Chapter 4 Tissues A&P 1

Classification of Epithelial Tissues

Simple: Consists of a singer layer of cells. Each ell extending from basement membrane to the free surface. Stratified: Consist of more than one layer of cells but only the basal layer attaches the deepest layer to the basement membrane. Psuedostratified: Appears to be stratified but is not.

Simple -vs- Compound

Simple: Glands with single ducts. Compound: Glands with ducts that branch out.

Tubular -vs- Acinar (Alveolar):

Tubular: Glands with secretory regions shaped as tubules (small tubes). Acinar (alveolar): Glands shaped like saclike structures. They can be straight or be coiled. Tubuloacinar or Tubuloalveolar: Some glands have combinations of both tubular and acinar.

Exocrine:

Referring to secreting outside of the body.

Extracellular Matrix:

The composition of non-cellular substances surrounding the cell and functions of the cell. Chemical environment secreted by tissue cells.

3 Loose Connective Tissue Types:

1.) Areolar 2.) Adipose 3.) Reticular

Protein Fibers of the Matrix:

1.) Collagen fibers: consist of collage, the most abundant protein in the body (1/4 to 1/3 of total body protein or about 6%). Synthesized within fibroblasts and secreted into the extracellular space. Link together forming long collagen fibrils. Joined together in bundles to make collagen fibers. Very strong and flexible. Specific to certain tissues. Type I is most abundant in body, good for tendons and ligaments. Cartilage is type II and Reticular is type III. 2.) Reticular fibers: very fine collagen fibers, not chemically distinct category of fibers. Short, thin fibers branch to form a network - appear differently microscopically from other collagen fibers. Not as strong as type I. (fills spaces between tissues and organs) 3.) Elastic fibers: Consist of protein elastin. Has ability to return to original shape after stretching or compression. Elastic quality. Fibroblasts secrete polypeptide chains, link to form network, elastin network like a rubber band responding to force an recoils when released.

Embryonic Germ Layers:

1.) Ectoderm - Integument, central nervous system. 2.) Mesoderm - Muscle, bone and blood vessels. 3.) Endoderm - Gut, digestive tract, reproductive.

4 Types of Tissues:

1.) Epithelial 2.) Connective Tissue 3.) Muscle Tissue 4.) Nervous Tissue

Most Common Characteristics of Epithelial Tissue:

1.) Mostly composed of cells. Very little extracellular matrix b/t cells. 2.) Covers body surfaces. Body surfaces and form glands. Exterior surface, lining of digestive system and respiratory tracts, heart, blood vessels and the linings of many body cavities. 3.) Distinct cell surfaces. 4.) Cell and matrix connections. 5.) Nonvascular. Blood vessels do not penetrate the basement membrane to reach the epithelial. All gas and nutrients in blood must reach epithelium by diffusing across the basement membrane. 6.) Capable of regeneration. Retain ability to undergo mitosis and able to replace damaged cells with new epithelial cells. Stem cells divide and produce new cells.

3 Parts to the Extracellular Matrix:

1.) Protein fibers. 2.) Ground substance. 3.) Fluid. Not always, but most cases is water.

3 Types of Epithelium based on idealized shapes of the epithelial cells:

1.) Squamous - cells are flat or scale-like. 2.) Cuboidal - cells are cube-shaped, about as wide as they are tall. 3.) Columnar - column shape. Tend to be taller than they are wide.

Tissues Defined:

A collection of similar cells performing a specific task.

Gap Junctions:

A small specialized contact region between cells containing protein channels that allow intercellular communication allowing ions and small molecules to pass from one cell to another.

Basement Membrane:

A specialized type of extracellular material secreted by epithelial an connective tissues cells. Like Scotch tape, basement membrane helps attach epithelial cells to the underlying tissues. Important role in supporting and guiding cell migration during tissue repair.

Merocrine -vs- Aprocrine -vs- Holocrine (all are exocrine):

All three terms refer to how these glands secrete. Merocrine: most common type of secretion, products released but no actual cellular material is lost. Like water producing sweat glands and exocrine portion of the pancreas. Aprocrine: secretory products are released as fragments of the gland cells, secretory products are retained within the cell and portions of cell are pinched off to become part of the secretions. Like as in mammary glands releasing milk as a combo of merocrine and aprocrine. Holocrine: involves the shedding of the entire cells during secretion. Products accumulate in cytoplasm of each epithelial cell, cell ruptures and dies. Oil glands of the skin do this.

Adhesive Molecules:

Also in ground substance, holds together proteoglycans to structures like plasma membranes. Specific adhesive molecules predominate in certain types of ground substances.

Cell Connections:

Cells have structures that hold them together or to the basement membrane. Do these 3 things: 1.) Mechanically bind cells together. 2.) Help form permeability barrier. 3.) Provide mechanism for intercellular communication.

Epithelial Tissue:

Covers and protects surfaces, both outside and inside the body.

Connective Tissues:

Enclose and separate other tissues (around organs, separate muscles, arteries, veins and nerves from each other) Connects things within the body.

Ground Substance of Matrix:

Fibers will be in and amongst these substances. 2 types of large nonfibrous molecules called hyaluronic acid and proteoglycans.

Proteoglycans:

Formed from proteins and polysaccharides) Main component of cartilage. Traps large quantities of water that cannot be squeezed out, the water makes the cartilage handle being compressed and returning to original shape like a sponge.

Desmosomes/Hemidesmosomes

Glycoproteins secreted attach cells to the basement membrane but are a weak connection! Extra binding between cells: Desmosomes: Disk shaped structures with very adhesive glycoproteins that bind cells to each other in intermediate filaments that extend into cytoplasm of cells. Many found in epithelial tissue that are subjected to stress, like stratified squamous, epidermis of the skin. Hemidesmosomes: Similar to 1/2 a desmosome, attach epithelial cells to the basement membrane.

Functions of Epithelial

Have many functions, including forming barrier between a free surface and the underlying tissues and secreting, transporting and absorbing selected molecules. The structure and organization of cells within each epithelial type reflect these functions.

Tight Junctions:

Hold cells together, form permeability barrier. Formed by plasma membrane adjacent to the cell that join one another in a jigsaw fashion to make a tight seal. Near surface or epidermis of the skin. Prevents materials from passing between. (stomach and urinary bladder chemicals cannot pass b/t cells)

Hyaluronic Acid:

Long chain carbohydrate - is very slippery. Makes good lubricant for joint cavities.

Adhesion Belts:

Made up of glycoproteins, is found below the tight junction. Located between the plasma membrane of adjacent cells and acts as a weak glue holding cells together. Not as strong of connection as desmosomes.

Multicellular -vs- Unicellular:

Multicellular: Most exocrine glands are composed of many cells... Unicellular: Some exocrine glands are composed of a single cell. (Goblet cells are unicellular that secret mucus.)

Stratified Squamous:

STRUCTURE: Multiple layers of cells that are cube-shaped in the basal layer and progressively flattened toward the surface. Can be non-keratinized (moist) or keratinized. In non, surface cells retain a nucleus and cytoplasm, in keratinized the cytoplasm of cells at surface is replaced by protein called keratin, and cells are dead. FUNCTION: Protect against abrasion, a barrier against infection, reduction of water loss from the body. LOCATION: Keratinized - primarily in the skin. Non-keratinized - mouth, throat, larynx, esophagus, anus, vagina, inferior urethra, cornea.

Stratified Columnar:

STRUCTURE: Multiple layers of cells with tall, thin cells resting on layers of more cube-shaped cells, the cells are ciliated in the larynx. FUNCTION: Protection, secretion. LOCATION: Mammary gland ducts, larynx, a portion of male urethra.

Stratified Cuboidal:

STRUCTURE: Multiple layers of somewhat cube-shaped cells. FUNCTION: Secretion, absorption, protection against infection. LOCATION: Sweat gland ducts, ovarian follicular cells, salivary gland ducts.

Pseudostratified Columnar:

STRUCTURE: Single layer of cells, come are tall and thin, reach the free surface, others do not. The nuclei of these cells are at different levels and appear stratified, are almost always ciliated and associated with goblet cells that secrete mucus onto the free surface. FUNCTION: Synthesize and secrete mucus onto the free surface, move mucus or fluid that contains foreign particles over the surface of the free surface and from passages. LOCATION: Lining of the nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, bronchi of the lungs.

Simple Cuboidal:

STRUCTURE: Single layer of cube-shaped cells, some have microvilli (kidney tubules) or cilia (terminal bronchioles of the lungs). FUNCTION: Secretes and absorbs by cells of the kidney tubules, secretion by cells of glands and choroid plexuses, movement of particles embedded in mucus out of the terminal bronchioles by ciliated cells. LOCATION: Kidney tubules, glands and their ducts, choroid plexuses of the brain, lining of terminal bronchioles of the lungs, surfaces of the ovaries.

Simple Squamous:

STRUCTURE: Single layer of flat, often hexagonal cells, nuclei appear as bumps when viewed as a cross section. FUNCTION: Diffusion, filtration some secretion and some protection against friction. LOCATION: Lining of blood vessels, heart, lymphatic vessels and small ducts. Lining of serous membranes of body cavities.

Simple Columnar:

STRUCTURE: Single layer of tall, narrow cells, some have cilia (bronchioles of lungs, auditory tubes, uterine tubes and uterus) or microvilli (intestines). FUNCTION: Move particles out of the bronchioles of lungs by ciliated cells, partially responsible for the movement of oocytes thru the uterine tubes by ciliated cells, secretion by cells of the glands, the stomach and the intestines, absorptions by cells of the small and large intestines. LOCATION: Glands and some ducts, bronchioles of lungs, auditory tubes, uterus, uterine tubes, stomach, intestines, gallbladder, bile ducts, ventricles of the brain.

Transitional Epithelial:

STRUCTURE: Stratified cells that appear cube-shaped when the organ or tube is not stretched and squamous when the organ or tube is stretched by fluid, the number of layers also decreases on stretch. FUNCTION: Accommodate fluctuations in the volume of fluid in organs or tubes, protect against the caustic effects of urine. LOCATION: Lining of the urinary bladder, ureters, superior urethra.

Endocrine:

Secretion into the body. Are hormones secreted into the body thru the bloodstream.

Glands

Secretory organs that secrete chemicals.

Connective Tissue Cell Types:

Specialized cells of various connective tissues produce extracellular matrix, the name of the cell identifies it's functions: 1.) Blasts - create the matrix. 2.) Cytes - maintain the matrix. 3.) Clasts - break it down for remodeling.

Goblet Cells:

Specialized columnar epithelial cells, contain abundant organelles, such as ribosomes, endoplasmic reticulum, Golgi apparatuses and secretory vessels. Responsible for synthesizing and secreting mucus. (Endocrine Glands)

Epithelial Surfaces:

a.) Free surface - is attached to other cells. Can be smooth or folded. Can have microvilli or cilia. Smooth reduces friction. b.) Lateral surface - attached to other epithelial cells. c.) Basal surface - attached to the basement membrane. d.) Basement membrane - attached to surface on back side.