Histology Flashcards
what is the Plasmalemma?
- separates the cytosol from the outer environment
- bimolecular layer of amphiphatic phospholipid molecules
- hydrophilic heads at the outer and inner surfaces and hydrophobic fatty acid chains facing in between
what does Amphiphatic mean?
contains both hydrophilic and hydrophobic parts
what is the membrane selectively permeable to?
allows water, oxygen and small hydrophobic molecules in easily, and is virtually impenetrable to ions
what proteins are inserted in the membrane?
integral proteins inserted by the cell
- transporter proteins, channel proteins, receptors, enzymes and cell attachment proteins.
what is the function of the cytoskeleton?
provides structural integrity to the cell
what are microfilaments?
- composed of actin protein
- actin molecules can assemble into filaments and then dissociate, therefore the filament is very dynamic (not permanent).
what are Intermediate filaments?
- composed of 6 main proteins
- different cells express different intermediate proteins, so can be used in pathology to identify tumour origins.
what are microtubules?
- hollow tubule composed of two alternating alpha and beta subunits of tubulin
- Originate from a centromere
- Include microtubule associated proteins (MAP)
- Act as the motor way of the cell
- Kinesin and dynein attach to the microtubule and associated with membranes of organelles and vesicles, dragging them along
- Both ATPases, kinesin moves towards the periphery, dynein moves towards the cell centre.
what is the 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.
what is Euchromatin?
DNA that is more dispersed and is actively undergoing transcription.
what is Heterochromatin?
DNA that is highly condensed and not undergoing transcription
what is the RER?
studded with ribosomes. Vital role in protein synthesis. The more metabolically active a cell, the more ribosomes on the RER.
what is the SER?
continues the processing of proteins produced in RER. vital role in synthesising lipids
Steroid hormone synthesising cells have lots of SER
what is the 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.
what is the 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 mitochondria are metabolically active.
where are intercellular junctions prominent?
epithelia
. Occluding junctions
prevents diffusion, appear as a focal region of close opposition between adjacent cell membranes (zona occludens).
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
Cardiac muscle - important for spread of electrical excitation.
what are the different types of epithelium?
simple squamous
simple cuboidal
simple columnar
stratified squamous
stratified cuboidal
pseudostratified columnar transitional
Connective Tissue
Forms the framework of the body, but has dynamic role in development, growth and homeostasis of tissues, and, via fat, in energy store
Extracellular matrix - lots of space between cells and relatively small numbers of cells
Extracellular matrix - fibres, ground substance and tissue fluid
Cells - fibroblasts (active cells produce and maintain cellular matrix), adipose cells, osteocytes, chondrocytes.
what are the two types of connective tissue?
Soft and hard
Soft Connective Tissue
Soft - tendons, ligaments, mesentery, dermis of skin.
Loose - loosely packed fibres surrounded by abundant ground substance.
Dense regular - densely packed bundles of collagen fibres, fibres all aligned.
Dense irregular - densely packed bundles of collagen fibres, run in many directions (skin).
hard connective tissue
cartilage and bone.
Smooth muscle
simplest, no striations, individual fibres are elongated, spindle shaped 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.
what does nervous tissue consist of?
neurones and their supporting cells (glia)
Glia outnumber neurones 10:1
Surrounded by a connective tissue coat:
meninges (CNS)
epineurium (PNS).
astrocytes, oligodendrocytes, microglia, schwaann cells
Astrocytes
support, ion transport, induce blood brain barrier.
Oligodendrocytes
produce myelin in the brain and spinal cord.
Microglia
provide immune surveillance
Schwann cells
produce myelin and support axons in the PNS.
what are the 3 layers of the blood vessels?
Inner layer: tunica intima
Middle layer: tunica media
Outer layer: tunica adventitia
what does the tunica intima consist of?
simple squamous epithelium (endothelium). Supported by basal lamina and thin layer of connective tissue. Separated from tunica media by internal elastic membrane.
what does the tunica media consist of?
predominantly smooth muscle
Thickness varies depending of vessel type
Separated from tunica adventitia by external elastic membrane.
what does the tunica adventitia consist of?
supporting connective tissue.
what does the aorta consist of?
lots of smooth muscle replaced with elastic fibres in tunica media for elastic recoil
This means the blood pressure doesn’t skyrocket everytime the left ventricle ejects a bolus of blood.
