Cytoskeleton the cytoskeleton is the supporting

Cytoskeleton
The cytoskeleton is the supporting framework of the cell.
Made of protein filaments and rod-like structures, the
cytoskeleton determines the shape of the cell, gives it
strength, and also allows the cell to move. It also helps
organize the contents of the cell. In some cells, the
cytoskeleton forms finger-like processes that extend
outward. These processes include microvilli, cilia, and
flagella.
Microvilli
Microvilli are folds of the cell
membrane that greatly increase
the surface area of a cell. Typically
found in cells charged with
absorbing nutrients—such as the
intestines—microvilli can increase
a cell’s absorptive area as much as
40 times.
Cilia
Cilia are hair-like processes along the
surface of a cell. Unlike microvilli,
cilia move. They beat in waves,
always in the same direction. They
occur primarily in the respiratory
tract—where their wave-like motion
helps move mucus and foreign
particles out of the lungs—and the
fallopian tubes—where their motion
propels an egg cell or embryo toward
the uterus.
Flagella
Flagella (singular: flagellum) are
similar to cilia in that they are
also hair-like projections that
move. However, flagella are
thicker, longer, and fewer in
number. Flagella have a whip-like
motion that helps move a cell.
The only flagellum in humans is
the tail of a sperm cell.
Inner
membrane
Matrix
Outer membrane
Cristae
Endoplasmic
reticulum
Ribosomes
Intermediate
filaments
Microtubule
Mitochondrion
Microfilament
Plasma
membrane
Thompson, Gale Sloan. Understanding Anatomy and Physiology : A Visual, Auditory, Interactive Approach, F. A. Davis Company, 2019. ProQuest Ebook Central,
.
Created from norquest-ebooks on 2022-05-06 05:09:29.
Copyright © 2019. F. A. Davis Company. All rights reserved.

43
CHAPTER 3 Cells
Movement Through Cell Membranes
A cell’s survival depends on its ability to move substances such as nutrients and waste products where they’re needed. Toward
this end, the cell uses a number of transport mechanisms to move substances back and forth across its plasma membrane.
These mechanisms fall into one of two categories: passive or active transport.
Passive Transport
Passive transport mechanisms—which include diffusion, osmosis, filtration, and facilitated diffusion—don’t require the
cells to expend energy.
Diffusion
Diffusion involves the movement of particles from an area of higher concentration to an area of lower concentration.
Diffusion occurs in air or water. It can perhaps be best illustrated by placing a dye tablet in water.
Dye tablet
Time
●
As the tablet dissolves, the particles move away from the tablet (where concentration is high) to the edges of the
container (where the concentration of particles is low).
●
Diffusion continues until the particles are evenly distributed. The point at which no further diffusion occurs is called
equilibrium .