Types of Tissues

Section 6 Types of Tissue OBJECTIVES: Upon completing this section, you will be able to: 1. Define the word histology. 2. Name and briefly describe the four basic types of tissue. 3. Name the three subtypes of simple epithelial tissue. 4. List the five main subtypes of connective tissue. 5. Name the three subtypes of muscle tissue. 6. Name the two types of nerve tissue. 68 Section 6 Types of Tissue HISTOLOGY Histology is the microscopic study of cells, tissues, and organs. Also called microscope anatomy, histology has two basic classes: 1) normal histology— the study of normal tissues, and 2) pathologic histology—the study of diseased tissue.

Malignancies are diagnosed according to the pattern of cellular growth and deviations of individual cells from their normal forms. Nurses involved with the treatment of malignancies must possess a knowledge of histology in order to understand the anatomy and classification of tumors. In this section, we will review the four basic types of tissue, their functions and locations, and the terms used to describe these tissues—terms such as squamous, stratified, cuboidal, columnar, and others.

We are interested in the types of normal body tissue for two reasons: 1) cancers are named according to the cells and tissues from which they arise, and you should be familiar with these names, and 2) different histologic types of cancers have different responses to chemotherapy and radiotherapy. Basic Types of Tissue There are four basic types of tissue: 1) epithelial tissue, 2) connective tissue (blood, bone, cartilage) muscle tissue, and 4) nerve tissue. The primary tissues are divided into subtypes, which we will discuss shortly.

Each tissue type is designed to perform a specific function. For instance, nerve tissue conducts nerve impulses, muscle tissues are contractile, and epithelial tissues cover body parts. Tissues differ in several ways: 1) according to the size, shape, and arrangement of their cells; 2) according to the kind or intercellular substance; and 3) according to location and function. tissue are the skin and the mucosa and serosa that line the body cavities and internal organs, such as intestines, urinary bladder, uterus, etc.

In some cases, epithelial tissue extends into deeper tissue layers to form glands, such as mucus-secreting glands. The term carcinoma is reserved for malignant growth arising from epithelial cells. Epithelial cells are tightly packed together in sheets and have very little intercellular material between them. Securing the epithelium to the underlying connective tissue is a membrane called the basement membrane. Since epithelial tissue has no blood vessels, it receives nourishment from nutrients that diffuse from blood vessels in the underlying connective tissue.

Dead and injured epithelial cells are constantly being replaced by new cells. Epithelial tissue always has a free surface exposed to the outside (eg, skin) or to an open space internally (eg, the uterus). Epithelial tissue is concerned with protection, secretion, absorption, and filtration. For example, the surface layer of the skin, the epidermis, has tightly packed epithelial cells and protects the body from the elements; epithelial cells in glands secrete various liquids; epithelial cells in the small intestine absorb nutrients into the bloodstream, and so on.

Epithelial tissue may be a single layer thick or several cell layers thick, as shown in Figure 15. The cell layers are arranged in thin sheets, called membranes, that are firmly attached to the underlying connective tissue by a permeable basement membrane. Epithelial tissue is classified into subtypes, according to the shape, arrangement, and function of cells. For instance, an epithelial membrane composed of single layers of cell is called simple; those several cell layers thick are called stratified.

Thin, flat epithelial cells are called squamous (platelike); cube-like cells are called cuboidal; and tall, column-like cells are called columnar. EPITHELIAL TISSUE Epithelial tissue covers or lines all body surfaces inside and outside the body. Examples of epithelial 69 These cell types are explained in more detail below. ¦ ¦ Simple squamous epithelium is composed of a single layer of thin, flattened cells closely fitted together. lt is found on the surface of the skin (where it is called epidermis ). Some substances easily pass through simple squamous epithelia.

Simple cuboidal epithelium is composed of a single layer of lightly packed cube-shaped cells. It covers the ovaries, lines a portion of the kidney tubules, and lines the ducts of such glands and organs as the thyroid gland, salivary glands, liver, and pancreas. ¦ ¦ Simple columnar epithelium is composed of tall, slender cells. These elongated cells are found lining the intestine, the gallbladder, the Fallopian tubes, and some of the respiratory passages. Scattered among the columnar cells are cells called goblet cells, which secrete mucus onto the surface of the tissue.

Pseudostratified columnar epithelium is so named because it seems to be arranged in several layers, when in reality it is but a single layer thick. As shown in Figure 15, all cells adhere to a basement membrane, but not all of them reach the surface, thus accounting for the “false” Figure 15. Types of epithelial cells. Simple squamous Simple cuboidal Goblet cell Simple columnar Stratified squamous Cilia Goblet cell Basement membrane Pseudostratified Glandular 70 ¦ ¦ ¦ ¦ ¦ appearance. This tissue lines most of the respiratory passages (eg, the trachea, the bronchi, and the nasal cavity), and contains both ciliated cells and goblet cells.

Ciliated cells have microscopic hair-like structures extending from the free surface; constantly moving, the hairs sweep debrisladen mucus toward the throat. Goblet cells secrete mucus. Stratified epithelium consists of many layers of cells, but only the surface layer of cells is flat. It is named according to the shape of the cells in the surface layer. Among the various types of stratified epithelium are: Stratified squamous keratinized epithelium consists of flattened, dead, dry cells, composing the epidermis of the skin. Keratin is a protein found in fingernails and toenails, hair, and the epidermis.

Keratinization is the process whereby cells form keratin. Stratified squamous nonkeratinized epithelium is composed of living cells lining the mouth, esophagus, vagina, and anal canal. Transitional epithelium consists of flexible, pliable cells that are capable of stretching and then resuming their original shape. Transitional cells are found in the urinary bladder and other structures subject to periodic distention. Glandular epithelium is found in glands. Examples are sweat and mucus-secreting glands. of intercellular material and fewer cells.

Another difference between epithelial and connective tissue is that while the former is avascular, the latter usually is well supplied with blood vessels. As shown in Figure 16 and outlined below, there are five subtypes of connective tissue. 1. Embryonal connective tissue is found in the embryo and fetus. 2. Vascular tissue, blood and lymph, is connective tissue in which the intercellular material is plasma for blood and an ultrafiltrate of plasma for lymph. The lining of the blood and lymph vessels is called endothelium, and the lining of body cavities is called mesothelium. . Connective tissue proper consists of several types, ranging from tough fibers to soft, gelatinous material. 4. Cartilage is characterized by intercellular material that has a rubbery substance. 5. Bone is a hard matrix due to the presence of lime salts. Connective tissue performs several different functions, ranging from connecting, supporting, and protecting other tissue to helping protect the body against disease. For example, bone serves as the main support system of the body, while tendons, ligaments, and fascia connect other tissues of the body.

Blood transports oxygen, nutrients, and waste products, and helps to fight bacterial infection. Important connective tissue is listed in Table 13, and various connective tissue tumors are listed in Table 14. A point about terminology: malignant tumors of connective tissue (and muscle) are known as sarcomas. There are, however, two exceptions. Cancers affecting the lymph nodes are called lymphomas, and cancers involving the white blood cells are called leukemias. Tumors of epithelial origin are listed in Table 12. Remember that malignant tumors of epithelial origin are called carcinomas. CONNECTIVE TISSUE

Connective tissue, the most abundant and most widely distributed of all tissues, is found throughout the body. It consists of three elements: cells, ground substances (also called matrix or intercellular material), and fibers. In contrast to epithelial tissue, connective tissue consists of large amounts 71 Table 12. Tumors of Epithelial Tissue Tissue of Origin Benign Tumor Malignant Tumor Stratified squamous Basal cells of skin or adnexa Skin adnexal glands: Sweat glands Sebaceous glands Epithelium lining: Glands or ducts— Well-differentiated group Squamous cell papilloma Squamous cell or epidermoid carcinoma Basal cell carcinoma

Sweat gland adenoma Sebaceous gland adenoma Adenoma Papilloma Papillary adenoma Cystadenoma Sweat gland carcinoma Sebaceous gland carcinoma Adenocarcinoma Papillary carcinoma Papillary adenocarcinoma Cystadenocarcinoma Medullary carcinoma Undifferentiated carcinoma (simplex) Bronchogenic carcinoma Bronchial “adenoma” Poorly differentiated group Respiratory tract Neuroectoderm Renal epithelium Liver cells Bile duct Urinary tract epithelium (transitional) Placental epithelium Testicular epithelium (germ cells) Nevus Renal tubular adenoma Liver cell adenoma Bile duct adenoma Transitional cell papilloma

Melanoma Renal cell carcinoma (hypernephroma) Hepatocellular carcinoma Bile duct carcinoma (cholangiocarcinoma) Papillary carcinoma Transitional cell carcinoma Squamous cell carcinoma Choriocarcinoma Seminoma Embryonal carcinoma Hydatidiform mole Source: Robbins SL, Cotran AS, Kumar V: Pathologic Basis of Disease. 3rd ed. Philadelphia, PA: WB Saunders Co; 1984:217. Reprinted with permission. 72 Figure 16. Types of connective tissue. Example Tissue Type A. Embryonal connective tissue. Found in the embryo and fetus. Red blood cell Platelets White blood cell Intercellular material White fiber Fibroblast Yellow fiber

B. Vascular tissue … blood and lymph. C. Connective tissue proper. Several types. Example is loose connective tissue that binds skin to underlying organs. Fills spaces between muscles. Lies beneath epithelium. Contains blood vessels that supply epithelium with nourishment. Cartilage cell White fibers D. Cartilage. Examples are hyaline, elastic, and fibrocartilage, the last illustrated here. Fibrocartilage is a tough tissue that acts as a shock absorber between bones, such as the vertebrae. E. Bone or osseous tissue, the most rigid of connective tissue.

Haversian canal Canaliculi Lacuna 73 Table 13. Important Connective Tissue Type of Connective Tissue Location Function 1. Embryonal Under skin, and along developing bones Blood Forms all other types of connective tissue Transportation; fights infections 2. Blood (vascular) 3. Connective tissue proper a. Loose or areolar b. Adipose (fat) Between other tissues Between organs Superficial fascia Subcutaneous layer of skin, mucous membranes, blood vessels, nerves, body organs Tendons, ligaments, aponeuroses (ie, end of muscle where it becomes tendon), deep fascia, scars, etc. n structures that are extensible and elastic: vocal cords, walls of arteries, trachea, lungs, bronchial tubes, between vertebrae Liver, spleen, lymph nodes, thymus, tonsils, bone marrow, various other structures Supporting and cementing parts of body together Protection, insulation, support c. Collagenous Gives flexible but strong support Furnishes elasticity, thus allowing stretching of structures Protection and supporting framework d. Dense elastic e. Reticular 4. Cartilage a. Hyaline (also called gristle) b. Fibrocartilage c.

Elastic Part of nasal septum; covers surfaces that move against one another; ends of long bones, ribs, larynx, trachea, etc. Discs between vertebrae; symphysis pubis (in pelvis) Epiglottis, larynx, external ear Furnishes firm but flexible support Support and fusion Support and shape 74 Table 14. Tumors of Connective Tissue Tissue of Origin Benign Tumor Malignant Tumor Fibrous tissue Myxomatous tissue Fatty tissue Cartilage Bone Notochordal tissue Blood vessels Fibroma Myxoma Lipoma Chondroma Bone osteoma Fibrosarcoma Myxosarcoma Liposarcoma Chondrosarcoma Osteogenic sarcoma Ewing’s tumor Chordoma (chordosarcoma)

Hemangioma Hemangioendothelioma Angiosarcoma Endotheliosarcoma (multiple sarcoma, Kaposi’s sarcoma) Lymphangiosarcoma Lymphangioendotheliosarcoma Synovioma (synoviosarcoma) Mesothelioma (mesotheliosarcoma) Lymph vessels Synovia Mesothelium (Iining of body cavities) Brain coverings Glomus Hematopoietic cells Lymphoid tissue Lymphangioma Lymphangioendothelioma Meningioma Glomus tumor (glomangioma) Granulocytic leukemia Monocytic leukemia Malignant lymphomas Lymphocytic leukemia Plasmacytoma (multiple myeloma) Hodgkin’s disease 75 MUSCLE TISSUE

The third major type of tissue with which you should be familiar is muscle tissue. Muscle tissue accounts for nearly one-half of the total body weight and consists of three distinct subtypes: striated (skeletal) muscle, smooth (visceral) muscle, and cardiac muscle (Figure 17). Each type of muscle cell is designed to perform one basic function. Striated muscle is attached to bones that move the skeleton. Smooth muscle is located in the walls of hollow internal structures, such as the intestines and blood vessels, allowing such organs to expand and contract.

Cardiac muscle occurs only in the heart, where it forms the walls and enables the heart to pump blood. When viewed under the light microscope, striated muscle cells appear long and thread-like with alternating light and dark cross strips called striations. In contrast, smooth muscle has no striations, Cardiac muscle cells, each of which has a nucleus, are slightly striated. Each cardiac muscle cell tends to divide into a “y” or “x” shape, so that it has more than two ends and joins more than two other cells, ie, it intercalates. The ends of one cardiac Figure 17.

Types of muscle tissue. Intercalated disks Cardiac muscle Isolated smooth cells Striations 76 muscle cell are separated from adjoining cells by a band called an intercalated disk. Unlike skeletal muscle, smooth muscle and cardiac muscle are controlled involuntarily, ie, an individual cannot stop or start the muscle action. Tumors of muscle tissue are listed in Table 15. Nerve tissue is composed at two subtypes of tissue: 1. Specialized cells called neurons (nerve cells) receive stimuli and conduct impulses to and from all parts of the body (Figure 18). 2. Neuroglial or glial cells.

Unlike bone, which is rigid, nerve tissue has a wet noodle-like compactness, and therefore must be supported by connective tissue. Some glial cells support neurons in the brain and spinal cord by entwining around them, while others bind neurons to other connective tissue. NERVE TISSUE The fourth primary type of tissue is nerve tissue. Nerve tissue is found in the brain, spinal cord, and accompanying nerves. The function of the nerve tissue is to move and coordinate bodily functions. Table 15. Tumors of Muscle Tissue Tissue of Origin Benign Tumor Malignant Tumor Smooth muscle Striated muscle Leiomyoma Rhabdomyoma

Leiomyosarcoma Rhabdomyosarcoma Figure 18. Nerve tissue. A neuron showing the three main parts: 1) dendrites, 2) cell body, and 3) axon. 1) Dendrites Telodendria 2) Cell body Golgi apparatus 3) Axon 77 Among the several varieties of glial cells are astrocytes, oligodendrocytes, microglia, and ependymal cells. Tumors of the nervous system are named according to where they arise. For example, cancers arising from astrocytic cells of the brain are called astrocytomas; those arising from oligodendrocytes are called oligodendrogliomas; and those arising from ependymal cells are called ependymomas.

Both the brain and spinal cord are covered by three thin layers of tissue called meninges: the dura mater (external layer); the arachnoid (middle layer); and the pia mater (internal layer). The major type of brain-surface tumor is the meningioma, socalled because it arises from the meninges. Because the spinal cord contains the same basic nerve cell types as the brain, it develops the same kinds of tumors. Table 16 lists the various types of tumors occurring in nerve tissue. Epithelial tissue covers the external and internal surfaces of the body.

Its functions are protection, secretion, absorption, and filtration. The three subtypes of epithelial tissue are: 1) cuboidal, 2) squamous, 3) columnar. Connective tissue is found throughout the body. Its functions range from connecting, supporting, and protecting other tissues to fighting disease. The five subtypes of connective tissue are: 1) embryonal, 2) connective tissue proper, 3) blood and lymph, 4) cartilage, 5) bone. Muscle tissue functions to move and support body parts; it also forms the walls of the heart and blood vessels, in which it functions to move blood throughout the body.

The three subtypes of muscle tissue are: 1) striated (skeletal) muscle, 2) smooth (visceral) muscle, and 3) cardiac muscle. Nerve tissue is composed of specialized cells called nerve cells or neurons and glial or neuroglial cells. Neurons receive stimuli and conduct impulses to and from all parts of the body. The neuroglial or glial cells, which have a glue-like consistency, bind and support neurons. Selected Bibliography Robbins SL, Cotran RS, Kumar V: Pathologic Basis of Disease. 4th ed. Philadelphia, PA: WB Saunders Co; 1989. SUMMARY Histology is the microscopic study of the structure and function of cells, tissues, and organs.

The four basic types of tissues are: 1) epithelial tissue, 2) connective tissue, 3) muscle tissue, and 4) nerve tissue. Table 16. Tumors of Nerve Tissue Tissue of Origin Benign Tumor Malignant Tumor Glial tissue Meninges Peripheral nerve cells Retina Adrenal medulla Nerve sheath Pheochromocytoma Neurilemoma (schwannoma) Neurofibroma Meningioma Neuroma Ganglioneuroma Glioma Meningeal sarcoma Neuroblastoma Retinoblastoma Pheochromocytoma Anaplastic neurilemoma (schwannoma) Anaplastic neurofibroma (neurogenic sarcoma) 78 Section 6 EVALUATION FRAMES 1. Define the word histology. 6. Solid tumors of connective tissue are called: . Name and briefly describe the four basic types of tissue. a) 7. Connective tissue tumors involving the blood are called: 8. Connective tissue tumors involving the lymphoid tissue are called: 9. Name the three subtypes of muscle tissue. b) a) b) c) c) 10. A malignant tumor of smooth muscle origin is called: 11. A malignant tumor originating in striated muscle tissue is called: 12. An example of a malignant tumor of nerve cell origin is a , which develops in the glial tissue. d) 3. Name the three subtypes of simple epithelial tissue. a) b) c) 4. Malignant tumors of epithelial origin are called: 5.

List the five main subtypes of connective tissue. a) b) c) d) e) 79 Section 6 ANSWERS 1. Histology is the microscopic study of cells, tissues, and organs. 2. a) Epithelial tissues cover the external and internal surfaces of the body, and are concerned with protection, secretion, absorption, and filtration. b) Connective tissues are found throughout the body and function to protect, support, and connect other tissues, as well as to help protect the body against disease. c) Muscle tissue performs important functions of support, movement, and protection of body parts; it also propels blood throughout the body. ) Nerve tissue is composed of two types of specialized cells: neurons and neuroglial (glial) cells. Neurons receive stimuli and conduct impulses to and from all body parts. Glial cells function to support and bind neurons. 3. a) cuboidal b) squamous c) columnar 4. carcinomas 5. a) embryonal b) connective tissue proper c) vascular (blood and lymph) d) cartilage e) bone 6. sarcomas 7. leukemias 8. lymphomas 9. a) striated (skeletal) muscle b) smooth (visceral) muscle c) cardiac muscle 10. leiomyosarcoma 11. rhabdomyosarcoma 12. glioma If you completely understood the preceding material, proceed to Section 7.

Otherwise, continue with the reinforcement frames on the next page. 80 REINFORCEMENT FRAMES 6. 1 Section 6 discusses the various types of tissues. The word histology is derived from two Greek forms: histo (web) and ology, meaning “the study of. ” The study of microscopic structures of cells, tissues, and organs is called ……………………………… histology 6. 2 Microscopic anatomy is another name for ………………………………. A medical doctor specially trained in the study of histology is a histologist. A pathologist is an expert in the field of disease or pathology.

One specially trained to recognize and identify abnormal cell growth patterns and deviations in tissues is called a ………………………………….. histology histopathologist 6. 3 The science of histology involves the study of four basic types of tissue: 1) epithelial tissue, 2) connective tissue, 3) muscle tissue, and 4) nerve tissue. Epi is a Greek preposition meaning “upon. ” The type of tissue covering the external and internal surfaces of the body that is concerned with protection, secretion, absorption, and filtration is called ……………….. issue. epithelial 6. 4 There are (three/four/five) …………………………. subtypes of simple epithelial tissue three 6. 5 The three subtypes of epithelial tissue are …………………. , ………………….. , …………………… cuboidal squamous columnar 6. 6 A second type of tissue found in the body is connective tissue. The five subtypes of connective tissue are 1) embryonal, 2) connective tissue proper, 3) blood and lymph, 4) cartilage, and 5) bone.

From the above and with some careful thought, we can determine that three functions of solid types of………………….. tissue are to connect, support, and protect other tissues. connective 6. 7 The two liquid forms of connective tissue are ……………………. and …………………. Blood transports oxygen, nutrients, and waste products and helps to fight bacterial infection. Lymph returns waste products to the blood for elimination from the body and also filters out debris. blood lymph 6. 8 The third type of body tissue that we discussed in Section 6 was muscle tissue.

Muscle tissue makes up about one-half of the total body weight and performs important support and protection functions, as well as providing the mechanism for the ………………… of body parts. movement 6. 9 The fourth type of tissue studied is composed of two specialized types of cells. One type receives stimuli and conducts impulses to and from all parts of the body. These cells are called …………………………………… neurons (nerve cells) 6. 10 The second type of cell serves to bind neurons to surrounding tissues. These cells are called …………… and …………. cells. glial neuroglial 81