- Providing structural support to the cell, the cytoskeleton also functions in cell motility and regulation
- The cytoskeleton is a network of fibers extending throughout the cytoplasm.
- The cytoskeleton organizes the structures and activities of the cell.
MICROFILAMENTS THICKENS THE CORTEX AROUND THE
INNER EDGE OF THE CELL JUST LIKE RUBBER BANDS
THEY RESIST TENSION
MICROTUBULES – ARE FOUND IN THE INTERIOR OF THE
CELL WHERE THEY MAINTAIN CELL SHAPE BY RESISTING
COMPRESSIVE FORCES
INTERMEDIATE FILAMENTS ARE FOUND THROUGHOUT
THE CELL AND HOLD ORGANELLES IN PLACE
The cytoskeleton also plays a major role in cell
motility.
This involves both changes in cell location and limited movements of parts of the cell.
The cytoskeleton interacts with motor proteins.
This is also true in muscle cells.
MICROTUBULES, small hollow rods about 25 nm in
diameter.
Microtubule fibers are constructed of the globular protein, tubulin, and they grow or shrink as more tubulin molecules are added or removed.
Another function is as tracks that guide motor proteins carrying organelles to their destination.
They are made up of 2 polymer of alpha and beta
tubulin( two globular proteins)
• In animal cells, the centrosome has a pair of
centrioles, each with nine triplets of microtubules arranged in a ring.
• During cell division the centrioles replicate.
Microtubules are the central structural supports in cilia
and flagella.
-Both can move unicellular and small multicellular organisms by propelling water past the organism.
-If these structures are anchored in a large structure, they move fluid over a surface.
Cilia usually occur in large numbers on the cell surface.
They are about 0.25 microns in diameter and 2-20 microns long.
There are usually just one or a few flagella per cell.
Flagella are the same width as cilia, but 10-200 microns long.
In spite of their differences, both cilia and flagella have
the same structure.
Both have a core of microtubules sheathed by the plasma membrane.
Nine doublets of microtubules arranged around a pair at the center, the “9 + 2” pattern.
The outer doublets are also connected by motor proteins.
The cilium or flagellum is anchored in the cell by a basal body, whose structure is identical to a centriole.
MICROFILAMENTS (7nm), the thinnest class of the cytoskeletal fibers, are solid rods of the globular
protein actin.
-A microfilament are made of two intertwined strands of actin
Microfilaments are designed to resist tension.
Enabling cell to move and change its shape just like
WBC
In muscle cells, thousands of actin filaments are
arranged parallel to one another.
Actin is powered by ATP to assemble its filamentous
form
Actin serves a track for the movement of motor
protein known to be your MYOSIN
This enables actin to engage in cellular events requiring motion
INTERMEDIATE FILAMENTS, intermediate in size at 8 -
12 nanometers, are specialized for bearing tension.
Intermediate filaments are built from a diverse class of subunits from a family of proteins called keratins.
Intermediate filaments are more permanent fixtures
of the cytoskeleton than are the other two classes.
They reinforce cell shape and fix organelle location.

EPITHELIAL TISSUE (Covering)
 Tightly-joined closely-packed cells
 One side of exposed to air or internal fluid, other side attached to a basement membrane
 Covers outside of the body and lines internal organs and cavities
 Barrier against mechanical injury, invasive microorganisms, and fluid loss
 Provides surface for absorption, excretion and transport of molecules
Types of Epithelial Tissue
Cell shape
Squamous
Cuboidal
Columnar
Number of cell layers
Simple
Pseudostratified
Stratified
RELATE STRUCTURE TO FUNCTION!
CONNECTIVE TISSUE (Framework)
 Binding and support of other tissues
BONE
collagen fibers in calcium salts
rigid parts of skeleton
support
ADIPOSE TISSUE
storage, insulation, padding
BLOOD
liquid plasma matrix
transport
CARTILAGE
rubbery collagenious matrix
flexible parts of skeleton
support
FIBROUS CONNECTIVE TISSUE
parallel fibers
tendons, ligaments
connecting bones and muscles
LOOSE CONNECTIVE TISSUE
loose weave of fibers
widespread packing material
holds organs in place
MUSCLE TISSUE (Movement)
Composed of long cells called muscle fibers
Contraction  movement
SKELETAL MUSCLE
Unbranched fibers
Striated
Attached to bones
Voluntary movements
CARDIAC MUSCLE
Branched fiber
Striated
Heart, contraction of the heart
SMOOTH MUSCLE
Spindle-shaped cells
Unstriated
Digestive tract, arteries, bladder
Contraction of other internal organs
NERVOUS TISSUE (Control)
Senses stimuli and transmits nerve impulses
Single cell body with long extensions (axons and dendrites)