5.1 Epithelial Tissue: Surfaces, Linings, and Secretory Functions

How are exocrine glands classified?

(A) Anatomic Form By structure: (i)Simple; single unbranched (ii)Compound; branched ducts (B) Anatomic Form By Shape of Secretory Portions: (i)Tubular; secretory portion and duct are of uniform diameter. (ii)Acinar; the secretory portion forms an expanded sac. (C) Method of Secretion (i) Merocrine; secretions packaged into secretory vesicles, and release the secretion by exocytosis. (ii) Apocrine; apical membrane around a portion of the glandular cell cytoplasm with the secretory product pinches off and becomes the secretion. (iii) Holocrine; formed from cells that accumulate a product; then disintegrate; a viscous mixture of both cell fragments and the product the cell produced prior to its disintegration.

No blood vessels penetrate: (a) epithelial tissue (b) epithelium

(b)

(3 layers; lamina: "lucida"; "densa"; recticular lamina;) epithelial is bound to a basement membrane at the basal surface. (lucida and densa are closest to the epithelium and contain: collagen fibers, specific proteins, and carbohydrates. Function: strengthen the attachment and form a selective molecular barrier between the epithelium and the underlying connective tissue.

- Attachment to a "basement membrane" anatomy:

epithelia are richly innervated to detect changes in the environment at that body or organ region.

- Extension innervation;

Name the function: epithelial tisues protect both external and internal surfaces from dehydration, abrasion, and destruction by physical, chemical, or biological agents.

- Physical protection

What are the functions of epithelial tissue?

- Physical protection -Selective permeability -Secretions -Sensations.

apical (free/superficial) surface; exposed either to the external environment or to some internal body space. basal surface; attachment at the underlying connective tissue. Intercellular junctions; attach cells laterally

- Polarity (sides of the cell);

What characterizes ALL epithelial?

-.Celluarity - Polarity (sides of the cell) - Attachment to a "basement membrane" -Avascularity - Extension innervation High regeneration capacity

tight packed cells with minimal amounts of extracellular matrix separating them.

-.Celluarity;

All epithelial cells lack blood vessels. Nutrients are obtained: 1. directly across the apical surface 2. diffusion across the basal surface

-Avascularity;

Some epithelial cells are specialized to produce secretions, gland cells may be scattered through the epithelium (layered) cells.

-Secretions

All substances that enter or leave the body must pass through an epithelium, thus, epithelial cells are gate keepers.

-Selective permeability

Epithelial cells contain nerve endings to detect changes in the external environment.

-Sensations.

Why don't epithelial cells have blood vessels?

...

What are the two basic parts of a multicellular exocrine gland?

Acini; produce secretion ducts; release the secretion to the epithelial surface.

What epithelial tissue lines the air sacs of the lungs?

Ciliated Simple Columnar Epithelium

-Cilia projects from the cells mucus covered apical surface, the mucus moves by the beating the cilia. -Goblet cells interdispersed -Present in bronchioles in the lungs, luminal (internal) surface of uterine tubes--helps the oocyte from the ovary to the uterus.

Ciliated simple columnnar epithelium

epithelium lined tube through which the gland sections are discharged onto the epithelial surface.

Duct

Glandular Secretions include

Electrolytes, enzymes, hormones, urea, mucin

Lack ducts and secrete hormones directly into IF and blood.

Endocrine glands

Tissue that covers the body surfaces, lines the body cavities, and forms the majority of glands.

Epithelial tissue

Composed of one or more layers of closely packed cells, it contains little to no extracellular matrix between these cells.

Epithelium

Originate from an invagination of epithelium that burrows into the deeper connective tissues-this connection is usually maintained by a duct. May be unicellular or multicellular

Exocrine glands

Why does an epithelium need to be considered selectively permeable?

For protection and maintenance

Are either individual cells or multicellular organs composed predominately of epithelial tissue. Are either exocrine or endocrine. Function: secrete substances either for use or elimination.

Glands

because the apical surface is exposed to the environment, epithelial cells are easily damaged/lost, thus causing the to have a high regeneration capacity (frequent mitosis)

High regeneration capacity;

What are the differences between holocrine and merocrine glands?

Holocrine glands are cells that accumulate a product. Merocrine glands package secretions into vesicles then release the vesicles via exocytosis.

Chemical messengers to influence cell activities elsewhere in the body.

Hormones

What epithelial tissue contains multiple layers of cells and the most superficial cells (apical) are squamous, dead and filled with keratin.

Keratinized stratified squamous epithelium

Contain numerous cells (acini) that work together to produce a secretion. Contain a duct that transports the secretion to the epithelial surface.

Multicellular exocrine glands.

-Contains microvilli that cannot be seen with a microscope (brushborder) -Scattering of unicellular glands (goblet cells) that secrete mucin (glycoprotein, that when hydrated, forms a mucus.) -Lines digestive tract, from the stomach to the anal canal.

Nonciliated simple columnar epithelium

The type of epithelial in the body is indicated by a two-part name the first part refers to the __________ of epithelial cells, the second part describes the _______ of the cells at the apical surface.

Number Shape

-Composed of single layer of cells that are taller than they are wide -Oval nucleus orientated length wise and located in the basal region of the cell, may contain goblet cells.(noncilliated -apical surface occurs with and without cilia Function: Secretory absorptive

Simple columnar epithelium

Anatomy Contains uniformly shaped cells Ideal for building small ducts and glands (when does a gland/duct not build use this cell?) Single layer of cells that are as tall as they are wide Spherical nucleus located in center of cell. Physiology: Does nucleus location effect physiology? Functions to absorb fluids and other materials. across the apical surface. secretes specific molecules. Eg. Kidney tubules for reabsorption of nutrients, ions, and water filtered from the blood

Simple cuboidal epithelium

How does a simple epithelium differ from stratified epithelium?

Simple epithelium is a single layer mainly used for the diffusion, secretion, and absorption of ions, molecules, etctera. Stratified epithelium is multilayerd and mainly used for protection.

How are epithelial cells classified?

Simple epithelium; one layer thick Stratified epithelium; two or more layers thick

1. Spherical to oval nucleus, 2. single layer of flattened cells, 3. thinnest possible barrier. 4. Specialized/delicate 5. Allows rapid movement of molecules across its surface by diffusion, osmosis or filtration 6. found in inside lumen (inside of blood vessels wall (vein)).

Simple squamous epithelium

What the types of simple epithelium based on cell shape?

Simple squamous epithelium Simple cuboidal epithelium Simple columnar epithelium

name the types of simple epithelieum

Simple squamous epithelium Simple cuboidal epithelium Simple columnar epithelium ciliated nonciliated Pseudostratified ciliated nonciliated.

What are the three classifications of cell shape?

Squamous; flat wide, somewhat irregular in shape Cuboidal; about as tall as are wide Columnar; slender and taller than they are wide. (Transitional); can change shape, depending upon how stretched the epithelium becomes.

-Two or more layers but only the apical layer are columnar. Function: Protective Secretory

Stratified columnar epithelium e.g. Ducts of salivary glands, membranous segment of the male urethra.

-Two or more layers of cuboidal cells. -Forms the wall ducts of most exocrine glands (sweat glands). Function: Protective Fortification of gland duct walls and male urethra

Stratified cuboidal epithelium

-Designed to protect against abrasion and friction. -Multiple cell layers -[only] deepest layer of cells contact the basement membrane. -Cuboidal or polyhedral shape - Exists as keratinized and nonkeratinized function: -protect underlying tissues from damage due to activities that cause abrasion and friction.

Stratified squamous epithelieum

Relaxed or Stretched transition epithelial cell? Apical cells flatten into an almost squamous shape.

Stretched transitional epithelial cell.

-Urinary tract -Appearance varies dependent upon state (relaxed/stretched) -Binucleated (two nuclei)

Transitional epithelium

Do not contain a duct Located close to the surface of the epithelium in which they reside. Most common type is the Goblet cell

Unicellular exocrine glands

Name the types of Stratified epithelium

[non/keratinized] Stratified squamous epithelium Stratified cuboidal epithelium Stratified columnar epithelium Transitional epithelium

What is a pseudostratified epithelium

a simple epithelium with varied cell shapes.

Epithelia are classified by the shape of the cell at the ___________.

apical surface

Why does an epithelium need to be highly regenerative?

because its apical surface is exposed to the environment and in order replace cells that are damaged or lost the epithelial cells undergo mitosis frequently .

-superficial layer composed of cells that are dead. -lack nuclei, all cell organelles, when under a microscope, are filled with keratin (protein) -composes the epidermis

keratinized stratified squamous epithelium

Simple squamous epithelium that forms the serous membranes of body cavities.

mesothelium; name obtained from mesoderm, the embryonic primary germ layer. Serous membranes of the body cavity:

Remain alive all the way to the tissue's apical surface. Kept moist by secretions

nonkeratinized stratified squamous epithelium lines oral cavity, part of the pharynx, esophogus, vagina, anus.

-Appears to consist of multiple layers of cells. - All cells are attached to basement membrane. -Occurs in two forms: ciliated (at the apical surface)/nonciliated. -Not all cells reach the apical surface. Function: Protective secretes, mucin which hydrates to become mucus that traps foreign particles and is moved by the beating cilia.

pseudostratified columnar epithelium

Relaxed or Stretched transitional epithelial cell? Basal cells appear cuboidal or polyhedral Apical cells are large and rounded.

relaxed transitional epithelial cell.

Found in areas where stress is minimal and where filtration, absorption, or secretion is the primary function.

simple epithelium

In a ____ _____ all the cells displace the same shape.

simple epithelium

One cell layer thick, and all epithelial cells are in direct contact with the basement membrane.

simple epithelium

IN a ______ ______ a difference in shape can be seen between cell layers.

stratified epithelium

contains two or more layers of epithelial cells, in direct contact with the basement membrane. Resembles a brick wall. Found in areas likely to be subjected to stress (skin, internal lining of the parynx

stratified epithelium