Chapter 4: Tissue Flashcards
Tissues
Groups of cells in similar structure that perform common or related function
Histology
Study of tissue
What are the 4 basic types of tissues?
1) Epithelial
2) Connective
3) Muscle
4) Nervous Tissue
What steps do you need to do to look at a tissue in detail under a microscope?
1) Fixed (Preserved)
2) Sectioned (sliced)
3) Stained (colored)
Epithelial Tissue
A sheet of cells that covers body surfaces or cavities
What are the 2 main forms of epithelial tissue?
1) Covering and lining epithelia
2) Glandular epithelia
What are the main functions of epithelial tissue?
- Protection
- Absorption
- Secretion
What are the special characteristics of Epithelial Tissues?
- Polarity
- Specialized contacts
- Supported by connective tissues
- Avascular, but innervated
- Regeneration
Polarity
- Apical (top)
- Basal (bottom)
Specialized contacts
Special cell contacts including desmosomes and right junctions
Supported by connective tissues
- Basal surface is connected to connective tissue
- Gives structural support, nutrients and helps resist epithelial tears
Avascular, but innervated
- Connective tissue supplies blood because there are no blood vessels in the epithelial tissue
- There are many nerve endings in epithelial tissue
Regeneration
- Epithelial cells are often destroyed, so they are easily replaced and undergo mitosis often
- Some cells are exposed to friction, some to hostile substances, resulting in damage
• Ex: Stomach lining
Simple Epithelial
Involved in absorption, secretion or filtration processes
Simple Squamous Epithelialium
Cells are flattened laterally and cytoplasm is sparse
- Function: rapid diffusion
• Ex: lungs, blood vessels
Simple Cuboidal Epithelium
- Function: secretion and absorption
• Ex: smallest ducts of glands, kidney tubules
Simple Columnar Epithelium
Some cells have microvilli (absorption), and some have cilia (movement)
Some layers contain mucus-secreting goblet cells (secretion)
- Function: in absorption, secretion and movement of mucus, enzymes and other substances
• Ex: in small intestines, gallbladder
Pseudostratified Columnar Epithelium
Many cells are ciliated
- Function: involved in secretion, particularly of mucus, and also in movement of mucus via ciliary sweeping action
• Ex: trachea
Stratified Epithelial Tissues
Involve 2 or more layers of cells
New cells regenerate from below
• Basal cells divide and migrate toward surface
• More durable than simple epithelia because protection is the major role
Stratified Squamous Epithelium
- Most widespread of stratified epithelia
- Free surface is squamous, with deeper cuboidal or columnar layers
- Located in area of high wear and tear (ex: skin)
- Keratinized cells found in skin; nonkeratinized cells are found in moist linings
Glandular Epithelia
Classified by:
- Site of product release
- Relative number of cells forming the gland
Gland
One or more cells that makes and secretes an aqueous fluid called a secretion
Endocrine
- Internally secreting
- Ductless glands
• Ex: hormones
Exocrine
- Externally secreting
- More common and have ducts
• Ex: Sweat, salivary
What are the sites of product release of Glandular Epithelia?
1) Endocrine
2) Exocrine
What are the “relative number of cells forming the gland”?
- Unicellular
* Multicellular
Unicellular
• Ex: goblet cells
Multicellular
3 Types:
• Merocrine
• Holocrine
• Apocrine
Merocrine
Secrete using exocytosis (sweat gland)
Holocrine
Accumulate products than rupture sebaceous oil glands
Apocrine
Accumulates products within and then only the top rupture (possibly mammary glands)
What are the major functions of connective tissue?
Binding and support, protecting, insulating, storing reserve fuel, and transporting substances (blood)
What are the 4 main classes of connective tissue?
- Connective tissue proper
- Cartilage
- Bone
- Blood
What are the 3 common characteristics of Connective Tissue?
- Common embryonic
- Varying degrees of vascularity
- Cells are suspended/ embedded in extracellular matrix (ECM)
Common Embryonic Origin
All arise from mesenchyme tissue as their tissue of origin
Varying degrees of vascularity
Different amounts of blood vessels, for example, cartilage is avascular, bone is highly vascularized
Cells are suspended/ embedded in extracellular matrix (ECM)
- ECM is a protein-sugar mesh
* Matrix supports cells to make them durable
What are the 3 main structural elements of connective tissues?
- Ground substance
- Fibers
- Cells
What elements make up the extracellular matrix?
Ground Substance and Fibers
Ground Substance
Unstructured gel-like material that fills space between cells
• Medium through which solutes diffuse between blood capillaries and cells
What are the components of Ground Substance?
- Interstitial fluid
- Cell adhesion proteins (“glue” for attachment)
- Proteglycans (sugar proteins)
- Water
What are the 3 types of connective tissue fibers?
- Collagen
- Elastic Fibers
- Reticular
Collagen
Strongest and most abundant type of fiber
Elastic Fiber
Allow for stretch and recoil
Reticular
• Short, fine, highly branched collagenous fibers
Branching forms networks that offer more “give”
Cells
“Blast” cells
- Immature form of cells that actively secretes ground substance and ECM fibers
What are the 3 types of “Blast” cells?
- Fibroblasts
- Chondroblasts
- Osteoblasts
Fibroblasts
Found in connective tissue proper
Chondroblasts
Found in cartilage
Osteoblasts
Found in bone
“Cyte” cells
Mature, less active form of “blast” cells, that now becomes part of and helps maintain health of matrix
What are the other types of cells found in connective tissues?
- Fat cells
- White blood cells
- Mast cells
- Macrophages
Fat cells
Store nutrients
White blood cells
Tissue response to injury
Mast cells
Initiate local inflammatory response against foreign microorganism story detect
Macrophages
Phagocytic cells that “eat” dead cells, microorganisms
- function in immune system
Connective Tissue Proper
- CT Proper: Loose connective tissue
* CR Proper: Dense connective tissue
Loose Connective Tissue
- Areolar
- Adipose
- Reticular
Areolar Loose Connective Tissue
Universal packaging material between other tissues; supports and binds other tissues
• Contains fibroblasts that secrete loose arrangement of mostly collagen fibers
Adipose Loose Connective Tissue
Shock absorption, insulation, and energy storage
• Fat tissue
• Similar to areolar tissue but greater in nutrient storage
• Richly vascularized
Reticular Loose Connective Tissue
Form a mesh-like stroma that acts as a support for blood cells in lymph nodes, spleen, and bone marrow
Dense Connective Tissue
Function: Very high tensile strength; can withstand high tension and stretching
• Made up of collagen fibers
• Vascularized
What are the 3 different types of Dense Connective Tissue?
- Dense Regular
- Dense Irregular
- Elastic
Dense regular
Very strong, stretches in one direction, found in dermis, joints, ligaments
Dense irregular
Can stretch in multiple directions, also in the dermis
Elastic
Very stretchy, found in some ligament and around blood vessels
Cartilage
- Matrix secreted from chondroblasts (during growth) and chondrocytes (adults)
- Tough yet flexible material that lacks nerve fibers
- Avascular
Avascular
Receives nutrients from membrane surrounding it (perichondrium)
What are the 3 types of cartilage?
- Hyaline cartilage
- Elastic cartilage
- Fibrocartilage
Hyaline cartilage
Found at tips of long bones, nose, trachea, larynx, and cartilage of the ribs
Elastic Cartilage
Found in ears and epiglottis
• Similar to Hyaline but with more elastic fibers
Fibrocartilage
Strong so found in areas such as intervertebral discs and joints
• Properties between hyaline and dense regular tissue
Bone
Function: supports and protects body structures; stores fat and synthesizes blood cells in cavities
• Osteoblasts produce matrix
• Osteocytes maintain the matrix
- Osteons: individual structural units
- Richly vascularized
Blood
Function: transports and carries nutrients, wastes, gases and other substances
- Contains white blood cells and platelets
- Fibers are soluble proteins that precipitate during blood clotting
