Chapter 3 Body Tissues Tissues Groups of cells

Chapter 3 Body Tissues • Tissues – Groups of cells with similar structure and function – Four primary types: 1. 2. 3. 4. Epithelial tissue (epithelium) Connective tissue Muscle tissue Nervous tissue © 2015 Pearson Education, Inc.

Epithelial Tissues • Locations: – Body coverings – Body linings – Glandular tissue •

Epithelium Characteristics • Cells fit closely together and often form sheets • The apical surface is the free surface of the tissue – The unattached surface • Can be exposed to exterior or cavity of an organ • The lower surface of the epithelium (the basal lamina) rests on a basement membrane – Consists of reticular connective tissue © 2015 Pearson Education, Inc.

Epithelium Characteristics • Avascular (no blood supply) – Relies on circulatory system to obtain food and oxygen • Surrounding connective tissues supply via diffusion from nearby capillaries • Regenerate easily if well nourished (through normal cell division) – Those on the exterior of the skin are exposed to friction and other hostile substances and are therefore lost

Classification of Epithelia • Two name system: – First name = # of layers – Second name = shape of cells • Names using number of cell layers include: – Simple—one layer – Stratified—more than one layer © 2015 Pearson Education, Inc.

Figure 3. 17 a Classification and functions of epithelia. Basal surface Apical surface Simple Apical surface Basal surface Stratified (a) Classification based on number of cell layers

Classification of Epithelia • Names using shape of cells – Squamous • Flattened, like

Figure 3. 17 b Classification and functions of epithelia. Squamous Cuboidal Columnar (b) Classification based on cell shape

Figure 3. 17 c Classification and functions of epithelia. Number of layers One layer: simple epithelial tissues More than one layer: stratified epithelial tissues Squamous Diffusion and filtration Secretion in serous membranes Protection Cuboidal Secretion and absorption; ciliated types propel mucus or reproductive cells Protection; these tissue types are rare in humans Cell shape Columnar Transitional Protection; stretching to accommodate distension of urinary structures (c) Function of epithelial tissue related to tissue type • Remember these general characteristics and you will be able to classify each type a lot easier !!

Simple Epithelia • Simple squamous – Single layer of flat cells – Location—usually forms membranes • Lines air sacs of the lungs • Forms walls of capillaries • Forms serous membranes (serosae) that line and cover organs in ventral cavity – Functions in diffusion, filtration, or secretion in membranes © 2015 Pearson Education, Inc.

Figure 3. 18 a Types of epithelia and their common locations in the body. Air sacs of lungs Nucleus of squamous epithelial cell Basement membrane (a) Diagram: Simple squamous Nuclei of squamous epithelial cells Photomicrograph: Simple squamous epithelium forming part of the alveolar (air sac) walls (275×).

Simple Epithelia • Simple cuboidal – Single layer of cube-like cells – Locations: • Common in glands and their ducts • Forms walls of kidney tubules • Covers the surface of ovaries – Functions in secretion and absorption; ciliated types propel mucus or reproductive cells © 2015 Pearson Education, Inc.

Figure 3. 18 b Types of epithelia and their common locations in the body. Nucleus of simple cuboidal epithelial cell Basement membrane (b) Diagram: Simple cuboidal epithelial cells Basement membrane Connective tissue Photomicrograph: Simple cuboidal epithelium in kidney tubules (250×).

Simple Epithelia • Simple columnar – Single layer of tall cells • Goblet cells secrete mucus – Location: • Lines digestive tract from stomach to anus • Mucous membranes (mucosae) line body cavities opening to the exterior – Functions in secretion and absorption; ciliated types propel mucus or reproductive cells © 2015 Pearson Education, Inc.

Figure 3. 18 c Types of epithelia and their common locations in the body. Nucleus of simple columnar epithelial cell Basement membrane (c) Diagram: Simple columnar Mucus of a goblet cell Simple columnar epithelial cells Basement membrane Photomicrograph: Simple columnar epithelium of the small intestine (575×).

Simple Epithelia • Pseudostratified columnar – All cells rest on a basement membrane – Single layer, but some cells are shorter than others giving a false (pseudo) impression of stratification – Location: • Respiratory tract, where it is ciliated and known as pseudostratified ciliated columnar epithelium – Functions in absorption or secretion © 2015 Pearson Education, Inc.

Figure 3. 18 d Types of epithelia and their common locations in the body. Cilia Pseudostratified epithelial layer Basement membrane Connective tissue (d) Diagram: Pseudostratified (ciliated) columnar Photomicrograph: Pseudostratified ciliated columnar epithelium lining the human trachea (560×).

Stratified Epithelia (two or more cell layers) • Stratified squamous – Named for cells present at the free (apical) surface, which are flattened – Functions as a protective covering where friction is common – Locations—lining of the: • Skin (outer portion) • Mouth • Esophagus © 2015 Pearson Education, Inc.

Figure 3. 18 e Types of epithelia and their common locations in the body. Nuclei Stratified squamous epithelium Basement membrane (e) Diagram: Stratified squamous epithelium Basement membrane Connective Photomicrograph: tissue Stratified squamous epithelium lining of the esophagus (140×).

Stratified Epithelia • Stratified cuboidal—two layers of cuboidal cells; functions in protection • Stratified columnar—surface cells are columnar, and cells underneath vary in size and shape; functions in protection • Stratified cuboidal and columnar – Rare in human body – Found mainly in ducts of large glands © 2015 Pearson Education, Inc.

Stratified Epithelia • Transitional epithelium – Unique type of epithelium because of its ability to become temporarily modified in arrangement and shape – Composed of modified stratified squamous epithelium – Shape of cells depends upon the amount of stretching – Functions in stretching and the ability to return to normal shape – Locations: urinary system organs © 2015 Pearson Education, Inc.

Figure 3. 18 f Types of epithelia and their common locations in the body. Transitional epithelium Basement membrane (f) Diagram: Transitional Basement membrane Transitional epithelium Connective tissue Photomicrograph: Transitional epithelium lining of the bladder, relaxed state (270×); surface rounded cells flatten and elongate when the bladder fills with urine.

Glandular Epithelium • Gland – One or more cells responsible for secreting a particular product – Secretions contain protein molecules in an aqueous (water-based) fluid – Secretion is an active process © 2015 Pearson Education, Inc.

Glandular Epithelium • Two major gland types – Endocrine gland • Ductless; secretions diffuse into blood vessels • All secretions are hormones • Examples include thyroid, adrenals, and pituitary © 2015 Pearson Education, Inc.

Glandular Epithelium • Two major gland types – Exocrine gland • Secretions empty through ducts to the epithelial surface • Include sweat and oil glands, liver, and pancreas • Includes both internal and external glands © 2015 Pearson Education, Inc.