Building tissues from cells Flashcards
Definition of a tissue
Collections of similar cells and material surrounding them
Definition of histology
Microscopic study of tissues
Definition of exocrine
Secrete to free surface
Definition of endocrine
Secrete to blood stream
Major types of adult tissues
Epithelial
Connective
Muscle
Nervous
Characteristics of epithelial tissue
Exist as sheets Cover body surface Line almost all internal cavities Rests on basement membrane Depend on diffusion for nutrients, no blood vessels in BM
Structure of epithelial tissue
Epithelium Connective tissue Circular fibre Longitudinal fibre Connective tissue Epithelium
Importance of basement membrane
ECM made of T4 collagen
Secrete proteins and bind to them
Membrane can have varying thickness, can act as a filter
Classification of epithelial tissue
Cell shape
Layer structure
Surface specialization
Location and function
Cell shapes
Squamous
Cuboidal
Columnar
Layer structure
Simple
Pseudostratified
Stratified
Surface specialisation
Ciliated
Microvilli
Keratinized
Location and function
Respiratory, ciliated columnar PS w goblet cell
Transitional, only in urinary, stratified, squamous, cuboidal
Location of glands and types
Almost all originate as invaginations of epithelium, retain epithelial organisation
Endocrine and exocrine
Formation of endocrine glands
Solid epithelial growth, does not break through BM, migrates
Epithelial cells move into mesenchyme, surrounded by BM
Forms cords of glandular cells, trap blood capillary
Formation of exocrine glands
Solid epithelial growth into mesenchyme, does not break through BM,
Form secretory cells, excretory duct and surrounded by blood capillaries
Types of exocrine glands
Simple tubular Simple coiled tubular Simple branched tubular Simple acinar Simple branched acinar Compound branched tubular Compound acinar Compound tubule-acinar
Types of exocrine secretion mechanism
Merocrine
Apocrine
Holocrine
How do merocrine glands work
Vesicles open onto cell syrface
Secretory product discharged from cell in exocytosis
How do apocrine glands work
Some apical cytoplasm lost with secretory products
Sweat, mammary, prostate
How do holocrine glands work
Breakdown and discharge of entire secretory cell
Cell junctions and function
Keeps epithelial sheets tightly bond
Anchor junctions
Allows functional integrity of cells selective barriers/communication
Name of junctions in the epithelial cells
Tight junctions Adherens junctions Desmosomes Gap junctions Hemidesmosomes
Function and properties of desmosomes and hemidesmosomes
Both attached to intermediate filaments
Anchored allow for flexing of cell sheets, prevent cells from being ripped apart/from underlying tissue
Adjacent cells joined by adhesion proteins (desmoglein, desmocolin)
Only attach like to like
Function and properties of adherents junction
Links 1 cell to another with different adhesion proteins (cadherin)
Anchor proteins attach to actin filaments
Actin creates rigid structures, hold columnar cells upright
Types on non anchoring junctions
Tight, occludent barrier junction
Gap, selective communication between cells
Function and properties of tight junctions
Bring 2 cells so close together that nothing can pass between them Prevents substances (glucose) from diffusing back out into gut lumen, homeostasis Adhesion proteins (claudia and occluding) bind like to like
Function and properties of gap junctions
Allow molecules to freely move between adjacent cells
Has many channels made up of connexion proteins
All channels closed, prevent cytoplasm from leaking out, only open when 2 like channels meet
Allows ions, glucose, AA and O2 through
Allows for equilibration of substances via osmosis
In embryo, allow diffusion of Ca2+ to adjacent cells to trigger Ca2+ production in adjacent cell
