.

Vena cava

• The largest veins in the body. Has two of these.

• The one that direct upper body blood to the heart is called superior vena cava

• The one that direct lower body blood to the heart is called inferior vena cava

Aorta

• The largest artery.

•Branches of the aorta lead to all major body regions and organs.

Describe the path of blood

Trace the path of blood from kidney to heart then back to kidney.

Trace the path of blood from stomach back to stomach.

Upper Body major arteries

Upper Body major veins

Coronary Artery

•Heart muscle requires its own blood supply.

•Coronary arteries supply the nutrient and oxygen to heart muscles.

Coronary Artery

•Coronary veins return the blood to the right atrium directly.

Summary of the Major Blood Vessels you Should know

Atherosclerosis

•Atherosclerosis is the hardening of the arteries caused by cholesterol plaque deposits. It can occur in the coronary arteries, the carotid arteries, the aorta, and the leg arteries.

Heart Attack

• if a coronary artery becomes plugged (e.g. with cholesterol), and blood is not supplied to part of the heart, a heart attack occurs. Pain occurs in upper left arm and shoulder.

Thrombosis

• a stationary clot attached to an arterial wall. Slows the flow of blood.

Embolism

• a thrombus that has become dislodged and moves along with the blood. When the vessel narrows, the embolus gets stuck and entirely blocks the flow of blood in a small vessel.

Stroke

•when portion of brain dies due to lack of oxygen -- usually when arteriole bursts or is blocked by an embolism. Strokes usually cause death or paralysis.

A person having atherosclerosis will often experience

symptoms of angina, stroke, and claudication (limb

pain or tiredness). All of the symptoms are caused by insufficient blood flow due to atherosclerosis.

The blood vessel shown carries blood between organs at locations

X and Y. Blood flow through the vessel would be from the

A. heart at X to the kidneys at Y.

B. intestine at Y to the liver at X.

C. heart at Y to the kidneys at X.

D. intestine at X to the liver at Y.

The chordae tendineae are indicated by the letter

A. W

B. X

C. Y

D. Z

The path followed by blood on one circuit through the heart is

A. ventricle, atrioventricular valve, semilunar valve, atrium.

B. atrium, atrioventricular valve, ventricle, semilunar valve.

C. atrium, ventricle, atrioventricular valve, semilunar valve.

D. atrium, semilunar valve, ventricle, atrioventricular valve.

A red blood cell leaves the aorta, makes a circuit through the body and arrives back in the capillaries of the alveoli. The correct sequence of organs through which the cell may have travelled is

A. lungs, heart, small intestine, liver. B. small intestine, heart, liver, lungs. C. liver, lungs, small intestine, heart. D. small intestine, liver, heart, lungs.

HEARTBEAT

The heartbeat is INTRINSIC.

the heart has its own SPECIAL TISSUE, called NODAL TISSUE, which has characteristics of both nerve and muscle tissue, which controls the heartbeat.

There are TWO nodal regions in the heart:

• SA (sinoatrial) NODE (also called the PACEMAKER)

•AV (atrioventricular) NODE

Sinoatrial Node: Pacemaker

• Located in the upper back wall of the right atrium.

• Sends out a signal automatically about every 0.85 seconds to make the ATRIA CONTRACT

Artificial Pacemaker

If SA node doesn't work, the heart will beat irregularly. This can be corrected by implanting an ARTIFICIAL PACEMAKER, which will send out an electric signal every 0.85 seconds to stabilize the heart rate.

Atrioventricular Node

• Found in the base of the right atrium near the septum.

• The SA node sends its signal along fibers to the atria and also to the AV node.

Atrioventricular Node

•When the pulse sent out by the SA node reaches the AV node, the AV node itself the sends out a signal along special conducting fibers called PURKINJE FIBERS. These fibers take the message to the VENTRICLES, and cause them to contract.

Electrocardiogram: ECG

Cardiac cycle

The sound of heart beat

There are two parts to each heart beat. Each “LUB DUB” is one heart beat.

The “LUB” sound comes from the shutting of AV valves after atria contract.

The “DUB” sound comes from the shutting of semilunar valves after ventricles contract.

While the heart can keep a steady beat on its own, the how fast it goes (heart rate) is under NERVOUS CONTROL. Specifically, there is a HEART-RATE CENTER in the brain (to be precise, in the MEDULLA OBLANGATA)

Pulse

• The alternate expanding and recoiling of an arterial wall that can be felt in any artery that runs near the surface of the body.

•Radial artery in wrist, carotid artery in neck are common places to check.

•Pulse rate indicates the rate of heartbeat.

Which area indicated in the diagram is the location of the AV node?

Systole of the ventricles is occurring at

The sequence of structures through which the nerve impulse passes to cause contraction of the heart is A. AV node – SA node – Purkinje fibres. B. Purkinje fibres – AV node – SA node. C. Purkinje fibres – SA node – AV node. D. SA node – AV node – Purkinje fibres.

Blood Pressure

•Measure blood pressure with an instrument called a SPHYGMOMANOMETER.

SYSTOLIC BLOOD PRESSURE: the highest arterial pressure reached during ejection of blood from the heart.

DIASTOLIC BLOOD PRESSURE: lowest arterial pressure. Occurs while the ventricles are relaxing.

Normal resting blood pressure is 120 mm Hg over 80 mm Hg in brachial artery of arm (120/80). Of course, blood pressure decreases with distance from left ventricle.

High blood pressure is 140 mm Hg over 90 mm Hg.

Clinical Term: Hypertension

Nervous System controls heart rate and breathing

Autonomic nervous system has two branches.

• Sympathetic (fight-or-flight)

•Parasympathetic (rest-and-digest)

Diving Reflex

When face is dived into ice cold water, the reflex actives as to conserve oxygen by redirecting blood flow to brain and heart and away from other organ.

Fetal CirculationWhile the fetus is inside the mother’s womb, it cannot breath air. Therefore, the lung has no function. In fact, fetus blood will not need to go through lung. As a result, the paths of a fetus circulatory system is slightly different than that of an adult.

The fetus has four features that are different from adult.

1. Oval opening

2. Arterial duct

3. Umbilical vein and artery

4. Venous duct

OVAL OPENING (foramen ovale)Opening between the two atria, covered by a flap that acts like a valve.

Some of the blood from the right atrium is therefore pumped through this flap and into the left atrium, bypassing the pulmonary circuit.

OVAL OPENING (foramen ovale)If the oval opening doesn’t close after birth, it can cause mixing of blood and “blue babies”. Correct with open heart surgery.

ARTERIAL DUCT: (ductus arteriosus)Connects pulmonary artery and aorta. Much of the blood being pumped out of the heart to the lungs will be directed away from the lungs and into the aorta. Like the oval opening, the arterial duct’s function is to bypass the pulmonary circuit.

UMBILICAL ARTERIES AND VEINS:Vessels that travel to and from PLACENTA (a membrane shared by the mother and baby across which gases, nutrients, and wastes are exchanged). The umbilical arteries are grafted to the iliac arteries.

VENOUS DUCT (ductus venosus):Connects umbilical vein to the venae cava to bring the blood back to the baby’s heart. It attaches right at the babies liver, but bypasses most of the liver.

This is why chemicals ingested by the mother can seriously affect the baby!

PATH OF BLOOD THROUGH FETUS• Begin with blood collecting in Right Atrium

• From there, blood can go into Left Atrium through Oval opening plus into Right Ventricle through atrioventricle valve.

• Right Ventricle to Pulmonary Artery. Most of blood will go through arterial duct into aorta.

• Aorta to tissue. Umbilical arteries lead to placenta, where exchange of gases and nutrients take place.

• Umbilical vein carries O2-rich blood. It enters the venous duct, passes through liver.

• Venous duct joins with inferior venae cava (it mixes here with deoxygenated blood) and this mixed blood goes back to the back to heart.

Placental Barrier

Placenta allows for gas and nutrient exchange between fetal and maternal blood.

However, no actual blood mixing takes place.

Blood composition

• About 55% of blood volume is plasma, the fluid portion of blood.

• Cells account for about 45% of blood volume. These are called formed elements.

Plasma

• Plasma contains a variety of dissolved materials including gases, glucose, amino acids, ions and vitamins. The plasma also contains wastes and hormones.

• Proteins (1) Albumin acts as a solute in plasma to regulate the movement of water into and out of blood by osmosis. (2) Proteins that carry lipids (HDL and LDL). (3) Fibrinogen needed for blood clotting.

Formed elements

Red blood cells (RBCs) or erythrocytes

(1) Red blood cells are continuously produced in the red marrow of the skull, ribs, vertebrae, and ends of the long bones.

Formed elements

Red blood cells (RBCs) or erythrocytes

(2) Cells are shaped like biconcave disks to increase surface area. This surface area increases the rate of exchange between RBCs and tissue. They lack a nucleus to have more space for hemoglobin so they can carry more oxygen.

Formed elements

Red blood cells (RBCs) or erythrocytes

(3) RBCs have membrane glycoproteins of specific types which allow us to divide them into the 4 blood types.

ABO Blood Typing

The glycoproteins on the red blood cells that determines the blood types are called antigens.

• Type A Blood carries Antigen A

• Type B Blood carries Antigen B

• Type AB Blood carries both Antigen A and B

• Type O Blood carries no antigen

ABO Blood Typing

Immunoproteins that recognizes antigens are called antibodies.

Antibodies will seek out its counterpart and cause agglutination.

i.e. Anti-A will cause RBCs with antigen A to agglutinate.

In order for a person with a specific blood type to protect themselves, the person will have antibodies for antigens that are missing on the RBCs.

i.e. Type A blood will contain anti-B antibody.

ABO Blood Typing

Anti Serum Test

Transfusion of incorrect blood type can result in blood agglutination. Before blood transfusion is administered, an anti-serum test is performed.

Anti-A serum contains anti-A antibody.

Anti-B serum contains anti-B antibody.

Rh factor Blood Typing

A person who has Rh antigen has no anti-Rh antibody.

The person is said to be Rh+

A person who has no Rh antigen has anti-Rh antibody.

The person is said to be Rh-

Formed elements

White blood cells (WBCs) or leukocytes

(1) Leukocytes are less than 1% of total blood cells but are an important part of the immune system.

(2) They circulate in blood and can exit into the fluid surrounding the tissues.

Formed elementsPlatelets are tiny cells that play important role in blood clotting.