Human Circulation

The Need for Circulation

All living things must be able to supply their cells with materials from the surrounding environment (Ex. Oxygen, nutrients, enzymes ,etc.)

Special Circulatory Systems

In this case materials are absorbed across the cell membrane by diffusion.

For larger organisms,where some cells may be located far away from the outside, a special circulatory system is required.

These systems may be open or closed.

Closed and Open Systems

A closed system, is one in which the blood is always confined in vessels (Ex. Earthworm).

An open system, is one in which the blood is not always enclosed in vessels, but flows into open spaces where it bathes the tissues of the body directly(Ex. Grasshopper).

Assignment: Write a detailed summary of open and closed circulation in the earthworm and grasshopper (pages 146-147). Also complete the coloring sheet-Correlative Circulatory Patterns.

Components Involved

Three components:1. A fluid to transport

dissolved materials (Blood) See handout-Components and Function.

2. A network of tubes (or body spaces) to carry fluid (Blood vessels).

A means of pumping the fluid (Heart).

Blood

Blood is a special type of connective tissue.

Two components; Formed Elements (the blood cells) and Plasma (fluid).

Blood-Erythrocytes-Red Blood Cells

Make up 44% of blood.

Biconcaveno nucleuscontain the

respiratory pigment hemoglobin (carries oxygen)

life span of 100-120 days

Blood-Erythrocytes-Red Blood Cells continued

Lost cells are replaced by new cells produced in the red bone marrow.

The rate of RBC production is called hemopoiesis, and is controlled by the hormone erythropoietin (released by the kidneys in response to decreasing oxygen levels in the blood).

Blood- White Blood Cells

More like body cells.Make up 1% of blood.Have nuclei.Produced by

lymphatic tissue.Serve as a “movable

army”-protect the body from bacteria, viruses and tumor cells.

Blood - Platelets

Believed to be fragments of other blood cells formed in red bone marrow.

Small, irregular shapes.

Needed for clotting.

Blood Clots

A whole series of reactions called the blood clotting cascade creates the clot.

Reduces blood loss.Clotting process

involves a number of substances.called the clotting factors.

Plasma

Liquid portion Make up 55% of

blood.Contains water,

salts, proteins, nutrients,

waste products and hormones.

The Blood Vessels

There are three main types of blood vessels:

1. Arteries2. Veins3. Capillaries

Arteries

Carry blood away from the heart.

Thick muscular walls.No valves.Form arterioles that

join with capillaries in the capillary network.

Blood pressure higher than in veins.

Artery Structure

Connective tissueSmooth muscle

Elastic fibers

Endothelium

Veins

Veins are the vessels that carry the blood to the heart.

Thin muscular walls.Valves to prevent back

flow.Venules that join

capillaries in the capillary network.

Blood pressure tends to be lower than in arteries.

Veins Structure

Connective TissueSmooth muscle

Elastic Fibers

ValveEndothelium

Capillaries

Capillaries connect arterioles and venules.

The wall of a capillary is made up of a single layer of endothelial cells.

Thin walls allow for nutrients and gases to diffuse quickly between the blood and body cells.

Single layerof endothelium.

Blood Flow in the Heart

Deoxygenated blood from the body enters the right atrium and is pumped to the lungs by the right ventricle.

Oxygenated blood returns to the left ventricle under high pressure and is pumped to the body tissues.

Note the thicker walls in the left ventricle that serve to handle the higher pressure.

Blood Flow in the Heart

This animation shows the flow of blood in the heart.

The Heart Beat Cycle (HBC)

The HBC refers to the periods of contraction and relaxation of the atria and ventricles in the heart.

Relaxation is known as diastole and contraction is called systole.

The accompanying blood pressure changes are called diastolic and systolic.

See the handout called The Heart Beat Cycle.

Pulmonary Circulation

Blood travels through pulmonary arteries to the lungs.

Gas exchange occurs at the capillary level in the alveoli.

Veins pick up the oxygenated blood and bring it back to the left atrium via the pulmonary vein.

Alveoli

Capillary Network

Gas Exchange