Human Circulation

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

Special Circulatory Systems z In this case materials are absorbed across the cell membrane by diffusion. z For larger organisms,where some cells may be located far away from the outside, a special circulatory system is required. z These systems may be open or closed.

Closed and Open Systems zA closed system, is one in which the blood is always confined in vessels (Ex. Earthworm). zAn 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). zAssignment: Write a detailed summary of open and closed circulation in the earthworm and grasshopper (pages ). Also complete the coloring sheet-Correlative Circulatory Patterns.

Components Involved zThree components: z1. A fluid to transport dissolved materials (Blood) See handout-Components and Function. z2. A network of tubes (or body spaces) to carry fluid (Blood vessels). zA means of pumping the fluid (Heart).

Blood z Blood is a special type of connective tissue. z Two components; Formed Elements (the blood cells) and Plasma (fluid).

Blood-Erythrocytes-Red Blood Cells z Make up 44% of blood. z Biconcave z no nucleus z contain the respiratory pigment hemoglobin (carries oxygen) z life span of days

Blood-Erythrocytes-Red Blood Cells continued z Lost cells are replaced by new cells produced in the red bone marrow. z 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 zMore like body cells. zMake up 1% of blood. zHave nuclei. zProduced by lymphatic tissue. zServe as a “movable army”-protect the body from bacteria, viruses and tumor cells.

Blood - Platelets z Believed to be fragments of other blood cells formed in red bone marrow. z Small, irregular shapes. z Needed for clotting.

Blood Clots zA whole series of reactions called the blood clotting cascade creates the clot. zReduces blood loss. zClotting process involves a number of substances.called the clotting factors.

Plasma z Liquid portion z Make up 55% of blood. z Contains water, salts, proteins, nutrients, z waste products and hormones.

The Blood Vessels zThere are three main types of blood vessels: z1. Arteries z2. Veins z3. Capillaries

Arteries zCarry blood away from the heart. zThick muscular walls. zNo valves. zForm arterioles that join with capillaries in the capillary network. zBlood pressure higher than in veins.

Artery Structure Connective tissue Smooth muscle Elastic fibers Endothelium

Veins z Veins are the vessels that carry the blood to the heart. z Thin muscular walls. z Valves to prevent back flow. z Venules that join capillaries in the capillary network. z Blood pressure tends to be lower than in arteries.

Veins Structure Connective Tissue Smooth muscle Elastic Fibers Valve Endothelium

Capillaries zCapillaries connect arterioles and venules. zThe wall of a capillary is made up of a single layer of endothelial cells. zThin walls allow for nutrients and gases to diffuse quickly between the blood and body cells. Single layer of endothelium.

Blood Flow in the Heart z Deoxygenated blood from the body enters the right atrium and is pumped to the lungs by the right ventricle. z Oxygenated blood returns to the left ventricle under high pressure and is pumped to the body tissues. z Note the thicker walls in the left ventricle that serve to handle the higher pressure.

Blood Flow in the Heart z This animation shows the flow of blood in the heart.flow of blood in the heart

The Heart Beat Cycle (HBC) zThe HBC refers to the periods of contraction and relaxation of the atria and ventricles in the heart. zRelaxation is known as diastole and contraction is called systole. zThe accompanying blood pressure changes are called diastolic and systolic. zSee the handout called The Heart Beat Cycle.

Pulmonary Circulation z Blood travels through pulmonary arteries to the lungs. z Gas exchange occurs at the capillary level in the alveoli. z Veins pick up the oxygenated blood and bring it back to the left atrium via the pulmonary vein. Alveoli Capillary Network Gas Exchange