Chapter 4 Flashcards
What is a tissue?
A group of cells that usually have a common origin in an embryo and function together to carry out specialized activities
What are the Four basic types of body tissues?
- Epithelial tissue
- Connective tissue
- Muscular tissue
- Nervous tissue
What are cell junctions and what type of junctions is there?
Contact points between the plasma membranes of tissue cells
- Tight junctions
- Adherents junctions
- Desmosomes
- Hemideamosomes
- Gap junctions
What is the function of tight junctions?
Fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells. Prevent contents of organs from leaking.
What are adherents junctions and their function?
Contain 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. Cells join together with caherins
Adherents junctions help epithelial surfaces resist separation during various contractile activities like food moving through intestines
What are desmosomes and their function?
Contain plaque and have transmembrane glycoproteins(Cadherins) that extend into the intercellular space between adjacent cell membranes and attach cells to one another but unlike adherents junction the plaque of desmosomes does not attach to microfilaments
Contributes to stability of cells and tissue common among epidermis, cardiac muscle cells of heart
What are hemidesmosomes and their function?
Resemble desmosomes, but they do not link adjacent cells.
Transmembrane glycoproteins are interims, that attach to intermediate filaments made of keratin inside cell and attach to laminin outside of cell
What are gap junctions and their function?
At the gap junction connections form tiny fluid-filled tunnels called connexons
Gap junctions transfer nutrients and waste in a vascular tissue like the lens and cornea, allow cell tissue to communicate, in an embryo chemical and electrical signals can regulate growth, allow nerve impulses to travel rapidly
What are the differences between epithelial tissue and connective tissue?
- Epithelial tissue is tightly packed with little extra cellular matrix and connective tissue has a large amount of extra cellular matrix
- Epithelial tissue has no blood vessels and connective tissue has a significant network of blood vessels
- Epithelial tissue forms surface layers and is not covered by other tissue other than blood vessel lining where blood passes over
What is epithelial tissue and it’s function?
Consists of cells arranged in continuous sheets, in either single or multiple layers
Epithelial tissue protects,secretes (mucous, hormones, and enzymes), absorbs (nutrients in the gastrointestinal tract), and excretes (various substances in the urinary tract)
The various surfaces of covering and lining epithelial cells often differ in structure and have specialized functions
Is avascular and has its own nerve supply
What is the apical surface of an epithelial cell?
Apical surface faces the body surface, a body cavity, the lumen of an internal organ, or a tubular duct that receives cell secretions
May contain cilia or microvilli
What is the lateral surface of an epithelial cell?
Faces adjacent cells on either side
May contain tight, adherens, desmosomes, gap junctions
What is the basal surface of an epithelial cell?
Opposite the apical surface
They adhere to extra cellular materials such as basement membrane
What is the basement membrane?
A thin extracellular layer that commonly consists of two layers, basal lamina and reticular lamina
Basement membranes form a surface along which epithelial cells migrate during growth or wound healing, restrict passage of larger molecules between epithelium and connective tissue and participate in filtration of blood in the kidneys
What is basal lamina layer of the basement membrane?
Closer to and secreted by the epithelial cells. Laminin molecules in this layer adhere to integrity in hemidesmosomes and attach epithelial cells to the basement membrane
What is the reticular lamina layer of the basement membrane?
Closer to the underlying connective tissue and contains proteins such as collagen produced by connective tissue cells called fibroblasts
How does epithelial tissue exchange substances with connective tissue?
Diffusion
How do epithelial tissues contestant or repair and renew itself?
It has a high rate of cell division
What are the different roles epithelial tissue play in the body?
Protection Filtration Secretion Absorption Excretion
What are the two types of epithelial tissue?
- Covering and lining epithelium/ surface epithelium
2. glandular epithelium
How can you classify epithelial tissue?
- Arrangement of cells in layers
2. Cell shape
What are the different epithelium layers?
- Simple - single layer of cells functions in diffusion, osmosis, filtration, secretion and absorption
- Pseudostrtified - appears to have multiple layers because nuclei are at different levels but is actually simple
- Stratified - consists of two or more layers that protect underlying tissues found in locations with considerable wear and tear
What are the different cell shapes?
Squamous cells
Cuboidal cells
Columnar cells
Transitional cells
Squamous cells
Thin, allowing for rapid passage of substances through them