The Circulatory SystemBiology 1-2

The Circulatory SystemThe circulatory system carries blood and

lymph throughout the body.Blood carries gases, nutrients and wastes.Lymph is water and things that leaked from

the blood vessels.Includes the heart, blood vessels and lymph

nodes.

Blood VesselsFive types of blood vessels:

Artery-carries blood from the heart. Thick wall of smooth muscle to pump blood.

Arteriole-small artery.Vein-carries blood to the heart.

Thin, lack the smooth muscle of the arteries. Usually buried in muscle; when muscle contracts, it

squeezes the blood back toward the heart.Venule-small vein.

Blood Vessels cont’dCapillary-connect arterioles to venules.

Where exchange between the blood and tissues takes place. Oxygen/nutrients are dropped off, carbon

dioxide/wastes are picked up.

BloodBlood is made of:

Plasma-straw-colored, mostly water includes: proteins, salts, other dissolved things.

Red blood cells-carry oxygen.White blood cells-fight infections.

Blood cont’dPlatelets are cell pieces in the blood used to

close cuts.Platelets stick together, forming a plug to stop

blood loss.The protein fibrin forms a net, strengthening

the platelet plug.New cells (mitosis) fill in and replace the plug.

Scars form when collagen fills in, not original tissue.

The Heart and CirculationOxygen-poor blood

enters the heart through the right atrium.Blood from the

head/shoulders enters the right atrium through the superior vena cava.

Blood from the rest of the body enters from the inferior vena cava.

The Heart cont’dThe right atrium

pumps blood to the right ventricle.Right ventricle

pushes blood to the lungs through the pulmonary artery.

The Heart cont’dBlood picks up

oxygen at the lungs and returns through the pulmonary vein. Enters the heart

through the left atrium.

Left atrium pumps blood to the left ventricle.

The Heart cont’dBlood leaves the left

atrium through the aorta to deliver oxygen-rich blood to the rest of the body.

The Heart cont’dThe cardiac cycle is the contraction and

relaxation of the heart.During relaxation (diastole) blood fills the

atria and ventricles.During contraction (systole) blood is pumped

into/out of the ventricles.

The Heart cont’dBlood pressure is the force that blood

exerts on the walls of the blood vessels.Created when the left ventricle contracts.Increased pressure (systolic pressure)

stretches the arterial wall. Pulse-rhythmic stretching of the arteries. During diastole, the heart relaxes and the pressure

on the arteries is at its lowest (diastolic pressure).

The Lymphatic SystemConsists of:

LymphLymph vessels-carry lymph and are found

near blood vessels.Lymph nodes-produce cells found in lymph

that fight infections. Filter fluids before they go back into the blood.

Lymphatic System cont’dThe lymphatic system does three things.

Returns lost fluids to the blood.Carries fat from the small intestine to the liver.Produces cells to fight infections.