Tissues (Ch. 4) Flashcards
What are the four types of tissue?
- Epithelial tissue (covering)
- Connective tissue (support)
- Muscle tissue (movement)
- Nervous tissue (control)
What does nervous tissue do, and what are some examples?
Internal communication
- Brain
- Spinal cord
- Nerves
What does muscle tissue do, and what are some examples?
Contracts to cause movement
- Skeletal muscle tissue (attached to bones)
- Cardiac muscle tissue (heart)
- Smooth muscle tissue (walls of hollow organs)
What does epithelial tissue do, and what are some examples?
Forms boundaries between different environments
Protects, secretes, absorbs, and filters
-Lining of GI tract organs and other hollow organs
-Skin surface (epidermis)
What does connective tissue do, and what are some examples?
Supports, protects, and binds other tissues together
- Bones
- Tendons
- Fat and other soft padding tissue
What is the study of tissues called?
Histology
What are the 3 steps of preparing an animal tissue specimen for microscope viewing?
- Needs to be fixed (preserved)
- Needs to be cut into sections (slices) thin enough to transmit light
- Needs to be stained for contrast
When animal tissue is preserved, what is known as “artifacts?”
Little alterations that form as a result of being preserved for a long time or strange sectioning
What are some special characteristics of epithelial tissue?
Polarity
Avascularity
Support from connective tissue
High regenerative capacity
What is the apical surface of epithelial tissue?
Apical surface - upper free surface exposed to the body exterior or the cavity of an internal organ
- Usually have microvilli (finger-like extensions of the plasma membrane - increased surface area –> increased absorption)
- Dense microvilli forest is called a “brush border”
- Some apical surfaces have cilia (hair-like projections used for propelling substances along their surface)
What is the basal surface of epithelial tissue?
Basal surface - attached surface
What is basal lamina?
Filter and scaffolding
Lamina = sheet
Non-cellular, adhesive sheet made of glycoproteins and fine collagen fibers
Acts as a selective filter, determining which molecules diffusing from the underlying connective tissue are allowed to enter the epithelium
Acts as scaffolding along which epithelial cells can migrate to repair a wound
What is the function of specialized contacts between epithelial cells?
Special junctions keep proteins in place, which keeps the overall structure and basal-apical polarity intact
What is the basement membrane?
Basal lamina (epithelial) and the reticular lamina (connective tissue) are joined to strengthen and reinforce the epithelial sheet Reinforcement = resist stretching and tearing, defines epithelial boundary
How do epithelial cancer cells react at the basement membrane?
It does not respect the basement membrane and travels freely, which is how cancer spreads so easily.
How are epithelial cells nourished? Are epithelial cells innervated or not? Are they vascular or avascular?
Innervated - have nerves
Avascular - no blood flow
Nourishment from substance diffusing from blood vessels in underlying connective tissue
Do epithelial cells regenerate easily? How do they know when to regenerate?
Yes. When basal-apical polarity and lateral contacts are destroyed, regeneration ramps up.
What is the difference between simple and stratified epithelia?
Simple - one layer - suitable for areas of high absorption, secretion, and filtration
Stratified - many layers - suitable for high-abrasion areas like the mouth
What shape are epithelial cells (when viewed from above)
Hexagonal, like honeycomb
What are the three heights of epithelial cells?
Squamous - flat (squam = scale)
Cuboidal - boxy
Columnar - column-shaped
Which kind of cells resemble fried eggs, when sectioned vertically?
Simple squamous cells
What is the endothelium?
Simple squamous cell layer
Provides slick lining for lymphatic vessels and hollow cardiac system organs (heart, blood vessels, and capillaries)
Mesothelium: shape, function, and locations
Shape: Simple squamous layer
Function: Provides slick lining
Locations: Is the epithelium in serous membranes (line the ventral body cavity and cover its organs)
Simple Cuboidal Epithelium: shape, functions, and locations
Shape: single layer, cube-shaped (height = width)
Functions: Secretion and absorption
Locations: Smallest ducts of glands and many kidney tubules
Resembles: beads on a string
Simple Squamous Epithelium: shape, functions, and locations
Shape: single layer, flat
Functions: Permeable membranes, secretion and absorption
Locations: Kidneys, lungs
Resembles: fried egg
Simple Columnar Epithelium: shape, functions, and locations
Shape: single layer, tall
Functions: Absorption and secretion
Locations: Digestive tract from stomach to rectum - has special cilia, also uterus
Resembles: soldiers in a row
Pseudostratified Columnar Epithelium: shape, functions, and locations. What are the special things that always indicates pseudostratified cells when you see them?
Shape: single layer of differing heights; all cells touch the basement, but some don’t reach the free surface. May have cilia.
Function: Mucus secretion
Location: Trachea and upper respiratory tract, also sperm-carrying ducts
Special thing: this is the only type of tissue that has cilia
Stratified Squamous Epithelium: shape, functions, and locations
Shape: Layer of fried eggs on top of cuboidal or columnar cells
Functions: Thick protective roles. Can be keratinized (thicker, i.e. epidermis/skin) or nonkeratinized.
Stratified Cuboidal or Columnar Epithelium: shape, functions, and locations
Locations: Rare - in ducts of some larger glands like mammaries
No pics in books - look in Atlas Plates 8 and 9
Transitional Epithelium: shape, functions, and locations
Shape - mixed up - resembles stratified squamous and stratified cuboidal, with squamous nearer to the free surface, and basal cells more cuboidal or columnar
Functions: Stretch to hold urine (undergoes TRANSITIONS)
Locations: Bladder and urinary tracts
What is the difference between an endocrine and an exocrine gland?
Endocrine = internally secreting (inside the body) Exocrine = externally secreting (out of the inside of the body) Difference = where they release their product (secretion)
Where are unicellular glands found in the body, vs. multicellular glands?
Unicellular are scattered within epithelial sheets
Multicellular grow in or out (invagination or exvagination) from an epithelial sheet and usually have ducts
What kind of secretions do endocrine glands produce?
Hormones
Are endocrine glands mostly ducted or ductless?
Ductless
Where do exocrine glands secrete their secretions?
Onto the body’s surface or into body cavities
What is the role of unicellular exocrine glands?
Mucous cells and goblet cells
What is the role of multicellular exocrine glands? What are their two basic parts?
- Duct
2. Secretory unit (acinus)
What are the two classifications of multicellular exocrine glands according to duct structure?
Single (unbranched)
Compound (branched)
What are the three classifications of multicellular exocrine glands according to structure of secretory parts?
Tubular (forms tubes)
Alveolar (forms flasks)
Tubuloalveolar (has both types)
What is the difference between a merocrine gland and a holocrine gland?
Merocrine (secrete product as it is produced, by exocytosis) (most glands)
Holocrine (store secretion until it ruptures) (sebaceous glands)
What is the common origin of connective tissue?
Mesenchyme (an embryonic tissue)