C6 Refer Again to Figure Lg 1 1 Show the Pattern of Ciculation

Learning Objectives

By the terminate of this department, y'all will be able to:

• Identify the iv master tissue types
• Hash out the functions of each tissue type
• Chronicle the structure of each tissue type to their office
• Discuss the embryonic origin of tissue
• Place the three major germ layers
• Identify the principal types of tissue membranes

The term tissue is used to describe a grouping of cells found together in the body. The cells within a tissue share a mutual 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 circuitous organisms. For instance, multicellular protists, ancient eukaryotes, exercise not take 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 exist detected through histology, the microscopic study of tissue appearance, system, and role.

The Four Types of Tissues

Epithelial tissue, too referred to as epithelium, refers to the sheets of cells that encompass exterior surfaces of the body, line internal cavities and passageways, and form sure glands. Connective tissue, as its name implies, binds the cells and organs of the body together and functions in the protection, back up, and integration of all parts of the trunk. Muscle tissue is excitable, responding to stimulation and contracting to provide movement, and occurs every bit three major types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle in the eye. Nervous tissue is too excitable, allowing the propagation of electrochemical signals in the form of nervus impulses that communicate between unlike regions of the torso (Figure four.2).

The next level of organization is the organ, where several types of tissues come together to class a working unit of measurement. Just as knowing the structure and function of cells helps y'all in your written report of tissues, knowledge of tissues will help you empathize how organs part. The epithelial and connective tissues are discussed in detail in this chapter. Musculus and nervous tissues volition be discussed only briefly in this affiliate.

Figure 4.2 Four Types of Tissue: Trunk The four types of tissues are exemplified in nervous tissue, stratified squamous epithelial tissue, cardiac muscle tissue, and connective tissue. (Micrographs provided past the Regents of University of Michigan Medical School © 2012)

Embryonic Origin of Tissues

The zygote, or fertilized egg, is a unmarried cell formed by the fusion of an egg and sperm. After fertilization the zygote gives rise to rapid mitotic cycles, generating many cells to grade the embryo. The first embryonic cells generated have the ability to differentiate into any blazon of cell in the body and, equally such, are chosen totipotent, pregnant each has the chapters to divide, differentiate, and develop into a new organism. As cell proliferation progresses, three major cell lineages are established within the embryo. As explained in a later chapter, each of these lineages of embryonic cells forms the distinct germ layers from which all the tissues and organs of the human body somewhen form. Each germ layer is identified by its relative position: ectoderm (ecto- = "outer"), mesoderm (meso- = "middle"), and endoderm (endo- = "inner"). Figure 4.3 shows the types of tissues and organs associated with the each of the three germ layers. Note that epithelial tissue originates in all iii layers, whereas nervous tissue derives primarily from the ectoderm and musculus tissue from mesoderm.

Figure 4.3 Embryonic Origin of Tissues and Major Organs

Interactive Link

View this slideshow to larn more virtually stalk cells. How practise somatic stem cells differ from embryonic stalk cells?

Tissue Membranes

A tissue membrane is a thin layer or sheet of cells that covers the outside of the body (for case, skin), the organs (for example, pericardium), internal passageways that lead to the outside of the body (for example, mucosa of tum), and the lining of the moveable joint cavities. There are two basic types of tissue membranes: connective tissue and epithelial membranes (Figure four.four).

Effigy 4.4 Tissue Membranes 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 the cutaneous membrane, in other words, the skin.

Connective Tissue Membranes

The connective tissue membrane is formed solely from connective tissue. These membranes encapsulate organs, such equally the kidneys, and line our movable joints. A synovial membrane is a type of connective tissue membrane that lines the cavity of a freely movable joint. For example, synovial membranes environs the joints of the shoulder, elbow, and knee joint. Fibroblasts in the inner layer of the synovial membrane release hyaluronan into the joint crenel. The hyaluronan effectively traps available water to form the synovial fluid, a natural lubricant that enables the bones of a joint to motion freely confronting ane another without much friction. This synovial fluid readily exchanges water and nutrients with blood, as do all body fluids.

Epithelial Membranes

The epithelial membrane is composed of epithelium attached to a layer of connective tissue, for instance, your skin. The mucous membrane is also a composite of connective and epithelial tissues. Sometimes called mucosae, these epithelial membranes line the body cavities and hollow passageways that open up to the external environs, and include the digestive, respiratory, excretory, and reproductive tracts. Mucus, produced past the epithelial exocrine glands, covers the epithelial layer. The underlying connective tissue, called the lamina propria (literally "ain layer"), aid support the frail epithelial layer.

A serous membrane is an epithelial membrane composed of mesodermally derived epithelium called the mesothelium that is supported by connective tissue. These membranes line the coelomic cavities of the body, that is, those cavities that do not open to the outside, and they cover the organs located inside those cavities. They are essentially membranous bags, with mesothelium lining the within and connective tissue on the outside. Serous fluid secreted past the cells of the sparse squamous mesothelium lubricates the membrane and reduces abrasion and friction betwixt organs. Serous membranes are identified according locations. 3 serous membranes line the thoracic cavity; the two pleura that cover the lungs and the pericardium that covers the middle. A quaternary, the peritoneum, is the serous membrane in the abdominal cavity that covers abdominal organs and forms double sheets of mesenteries that append many of the digestive organs.

The skin is an epithelial membrane also called the cutaneous membrane. Information technology is a stratified squamous epithelial membrane resting on pinnacle of connective tissue. The apical surface of this membrane is exposed to the external environment and is covered with dead, keratinized cells that assistance protect the body from desiccation and pathogens.

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Source: https://openstax.org/books/anatomy-and-physiology-2e/pages/4-1-types-of-tissues

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