Chapter 42 Internal Transport

Diffusion Small, simple invertebrates Sponges, cnidarians, and flatworms

Invertebrates with no circulatory system

Specialized circulatory system Larger animals Blood Heart System of blood vessels Spaces through which blood circulates

Interstitial fluid Tissue fluid between cells Brings oxygen and nutrients into contact with cells All animals

Open circulatory system Arthropods and most mollusks Blood flows into a hemocoel Bathes the tissues directly

Closed circulatory system Some invertebrates All vertebrates Blood flows through a continuous circuit of blood vessels

Closed circulatory system

Vertebrate circulatory system Muscular heart Arteries Capillaries Veins

Vertebrate circulatory system Transports nutrients, oxygen, wastes, and hormones Helps maintain Fluid balance Appropriate pH Body temperature Defends body against disease

Plasma Water Salts Substances in transport Plasma proteins Albumins Globulins Fibrinogen

Blood components

Red blood cells (erythrocytes) Transport oxygen and carbon dioxide Produce large quantities of hemoglobin Red pigment that binds with oxygen

White blood cells (leukocytes) Defend the body against disease organisms Agranular white blood cells Lymphocytes Monocytes

Granular white blood cells Neutrophils Eosinophils Basophils

Platelets Patch damaged blood vessels Release substances essential for blood clotting

Blood clotting Damaged cells and platelets release substances that activate clotting factors Prothrombin is converted to thrombin

Thrombin catalyzes the conversion of fibrinogen to an insoluble protein, called fibrin Fibrin forms long threads that form the webbing of the clot

Blood clotting

Arteries Veins Carry blood away from the heart Return blood to the heart

Arterioles Constrict (vasoconstriction) Dilate (vasodilation) Regulate blood pressure and distribution of blood to the tissues

Capillaries Thin-walled exchange vessels through which blood and tissues exchange materials

Blood flow through a capillary network

Vertebrate heart One or two atria One or two ventricles Receive blood Pump blood into the arteries

Fish heart Single atrium and ventricle Part of a single circuit of blood flow

Terrestrial vertebrates Complex circulatory systems separate oxygen-rich from oxygen-poor blood Allows the higher metabolic rate needed to support an active terrestrial lifestyle

Amphibians Two atria and a ventricle Blood flows through a double circuit Oxygen-rich blood is partly separated from oxygen-poor blood

Most reptiles Wall that partly divides the ventricles, minimizing the mixing of oxygen-rich and oxygen-poor blood

Birds and mammals Four-chambered hearts separate oxygen-rich blood from oxygen-poor blood

Human heart Enclosed by a pericardium Valves that prevent backflow of blood

Right atrioventricular (AV) valve (tricuspid valve) Between right atrium & ventricle Mitral valve Between left atrium and ventricle Semilunar valves Guard the exits from the heart

Human heart

Cardiac muscle fibers are joined by intercalated discs The sinoatrial (SA) node (pacemaker) initiates each heartbeat A specialized electrical conduction system coordinates heartbeats

Cardiac cycle One complete heartbeat Contraction occurs during systole Period of relaxation is diastole

Beginning of ventricular systole Closing of the AV valves Low-pitched “lub” sound Beginning of ventricular diastole Closing of the semilunar valves Short, loud, sharp “dup” sound

Cardiac output (CO) Stroke volume times heart rate Stroke volume depends on venous return and on neural messages and hormones, especially epinephrine and norepinephrine

Starling’s law of the heart The more blood delivered to the heart by the veins, the more blood the heart pumps

Heart rate Regulated mainly by the nervous system Influenced by hormones and body temperature

Blood pressure Force blood exerts against the inner walls of the blood vessel Greatest in the arteries Decreases as blood flows through the capillaries

Blood pressure depends on Cardiac output Blood volume Resistance to blood flow

Peripheral resistance Resistance to blood flow Blood viscosity Friction between blood and blood vessel wall

Blood pressure

Baroreceptors Sensitive to blood pressure changes Send messages to the cardiac and vasomotor centers in the medulla of the brain

When blood pressure increases Cardiac center stimulates parasympathetic nerves that slow heart rate Vasomotor center inhibits sympathetic nerves that constrict blood vessels Blood pressure is reduced

Angiotensin Aldosterone Hormone that raises blood pressure Helps regulate salt excretion Affects blood volume and blood pressure

Pulmonary circulation Systemic circulation Connects heart and lungs Systemic circulation Connects heart and tissues

Pulmonary circulation Right ventricle pumps blood into the pulmonary arteries, one going to each lung Blood circulates through pulmonary capillaries in the lung Blood is conducted to the left atrium by a pulmonary vein

Systemic circulation Left ventricle pumps blood into the aorta Aorta branches into arteries leading to the body organs Blood flows through capillary networks within various organs

Blood flows into veins that conduct it to the superior vena cava or inferior vena cava Blood returns to the right atrium

Systemic and pulmonary circulation

Coronary arteries Hepatic portal system Supply the heart muscle with blood Hepatic portal system Circulates nutrient-rich blood through the liver

Lymphatic system Collects interstitial fluid Returns it to the blood Plays an important role in homeostasis of fluids Defends body against disease Absorbs lipids from the digestive tract

Lymph Lymphatic vessels Formed from interstitial fluid Conduct lymph to the thoracic duct and right lymphatic duct in the shoulder region Ducts return lymph to the blood circulatory system

Lymphatic capillaries