Chapter 3: Tissues, Organ Systems, and Homeostasis
Key concepts:
1. Cells interact to form tissues, many of which are combined in
organs, which are components of organ systems.
2. Organs are constructed of four basic classes of tissues: epithelial,
connective, muscle, and nerve tissues.
3. Each cell engages in basic metabolic activities that assure its own
survival. At the same time, cells, tissues, and organs perform
activities that contribute to the survival of the body as a whole.
4. The combined contributions of cells, tissues, organs, and organ
systems help maintain a stable internal environment (homeostasis),
which is required for our body’s survival.
Introduction: The body in balance:
A. The human body is adapted to:
1. Maintain internal conditions within tolerable range.
2. Locate and acquire nutrients and dispose of wastes.
3. Protect itself against injury or microbial attack.
4. Reproduce and provide for offspring during development.
B. Humans exhibit levels of organization.
1. A tissue is an aggregation of cells and substances functioning
for a specialized activity.
2. Various types of tissues can combine to form organs
3. Organs may interact to form organ systems.
3.1 Epithelial Tissue
A. Features of epithelium:
1. One surface is free (may have cilia or microvilli) and the
other adheres to a basement membrane.
2. Cells are linked closely together; there may be one or mare
layers.
3. Specialized junctions form links between cells.
4. Simple epithelium is a single layer of cells functioning as a
lining for body cavities, ducts, and tubes.
a. Squamous epithelium has flattened cells; lining of blood
vessels
b. Cuboidal epithelium has cube-shaped cells; example:
glands
c. Columnar epithelium has elongated cells; example:
intestine
5. Stratified epithelium has many layers; example: human skin
(protection)
6. Pseudostratified epithelium is a single layer of cells that
looks like a double layer;
o most of the cells are ciliated
o example: respiratory passages and reproductive tracts
o
Station 3.1B (Table 1)
3.1 Epithelial Tissue
B. Glands derived for Epithelium
1. Glands are secretory structures derived from epithelium
Examples:
o Mucus-secreting cells in the trachea (windpipe)
o Glandular cells that secrete mucus and other substances
in the stomach epithelium
2. Endocrine glands have no ducts. They secrete hormones
into tissue where the bloodstream will pick them up and
deliver throughout the body.
3. Exocrine glands secrete substances onto a free epithelial
surface through ducts or tubes. Examples: mucus, saliva,
earwax, oil, milk, and digestive enzymes
On your lab sheet…
 Using the prepared slide, focus on the mucus-secreting cells in the
trachea.
 Make a pencil-line drawing of a few cells.
Questions to ponder and answer:
1. Drinking eight glasses of water a day keeps the body “lubricated.”
From what you know about Exocrine glands, give five specific
examples why must we consume so much liquid.
Example: Breast milk has a base of water, therefore nursing mothers
must consume water so the mammary glands will function properly.
Station 3.1C (Table 2)
3.1 Epithelial Tissue
C. Membranes
1. Membranes are various types of thin, sheetlike epithelium
with underlying connective tissue that covers or lines organs.
a. Mucous membranes that line the tubes and cavities of
the digestive, respiratory and reproductive systems
contain glands that secrete mucus.
b. Serous membranes, such as those that line the thoracic
cavity, do not contain glands. They help hold internal
organs in place and provide lubricated smooth surfaces
to prevent chafing.
On your lab sheet…
 Draw the torso presented here
 Label the membranes
Questions to ponder and answer:
2. Infection in the abdominal cavity often involves the
peritoneum (membrane lining the walls of the abdominal
cavity). For instance, a ruptured appendix allows the escape
of intestinal contents, loaded with bacteria, into the peritoneal
cavity. This leakage causes a life-threatening infectious
condition called peritonitis.
 Why do you think it is necessary to operate to take
someone’s painful, infected appendix out?
 If the infected appendix ruptured (burst), what type of
medicinal treatment would be necessary? (Remember
our infectious disease unit and bacteria…)
Station 3.2 and 3.6 (Table 3)
3.2 Spare Parts
A. New, replacement tissues (or organs?)
1. Skin: Advanced Tissue Sciences, La Jolla
2. Artificial bone from synthesized tissues
3. Substitute blood
a. Blood donations don’t keep up with demand
b. Diseases in donated blood…Correct blood type?
c. Substitute blood solution contains carbohydrate to maintain
proper water content and oxygen-binding PFC. Drawbacks:
short-lived and side effects
d. Solution with cow hemoglobin, drawback: BSE? high
manufacturing costs
e. Genetically engineered human hemoglobin in pigs: high cost
(skip ahead to 3.6 on your notes)
3.6 Blood and Adipose Tissue
A. Blood is a fluid tissue derived from connective tissue.
1. The fluid plasma contains suspended red blood cells (oxygen
transport) and white cells (defense) and platelets (clotting).
2. Blood transports oxygen, wastes, hormones, and enzymes.
B. Adipose tissue cells are specialized for the storage of fat.
1. Fat can be used as an energy reserve and cushions to pad organs.
2. Adipose has a rich supply of blood vessels, which serve as highways
for the movement of fats to and from individual adipose cells.
On your lab sheet…
 Using the prepared slide, focus on the human blood smear.
 Make a pencil-line drawing of several red blood cells and a white
blood cell.
Questions to ponder and answer:
3. List two reasons why a plastic surgeon shouldn’t remove all
of the adipose tissue from a patient having liposuction.
At the next station, go back in your notes to section 3.3
Station 3.3 (Table 4)
3.3 Cell-to-Cell Contact
A. Cells adhere to one another in three ways:
1. Tight junctions: strands of proteins that prevent leaks
between adjacent cells. Examples: epithelium (stomach
lining, skin)
2. Adhering junctions: proteins attached to cell walls that
cement cells together and are anchored to cytoskeleton (can
be stretched- muscle)
3. Gap junctions: help in cell communication. Contains small,
open channels that directly link the cytoplasm of adjacent
cells—ideal for rapid feedback (heart).
On your lab sheet…
 Using the handout provided, draw and label the three types of
junctions.
Questions to ponder and answer:
5. Copy the following list of tissues. Write what type of junction
cells in the tissue would have and WHY.
a. stomach lining
b. intestine lining
c. leg muscle
d. heart muscle
e. nervous tissue
f. taste buds
Station 3.4 (Table 5)
3.4 Overview of Connective Tissues
A. Connective tissues are the most abundant and widely distributed tissue in
the human body.
They bind together, support, strengthen, protect, and insulate other body
tissues. Most consist of: protein fibers and a variety of cells in a ground
substance secreted by the embedded cells (extracellular matrix).
1. Most connective tissue contains fibroblasts which secrete fibers
made of collagen or elastin.
B. Connective tissue proper
1. Loose connective tissue: supports epithelia and organs and
surrounds blood vessels and nerves; it contains more cells and fewer,
thinner fibers.
2. Dense, irregular connective tissue has fewer cells and more fibers
which are thick; it forms protective capsules around organs.
3. Dense, regular connective tissue has bundled collagen fibers lying
in parallel; such arrangements are found in ligaments (binding bone to
bone) and tendons (binding muscle to bone).
C. Specialized connective tissue:
Examples: Cartilage, bone, blood, adipose tissue
On your lab sheet…
 List the different types of connective tissue from Figure 5-5
Questions to ponder and answer:
6. Connective tissue share two characteristics. First, most connective tissue (except
ligaments, tendons, and cartilage) has good blood supply. Ligaments and tendons
have a poor blood supply, and cartilage has no blood supply. Second, connective
tissue has an abundance of extracellular matrix—secreted substance and
protein/fibers.
 If these three tissues had an injury, which would heal most rapidly? Most
slowly? WHY? Ligament, cartilege, muscle
7. What does loose connective tissue do?
3.5 Cartilage and Bone (Table 6)
A. Cartilage contains a dense array of fibers in a rubbery ground
substance (matrix) produced by chrondroblasts that mature into
chondrocytes located in lacunae.
1. Hyaline cartilage has many small fibers; it is found at the
ends of bones, in the nose, ribs, and the windpipe.
2. Elastic cartilage, because of its elastin component, is able to
bend yet maintain its shape such as in the external ear.
3. Fibrocartilage is a sturdy and resilient form that can
withstand pressure such as in the disks that separate the
vertebrae.
B. Bone is organized as flat plates and cylinders, bones support and
protect body tissues and organs; they also work with muscles to
perform movement
1. The bone matrix is mineralized (calcium) and hardened, but
includes lacunae for the osteocytes
2. Compact bone appears to be very solid and makes up the
shafts of long bones and the outer regions of all bones.
3. Spongy bone occurs inside bones and includes large,
marrow-filled spaces.
On your lab sheet…
 Using the prepared slide, focus on the BONE and CARTILAGE.
 Make a pencil-line drawing of these two tissues
Questions to ponder and answer:
8. What are some similarities between cartilage and bone? What are
some functions of cartilage? How are the functions of cartilage and bone
similar?
3.7 Muscle Tissue (Table 7)
A. Muscle tissue contracts in response to stimulation, then
passively lengthens.
B. There are three types of muscle:
1. Skeletal muscle tissue attaches to bones for voluntary
movement; it contains striated (actin and myosin)
multinucleated, long cells (fibers) which are often bundled
together to form “a muscle.”
2. Smooth muscle tissue contains spindle-shaped cells with a
single nucleus; it lines the gut, blood vessels, and glands; its
operation is involuntary.
3. Cardiac (heart) muscle is composed of short, striated cells
that can function in units due to the signals that pass by way
of the gap junctions.
On your lab sheet…
 Using the prepared slides, focus on the three types of muscle.
 Make a pencil-line drawing of these three tissues.
Questions to ponder and answer:
8. Briefly describe the tissues next to your drawings.
3.8 Nerve Tissue (Table 8)
A. Neuron Structure
1. Neurons, and associated cells, are organized as lines of
communication throughout the body.
2. Branched dendrites pick up chemical messages and pass
them to an outgoing axon.
3. Communication between neurons is by neurotransmitters,
such as acetylcholine.
4. A nerve is a bundle of neuron processes conducting to and
from the CNS.
B. Neuron functions
1. Sensory neurons pick up stimuli and conduct messages to the
central nervous system.
2. Motor neurons conduct impulses to muscles and glands.
On your lab sheet…
 Using the prepared slide, focus on the Neurons and spinal chord.
 Make a pencil-line drawing of these tissues.
Questions to ponder and answer:
10. Nervous tissue makes up the brain, spinal chord, and the nerves.
They transmit electrical signals to and from the brain and spinal
chord. What are the five senses that sensory neurons transmit?
11. Name three diseases that are caused by some form of nerve
dysfunction.
3.9 Organ Systems (Table 9)
A. Eleven organ systems contribute to the survival of the living cells
of the body: integumentary, muscular, skeletal, nervous, endocrine,
circulatory, lymphatic, respiratory, digestive, urinary, and
reproductive.
B. The major cavities of the human body are: cranial, spinal,
thoracic, abdominal, and pelvic.
C. Directional terms for the human body are: anterior, posterior,
superior, inferior, distal, proximal
D. Planes of symmetry for the human body are: transverse,
midsagittal, and frontal
On your lab sheet…
 Using the Handout on the table, try to match the numbers with the
terms in B, C, and D above.
12. After you think you have figured all of them out, write them out,
(a-n) on your lab sheet.
Quiz each other on the terms, we’ll be having a test soon! If you’re unsure
of an answer, look on the overhead.
3.10 Skin: an Organ System
A. The integument is the outer covering of humans including nails
and hair.
B. Skin functions:
1. Protection from abrasion, bacterial attack, UV radiation, and
dehydration.
2. Helps control internal temperature
3. Its vessels serve as a blood reservoir for the body
4. The skin produces vitamin D
5. It contains receptors for detecting environmental stimuli.
C. Skin Structure
1. Epidermis refers to the thin, outermost layers of cells
consisting of stratified, squamous epithelium
a. The outermost layer consists of dead bags of keratin, a
waterproofing protein
b. Three pigments contribute to skin color: melanin,
hemoglobin, and carotene
2. Dermis, the thicker portion of the skin underlying the
epidermis, is mostly dense connective tissue. The dermis
contains:
a. blood vessels, lymph vessels, and nerve endings
b. sweat glands (helps regulate temperature)
c. oil glands to soften and lubricate the hair and skin (acne
occurs when bacteria when the ducts become infected by
bacteria)
d. hairs rooted here—growth influenced by hormones,
nutrition, and genes
e. As the body ages, epidermal cells divide less often, skin
becomes thinner, more susceptible to injury, drier, and
less elastic
3.11 Sun, Skin and Ozone Layer
A. Melanin-producing cells are stimulated by exposure to UV
radiation (sun-tan)
B. Drawbacks: leathery skin, immune suppression, cancer…Why
do we desire a tanned look?
3.12 Homeostasis and Systems Control
A. The Internal Environment
1. Trillions of cells must constantly be bathed in fresh liquid to
supply nutrients and carry away metabolic waste
2. The extracellular fluid consists of plasma and interstitial
fluid (between cells and tissues)
3. The component parts of the body work together to maintain
the stable fluid environment required by its living cells.
a. Each body cell engages in metabolic activities that
ensure its own survival
b. Cells of a tissue perform one or more activities that
contribute to the survival of the whole organism.
c. The combined contributions of individual cells, tissues,
organs, and organ systems help maintain the stable
internal environment.
B. Mechanisms of homeostasis to maintain tolerable limits
1. Sensory receptors are cells that can detect a stimulus (a
specific change in an environment)
2. Integrators (brain and spinal chord) act to direct impulses to
the place where a response can be made (muscles).
3. Effectors (muscles and glands) perform the appropriate
response.
C. Negative feedback detects a change in the internal environment that
brings about a response that tends to return conditions to the original state
(like a thermostat/heating/cooling system)
D. Positive feedback mechanisms set in motion a chain of events that
intensify a change form an original condition. For example: labor
contractions and oxytocin.