Principles of Cell Biology
Chapter 14: Tissues
Chapter Summary: The Big Picture (1)
• Chapter foci:
– Tissues form macroscopic equivalents of individual
cells.
– Explore how biology merges into anatomy and
physiology by introducing 4 major tissue types
Chapter Summary: The Big Picture (2)
• Section topics:
– Epithelial tissues form protective, semi-permeable
barriers between compartments
– Nervous tissues store and transmit information as
electrical charge
– Muscle tissues convert chemical signals into
mechanical force
– Connective tissues provide mechanical strength
and cushioning to the animal body
Epithelial tissues form protective, semipermeable barriers between
compartments
• Key Concepts:
– Epithelial tissues share important properties with
cellular membranes: they possess structural polarity
and protect the material they enclose, forming a
semi-permeable barrier.
– Epithelial cells contain specialized structures that
help them form strong bonds to each other and the
extracellular matrix.
– Epithelial tissues are specialized to perform specific
functions, including protection, secretion, transport,
and absorption.
Epithelial cells have structural polarity
Figure 14.02:
Epithelial tissues are
macroscopic analogs
of cellular
membranes.
Epithelial tissues are classified according to cellular structure and
function
Figure 14.03:
Examples of
different types of
epithelial tissues.
Some epithelial tissues are optimized for
protection: the epidermis
Figure 14.04:
Structural
organization of
skin.
Some epithelial tissues are optimized for absorption: the
gastrointestinal system
Figure 14.05: The gastrointestinal system.
Figure 14.06: Cross-section of the stomach.
Note the deep folds (gastric pits). The
protective mucous layer is stained dark
purple in this image.
Some epithelial tissues are optimized
for transport: the kidney
Figure 14.07: Summary of kidney function. The
nephron collects wastes filtered from the blood in
Bowman's capsule and converts it into urine for
excretion.
Figure 14.08: Kidney epithelial cells use
transport proteins (pumps, carriers, and
channels) to move material into and out of the
bloodstream.
Nervous tissues store and transmit
information as electrical charge
• Key Concepts:
– Nervous tissues are composed of neurons and
supportive cells called glial cells.
– Neurons transmit information in the form of an
electrical current that is passed between neurons.
The network of interconnected neurons in an
organism is functionally analogous to the signaling
network in a single cell.
– The electrical current is conducted through individual
neurons by a coordinated transport of ions across
the plasma membrane - an action potential.
Nervous tissues are the macroscopic
equivalent of the information transfer
network
Nervous tissues are composed of at
least 2 different cell types
• 2 types of cells:
– Neurons - store and transmit electrical
information
– Glial cells - provide support to the neurons but
do not actually manipulate the information
Neurons transmit signals via action potentials
Figure 14.10:
Summary of action
potential generation
in a neuron.
Glial cells support neurons and increase the speed of action
potential transmission
Figure 14.11: Structural organization of nerve cells.
Glial cells support neurons and increase the speed of action
potential transmission
• Myelin sheath
– Schwann cells
– Oligodendrocytes
• Sphinganine
Figure 14.12: Glial cells
wrap neurons with
myelin. Some glial cells
wrap a portion of one
axon, others wrap
many. The gaps
between wraps are
called Nodes of Ranvier.
Figure 14.11: Structural organization of nerve cells.
The synapse is a customized junction to
facilitate cell–cell communication
Figure 14.14: A model of how myelin-associated glycoprotein (MAG) and Nogo-66 receptor
participate in suppression of neurite outgrown in neurons.
Muscle tissues convert chemical signals into
mechanical force
• Key Concepts (1):
– Muscles are effectors targeted by the nervous system
and composed primarily of muscle tissue.
– Muscle tissues are classified into three types: skeletal,
cardiac, and smooth muscle. Collectively, muscle and
bone tissues form the functional analog of the
cytoskeleton in tissues.
– Skeletal muscle cells are multinucleated, terminallydifferentiated cells composed of parallel actin and
myosin bundles called sarcomeres. They are
stimulated to contract by the electrical current passing
from neurons to the muscle cells.
Muscle tissues convert chemical signals into
mechanical force
• Key Concepts (2):
4) Cardiac muscles are structurally similar to
skeletal muscle cells, except they contract
autonomously and are found only in the heart.
5) Smooth muscles lack sarcomeres, and are
capable of contracting in several directions. This
enables them to line tubes such as blood vessels
and airways and control their diameter. Smooth
muscle cells are also capable of sustaining
contractions much longer than skeletal or cardiac
muscle cells.
Each type of muscle tissue is specialized for a different type of motion
Figure 14.15: Transmission of
information at a chemical synapse.
This material is
definitely on the
third exam
Skeletal muscle cells are multinucleated, highly-specialized cells
• Sarcomeres are
combined to form muscle
fibrils
• Action potentials
stimulate skeletal muscle
contraction
Figure 14.17: Structural
organization of skeletal muscle.
Skeletal muscle cells are multinucleated, highly-specialized cells
Figure 14.16: Three classes of
muscle tissue: skeletal (top),
smooth (middle) and cardiac
(bottom). Note that both skeletal
and cardiac muscle form large,
multinucleated cells called fibers.
Skeletal muscle contraction is driven by the crossbridge cycle
Figure 14.18: How an
action potential
triggers skeletal
muscle contraction.
3D model of Sarcomere
Sarcoplasmic Reticulum Stores Ca+2
Troponin and Tropomyosin Control
Skeletal Muscle Contraction
Better drawing of
Troponin/Tropomyosin
Figure 14.19: The
crossbridge cycle for
skeletal muscle
contraction.
Cardiac muscle is responsible for pumping blood
Figure 14.20: Structural
organization of mammalian
heart. Note that blood flow
changes direction in the left and
right ventricles.
Figure 14.21: Transmission of action potentials in cardiac muscle.
Smooth muscle cells generate force in three dimensions
Figure 14.23: Smooth muscle forms a
contracile layer around all but the
smallest blood vessels.
Smooth Muscle Contracts in All
Directions
Smooth muscle cells generate force in three dimensions
Figure 14.22: Summary
of signaling mechanisms
controlling smooth
muscle cell contraction.
Note that all converge
on myosin II regulatory
light chain
phosphorylation.
Connective tissues provide mechanical
strength and cushioning to the animal
body
• Key Concepts:
– The term “connective tissue” refers to a wide
variety of tissues that collectively fill spaces
between epithelial, nervous, and muscle tissues. In
most cases, connective tissue is characterized by
the type and organization of the ECM it contains. It
is analogous to the ECM surrounding individual
cells.
– Most connective tissues are classified into five
types. Each type is populated by different cells that
secrete and organize the ECM.
Common property of connective tissues
• “glue” that holds cells and tissues
together
• Contains well organized ECM to:
– Form stable bonds between neighboring cells
– Govern the location and behavior of the cells
– Provide a means for intercellular
communication
5 types of connective tissue
•
•
•
•
•
Loose connective
Dense connective
Elastic
Reticular
Adipose