Unit 1 – Unity and diversity AOS 2 – Functioning organisms Chapter 6 Distribution of materials

Transport systems This chapter is designed to enable students to: Identify and give examples of the features of effective transport systems by which living organisms distribute materials Understand the nature of waste products and the excretory mechanisms for removing wastes Appreciate the various ways in which gaseous exchange occurs in multicellular organisms including the process of diffusion

Circulatory system The circulatory systems is the mechanism that transports nutrients and oxygen to all cells of a multicellular organism. The circulatory system consists of: - blood vessels, through which blood is transported - a heart, a muscular pump that keeps the blood moving Blood travels through the heart twice during each circulation of the body: once after circulating through the pulmonary system (the lungs) and once after circulating through the remaining parts of the body.

Figure 6.4 – The main routes for blood circulation – red = oxygenated blood and blue = deoxygenated blood

Components of blood Plasma (55%) Approx 90% water, remaining 10% made up of nutrients, nitrogenous wastes, CO2 and 02, plasma proteins, ions and hormones. Red blood cells (45%) Contains haemoglobin, a red iron-carrying protein that binds with CO2 and O2 to assist with the transport of gases around the body. White blood cells (<0.1%) To combat infection – involved in the immune response to foreign cells invading the body (e.g. through a cut in the skin). Platelets (<0.01%) Specialised fragments of larger cells that play an important role in blood clotting, to stop the flow of blood from an open wound.

Vessels to transport blood Blood is transported around the body in different kinds of vessels: Arteries – thick walled vessels that carry blood away from the heart. They branch into smaller and smaller arteries, with the smallest type of artery called an arteriole. Blood in arteries in of a high pressure due to being pushed away from the heart. Capillaries – thin walled vessels (one cell thick), to allow substances to diffuse into and out of them. Veins – blood moves from the capillaries into venules (small veins) which join together to form larger veins. Veins carry blood to the heart, and because this blood is lower in pressure, the walls of veins do not need to be as thick as those of arteries.

Figure 6.8 – A capillary bed branching from an arteriole and ultimately feeding into a venule. Figure 6.9 – The relationship between capillaries, tissues and lymphatics.

The heart The heart acts like a pump to keep the blood constantly flowing through the body. Each beat brings blood into the one chamber of the heart and expels blood from another chamber into an artery. The mammalian heart has four chambers: - left atrium - left ventricle - right atrium - right ventricle

Inside the heart Each side of the heart has two chambers, and atrium and a ventricle Atria (singular = atrium) blood is brought to the atrium via a vein thin walled, blood inside of a lower pressure than ventricles right atrium receives deoxygenated blood from the body left atrium receives oxygenated blood from the lungs Ventricles have thick muscular walls, pump blood out of the heart to an artery right ventricle pumps deoxygenated blood to the lungs left ventricle pumps oxygenated blood to the body. blood leaves the ventricle via a vein

Major veins and arteries Pulmonary artery – receives deoxygenated blood from the right ventricle and carries it to the lungs Pulmonary vein – brings oxygenated blood from the lungs to the left atrium Aorta (artery) – receives oxygenated blood pumped from the left ventricle to be distributes throughout the body Vena cava (vein)– receives deoxygenated blood from the body –Inferior vena cava comes from the trunk and legs –Superior vena cava comes from the head, upper torso and arms Valves separate the atrium from the ventricle in each side of the heart and prevent backflow of blood (keep the blood moving in the right direction) tricuspid valve – right side of heart; bicuspid valve – left side of heart

Different circulatory systems Closed circulatory systems Blood remains within vessels as it is transported around the body. All closed circulatory systems have: - blood - a pumping organ, known as a heart, that forces the blood through the system Different groups of animals have different hearts Figure 6.20 – Circulatory systems of different groups of vertebrates

Open circulatory systems The blood is contained within vessels for some of the time, leaves the vessels to bathe in the tissues, then returns to the vessels. When the blood bathes in the tissues, CO2 from the tissues is exchanged for O2, and then the deoxygenated blood moves back to the vessels where it can be reoxygenated. E.g. Insects Figure 6.21 – An insect has an open circulatory system. Blood bathes the internal organs, enters the heart, is pumped into the aorta, then out of the aorta to surround the tissues again.

The lymphatic system The lymphatic system is made up of a special series of blind ending vessels, that carry fluid including protein, dissolved gases and white blood cells. The lymphatic system plays an important role in an immune response, carrying detected foreign cells back to lymph nodes, where they are destroyed and digested by various types of white blood cells. The lymphatic system has no heart to act as a pump, but it has valves to prevent back flow. Muscular movements and breathing action helps move lymph through the lymphatic system. Figure 6.22

Figure 6.23 – The lymphatic system in the human body

Transport of nutrients Plasma of the blood transports nutrients in all living cells. These nutrients are the products of digestion in which enzymes break down large organic molecules (fats, polysaccharides, proteins) into much smaller subunits that are able to cross the plasma membrane of a cell. Figure 6.24 – Summary of breakdown of organic compounds during digestion

Simple sugars Cross the membrane of the cells lining the gut and are absorbed in capillaries in the gut villi. They are they carried to the liver. If there is sufficient glucose present in the body at that time, any excess glucose will be converted to glycogen, and stored in the liver. Amino acids The digestion of proteins produces amino acids. AA’s are transported to the liver and then moved into the blood stream where they are transported around the body for use. Lipids Fatty acids and glycerol are produced from fat digestion. Transported to the liver.

Complete Quick-check questions 1-3 on page 136. Complete Quick-check questions 4-10 on page 142. Figure 6.42 – Organic compounds broken down during digestion

Transport of gases Different groups of organisms have different processes and organs for gaseous exchange – whereby CO 2 (waste product of cellular respiration) is exchanged for O 2 (reactant required). Blood transports O 2 to cells and CO 2 away from these cells. The system responsible for gas exchange is the respiratory system. Mammals, reptiles, birds and amphibians have lungs Fish have gills Insects have trachea

Movement of gases Air is breathed in through the nose and mouth – where these two passages connect is called the pharynx. Air then moves through the larynx (voice box), down the trachea (wind pipe) and into the lungs – see below.

Air then moves down the trachea into two bronchi (singular = bronchus). Each bronchus goes into the lobe of a lung, and branches into smaller and smaller tubes called bronchioles (see below for order) The passage of air from the outside into the lungs follows the sequence below:

Gas exchange The lungs are specialised two-way gas exchange organs – whereby the waste CO 2 from the body is exchanged for fresh O 2 from the air breathed in. The CO 2 is then breathed out in the opposite way. The red cells carry oxygen and carbon dioxide around the body. In the lungs, the red blood cells get rid of the CO 2 into the alveolus and the O 2 from the alveolus is transferred throughout the thin capillary wall into the blood stream and is picked up by red blood cells. This gas exchange occurs through the process of diffusion.

Gills: gas exchange in fish Fish exchange gas differently as they live in water. The water moves into the fishes mouth and then over the gills, which are made of many lamella, which contain capillaries – where the CO 2 from the body is exchanged with the O 2 from the water.