Chapter 4 A&P 1 section A

Tissue

a group of similar cells that usually have a similar embryological origin and are specialized for a particular function

Pathologists

physicians who specialize in laboratory studies of cells and tissues

The science that deals with the study of tissues is called

histology

The 4 tissue types

epithelial, connective, muscular, nervous

Epithelial tissue functions:

1. Covers body surfaces

2. line hollow organs, body cavities, ducts

3. forms glands

Connective tissue functions:

1. protects and supports the body and its organs

2. binds organs together

3. stores energy reserves as fat

4. provides immunity

Muscular tissue function:

1. Responsible for movement and generation of force

Nervous tissue function:

1. initiates and transmits action potentials (nerve impulses) that help coordinate body activities

Cell junctions

points of contact between adjacent plasma membranes

Cell junctions may serve one of three functions:

1. form fluid-tight seals between cells

2. anchor cells together or to extracellular material

3. act as channels, which allow ions and molecules to pass from cell to cell within a tissue

The five most important kind of cell junction:

1. Tight junctions

2. adhere junction

3. Desmosomes

4. Hemidesmosmes

5. Gap junctions

Tight junctions

• Form fluid-tight sells between cell

• common among epithelial cells that line the stomach, intestines, urinary bladder

Adherens junctions

• made of plaque

• anchor cells together

Desmosomes

• Composed of plaque linked by transmembrane glycoproteins

• these extend across a gap between adjacent cell membrane

• link the cytoskeleton of cells together

Hemidesmosome

• Connect cells to extracellular material such as the basement membrane

Gap junctions

Allow cells in a tissue to rapidly communicate through connexins

Connexins

transmembrane protein channels that connect cells together

Structure of epithelia tissue:

many cells tightly packed together and little to no extracellular matrix

Structure of connective tissue:

few scattered cells surrounded by large amounts of extracellular fluid

Epithelial tissue has no blood vessels (T or F)

True

Connective tissue have significant networks of blood vessels (T or F)

True

Epithelial tissues almost always form surface layers and are not covered by another tissue (T or F)

True

Simple

one layer

stratified

several layers

pseudostratified

one layer that appears a several

Squamous

flat

cuboidal

cube-like

columnar

rectangular

transitional

variable

What are the cell shapes of epithelial tissue?

1. squamous- flat

2. cuboidal- cube like

3. columnar- rectangular

4. transitional- (variable)

Simple squamous epithelium

1. consist of a single layer of flat, scale like cells

2. it is adapted for for diffusion and filtration and is found in lungs and kidneys

3. it is found in parts of the body that are subjected to little wear and tear

Endothelium

lines the heart and blood vessels

mesothelium

lines the thoracic and abdominopelvic cavities and covers the organs within in them

Simple cuboidal epithelium

consists of a simple layer of cube-shaped cells and performs the functions of secretion and absorption

Simple columnar epithelium

consists of a single layer of rectangular cells and can exist in two forms: nonciliated simple columnar epithelium and ciliated simple columnar epithelium.

Nonciliated simple columnar epithelium

contains microvilli to increase surface area and the rate of absorption and goblet cells that secrete mucus

Ciliated simple columnar epithelium

contains cells with cilia, motile, hair-like processes that help to move fluids or particles along a surface.

Pseudostratified epithelium

1. has only one layer but gives the appearance of many

2. All cells are attached to the basement membrane but some do not reach the apical surface.

pseudostratified ciliated columnar epithelium

the cells that reach the surface either secrete mucus (goblet cells) or bear cilia that sweep away mucus and trapped foreign particles.

Pseudostratified nonciliated columnar epithelium

contains no cilia or goblet cells.

Stratified squamous epithelium

consists of several layers of cells in which the top layer of cells is flat and the deeper layers of cells vary in shape from cuboidal to columnar

Nonkeratinized stratified squamous epithelium

does not contain keratin and remains moist

Stratified cuboidal epithelium

a rare tissue consisting of two or more layers of cube-shaped cells whose function is mainly protective

Stratified columnar epithelium

consists of several layers of cells of which only the top layer is columnar. It is somewhat rare and functions in protection and secretion.

Transitional epithelium

consists of several layers of cells whose appearance is variable

1. it is capable of stretching and thus permits distention of an organ.

2. It lines the urinary bladder and portions of the ureters and the urethra

Glandular Epithelium

are ductless; their secretory products (hormones) enter the extracellular fluid and diffuse into the blood

Exocrine Glands

(sweat, oil, and digestive glands) secrete their products into ducts that empty at the surface of covering and lining epithelium or directly onto a free surface

Unicellular glands

single cells such as the goblet cell

Multicellular glands

composed of many cells that form a distinctive microscopic structure or macroscopic organ

Example of multicellular glands:

Sweat glands (sudoriferous) ,Oil glands (sebaceous) ,Salivary glands

Types of multicellular glands

tubular glands, acinar glands, tubuloacinar glands, simple glands, and

compound glands.

Merocrine

form the secretory products and discharge it by exocytosis

Apocrine

accumulate their secretary product at the apical surface of the secreting cell; that portion then pinches off from the rest of the cell to form the secretion with the remaining part of the cell repairing itself and repeating the process

Holocrine

accumulate the secretory product in the cytosol; when the cell dies, it and its products are discharged as the glandular secretion, with the discharged cell being replaced by a new one