B.3.2. Flashcards
(17 cards)
Capillary structure
Capillaries are micro vessels that function as a site for material exchange between the blood and the tissues. Their structure is made up of:
- Pericytes: these are cells that wrap around small blood vessels to help maintain vascular integrity
- Blood plasma: the liquid component of blood that carries nutrients, hormones, water, and other substances throughout the body.
- Basement membrane: a matrix of proteins that forms a gel that acts like a filter to regulate the passage of substances between the blood and tissues, and anchors the endothelial cells on the capillary wall to the surrounding tissues.
- Endothelial cells: cells that form the thin wall of the capillary
- Red blood cells: cells that contain haemoglobin for oxygen transport.
- Fenestrations: are pores in the capillaries that allow for larger molecules in the plasma to come out, increasing the permeability. These gaps allow for faster exchange.
- Capillaries are thin and have a small lumen for better gas and material exchange but branch to increase surface area and decrease pressure.
Artery structure
Arteries are vessels that take blood away from the heart under high pressure. They have the following structure:
They have the tunica interna, the layer in the artery that lines the lumen that provides a smooth surface for blood f low with low resistance.
Then there the tunica media, the middle layer and thickest layer.
In the tunica media they have a thick wall of smooth muscle to sustain the pressure of blood travelling in them by contracting and relaxing to adjust the diameter of the artery lumen, this regulates blood flow and pressure. In the muscles there is a protein called elastin that creates an elastic effect that allows for the vessel to expand and recoiled. During systole the wall of the artery push forward to widen the lumen for influx of blood (vasodilation), then once the pressure lowers in diastole the vessels recoil (vasoconstriction).
Lastly there is the tunica externa that has connective tissue with varying amounts of collages and elastin. Collagen provides structure and tensile strength allowing arteries no to break or bulge, it also maintains the shape of the artery as well as anchors arteries to nearby tissues.
Vein structure
Veins are blood vessels that bring blood into the heart under low pressure. They have valves to prevent back flow of blood in the low pressure, they have wider lumen for low blood pressure, and they have thin smooth muscle walls will little elastin on collagen. Lastly, their placement in skeletal muscle tissues allows for an aid in the circulation of blood, when the skeletal muscles contract they increase the pressure in the veins and force blood upwards towards the heart.
Pulse rate
The heart cycle is measured by pulses, in beats per minute. Every time the heart beats and the arteries expand on certain points on the body it can be felt, and pulse rate can be measured. Digitally there are tools that measure pulse rate with how much light is absorbed due to the change of blood volume depending of the cardiac cycle stage. There are numerous factors that affect pulse rate such as age, exercise, medication, temperature, and heart conditions. The average beats per minute in an adult is 70.
Occlusions
Occlusions are blockages of blood vessels, there are 3 different main causes for occlusions:
Atherosclerosis which is the accumulation of plaque in an artery (plaque being a substance made of cholesterol, fat, cellular debris, calcium deposits, and a clotting protein called fibrin.
Thrombosis which is a clot of platelets, red blood cells, and fibrin. Thrombi form when the vessel wall is damaged and clotting mechanisms are activated.
Embolisms are when a thrombi breaks off and the clot begins travelling through the blood, these can get stuck in smaller vessels and block blood flow.
Coronary occlusions
Coronary occlusions are occlusions in the coronary arteries. These arteries are arteries that supply blood to and from the heart for it to keep it pumping. When there are obstructions on these arteries there is a restriction of nutrients and oxygen that can be delivered into the heart which leads to heart cells not being able to make ATP making them go out of sync when contracting, this makes the heart spasm and have a heart attack called a myocardial infraction.
These occlusions cause coronary heart disease, symptoms are chest pain, nausea, fatigue, and shortness of breath and more. Risk factors are smoking, obesity, alcohol, untreated diabetes, and more.
Xylem vessels
Xylem vessels are vessels in the vascular bundles of plants, they transport water and nutrients from the roots to the leaves through the stems. The vessels are emptied out cells that form a tube, the left over cellulose from the cell walls has thickenings added to them with a polymer called lignin, it’s there for strength since the pressure in the xylem is usually below atmospheric pressure. Those walls are impermeable but have gaps called pits where water can exist.
Root pressure is a mechanism used to refill the xylem vessels with sap to rise. Firstly, root cells adjacent to the xylem vessels load up mineral ions to vessels by active transport, this transport makes the xylem sap hypertonic compared to the cytoplasm of the adjacent cells, so the water moves form them to the xylem through osmosis, lastly rising the pressure inside the vessels and pushing the sap upwards.
Dicot stem
The stem of a dicotyledonous plant is composed of:
Xylem, the vessel that transports water and nutrients from the roots to the leaves.
Phloem, the vessel that transports sucrose and nutrients from the leaves to the roots.
Cambium, produces more xylem and phloem
Epidermis, water proofing and protection
Cortex, photosynthesis and support
Pith, Bulking out the stem
Dicot root
Epidermis, absorbs water and mineral ions with root hair cells from the soil.
Endodermis, inner cell layer where water needs to pass through to get to the xylem
Xylem, the vessel that transports water and nutrients from the roots to the leaves
Phloem, the vessel that transports sucrose and nutrients from the leaves and roots
Cortex, bulking out the root.
Plasma
Plasma is the liquid component of the blood and it makes up 55% of the total blood volume. It is composed of:
- Salt ions
- Glucose
- Waste products
- Dissolved gases
- Proteins
- Water
Tissue fluid
Interstitial fluid is a watery substance that fills the spaces between tissues and cells throughout the body, it is formed when plasma leaks out of the capillaries.
Capillary exchange
Capillary exchange is a process in which substances move between the blood and surrounding interstitial fluid, there are 4 ways for capillary exchange to happen:
- Diffusion
- Vesicle transport
- Active transport
Bulk flow (water and dissolved substances move through the fenestrations in the capillary walls due to differences of osmotic and hydrostatic pressure
In the arteriole end of capillaries the pressure is greater than in the surrounding tissue therefore the net movement of fluid is moved out of the capillaries by bulk flow (called filtration).
In the venule end of the capillaries the pressure is lower than in the surrounding tissues because the pressure has flowed out, so now interstitial and plasma fluid will move back into the capillary (called reabsorption).
Lymphatic system
The lymphatic system is a drainage system that picks up left behind plasma fluid during filtration in capillary exchange and circles it back to the blood stream. This left behind plasma is called lymph and it is absorbed by lymph vessels, these then transport the lymph fluid into lymph nodes throughout the body to break down bacteria in the lymph by lymphocytes in the lymph nodes. One the bacteria have been broken down the lymph is transported through the lymphatic trunk back into the blood stream.
Single circulation
Single circulation in fish is because their heart only has 2 chambers, one that receives the blood and another that pumps it out. After the deoxygenated blood from the heart is pumped out it is pumped to the gills where it becomes oxygenated, it can be pumped to the gills at high pressure because the surrounding water prevents it from bursting. Once the blood has been oxygenated in the gills where it has a counter current flow, it still has enough pressure to be pumped to the organs for gas and material exchange to occur, lastly from the organs the blood at low pressure is delivered back to the heart deoxygenated for the cycle to go again.
Heart structure
The heart is structured as follows:
- Ventricles, chambers in the heart with strong smooth muscle that can generate high blood pressure when it contract to pump blood to the arteries.
- Atria, chambers in the heart with thinner muscular wall, where the sinoatrial node is located (in the right chamber), it gets blood from the veins and pumps it to the ventricles when it contracts (pumping as much as possible).
- The sinoatrial node, this is the node that creates the electrical signal that stimulates contraction in the atria at the beginning of the atrial systole.
- Atrioventricular valve, this valve is between the atrium and ventricle on each side. These valves prevent backflow from the ventricle contraction back to the atrium and allows blood from the atrium to flow into the ventricle during ventricle diastole.
- Semilunar valves, the semilunar valves are the valves between the arteries and ventricles that prevent backflow to the ventricles and allow blood to pump from the ventricles to the arteries when open during ventricle systole.
- Cardiac muscle, is specialized muscle tissue that forms the walls in the atria and ventricles, it has branched cells that allow connection between the plasma membranes of adjacent cells to allow electrical contractions without the need for motor neurons, (myogenic movement).
- Septum, the wall of the heart that separates the left and right sides of the heart, preventing deoxygenized blood from mixing with oxygenized blood.
- Coronary vessels, these vessels on the wall of the heart provide a supply of blood to the heart to keep it pumping and collect deoxygenated blood from the heart wall and return it to the right atrium.
Phloem sieve tubes
The transport of sugar through the plant is from sources to sinks (sources being the tissues where the compounds are produced or stored and sinks are tissues that need to be supplied by the sources). It starts in the leaves where sucrose is made through photosynthesis, then to transports the sucrose to the roots which are the sinks the sucrose and other nutrients need to go to through the phloem sieve tube vessels. Sieve tubes in the phloem tissue provide channels for transport to happen, the sieve tube cells are empty cells like in the xylem but at the end of each cell there are gaps on the end walls called sieve plates which allow the sap to flow through each sieve tube cell. Sieve tube cells use active transport for loading and unloading sucrose (cotransport) but they have little to no mitochondria so they rely on their adjacent companion cells for ATP supply.
High solute concentration develop in the sieve tubes of the leaves and other sources of sucrose which draws water in by osmosis, increasing hydrostatic pressure, this difference of pressure lowers the solute concentration in the phloem sieve tubes therefore water exists and hydrostatic pressure goes down again. The difference in pressure between the phloem sap in the sources and in the sinks drives water to help the flow of phloem sap to the sink. This is supported by the plasma membrane in the sieve tube cells, although the cellulose walls are not as thick as in the xylem.
Stages of the cardiac cycle
The stages go as follow:
0-0.1 secs The atrial systole. The sinoatrial node sends an electrical signal to the atria which makes it contract applying rapid but small pressure to the atria causing blood to pump through the atrioventricular valve into the ventricles. The semilunar valve remains closed.
0.1-0.15 secs Ventricular systole. The ventricle contracts with rapid pressure build-up which causes the atrioventricular valve, while the semilunar valve stays closed.
0.15-0.4 secs Ventricular systole. The pressure in the ventricles causes the semilunar valve to open, pumping blood to the arteries, maximizing the arterial blood pressure. The pressure slowly rises in the atrium as blood drains from the veins filling the atrium.
0.4-0.45 secs ventricular diastole: the ventricle stops contracting and the pressure drops below the pressure of the artery causing the semilunar valve to close. And the atrioventricular valve remains closed.
0.45-0.8 ventricular diastole, the pressure in the ventricle drops below the pressure in the atrium so the atrioventricular valve opens. Blood from the veins drains into the atrium and from there into the ventricle, causing a slow increase in pressure.
