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Fever: An abnormal elevation of body temperature, usually as a result of a pathologic process.

Allergic Reactions

JoVE 10901

We speak of an allergy when the immune system triggers a response against a benign foreign structure, like food, pollen or pet dander. These elicitors are called allergens. If the immune system of a hypersensitive individual was primed against a specific allergen, it will trigger allergic symptoms during every subsequent encounter of the allergen. Symptoms can be mild, such as hay fever, to severe, such as potentially fatal anaphylactic shock. The immune system is crucial for defending an organism against bacteria, viruses, fungi, toxins, and parasites. However, in a hypersensitive response, it can be triggered by harmless substances and cause unpleasant or potentially life-threatening overreactions, called allergies. The first step toward establishing an allergy is sensitization. For instance, an individual becomes allergic to the pollen of ragweed when, for the first time, immune cells in the respiratory passage take up the pollen and degrade the allergens into fragments. These immune cells are called antigen-presenting cells, or APCs, because they display the degraded allergen fragments on their surface. Examples of APCs are dendritic cells, macrophages and B cells. Subsequently, APCs activate encountered Type 2 helper T cells (Th2). The activated Th2 then release chemical signals (e.g., cytokines) that cause B cells to differen

 Core: Biology

Accessory Organs

JoVE 10831

Accessory organs are those that participate in the digestion of food but do not come into direct contact with it like the mouth, stomach, or intestine do. Accessory organs secrete enzymes into the digestive tract to facilitate the breakdown of food.

Salivary glands secrete saliva—a complex liquid containing in part water, mucus, and amylase. Amylase is a digestive enzyme that begins breaking down starches and other carbohydrates even before they reach the stomach. The liver, gallbladder, and pancreas are the other accessory organs involved in digestion. All three secrete enzymes into the duodenum of the small intestine via a series of channels called the biliary tree. The liver and gallbladder work together to release bile into the duodenum. The liver produces bile, but it is stored in the gallbladder for secretion when needed. Bile is a mixture of water, bile salts, cholesterol, and bilirubin. Bile salts contain hydrophobic areas and hydrophilic areas which allows it to engage with both fats and water. Thus it breaks down large fat globules into smaller ones—a process called emulsification. Bilirubin is a waste product that accumulates when the liver breaks hemoglobin from red blood cells. The globin is recycled and the heme, which contains iron, is excreted in the bile. The presence of bilirubin is what gives feces its brown color

 Core: Biology

What are Viruses?

JoVE 10821

A virus is a microscopic infectious particle that consists of an RNA or DNA genome enclosed in a protein shell. It is not able to reproduce on its own: it can only make more viruses by entering a cell and using its cellular machinery. When a virus infects a host cell, it removes its protein coat and directs the host’s machinery to transcribe and translate its genetic material. The hijacked cell assembles the replicated components into thousands of viral progeny, which can rupture and kill the host cell. The new viruses then go on to infect more host cells. Viruses can infect different types of cells: bacteria, plants, and animals. Viruses that target bacteria, called bacteriophages (or phages), are very abundant. Current research focuses on phage therapy to treat multidrug-resistant bacterial infections in humans. Viruses that infect cultivated plants are also highly studied since epidemics lead to huge crop and economic losses. Viruses were first discovered in the 19th century when an economically-important crop, the tobacco plant, was plagued by a mysterious disease—later identified as Tobacco mosaic virus. Animal viruses are of great importance both in veterinary research and in medical research. Moreover, viruses underlie many human diseases, ranging from the common cold, chickenpox, and herpes, to more dangerous infection

 Core: Biology

Lymph Node Exam

JoVE 10061

Source: Richard Glickman-Simon, MD, Assistant Professor, Department of Public Health and Community Medicine, Tufts University School of Medicine, MA


The lymphatic system has two main functions: to return extracellular fluid back to the venous circulation and to expose antigenic substances to the immune system. As the collected fluid passes …

 Physical Examinations II

Nose, Sinuses, Oral Cavity and Pharynx Exam

JoVE 10152

Source: Richard Glickman-Simon, MD, Assistant Professor, Department of Public Health and Community Medicine, Tufts University School of Medicine, MA


This video provides an overview of sinus, nose, and throat examinations. The demonstration begins with a brief overview of the anatomy of the region. The upper third of the nose is bony, and…

 Physical Examinations II

Testing the Heat Transfer Efficiency of a Finned-tube Heat Exchanger

JoVE 10437

Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA


Heat exchangers transfer heat from one fluid to another fluid. Multiple classes of heat exchangers exist to fill different needs. Some of the most common types are shell and tube exchangers and plate exchangers1.…

 Chemical Engineering

Cardiac Exam III: Abnormal Heart Sounds

JoVE 10135

Source: Suneel Dhand, MD, Attending Physician, Internal Medicine, Beth Israel Deaconess Medical Center


Having a fundamental understanding of normal heart sounds is the first step toward distinguishing the normal from the abnormal. Murmurs are sounds that represent turbulent and abnormal blood flow across a heart valve. They are caused…

 Physical Examinations I

Measuring Vital Signs

JoVE 10107

Source: Meghan Fashjian, ACNP-BC, Beth Israel Deaconess Medical Center, Boston MA


The vital signs are objective measurements of a patient's clinical status. There are five commonly accepted vital signs: blood pressure, heart rate, temperature, respiratory rate, and oxygen saturation. In many practices, pain is…

 Physical Examinations I

Whole-Mount In Situ Hybridization

JoVE 5330

Whole-mount in situ hybridization (WMISH) is a common technique used for visualizing the location of expressed RNAs in embryos. In this process, synthetically produced RNA probes are first complementarily bound, or "hybridized," to the transcripts of target genes. Immunohistochemistry or fluorescence is then used to detect these RNA hybrids, revealing spatial and temporal patterns of…

 Developmental Biology
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