Characteristics Of Epithelial Tissues

Epithelial tissue, connective tissue, muscular tissue, nervous tissue

1. Covers and lines body surfaces 2. Cells are densely packed together with minimal amount of intercellular substance 3. Cells are firmly attached by intercellular junctions 4. Cells rest on a basement membrane partly derived from underlying connective tissue

1. Anchors epithelium to underlying connective tissue 2. Acts as a selective barrier for diffusion

Diffusion from underlying connective tissue

It is richly supplied with nerve fibers

It is avascular

Ectoderm, mesoderm, endoderm

1. Ectoderm- epidermis of skin 2. Endoderm- epithelium of digestive tract 3. Mesoderm- the serous lining of body cavities

1. Covering/lining epithelium 2. Glandular epithelium (endocrine and exocrine) 3. Neuroepithelium (taste buds)

The number of layers of cells and the shape of surface cells

Simple (one layer of cells) and stratified (2 or more layers of cells)

Squamos (flat), cuboidal (square), and columnar (tall)

They are formed of one layer of cells resting on a basement membrane

Absorption, diffusion, secretion, excretion

1. simple squamos 2. simple cuboidal 3. simple columnar 4. pseudostratified columnar

1. Its major function is diffusion 2. Found in bowman's capsule in kidney, lining of blood vessels (endothelium), lining of body cavities (mesothelium), and alveoli of lungs

1. Absorption, secretion 2. Convoluted tubules of kidney, thyroid gland, and germinal epithelium of ovary

1. Functions are absorption and secretion 2. Simple columnar ciliated epithelium is located in the lining of the uterus and uterine tube. Simple columnar non-ciliated epithelium is located in the lining the stomach, small intestine, large intestine, and gall bladder

There is one layer of cells and all cells touch the basement membrance, but not all cells reach the luminal surface. This is due to cells of different sizes being lined up next to each other.

The nuclei appear to be arranged in more than one layer. This is a false appearance.

1. Pseudostratified columnar ciliated with goblet cells, which is found in the respiratory system (nasal cavity, trachea, and bronchi) 2. Pseudostratified columnar with stereocilia, which is found in the male reproductive system

Non-motile microvilli

Protection- they have the ability to withstand wear and tear

1. Stratified squamos 2. Stratified cuboidal 3. Stratified columnar 4. Transitional

1. Keratinized: epidermis of skin 2. Non-Keratinized: oral cavity, pharynx, esophagus, vagina (wet), cornea

This is a rare type of epithelium. It is only found in the small ducts of sweat glands of the skin and in ovarian follicles

This is a rare type of epithelium. It is present in the large ducts of the salivary glands, conjuctiva (mucus membrane that lines eyelids), and penile urethra

A type of stratified epithelium that changes shape and can resemble either stratofied squamos or stratified cuboidal epithelium, depending on whether it is stretched or contracted. It is found in the urinary system (calyces of kidney, ureter, urinary bladder, and prostatic urethra in males and females)

1. Relaxed (empty): 4-6 layers and the surface cells are cuboidal, binucleate cells 2. Stretched (distended, full): appears to have only 2-3 layers and surface cells look cuboidal with convex free border and rounded nuclei

1. Tight or occluding junction: tight seal that obstructs transmission between cells 2. Adherent junctions: are sites of strong adhesion between cells 3. Gap/communicating junctions: allow the transmission of ions and small molecules between cells 4. Desmosomes: are adherent junctions that connect adjacent cells at certain spots only 5. Hemidesmosomes: connect epithelial cells to underlying connective tissue

Tonofilaments/intermediate filaments are inserted into electron-dense plaques of material on the cytoplasmic surfaces of the junctional membranes

1. Cilia 2. Microvilli (brush border) 3. Stereocilia

simple/pseudostratified columnar ciliated epithelium

It is attached to basal bodies (same structure as centrioles), composed of microtubules covered with cell membrane, and they beat to move things along a surface. They are located in the respiratory tract (move things away from lungs) and fallopian tubes (move ovum towards uterus)

The name for the microvilli-covered surface of simple cuboidal epithelium and simple columnar epithelium cells. They are found in the small intestine and proximal convoluted tubules of the kidney.

They are very short and formed of folds of cell membrane and a core of actin filaments. They increase the surface area for absorption.

It contains long microvilli that project from the luminal pole of the cell. It is composed of a core of actin filaments and only found on columnar cells. It is located in male genital passages (epididymis and vas deferens).

To absorb testicular fluid in the epididymis and vas deferens that was produced by cells in the testes.

Modified columnar cells that synthesize and secrete mucus, which are found in the GI tract and the respiratory tract.

Unicellular gland

They are cells that contain contractile actin proteins and surround and squeeze secretory units and ducts. They are found in exocrine glands inlcuding the lacrimal, salivary, mammary, and sweat glands.

An organized collection of cells derived from covering epithelial cells. They synthesize, secrete, and store the secretion.

Vascular

1. Exocrine: contains ducts and maintains connection with surface cells 2. Endocrine: do not have ducts, secrete directly into blood, loses connection with surface cells

1. Proliferation of surface cells 2. Downward growth and invasion of the underlying connective tissue 3. Differentiation into exocrine and endocrine

Glands formed of secretory units formed of secretory epithelial cells that release secretion into a lumen and a duct that conveys secretion to a surface.

1. Branching of the duct 2. Shape of the secretory unit 3. Type of secretion 4. Method/mode of secretion

1. Simple: ducts do not branch 2. Compound: branched duct system

1. Tubular: tube-like 2. Acinar/alveolar: bulbous-like

1. Serous: watery secretion containing enzymes. Ex-parotid (contains salivary amylase) 2. Mucous: thick mucous secretion. Ex- goblet cells 3. Mixed: has both serous and mucous acini. Ex- submandibular gland

1. Eccrine/merocrine: secretion released without loss of cell. Ex- sweat glands 2. Apocrine: apex of cell is lost with secretion. Ex- mammary glands 3. Holocrine: cell is lost as part of the secretion. Ex- sebaceous glands of skin

By their arrangements

1. Follicular: arranged in rings called follicles (secretion stored inside follicles), lined with simple cuboidal epithelium, and follicles are surrounded with blood capillaries to transport secretion. Ex- thyroid gland. 2. Anastomosing cords: granules are stored inside cells, every cell must be in contact with a capillary for transport of secretion. Ex- parathyroid gland.

1. Protection: covers body surfaces (epidermis of skin, cornea) or lines hollow organs (digestive tube, urinary/reproductive passages), blood vessels, and body cavities 2. Absorption (intestines and kidney) 3. Secretion (glandular epithelium) 4. Excretion (kidney) 5. Sensation (neuroepithelium- taste buds) 6. Contractility (myoepithelial cells of glands) 7. Reproduction (germinal epithelium of ovary and testis)