cell differentiation
cell
specialization
• multicellularity
• probably evolved many times
• provides opportunity of specialization of cells
• a step above colonial organization
• cells perform special functions
• differentiation of cells
• stem cells (pluripotent)
• defined by pattern of regulated gene expression
plant cell types
plant cell types
• parenchyma
• relatively less differentiated cells
• thin cell walls
• large tonoplast
• collenchyma
• unevenly thickened cell walls
• used for support
• celery
plant cell types
plant cell specialization
• sclerenchyma
• lignified secondary cell walls
• fibers or sclereids (stone cells)
• dead when functionally mature
• plant tissues
• dermal
• root hairs
• guard cells
• vascular
• xylem
• phloem
• ground
• meristem
root hairs (trichomes)
guard cells and stomata
• epidermis
• atrichoblasts
• trichoblasts
• nucleus moves into root
• guard cells
• microtubules
• synthesis of cellulose
• cell walls of variable thickness
• dorsal wall thinner than ventral wall
• radial arrangement of microfibrils
hormone
abscissic acid causes K+ to rush out
•
hair tip
• actin filaments
• growth
• dense mesh of filaments
at tip
• dynamic microtubules
• nucleus associated MTs
• involved in directionality
of root hair growth
of cell
• loss of turgor pressure
animal cell specialization
animal cell specialization
• amoebocytes
• archaeocytes - sponges
• hemocytes - arthropods
• represent a variety of cells in
• cnidocytes
• nematocyst
• stylets
• thread
• cnidocil
• trigger
different organisms
pulling fluid into tubules
integument cells
• flame cells
• protonephridia
• rotifers, flatworms, some annelids
• solenocytes
• protonephridia
• priapulida, gastrotrichs
• syncytial tegument
• Platyhelminthes -
Nucleus
of cap cell
Cilia
Interstitial
fluid flow
Tubule cell
flatworms
• tegument
• Nemata - roundworms
• hypodermis
spine
distal
cytoplasm
muscle
internuncial
process
golgi
• generates collagenous
cuticle
nucleus
tegument
cell body
Flame
bulb
Opening in
body wall
mitochondrion
nematode
body wall
parenchymal
cell
Tubule
Tubules of
protonephridia
trematode body wall
pigment cells
• chromatophores
• large cells with branching
processes
• arthropods, cephalopods,
reptiles, amphibians, fish
• melanophores
• xanthophores
• iridophores / guanocytes
animal cell specialization
• hair cells
• neuromast cells
• lateral line system
stereocilia
of hair cell
bone cells (vertebrates)
• osteoblasts (osteocytes)
• connected by tight junctions
• connected to each other via filopodia (canaliculi)
• gap junctions
• lacunae
• Haversian canal
• blood vessels
• nerves