CH 4, 5, 6

Lateral surfaces of an epithelial cell

face the adjacent cells on either side, may contain tight junctions, adherens junctions, desmosomes, and/or gap junctions.

The apical (free) surface of an epithelial cell

faces the body surface, a body cavity, the lumen (interior space) of an internal organ, or a tubular duct that receives cell secretions. Apical surfaces may contain cilia or microvilli.

Tactile epithelial cells

function in the sensation of touch.

Melanocytes

produce the pigment melanin

Epithelial tissues have three major functions

(1) selective barriers that limit or aid the transfer of substances into and out of the body; (2) secretory surfaces that release products produced by the cells onto their free surfaces (3) protective surfaces that resist the abrasive influences of the environment

General Features of Epithelial Tissue

- Cells are arranged in sheets - Cells are densely packed - Many cell junctions are present - Epithelial cells attach to a basement membrane - Epithelial tissue is avascular but does have a nerve supply - Mitosis occurs frequently

4 major types of cells of the epidermis

- Keratinocytes - Melanocytes - Intraepidermal macrophages - Tactile epithelial cells

What does the integumentary system do

- Maintains the body's integrity - Maintains temperature - Converts inactive vitamin D to its active form - Provides sensory information - Maintains homeostasis.

3 major layers of the skin

- The outer is called the epidermis - The inner is called the dermis - The subcutaneous (subQ) layer (also called the hypodermis) is located underneath the dermis

The epidermis is composed of four layers in thin skin, and five layers in thick skin. They are (from deep to superficial):

- The stratum basale - The stratum spinosum - The stratum granulosum - The stratum lucidum (only present in thick skin) - The stratum corneum

Types of skin:

- Thin (hairy) skin covers all body regions except the palms, palmar surfaces of digits, and soles. - Thick (hairless) skin covers the palms, palmar surfaces of digits, and soles.

Epithelial tissues may be divided into two types

1. Covering and lining epithelium forms the outer covering of the skin and some internal organs. It also forms the inner lining of blood vessels, ducts, and body cavities, and the interior of the respiratory, digestive, urinary, and reproductive systems. 2. Glandular epithelium makes up the secreting portion of glands such as the thyroid gland, adrenal glands, and sweat glands.

Body tissues can be classified into four basic types according to their structure and function. What are those tissues?

1. Epithelial tissues 2. Connective tissues 3. Muscular tissues 4. Nervous tissue

adhesion belts

Extensive zones formed by adherens junction: help epithelial surfaces resist separation during various contractile activities, as when food moves through the intestines.

Nail structures include

Free edge Transparent nail body (plate) with a whitish lunula at its base Nail root embedded in a fold of skin

The dermis is composed of connective tissue containing collagen and elastic fibers.

It contains two regions: The papillary region lies just below the epidermis The reticular region consists of dense irregular connective tissue

Nails

Made of keratinized epidermal cells

Hair

Present on most surfaces except the palms, anterior surfaces of fingers, and the soles of the feet. Composed of dead, keratinized epidermal cells. Genetics determines thickness and distribution.

The skin contains 4 types of glands.

Sebaceous (oil) glands are connected to hair follicles. Eccrine sweat glands are the most numerous. Apocrine sweat glands are located mainly in hairy skin. Ceruminous glands are modified sweat glands located in the ear canal.

The parts of a hair

The shaft (above the skin surface) The follicle (below the level of the skin) A root that penetrates into the dermis includes: An epithelial root sheath A dermal root sheath

Intraepidermal macrophages

are involved in the immune responses.

cadherins

Transmembrane glycoproteins

Vitiligo

a chronic disorder that causes depigmentation patches in the skin. The precise cause, is not known, but is most likely a combination of genetic factors coupled with a disorder of the immune system (autoimmune disease).

Albinism

a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair, and eyes due to a defect of an enzyme involved in the production of melanin.

Plaque

a dense layer of proteins on the inside of the plasma membrane that attaches both to membrane proteins and to microfilaments of the cytoskeleton

pathologist

a physician who specializes in laboratory studies of cells and tissues to help other physicians make accurate diagnoses.

gland

a single cell or a mass of epithelial cells adapted for secretion

basement membrane

a thin extracellular layer that commonly consists of two layers, the basal lamina and reticular lamina

avascular

a- without; -vascular vessel

Muscular tissues

composed of cells specialized for contraction and generation of force. In the process, muscular tissues generate heat that warms the body.

Tight junctions

consist of web like strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells

epithelial tissue/epithelium

consists of cells arranged in continuous sheets, in either single or multiple layers. Because the cells are closely packed andare held tightly together by many cell junctions, there is little intercellular space between adjacent plasma membranes. Epithelial tissues form coverings and linings throughout the body.

Cell junctions

contact points between the plasma membranes of tissue cells.

Adherens junctions

contain plaque

desmosomes

contain plaque and have transmembrane glycoproteins (cadherins) that extend into the intercellular space between adjacent cell membranes and attach cells to one another like adherens junctions. Unlike adherens junctions, the plaque of desmosomes does not attach to microfilaments.

Epithelial tissues

cover body surfaces and line hollow organs, body cavities, and ducts; they also forms glands. This tissue allows the body to interact with both its internal and external environments.

Nervous tissue

detects changes in a variety of conditions inside and outside the body and responds by generating electrical signals called nerve action potentials (nerve impulses) that activate muscular contractions and glandular secretions.

The basal surface of an epithelial cell

is opposite the apical surface. The basal surfaces of the deepest layer of epithelial cells adhere to extracellular materials such as the basement membrane. Hemidesmosomes in the basal surfaces of the deepest layer of epithelial cells anchor the epithelium to the basement membrane

gap junctions

membrane proteins called connexins form tiny fluid-filled tunnels called connexons that connect neighboring cells

protein laminin

present in the basement membrane

Keratinocytes

produce keratin - a tough fibrous protein that provides protection.

Connective tissues

protect and support the body and its organs. Various types of connective tissues bind organs together, store energy reserves as fat, and help provide the body with immunity to disease-causing organisms.

Hemidesmosomes

resemble desmosomes, but they do not link adjacent cells.

Melanin is produced by melanocytes in the

stratum basale

integrins

the transmembrane glycoproteins in hemidesmosomes

five most important types of cell junctions

tight junctions, adherens junctions, desmosomes, hemidesmosomes, and gap junctions