5.2. Transport Flashcards
Systemic circulation description:
Oxygenated blood goes from LV into the aorta and from there into head and the body. The arteries that carry blood to the head are called carotid arteries. In the body tissue, blood loses O2 and gains CO2. Deoxygenated blood goes back into the heart via veins, specifically superior vena cava from the head and inferior vena cava from the body and into the RA.
Pulmonary circulation description:
Deoxygenated blood goes from the heart’s RV into lungs via pulmonary artery. In the lungs, blood loses CO2 and gains O2. Oxygenated blood goes from lungs into the heart by the pulmonary vein and into the LA
Heart anatomy and adaptations to function:
Atria – collecting chambers with thin myocardium, gradually fill with blood, pump blood intro ventricles
Ventricles – pumping chambers with thick myocardium (especially left V), pump blood into arteries (stronger contractions because they pump blood out farther than atria, especially LV)
Septum – separating the two halves to prevent blood from mixing (would cause constant lack of oxygen in the body) - the right side of the heart carries deoxygenated blood and the left oxygenated
Valves – atrioventricular and semilunar, ensure that blood circulates by preventing backflow
Cardiac muscle (myocardium) – special property of contracting on its own without being stimulated by a nerve (myogenic contraction)
Coronary vessels – the many capillaries in the muscular wall of the heart supply O2 and glucose for aerobic CR and remove waste products, blood running though them is supplied by coronary arteries and removed by coronary veins
Pacemaker (sinoatrial node) – region of specialized cardiac muscle cells in the wall of the right atrium hat initiated each contraction
Layers of blood vessel wall in arteries vs veins plus extra adaptations (lumen, valves…)
Arteries:
1) Tunica externa: tough outer coat with collagen fibres (produced by fibroblasts) to prevent aneurysm (bulging outwards) or bursting due to high blood pressure
2) Tunica media: thick layer of circular smooth muscle and elastic fibres (elastin) to help pump blood by transmitting the pulse, accommodates to large (and variable) V of blood
Smooth muscles make the lumen narrower (vasoconstriction) and wider (vasodilation)
3) Tunica intima – inner surface is corrugated (smooth endothelium to reduce resistance of blood flow) plus a layer of elastic fibres in some arteries
- Pulsatile (especially further down in the body), narrow lumen (maintaining high pressure and sufficiently fast flow), regular circle cross section
Veins
1) Tunica externa: thin and tough outer coat since there is no danger of it bursting but still want to prevent leaks
2) Tunica media: thinner layer of muscles and some elastic or collagen fibres as blood flow is not pulsatile
3) Tunica intima – smooth endothelium to reduce resistance (friction) of blood flow
- Wide lumen to accommodate blood flowing slowly, one-way valves to prevent backflow due to gravity, cross section elongated
Adaptations of capillaries for the exchange of materials
1) Capillary wall is one layer of flat endothelial cells (short diffusion distance, SA large)
2) Surrounded by the basement membrane (extracellular protein serving as filtration barrier, preventing larger molecules from entering and exiting)
3) Pores between cells enable some of the plasma to leak out and form tissue fluid Fenestration (fenestrated endothelium) is when the pores between cells are larger than normal in tissues whose main function is exchange of materials (e.g. kidney tissue).
4) Narrow lumen – fit into narrow spaces, makes blood flow very slowly (cells flow in one file) to ensure thorough exchange of materials
5) Density of capillary network depends on tissues’ metabolic demands (bone vs lungs/small intestine)
6) Substances provided to tissue by capillaries are O2, food molecules and hormones (enzymes) and substances dissolved in tissue fluid that goes into capillaries are CO2 and other waste products (detoxified by liver or excreted by lungs or kidneys)
Composition of blood
55% plasma, 45% cellular components: Erythrocytes, leukocytes (fight infection), platelets (cell fragments that heal wounds and cause blood clotting), plasma (water with dissolved substances)
Substances dissolved in plasma:
1) CO2, O2, salts, urea (product of a-a digestion)
2) glucose, a-a (nutrients)
3) hormones
4) heat (due to high heat capacity of water)
5) plasma proteins like albumin, fibrinogen and antibodies (globulins)
Myocardium
Cardiac muscle is a striated muscle but controlled by autonomic nervous system
Blood flow inside the heart description (vessel names, valves)
Blood from the body fills the RA by vena cava and blood from lungs the LA by pulmonary vein. They push the blood into RV and LV respectively by weak contractions (high pressure from atriums keeps atrio-ventricular valves open so that blood can pass through). Once the blood is in ventricles the AV valves close to prevent backflow. Ventricles, once they contract more powerfully, pump the blood into aorta and pulmonary artery respectively (high pressure from ventricles keeps semi-lunar valves open so that blood can pass through). Once the blood is in arteries the SL valves close to prevent backflow.
How is tissue fluid formed? How is lymph formed?
As a result of pressure filtration which means that some components of blood plasma were pushed through the membrane into tissue fluid due to the “high” pressure in capillaries and this excess of tissue fluid drains into the lymphatic system
Extra waste from tissue fluid (3/14 litres – molecules that are too large to pass though capillary wall, e.g. pathogens) is drained into lymphatic vessels, if it wasn’t, it would cause swelling (oedema)
Lymph flow, lymph vessels adaptations
From tissue fluid to vessels, small lymphatic vessels merge into larger vessels and then flow into a lymphatic node, all lymph is returned to the blood circulation through two large lymphatic ducts which merge with the right and left subclavian veins
Not pulsatile (no muscles surrounding them), much larger than blood vessels (larger lumen) and have one-way valves
Cardiac cycle
Repeating sequence of actions in which the heart chambers contract and relax in a coordinated manner to send blood around the circulatory system. One cycle = diastole and systole (A and V contraction) = 0.8s
Describe phases of the cardiac cycle (pressure, contractions, valves, blood movement)
- phase – atrial systole
Atria contract, pressure in atria increases, blood is pushed from atria to ventricles, AV valves are open, SL valves are closed - phase – ventricular systole
ventricles contract, pressure in ventricles rises, blood is pushed from ventricles into arteries, AV valves are closed, SL valves are opened - phase – diastole
heart muscle is relaxed, SL valves are closed, when p(ventricles) < p (atria) AV valves open and blood spontaneously fills ventricles, blood starts filling the ventricles, next cardiac cycle starts when atria contract again
Different types of pulses, what is actually pulse?
Radical pulse at wrist or carotid pulse on the neck – systolic blood pressure
What is heart muscle in terms of origin of its contractions? Describe the process of a atrial and ventricular contractions regarding transmission of a nerve impulse.
Myogenic which means that heartbeat is initiated within the heart muscle itself (no nerve impulse from CNS is required). Each heartbeat is initiated by SA node (pacemaker) which sends an electrical impulse that causes atrial contraction (75 beats per minute, independent of activity). These impulses are prevented from spreading immediately into ventricles (short delay which ensures that all blood is transferred from atria), they are transmitted to the ventricles by AV node and a layer of fibrous, isolated bundles that lead to the heart apex. This gives atria time to pump blood into the ventricles before they contract. Nerve impulses from the medulla of the brain together with hormones (e.g. epinephrine) can speed up or slow down the heartbeat (activity, sleeping, etc.)
