PHYS20030 An Introduction to Physiology: Organs and Systems UCD Assignment Example

Physiology is the study of how the body works. It covers everything from the organs and tissues that make up the body to the systems that help it function, to how those systems interact with each other. In this blog post, we’ll take a closer look at some of the most important organs and systems in physiology. We’ll also explore some of the key concepts and theories associated with each one. So whether you’re just starting in physiology or you’re looking for a refresher on these topics, read on for an introduction to some of the most important organs and systems in your body.

Assignment Task 1: Describe the structure and function of heart and blood vessels.

The heart is a special organ in the body because it does not have any essential cells. The only tissue that makes up the organ are muscle tissues. It contains mainly cardiac muscle fibers arranged to lower blood pressure during diastole and increase it during systole. A completely different type of tissue, connective tissue, creates an intricate system of blood vessels and lymphatic vessels around the heart and in between major organs. The structure of blood vessels is such that they can collapse under pressure, so it becomes very important to have a mechanism by which the heart maintains its own blood pressure via pumping mechanisms. Blood vessel walls are made up of three layers: an inner endothelial layer, a middle muscular layer, and an outer fibrous layer. The walls of blood vessels are very elastic, this property of the wall is what causes the vessel to collapse when pressure within the vessel falls below a certain threshold.

The heart generates its own electrical impulses and rhythm of contraction. These signals are carried by the cardiac conduction system, which surrounds the heart and is made up of specialized muscles cells called myocytes (cardiomyocytes) that form a single cell layer between the endocardium and epicardium. The myocytes generate action potentials that propagate through these cells, causing them to contract. The cardiac conducting system sends these signals out into the heart via specialized connections called “gap junctions” which synchronize the contraction of the heart muscle. This is important because, without synchronization, the atria and ventricles would not be able to contract simultaneously, leading to stagnation in the blood flow.

Assignment Task 2: Describe the structure and function of the airways.

The airway are sub-divided into the upper airway, which includes the mouth and nose; and the lower airways. The lower airways include the trachea, bronchi, bronchioles, and alveoli. The trachea is a tube that carries inhaled air to the larynx where it enters the glottis. The exit of the glottis is called the “false vocal cords” and leads into the infraglottic cavity where it joins with the larynx. The false vocal cords lead up to the epiglottic cartilage which separates food from the air for proper mastication (chewing) to occur. Beneath the epiglottis is the arytenoid cartilages which are what separates food from the air.

The larynx itself is suspended in front of the trachea by the thyrohyoid membrane. The larynx also has two functions: it acts as an airway passage to the trachea, and it houses the vocal cords, which are responsible for vocalization. The trachea is made up of 16-20 C-shaped cartilage rings and the lumen (opening of the tube) of the trachea can be collapsed by muscles during swallowing to prevent food from entering the airway.

The bronchi branch off from each lobe of the lungs, the right bronchus is shorter than the left. Both bronchi branch off into secondary and tertiary branches called “bronchioles.” The cross-section of a bronchiole is similar to that of an airway, containing cartilage rings with complete walls made of smooth muscle fibers. Bronchial arteries divide at each tertiary bronchiole to form a rich capillary bed. The end of each bronchiole is surrounded by alveolar sacs, which are where oxygen and carbon dioxide diffuse across the alveolus membrane. Each alveolus contains many capillaries that converge at an arteriole and venule. These blood vessels nourish the alveolus with oxygen and remove waste-containing carbon dioxide.

Assignment Task 3: Describe the mechanisms of gas exchange and transport.

Transport in the body involves a gas exchange between the environment and the human body. The main functions of breathing (or ventilation) are to release carbon dioxide which is produced within cells, and the uptake of oxygen into the bloodstream for use by cells.

The actual movement of gases is dependent upon many factors, including density and viscosity.  The physical properties of gas make this movement possible. Four factors affect the diffusion of gases, first is the difference in partial pressure on either side of the membrane. The second is the distance between each molecule. The third is the area available for diffusion. And lastly, it depends upon how soluble a gas is within another substance (usually water).

These factors that affect gaseous diffusion are all related to the difference between partial pressures. This, in turn, is directly proportional to solubility and solubility has an inverse relationship with distance. The opposite of this difference is what determines the movement of gases throughout the body.

Assignment Task 4: Explain how food is digested and absorbed.

The digestive system is made up of the gastrointestinal tract (GI), accessory organs, and the associated lymphatic tissues. It is responsible for digesting food into small molecules that can pass into the bloodstream. The GI tract begins with the mouth where mastication (chewing) breaks down food into smaller pieces. The saliva secreted by salivary glands contains salivary amylase, a digestive enzyme that starts breaking down the carbohydrates present in food. The bolus (final product after mastication) enters the esophagus and is pushed down by peristalsis to the stomach where further digestion occurs. Protein digestion occurs within the stomach as pepsin, found in gastric juice secreted by gastric glands in the stomach walls, is activated through hydrochloric acid (HCl) and pepsinogen.

Protein digestion concludes with the small intestine where pancreatic amylase (an enzyme that breaks down carbohydrates) and intestinal lipases (enzymes that break down lipids) complete the breakdown of carbohydrates and lipids. The products of these digestive enzymes are absorbed through the intestinal epithelium and into capillaries in the intestinal villi. They enter hepatic portal vessels, which bring them to the liver for storage or distribution around the body (most molecules get stored as fat). After food has been processed, residual material will pass through the small intestine and into the large intestine where more water is absorbed. Afterward, the remaining material (feces) will be passed out of the body through defecation.

Assignment Task 5: Describe the structure and functions of the kidneys and urinary system.

The kidneys are two bean-shaped organs that are located at the bottom of the ribcage. They are made up of about a million functional units called nephrons. The kidneys filter out metabolic waste products while balancing salt, potassium, and acid concentrations in the body through urine production.

Functioning bilaterally, each kidney has four major sections: cortex, outer medulla, inner medulla, and papilla. The kidneys filter the blood to produce about a quart of urine a day. The nephrons filter out water and small solute molecules from the blood to form urine, which is sent down through tubes called ureters into the bladder. The kidneys maintain homeostasis by adjusting the levels of ions, water, and other molecules that are lost from the body in urine.

The kidneys do not metabolize glucose or amino acids, but they do help maintain the right balance of hormones to control how much water is excreted in a person’s urine. A pair of kidneys can fail if their function decreases by more than fifty percent. If this happens, waste products begin to accumulate in the blood, which can cause severe damage to different organs in the body.

Assignment Task 6: Describe the principal endocrine glands and their basic functions.

Endocrine glands in the body secrete hormones, which are chemical messengers that affect certain cells or tissues in distant parts of the body. Hormones help control and coordinate a wide variety of bodily functions including digestion, metabolism, growth and development, tissue function, sexual function, reproductive processes, sleep and wake cycles, moods and emotions, reproduction, and the ability to sense pain.

The principal glands in the human endocrine system are the hypothalamus, pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas (which has both endocrine and exocrine functions), ovaries (female) and testes (male), pineal body (connected to the brain by a tiny stalk), and in women, the mammary glands.

Assignment Task 7: Explain how the actions of the major body systems contribute to the function of homeostasis.

All body systems work together, creating a complex dialogue to maintain homeostasis. For example, when blood sugar levels increase in the body due to food intake, the pancreas releases insulin into the blood. As insulin attaches to cells throughout the body it stimulates these cells to take in glucose from the blood and lower glucose levels in the blood. If blood glucose levels fall, the pancreas releases glucagon into the blood. Glucagon stimulates cells throughout the body to release stored sugar into the bloodstream and increase levels of blood sugar. Both insulin and glucagon help return blood glucose concentrations back to normal so that all cells receive adequate nourishment.

Sensory receptors monitor changes in internal and external conditions. The endocrine system orchestrates all other systems to maintain optimal conditions in the body to ensure survival.

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