TISSUES

tissues

Group of specialized cells with similar structure and function and the extracellular substances surrounding them

histology

the study of the microscopic structure of tissues

pathology

study of disease

four types of tissues

epithelial, connective, muscle, nervous

epithelium

the specialized epithelial tissue that forms the epidermis of the skin and the surface layer of mucous membranes

cellular tissue

very little extracellular between the cells

location of epithelial tissue

skin, kidney, trachea, glands, intestines, convoluted tubes

characteristics of epithelia

1. Mostly composed of cells

2. Covers body surfaces

3. Has an exposed surface

4. Attaches at the basal surface

5. Has specialized cell connections and matrix attachments

6. Is avascular

7. Capable of regeneration

free surface/apical surface

Part of the epithelial tissue that is exposed to an open area (either the external environment or to the inside of a hollow organ).

basal surface

surface of the cells anchored in place; attaches epithelial cells to underlying tissues

basement membrane

Cells at the base of an epithelial layer are attached to this; porous, regulates the movement of substances to and from the epithelial tissue above it; where gases, nutrients and waste products diffuse to reach the epithelium

basement membrane disease

Thickened capillaries due to increased production of collagen and laminin in DM

functions of epithelia

1. Protects underlying structures

2. acts as a barrier

3. Passage of substance

4. Secretion of substances

5. Absorption

classification of epithelia

o Number of cell layers o Cell shape

simple epithelium

single layer of cells

stratified epithelium

several layers of cells

pseudostratified epithelium

Multiple layers due to difference in cell height, but are really one layer.

squamous

flat or scalelike

cuboidal

cube shaped

columnar

tall and thin

simple squamous epithelium

single layer of flattened cells; diffusion and filtration; lungs, kidneys, lining of blood vessels and heart, membranes of body cavities

simple cuboidal epithelium

single layer of square-shaped cells; some have microvilli or cilia; secretion, glands, ducts; terminal bronchioles, nasal passages, surface of ovaries, kidney tubules, brain

simple columnar epithelium

single layer of tall, narrow cells; some have cilia or microvilli; movement of particles, secretion and absorption; lining of stomach and intestines, gallbladder, bile ducts, auditory tubes, uterus and fallopian tube, ventricles of the brain, cervix,

pseudostratified columnar epithelium

single layer of tall, narrow cells; appears stratified but isn't; synthesize and secrete mucus, propel debris out of resp tract (cilia); respiratory system: nasal cavity, nasal pharynx, bronchi 1st and 2nd, auditory tube

stratified squamous epithelium

many layers of cube-shaped cells; can be nonkeratinized or keratinized; protects against abrasion, acts as barrier, reduces water loss; skin, mouth, throat, larynx, esophagus, anus, vagina, inferior urethra, corneas

keratinized stratified squamous epithelium

surface cells are replaced by keratin; cells are dead; exposed to the sun

nonkeratinized stratified squamous epithelium

surface cells retain a nucleus and cytoplasm; not exposed to the sun

transitional epithelium

special type of stratified; when stretched - appears squamous, not stretched - appears cuboidal; holds fluids, protects against the caustic effects of urine; bladder, ureter, urethra

stratified cuboidal epithelium

tissue that consists of two or more layers of cube-shaped cells, found in some ducts

Function: protection

Location: Largest ducts of sweat glands, mammary glands, and salivary glands, ovary parotid gland, testes, spleen

free cell surfaces

surface not in contact with other cells

smooth free surface

reduces friction as material moves across it

folded free surface

help organs to change shape; increased surface area

endothelium

the specialized epithelial tissue that lines the blood and lymph vessels, body cavities, glands, and organs

microvili

increase surface area for absorption; lining of small intestine; stationary

cilia

move materials across cell's surface; trachea; not stationary

goblet cells

secrete mucus

cell structures

1. Mechanically bind the cells together

2. Help form a barrier to the movement of molecules or ions

3. Provide a mechanism for intercellular communication

desmosomes

Mechanically bind epithelial cells together

hemidesmosomes

attach epithelial cells to the basement membrane

integrins

membrane proteins; they transmit signals between the ECM and cytoskeleton

tight junctions

Form barriers to movement of molecules or ions between epithelial cells

gap junctions

provide cytoplasmic channels between adjacent animal cells; Consist of groups of channels that allow small molecules and ions to pass from one epithelial cell to an adjacent one

adhesion belts

extensive zones of adherens junctions that encircle a cell the way a belt encircles your waist

plaque

dense layer of protein that attached both to membrane proteins and to microfilament of the cytoskeleton

cadherins

attach cells to other cells

glands

➢ Composed of epithelium supported by a network of connective tissue ➢ Structures that secrete substances onto a surface, into a cavity, or into blood

proteins

pancreas

lipids

adrenal and sebaceous glands

complexes of carbohydrates and proteins

salivary glands

two major types of glands

endocrine and exocrine

endocrine glands

Ductless glands that empty their hormonal products directly into the blood; produces hormones; thyroid, thymus, pituitary

exocrine glands

gland that releases its secretions through tubelike structures called ducts; sweat or oil glands

structure of exocrine glands

unicellular, simple, compound

unicellular glands

single-celled glands; goblet cells

simple glands

Multicellular; single non-branched duct; Secretory portions can be shaped in two: tubular and acinar

tubular glands

Straight narrow tube the same width as the duct

acinar glands

Saclike structure whose width is greater than the width of the duct

simple tubular gland

glands forming a straight tube with no branching of the secretory portion

simple branched tubular gland

gland with several tubular secretory portions branching from the single duct

simple acinar gland

glands with a single saclike secretory portion

simple branched acinar

glands with several acinar secretory portions branching from the single duct

compound gland

Multicellular glands that have several branched ducts

compound tubular gland

glands with multiple ducts, each with a narrow tubular secretory portion

compound acinar gland

glands with multiple ducts, each with several saclike secretory portions

compound tubuloacinar gland

glands with multiple ducts, each with several tubular and acinar secretory portions

Modes of secretion of exocrine glands

merocrine, apocrine, holocrine

merocrine secretion

➢ Release of secretory products through exocytosis ➢ Most common ➢ Goblet cells, temperature-sensitive sweat glands, exocrine portion of the pancreas ex: sweat glands

apocrine secretion

➢ Release of secretory products when a portion of the free surface of the epithelial cell pinches off, releasing cytoplasmic contents ➢ Remainder of the cell is repaired ➢ Release of fatty portion of milk, secretion of earwax ex: mammary glands, secretion of earwax/cerumen

holocrine secretions

➢ Release of secretory products through shedding of entire cells ➢ Once the secretory products have accumulated in the epithelial cell, the cell disintegrates and becomes part of the secretion ➢ Deeper cells in the gland replace lost cells ➢ Sebaceous glands

connective tissue

A body tissue that provides support for the body and connects all of its parts; ➢ Cells far apart ➢ Contains large amounts of extracellular matrix

functions of connective tissue

1. Enclosing and separating other tissues

2. Connecting tissues to one another

3. Supporting and moving parts of the body

4. Storing compounds

5. Cushioning and insulating

6. Transporting

7. Protecting

tendons

attach muscle to bone

ligaments

attach bone to bone

bones

provide rigid support and protect organs and soft tissues

semirigid cartilage

nose, the ears, and the surfaces of joints

joints

allow one part of the body to move relative to other parts

adipose tissue

stores high-energy molecules

bones

store minerals, such as calcium and phosphate

adipose tissue

protects the tissues it surrounds and provides an insulating layer beneath the skin that helps conserve heat

blood

transports gases, nutrients, enzymes, hormones, and cells of the immune system throughout the body

cells of the immune system and blood

provide protection against toxins and tissue injury, as well as against microorganisms

bones

protect underlying structures

-blast

cells build

-clast

cells that break down, remodel