Learn: BMS 300 Tissues and Skin

tissues

collection of similar cells performing a similar function

organs

two or more tissues working in concert ex: skin

epithelium tissue

-sheet of continuous cells that form boundaries and surfaces

-cells attracted to basal lamina

-have an apical and basal side

squamous epithelial cells

(flattened) epithelia are found in places where there is an advantage to shortening the diffusion distances such as in regions of gas exchange in the lungs and in the lining of capillaries called the endothelium.

cubodial epithelial cells

these epithelia are found in the kidney. Transport of water and salts occurs across this epithelium which you will hear more about in the discussion about excretion.

columnar epithelial cells

epithelia are found mostly lining the walls of the stomach, small, and large intestine. The apical surface of these cells is often thrown into a series of folds called microvilli. Each microvillus contains a bundle of actin filaments to give it shape. Some may be ciliated.

stratified squamous epithelium

-the type of epithelium found in skin

-composed of many layers of epithelia

stratum corneum

top layer of epithelia in stratified epithelium that is a horny layer of dead cells filled with keratin

stratum granulosum

-second layer of stratified epithelium that is filled with glycolipid vesicles that prevent water from entering

stratum spinosum

-third layer of stratified epithelium

-called the spiny layer

stratum basale

-last layer of stratified epithelium where cell division in epithelium occurs

epidermis

-top layer of skin which is made up of keratinocytes

dermis

connective tissue proper formed from fibrocytes

-lies under the epidermis

melanocytes

-pigment synthesizing and secreting cells

-has a role in UV shielding

-secrete melanin

endocrine glands

glands that have no openings to the outside; they are ductless glands

exocrine glands

-ducted; they have ducts that carry their secretions to the outside world

-mammary glands, sweat glands, and sebaceous glands (oil glands) in the skin

carcinoma

-cancerous epithelial cells that continuously replicate

connective tissue

-tissue that are connected by an extra cellular matrix they secrete

-connective tissue proper

-cartilage

-bone

-blood

connective tissue proper

-formed from fibrocytes-

include ligaments, tendons, and dermis

fibrocyte

forms connective tissue proper

cartilage

-formed from chondrocytes

-includes elatic (elastin), fibrocaritilage (collagen), and hyaline (collagen and glycosamino glycans-fibroglass)

chondrocytes

form cartilage

bone

-formed from osteocytes

osteocytes

form bone

blood

-type of connective tissue formed from hematopoeitic stem cells (hemocytoblasts)

anchoring junctions

-hemidesmosomes and desmosomes

-anchor epithelial cells to neighboring cells and the basal lamina

integrin

-transmembrane protein involved in a hemidesmosome, anchoring the protein plague to the basal lamina

actin

-protein involved in short distance transport, and makes up the cytoskeleton

hemidesmosomes

-attach epithelial cells to the basal lamina

- serve to anchor the epithelial cells to the underlying connective tissue.

protein plagues

contains proteins that bind to integrin and actin or keratin

desmosomes

-"weld" the cells in an epithelium together and provide strength to resist shearing forces

-extracellular-to-intracellular links physically attach each epithelial cell to its immediate neighbors

basal lamina

The basilar sides of the epithelial cells are attached to extracellular matrix molecules in this protein

cadherins

-Plagues in adjacent cells are connected to one another by glycoproteins in the extracellular space called....

occluding junctions (tight junctions)

-serve to knit together adjacent cells in an epithelial layer and thereby create an impermeable barrier between the cells

-prevent polar molecules from passing through the extracellular space between the cells and block diffusion of such molecules from the apical to the basal side of the epithelium.

-important in epithelia because epithelia commonly line tubes or cavities such as the intestines where it is important to prevent the indiscriminant movement of molecules from the lumen of the tube into underlying tissue

claudins and occludins

transmembrane proteins used to create a tight junction by binding in extracellular space to form a "dam"

communicating junctions (gap junctions)

composed of transmembrane proteins which assemble to form channels that cross the plasma membrane

connexons

-formed with 6 connexins

-provide a hydrophilic pathway between cells

connexins

-6 of these form a connexon in a gap junction

-have 4 alpha helpix proteins with the hydrophilic R group facing out