Epithelia & supporting tissue (W2) Flashcards
What are the 4 basic tissue
- epithelial
- supporting
- muscular
- nervous
What is the function of epithelial
- containment
- selective diffusion
- absorption
- secretion
- physical protection
What is surface epithelia , where is is found and what is it involved in
- cover and line all body surface , cavities and tube
- Involved in containment, selective diffusion, absorption, secretion and physical protection
What does all surface epithelia contain
cytokeratin intermediates filaments
- makes it recognisable by immunohistochemistry
What are all epithelia supported by
Basement membrane
Describe the basement membrane
- separates epithelial from underlying supporting tissue
- doesn’t contain BV and are dependant on diffusion for nutrients jh
What is the function of the basement membrane
provide metabolic support & binds to underlying support tissue
What is the basement membrane celled in nerve and muscle tissue
external lamina
Describe the shape of the basement membrane
sheet-like arrangements of extra-cellular matrix proteins which act as interface between support tissue and parenchymal cells
What are the main constituents of the basement membrane
- collagen type 4
- glycoproteins laminin
- entactin
- fibroxnectin
What layers are the basement membrane composed of
- Lamina lucida
- Lamina densa
- Lamina fibroreticularis
Describe the 3 layers of basement membrane
- Lamina lucida
- relatively transparent - Lamina densa
- intermediate elcetron-dense layer - Lamina fibroreticularis
- electrolucent layer which emerge with supporting tissue underneath
- mainly tyope 3 collagen & fibronectin
Describe simple squamous and where it is found
- flattened irregular epithelium forming continuous surface (pavement epithelium)
- found lining surfaces f gases e.g., lungs
Describe simple cuboidal and where it is found
- round nucleus located in cell centre (gives clue to shape)
- lines small suits and excretory, secretory or absorptive functions
Describe simple columnar and where it is found
- taller cuboidal cells
- elongated nuclei an located towards the base, apex of centre of cytoplasm
- located in small intestine, gall bladder or play a secretory role
Describe simple stratified epithelia
- consisting of 2+ layers
- flattened cells at the top
- cuboidal at base
Why is stratified epithelium poor for absorption
thickness of cell layers
Describe stratified squamos and where it is found
adapted to withstand constant abrasion and desiccation due to tough non-living surface layer composed of protein keratin wrapped in plasma membrane
Why is the nuclei eventually lost in stratified epithelium
the cell matures
Describe stratified cuboidal and where it is found
- thin ( only 2 or 3 cells)
- more robust
- found lining larger excretory ducts
- not involved in significant secretory or absorptive activity
Describe stratified transitional and where it is found
- highly nucleated
- found in urinary tract and is highly specialised to accommodate stretch and toxicity of urine
What does stratified transitional look like when
- relaxed
- stretched
- when relaxed, surface cells are large and rounded
- when stretched, intermediate and surface layers are extremely flattered
What is glandular epithelium
- primarily involved in secretion
Describe simple tubular glands and where they are located
- single straight tubular lumen which secretary products are discharged
- large intestine
Describe simple coiled tubular glands and where they are located
- tightly coiled in 3D
- sweat glands
Describe simple branched glands and where they are located
- several tubular secretory portions which converge onto a single unbranched duct
- stomach mucus
When do endocrine glands lose their connection to the epithelial surface
during development
How can secretion be controlled
by metabolic factors
e.g., glucose
What do most endocrine glands contain
clusters of secretary cells each with own basement membrane surrounded by rich network of blood vessels
What is supporting tissue
provides structural and metabolic support for other tissues and organs
What are supporting tissue derived from
precursor cells in primitive (metal) supporting tissue - mesenchyme
What is the function of supporting tissue
mediates exchange of nutrients, gases and metabolites between tissues and circulatory system
What is supporting tissue composed of
- specialised cells
- extracellular matrix (ground substance and fibres)
What determines the physical properties of the supporting tissue
extracellular matrix component
What are the 2 main fibrous components of supporting tissue
- collagen
- elastin
Describe collagen
- provides tensile strength
- secreted as tropocollagen which polymerises in the extracellular matrix to from collagen
What are the main types of collagen and where are they found
- Type 1 - found in dermis, tendons, ligaments, bone and fibrous supporting tissue
- Type 2 - found in hyaline cartilage
- Type 3 (reticulin) - delicate branching supporting meshwork in highly cellular tissues e.g, liver bone and lymphoid organs
- Type 4 - mesh-like structure in basement membrane
- Type 7 - anchors fibrils that link to the basement membrane
Name some examples of mesenchyme
- fibroblast (most come cells) - responsible for secreting extracellular matrix
- my-fibroblasts - contractile function + secretion of extracellular matrix
What is primitive mesenchyme
embryonic tissue which all connective tissue is derived from
Describe the shape of mesenchymal cells
- stellate shape with delicate branching cytoplasmic extensions
- oval nuclei
What are mature fibroblastas
maintain the integrity of tissue by slow turnover of the extracellular matrix constituents
Describe the shape of mature fibroblasts
- condensed elongated in the direction of the collagen bundles
What is adipose tissue and where is is found
- fat storage
- found in isolation or clumps in tissue
Why does adipose tissue have a rich blood supply
to release energy
What is the function of adipose tissue
releasing several proteins
What is brown adipose
- highly specalised tissue found in newborns
- importnat role in temperature regulation
- arrnaged in lobules seperated by fibrous septae which convey blood vessels and nerves
What is white adipose
- thermal insulator and a cushion against mechinal shock in sites