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Connective Tissue: Tissue that supports and binds other tissues. It consists of Connective tissue cells embedded in a large amount of Extracellular matrix.

Tissues

JoVE 10696

Cells with similar structure and function are grouped into tissues. A group of tissues with a specialized function is called an organ. There are four main types of tissue in vertebrates: epithelial, connective, muscle, and nervous.

Epithelial tissue consists of thin sheets of cells and includes the skin and the linings of internal organs and body cavities. Epithelial cells are tightly packed, providing a barrier against injury, infection, and water loss. Epithelial tissue can be a single layer called simple epithelium, or multiple layers called stratified epithelium. In stratified epithelium, such as the skin, the outer cells—which are subject to damage—are replaced through the division of cells underneath. Epithelial cells have a variety of shapes, including squamous (flattened), cuboid, and columnar. Some epithelial tissues absorb or secrete substances, such as the lining of the intestines. Connective tissue is composed of cells within an extracellular matrix and includes loose connective tissue, fibrous connective tissue, adipose (fat) tissue, cartilage, bone, and blood. Although the characteristics of connective tissue vary greatly, their general function is to support and attach multiple tissues. For example, tendons are made of fibrous connective tissue and attach muscle to bone. Blood transports oxygen, nutrients and waste produ

 Core: Biology

Skeletal Muscle Anatomy

JoVE 10867

Skeletal muscle is the most abundant type of muscle in the body. Tendons are the connective tissue that attaches skeletal muscle to bones. Skeletal muscles pull on tendons, which in turn pull on bones to carry out voluntary movements.

Skeletal muscles are surrounded by a layer of connective tissue called epimysium, which helps protect the muscle. Beneath the epimysium, an additional layer of connective tissue, called perimysium, surrounds and groups together subunits of skeletal muscle called fasciculi. Each fascicle is a bundle of skeletal muscle cells, or myocytes, which are often called skeletal muscle fibers due to their size and cylindrical appearance. Between the muscle fibers is an additional layer of connective tissue called endomysium. The muscle fiber membrane is called the sarcolemma. Each muscle fiber is made up of multiple rod-like chains called myofibrils, which extend across the length of the muscle fiber and contract. Myofibrils contain subunits called sarcomeres, which are made up of actin and myosin in thin and thick filaments, respectively. Actin contains myosin-binding sites that allow thin and thick filaments to connect, forming cross bridges. For a muscle to contract, accessory proteins that cover myosin-binding sites on thin filaments must be displaced to enable the formation of cross bridges. During muscle contracti

 Core: Biology

Histotypic Tissue Culture

JoVE 5787

Although two-dimensional tissue culture has been common for some time, cells behave more realistically in a three-dimensional culture, and more closely mimics native tissue. This video introduces histotypic tissue culture, where the growth and propagation of one cell line is done in an engineered three-dimensional matrix to reach high cell density. Here, we show the…

 Bioengineering

Bone Structure

JoVE 10864

Within the skeletal system, the structure of a bone, or osseous tissue, can be exemplified in a long bone, like the femur, where there are two types of osseous tissue: cortical and cancellous.

Covering the cortical, or compact bone, is a membrane called the periosteum, which contains connective tissue, capillaries, and nerves. The outer, solid layer—found along the diaphysis, the shaft—forms a dense protective shell around the medullary canal—the cavity that stores yellow bone marrow, composed primarily of fat cells. This space is also covered in a thin lining—the endosteum in which bone growth, remodeling, and repair occur. Within the dense layer of cortical bone are osteons—structural units, arranged in concentric rings called lamellae, that contain osteoblasts—cells critical for bone formation and growth. These cells eventually mature into osteocytes in the hollow space, the lacuna. Through the center of each osteon runs the Haversian canal, which contains more blood and lymphatic vessels, as well as nerve fibers. Towards the rounded ends of the long bone, the epiphyses is the second type of osseous tissue, known as the cancellous, or spongy, bone. This inner layer is composed of a honeycomb-like network of trabeculae—grouped arrangements that form along the lines of stress points to maximize strengt

 Core: Biology

High-frequency Ultrasound Imaging of the Abdominal Aorta

JoVE 10397

Source: Amelia R. Adelsperger, Evan H. Phillips, and Craig J. Goergen, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana


High-frequency ultrasound systems are used to acquire high resolution images. Here, the use of a state-of-the-art system will be demonstrated to image the morphology and …

 Biomedical Engineering

Anatomy of the Heart

JoVE 10886

The human heart is made up of three layers of tissue that are surrounded by the pericardium, a membrane that protects and confines the heart. The outermost layer, closest to the pericardium, is the epicardium. The pericardial cavity separates the pericardium from the epicardium. Beneath the epicardium is the myocardium, the middle layer, and the endocardium, the innermost layer. There are four chambers of the heart: the right atrium, the right ventricle, the left atrium, and the left ventricle. These compartments have two types of valves—atrioventricular and semilunar—that prevent blood from flowing in the wrong direction. The right atrium receives blood from the coronary sinus and the superior and inferior vena cavae. This blood goes into the right ventricle via the right atrioventricular (or tricuspid) valve, a flap of connective tissue that prevents the backflow of blood into the atrium. Then, the blood leaves the heart, traveling through the pulmonary semilunar valve into the pulmonary artery. Blood is then carried back into the left atrium of the heart by the pulmonary veins. Between the left atrium and the left ventricle, the blood is again passed through an atrioventricular valve that prevents backflow into the atrium. This atrioventricular valve is called the bicuspid (or mitral) valve. The blood passes through the left ventricle into the aorta

 Core: Biology

Gastrulation

JoVE 10909

Gastrulation establishes the three primary tissues of an embryo: the ectoderm, mesoderm, and endoderm. This developmental process relies on a series of intricate cellular movements, which in humans transforms a flat, “bilaminar disc” composed of two cell sheets into a three-tiered structure. In the resulting embryo, the endoderm serves as the bottom layer, and stacked directly above it is the intermediate mesoderm, and then the uppermost ectoderm. Respectively, these tissue strata will form components of the gastrointestinal, musculoskeletal and nervous systems, among other derivatives. Depending on the species, gastrulation is achieved in different ways. For example, early mouse embryos are uniquely shaped and appear as “funnels” rather than flat discs. Gastrulation thus produces a conical embryo, arranged with an inner ectoderm layer, outer endoderm, and the mesoderm sandwiched in between (similar to the layers of a sundae cone). Due to this distinct morphological feature of mice, some researchers study other models, like rabbit or chicken—both of which develop as flat structures—to gain insights into human development. One of the main morphological features of avian and mammalian gastrulation is the primitive streak, a groove that appears down the vertical center of the embryo, and through which cells migrate t

 Core: Biology

Levels of Organization

JoVE 10648

Biological organization is the classification of biological structures, ranging from atoms at the bottom of the hierarchy to the Earth’s biosphere. Each level of the hierarchy represents an increase in complexity that builds upon the previous level.

The most basic levels include atoms, molecules, and biomolecules. Atoms, the smallest unit of ordinary matter, are composed of a nucleus and electrons. Molecules comprise two or more atoms held together by chemical bonds, most commonly covalent, ionic, or metallic bonds. Biomolecules are molecules found in living organisms, including proteins, nucleic acids, lipids, and carbohydrates. Biomolecules are often polymers—large molecules that are created from smaller, repeating units. For instance, proteins are composed of amino acids, and nucleic acids are composed of nucleotides. Biomolecules can be endogenous or exogenous. Endogenous means that the biomolecule is produced inside a living organism. Biomolecules can also be consumed; for example, a cow gets carbohydrates from digesting grass (exogenous), but the grass must produce the carbohydrates through photosynthesis (endogenous). The next hierarchical level comprises subcellular structures called organelles. Organelles are made up of biomolecules and compartmentalize eukaryotic cells. Organelle means “little organ” as

 Core: Biology

Joints

JoVE 10865

Joints, also called articulations or articular surfaces, are points at which ligaments or other tissues connect adjacent bones. Joints permit movement and stability, and can be classified based on their structure or function.

Structural joint classifications are based on the material that makes up the joint as well as whether or not the joint contains a space between the bones. Joints are structurally classified as fibrous, cartilaginous, or synovial. The bones of a fibrous joint are connected by fibrous tissue and have no space, or cavity, between them. Thus, fibrous joints cannot move. Although the skull appears to be a single large bone, it includes several bones that are connected by fibrous joints called sutures. Syndesmoses, the second type of fibrous joint found in the fibula (calf bone), allow more movement than sutures. The third type of fibrous joint, gomphoses, connect teeth to their sockets. The bones of cartilaginous joints are connected by cartilage and permit minimal movement. The two types of cartilaginous joints, synchondroses and symphyses, differ in the kind of cartilage that connects the bones (hyaline cartilage and fibrocartilage, respectively). The epiphyseal plates in the bones of growing children contain synchondroses. Symphyses connect vertebrae as well as the pubic bones. Synovial joints, found in the elbows, s

 Core: Biology

Collagen Hydrogels

JoVE 5786

Collagen is another widely used biomaterial that has found popularity in commercial applications, such as photography. Collagen has more recently been used in tissue engineering applications, by creating hydrogels that provide structure to engineered tissue.


This video introduces collagen as a biomaterial, demonstrates how it is…

 Bioengineering
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