Open Circulatory System. Closed Circulatory System

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1 General Types of Circulatory Systems -All circulatory systems exchange gases, nutrients, and wastes at the cellular level -Although all animals need to do this, they do so in a variety of ways: -Two types of circulatory systems are: ---Open circulatory systems ---Closed circulatory systems Structures of the Circulatory System -A circulatory system has three components: -Blood (a circulatory fluid) -Vessels (tubes through which blood moves) -Heart (structure that pumps the blood) Open Circulatory System -Blood and lymph bathes the organs directly for nutrient/waste transfer -The blood and lymph combined are called hemolymph -The heart pumps hemolmph into cavities called sinuses, where the organs are -Blood vessels are not used for transport ***Found in arthropods and most mollusks. Closed Circulatory System -Blood is contained within vessels and pumped around the body -The blood is separate from the interstitial fluid/lymph -Seen in annelids, cephalopods and all vertebrates

2 Blood Vessels -Arteries -Capillary -Veins Arteries -Carry blood away from the heart and branch into smaller arterioles -Their walls are relatively thick, flexible, and include a significant amount of smooth muscle -The pulse is felt in an artery Capillaries -Are microscopic vessels that are composed of only a single layer of cells (the endothelium) on a basement membrane -All gas diffusion (O 2 /CO 2 ) occurs here. Veins -Carry the blood back to the heart -They use skeletal muscles to help push blood back up to the heart and have valves to prevent backflow

3 The Heart -Atria are heart chambers that receive blood from blood vessels -Ventricles are heart chambers that receive blood from the atria -Amphibians have a 3 chambered heart with a single large ventricle -Reptiles have a 3 chambered heart with a septum partially dividing the single ventricle -Mammals and birds have a 4 chambered heart Blood Flow in Mammals Steps 1-6 Blood Flow in Mammals Steps 7-10 The Cardiac Cycle 1.Blood is pumped from the right ventricle. 2.It enters the pulmonary arteries and is carried to the lungs. 3.The blood flows through capillary beds in the lungs and picks up oxygen and releases carbon dioxide. 4.The blood returns via pulmonary veins to the left atrium of the heart. 5.Then it continues to the left ventricle. 6. It leaves the heart via the aorta, which branches off and sends blood through arteries throughout the body. 7.The blood enters capillary beds all over the body, giving up oxygen and picking up carbon dioxide. 8. The capillaries form venules, and blood from the neck, head, and arms travels back to veins and then back to the right atrium via the superior vena cava. 9.Blood from the legs and trunk travels through the infererior vena cava to the right atrium. 10. Blood is pumped into the right ventricle and the cycle begins again. -The cardiac cycle is the complete cycle of contraction and relaxation of the heart -The contraction phase is called systole and the relaxation phase is called diastole.

4 The Heart Heart Rate Blood Pressure Movement of Blood -The atrioventricular (AV) valve between each atrium and ventricle prevents the backflow of blood into the atria -There are also two semilunar valves -One is located at the entrance to the pulmonary artery and the second at the entrance to the aorta. -They prevent backflow of blood into the ventricles -The sinoatrial (SA) node is the pacemaker of the heart. It is located in the upper wall of the right atrium. It sets the rate at which cardiac muscle cells contract -Is the rate of contraction per minute (pulse). -Stroke volume is the amount of blood pumped by the left ventricle during each contraction. Regulation of Blood Pressure: -The sympathetic nerves accelerate heart rate -The parasympathetic nerves decelerate heart rate -Hormones such as epinephrine increase heart rate -An increase of body temperature increases heart rate. -Is measured with a spyghmomanometer -For a healthy 20 year old at rest, typical blood pressure is 120/80 -The first number is the systolic pressure (when the heart contracts), the second is the diastolic pressure (when the heart relaxes) -Short term regulation of blood pressure occurs when the smooth muscle of the blood vessel contracts or relaxes -Long term regulation of blood pressure is accomplished by changes in blood volume due to hormonal signals -Blood moves through the veins and venules as rhythmic contractions of smooth muscles in the walls propel it, and it is squeezed by contraction of skeletal muscles during exercise. Valves prevent backflow

5 Movement of Lymph -The lymphatic system is responsible for returning lost fluid and proteins to the blood in the form of lymph. Along a lymph vessel are lymph nodes that filter lymph and attack viruses and bacteria, playing an important role in immunity Blood Components Fibrinogen -Plasma is mostly water, but it also contains ions, electrolytes, and plasma proteins -It transports nutrients, metabolic wastes, gases and hormones -Red blood cells (erythrocytes or RBCs), which transport oxygen via hemoglobin (an ironcontaining protein) -White blood cells (leukocytes or WBCs), which are part of the immune system -Platelets which are fragments of cells responsible for blood clotting -Blood contains a soluble plasma protein called fibrinogen, which helps platelets form clots when it is converted to its active form, fibrin The Red Blood Cell -Are biconcave disks. This shape increases surface area to enhance oxygen transport -Each RBC contains about 250 million molecules of hemoglobin, and each hemoglobin molecule can bind up to 4 molecules of O 2. So each RBC can carry up to a billion molecules of oxygen! -RBCs lack nuclei, which increases space for hemoglobin and mitochondria, so the oxygen they carry is not consumed. -All blood components (RBCs, WBCs, and platelets)develop from stem cells found in red marrow of flat bones (ex. sternum, ribs and pelvis).

6 Gas Exchange occurs across specialized Respiratory Surfaces -Gas exchange, or respiration, is the uptake of molecular oxygen (O 2 ) from the environment and the discharge of carbon dioxide (CO 2 ) to the environment. Although all animals need to do gas exchange, they do so in a variety of ways. -The diffusion of a gas depends on partial pressure. -Gases always diffuse from regions of higher partial pressure to regions of lower pressure. Gas Exchange Continued -The respiratory medium is the source of the O 2. It is air for terrestrial animals and water for most aquatic animals. -Water holds less oxygen than an equivalent volume of air, and is more dense and viscous. Therefore, aquatic animals expend considerable energy to carry out gas exchange. The amount of dissolved O 2 in water decreases as temperature or salinity increases. Respiratory Surfaces -The respiratory surface is the part of an animal s body where gases are exchanged with the surrounding environment. It can be the body wall (sponges), the skin (annelids, amphibians), gills (mollusks, fish), tracheae (insects), or lungs (terrestrial vertebrates). General characteristics of respiratory surfaces include: -Must be moist -Favorable surface area/volume ratio. Respiratory surfaces are often extensively folded or branched. (Think structure/function) -Closely associated with the vascular system of larger animals.

7 Gills Tracheal Systems -Are respiratory organs in aquatic animals. -Water flows through them, and blood flowing through capillaries within the wall of the gill picks up oxygen from the water. Blood flows in a direction opposite to the flow of water. This is called countercurrent exchange, and it maximizes the absorption of oxygen. -Countercurrent exchange mechanisms allow for more diffusion to occur than would otherwise be possible -Insects have tracheal systems, which are made up of air tubes that are open to the outside air and branch through the body extending to almost all cells Lungs -Lungs are infoldings of the body surface and are found in most terrestrial vertebrates Larynx -The larynx (voice box) is the upper part of the respiratory tract. It is a tube with cartilagereinforced walls that leads to the trachea (windpipe)

8 Trachea -The trachea divides into two bronchi, each of which leads to a lung. -Cilia and mucus-producing cells line the trachea, and their action keeps particulate matter from reaching the lungs. -The trachea has C-shaped cartilage rings, which keep it from collapsing, much like the reinforcements in a vacuum cleaner s hose. Bronchi -In the lungs, the bronchi branch into bronchioles -The alveoli are air sacs clustered at the ends of bronchioles -They are thin, moist, and have a large surface area -In a human, they would be the size of a tennis court if spread out, like the small intestine Alveoli Breathing Ventilates the Lungs -Air sacs clustered at the ends of bronchioles. -They are thin, moist, and have a large surface area -In a human, they would be the size of a tennis court if spread out, like the small intestine -They are associated with capillary beds. Here O 2 diffuses into the blood by passing through the simple squamous membrane of an alveolus and through the simple squamous membrane of a capillary, into the blood, and attaches to a hemoglobin molecule in a red blood cell -Breathing is the inhalation and exhalation of air that ventilates lungs -In mammals, breathing involves movement of the diaphragm, a dome shaped muscle separating the thoracic cavity from the abdominal cavity -Lung volume increases when the rib muscles and diaphragm contract, pressure within the lungs decreases, and air flows into the lungs -During exhalation, lung volume is decreased as the diaphragm relaxes and moves up, and pressure within the lungs increases, forcing the air out

9 Breathing -Breathing is under the control of regions located in the brain called the medulla and the pons. It is influenced by ph, which is an indirect indication of blood CO 2 levels -Increased metabolic activity lowers ph by increasing the concentration of CO 2 in the blood. CO 2 reacts with water to form bicarbonate (and protons), which changes the ph, and signals the brain to cause changes in breathing when the ph changes until it returns to normal Increased Metabolic Activity Formula CO 2 + H 2 O H 2 CO H + Carbon dioxide water Bicarbonate ion proton (lowers ph) Adaptations for Gas Exchange include Pigments that bind and transport Gases Pigment in Vertebrates -CO 2 is most commonly carried in the blood in the form of bicarbonate ions and protons in the plasma -Carbonic anhydrase is an enzyme found in RBCs that catalyzes the change of CO 2 in the blood to bicarbonate ions and protons -As blood ph changes because of the buildup of bicarbonate (and protons), it signals the brain to increase the rate and depth of respiration to lower CO 2 content until the ph returns to normal (negative feedback) -Hemoglobin is the respiratory pigment found in almost all vertebrates -Along with DNA, RNA and proteins, this is another example of a molecular homology among vertebrates