Different Types of Tissues With Pictures

Summary

Tissues are formed by cells and can be differentiated into four different types: connective tissue, muscle tissue, nerve tissue, and epithelium (epithelial tissue). Epithelium is a component of almost every organ in the body. The subtypes and functions of epithelium will be discussed in this article. Connective, muscle, and nerve tissue are addressed in the respective articles. Epithelium covers all inner and outer surfaces of the body (except joint cavities), namely the skin (epidermis) and all mucous membranes. Based on its predominant function, epithelium can be differentiated into protective surface epithelium and secretory glandular epithelium (exocrine glands). Surface epithelium is named and classified according to various criteria (layers, cell shape, surface characteristics). Glandular tissue can be classified according to its location, shape, secretory mechanism, and the type of secretion associated with it (serous or mucinous). The basement membrane anchors the epithelium to connective tissue and creates a diffusion barrier. The basement membrane is composed of a band-like layer of fibers and large proteins and is tightly bound to the cytoskeleton of cells.

For more information about cellular adaptive responses including apoptosis, necrosis, see the article on cellular changes and adaptive responses.

For images on the histology of both normal and abnormal tissues see the articles virtual histology slide box and virtual histopathology slide box.

Overview of the four basic tissue types

There are four basic types of tissues in the body: epithelium, connective tissue, nervous tissue, and muscle tissue.

Connective tissue: There are four subtypes:
- Connective tissue
- Adipose tissue
- Cartilage
- Bone tissue
Nervous tissue:
- Neurons
  - Bipolar neurons (e.g., in the retina)
  - Unipolar (pseudounipolar) neurons (e.g., spine and ganglia)
  - Multipolar neurons (e.g., motor cells)
  - Pyramidal cells (e.g., in the hippocampus)
  - Purkinje cells (e.g., in the cerebellum)
- Neuroglia (neuroglial cells)
  - Astrocytes
  - Oligodendrocytes
  - Schwann cells (produce myelin in the PNS)
  - Microglia
  - Ependymal cells
- Melanocytes (in the skin and retina; produce melanin)
- Odontoblasts (in teeth; produce dentin)
- Chromaffin cells (in the adrenal medulla)
Muscle tissue: Muscle tissue is divided into two types based on structure and distribution.
- Striated muscle
  - Cardiac muscle
  - Skeletal muscle
- Smooth muscle
Epithelium (epithelial tissue)
- Surface epithelium
- Glandular epithelium

Epithelium

Surface epithelium

Layers

Cell shape

Classification of epithelia

Epithelial specialization

Keratinization (horny layer)

Cell projections

Disorders associated with cell projections

Primary ciliary dyskinesia (Kartagener syndrome)
Polycystic kidney disease (PKD)
Retinitis pigmentosa
Dandy-Walker malformation
Polydactyly

Microvilli and stereocilia are comprised of actin filaments, while kinocilia are composed of microtubules!

Prominent stratum corneum of glabrous skin Hepatocyte Stereocilia in the epididymis Cell membrane with motile cilia Respiratory epithelium with goblet cells Spermatozoa Kinocilium

Some surface epithelia possess more than one of the criteria mentioned above or occur especially often in a number of different organs.

Keratinized stratified squamous epithelium

Keratinized stratified squamous epithelium is only found in the epidermis. (see Skin and skin appendage).

Nonkeratinized squamous epithelium

Urothelium (transitional epithelium)

Respiratory epithelium

Prominent stratum corneum of glabrous skin Squamous epithelium and esophageal glands Palatine tonsil Urothelium Mucosa of the ureter Urothelium (transitional epithelium) Respiratory epithelium of the nasal mucosa Respiratory epithelium with goblet cells

Glandular epithelium

Location of glandular tissue

Based on the location of glandular cells in relation to the surface epithelium, glands can be classified as either intraepithelial (located in the surface epithelium) or extraepithelial (located beneath the surface epithelium).

Intraepithelial glands

Respiratory epithelium of the trachea with goblet cells Respiratory epithelium with goblet cells Duodenum Colonic mucosa Goblet cells in the small intestine

Extraepithelial glands

Typical extraepithelial gland structure

Since extraepithelial glands migrate during embryogenesis from the surface epithelium into the underlying connective tissue, they have an elaborate structure composed of excretory ducts and terminal ends. These components are named below in the sequence corresponding to the path of the secretion (from formation to the opening):

Glandular duct with two-layered epithelium

Shapes of the terminal ends of exocrine glands

Classification of exocrine glands (by structure) Microstructure of the exocrine pancreas Pancreatic acini and islets of Langerhans Colonic mucosa Layers of the colonic wall Prostate gland with corpora amylacea

Secretory mechanisms of exocrine glands

Exocrine glands are intraepithelial glands or extraepithelial glands that release their secretions on the inner (e.g., intestinal lumen) or outer (e.g., skin) surfaces of the body.

Secretory mechanisms of exocrine glands Sebaceous gland and the arrector pili muscle

Type of secretion

Depending on the type of secretion, glands can be categorized as serous, mucous, or seromucous.

Normal mucous acinus

Eccrine sweat glands Mammary gland

References:^[1]

Basement membrane

The basal lamina and lamina reticularis form the basement membrane! The basement membrane is usually identified with light microscopy, whereas the basal lamina is identified with electron microscopy!

Structure of basement membrane

Microscopy