Anatomy and Physiology Chapter 3 Brief: Tissues
What are the types of connective tissue?
All connective tissues consist of living cells surrounded by a matrix. Their major difference reflect specific cell types, fiber types, and the number of fibers in the matrix. From most rigid to softest or most fluid, the major connective tissue are; bone, cartilage, dense connective tissue, loose connective tissue, and blood Bone: is sometime called osseous tissue; composed of osteocyte (bone cells) sitting in cavities called lacunae. Its pits are surrounded by layers of a very matrix that contains calcium salts in addition to large numbers of collagen fibers. Due to its nature, bone has an exceptional ability to protect and support other body organs. Cartilage: Less hard and more flexible than bone. Its major cell type is chondrocytes. Its major cell type is chondrocytes (cartilage cells), and found in only a few places in the body. Most widespread is hyaline cartilage, which has abundant collagen fibers hidden by a rubbery matrix with a glassy, blue-white appearance. Forms the supporting structures of the larynx, or voice box, attaches the ribs to the breastbone, and covers the ends of many bones, where they form joints. The skeleton of a fetus is made largely of hyaline cartilage, but by the time the baby is born, most is replaced by bone. The exceptions include the epiphyseal, or growth, plates in long bones, which allow the bones to grow in length during youth. Highly compressible fibrocartilage forms the cushion-like disk between the vertebrae of the spinal column. Elastic cartilage is found in structures with elasticity. Loose connective tissue: loose connective tissues are softer and have more cells and fewer fibers than any other connective tissue type except blood. Areolar Tissue: Protects the body organs it wraps. Its functions is as a universal packing tissue and connective tissue "glue" because it holds the internal organs together, in their proper position. Lamina propria, underlies all mucous membranes. Its fluid matrix contains all types of fibers, which form loose network. Due to its loose and fluid nature, areolar connective tissue provides a reservoir of water and salts for the surrounding tissues, and essentially all body cells obtain their nutrients from and essentially all body cells obtain their nutrients from, and release their wastes into this "tissue fluid". When a body region is inflamed, the areolar tissue in the area soaks up the excess fluid like a sponge, and the area swells and becomes puffy, a condition called edema. Many types of phagocytes wander through this tissue, scavenging for bacteria, dead cells, and other debris, which they destroy. Adipose tissue: Commonly called fat. Because it is an areolar tissue in which adipose (fat) cells predominate. Adipose (fat) tissue forms the subcutaneous (under the skin) tissue beneath the skin, where it insulates the body and protects it from bumps and extremes of both heat and cold. Adipose (fat) tissue also protects some organs individually; kidney surrounded by a capsule of fat, and adipose tissue cushions the eyeballs in their sockets. Adipose tissue, where fat is stored, can also be used for fuel if needed. Reticular Connective Tissue: consists of a delicate network of interwoven reticular fibers associated with reticular cells, which resemble fibroblasts. Reticular tissue is limited to certain sites: it forms the stroma ("bed" or "mattress") or internal framework of an organ. Stroma can support many free blood cells (largely lymphocytes) in lymphoid organs such as lymph nodes, the spleen, and bone marrow. Blood or Vascular Tissue: is a connective tissue because it consists of blood cells surrounded by a nonliving, fluid matrix called blood plasma. The "fibers" of blood are soluble protein molecules that become visible only during blood clotting.
What is a Nerve Tissue?
All neurons receive and conduct electrochemical impulses from one part of the body to another; irritability and conductivity are their major functional characteristics. A special group of supporting cells called neuroglia insulate, support, and protect the delicate neurons in the structures of the nervous system; the brain, the spinal cord, and nerves.
What is the epithelial tissue and its characteristics?
Epithelial Tissue: is the lining, covering and glandular tissue of the body. Epithelial functions include protection, absorption, filtration, and secretion. Special characteristics of Epithelium - other than glandular epithelium, epithelial cells fit closely together to form continuous sheets. Neighboring cells are bound together at many points by specialized cell junctions, including desmosomes and tight junctions. - Membranes always have one free surface or edge. This is called apical surface, and it is exposed to the body's exterior or to the cavity of an internal organ. The exposed surfaces of some epithelia are slick and smooth, but others exhibit cell surface modifications, such as microvilli or cilia. - Lower surface of an epithelium rests on a basement membrane, a structure-less material secreted by both the epithelial cells and the connective cells that abut the epithelium. - Epithelial tissues have no blood supply of their own (avascular) and depend on diffusion from the capillaries in the underlying connective tissue for food and oxygen. - if well nourished, epithelial cells regenerate themselves easily.
Explain the function of Connective tissue and classify the different types
Found everywhere in the body, it is the most abundant and widely distributed of the tissue types. It has many functions, but connective tissue are primarily involved in protecting, supporting, and binding together other body tissues. Common characteristics of connective tissue: - Variations in blood supply: Most connective tissues are well vascularized (meaning they have a good blood supply), but there are exceptions such as; tendons and ligaments having a poor blood supply, and cartilages being avascular. These injuries heal very slowly when injured (as people would say, they'd rather have an injured bone than an injured ligament) - Extracellular matrix: Connective tissues are made up of many different types of cells plus varying amounts of a non-living substance found outside the cells, called the extracellular matrix. Hence, "extra" for being outside.
Explain the function of connective tissue and classify the different type
Found everywhere in the body, it is the most abundant and widely distributed of the tissue types. It has many functions, but connective tissue are primarily involved in protecting, supporting, and binding together other body tissues. Common characteristics of connective tissue: - Variations in blood supply: Most connective tissues are well vascularized (meaning they have a good blood supply), but there are exceptions such as; tendons and ligaments having a poor blood supply, and cartilages being avascular. These injuries heal very slowly when injured (as people would say, they'd rather have an injured bone than an injured ligament) - Extracellular matrix: Connective tissues are made up of many different types of cells plus varying amounts of a non-living substance found outside the cells, called the extracellular matrix. Hence, "extra" for being outside.
What is a muscle tissue, and what are its types?
Muscle tissues are highly specialized to contract or shorten, to produce movement. - Skeletal Muscle: Packaged by connective tissue sheets into organs called skeletal muscles, which are attached to the skeleton. These muscles, which can be controlled voluntarily, form the flesh of the body, the so called muscular. The cells of skeletal muscle are along, cylindrical, multinucleate, and they have obvious striations (stripes). As skeletal muscle cells are elongated to provide a long axis for contraction, they are often called muscle fibers. - Cardiac Muscle: Found only in the heart, the heart act as pump and propels blood through the blood vessels. Has striations, and cardiac cells are uni-nucleate (single nucleus), relatively short, branching cells that fit tightly together at junctions called intercalated discs. Contain gap junctions that allow ions to pass freely from cell to cell. Cardiac muscle is an involuntary control. - Smooth (visceral) Muscle: is called because no striations are visible. Individual cells have a single nucleus and are spindle-shaped (pointed at each end). Smooth muscle found in the walls of hollow organs such as the stomach, uterus, and blood vessels.
What are the classification of Epithelium?
Simple Epithelia (one layer of cells): Most concerned with absorption, secretion, and filtration. As it is usually very thin, protection is not one of their specialties. Simple Squamous Epithelium (flat one layer of cells): Single thin layer of squamous cell resting on a basement membrane. This epithelium usually forms membranes where filtration or exchange of substances by rapid diffusion occurs. Simple squamous epithelium is in the air sacs on the lung, where oxygen and carbon dioxide are exchanged, and it forms the walls of capillaries, where nutrients and gases pass between the tissue cells and the blood in the capillaries. Simple squamous epithelium also forms serous membranes, or serosae, the slick membranes that line the ventral body cavity and cover the organs in that cavity. Simple Cuboidal (Cube-like) Epithelium: One layer of cuboidal cells resting on a basement membrane, is common in glands and their ducts. Forms the walls of the kidney tubules and covers the surface of the ovaries. Simple Columnar Epithelium (single layer, column-like): Single layer of tall cells that fit closely together. Goblet cells, which produce a lubricating mucus, are often seen in this type of epithelium. Simple columnar epithelium lines the entire length of the digestive tract from the stomach to the anus. Epithelial membranes that line body cavities open to the body exterior are called mucosae or mucous membranes. Pseudostratified columnar epithelium (Variation in cell lengths, many cell layers and column-like): All cells of pseudostratified columnar epithelium rest on a basement membrane. Cells differs in height and their nuclear appear at different heights above the basement membrane. Like simple columnar epithelium, it mainly focuses on absorption and secretion. That which lines the respiratory tract is called pseudostratified ciliated columnar epithelium. The mucus produced by the goblet cells in this epithelium traps dusts and other debris, and the cilia propel the mucus upward and away from the lungs. Stratified Epithelia: Consisting of two or more cell layers. Being considerably more durable than simple epithelia, these epithelia function primarily to protect. Stratified squamous epithelium (many cell layers, flat): Most common stratified cell in the body, usually consisting of several layers of cells. The cells at the free edge are squamous cell, whereas those close to the basement membrane are cuboidal or columnar. Stratified squamous epithelium is found in sites that receive a good deal of abuse or friction, such as the esophagus, the mouth and the outer portion of the skin. Stratified Cuboid and stratified columnar epithelia (many layers, cube-like and many layer, column-like): The surface being cuboidal in shape, and typically has just two cell layers. The surface cells of stratified columnar epithelium are columnar cells, but its basal cells vary in size and shape. Found mainly in the ducts of large glands. Transitional Epithelium: Highly modified, stratified squamous epithelium that forms the lining of only a few organs - the urinary bladder, the ureters, and part of the urethra. All these organs are part of the urinary system and are subject to considerable stretching. Cells of the basal layer are cuboidal and columnar; those at the free surface vary in appearance. When the organ is not stretched, the membrane is many layered, and the superficial cells are rounded and domelike. When the organ is distended with urine, the epithelium thins, and the surface cells flatten and become squamous-like. This ability of transitional cells to slide past one another and change their shape allows the ureter wall to stretch as a greater volume of urine flows through that tube-like organ. In the bladder, it allows more urine to be stored. Glandular Epithelium: a gland consists of one or more cells that make and secrete a particular product. This product, called a secretion, typically contains protein molecules in an aqueous fluid. Secretion also indicates that an active process in which the glandular cells obtain needed materials from the blood and use them to make their secretion when they then discharge. Two major types of glands develop from epithelial sheets: - Endocrine gland lose their connection to the surface (duct); thus they are often called ductless glands. Their secretions (all-hormones) diffuse directly into the blood vessels that weave through the glands. Examples of endocrine glands include the thyroid, adrenals, and pituitary. - Exocrine glands retain their ducts, and their secretions empty through the ducts to the epithelial surface. Exocrine glands, and pancreas, are both internal and external.
What is the extracellular matrix (refer to a diagram)
The extracellular matrix is produced by the connective tissue cells and then secreted to their exterior. It has two elements, a structure less ground substance and fibers. The ground substance of the matrix is composed largely of water plus adhesion proteins and large, charged polysaccharide molecules. The cell adhesion proteins serve as a glue that allows the connective tissue cells to attach themselves to the matrix fibers embedded in the ground substance. The charged polysaccharide molecules trap water as they intertwine. As these polysaccharide become more abundant, they cause the matrix to vary from fluid to gel-like to firm in its consistency. The various types and amounts of fibers that are deposited in the matrix, and form part of it, are depended upon the connective tissue type. These include collagen (white) fibers distinguished by their high tensile strength; elastic (Yellow) fibers, which have the ability to be stretched and then recoil; and reticular fibers, which are fine collagen fibers that form the internal "skeleton" of soft organs such as the spleen. The building blocks, or monomers, of these fibers are made by the connective tissue cells and secreted into the ground substance in the extracellular space, where they join together to form the various fiber types. Because of extracellular matrix, connective tissue is able to form a soft packing tissue around other organs, to bear weight, and to withstand stretching and other abuses, such as abrasion that no other tissue could endure, but there is variation. At one extreme, fat tissue is composed mostly of cells, and the matrix is soft. At the opposite extreme, bone and cartilage have very few cells and large amounts of hard matrix, which makes them extremely strong.
