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By the end of this section, you will be able to:
  • Identify the four main tissue types
  • Discuss the functions of each tissue type
  • Relate the structure of each tissue type to their function
  • Discuss the embryonic origin of tissue
  • Identify the three major germ layers
  • Identify the main types of tissue membranes

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.

The four types of tissues

Epithelial tissue , also referred to as epithelium, refers to the sheets of cells that cover exterior surfaces of the body, lines internal cavities and passageways, and forms certain glands. Connective tissue , as its name implies, binds the cells and organs of the body 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 provide movement, and occurs as three major types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle in the heart. Nervous tissue is also excitable, allowing the propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body ( [link] ).

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

Four types of tissue: body

This diagram shows the silhouette of a female surrounded by four micrographs of tissue. Each micrograph has arrows pointing to the organs where that tissue is found. The upper left micrograph shows nervous tissue that is whitish with several large, purple, irregularly-shaped neurons embedded throughout. Nervous tissue is found in the brain, spinal cord and nerves. The upper right micrograph shows muscle tissue that is red with elongated cells and prominent, purple nuclei. Cardiac muscle is found in the heart. Smooth muscle is found in muscular internal organs, such as the stomach. Skeletal muscle is found in parts that are moved voluntarily, such as the arms. The lower left micrograph shows epithelial tissue. This tissue is purple with many round, purple cells with dark purple nuclei. Epithelial tissue is found in the lining of GI tract organs and other hollow organs such as the small intestine. Epithelial tissue also composes the outer layer of the skin, known as the epidermis. Finally, the lower right micrograph shows connective tissue, which is composed of very loosely packed purple cells and fibers. There are large open spaces between clumps of cells and fibers. Connective tissue is found in the leg within fat and other soft padding tissue as well as bones and tendons.
The four types of tissues are exemplified in nervous tissue, stratified squamous epithelial tissue, cardiac muscle tissue, and connective tissue in small intestine. Clockwise from nervous tissue, LM × 872, LM × 282, LM × 460, LM × 800. (Micrographs provided by the Regents of University of Michigan Medical School © 2012)

Embryonic origin of tissues

The zygote, or fertilized egg, is a single cell formed by the fusion of an egg and sperm. After fertilization the zygote gives rise to rapid mitotic cycles, generating many cells to form the embryo. The first embryonic cells generated have the ability to differentiate into any type of cell in the body and, as such, are called totipotent    , meaning each has the capacity to divide, differentiate, and develop into a new organism. As cell proliferation progresses, three major cell lineages are established within the embryo. Each of these lineages of embryonic cells forms the distinct germ layers from which all the tissues and organs of the human body eventually form. Each germ layer is identified by its relative position: ectoderm    (ecto- = “outer”), mesoderm    (meso- = “middle”), and endoderm    (endo- = “inner”). [link] shows the types of tissues and organs associated with the each of the three germ layers. Note that epithelial tissue originates in all three layers, whereas nervous tissue derives primarily from the ectoderm and muscle tissue from mesoderm.

Questions & Answers

movement of small intestine
Bage Reply
which hormone is responsible for Gluten enteropathy
Syed
the diagram of the respiratory system
Praise Reply
Describe sinus of brain
MAHESH Reply
name the 5 layers of skin
Monika Reply
stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum
airiz
those are the layers of epidermis,, then we have the dermis which has got two layers that is papillary dermis and reticular dermis.. beneath the dermis we have the hypodermis( subcutaneous layer) which is not considered as a layer of skin
airiz
what's a feedback
ivhil Reply
is the information or comment about something that one have done
Gaston
may be you mean negative or positive feedback mechanism... in general, they mean body response its changes by hormones
Quran
what is endocrin?
Asim Reply
why should there be an inhibition to the process of gastric production in the intestinal phase
Gloria
endocrine is a system through which the secretions of cell directly poured into blood.
Tanveer
why should there be an inhibition to the process of gastric production in the intestinal
Gloria Reply
what is a stimuli
Emily Reply
environment factor that cause a cell to respond
Quran
name the two types of melanin
Laila Reply
deference between RNA and DNA
Ali
.DNA stands for Deoxyribonucleic Acid. The sugar portion of DNA is 2-Deoxyribose.RNA stands for Ribonucleic Acid.  The sugar portion of RNA is Ribose.2.The helix geometry of DNA is of B-Form (A or Z also present).The helix geometry of RNA is of A-Form.3.DNA is a double-stranded molecule consisting o
ryaisha
DNA consists of nucleotide but RNA consists of nucleoside DNA is double standard but RNA is single standard.In DNA at the nitrogen bases adinine,guanine,cytocin and thymine is present but in case of RNA instead of thymine uracil is present.
Tanveer
what are rdna
Budumari
what is a heart
walker Reply
A heart is an organ in the circulatory system that pumps blood throughout the systemic regions
bernard
what is anatomy
Aisha
Anatomy is the study of internal and external structures and the relationship among body parts. (the study of structure).
Tomi
what is the physiology of the heart
nadine
guys help me with a pathophysiology of asthma
Luyando
asthma is a lungs related disorder in which there is difficulty in breathing due to some allergic factors, their is inflamation of alveoli of respiratory part of lungs.also decreases the surface area.
Tanveer
what is meaning of brain strock and its types?
Tanveer
the pathophysiology of asthma is complex and involves airway inflammation and bronchial hyperresponsiveness pathogenesis of asthma
Omkar
skin infection please explain
Hamza Reply
what is malignant melanoma
Akon Reply
cancerous cells 🙄
Sohan
yes benign is non-cancerous malignant is cancerous.
Joseph
that's a simple way of explaining it however you're different processes like mitosis etc a person can be at risk for developing cancer etc
Joseph
you can tell by an unusual growth of a mole, or change in size coloration with melanoma. which is abnormal growth of your squamous cells.
Joseph
Types of wandering connective tissues
Hassan Reply
what are the meaning of skin
PASHALINA Reply
study of external structure of human body is known as anatomy
VINAY Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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