I. Adaptations for Transport Figure 1: Open Circulation. Open Circulation:

Transcription

1 I. Adaptations for Transport Figure 1: Open Circulation Open Circulation: Arthropods have an Open Circulatory System. The circulatory fluid does not contain hemoglobin (Hb) & therefore does not function in the transport of respiratory gases & is colorless. The circulatory fluid, containing digested nutrients, is pumped forward by a dorsal blood vessel into the spaces between organs to exchange nutrients & metabolic wastes. Squeezed rearward by body movements, it reenters the dorsal vessel through openings (ostia). Figure 2: Closed Circulation Closed Circulation: Annelids have a Closed Circulatory System. The circulatory fluid is blood containing the respiratory pigment Hb. Movement of blood throughout the circulatory system is achieved by contractions of the dorsal (back) blood vessel, which pumps blood toward the worm s anterior (front) end. Near the worm s anterior end, 5 pairs of vessels called aortic arches loop around the digestive tract, connecting the dorsal & ventral vessels. These arches act as auxiliary hearts, propelling blood ventrally (toward the belly) blood flows rearward in the ventral vessels.

2 II. Human Circulation Figure 3: Blood Components Plasma: Formed Elements: Red Blood Cells: a) Are small & biconcave in shape to allow for a greater surface area for the binding of respiratory gasses. RBC s are usually confined to blood vessels & exchange respiratory gasses are released upon reaching capillaries (O 2 released, CO 2 picked up). White Blood Cells:

3 Figure 4: White Blood Cells Platelets: Figure 5: Platelets -Blood Clot Formation The clotting process begins when the lining of a vessel is damaged & exposed to blood. Platelets adhere to the lining & release a substance that makes nearby platelets sticky. The platelets form a plug that provides emergency protection against blood loss. When damage is more severe, this plug is reinforced by a clot of fibrin: a) Clotting factors released from the clumped platelets or damaged cells mix with clotting factors in the plasma (Ca, vitamin K), to convert a plasma protein called Prothrombin to its active form, Thrombin. b) Thrombin is an enzyme that catalyzes the final step of the clotting process, the conversion of the plasma protein Fibrinogen to Fibrin. The insoluble fibrin meshwork serves to trap RBC s & platelets to form a protective cap over the wound. Upon repair of the damaged blood vessel, the clot is digested by an enzyme.

4 IV. Blood Vessels Figure 6: Blood Vessels Arteries: a) In order for O 2 & digested nutrients to reach & nourish individual cells, arteries branch off & become progressively thinner, forming Arterioles as they approach the tissues & organs they service. In turn, arterioles branch off to form a thin-walled network of vessels called Capillaries. Capillaries: a) To ensure that all cells are able to receive nutrients & dispose of metabolic wastes, no cell in the body is more than 10um from a capillary bed. Capillaries coalesce to form Venules that in turn coalesce further to form Veins. Veins: a) Due to the resistance encountered when traveling through capillary beds, venuous blood is not under pressure. The action of skeletal muscles allows this blood to return to the heart against gravity. As muscles contract, venuous blood is milked back toward the heart with unidirectional valves preventing the back-flow of blood (fig 7). Figure 7: Skeletal Muscle Pump

5 Figure 8: Lymph Vessels Lymph Vessels: Approximately 99% of the ICF lost from the circulatory system is recovered by the capillary beds. Although capillaries lose only 1% of the fluid they carry as ICF, so much blood passes through the capillaries that the cumulative daily loss would be 3L! Lymph vessels are intertwined with capillary beds to reabsorb the remaining ICF (1%) that the circulatory system does not. Upon entering the lymphatic system, the fluid is known as Lymph. At various junctions along the lymphatic system, Lymph Nodes housing WBC s serve to rid the lymph of bacterial or viral pathogens. Filtered lymph fluid is then returned to the circulatory system at junctions near the shoulders.

6 V. The Heart Figure 8: Human Heart Anatomy & Blood Flow Figure 8a: Heart Anatomy Figure 8b: Blood Flow (Double Circulation) Septum: Atria: Ventricles: Valves: The Pulmonary Circuit (fig 8b) involves blood flow from the right ventricle lungs left atrium. This flow serves to allow blood to pick up O 2 from lung tissue & release CO 2 into lung tissue. As a result of pulmonary circulation, blood velocity is reduced as it flows through the lung capillaries (small vessel diameter creates high resistance to blood flow). The Systemic Circuit (fig 8b) involves blood flow from the left ventricle all body systems. Blood must return to the heart from the lungs for a second pumping in order to regain its velocity that was lost as it flowed through the lungs = Double Circulation.

7 Figure 10: Heart Cycle Diastole: Systole: Figure 11: Roles of SA & AV Node in Heart Cycle Composed of a special mass of muscle tissue at the top of the right atrium, the SA Node or Pacemaker generates electrical impulses, which spread throughout the heart muscle causing the atria contract in unison in (first.1sec of systole) to completely fill the ventricles. This electrical signal then reaches the AV Node (base of right atrium) which delays this signal for 1.sec before allow it to pass to the apex of the heart, stimulating the ventricles to contract. The delay of this electrical signal at the AV node ensures that the atria contract before the ventricles to maximize the amount of blood the ventricles can send from the heart.