transport in mammals

describe a double circulatory system

• birds and most mammals

• blood passes through the heart twice per circuit

• one circuit of vessels carries blood away from heart to lungs for gas exchange: pulmonary circulation

• second circuit carries blood from heart to the rest of the body: systemic circulation

structure & function of arteries

• smooth muscle layer → constriction and dilation to control volume of blood

• elastic layer → maintains blood pressure, walls stretch and recoil in response to heartbeat

• collagen layer → provides structural support

• wall thickness → prevents vessels from bursting due to high pressure

• no valves

structure & function of arterioles

• smooth muscle layer → restrict flow into capillaries

• elastic layer → thinner than arteries as pressure is lower

• collagen layer → thinner

• wall thickness → thinner as pressure is slightly lower

• no valves

structure & function of capillaries

• no smooth muscular layer

• no elastic layer

• no collagen layer

• walls one cell thick to provide a short diffusion distance for exchanging materials between blood and cells

• no valves

structure & function of veins

• smooth muscle layer → relatively thin so cannot control blood flow

• elastic layer → relatively thinner as pressure is much lower

• collagen layer → lots of collagen

• wall thickness → thin as low pressure so low risk of vessel bursting, thinness means vessels are easily flattened, helps flow of blood to heart

• valves are present

structure & function of venues

• smooth muscle layer → thin layer

• elastic layer → none

• collagen layer → none

• wall thickness → very thin, several venues join to form a vein

• valves present

identifying RBCs, monocytes, neutrophils, and lymphocytes

• RBCs: biconcave shaped cell with no nucleus

• monocyte: non-granular cytoplasm and nucleus looks like a kidney bean

• neutrophil: granular looking cytoplasm and nucleus is lobed, looking like a string of beads

• lymphocyte: non-granular cytoplasm with a large, spherical nucleus

how is tissue fluid formed

• blood enters capillaries from arterioles → smaller diameter results in high hydrostatic pressure

• pressure forces water, glucose, amino acids, fatty acids, ions, and oxygen out of capillaries

• this tissue fluid bathes cells in substances they need

hydrostatic pressure

pressure exerted by liquid

oncotic pressure

tendency of water to move into blood by osmosis

how does liquid move out of the capillaries

• hydrostatic pressure is higher than oncotic pressure at arterial end of capillaries

• net movement of liquid is out of capillaries

what happens to remaining liquid

• absorbed into lymphatic system

• eventually drains back into bloodstream near the heart

• once in lymphatic system it is called lymph

how does the affinity of haemoglobin for oxygen change

• as each molecule binds the shape of haemoglobin changes, making the binding of further oxygen molecules easier

• areas with high partial pressure of oxygen (high concentration) the affinity for heamoglobin fro oxygen is high

• in humans, alveoli have a high partial pressure of oxygen

what is the Bohr effect

• A high partial pressure of carbon dioxide results in haemoglobin having a reduced affinity for oxygen.

• Haemoglobin will more readily unload oxygen.

• reduced affinity is caused by change in shape of haemoglobin

3 ways carbon dioxide is transported

1. dissolved in blood plasma

2. as haemoglobonic acid → CO2 reacts reversibly with amino acids in haemoglobin to form haemoglobin acid

3. in cytoplasm of RBCs in the form of hydrogen carbonate ions

What is the chloride shift

• carbonic acid leaves RBCs by diffusion

• in exchange chloride ions diffuse into RBCs

• both ions are negative, so this exchange maintains the electrical balance of RBCs

structure of the heart

• coronary arteries supply cardiac muscle with ATP

• left ventricle has thickest muscular wall

cardiac cycle

• atrial systole is when atria contract: increases pressure in atria, opening atrioventricular valves and forcing blood to flow into ventricles

• ventricular systole is when ventricles contract and aura relax: increases pressure in ventricles, causing atrioventricular valves to shut and semilunar valves to open, therefore blood flows out of ventricles and into the pulmonary artery and aorta

formula for cardiac output

stroke volume x heart rate

what is the rate of heart contraction controlled by

waves of electrical activity

process of heart contractions controlled by electrical activity

• sinoatrial node(SAN) is in right atrium: releases a wave of depolarisation across the atria, causing the cardiac muscle to contract

• atrioventricular node (AVN) is located near the border of right and left ventricles within the atria: releases another wave of depolarisation once first wave has reached it

• non-conductive layer between atria and ventricles prevents wave of depolarisation from travelling down to the ventricles

• bundle of His in septum conducts wave of depolarisation down septum and Purkyne fibres

• muscles in Apex contract first, then walls of ventricles