HISTOLOGY Flashcards
plasmalemma
separates the cytosol from the outer environment.
bimolecular layer of amphiphatic phospholipid molecules with hydrophilic heads at the outer and inner surfaces and their hydrophobic fatty acid chains facing between the two layers of hydrophilic heads
amphiphatic
contains both hydrophilic and hydrophobic parts
plasmalemma has which integral proteins inserted by the cell?
transporter proteins, channel proteins, receptors, enzymes and cell attachment proteins
selectively permeable
allows water, oxygen and small hydrophobic molecules in easily, and is virtually impenetrable to ions
organelles
small intracellular ‘organs’ with a specific function and structural organisation. essential to life.
examples of organelles
mitochondria, RER, SER, golgi apparatus, lysosomes, nucleus
inclusions
dispensable and may only be present as transients
cytoskeleton
provides structural integrity to the cell, made of microfilaments (composed of actin protein), intermediate filaments (composed of 6 main proteins), microtubules (composed of 2 microtubule proteins)
microfilaments
actin molecules can assemble into filaments and then dissociate, therefore the filament is very dynamic (not permanent)
intermediate filaments
different cells express different intermediate proteins, so can be use in pathology to identify tumours
microtubules
hollow tubule composed of two alternating alpha and beta subunits of tubulin. originate from a centromere. include stabilising proteins - microtubule associated proteins (MAP). act as the motor way of the cell. kinesin and dynein attach to the microtubule and associate with membranes of organelles and vesicles, dragging them along. both ATPases, kinesin move towards the periphery, dynein moves towards the cell centre
nucleus
enclosed in a nuclear envelope, consisting of an inner and outer nuclear membrane, with nuclear pores providing continuity with the cytoplasm. the perinuclear cistern is continuous with the cistern of the ER.
euchromatin
dna that is more dispersed and is actively undergoing transcription
heterochromatin
dna that is highly condensed and not undergoing transcription
RER
studded with ribosomes. vital role in protein synthesis. the more metabolically active a cell, the more ribosomes on the RER
SER
continues the processing of proteins produced in RER. vital role in synthesising lipids. steroid hormone synthesising cells have lots of SER.
golgi apparatus
series of flattened, membrane bound cisternae. transport vesicles arrive from the RER/SER. golgi cisterns function in the modification and packaging of macromolecules that were synthesised in the ER. adds sugars, cleaves proteins and sorts macromolecules into vesicles.
mitochondria
powerhouse of the cell. outer and inner membrane. the inner membrane is invaginated to form cristae, which increases surface area. mitochondrial dna comes from your mother. cells with many mitochonrdia are metabolically active.
intracellular junctions
ways in which cells connect with each other. prominent in epithelia. occluding junctions, anchoring junctions, desmosomes, communicating junctions
occluding junctions
prevents diffusion, appear as focal region of close opposition between adjacent cell membranes (zona adherens)
anchoring junctions
adherent - link submembrane actin bundles of adjacent cells (zona adherens)
desmosomes
link submembrane intermediate filaments, very powerful (macula adherens), very common in skin where they provide mechanical stability
communicating junctions
allows selective diffusion of molecules between adjacent cells (gap junctions). each junction is a circular patch studded with hundreds of pores made of connexon proteins
types of epithelium (7)
simple squamous, stratified squamous, simple cuboidal, stratified cuboidal, simple columnar, pseudostratified columnar, transitional
connective tissue
forms the framework of the body, but has a dynamic role in development, growth and homeostasis of tissues, and, via fat, in energy store
soft connective tissues
tendons, ligaments, mesentery, dermis of skin
hard connective tissues
cartilage and bone
connective tissue consists of…
an extracellular matrix (lots of space between cells and relatively small numbers of cells) and cells
extracellular matrix
fibres, ground substance and tissue fluid
cells
fibroblasts (active cells produce and maintain cellular matrix), adipose cells, osteocytes and chondrocytes
3 things soft tissue can be divided into
loose, dense regular, dense irregular
loose (soft connective tissue)
loosely packed fibres surround by abundant ground substance
dense regular (soft connective tissue)
densely packed bundles of collagen fibres, fibres all aligned
dense irregular (soft connective tissue)
densely packed bundles of collagen fibres, run in many directions (skin)
smooth muscle
simplest, no striations, individual fibres are elongated, spindle cells with cigar shaped nucleus in the centre
skeletal muscle
voluntary, striated muscle, responsible for conscious control. giant multinucleated at the peripheral of the cell at the sarcolemma, cylindrical cells
cardiac muscle
forms major part of walls of the chambers of the heart and the origin of the great vessels. less prominent striating than skeletal muscles. single nucleus in the centre. intercalated discs are the end to end attachment
nervous tissue consists of…
neurons and their supporting cells (glia). glia outnumber neurons 10:1. surrounded by a connective tisseu coat: meninges (CNS), epineurium (PNS)
astrocytes
support, ion transport, induce blood brain barrier
oligodendrocytes
produce myelin in the brain and spinal cord
microglia
provide immune surveillane
schwann cells
produce myelin and support axons in the PNS
blood vessels inner layer
tunica intima - simple squamous epithelium (endothelium). supported by basal lamina and thin layer of connective tissue. separated from tunica media by internal elastic membrane
blood vessels middle layer
tunica media - predominantly smooth muscle. thickness varies depending on vessel type. separated from tunica adventitia by external elastic membrane
blood vessels outer layer
tunica adventitia - supporting connective tissue
aorta
lots of smooth muscle replaced with elastic fibres in tunica media for elastic recoil. this means the blood pressure doesn’t skyrocket every time the left ventricle ejects a bolus of blood
