Chapter 3: Cells and Tissues
I. Overview of the Cellular Basis of Life
A. Cells are the building blocks of all
living things. The human body
has 50 to 60 trillion of these tiny building
blocks.
B. Cells carry out all chemical activities
needed to sustain life.
C. Our cells are made of four primary
elements- carbon, hydrogen, oxygen and
nitrogen
D. 60% of our cells are made of water
(one reason it is essential for life)
E. Cells of the body are constantly
bathed in a dilute saltwater solution called
interstitial fluid.
1. All exchanges between cells and
blood are made through interstitial fluid.
F. Cells vary dramatically in the functions
they play within the body.
II. Anatomy of a Cell
A. Cells are organized into three
main regions
1. Nucleus
a. contains DNA (genetic
material)
2. Cytoplasm
3. Plasma Membrane
a. barrier for cells contents
b. double phospholipids bilayer
c. Selectively permeableregulates what enters leaves
the cell
Selective Transport Animations
d. Plasma
membrane junctions; the meeting
of two adjacent cell membranes. There are
three types:
i.
ii.
iii.
Tight junctions- fit together like a
zipper forming an impermeable
junction. These exist in cells lining
the digestive tract to keep digestive
enzymes and microorganisms from
seeping into the bloodstream.
Desmosomes- anchoring junctions
that prevent cell separation. These
are abundant in tissues that are
subjected to great mechnical stress,
such as skin cells.
Gap junctions- the cells are
connected by hollow cylinders
(connexons) which allows chemical
substances to pass between cells.
These are abundant in heart muscle
tissue where the movement of ions
from cell to cell to synchronize the
heart rhythm.
B. The anatomy of a cell
C. Cell Diversity
1. All cells share the same general
structures; a cell membrane, a nucleus
and cytoplasm. However, their function in
the body is different. See examples
below:
Secretory vs. Absorptive
Epithelial Picture
III. Body Tissues
A. Tissues are groups of
cells with similar
structure and function.
B. Four primary tissues
types:
1.
2.
3.
4.
Epithelium (covering)
Connective (support)
Nervous Tissue (control)
Muscle (movement)
IV. Epithelium
A.
B.
C.
Found in different areas of the body,
such as body coverings, body linings,
and glandular tissue.
Functions are for protection (skin),
absorption (small intestine),filtration
(kidneys), and secretion (glands).
Characteristics of epithelial tissue
include:
1.
Cells fit closely together
2.
Tissue layer always has one free
surface (the apical surface) that is
exposed to the cavity of an
internal organ or the body’s
exterior.
3.
The lower surface is bound by a
basement membrane.
4.
Avascular (these tissues have no
blood supply of their own)
5.
Regenerate well if nourished.
D. Classification of epithelium
1. Number of cell layers
a. simple- one layer
a. stratified- more than one layer
2. Shape of cells
a. squamous- flattened
a. cuboidal- cube shape
a. columnar- column- like
Types of Epithelium
Thin for
gas
exchange
between
alveoli and
capillaries
Can secrete
mucus and
have cilia to
help clean air
Contain
lots of
golgi and
ER to
manufact
ure and
secrete or
absorb
Many layers
of cells to
replace those
lost when
swallowing
Adapted for
secretion of
mucus and
ciliated to
propel food
Stretches as
bladder fills
with urine
V. Connective Tissue
A. Found everywhere in the body, the most
abundant and widely distributed tissue.
B. Functions include: binding tissues together,
support, and protection
C. Characteristics of connective tissue:
1. Variations in blood supply- some tissue
types are well vascularized (have good
blood supply), while some have a poor
blood supply (tendons and ligaments).
Cartilage is avascular.
2. Extracellular matrix- the nonliving
material that surrounds the tissue. (This
is what makes connective tissue so
different from other tissues.)
a. Matrix is composed of a ground
substance (water,protein, and other
molecules) and fibers
(collagen,elastic, reticular).
b. The matrix allows connective tissue
to act as a soft packing tissue
around organs (adipose tissue), to
bear weight, or withstand stretching
and abrasion (bones, tendons and
ligaments).
V.
Connective Tissue
D. Connective tissue types:
1. Bone (osseous) - composed of bone cells, hard
matrix of calcium salts, large numbers of collagen
fibers.
a. used to protect and support the body
V.
Connective Tissue
D. Connective tissue types:
2. Hyaline Cartilage- most common type of
cartilage, composed of collagen and matrix
a. Entire fetal skeleton is hyaline cartilage, but by the
time of birth, most cartilage is replaced by bone.
V. Connective Tissue
D. Connective tissue types:
3. Elastic cartilage- provides elasticity
a. Example- supports the external ear
4. Fibrocartilage- highly compressible
a. Example- forms cushion-like discs between
vertebrae
V. Connective Tissue
D. Connective tissue types:
5. Dense connective tissue- main matrix element
is collagen fibers which form strong rope-like
structures, (the collagen producing cells are
called fibroblasts)
a. Example- tendons (attach muscle to bone),
ligaments (attach bone to bone)
V. Connective Tissue
D. Connective tissue types:
6. Areolar connective tissue- most widely distributed
connective tissue that serves as a kind of universal
packing material between other tissues
a. contains all fiber types,
b. can soak up excess fluid (this is the tissue that swells causing
edema)
c. universal packing tissue and “glue” that holds internal organs
together
V. Connective Tissue
D. Connective tissue types:
7. Adipose tissue- commonly called fat
a. matrix is Areolar tissue in which fat globules are
predominate
b. these cells contain large deposits of lipids
c. functions to insulate the body, protect organs, and
serves as a site of fuel storage
V. Connective Tissue
D. Connective tissue types:
8. Reticular connective tissue-delicate network of
interwoven fibers
a. forms internal network of lymphoid organs (lymph
nodes, spleen, and bone marrow)
V. Connective Tissue
D. Connective tissue types:
9. Blood- blood cells surrounded by a fluid
matrix
a. fibers are visible during clotting
b. functions as the transport vehicle for materials
IV. Muscle Tissue
A. Functions to produce movement
B. Three types are:
1.
2.
3.
Skeletal muscle- voluntary, striated
Smooth muscle – involuntary, surrounds organs
Cardiac muscle- involuntary, only in heart, striated
i.
Intercalated disks are the junctions that allow heart cells to rapidly
conduct electrical impulses through the heart.
VII. Nervous Tissue
A.
B.
C.
Composed of neurons and nerve support cells
Functions to send and receive impulses to other
areas of body
Located in nervous system structures such as the
brain, spinal cord and nerves.
VIII. Tissue Repair (Wound Healing)
A. Two types of tissue repair:
1. Tissue regeneration is the
replacement of destroyed tissue by
the same kind of cells
2. Fibrosis occurs when repair by
dense fibrous connective tissue called
scar tissue forms. Fibrosis occurs in
cardiac and nervous tissues of the
body.
B. The type of tissue repair depends on the type of
tissue damage and the severity of the
injury.
C. Steps in Tissue repair
1. Capillaries become very
permeable.
2. Clotting proteins and other
substances seep into the injured
area.
3. A clot is constructed to wall off the
injured area (when the clot dries and
hardens this forms the scab).
4. Formation of granulation tissue
(delicate tissue that is made
of new capillaries that grow into the
damaged area).
a. this tissue also contains fibroblasts
that synthesize collagen fibers that
bride the gap
5. Surface epithelium regenerates; this covers
an underlying layer of fibrosis (the scar).
D. The regeneration of tissue
1. Tissues that regenerate easily: epithelial, fibrous
connective, and bone
2. Tissues that regenerate poorly: skeletal muscle
3. Tissues that are replaced largely with scar tissue:
cardiac and nervous tissue within the brain and spinal
cord. Scar tissue lacks the normal flexibility of
tissues which hinders the functioning.
E. As we age there is a decrease in mass and viability
of most tissues. The epithelia thin, the amount of
collagen in the body declines which makes tissue repair
less efficient, and nervous tissues begins
to atrophy.