A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that hold up an organism's shape; the endoskeleton, a rigid internal frame to which the organs and soft tissues attach; and the hydroskeleton, a flexible internal structure supported by the hydrostatic pressure of body fluids.
An artery is a blood vessel in humans and most other animals that takes blood away from the heart to one or more parts of the body. Most arteries carry oxygenated blood; the two exceptions are the pulmonary and the umbilical arteries, which carry deoxygenated blood to the organs that oxygenate it. The effective arterial blood volume is that extracellular fluid which fills the arterial system.
In biology, tissue is a historically derived biological organizational level between cells and a complete organ. A tissue is therefore often thought of as an assembly of similar cells and their extracellular matrix from the same embryonic origin that together carry out a specific function. Organs are then formed by the functional grouping together of multiple tissues.
Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. It is the main storage form of glucose in the human body.
The bronchioles or bronchioli are the smaller branches of the bronchial airways in the lower respiratory tract. They include the terminal bronchioles, and finally the respiratory bronchioles that mark the start of the respiratory zone delivering air to the gas exchanging units of the alveoli. The bronchioles no longer contain the cartilage that is found in the bronchi, or glands in their submucosa.
Skeletal muscles are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle tissue, and are often known as muscle fibers. The muscle tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres.
The Purkinje fibers are located in the inner ventricular walls of the heart, just beneath the endocardium in a space called the subendocardium. The Purkinje fibers are specialized conducting fibers composed of electrically excitable cells. They are larger than cardiomyocytes with fewer myofibrils and many mitochondria. They conduct cardiac action potentials more quickly and efficiently than any of the other cells in the heart's electrical conduction system. Purkinje fibers allow the heart's conduction system to create synchronized contractions of its ventricles, and are essential for maintaining a consistent heart rhythm.
Cardiac muscle is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart. The cardiac muscle (myocardium) forms a thick middle layer between the outer layer of the heart wall and the inner layer, with blood supplied via the coronary circulation. It is composed of individual cardiac muscle cells joined by intercalated discs, and encased by collagen fibers and other substances that form the extracellular matrix.
Gaucher's disease or Gaucher disease (GD) is a genetic disorder in which glucocerebroside accumulates in cells and certain organs. The disorder is characterized by bruising, fatigue, anemia, low blood platelet count and enlargement of the liver and spleen, and is caused by a hereditary deficiency of the enzyme glucocerebrosidase, which acts on glucocerebroside. When the enzyme is defective, glucocerebroside accumulates, particularly in white blood cells and especially in macrophages. Glucocerebroside can collect in the spleen, liver, kidneys, lungs, brain, and bone marrow.
A syncytium or symplasm is a multinucleate cell which can result from multiple cell fusions of uninuclear cells, in contrast to a coenocyte, which can result from multiple nuclear divisions without accompanying cytokinesis. The muscle cell that makes up animal skeletal muscle is a classic example of a syncytium cell. The term may also refer to cells interconnected by specialized membranes with gap junctions, as seen in the heart muscle cells and certain smooth muscle cells, which are synchronized electrically in an action potential.
Striated muscle tissue is a muscle tissue that features repeating functional units called sarcomeres. The presence of sarcomeres manifests as a series of bands visible along the muscle fibers, which is responsible for the striated appearance observed in microscopic images of this tissue. There are two types of striated muscle:
Marek's disease is a highly contagious viral neoplastic disease in chickens. It is named after József Marek, a Hungarian veterinarian who described it in 1907. Marek's disease is caused by an alphaherpesvirus known as "Marek's disease virus" (MDV) or Gallid alphaherpesvirus 2 (GaHV-2). The disease is characterized by the presence of T cell lymphoma as well as infiltration of nerves and organs by lymphocytes. Viruses related to MDV appear to be benign and can be used as vaccine strains to prevent Marek's disease. For example, the related herpesvirus found in turkeys (HVT), causes no apparent disease in the birds, and continues to be used as a vaccine strain for prevention of Marek's disease.
The tunica intima, or intima for short, is the innermost tunica (layer) of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina. The endothelial cells are in direct contact with the blood flow.
The tunica media, or media for short, is the middle tunica (layer) of an artery or vein. It lies between the tunica intima on the inside and the tunica externa on the outside.
The Davson–Danielli model was a model of the plasma membrane of a cell, proposed in 1935 by Hugh Davson and James Danielli. The model describes a phospholipid bilayer that lies between two layers of globular proteins, which is both trilaminar and lipoprotinious. The phospholipid bilayer had already been proposed by Gorter and Grendel in 1925; however, the flanking proteinaceous layers in the Davson–Danielli model were novel and intended to explain Danielli's observations on the surface tension of lipid bi-layers.
Stem-cell therapy is the use of stem cells to treat or prevent a disease or condition. As of 2016, the only established therapy using stem cells is hematopoietic stem cell transplantation. This usually takes the form of a bone-marrow transplantation, but the cells can also be derived from umbilical cord blood. Research is underway to develop various sources for stem cells as well as to apply stem-cell treatments for neurodegenerative diseases and conditions such as diabetes and heart disease.
A mesoangioblast is a type of progenitor cell that is associated with vasculature walls. Mesoangioblasts exhibit many similarities to pericytes, which are found in the small vessels. Mesoangioblasts are multipotent stem cells with the potential to progress down the endothelial or mesodermal lineages. Mesoangioblasts express the critical marker of angiopoietic progenitors, KDR (FLK1). Because of these properties, mesoangioblasts are a precursor of skeletal, smooth, and cardiac muscle cells along with endothelial cells. Research has suggested their application for stem cell therapies for muscular dystrophy and cardiovascular disease.
Muscle is a soft tissue, one of the animal tissues that makes up the three different types of muscle. Muscle tissue gives skeletal muscles the ability to contract. Muscle is formed during embryonic development, in a process known as myogenesis. Muscle tissue contains special contractile proteins called actin and myosin which interact to cause movement. Among many other muscle proteins present are two regulatory proteins, troponin and tropomyosin.
A genetically modified mouse or genetically engineered mouse model (GEMM) is a mouse that has had its genome altered through the use of genetic engineering techniques. Genetically modified mice are commonly used for research or as animal models of human diseases, and are also used for research on genes. Together with patient-derived xenografts (PDXs), GEMMs are the most common in vivo models in cancer research. Both approaches are considered complementary and may be used to recapitulate different aspects of disease. GEMMs are also of great interest for drug development, as they facilitate target validation and the study of response, resistance, toxicity and pharmacodynamics.
A peg cell is a non-ciliated epithelial secretory cell within the uterine tube. These cells represent one of three epithelial cell types found within the normal fallopian tube epithelium and only make up around 10% of the total number of cells. The other two cell types are ciliated columnar and intercalary cells. The ratio of these remaining cells is dictated by an individual's hormone status. Peg cells secrete nutrients for the egg cell.
