THE STUDY OF TISSUES

Histology

What are tissues?

Tissues are collections of specialized cells and cell products that perform a limited number of functions.

Four Basic Tissue Types

Epithelial – lining and secretory tissueConnective – supportive and nutritive tissueMuscular – contracts to produce movementNervous – integration and control

Characteristics of Epithelial Tissue

Cellularity– epithelia are composed almost entirely of cells bound closely together by interconnections called cell junctions.

Polarity-epithelial tissue have an exposed surface (apical cells) that either faces the exterior of the body or some internal space and a base (basal cells).

Attachment—the base of the epithelium is bound to a thin basal lamina or basement membrane.

More characteristics of Epithelial Tissue

Avascularity—epithelia are avascular, which means that they lack blood vessels. They have to get their nutrients by diffusion or absorption

Regeneration—epithelial cells that are damaged or lost are continuously replaced by the stem cells in the epithelium

Functions of Epithelial Tissue

Four major functions: Provide physical protection Control permeability Provide sensation (They have a large sensory nerve

supply.) Produce specialized secretions (Glands)

Naming Epithelial Tissue based on shape

Epithelium is named according to shape, structure, and arrangement of cells.

Shapes of Epithelium

•squamous - thin and flat cells

•cuboidal - cube shaped cells

•columnar - column shaped cells

Naming Epithelial Tissue based on layers

simple - single layer of cells

stratified - multilayered cells

pseudostratified - false stratified

ciliated - cells possess cilia

-STRUCTURE, FUNCTION, AND LOCATION OF SEVEN EPI THELIAL T I SSUE TYPES-WHAT EACH T ISSUE TYPE LOOKS L I KE ENOUGH TO BE ABLE TO I DENTI FY THE TYPE FROM A P ICTURE

What do you HAVE to know?

The 7 Epithelial Tissue Types that you have to know are . . .

Simple SquamousSimple CuboidalSimple ColumnarStratified SquamousStratified Cuboidal (sometimes referred to as

Transitional)Pseudostratified Ciliated ColumnarKeratinized (or Cornified) Stratified

Squamous

Simple Squamous Epithelium

Structure-The thinnest tissue of the body. One layer, flattened (squashed) nucleus.

Function-Allows transport across membranes in lungs and capillaries. Secretes fluid in serous membranes (e.g. pericardial and pleural membranes, mesenteries).

Location-Lines cardiovascular system, covers organs, forms glomerular capsules in kidney.

Simple Cuboidal

Structure-single layer, cube-like cells with spherical (round) nuclei.

Function-secretion, absorption

Location-Kidney tubules, small ducts of glands

Simple Columnar

Structure

Function

Location

Stratified Cuboidal (sometimes referred to as “Transitional”)

Structure- many layered (usually 2), cube like cells, spherical (round) nuclei

Function-absorption, secretion

Location- mammary and some sweat glands.

Keratinized Stratified Squamous

Structure- there is a layer of dead cells above the stratified squamous cells (nearest the apical surface).

Function-protection of areas of external, sometimes extreme abrasion

Location- Palms of hands and soles of feet.

Summary of Epithelial Tissue

Look for basement membrane and apical surface (could be a lumen).

Determine how many layers there are between the basement membrane and the free or apical surface.

Simple=one layer, stratified=multiple layers, pseudostratified=looks like stratified, but are all connected to the basement membrane

Look at the shape of the cells nearest the apical surface.

Name the cells according to the shapes.

Name this type

Quiz Time

Name this tissue type

Name this tissue type

Tissue Notes Part 2Muscle and Connective Tissue

Muscle Tissue

Is specialized for contractionProduces all body movement

3 Types of Muscle Tissue

Smooth Muscle: found in walls of hollow, contracting organs (blood

vessels; urinary bladder; respiratory, digestive and reproductive tracts)

Skeletal muscle: body muscles responsible for movement

Cardiac muscle: only in the heart

Skeletal Muscle Cells

Skeletal muscle cells: are long and thin are usually called muscle fibers do not divide new fibers are produced by stem cells (satellite cells)

Skeletal Muscle

Striated, voluntary, and multinucleated

Figure 4–18a

MUSCLE TISSUESKELETAL

Voluntary movement

Long and cylindrical

Transverse striation

Each fiber is multi-nuclear

Smooth Muscle Cells

Smooth muscle cells: are small and tapered can divide and regenerate

Smooth Muscle Tissue

Nonstriated, involuntary, and single nucleus

Figure 4–18c

MUSCLE TISSUE

SMOOTH

Involuntary movement

Predominant

Long, spindle shape

Single nucleus

Internal organs

MUSCLE TISSUECARDIAC

Striations

Involuntary

One nucleus

Deep center

Heart muscle

Cardiac Muscle Cells

Cardiac muscle cells: are called cardiocytes form branching networks connected at intercalated

disks Where they branch is called a bifurcation. are regulated by pacemaker cells

Cardiac Muscle Tissue

Striated, involuntary, and single nucleus

Figure 4–18b

Connective Tissue

Connective Tissue

The essential characteristic that distinguishes connective tissue from the other three tissue types is that it consists of cells separated from each other by an extracellular MATRIX.

Cell types in a Matrix

-blast: create the matrix-cytes: maintain the matrix-clasts: breakdown the matrix

Major Components of the Matrix

Protein fibers Collagen-very strong and flexible but not elastic Reticular-thin and “fillers” of space Elastin-elastic

Ground Substance with non-fibrous proteins and other molecules. Bone Cartilage

Fluid Blood

Classification of Connective Tissue

Fibrous Connective Tissue Loose Connective Tissue

Areolar Dense Connective Tissue

Regular-very strong in one direction (tendons and ligaments)

Irregular-less strength but in many directions (dermis of skin)

Areolar

Structure- has a viscous matrix with an irregular arrangement of fibers

Function-loose packing, support, and nourishment for the surrounding structures

Location-widely distributed throughout the body; fascia, which attaches the skin to underlying tissue

Areolar

Adipose

Structure-Little extracellular material. The adipocytes, or fat cells, are so full of lipid that the cytoplasm is pushed to the periphery of the cell.

Function-Insulation, packing material, energy storage, and protection of organs

Location-mesenteries, subcutanous area (below the skin) and surrounding organs

Adipose

Fibrous (Dense or Collagenous)

Structure-Matrix composed of collagen fibers running in (somewhat) the same direction.

Function-Withstand great pulling forces with great tensile strength and stretch resistance.

Location-Tendons and Ligaments

Tendon (connects muscle to bone—muscle stretches)

Ligament (connects bone to bone—ligament stretches)

Dense Fibrous

Cartilage (Hyaline)

Structure-Collagen fibers are small and evenly dispersed in the matrix. The cartilage cells, or chondrocytes, are found in spaces, or lacunae, within the rigid matrix.

Function-Allows growth of long bones. Provides rigidity with some flexibility.

Location-Growing long bones, costal cartilage of ribs, nasal cartilage, articulating surface of bones.

Cartilage (Hyaline)

Bone (Compact)

Structure-Hard matrix with osteocytes within lacunae that are distributed around the central canal

Function-Provide strength and support. Forms the outer shell of bones

Location-Shafts of long bones, outer shell on all bones

Bone (Compact)

Key to Connective Tissue

Always found in a MATRIX.For American High School Anatomy and

Physiology: A AdiposeA AreolarB BoneC CartilageD/F Dense Fibrous

Nervous Tissue

Neuron (Multipolar)

Structure-axon, cell body and dendrite

Function-conduct impulses, store information, process thought

Location-brain, spinal cord, peripheral nerves

Neuron

General Review

http://www.gwc.maricopa.edu/class/bio201/histoprc/prac1q.htm

http://www.path.uiowa.edu/cgi-bin-pub/vs/vl_browse.cgi?cat=h_epithelium