Tissues
DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Tissues CRT04101 · Anatomy, Physiology and Pathology START READING NOTES Study Tissues using the sections below. Use the topic navigation to continue through Anatomy, Physiology and Pathology. Contents of This Topic Four primary tissue types interweave to form the fabric of the body. Describe its general role, the terms would most likely be: Tissues are organized into organs such as the kidneys and the heart. EPITHILIAL TISSUE Epithelia form boundaries between different environments. In its role as an interface tissue, epithelium accomplishes many functions, including CLASSIFICATION OF EPITHELIA They are typically found where absorption and filtration occur and a thin epithelial barrier is desirable. Tissues 1.Squamous cells are flattened and scalelike SIMPLE EPITHELIA The cells of a simple squamous epithelium are flattened laterally, and their cytoplasm is sparse. Simple cuboidal epithelium consists of a single layer of cells as tall as they are wide . Simple columnar epithelium is seen as a single layer of tall, closely packed cells, aligned like soldiers in a row. 1) Dense microvilli on the apical surface of absorptive cells The cells of pseudostratified columnar epithelium vary in height. The short cells are relatively unspecialized and give rise to the taller cells. STRATIFIED EPITHELIA Stratified squamous epithelium is the most widespread of the stratified epithelia. Transitional epithelium forms the lining of hollow urinary organs, which stretch as they fill with urine. CONNECTIVE TISSUE There are four main classes of connective tissue and several subclasses. Its major functions include COMMON CHARACTERISTICS OF CONNECTIVE TISSUE STRUCTURAL ELEMENTS OF CONNECTIVE TISSUE GROUND SUBSTANCE FIBERS Collagen fibers are constructed primarily of the fibrous protein collagen. Elastic fibers are long, thin fibers that form branching networks in the extracellular matrix. Reticular fibers are short, fine, collagenous fibers and are continuous with collagen fibers. CELLS The primary blast cell types by connective tissue class are TYPES OF CONNECTIVE TISSUE CONNECTIVE TISSUE PROPER AREOLAR CONNECTIVE TISSUE ADIPOSE (FAT) TISSUE Adipose tissue is richly vascularized, indicating its high metabolic activity. RETICULAR CONNECTIVE TISSUE DENSE REGULAR CONNECTIVE TISSUE DENSE IRREGULAR CONNECTIVE TISSUE This type of tissue forms sheets in body areas where tension is exerted from many different directions. CARTILAGE It receives its nutrients by diffusion from blood vessels located in the connective tissue membrane surrounding it. Cartilage matrix also contains an exceptional amount of tissue fluid; in fact, cartilage is up to 80% water! There are three varieties of cartilage: HYALINE CARTILAGE Hyaline cartilage provides firm support with some pliability. Most of the embryonic skeleton is formed of hyaline cartilage before bone is formed. ELASTIC CARTILAGE FIBROCARTILAGE BONE (OSSEOUS TISSUE) Osteoblasts produce the organic portion of the matrix; then bone salts are deposited on and between the fibers. BLOOD TISSUES Groups of cells that are similar in structure and perform a common or related function are called tissues. Four primary tissue types interweave to form the fabric of the body. These basic tissues are: 1.Epithelial Tissue 2.Connective Tissue Muscle Tissue 4.Nervous tissue Each has numerous subclasses or varieties. Describe its general role, the terms would most likely be: Covering (epithelial) Support (connective) Movement (muscle) Control (nervous). However, these terms reveal only a fraction of the functions that each tissue performs. Tissues are organized into organs such as the kidneys and the heart. Most organs contain all four tissue types, and their arrangement determines the organ’s structure and capabilities. The study of tissues is called Histology EPITHILIAL TISSUE Epithelial tissue, or an epithelium, is a sheet of cells that covers a body surface or lines a body cavity. Covering and lining epithelium forms the outer layer of the skin, dips into and lines the open cavities of the cardiovascular, digestive, and respiratory systems, and covers the walls and organs of the closed ventral body cavity. Epithelia form boundaries between different environments. For example, the epidermis of the skin lies between the inside and the outside of the body, and epithelium lining the urinary bladder separates underlying cells of the bladder wall from urine. Nearly all substances received or given off by the body must pass through an epithelium In its role as an interface tissue, epithelium accomplishes many functions, including 1.Protection 2.Absorption Filtration Excretion 5.Secretion Sensory reception CLASSIFICATION OF EPITHELIA Each epithelium is given two names. The first name indicates the number of cell layers present; the second describes the shape of its cells. Based on the number of cell layers, there are simple and stratified epithelia. Simple epithelia are composed of a single cell layer. They are typically found where absorption and filtration occur and a thin epithelial barrier is desirable. Stratified epithelia, consisting of two or more cell layers stacked one on top of the other, are common in high-abrasion areas where protection is important, such as the skin surface and the lining of the mouth. Tissues In cross section, all epithelial cells have six sides, and an apical surface view of an epithelial sheet looks like a honeycomb. This polyhedral shape allows the cells to be closely packed. However, epithelial cells vary in height, and on that basis, there are three common shapes of epithelial cells. 1.Squamous cells are flattened and scalelike 2.Cuboidal cells are boxlike, approximately astall as they are wide. Columnar cells are tall and column shaped. In each case, the shape of the nucleus conforms to that of the cell. Tissues The nucleus of a squamous cell is a flattened disc; that of a cuboidal cell is spherical; and a columnar cell nucleus is elongated from top to bottom and usually located close to the cell base. SIMPLE EPITHELIA The simple epithelia are most concerned with absorption, secretion, and filtration. Because they consist of a single cell layer and are usually very thin, protection is not one of their specialties The cells of a simple squamous epithelium are flattened laterally, and their cytoplasm is sparse. In a surface view, the close-fitting cells resemble a tiled floor. Tissues Thin and often permeable, this epithelium is found where filtration or