Ms Flecknoe DO NOT eat your Mentos YET!!!

Mentos task: -This is a SILENT task -As you eat your Mentos, I want you to think about the following: -What pathway does the Mentos take? -Where does the Mentos end up? -Write down the pathway in your work- book

Making the link… -During digestion, your Mentos is broken down into smaller components (eg monosaccharides) which can be absorbed by the small intestine. -These nutrients enter the underlying blood stream -The CIRCULATORY SYSTEM allows these nutrients to be delivered to the cells which need them

Chapter 6 Distribution of Materials: The Circulatory System

Roles of the circulatory system:

-To deliver oxygen and nutrients to the cells of the body -To remove carbon dioxide and other waste products (eg urea) -Why is this necessary? -Also involved in transport of hormones, heat and mediators of immune defence.

Circulatory system components: 3 main components: 1______2______3______

Circulatory system components: 3 main components: 1_Blood__ 2 _Blood vessels_ 3_Heart _

Components of blood: -Plasma (mostly water) -Red blood cells -White blood cells -Platelets What colour is blood?

Plasma -Plasma is a straw coloured solution in which blood cells are suspended -Plasma takes up 55% of blood volume -90% of plasma is water (easy to dissolve substrates in) -Other 10% of plasma is made up of nutrients, waste products, oxygen and carbon dioxide, hormones, plasma proteins, antibodies and ions

Cellular components of blood -Red blood cells, white blood cells and platelets all arise from a common STEM cell found in bone marrow

Red Blood Cells (erythrocytes) -Red blood cells (RBC) are bi- concave …they look like a donut without the middle fully punched out! (advantage?) -Contain haemoglobin which allows RBCs to transport large amounts of oxygen to the body -RBCs lack nuclei and mitochondria (advantage?) -Short life span relative to other nucleated cells (only survive for ~120 days)

Red Blood Cells – unique shape -Shape increases surface area to allow rapid diffusion of gases -Shape increases flexibility – RBC can squeeze through tiny blood vessels (capillaries)

RBCs contain Haemoglobin -Haemoglobin GREATLY increases the capacity for blood to carry oxygen 1L of plasma holds 3mL O 2 1L of blood holds 200mL O 2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 Oxyhaemoglobin (haemoglobin bound to oxygen) Deoxy-haemoglobin (not bound to oxygen) Oxygen binds in the lung Oxygen released at the tissues Oxygen binds reversibly to haemoglobin

White Blood Cells -Many different types (basophils, eosinophils, neutrophils and lymphocytes) -These cells have slightly varied functions, but main role is to fight infection. -Can cause inflammation, produce antibodies and phagocytose (eat/engulf) foreign objects. -Only live for a few days Foreign cell White blood cell engulfing foreign cell

Platelets -Platelets are specialized fragments of larger cells -Platelets are responsible for initiating blood clotting in response to vessel damage -Platelets prevent excessive bleeding -Platelets live for about a week

Blood cell lifespan -White blood cells live a few days -Platelets survive for approximately 1 week -Red blood cells survive for approximately 120 days -To replace the dying cells, the body produces ~2,500,000 cells per second!

Question?? Why do we bleed when we cut ourselves?

Vessels transport blood -Three main types of vessels transport blood around the body: 1.Arteries 2.Capillaries 3.Veins -Arterioles are small arteries -Venules are small veins

Arteries -Arteries carry blood away from the heart -In general, arteries carry oxygenated blood (the exception is the pulmonary arteries) -Arteries have thick muscular walls -Thick walls needed to withstand the high pressure of blood as it is pumped from the heart -Walls are too thick to allow diffusion of nutrients and gases -Arteries branch into smaller and smaller vessels. The smallest arteries are called arterioles ArteryArteriole

Arterioles -Muscular walls allow blood to be directed to tissue that needs it most - Examples? -Smooth muscle acts as sphincters to regulate blood flow (pre-capillary sphincters) -Contraction/relaxation is not under voluntary control – ie we can’t deliberately increase blood flow to a certain region – it is controlled by the body -Continued branching of arterioles leads to capillaries ArterioleCapillary

Capillaries -Capillaries are the site of nutrient and gas transfer -Capillaries have a small diameter (5-8µm) – Implications? -Capillaries have very thin walls which are only one cell thick (these cells are called endothelial cells). The thin walls allow substances to diffuse across the capillary to reach the tissue (or vice versa). -Alternatively, larger molecules (eg proteins and white blood cells) can squeeze between the endothelial cells to reach the other side. -Concentration gradients determine the direction molecules (eg nutrients, oxygen, carbon dioxide) will move -Branching of arteries and arterioles leads to very large numbers of capillaries. This leads to large surface area and decreased blood pressure in capillaries– Why is this important?

Veins and venules -Venules are small veins which take blood from the capillaries to the veins -Veins take blood back to the heart -They have thinner walls compared to arteries because they function under low pressure (blood is further from the heart) -Veins generally carry deoxygenated blood (exception is the pulmonary vein) -Many veins are located close to your skin –What colour are they? Why? -Veins lack thick muscular layer and must rely on valves and contraction of nearby skeletal muscle to pump blood back to the heart. -Valves prevent backflow of blood -Contraction of nearby muscles (eg in the leg) squeeze the veins and push blood back to the heart. -Implications for deep vein thrombosis and traveling on aeroplanes?

Bringing it all together… Heart

Summary Function Take large volumes of blood from heart. Under high pressure Connect arteries to capillaries. Role in directing blood flow. Direct blood from capillaries to veins. Take large volumes of blood to heart. Allow diffusion of nutrients and gases to tissues.