HUMAN BODY ANATOMY

WHAT IS A TISSUE? The term  tissue  is used to describe a group of cells found together in the body. The cells within a tissue share a common embryonic origin. Microscopic observation reveals that the cells in a tissue share morphological features and are arranged in an orderly pattern that achieves the tissue’s functions. From the evolutionary perspective, tissues appear in more complex organisms. For example, multicellular protists, ancient eukaryotes, do not have cells organized into tissues. Although there are many types of cells in the human body, they are organized into four broad categories of tissues: epithelial, connective, muscle, and nervous. Each of these categories is characterized by specific functions that contribute to the overall health and maintenance of the body. A disruption of the structure is a sign of injury or disease. Such changes can be detected through  histology , the microscopic study of tissue appearance, organization, and function. Th...

EPITHELIAL TISSUE KEY FACTS Epithelial tissue is composed of cells laid together in sheets with the cells tightly connected to one another. Epithelial layers are avascular, but innervated. Epithelial cells have two surfaces that differ in both structure and function. Glands, such as exocrine and endocrine, are composed of epithelial tissue and classified based on how their secretions are released. Functions of the Epithelium Epithelia tissue forms boundaries between different environments, and nearly all substances must pass through the epithelium. In its role as an interface tissue, epithelium accomplishes many functions, including: Protection for the underlying tissues from radiation, desiccation, toxins, and physical trauma. Absorption of substances in the digestive tract lining with distinct modifications. Regulation and excretion of chemicals between the underlying tissues and the body cavity. The secretion of hormones into the blood vascular system. The secretion ...

CONNECTIVE TISSUE DEFINITION Connective tissue , group of tissues in the body that maintain the form of the body and its organs and provide cohesion and internal support. The connective tissues include several types of fibrous tissue that vary only in their density and cellularity, as well as the more specialized and recognizable variants—bone, ligaments, tendons, cartilage, and adipose(fat) tissue. COMPONENTS OF CONNECTIVE TISSUE All forms of connective tissue are composed of (1) extracellular  fibres, an amorphous matrix called ground substance, and  stationary and migrating cells. The proportions of these components vary from one part of the body to another depending on the local structural requirements. In some areas, the connective tissue is loosely organized and highly cellular; in others, its fibrous components predominate; and in still others, the ground substance may be its most  conspicuous  feature. The ana...

Muscle Tissue Definition Muscle tissue is a specialized tissue found in animals which functions by contracting, thereby applying forces to different parts of the body. Muscle tissue consists of fibers of muscle cells connected together in sheets and fibers. Together these sheets and fibers and known as muscles, and control the movements of an organisms as well as many other contractile functions. There are three different types of muscle found in animals, depending on their use. While these muscles differ slightly, they function in a similar way. Function of Muscle Tissue Muscle tissue functions as a single unit, and is often connected to the same nerve bundles. A nerve impulse traveling from the brain or another outside signal tells the muscle to contract. The nerve impulse is transferred almost instantaneously to all the nerve cells in the muscle tissue, and the entire muscle contracts. At the cellular level, each muscle cell has a complex of proteins containing actin an...

Nervous Tissue Definition Nervous tissue is the term for groups of organized cells in the nervous system, which is the organ system that controls the body’s movements, sends and carries signals to and from the different parts of the body, and has a role in controlling bodily functions such as digestion. Nervous tissue is grouped into two main categories: neurons and neuroglia. Neurons, or nerves, transmit electrical impulses, while neuroglia do not; neuroglia have many other functions including supporting and protecting neurons. Function of Nervous Tissue Nervous tissue makes up the nervous system.If you want to know more about the nervous system click here. Types of Nervous Tissue Neurons Neurons are cells that can transmit signals called nerve impulses, or action potentials. An action potential is a quick rise and fall in the electrical membrane potential of the neuron, which transmits signals from one neuron to the next. These are the different types of neurons: ...