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Questions we’ll answer

What are the mechanisms through which living things keep individual cells nourished and healthy?

How does the heart pump blood to all parts of your body?

What are the major circulatory pathways in the human body?




Circulatory System



Lymphatic system



Transport and Circulation

Circulatory System

Example: Humans

Transport in Protists

Transport in Protists

Transport in a Hydra



Transport in the Earthworm


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Blood carries nutrients, gases, wastes, water, etc. in a closed circulatory system.

Red color-hemoglobin- iron pigment- increases the amount of oxygen the blood can carry.

Major blood vessels

Dorsal vessel-runs along the top of the digestive tract.

Ventral vessel- runs below the digestive tract.

Aortic arches- 5 pairs of blood vessels "hearts" that connect the dorsal and ventral vessels near the head. These vessels pump the blood from the dorsal to the ventral vessel.

Capillaries- microscopic blood vessels through out the worm that arise from the ventral vessel


Transport in the Grasshopper

Open circulatory system- blood not always contained in blood vessels.

Blood is colorless because of a lack of hemoglobin. It does not transport oxygen or other gases.

Insert grasshopper

Differences between closed and open circulatory systems


Blood under pressure

Blood moves faster


Blood not confined in vessels so no pressure

Blood moves slower

Section Review

What are the three main parts of the circulatory system?

Name the processes that are involved in the transport of materials in Protists

How does a closes circulatory system differ from an open circulatory system?

What does the blood of a grasshopper transport?

Critical thinking: What type of circulatory system would you expect to find in a bee?

Explain why.

The Human Circulatory System

Humans have a closed circulatory system
A single heart and multiple blood vessels

Three types of blood vessels

Arteries- carry blood away from the heart. Walls are thick and elastic. As arteries enter organs the divide and subdivide into smaller arteries

Arterioles-smallest arteries

Add picture of artery

Blood vessels cont:

Veins- return blood from body tissues to the heart- walls are thin and only slightly elastic.

Valves allow the blood to flow only in one direction

Venules – smallest veins

Varicose- stretched and less elastic state of veins whose valves are not working right

Add picture of a vein

Blood vessels cont.

Capillaries-microscopic connections between arterioles and venules. These vessels are very narrow and the walls are very thin allowing the exchange of nutrients, wastes, oxygen and other substances between the blood and the body cells.

Add picture of a capillary

The Heart

Muscle- slightly larger than a fist

Acts as a pump- contractions force blood through the vessels

Right side sends poorly oxygenated blood to the lungs

Left side send oxygen rich blood to the rest of the body


Anatomy of the heart

Pericardium-tough outer membrane for protection.

Four chambers

Atria and auricles-upper thin-walled chamber.

Ventricles- lower thick-walled chambers

Septum- separates the left from the right and prevents poorly oxygenated blood on the right from mixing with well-oxygenated blood on the left

Four valves-control direction of blood flow in the heart

Heart anatomy cont.

Four valves:

Two A-V (arterioventricular)- allow blood to flow only from the atria into the ventricles

In the right side of the heart the valve is called the tricuspid (three flaps).

In the left side, it is called the bicuspid or mitral valve (two flaps).

Heart anatomy cont. (valves)

Two semilunar valves- When open, allow blood to move from the ventricles into the arteries that carry blood away from the heart. When closed, they stop blood from flowing backwards into the ventricles.

Heartbeat cycles

Distole- resting phase of the heart- AV valves are open and blood flows from the atria to the ventricles.

Systole- working phase of the heart- contraction of the atria forces more blood into the ventricles causing them to contract. The AV valves close and the semilunar valves open and blood flows out of the right ventricle to the pulmonary artery that branches out to the lungs. Blood flows out of the left ventricle into the aorta (the largest artery in the body) that sends blood to all other areas of the body.


"Lub-Dub" is the sound made as the heart valves open and close. "Lub" is produced by the closing of the AV valves. "Dub" is produced by the closing of the semilunar valves.

Heart murmur is an abnormal heart sound caused by a diseased or damaged valve.

Control of the Heartbeat

Muscle of the heart has a built in ability to contract; this is made possible by the S-A (sinotrial node) or pacemaker. The S-A node sends an electrical signal to the right atrium which causes it to contract. Immediately the A-V (atrioventricular)node triggers the ventricles to contract. These signals can be recorded and monitored using an Electrocardiogram (ECG). The rate of the heartbeat is controlled by vagus nerves that slows the heart rate or the cardioaccelerator nerves that speed the heart rate

Blood flow and blood pressure

Pulse- the expansion and relaxation that can be felt in the artery each time the ventricle contracts and relaxes. Both the rate and the force can be measured by taking the pulse.

Pressure can be measured using a sphygmomanometer. Normal blood pressure in an adult is 120/80.

High Blood Pressure (hypertension)

Blood pressure remains above normal throughout the heartbeat cycle. It is serious and fairly common.

Cause of Hypertension:

Atherosclerosis- "hardening of the arteries"-cholesterol and other fatty material collects and deposits on the artery walls causing blood to move slower through the vessels causing strain on the heart and blood vessels that can lead to heart attack.

Preventing Heart Disease

Don’t smoke.

Monitor blood pressure.

Reduce amount of cholesterol in foods eaten.

Decrease salt intake.

Exercise regularly.

Avoid obesity.

Learn to manage stress.

Section review

Pathways of human circulation

Circulation of blood.

Pulmonary circulation- begins in the right ventricle and pulmonary arteries and carries blood between the heart and the lungs.

Adds oxygen

Removes carbon dioxide


Pathways cont.

Systemic circulation- begins in the left ventricle and carries blood between the heart and all other areas of the body. From the ventricle the blood enters the aorta that branches into arteries that serve all parts of the body. Arteries divide and subdivide until they form capillaries that merge to form veins that return blood to the heart.

Pathways cont.

Systemic circulation cont:

The largest veins in the body are:

Superior vena cava-returns blood from the head, arms and chest to the heart.

Inferior vena cava- returns blood from the lower body to the heart.

The 3 branches of systemic circulation are:

Coronary circulation- heart

Hepatic-portal circulation-liver

Renal circulation-kidneys

Pathways cont.

Lymphatic circulation- all the cells in the body are bathed in a clear, watery fluid called intercellular fluid that helps move material between the capillaries and body cells and consists of water, salts, proteins and nutrients. Without it, blood would drain from the circulatory system.

Pathways cont.

Lymphatic circulation cont.

Lymphatic system begins in the body tissues with lymph capillaries-microscopic tubes that are closed at one end whose walls are one cell thick. Intracellular fluids and proteins pass readily into these capillaries and become Lymph.

Lymphatic capillaries merge to become larger and larger vessels. The lymph from the left side of the body empty into the thoracic duct (larges lymphatic vessel in the body and eventually into a large vein on the left side of the neck. The lymph from the right side of the body enters the right lymph duct which drains into a large vein on the right side of the neck. In this way, fluids lost from the blood in the capillaries are returned to the blood.

Pathways cont.

Lymphatic circulation cont.

Lymph nodes or lymph glands: filter foreign material from lymph fluid. Prevents cancer, bacteria and other disease-causing organisms from entering the bloodstream.

May become enlarged and painful when infection is present.

Spleen also filters bacteria from the lymph system.

Section Review

How do the pulmonary arteries differ from other arteries in the body?

What parts of the body are served by the systemic circulation?

What are the three major branches of the systemic circulation?

What is the role of the lymphatic system?

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