Histology Flashcards
Components of Cell
75-85% Water 10-20% Protein 2-3% Lipid 1% Carbohydrate 1% Inorganic
What cells have most water?
Embryonic
Features common to all eukaryotic cells
an outer membrane,
inner cytosol,
cytoskeleton ,
organelles ,inclusions
Role of plasmalemma
separates cytoplasm from the outer environment
Whats is the plasmalemma made up of?
amphipathic phospholipid molecules
what does the plasmalemma contain?
integral proteins
examples of integral proteins
receptors, channels, transporters, enzymes and cell attachment proteins
What can the plasmalemma do
exocytose and endocytose
What is the plasmalemma permeability like?
highly permeable to H20, O2 and small hydrophobic molecules whereas charged ions are virtually impermeable
why is a bi layer important
because both inside the cytoplasm and outside the cell are water loving environments and so hydrophilic head must face both
organelles
small ‘organs’ of the cell that have a specific function and are essential for life
examples of organelles
mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi apparatus, lysosomes and nucleus
inclusions
are there for specific purposes but are not necessary for life
example of inclusion
adipose cells in brown fat
what is the cytoskeleton made up of?
filamentous proteins
3 main filaments
microfilaments, intermediate filaments and microtubules
how do filaments become attached to the cell membrane
by anchoring and joining proteins to form a dynamic 3D internal scaffolding in the cell
What are microfilaments composed of
fine brands of protein actin
what makes microfilaments dynamic cytoskeletal elements?
they can assemble into filaments and later dissociate
how small are microfilaments
smallest filament (7nm)
what do intermediate filaments do?
bind intracellular elements together and to plasmalemma
size of intermediate filaments
10-15nm
why are intermediate filaments subdivided into classes?
these are used in pathology to identify tumour origins
what do intermediate filaments form?
a network through out the cytoplasm
what do microtubules consist of?
they are hollow tubules composed of alpha and beta tubular subunits
where do microtubules originate from?
the centrosome
What is the role of microtubules?
participate in production of spindle and proteins such as dyeing and kinesis attach to microtubules and move vesicles by dragging them along the microtubules
Kinesin
ATPase that moves towards the cell periphery
Dynein
ATPase that moves toward the cell centre
How is the nucleus structures?
it is surrounded by a nuclear envelope which is composed of an inner and outer nuclear membrane with nuclear pores, between the two membranes there’s the perinuclear cistern which is continuous with the cistern of the ER and the outer membrane is studded with ribosomes and continuous with the rough ER
Function of nucleus
location of RNA synthesis, mRNA and tRNA are transcribed in nucleus, rRNA is transcribed in the nucleolus
What does the nucleus contain
Euchromatin and heterochromatin
Euchromatin
DNA that is more dispersed and is actively undergoing transcription
heterochromatin
DNA that is highly condensed and not undergoing transcription
what is the nucleus surrounded by
double membrane
where are ribosomes formed
the nucleolus
what are ribosomes made up of
small subunit (which binds RNA) and a large subunit (which catalyses the formation of peptide bonds.
What does the export of ribosome depend on?
the nuclear pore complex
What does the ER form
a network of interconnecting membrane bound compartments in the cell
how does the ER look in micrographs
appears as flattened membrane sheets or elongated tubular profiles
What does the RER do?
Site of protein synthesis and initiation of glycoprotein formation
What is expected if you see lots of RER?
there will be lots of protein production
What does SER do?
produces lipids and continues protein synthesis
What is the Golgi apparatus made up of?
made up of flattened, membrane bound cisternae which are arranged in sub compartments
What arrives at the Golgi apparatus?
transport vesicles from the RER/SER
What does Golgi apparatus do?
functions in the modification and packaging of macromolecules that were synthesised in the ER
What is the mitochondria composed of
an outer membrane and an extensively folded inner membrane folded to form cristae
Role of mitochondria
generate ATP via oxidative phosphorylation and involved in synthesis of certain lipids
How do mitochondria synthesis proteins?
they contain their own DNA and system
What are intercellular junctions
specialised membrane structures which link individual cells together into a functional unit
The three types of junctions
Occluding, Anchoring and communicating junctions
Anchoring/adherent junctions
link submemnrane actin bundles of adjacent cells
communicating junctions (gap junctions)
allow selective diffusion of molecules between adjacent cells
intercellular junctions (junctional complex)
a close association of several types of junctions found in certain epithelial tissues
How can things be transported in and out of the cell?
diffusion, transport proteins and by incorporation into vesicles
Endocytosis and exocytosis
material from extracellular space can be incorporated into the cell by endocytosis. The cell membrane invaginate, fuses and newly made endocytotic vesicle buds into the cell. Exocytosis works in a reverse fashion to discharge material
How is tissue prepared to watch under a microscope?
- Tissue placed in a fixative (formalin), preserves in in a life like state
- Tissue is dehydrated, put in organic solvent and placed in hot wax until it has fully penetrated/impregnated the tissue.
- tissue is thinly sliced (1-15µm) using a microtome to allow light to pass through
- placed on microscope slides, wax is washed out and tissue is rehydrates
- this can produce ARTIFACTS (distortions/changes from original tissue e.g. shrinkage)
most common stain
H and E
Haematoxylin
basic dye that has an affinity for acidic molecules and stains them purplish blue
Eosin
an acidic dye that has an affinity for basic molecules and stains them pinkish red
Why are epithelial cells good for covering surfaces?
because they have strong adhesion between them meaning they’re tightly bound and have little intercellular space
How do epithelial cells receive nutrients?
they are non vascular, so nutrients must diffuse across the the basal lamina
what can epithelia also form?
solid organs and glands
shapes of epithelia
squamous, cuboidal and columnar
simple
has one layer of epithelia
stratified
has two or more layers of epithelia
pseudostratified
multiple layers of epithelia
specialised cells
goblet cells
what are glands
where product is secreted
exocrine glands
product secreted toward apical end of the cell either into the lumen of an internal space, into a duct, or onto the body surface
endocrine glands
product secreted toward the basal end of the cell (end sitting on basal lamina), then distributed by the vascular system throughout the body. Termed ‘ductless’ glands