Biology, 9th ed, Sylvia Mader Chapter 34 Circulatory Systems

Transport in Vertebrates Transport in Humans Outline Transport in Vertebrates Transport in Humans Heartbeat Vascular Pathways Blood Pressure Blood Components Clotting Transport in Invertebrates Open versus Closed Circulatory Systems

Transport in Humans Human Heart Cone-shaped Size of a fist-14cm long and 9cm wide Inner surface is lined with endocardium Thick muscular organ (special cardiac fibers)-myocardium Lies within the pericardium, a thick membranous sac that secretes a lubricating liquid.

Thoracic cavity

Heart-lies behind the sternum and between lungs.

External Heart Anatomy

Human cardiovascular system includes two major circular pathways: Vascular Pathways Human cardiovascular system includes two major circular pathways: Pulmonary Circuit Takes oxygen-poor blood to the lungs and returns oxygen-rich blood to the heart Systemic Circuit Takes blood throughout the body from the aorta to the vena cava

Path of Blood

Human Heart: Gross Anatomy Septum separates heart into left & right halves The heart has four chambers Upper two chambers are the atria Thin-walled Receive blood from circulation Lower two chambers are the ventricles Thick-walled Pump blood away from heart

Valves open and close to control blood flow through heart Human Heart: Valves Valves open and close to control blood flow through heart Atrioventricular valves (between the atria and ventricles Tricuspid Bicuspid Semilunar valves (between the ventricles and their attached vessels) Pulmonary Aortic

Internal View of the Heart

Cross-section of the heart

Transport in the Vertebrates All vertebrates have a Closed Circulatory System Heart pumps blood to capillaries Gases and materials diffuse to and from nearby cells Vessels return blood to heart without it contacting tissues Oxygen-poor blood never mixes with oxygen-rich blood (in humans) Vertebrate vessels: Arteries - Carry blood away from heart Arterioles – Lead to capillaries Capillaries - Exchange materials with tissue fluid Venules - Lead to veins Veins - Return blood to heart

Transport in Humans Blood returning to heart from systemic circuit Enters right atrium Right atrium pumps through tricuspid valve to right ventricle Right ventricle pumps blood through pulmonary valve to the pulmonary circuit Blood returning to heart from pulmonary circuit Enters left atrium Left atrium pumps through mitral valve to left ventricle Left ventricle pumps blood through aortic valve to the systemic circuit

Blood Flow Through the heart

Cardiac Cycle-70 beats/min 100,000 x a day or 40 million x a year A single cardiac cycle is made up of the events associated with one heart beat. Each cardiac cycle takes about 8 tenths of one second. During each cardiac cycle pressure changes occur within the chambers of the heart as they relax and contract. As the chambers relax, they fill with blood, diastole. When the chambers contract, this is called systole.

Cardiac cycle When the AV-opens-blood flows into the ventricles from the atria (semilunar valves are closed). Atrial contraction results from a series of events beginning with the spread of nerve impulses from the SA-node across the walls of the atria. Ventricular filling is completed by atrial systole. Impulses from the AV-node travels along the ventricular conduction fibers leading to contraction of the ventricles.

Heartbeat In ventricular systole, increased pressure forces the AV valves closed, “Lub” semilunar valves open and blood is ejected from the ventricles. Ventricular diastole, pressure in the ventricles decrease and blood in the aorta and pulmonary flows back toward the chambers, causing these valves to close “dub”. Ventricular pressure falls below that of the atria, AV valves open and cycle begins again.

Heartbeat P- Atrial depolarization/systole Electrocardiogram (ECG) Fluids contain ions that conduct electrical currents, electrodes placed on the skin are connected to a instrument that detects electrical changes of the myocardium. P- Atrial depolarization/systole QRS- Ventricular depolarization T-wave- Ventricular repolarization

Conduction System of the Heart

One way venous valves During muscle contraction, venous diameter decreases, and venous pressure rises. The increase in pressure forces the flow toward the heart.

Cross Section of a Valve in a Vein

Skeletal muscle contraction pushes blood in the veins toward the heart Blood Pressure The beat of the heart supplies pressure that keeps blood moving in the arteries Systolic Pressure results from blood forced into the arteries during ventricular systole Diastolic Pressure is the pressure in the arteries during during ventricular diastole Skeletal muscle contraction pushes blood in the veins toward the heart Blood pressure Normally measured with a sphygmomanometer on the brachial artery Expressed in the form: Systolic “over” Diastolic

Transport in Invertebrates Small aquatic animals with no circulatory system May rely on external water in gastrovascular cavity to service cells Roundworms and other pseudocoelomates Use a fluid-filled body cavity as a means of transporting substances Fluid-filled cavity can also act as a hydrostatic skeleton Animals that have a rigid skeleton May still rely on body fluids for the purpose of locomotion Bivalves pump hemolymph into the foot for digging into mud

Aquatic Organisms Without a Circulatory System

Open vs. Closed Invertebrate Circulation Two types of circulatory fluids: Blood - contained within blood vessels Hemolymph - flows into hemocoel Open Circulatory System Heart pumps hemolymph via vessels Vessels empty into tissue spaces

Open vs. Closed Circulatory Systems

Transport in Birds and Mammals

Comparison of Circulatory Circuits in Vertebrates

Comparison of Circulatory Pathways Fish - Blood flows in single loop Single atrium and single ventricle Amphibians - Blood flows in double loop Two atria with single ventricle Other vertebrates - Blood flows in a double loop Heart divided by septum into separate sides

Blood: Homeostasis Functions Transports substances to and from capillaries for exchange with tissue fluid Guards against pathogen invasion Regulates body temperature Buffers body pH Maintain osmotic pressure Clots prevent blood/fluid loss

Lack a nucleus and contain hemoglobin Red Blood Cells Small, biconcave disks Lack a nucleus and contain hemoglobin Hemoglobin contains Four globin protein chains Each associated with an iron-containing heme Manufactured continuously in bone marrow of skull, ribs, vertebrae, and ends of long bones

Most types larger than red blood cells White Blood Cells Most types larger than red blood cells Contain a nucleus and lack hemoglobin Important in inflammatory response Neutrophils enter tissue fluid and phagocytize foreign material Lymphocytes (T Cells) attack infected cells Antigens cause body to produce antibodies

Composition of Blood

Blood clot consists of: Platelets Platelets Result from fragmentation of megakaryocytes Involved in coagulation Blood clot consists of: Red blood cells All entangled within fibrin threads

Blood Clotting

Capillaries very narrow – Tiny RBCs must go through single file Capillary Exchange Capillaries very narrow – Tiny RBCs must go through single file Wall of capillaries very thin to facilitate diffusion of nutrients, gasses and wastes Oxygen and nutrients exit a capillary near the arterial end Carbon dioxide and waste molecules enter a capillary near the venous end

Capillary Exchange

Capillary Bed

Transport in Invertebrates Transport in Vertebrates Review Transport in Invertebrates Open versus Closed Circulatory Systems Transport in Vertebrates Transport in Humans Heartbeat Vascular Pathways Blood Pressure Cardiovascular Disorders Blood Components Clotting

Biology, 9th ed, Sylvia Mader Chapter 34 Circulatory Systems