Adaptations for transport in animals (Arteries and veins (In capillaries…
Adaptations for transport in animals
In an earthworm, blood moves through dorsal vessel, back into the ventral vessel and keep it moving.
Open , blood bathes tissue directly, closed (single, double)
An electrocardiogram (ECG) is the trace of voltage in the heart
suitable medium in which to carry material, a pump, valves (respiratory pigment, system of vessels)
In fish, the ventricle of the heart pumps deoxygenated blood to the gills, which is then carried to the tissues and back to the atrium of the heart.
Pulmonary circulation is to the lungs
systemic circulation is to body tissues
Arteries and veins
Tunica media, containing elastic fibres and smooth muscle. It is thicker in arteries than in veins, in artieries smooth muscle contracts to maintain blood pressure.
Tunica externa, contains collagen which resists over stretching.
Veins contain vaves which prevent backflow of blood when it is returning to the heart.
Veins have larger lumen and thinner walls than arteries.
In capillaries pressure drops as more blood is in contact with the walls of the vessel, meaning there is more friction and the rate of flow drops, as well as this, the large total surface area of the vessels causes a drop in pressure.
Endothelium, innermost layer, one cell thick, surrounded by tunica intima, reducing friction with the blood.
Capillaries have thin walls, only one cell thick(endothelium), small diameter, rate of flow is slow.
The heart consists of cardiac muscle, a specialised tissue with myogenic contraction. It contracts and relaxes rhythmically.
Atrial systole, atrial walls contract and blood is pushed through the bicuspid left and tricuspid valves right into the ventricles.
Ventricular systole, forces blood up through the semi lunar valves out of the heart into the pulmonary artery and the aorta. Pulmonary artery to the lungs and aorta to the body.
Diastole, ventricles and atria relax, blood flows into the atria and the cycle repeats itself.
The wall of the right atrium has a cluster of specialised cells called the Sino-atrial node, acts as a pacemaker. The node produces a wave of electrical stimulation that spreads down across the atria, causing the muscle to contract. The atrio-ventricular node acts as a layer of insulation and prevents the electrical impulse from travelling into the ventricles.
The AVN passes the wave of excitement down the nerves of the bundle of His, to the apex of the heart. This is transmitted to the purkinje fibres in the ventricle walls upwards, causing the muscle to contract from the bottom up, and blood to be forced up and out of the aorta or pulmonary artery.
Red blood cells (erythrocytes) are biconcave discs with no nucleus, maximising area for haemoglobin and therefore oxygen.
Plasma is a pale yellow liquid, mostly water that carries glucose, amino acids, vitamins, waste hormones and distributes heat
Transport of oxygen
Haemoglobin must readily associate with oxygen. It can change it's affinity for oxygen depending on how high the partial pressure of oxygen is by changing it's shape.
The first and the fourth molecule of oxygen take a large partial pressure increase to bind, cooperative binding
Bohr effect , lowers affinity for oxygen
Foetal haemoglobin has a higher affinity for oxygen, lugworms have a higher affinity
carbon dioxide and water react with carbonic anhydrase to form carbonic acid, this dissociates into hydrogen and hydrogen carbonate ion, hydrogen carbonate diffuses out of the cell and chloride ions move in, this is known as the chlorine shift. hydrogen ions cause oxyhaemoglobin to dissociate into oxygen and haemoglobin., haemoglobinic acid is formed and oxygen diffuses out of the cell.
Tissue fluid. Fluid from the plasma is forced through the capillary wall as there is a higher hydrostatic pressure a the arteriole end of the capillary network, because it is closer to the heart. The tissue fluid bathes cells supplying them with glucose, amino acids, oxygen and removes any waste product from the cells
Water moves back into the capillary as so much water was forced out with the plasma by osmosis.
At the venous end osmotic pressure is low as there are a large number of proteins that can't move out so water is forced back in by osmosis, ost tissue fluid moves back into the capillaries but some of them move back into the lymphatic system. It returns through he thoracic duct, which empties it into th left subclavian vein of the heart.