Introduction to Basic Tissue Types Flashcards
What are the four basic tissue types and their general function?
Epithelium (barrier)
Muscle (movement)
Nerve (information)
Connective Tissue (support)
What are the functions of the Epithelium?
Protection
absorption
excretion (also forms glands)
sensory reception
movement of materials
What are the functions of the Muscle Tissue?
Specialized for movement Sliding filaments (actin/myosin)
What are the three types of muscle tissue?
Skeletal
Smooth
Cardiac
Where is smooth muscle found?
blood vessels, GI tract
What are the features of Skeletal Muscle?
striations (horizontal lines)
syncytium (multinuclear mass of cells)
nuclei on periphery (pushed there by actin and myosin)
What are the features of Smooth Muscle?
No striations
Centrally-located nuclei
What are the features of Cardiac Muscle?
Striations
Centrally-located nuclei
Intercalated Disk (connects two cardiac muscles in sequence)
What are the functions of Nerve Tissue?
Specialized for signal transmission
Central Nervous System (Brain and Spinal Cord)
Peripheral Nervous System (ganglia and axons, [nerves])
What are the features of the brain?
- Cortex (outer portion)
- cell bodies
- gray matter
- Medulla (inner portion)
- nerve fibers (myelinated)
- white matter
What are the features of the Spinal Cord?
- Gray Matter (medulla)
- dorsal horn
- ventral horn
- Central canal (spinal fluid)
- White matter (cortex)
- Meninges (specialized connective tissue)
What are the features of Peripheral Nervous Tissue?
Axons (nerve fibers)
Schwann cells (make myelin sheath)
Fibroblasts
CCT
What are the functions of connective tissue?
- Primarily structural
- often the stroma of organs
- parenchyma is the functional tissue
- includes cushioning CT found almost everywhere
- cells organized in special extracellular matrix
- classified based on ECM, not cells
What are the properties of Connective Tissue?
- Cells
- mostly fibroblasts and immune cells
- other specialized cells for specific functions
- Collagen (or collagen-based) fibers in a matrix
- Matrix contains carbohydrate-based protein complexes that retain water
- absorb force
- maintain shape
What are the types of connective tissue?
- Embryonic
- mesenchymal or mucous
- Adult
- CT proper (collagenous/elastic)
- Specialized
What are the features of proper adult CT (collagenous/elastic)?
Loose
dense irregular
dense regular
reticular (not elastic)
What are the features of specialized adult CT?
supporting (bond/cartilage)
adipose
blood
How does the epithelium function for protection?
Skin
has water barrier
protects from mechanical abrasion, chemicals, bacteria, etc.
What characteristics help epithelium act as a barrier?
Avascular
Free surface
CT associated with epithelium for supports is vascular
How can epithelium acting as a barrier vary?
- specific transport vs. diffusion
- single layer vs. multiple layers
- moist vs. dry
Define: Apical
faces the free surface (head)
Define: Basal
the bottom (feet)
Define: Lateral
the sides
Is epithelium polar or nonpolar? why?
Epithelial cells are polar because their ends are different (one end is apical, the other is basal)
What are the functions of squamous epithelium?
allows diffusion and transport across the membrane
What are the functions of cuboidal cells?
act as a lining
some absorption and secretion
What are the functions of columnar cells?
specialized excretion and absorption
Define: Simple
one layer
Define: Stratified
multiple layers
name based on top layer
What are the two exceptions to cell type naming?
Pseudostratified
Transitional
Define: Pseudostartified
one layer, looks like 2+
cells look like they are in different layers but are on the same surface
columnar cells are next to basal cells not above or below
basal cells
Define: transitional
stretches
cells can slide past one another making it look stratified
cells change shape depending on if it is stretched or not
umbrella (domed) cells
in urinary tract
Define: Basement Membrane
- Separates epithelium from underlying CT
- Matrix of proteins and carbohydrates
- Basal lamina
- epithelially-derived
- Lamina reticularis
- CT-derived
What are the functions of the basement membrane?
- Structural Support
- framework for cells to attach
- Molecular Filter
- additional barrier
- Regulate migration of cells
- immune cells → send out to epithelial cells
- Regeneration (wound healing)
- Regulation and signaling
What are Apical Modifications?
Found on the free surface
used in nomenclature
strong functional relevance
What are the three types of apical modifications?
Cilia (movement)
Microvilli (surface area)
Stereocilia (sensory)
Define: Cilia
microtubule core
surrounded by plasma membrane
developed from basal bodies
9+2 arrangement
wispy structures
move material along the apical surface
Define: Microvilli
actin core
anchor to terminal web (web of actin)
increase surface area of cell
tight
brush border
Define: Stereocilia
actin core
long and branched
tend to clump
thin
used for detection with receptors
What are Cell-Cell Junctions?
found in many tissue types
prominent and important in epithelial tissue b/c of its barrier function
attach and anchor cells (lateral/basal surface)
seal adjacent cell membranes
form channels between cells
support the barrier function of cells
How are Cell-Cell Junctions seen in Light Microscopy?
not well
around the entire cell
terminal bar
How are Cell-Cell Junctions seen on electron microscopy?
- Higher resolution
- Able to see:
- Zonula occuldens (line)
- Zonula adherens (line)
- Macula adherens (spots)
Define: tight Junctions
* define cell polarity
- control the passage of substances between adjacent cells
- have a belt like distribution like a ribbon internally bracing the cells and are associated with actin filaments
Define: Zonula adherens/belt Desmosomes
Anchoring junction has a beltlike distribution and is associated with actin filaments
Define: Macula adherens/spot desmosome
Anchoring junction has a spotlike distribution and is associated with intermediate filaments
Define: Hemidesmosome
link the basal domain of an epithelial cell to the basal lamina
intermediate filaments are associated with a plaque
Define: Gap/communicating junctions
Connect functionally two adjacent cells
A gap junction is formed by connexons, channel-like structures that enable the passage of small molecules (~1.3 kd) between cells
What are zonula occludens?
- tight junctions
- most apical
- helps maintain cell polarity
- intracellular diffusion barrier
- stops things from migrating between cells
- involved in intracellular signaling
What are PDZ Domain Proteins?
recognize internal elements of junctions to initiate cell signaling pathways
What is the ZO-1 protein?
tumor suppressor
What is the ZO-2 protein?
epidermal GF signaling
what is the ZO-1,3 proteins?
attach to actin
mediate actin binding
Define: Anchoring Junctions
Include Zonula Adherens and Macula Adherens (desmosomes)
Mechanical stability by linking cytoskeleton of neighboring cells
Found laterally and basally
Structural integrity of epithelium
participate in intra- and intercellular signalling
Define: Cadherins
anchoring proteins
calcium-dependent transmembrane proteins
bind microfilaments through catenins
maintain epithelial continuity
main adhesion proteins holding epithelial cells together in a sheet arrangement
the removal of calcium disrupts tissue cohesiveness
Define: Integrins
- Consist of two subunits
- have dual function:
- bind to extracellular matrix
- bind to internal cytoskeleton
- not calcium dependent
Define: Gap junctions
- Lateral Surface
- Made up of connexons
- create pores between cells for communication
- create continuity between cells
- electrical (ions)
- Metabolic (glucose and other small carbons)
How is a connexon created?
six connexin monomers assemble to form a hexameric connexon
What are the features of epithelial glands?
- grow down into connective tissue
- secrete:
- lubrication
- modifiy pH
- enzymes (digestion)
- exocrine (duct) → has an exit
- endocrine (no duct) → released within tissue and usually surrounded by alot of blood vessels
Define: Exocrine gland
a gland product is released onto the surface
has an exit
Define: Endocrine gland
A gland product is released into the blood
How are glands classified?
- unicellular vs. multicellular
- duct branching
- secretory unit shape
- type of secretion
- mode of secretion
What is an example of unicellular glands?
goblet cells
mucous cup on apical surface with stem
extracellular gel containing water and glycoproteins
What is an example of multicellular glands?
sweat glands
Gland Classification: Duct Branching
Simple (no branching)
Compound (branches)
Gland Classification: Secretory Unit Shape
Tubular (tube shaped)
Acinar (ball shaped)
Tubuloacinar (ball and tube shaped)
Gland Classification: Types of Secretion
Serous (protein, water)
Mucous (Mucin/Lipid-Based)
Mixed
Gland Classification: Mode of Secretion
Merocrine
Apocrine
Holocrine
Define: Merocrine Secretion
Vesicles fuse with apical surface to excrete contents
most common
basically exocytosis
causes a net addition to plasma membrane
Define: Aprocrine Secretion
product released from apical surface is surrounded by cytoplasm and plasma membrane
vesicle is pinched off around lipid
often partners with merocrine secretion (milk production)
Define: Holocrine Secretion
Secretory cell dies, cell explodes and releases contents
whole cell is secreted
