Histology Flashcards
Why do you study microscopic anatomy?
to allow you to assess and understand pathological changes that affect your patient
which cells contains the most water?
embryonic cells
what are features that are common in all eukaryotic cells?
an outer membrane, an inner cytosol, a cytoskeleton, membrane bound organelles in the cytosol, inclusion
what is an inner cytosol in a cell?
a solution of proteins, electrolytes & carbohydrates. both fluid and gel like properties.
what is a cytoskeleton of a cell?
determines the shape and fluidity of the cell, made from thin and intermediate filaments and microtubules
what are inclusion?
structures in the cytoplasm, that can be bound to the membrane. they have been synthesised by the cell itself or taken up from the extracellular environment. they are dispensable
what is the plasmalemma?
separates the cytoplasm from the outside environment. bimolecular layer of amphipathic phospholipid molecules with their hydrophilic heads at the outer and inner surfaces and their hydrophobic fatty acid chains facing towards the middle of the two layers
where do the integral proteins insert themselves into?
the cell membrane within the plasmalemma
what are examples of integral proteins?
receptors, channels, transporters, enzymes and cell attachment proteins.
what is exocytose?
cellular secretion
what is endocytose?
when substances are brought into the cell
what does is mean by the membrane is fluid?
can change shape easily, membrane proteins can diffuse laterally, but many are anchored, therefore many proteins are not distributed equally in the membrane
what does is mean when a membrane is selectively permeable?
highly permeable to: water, oxygen, small hydrophobic molecules. virtually impermeable to charged ions
what provides a selective structural barrier to the cell?
the plasmalemma
what does the phospholipid bilayer contain?
integral and peripheral proteins and cholesterol imbedded
what are organelles?
small intracellular organs with a specific function and structural organisation
what are the functions of the cell maintained by?
set of filamentous cytosolic proteins, the cytoskeletal proteins
what are the three classes of filaments?
microfilament - composed of the protein actin
intermediate filaments - composed of 6 main proteins, which vary in different cell types
microtubules - composed of 2 tubulin proteins
how do filament proteins become attached to the cell membrane and each other?
by anchoring and joining proteins to form a dynamic 3D internal scaffolding in the cell. they form a network throughout the cytoplasm
what are microfilaments (MF)?
globular actin polymerises to form filamentous actin, actin molecules can assemble into filaments and then dissociate, making them dynamic cytoskeletal elements. often accumulate under the cell membrane
what are intermediate filaments?
they bind intracellular elements together and to the plasmalemma. so many types that are then divided up into classes which are then used in pathology to identify tumour origins
what are microtubules?
hollow tubule composed of two types of tubulin subunits, alpha and beta in an alternating array. they can be assembles and disassembled. originate from centrosome. include stabilising proteins.
what are stabilising proteins?
microtubule associated proteins (MAPs), important in cilia, flagella and the mitotic spindle
what serves as the motorway network of the cell?
microtubules - two proteins, dyne and kinesis attach to the microtubules and move along them. they associate with the membranes of the organelles and vesicles and drag them along the microtubule.
what is kinase?
an ATPase that moves toward the cell periphery
what is dynein?
an ATPase that moves toward the cell centre
what is the nucleus enclosed by?
the nuclear envelope
what is the nuclear envelope composed of?
an inner and outer nuclear membrane with pores providing continuity with the cytoplasm.
what is the perinuclear cistern?
found between the two sheets of the nuclear envelope and is continuous with the cytoplasmic RER
what is the nucleus?
the location of RNA synthesis
where are mRNA and tRNA transcribed?
in the nucleolus, a dense area within the nucleus
what does the nucleus contain?
chromosomes, Euchromatin (DNA that’s dispersed and actively undergoing transcription), heterochromatin (DNA that’s highly condensed and not undergoing transcription)
True or false, the nucleus is surrounding by a single nuclear membrane?
False - a double nuclear membrane
where are ribosomes formed?
the nucleus
what does the export of ribosomes depend on?
the nuclear pore complex
what do the subunits of a ribosome do?
small subunit binds RNA and large subunit catalyses the formation of peptide bonds
what does the endoplasmic reticulum form?
a network of interconnecting membrane-bound compartments in the cell
what is the RER studded with?
ribosomes
what is the amount of ER in a cell dependent on?
how active a cell is
where do proteins that are unpackaged in the cytosol get synthesised?
on polysomes, floating free in the cytosol
what is RER associated with?
protein synthesis and initiation of glycoprotein formation
what does SER do?
continue the processing of proteins produced in the RER, plays a vital role as the site of synthesis lipids.
what is the Golgi apparatus/complex?
composed of a group of flattened, membrane bound cisternae, arranged in sub-compartments
what are the sub-compartments of the Golgi apparatus?
transport vesicles that arrive in the Golgi from the RER/SER, Golgi cisterns function in the modification and packaging of macramolecules that were synthesised in the ER, e.g adds sugar, cleaves some proteins, sorts macramolecules into vesicles
what are macramolecules?
many monomers linking together, forming a polymer, e.g. lipids
what are mitochondria?
the power generators of the cell, function in the generation of ATP, via oxidative phosphorylation and the synthesis of certain lipids and proteins
what is the shape of mitochondria?
oblong and cylindrical
what are mitochondria composed of?
an outer and inner membrane. the inner membrane is extensively folded to form cristae, which act to increase the available surface area
True or false mitochondria contain their own DNA and system for protein production?
true
what are intercellular junctions?
specialised membrane structures which link individual cells together into a functional unit. particularly in epithelia
what are the three types of intercellular junctions?
occluding junctions - link cells to form a diffusion barrier
anchoring junctions - provide mechanical strength
communicating junctions - allow movement of molecules between cells
what does an occluding junction do?
prevent diffusion, links cells to form a diffusion barrier, , appear as a focal region of close apposition between adjacent cell membranes
what are occluding junctions also known as?
tight junctions or zonula occludens
what do anchoring junctions do?
link submembrane actin bundles or adjacent cells, transmembrane cadherin molecules bind to each other in the extracellular space and through link molecules, to actin of the cytoskeleton. desmosomes: link submenbrane intermediate filaments of adjacent cells. also called macula adherent. desmosomes are very common in the skin providing mechanical stability
what are anchoring junctions also known as?
adherent junctions or zonula adherent
what do communicating junctions do?
allow selective diffusion of molecules between adjacent cells, each junction is a circular patch studded with several hundred pores. pores are produced by connexon proteins. found in epithelia but also in smooth muscle and in cardiac muscle, where it is critical for the spread of excitation
what are communicating junctions also known as?
gap junctions
what is a junctional complex?
close association of several types of junctions found in certain epithelial tissues.
ZO: zonual occulens
ZA: zonula adherens
MA: macula adherens
how is material transported via diffusion?
via transport proteins (pumps or channels) by incorporation into vesicles (vesicular transport)
what are two types of vesicular transport?
endocytosis and phagocytosis
what is endocytosis?
material from extracellular space can be incorporated into the cell by endophytes. the cell membrane invaginates, fuses and the newly made endocytotic vesicle (endosome) buds into the cell. this process is often receptor mediated. exocytosis works in a reverse fashion, to discharge
what is phagocytosis?
bacteria or larger particulate material from the extracellular space can be incorporated into the cell by phagocytosis. the bacterium binds to the cell surface receptors triggering extensions of the cell to engulf it forming a phagosome. the phagosome binds with a lysosome carrying digestive enzymes producing a phagolysosomes
why is tissue fixed?
to preserve it in a life-like as state as possible
how does a tissue have to be sliced to allow light to penetrate the tissue?
thinly
what support material is commonly used to impregnate issue with when analysing it?
wax
how is the tissue penetrated by the support material in order for it to be analysed?
dehydrated, put into organic solvent and placed into hot wax until the tissue is fully penetrated. thin sections are then cut by a microtome, the wax is washed off and the tissue is rehydrated.
what are artefacts in tissues in the context of being analysed?
distortions made from the process of preparing the tissue before analysis, e.g. shrinkage
how do stains work?
different stains bind to particular types of molecules, allowing molecules to be differentiated from each other and identified
what does H&E stand for
haematoxylin (basic dye with an affinity for acidic molecules) and eosin (acidic dye with an affinity for basic molecules)
what are the 4 basic tissue types?
epithelium, connective tissue, muscle and nervous tissue