Types Of Connective Tissues And Their Functions – The term tissue is used to describe a group of cells found together in the body. The cells in a tissue have the same embryonic origin. Microscopic observation reveals that the cells in a tissue have the same morphological characteristics and are arranged in a regular pattern so as to achieve the function of the tissue. From an evolutionary perspective, tissues emerged in more complex organisms. For example, multicellular protists, ancient eukaryotes, do not have cells arranged in tissues.

Although there are many types of cells in the human body, they are organized into four broad categories of tissue: 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. Disruption of the structure is a sign of injury or disease. These changes can be detected through histology, which is a microscopic study of the appearance, organization and function of tissue.

Types Of Connective Tissues And Their Functions

Epithelial tissue, also referred to as epithelium, refers to the sheets of cells that cover the external surfaces of the body, line internal cavities and ducts, and form certain glands. Connective tissue, as the name suggests, binds the body’s cells and organs together and functions in the protection, support, and integration of all parts of the body. Muscle tissue is excitable, responding to stimulation and contracting to produce movement, and comes in three main types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle in the heart. Nervous tissue is also excitatory, allowing the propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body (Figure 1).

Classification Of Connective Tissues: Types & Functions

Figure 1. Four Types of Tissue: Body. These four types of tissue are exemplified in nervous tissue, stratified squamous epithelial tissue, heart muscle tissue, and connective tissue in the small intestine. Clockwise from neural tissue, LM × 872, LM × 282, LM × 460, LM × 800. (Micrographs provided by the Regents of the University of Michigan Medical School © 2012)

The next level of organization is the organ, where several types of tissue unite to form a working unit. Just as knowing the structure and function of cells helps you study tissues, knowledge of tissues will help you understand how organs function. Epithelial and connective tissues are discussed in detail in this chapter. Muscle and nervous tissue will only be discussed briefly in this chapter.

A zygote, or fertilized egg, is a single cell formed by the fusion of an egg and sperm. After fertilization, the zygote undergoes a rapid mitotic cycle, producing many cells to form the embryo. The first embryonic cells produced have the ability to differentiate into any type of cell in the body and are, therefore, called totipotent, which means that each cell has the capacity to divide, differentiate and develop into a new organism. As cell proliferation progresses, three main cell lineages are formed within the embryo. Each of these embryonic cell lineages forms a distinct germ layer that ultimately forms all the tissues and organs of the human body. Each germ layer is identified based on its relative position: ectoderm (

– = “mind”). Figure 2 shows the types of tissues and organs associated with each of the three germ layers. Note that epithelial tissue originates from all three layers, while nervous tissue originates primarily from the ectoderm and muscle tissue from the mesoderm.

Connective Tissue: Types, Function, Examples, Disorders

Tissue membranes are thin layers or sheets of cells that cover the outside of the body (e.g. skin), organs (e.g. pericardium), internal channels leading to the outside of the body (e.g. abdominal mesentery). ), and a movable joint cavity lining. There are two basic types of tissue membranes: connective tissue and epithelial membranes (Figure 3).

Figure 3. Tissue Membrane. The two broad categories of tissue membranes in the body are (1) connective tissue membranes, which include synovial membranes, and (2) epithelial membranes, which include mucous membranes, serous membranes, and cutaneous membranes, in other words, skin.

Connective tissue membranes are formed only from connective tissue. These membranes wrap around organs, such as the kidneys, and line our moving joints. Synovial membrane is a type of connective tissue membrane that lines the joint cavity that can be moved freely. For example, synovial membranes surround the shoulder, elbow, and knee joints. Fibroblasts in the inner layer of the synovial membrane release hyaluronan into the joint cavity. Hyaluronan effectively traps available water to form synovial fluid, a natural lubricant that allows joint bones to move freely against each other without much friction. This synovial fluid easily exchanges water and nutrients with the blood, as do all body fluids.

Epithelial membranes consist of epithelium attached to a layer of connective tissue, such as your skin. The mucous membrane is also a combination of connective tissue and epithelium. Sometimes called mucosa, these epithelial membranes line body cavities and hollow tubes that are open to the external environment, and include the digestive, respiratory, excretory, and reproductive tracts. Mucus, produced by the exocrine glands of the epithelium, covers the epithelial layer. The underlying connective tissue, called the lamina propria (literally “layer itself”), helps support the fragile epithelial layer.

Solved] Identifying The Functions And Locations Of Loose Connective…

The serous membrane is an epithelial membrane consisting of mesodermally derived epithelium called mesothelium which is supported by connective tissue. This membrane lines the body’s coelom cavity, which is a cavity that does not open to the outside, and covers the organs that are located inside the cavity. They are essentially membrane sacs, with mesothelium lining the inside and connective tissue on the outside. The serous fluid secreted by the thin squamous mesothelium cells lubricates the membrane and reduces abrasion and friction between organs. Serous membranes are identified based on their location. Three serous membranes line the chest cavity; the two pleura which cover the lungs and the pericardium which covers the heart. The fourth, the peritoneum, is a serous membrane in the abdominal cavity that covers the abdominal organs and forms a double sheet of mesentery that holds many of the digestive organs.

The skin is an epithelial membrane which is also called the skin membrane. It is a stratified squamous epithelial membrane that lies over the connective tissue. The apical surface of this membrane is exposed to the external environment and is covered with dead keratin cells that help protect the body from desiccation and pathogens. Different types of connective tissue maintain the shape of organs throughout the body. Connective tissue provides a matrix that supports and physically connects other tissues and cells together in organs. Connective tissue interstitial fluid provides metabolic support to cells as a medium for the diffusion of nutrients and waste products.

In contrast to other types of tissue (epithelium, muscle, and nerve), which consist mostly of cells, the main constituent of connective tissue is the extracellular matrix (ECM). The extracellular matrix consists of various combinations of protein fibers (such as collagen and elastic fibers) and ground substance. The basic substance is a complex of anionic, hydrophilic proteoglycans, glycosaminoglycans (GAG), and multiadhesive glycoproteins (laminin, fibronectin, etc.). As explained briefly in Chapter 4 regarding the basal lamina, these glycoproteins help stabilize the ECM by binding to other matrix components and to integrins in the cell membrane. The hydrated nature of the ground substance of connective tissue provides a medium for the exchange of nutrients and metabolic waste between cells and the blood supply.

The diversity of connective tissue types in the body reflects differences in the composition and number of cells, fibers, and ground substances that together are responsible for the extraordinary structural, functional, and pathological diversity of connective tissue.

Levels Of Organization And Tissue Types

Connective tissue originates from embryonic mesenchyme, which is tissue that develops mainly from the middle layer of the embryo, namely the mesoderm (Figure 5-1). The mesenchyme consists mostly of a viscous ground substance with few collagen fibers. Mesenchymal cells are undifferentiated and have large nuclei, with prominent nucleoli and fine chromatin. They are often said to be “spindle-shaped,” with little cytoplasm extending into two or more thin cytoplasmic processes. Mesodermal cells migrate from their original site in the embryo, surrounding and penetrating the developing organs. In addition to producing all types of connective tissue proper and the specialized connective tissue of bone and cartilage, embryonic mesenchyme includes stem cells for other tissues such as blood, vascular endothelium, and muscle. This chapter focuses on actual connective tissue.

Fibroblasts and certain other cells are commonly found in connective tissue (Figure 5–2 and Table 5–1). Fibroblasts originate locally from mesenchymal cells and are permanent residents of connective tissue; Other cells found here, such as macrophages, plasma cells, and mast cells, originate from hematopoietic stem cells in the bone marrow, circulate in the blood, and then migrate to connective tissue where they function. White blood cells (leukocytes) are transient cells in most connective tissues; they also originate in the bone marrow and migrate to connective tissue where they function for several days, then die via apoptosis.

Fibroblasts (Figure 5-3), the most common cells in connective tissue, produce and maintain most of the tissue’s extracellular components. Fibroblasts synthesize and secrete collagen (the most abundant protein in the body) and elastin, which form large fibers, as well as GAGs, proteoglycans, and multiadhesive glycoproteins that make up the ground substance. As explained later, most of the secreted ECM components undergo further modification outside the cell

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