Blood Flow Through the Heart: From Tissues to Ventricles - Essay Sample

Introduction

The blood from the body tissues and organs reaches the heart via the superior and inferior vena cava. This blood goes through the right atrium, the upper right chamber of the heart. The blood then flows to the right ventricle via the tricuspid valves. Once the right ventricle is full, the tricuspid valve closes and an electrical signal is generated in the His Purkinje node triggering the contraction of the ventricles forcing the blood out of the ventricle via the pulmonic valve through the right and left pulmonary artery to the respective lungs. The pulmonary artery branches into capillaries which increase the surface area for oxygenation. Oxygenation takes place in the alveoli, and the blood flows through the pulmonary vein where it is transported back to the left atrium. Once the left atrium is full, it contracts to open the mitral valve and the blood pours into the left ventricle. Relaxation to the capacity of the ventricles once full excites the His Purkinje fibres, which contracts to cause the mitral valve to shut, and the aortic valve opens to allow the blood to leave the heart through ascending and descending aorta to the rest of the body (Peate & Nair, 2015; p. 34-39).

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Critical points to remember include that the right side of the heart deals with deoxygenated blood while the left side accumulates blood rich in oxygen. All veins in the body carry blood poor in oxygen apart from the pulmonary vein while all arteries carry blood rich in oxygen apart from the pulmonary artery (Rizzo, 2012; p. 323).

Describing Normal Sinus Waveform at P, Q, R, S and T

The sinus waveform can be represented graphically in an electrocardiogram test results. The waveform is often illustrated using the markers p, Q, R, S, and T, each representing a function in the sinus electric impulse that produces the heart rhythm and rate. Understanding the wave is critical in making a heart-related diagnosis (Peate & Nair, 2015).

The P wave illustrates the beginning of atrial contraction (depolarization). In normal cases, the P wave should not be more than 2.5mm tall and not lasting over 0.11 seconds.

The QRS complex represents ventricular depolarization which starts with an electric impulse to the atrioventricular node through the intraventricular septum and finally the ventricles. A normal QRS complex is expected to be in the range of 0.06 and 0.01 seconds. In leads, I, II, III, aVL, V5, V6, and aVF, the wave is positive unlike in aVR, V1, and V2 leads where the wave is negative (Rizzo, 2012).

The ST segment is a representation of the end of ventricular contraction, which also marks the start of ventricular repolarization.

At T wave, the heart contraction and relaxation circle are completed and the heart muscle prepares for a new cycle. The T wave is positive in leads I, II, and V2 – V6 with the only lead negative being aVR.

Mechanism Used to Achieve Venous Return to the Heart

Venous return describes the flow of blood from the periphery to the right heart atrium. Compromised venous return results in reduced cardiac output, oedema of the lower limbs, and high blood pressure. Several mechanisms concurrently facilitate venous return. The first mechanism is the pressure gradient which is the difference in pressure between venous return and pressure in the right atrium. The pressure gradient is influenced by venous pressure (such as physical activities), venous resistance (such as in vein constriction), and right atrium pressure. When emptying of the right atrium is compromised such as with tricuspid defects allowing backflow, the pressure gradient is significantly reduced inhibiting effective venous return. Doing exercises increases venous pressure increasing venous return through influence on the pressure gradient. The second mechanism is the skeletal muscle pump system whereby engaging the muscles such as in physical activity, the muscle pushes the blood up the vein. The one-way valves in the veins reduce the backflow of the blood thus increasing venous return. The third mechanism is gravity which allows the blood flow through the superior vena cava to flow the heart simply by gravity while the flow-through inferior vena cava must overcome this gravity force. The impact of gravity is often observed with blood pooling in cases of prolonged standing or sitting in one position. The fourth mechanism is breathing activity, where the descent of the diaphragm decreases the thoracic pressure while at the same time increasing abdominal pressure. The effect is pushing the blood up the inferior vena cava to the right atrium. These mechanisms may act individually or together to influence the effectiveness of venous return (Berlin & Bakker, 2014).

The Process of Urine Formation

The process of urine formation in humans can be categorized into three phases. The first phase called the glomerular filtration takes place in the Bowman’s capsule. The Bowman’s capsule comprises a cup-shaped structure where blood flows in through the afferent arteriole and out through the efferent arteriole. The efferent arteriole is narrower compared to afferent arterioles. Consequently, the hydrostatic pressure increases the ability to filter out molecules with small particles such as water, inorganic ions, glucose, amino acids, urea, and creatinine. The filtered out substance forms the glomerular filtrate that collects in the Bowman’s capsule and down the nephron system (Peate & Nair, 2015).

The second phase is the tubular reabsorption and secretion that takes place in the renal tubule. The tubules include the proximal convoluted tubule, descending loop of Henle, ascending loop of Henle, and the distal convoluted tubule. As the glomerular flow through the tubules, water is reabsorbed back through osmosis. The reabsorbed water then creates a gradient slope in the concentration forcing sodium ions, calcium ions, drugs, and glucose to be reabsorbed into the blood vessels. The reabsorption leaves large particle elements such as urea, creatinine, and lactate concentration in the glomerular filtrate. The aldosterone hormone and the parathyroid hormone acts in the distal convoluted tubule to regulate the urine concentration based on blood constituents (Peate & Nair, 2015).

The third phase is water conservation in the collecting duct. Increases the process of water conservation achieved through the osmolality gradient created by the ascending loop of Henle which gets more concentrated. As the fluid flows through the collecting duct, it loses more and more water content. The collecting duct is mainly influenced by antidiuretic hormones. At the end of the collecting duct, the urine is already formed (Peate & Nair, 2015).

Structures of the Respiratory System

The parts of the respiratory system involved in the passage of air to the lungs include the nose, pharynx, trachea, bronchi, the bronchioles, and the air sac. The nasal cavity is lined with hair, which traps dust and foreign matter. The pharynx has elastic cartilage called epiglottis which prevents food to get into the trachea. The larynx is also called the voice box often used in making a sound. The trachea is the windpipe large in diameter and held in situ by circular cartilage. The trachea branches into two bronchi for the left and the right lungs. The bronchi further subdivide to for the bronchioles which direct the inhaled air into the air sacs for gaseous exchange. The intercostal muscles are also crucial in breathing since their relaxation and concentration facilitate the expansion and constriction of the chest cavity. The diaphragm is a dome-shaped organ, where flattens to create a negative pressure allowing the lungs to deflate and inflate facilitating breathing (Rizzo, 2012).

Glucose Homeostasis

Glucose homeostasis involves a cascade of processes responsible for maintaining normal blood sugar levels fluctuations in glucose availability following episodes of eating and fasting. The products the student ate, that is, the biscuits, cake, and ice cream are all fast food, which is digested fast and is rich in glucose. Therefore, immediately after taking each of the three, the blood sugars spikes within a short period. The increased level of blood sugars is detected and triggers the release of insulin hormone, which responsible for converting excess glucose to glycogen for storage. This means the glucose clears fast from the blood circulation creating the sensation of hunger. The glucagon is then released in between the breakfast, lunch, and dinner to maintain the flow of glucose in the blood within the normal range. Glucagon works by converting stored energy to glucose when blood sugar levels go below the body's demand levels (Rizzo, 2012).

Red Blood Cell in Hypotonic Solution

Homeostatic systems and processes in the body are crucial in balancing the cell's environment based on the surrounding environment concentration. Ideally, a cell placed in hypertonic media loses water thereby shrinking. In an isotonic solution, the cell will maintain its shape since the cell’s concentration and that of the media are equal. Placed in a hypotonic solution, the red blood cell will take in excess water through osmosis swelling to the extent of bursting as homeostatic processes try to attain an isotonic state (Peate & Nair, 2015).

Concerning patients, the infusion of pure water creates a hypotonic medium by haemodilution. The red blood cell is therefore, likely to take in more water through osmosis, which can result in multiple red blood cells exploding and thus compromising the oxygen circulation. Furthermore, the red blood cells are biconcave in shape, and swelling after taking in a lot of water makes the cells lose the biconcave shape, thereby, reducing the service areas for oxygenation (Peate & Nair, 2015).

How Body Protects the Intestinal Tract from Gastric Acid

Gastric acid is produced in the stomach and is critical in converting apoenzyme such trypsinogen to active enzyme trypsin. However, it can also be a risk of corrosion to the stomach wall and the intestinal walls in case the body protective mechanisms are compromised. The human body prevents the intestinal tract from being corroded by gastric acid through two main mechanisms. The first is ensuring the gastric acid is neutralized at the duodenum by the bicarbonate products from the bile juice. The second mechanism is by ensuring the intestines are lined with mucus, which cushions the intestinal wall from corrosion (Peate & Nair, 2015).

Trophic and Non-trophic Hormones of the Pituitary Gland

Body hormones can be categorized based on the targeted organ. Trophic hormones are released to influence an endocrine organ to release other hormones. Examples of such hormones produced by the pituitary gland include thyroid-stimulating hormone which triggers the release of thyroid hormone. Also, the Luteinizing hormone and follicle-stimulating hormones are targeting the ovary. Lastly, the adrenocorticotrophic hormone targets the adrenal gland to release glucocorticoids (Peate & Nair, 2015).

Non-trophic hormones on the other hand lead to a direct effect on the targeted cells. Some of such hormone includes vasopressin, which produced targeting (Peate & Nair, 2015).

The Events of Respiratory Cycle

The respiratory cycle comprises of two major phases, that is, inspiration and expiration. During inspiration, the dome-shaped diaphragm flattens while the internal intercostal muscle contracts. The flattening of the diaphragm increases the chest cavity volume while the contraction of the external intercostal muscle moves the rib cage up and outwards further increasing the chest cavity. According to Boyles Law, the pressure is inversely rela...