Chapter 3 Tissue and its Parts PDF

***Chapter 3*** ***Tissue & and its Parts*** Tissues are groups of cells that have a similar structure and act together to perform a specific function. The word tissue comes from a form of an old French verb meaning "to weave". The zygote, or fertilized egg, is a single cell formed by the fusion o...

***Chapter 3*** ***Tissue & and its Parts*** Tissues are groups of cells that have a similar structure and act together to perform a specific function. The word tissue comes from a form of an old French verb meaning "to weave". The zygote, or fertilized egg, is a single cell formed by the fusion of an egg and sperm. After fertilization 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. Theepithelial tissueand connective tissues are discussed in detail in this chapter. Muscle and nervous tissues will be discussed only briefly in this chapter. 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. **There are four different types of tissues in animals:** 1. Connective Tissue. 2. Musclcullar Tissue. 3. Nervous Tissue. 4. epithelial tissueTissue. ***Connective Tissue*** As its name suggests, **connective tissue** makes up a connective web inside our body. Holding our body parts together and providing support are the main jobs of this tissue. We would certainly not be in good shape if all of our internal body parts were free-floating. Connective tissue fills in the spaces inside our body with a matrix made of fibers within a liquid, solid, or jelly-like substance. Think of a gelatin salad with fruit suspended inside, and you will have an idea of how certain types of connective tissue function.  **Fig. No. 3.1 *Connective Tissue and its type in different location*** There are three main groups of connective tissues: - **Loose connective tissue**  It holds [organs](https://www.thoughtco.com/organ-systems-373571) in place and attachesepithelial tissuetissue to other underlying - **Dense connective tissue**  It helps attach muscles to bones and link bones together at joints. - **Specialized connective tissue**  It encompasses a number of different tissues with specialized cells and 1. **Loose Connective Tissue** In vertebrates, the most common type of connective tissue is **loose connective tissue**. It holds [organs](https://www.thoughtco.com/organ-systems-373571) in place and attachesepithelial tissuetissue to other underlying tissues. Loose connective tissue is named so because of the \"weave\" and type of its constituent fibers. These fibers form an irregular network with spaces between the fibers. The spaces are filled with ground substance. The three main types of **loose connective fibers** include collagenous, elastic, and reticular fibers. Fig. No. 3.2 **This image of loose connective tissue shows collagenous fibers (red), elastic fibers (black), matrix, and fibroblasts (cells that produce the fibers). ** - **Collagenous fibers**  They are made of collagen and consist of bundles of fibrils that are coils - **Elastic fibers**  They are made of the protein elastic and are stretchable. They help to give connective - **Reticular fibers ** join connective tissues to other tissues. Loose connective tissues provide support, flexibility, and strength required to support internal organs and structures such as [blood vessels](https://www.thoughtco.com/blood-vessels-373483), [lymph vessels](https://www.thoughtco.com/lymphatic-vessels-anatomy-373245), and nerves. 2. **Dense Connective Tissue** Another type of connective tissue is dense or fibrous connective tissue, which can be found in tendons and ligaments. These structures help attach muscles to bones and link bones together at joints. Dense connective tissue is composed of large amounts of closely packed collagenous fibers. In comparison to loose connective tissue, dense tissue has a higher proportion of collagenous fibers to ground substance. It is thicker and stronger than loose connective tissue and forms a protective capsule layer around organs such as the [liver](https://www.thoughtco.com/liver-anatomy-and-function-4058938) and [kidneys](https://www.thoughtco.com/kidneys-anatomy-373243).  Fig No. 3.3 **Image of the dermis of the skin shows dense fibrous connective tissue. Irregular collagenous fibers (pink) and fibroblast nuclei (purple)** Dense connective tissue can be categorized into **dense regular**, **dense irregular**, and **elastic** connective tissues. - **Dense regular:**  Tendons and ligaments are examples of dense regular connective tissue. - **Dense irregular:** Much of the dermis layer of the [skin](https://www.thoughtco.com/integumentary-system-373580) is composed of dense irregular connective tissue. - **Elastic:**  These tissues enable stretching in structures such as [arteries](https://www.thoughtco.com/artery-anatomy-373235), vocal cords, the trachea, ***Epithelial tissue Tissue*** **Epithelial tissue tissue** is made up of epithelial tissue cells, which are vastly different from the muscle cells we just talked about. These cells can be flat, cubical, or columnar. They are joined tightly together, making a single or stacked continuous sheet. Like a quilt that is tightly stitched, epithelium makes an excellent protective cover for the body, in the form of skin. Epithelial tissue tissue can also be found lining some internal cavities and organs. There are different types of epithelial tissue tissue depending on their function in a particular location. The simplest classification of these tissues is based on the number of cell layers. - Simple epithelial tissue - Stratified epithelial tissue When the epithelium is composed of a single layer of cells, it is called simple epithelial tissue tissue and those containing two or more layers of cells are called stratified epithelial tissue tissues. One particular type is called *pseudostratified* because a single layer of cells having varying heights gives the appearance of being stratified. Epitheliaal tissuel tissue can also be classified based on the shape of the cells, giving rise to three types: - **Squamousepithelial tissuetissue:** consists of extremely thin cells that resemble the scales of a fish - **Cuboidalepithelial tissuetissue:** contains cells that appear square in cross-section but are marginally longer than they are wide - **Columnarepithelial tissuetissue:** consists of elongated cell involved in absorption of materials The number of cell layers and cell types together give rise to 6 different types ofepithelial tissuetissue. - **Simple squamous epithelial tissue** - **Simple cuboidal epithelial tissue** - **Simple columnar epithelial tissue** - **Stratified squamous epithelial tissue** - **Stratified cuboidal epithelial tissue** - **Stratified columnar epithelial tissue** Additionally, there are pseudo stratified epithelial tissue and transitional epithelial tissue. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- Key facts about the simple epithelium --------------------------------------- ------------------------------------------------------------------------------------------------------------------------------ Function and classes Function: absorption and filtration processes\ Classes: squamous, cuboidal, columnar, pseudostratified Simple squamous Location: blood and lymphatic vessels, air sacs of lungs, lining of the heart\ Function: secrets lubricating substance, allows diffusion and filtration Simple cuboidal Location: secretory ducts of small glands, kidney tubules\ Function: allows secretion and absorbtion Simple columnar Location: bronchi, uterine tubes, uterus - *ciliary columnar*; digestive tract, bladder - *nonciliated columnar* epithelium\ Function: allows absorbtion, secretes mucous and enzymes Pseudo stratified columnar Location: trachea and most of the upper respiratory tract (ciliated cells)\ Function: secretes mucus which is moved with cilia Clinical relations Metaplasia, dysplasia, neoplasia ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. **Simple Epithelium** Simple epitheliaal tissue are made of a single layer of cells that are in direct contact with the basement membrane with a common apical surface. These cells can be squamous, cuboidal, or columnar. [Simple squamous epithelium](https://biologydictionary.net/simple-squamous-epithelium/) is found in the alveoli of lungs, and its structure is important for the exchange of gases between the blood and lungs. Simple cuboidal epithelial tissue line the lumen of collecting ducts in the kidney and are present in the thyroid around the follicles that secrete thyroid hormones. They protect the underlying structures and have a secretory function (such as in the thyroid) or absorptive function (as in the collecting ducts of the kidney). 1. **Simple columnar epithelial tissue** Simple columnar epithelial tissue tissue is found in the female reproductive system and in the digestive tract. The cells in the fallopian tubes are ciliated and involved in the movement of the ovum towards the uterus. Those in the digestive tract are non-ciliated, and instead contain microvilli, which gives the epithelium the appearance of being brush-bordered. 2. **Simple squamous epithelial tissue** Simple squamous epithelia are tissues formed from one layer of squamous cells that line surfaces. Squamous cells are large, thin, and flat and contain a rounded nucleus. Like other epithelial cells, they have polarity and contain a distinct apical surface with specialized membrane proteins. These epithelia are common where absorption or transport of materials is important. They also play a role in [diffusion](https://biologydictionary.net/diffusion/), [osmosis](https://biologydictionary.net/osmosis/) and [filtration](https://biologydictionary.net/filtration/). This makes them important in the kidney, in the alveoli of lungs and in the walls of capillaries. Since this epithelium is made of a single layer of thin cells that are tightly packed together, it is the ideal medium for selective transmembrane transport. Some substances, such as oxygen from the lungs travel mostly along their [concentration gradient](https://biologydictionary.net/concentration-gradient/) towards the [blood](https://biologydictionary.net/blood/). Others are actively transported using membrane-bound carrier proteins. Membrane proteins are involved in forming [tight junctions](https://biologydictionary.net/tight-junctions/) to ensure that the movement of ions, gases, small molecules or water occurs only through the [cell](https://biologydictionary.net/cell/) and there is no diffusion or osmosis through the interstitial spaces. The rest of the [plasma membrane](https://biologydictionary.net/plasma-membrane/) makes up the basolateral surface. **Example Alveoli of the Lung** Epithelial Tissue 3. **Simple Cuboidal Epithelial tissue** Simple cuboidal epithelium consists of a monolayer of epithelial cells that appear to be square-shaped in cross section. With large, rounded, centrally located nuclei, all the cells of this epithelium are directly attached to the basement membrane. Types of Simple Cuboidal Epithelial tissue This epithelium can be classified based on the location and its corresponding function. - Cuboidal epithelium of reproductive organs: cells lining the tubuli recti, rete testis and the [ovary](https://biologydictionary.net/ovary/) - Cuboidal epithelium of the [central nervous system](https://biologydictionary.net/central-nervous-system/): the ependyma - Cuboidal epithelium of the [endocrine system](https://biologydictionary.net/endocrine-system/): the follicular cells of the thyroid - Cuboidal epithelium of the [excretory system](https://biologydictionary.net/excretory-system/): lining the proximal and distal convoluted tubules of a [nephron](https://biologydictionary.net/nephron/) Though these tissues appear histologically similar, in each of these organs, they are specialized for performing certain roles. 2. **Stratified epithelial tissue**  ***Nervous Tissue*** **Nervous tissue** is found within the nervous system and is made up of unique specialized cells. Like electrical circuits, the nervous system transmits signals from nerves to the spinal cord and brain. Cells known as **neurons** conduct these impulses, making it possible for us to use our senses. Image result for nervous tissue ***Fig. No. 1.4 Nervous Tissue*** **1. Which of these is true about simple squamous epithelia?**\ **A.** They are involved in the transport of oxygen and carbon dioxide at the lungs\ **B.** They play a role in the filtration of nitrogenous waste products in the [brain](https://biologydictionary.net/brain/)\ **C.** They are necessary for secretion and transport of hormones\ **D.** All of the above **Answer to Question \#1** **2. Which of these epithelia can stretch to increase the volume of the organ based on internal water pressure?**\ **A.** Simple squamous epithelia\ **B.** Simple columnar epithelia\ **C.** Transitional epithelia\ **D.** Stratified columnar epithelia **Answer to Question \#1** **3. How is a pseudostratified epithelium different from a truly stratified tissue?**\ **A.** The nuclei are at the same level in pseudostratified epithelia.\ **B.** The apical and basal surfaces are aligned.\ **C.** There are multiple cell layers in pseudostratified epithelia.\ **D.** All the cells in a pseudostratified epithelium interact with the basement membrane. **Answer to Question \#2** **4. Which of these is an important function of epithelial cells?**\ **A.** Protection from chemical abrasion\ **B.** Secretion of hormones and enzymes\ **C.** Absorption of nutrients\ **D.** All of the above **Answer to Question \#3**