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The Human Spleen: Functions and Importance

The Human Spleen

The spleen is an organ system located in the upper far left part of the abdomen, to the left of the stomach. I chose to discuss this organ because it is often neglected as essential and I wanted to know how it impacts one’s health. This organ fluctuates in size and shape depending on the individual, but it’s normally fist-shaped, purple, and about 5 inches long, weighing around 6 ounces (Bailey, 2018, October 22). It is a soft, spongy organ that appears purple due to the quantity of blood vessels running through it. Since the spleen is shielded by the rib cage, you can’t feel it unless it’s abnormally enlarged. Although its location is near the digestive organs, the spleen is actually part of the lymphatic system, responsible for filtering toxins and waste out of the body as part of the larger immune system (Bailey, 2018, October 22). The spleen removes the body’s old and damaged red blood cells and stores white blood cells for the fighting of infections (Bailey, 2018, October 22).
Function of the Spleen
Filtering blood is the most important job of the spleen. As blood flows into the spleen, it damaged red blood cells are detected (Bailey, 2018, October 22). Blood flows through a web of channels in the spleen. Healthy cells flow straight through and the unhealthy are broken down by large white blood cells called macrophages. Once the red blood cells are broken down the spleen stores useful nutrients such as iron, and returns it to the bone marrow. This permits hemoglobin to produce. In humans, around 1 cup of blood is kept in the spleen, ready to be released if there is a significant loss of blood (Bailey, 2018, October 22). The spleen clears out old platelets from the blood and acts as a reservoir. As a fetus is developing, the spleen makes red blood cells, but after the fifth month of gestation, it stops (Bailey, 2018, October 22).
The spleen also produces compounds to help the immune system called opsonins, which include properdin and tuftsin (HM, 2019). An opsonin is any molecule that improves phagocytosis by designing an antigen for an immune response, or marking dead cells for reprocessing (HM, 2019). Opsonins help the immune system in several ways. In a healthy individual, they mark dead and dying cells for clearance, trigger complement proteins, and target cells for annihilation by using natural killer cells (HM, 2019). Properdin is a protein present in the blood that aids in the how the body responds to certain kinds of infection (HM, 2019). Tuftsin is a peptide associated with the immune system function, and produced primarily in the spleen (HM, 2019).
Tissues within this Organ System
Two types of tissue directly control the organ’s function. The white pulp portion of the spleen produces B and T-lymphocytes (Bailey, 2018, October 22). T-lymphocytes (T-cells) are responsible for cell mediated immunity, which is an immune response that involves the initiation of certain immune cells to fight infection (Bailey, 2018, October 22). B-lymphocytes (B-cells) originate from bone marrow stem cells. B-cells create antibodies that are specific to an antigen (Bailey, 2018, October 22). The antibody binds to the antigen and labels it for destruction by other immune cells (Bailey, 2018, October 22). Both white and red pulp contains lymphocytes and immune cells called macrophages (Bailey, 2018, October 22). These cells remove antigens, dead cells, and debris by eating them. The lymphocytes can create protein antibodies that attack microbes that have invaded the body and could cause infection. The spleen’s red pulp controls blood-filtering functions. Red pulp consists of venous sinuses and splenic cords. Venous sinuses are vital cavities filled with blood, while splenic cords are connective tissues containing red blood cells and certain white blood cells including lymphocytes and macrophages (Bailey, 2018, October 22). The red pulp breaks down old or damaged red blood cells along with other waste from the blood, and then removes it from the body. Likewise, the spleen’s red pulp holds different types of white blood cells calls phagocytes, which consume foreign bodies such as bacteria and viruses (Bailey, 2018, October 22).
Human Body Systems Interconnected with the Spleen
The circulatory system rests on the normal functioning of the bone marrow and spleen (Lori, et al. 2017). They work synergistically in carrying out the majority of the blood-producing roles, while the other assists in cleaning the blood stream and replenishing cells after an injury or infection (Lori, et al. 2017). Without the cells delivered by these organs, the circulatory system would contain only lymphatic components, and the human body would not survive (Lori, et al. 2017).
In previous years, researchers focused their attention on finding the basis of the immune system’s innervation, revealing that spleen receives fibers from the nervous system (Lori, et al. 2017). Several experiments have been developed since then to develop our understanding of the splenic innervation. Research and science have described that sympathetic nervous system fibers innervate the spleen, and their synaptic endings are right alongside with immune cells (Lori, et al. 2017). Released neurotransmitters come in contact with lymphocytes, networking with their specific receptors and controlling immune cells responses. These properties portray the neuro-immune communication (Lori, et al. 2017). Once they are stimulated, the immune cells produce and discharge a variety of pro- or anti-inflammatory mediators, which offer an immune cell response (Lori, et al. 2017). The neuro-immune interaction provides an important connection between immune cells and the nearby fibers of the autonomic nervous system supplying the spleen. This current discovery has revealed that the nervous system controls immunological responses induced by hypertensive stimuli (Lori, et al. 2017). This implies that the same neuro-immune communication in this secondary lymphoid organ replenishes immune cells in tissue during metabolic disease (Lori, et al. 2017).
This spleen is vulnerable to several diseases and injuries that may affect the organ’s function or require it to be surgically removed from the body. Liver diseases or blood cancers may enlarge a spleen, which can cause abdominal pain (Ruth, 2017). A ruptured spleen, or one that has been injured from a blow to the body, can cause internal bleeding and is usually a life-threatening emergency. Ruptured spleens may be repaired, but removing the organ is often the safest treatment (Ruth, 2017). People can live without a spleen, but they are more prone to infectious diseases. Other parts of your body, like your liver and lymph nodes, are able to jump in and take over many of your spleen’s functions (Ruth, 2017). The spleen play a large role in supporting the body by filtering blood to keep our immune system operating optimally, so having it removed will have a significant impact on our immune system. Specifically, the spleen helps fight bacteria that cause pneumonia and meningitis (Bronte

Overview of the Human Respiratory Syste

Respiration is an example of an exothermic reaction. It releases energy from glucose molecules for use by the body. Organisms need this energy for chemical reactions to build larger molecules, for movement and to keep warm. Respiration in cells can be aerobic (with oxygen) or anaerobic (without oxygen).
Aerobic respiration takes place in the mitochondria and requires oxygen and glucose to do so. Glucose is a substance which is essential to life. It breaks down into ATP for the energy for respiration in all living things. However, glucose and its transfers are particularly key to human life, it provides us with all our energy and is transported through diffusion. Diffusion I a passive process – this is the rapid and random movement of particles from a high concentration of solutes to a low concentration of solutes-which in this case is glucose.
For example, one of the most common processes of aerobic respiration is where it occurs in the muscle
This type of respiration produces carbon dioxide, water and energy. The chemical equation for aerobic respiration is…
C6H12O6 6O2 will produce 6CO2 6H2O( 38ATP)
The faster the rate of respiration, the greater the rate of oxygen use and the greater the rate of carbon dioxide release.
Stage 1-Aerobic glycolysis is the same process as Anaerobic glycolysis except that the presence of oxygen inhibits the accumulation of lactic acid by diverting pyruvic acid further into the aerobic system. Pyruvic acid combines with coenzyme A to form Acetyl CoA.
Stage 2- Krebs Cycle- The Acetyl CoA from stage 1 combines with oxaloacetic acid to form citric acid. Then complex reactions within the matrix of mitochondria take place:
Carbon dioxide is produced and removed by the lungs
Hydrogen atoms are removed (oxidation)
Energy is produced to resynthesize 2 molecules of ATP
Oxaloacetic acid is regenerated
Stage 3- Electron transport chain- The hydrogen atoms combine with the coenzymes NAD and FAD to form NADH and FADH. These are carried down the electron transport chain where hydrogen is split into H and e-. This takes place when the cristae folds of the mitochondria, where 3 important things take place:
The hydrogen electron splits from hydrogen atom and passes down the ETC.
This provides sufficient energy to resynthesize 34 ATP.
The hydrogen ion combines with oxygen to form water.
The total energy produced by this system is 38 ATP.
• 2 ATP from Aerobic glycolysis
• 2 ATP from Krebs cycle
• 34 ATP from ETC
Anaerobic respiration also produces energy and uses glucose; however, it produces less energy and does not require oxygen. This is useful in tissues that have a high energy demand such as in working muscles, in which there is not enough oxygen to produce all the energy needed by using anaerobic respiration alone. Anaerobic respiration takes place in the cell cytoplasm and produces lactic acid. The chemical equation for anaerobic respiration is…
C6H12O6 will produce 2C3H6O3( 2ATP)
The lactic acid is toxic and needs to be oxidised to carbon dioxide and water to prevent it from building up. This process requires oxygen and therefore following anaerobic respiration there is oxygen debt in the cell, as oxygen is needed to break down the lactic acid. The waste product, lactic acid, builds up in the muscles causing pain and tiredness. Anaerobic respiration releases much less energy per glucose molecule than aerobic respiration does. Muscle fatigue is the result of anaerobic respiration in the musclecells.
Fermentation is a metabolic process that consumes sugar in the absence of oxygen. The products of fermentation are organic acids, gases, or alcohol. Fermentation takes place in yeast and bacteria and also in oxygen starved muscle cells as in the case of lactic acid fermentation. In micro-organisms fermentation is the primary way of producing ATP by the degradation of organic nutrients anaerobically. The chemical and word equations for fermentation are…
Glucose will produce ethanol carbon dioxide
C6H12O6 will produce 2C2H5OH 2CO2
Ways of checking respiration in humans:
There are different ways to check the respiration in humans, with different tests to see how much respiration a person is capable of.
One method is to measure Peak Flow. This is a person’s maximum speed of expiration. This is measured with a Peak Flow Meter. This measures the airflow through the bronchi and the extent of potential obstruction in the airways. Peak Flow is generally measured in units of litres per minute(L/min). Peak Flow readings are higher when you are well and lower when the airways are constricted. However due to the wide range of ‘normal’ results and high amount of variability, peak flow is not recommended to test whether somebody has asthma.
Blood Pressure is also another way to check. When the heart beats, it pumps blood around the body to give it the energy and oxygen it needs. As the blood moves, it pushes against the sides of the blood vessels. The strength of this pushing is your blood pressure. If your blood pressure is too high it puts an extra strain on your heart and arteries and could lead to heart attacks and strokes.
Blood pressure readings have two numbers, for example 140/90mmHg. The top number is your systolic blood pressure (the highest pressure when your heart beats and pushes blood around the body). The bottom number is your diastolic blood pressure (the lowest pressure when your heart relaxes between beats).

Factors affecting the respiratory system in humans:
One factor affecting the respiratory system is asthma. Asthma is a condition whereby the airways of the respiratory system become restricted. Asthma makes the bands around the airways tighten so air cannot move freely in or out of the body phlegm can also narrow the airway further. Exercise can induce an asthma attack. Asthma reduces our respiration rate as it restricts oxygen getting to the working muscles. However exercise can benefit someone with asthma as it can reduce the effects by increasing respiratory muscles, vital capacity and the oxygen and carbon dioxide diffusion rate.
Another factor is partial pressure/altitude. Partial pressure tells us how much of a particular gas is present. Oxygen moves from high pressure (alveoli) to low pressure (capillaries) until the pressures are equal. The greater the differences in these gases, the quicker the rate of diffusion. At altitude there is less oxygen reducing the partial pressure, because there is less oxygen available you have to work harder. This can cause: shortness of breath, dizziness and difficulties in concentration. Due to the lack of oxygen altitude can lead to hypoxia which causes an increase in breathing rate and depth. Over a period of time at altitude your respiratory will adapt to the conditions. Athletes will train at altitude so their body adapts, adaptations include an increasing in red blood cells and capillaries which will allow more oxygen to be carried and diffused to the working muscles.
Another factor affecting respiration is temperature. At very high temperatures the rate of respiration decreases with time. At low temperatures the respiration rate is insignificant. The optimum temperature of respiration is between 20 to 30°C. Also if there is an increase in water then there will be an increase in respiration rate. When you increase the temperature you will give the particles more kinetic energy. This means that there will be more frequent collisions between the particles as there is an increase in movement of the particles. However too much heatmeans that the rate of reaction will decrease. This same concept applies to non-human organisms!
Another factor affecting respiration rate is exercise. During exercise the body needs more energy, so the rate of respiration increases. The heart rate, breathing rate and breath volume all increase to supply the muscles with more oxygen and glucose for the increase in aerobic respiration. During periods of intense activity, the muscles may not get supplied with enough oxygen, so anaerobic respiration starts to take place in the muscle cells. This causes a build up of lactic acid and creates an oxygen debt. The lactic acid causes the muscles to hurt and stops them contracting efficiently. Lactic acid is a poison, so needs to be got rid of quickly. Once exercise is finished, the oxygen debt must be repaid. Also after exercise blood flowing through the muscles transports the lactic acid to the liver where it is broken down. The oxygen debt is the amount of extra oxygen the body needs after exercise to react with the lactic acid and remove it from the cells.

One factor affecting respiration rate in non humans is the oxygen content of the atmosphere. The percentage of oxygen in the atmosphere has a great impact on the rate of respiration. When there is a decrease in oxygen to about 10% in the atmosphere then there is a decrease in respiration. At 5% of oxygen in the atmosphere there is definite retardation of respiration.
Another factor affecting respiration rates in non-humans is temperature. When you increase the temperature you will give the particles more kinetic energy. This means that there will be more frequent collisions between the particles as there is an increase in movement of the particles. However too much heat can cause tissue deterioration. The respiration rates of certain fruits can be controlled by storing them in cool, dry places as lower temperatures are able to slow the respiration rate and prevent the fruit from ripening.
Basal metabolic rate is the number of calories your organs need to function while you perform no activity whatsoever. Since your BMR is based largely on involuntary functions like breathing and pumping blood, changes in your day to day activity don’t do much to raise or lower this number.
BMR calculation for men BMR = 66.5 ( 13.75 × weight in kg ) ( 5.003 × height in cm ) – ( 6.755 × age in years )
BMR calculation for women BMR = 655.1 ( 9.563 × weight in kg ) ( 1.850 × height in cm ) – ( 4.676 × age in years )
Things that affect BMR:
Body weight, Gender, Activity Levels, Temperature, Age, Muscle Mass, Body Fat Percentage.

Men tend to have higher BMRs than women because women tend to have less muscle mass than men. Also men tend to be larger in size, this means that more energy is required to perform basic functions as the body is larger. Women also tend to have a higher body fat percentage. This means that less energy will be required due to the fat acting as an insulator.
Direct calorimetry- Measurement of heat actually produced by the organism which is confined in a sealed chamber or calorimeter. This process is accurate. However, the person has to be isolated for a long time (at least 24 hours)
Indirect calorimetry- Estimates the heat production by measuring gas exchange. This process is really quick as it only takes 10 minutes and it can also be done at home. You also have to fast for 12 hours before it.
Fermentation experiment:
This experiment is performed to test the rate of respiration of yeast, a single celled kind of fungus. And given food and air it will grow and multiply. And to test which environment is best you make up a series of sugar solutions. You use different temperatures of water in each sugar solution and then add the yeast to the solution. Once the yeast has been added you quickly close the bung and time it. Each minute you record how much gas has been produced by the yeast respiring and make a note of it. You should find that as the time increases so does the amount of gas produced by the yeast. We repeated the experiment 3 times to be able to get valid and reproducible results and also to get a mean volume of gas produced by the yeast undergoing fermentation.

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