Anatomy and Physiology
Chapter 5: Tissues
Chapter Objectives:
1. Describe the general characteristics and functions of epithelial tissue.
2. Name the types of epithelium and identify an organ in which each is found.
3. Explain how glands are classified.
4. Describe the general characteristics of connective tissue.
5. Describe the major cell types and fibers of connective tissue.
6. List the types of connective tissue.
7. Describe the major functions of each type of connective tissue.
8. Describe the four major types of membranes.
9. Distinguish among the three types of muscle tissue.
10.Describe the general characteristics and functions of nervous tissue.
Chapter 5
Tissues:
1. A group or mass of similar cells working together to perform certain common functions
2. Can be distinguished from each other by variation in cell size, shape, organization, and
function.
3. The study of tissues is called histology.
4. There are four different types of tissues:
a. Epithelial
b. Connective
c. Muscle
d. Nervous
Epithelial Tissue
a. General characteristics
i. Found throughout the body, covers all
body surfaces inside and out.
ii. Always has a free surface, or one that is
exposed to the outside or to an open
space internally
iii. Main glandular tissue
iv. Attached to underlying connective tissue
by noncellular nonliving basement
membrane
v. Usually has no vascular tissue (no blood
supply), however, nutrients diffuse to
epithelium from underlying connective
tissues, which have abundant blood
vessels.
vi. Cell reproduce rapidly (heal rapidly)
vii. Cells tightly packed together (typically via tight junctions and desmosomes)
b. Major Functions
i. Protection
ii. Secretion
iii. Absorption
iv. Excretion
v. Sensory perception
c. Categorized based on the shape of the cells and the layers of the cells. Epithelial
tissues that are composed of thin, flattened cells are squamous; those with cubelike
cells are cuboidal; those with elongated cells are columnar; those with a single layer
are simple; and those with many layers are complex.
d. Types of Epithelium
i. Simple Squamous Epithelium
1. Consists of a single layer of thin,
flattened cells.
2. Fit tightly together (like floor tiles)
3. Nuclei are usually more broad and thin
than other cells
4. Substances pass easily thought this
epithelium
a. Can be found lining the air sacs in the lungs (alveoli)
b. Forms the walls of capillaries
c. Lines the walls of blood and lymph vessels
ii. Simple Cuboidal Epithelium
1. Consists of a single layer of cube-shaped cells
2. Have a centrally located, spherical nuclei
a. Lines the follicles of the thyroid gland
b. Covers the ovaries
i. Simple cuboidal epithelial cells’ ability to rapidly divide
and proliferate enables them to repair ovulatory defects that
occur on the ovarian surface, especially during the time of
ovulation. There have also been studies linking the majority
of ovarian cancer causes to the simple cuboidal layer.
c. Lines the kidney tubules
i. It functions in tubular secretion and tubular reabsorption
iii. Simple Columnar Epithelium
1. Composed of a single layer of
elongated cells whose nuclei are usually
at about the same level- near the
basement membrane
2. Can be ciliated or non-ciliated
3. Ciliated simple columnar epithelium
a. Cilia of simple columnar
epithelium aid in moving the egg
cell through the uterine tube to the uterus
4. Non-ciliated simple columnar lines the uterus
5. Non-ciliated simple columnar also lines portions of the digestive tract
a. Secretes digestive fluids and absorbs nutrients from digested food.
iv. Pseudostratified Columnar Epithelium
1. Appear stratified or layered, but are
not.
a. The layered effect occurs
because the nuclei are at two
or more levels in the row of
aligned cells
2. These cells commonly have cilia
and are lined with goblet cells that
secrete mucous
a. This epithelium line the respiratory tract
i. The mucous secreted by the goblet cells and the cilia help
move foreign particles trapped in the respiratory up to be
expelled from the body
v. Stratified Squamous Epithelium
1. Named for the shape of the
cells forming the outermost
layers
2. Consists of many layers of flat
cells, making this tissue very
thick
3. Cells near the surface are
flattened, whereas those in
deeper layers (where cell
division occurs) are cuboidal
and columnar
4. The outermost layer of skin (epidermis) is stratified squamous
a. As the older cells are pushed outward, they accumulate a protein
called keratin, then harden and die
i. Lose nucleus
b. This “keratinization” produces a covering of dry, tough, protective
material that prevents water from escaping and microorganisms
from entering.
i. Heel
ii. Also lines the oral cavity, vagina, and anal canal. These
sells are not keratinized.
vi. Stratified Cuboidal Epithelium
1. Consists of two or three layers of cuboidal cells that form the lining of a
lumen.
2. This layering provides more protection
a. Forms the lining of the mammary glands, sweat glands, and
salivary glands. (lining ducts/ glands)
vii. Stratified Columnar Epithelium
1. Consists of several layers of cells
2. Superficial (outermost) cells are
elongated, whereas the basal (bottom)
layers consist of cube-shaped cells
a. Located in parts of the male
urethra, & pharynx
viii. Transitional Epithelium
1. Specialized to change in response to increased tension
a. It forms the inner lining of the urinary bladder, ureters, and part of
the urethra.
i. When one of
these organs
contracts, the
cells look like
several layers
of cuboidal
cells, when the
organ is distended, the tissue stretches and the physical
relationship among the cells change.
b. This also prevents the contents of the urinary tract from diffusing
back into the internal environment
Connective Tissue
a. General Characteristics
i. Comprise much of the bodily
tissues
ii. Most abundant type by weight
iii. Have an abundance of
extracellular matrix between
them
2. Consists of fibers and a
ground substance
whose consistency
varies from fluid to
semi-solid to solid
3. It functions to bind,
support, and provide a
medium through which substances may be transferred between the blood
and cells within a tissue
iv. Have varying degrees of vascularity (blood supply)
v. Bone and cartilage are rigid
vi. Loose connective tissue and dense connective tissue are more flexible
b. Functions
i. Bind structures
ii. Provide support and protection
iii. Serve as frameworks
iv. Fill spaces
v. Store fat
vi. Produce blood cells
vii. Protect against infection
viii. Help repair tissue damage
1. Major Cell Types
a. Connective tissue contain a variety of cell types, however all can be classified two
ways:
i. Fixed- cells that reside in a specific connective tissue type for an extended
period of time.
1. Ex.// fibroblasts, mast cells
ii. Wandering- cells that move through and appear in tissues temporarily, usually
in response to injury or infection
1. Ex.// macrophages
b. Connective Tissue cell types
i. Fibroblast
1. Most common cell within connective
tissues
2. Large, star-shaped cells that produce fibers
by secreting proteins into the extracellular
matrix of connective tissues
ii. Macrophages
1. Originate as white blood cells
2. Are almost as numerous as
fibroblasts in some connective
tissues
3. Usually attached to fibers, but
can detach and actively move
about
4. Specialized for phagocytosis
a. Function as scavenger
cells that can clear foreign
particles from tissues
b. Important against
infection & play a role in
human immunity
i. Start immune response to foreign invader
ii. Not only fight individually by eating “non-self” cells, but
also send chemical signals to helper T cells and killer T
cells (part of the immune response)
iii. Mast Cells
1. Usually located near blood
vessels
2. Release heparin, which is a
compound that prevents blood
clotting
3. Also release histamine, which
is a substance that promotes
some of the reactions
associated with inflammation
and allergies
a. Release of histamine
stimulates
inflammation by dilating arterioles that feed capillaries. The
resulting swelling is not favorable for infectious bacteria and
viruses and stops their spread.
b. Often times the body releases histamine due to other particles that
you have breathed in. This can trigger an allergic response
2. Connective Tissue Fibers
a. Fibroblasts (most common cell type/ star shaped) produce three types of connective
tissue fibers: (You will be accountable for two of the three types)
i. Collagenous fibers- most abundant
ii. Elastic fibers
b. Collagenous Fibers
i. Thick threads of the
protein collagen
1. Major structural
protein of the body
2. Grouped in long,
parallel bundles
3. Flexible but
slightly elastic
4. Can resist considerable pulling force
a. Important components of body parts that hold structures together,
such as ligaments (connect bones to bones) and tendons (connect
muscles to bones)
5. Tissues that are abundant with Collagenous fibers are called dense
connective tissue
6. Issues with Collagenous fibers
a. When skin is exposed to prolonged and intense sunlight,
connective tissue fibers loose elasticity, and the skin stiffens and
becomes leathery
b. Cosmetic collagen injections temporarily smooth out wrinkles
c. However, collagen applied as a cream to the skin does not combat
wrinkles because collagen molecules are much too large to
penetrate skin
d. Botox injections as a cosmetic procedure do reduce wrinkles, but
is unrelated to collagen
i. Produced from the bacteria, Clostridium botulinum
1. In small, medical doses, this bacterium blocks the
release of a chemical known as acetylcholine that is
released by the nerve cells, virtually blocking
electrical messages sent by the brain (and more
specifically, by acetylcholine) to the muscles to
contract and move. Because these messages are
blocked, there is less of a chance of developing fine
lines and wrinkles.
ii. Elastic Fibers
1. Compose of spring-like protein called elastin
2. Weaker than Collagenous fibers, but are very elastic (remain in same
shape)
3. Easily deformed or stretched, but will resume their original lengths and
shapes when the force acting upon them is removed
4. Commonly found body parts that are subjected to stretching
a. Vocal cords
b. Air passages of the respiratory system
iii. Collagen vs. Elastin
1. Both are proteins of connective tissue
2. Collagen is widespread in the body and gives connective tissue strength
and flexibility, deals more with tensile strength. Elastin is a protein that
returns to its original shape after being stretched. While collagen occurs
more widely in the body, collagen and elastin are necessary for the
function of many tissues.
3. Categories of Connective Tissue
a. Broken down into two major categories
i. Connective tissue proper
1. Loose connective tissue
2. adipose tissue
3. reticular connective tissue
4. dense connective tissue
5. elastic connective tissue
ii. Specialized connective tissues
1. Cartilage
2. Bone
3. Blood
b. Loose Connective Tissue
i. Forms delicate, thin membranes
throughout body
ii. The cells of this tissue, mainly fibroblasts,
are located some distance apart
1. Separated by a gel-like ground
substance that contains many
Collagenous and elastic fibers
iii. Binds the skin to the underlying organs
and fills spaces between muscles.
c. Adipose Tissue
i. Also known as fat
ii. Adipocytes store fat in droplets within
their cytoplasm
iii. At first these cells resemble fibroblasts
1. However, they accumulate fat
quickly, enlarge, and their nuclei are
pushed to one side
iv. When adipocytes become so abundant that
they crowd out other cell types, they form
adipose tissue
v. This tissue is found:
1. Beneath skin
2. In between muscle
3. Around kidneys
4. Behind the eyeballs
5. In certain abdominal membranes
6. On the surface of the heart
7. Around certain joints
vi. This tissue functions to:
1. Cushion joints and some organs (kidneys)
2. Insulate beneath skin
3. Store energy (in fat molecules)
vii. Each person is born with a specific number of fat cells
1. Excess food calories are likely to be converted to fat and stored
a. Therefore, the amount of adipose tissue in the body reflects diet or
an endocrine disorder
i. Hyperthyroidismoveractive tissue within
thyroid gland, which
causes an increase of
thyroid hormones in the
blood. Increases
metabolic rate, which
increases weight loss,
anxiety, weakness,
fatigue, etc. Most
commonly caused by
inflammation of the thyroid gland.
ii. Hypothyroidism- tissue in thyroid gland isn’t working as it
typically does. The thyroid gland does not make enough
thyroid hormone. Decreases metabolic rate, which increases
weight gain. It is most commonly caused by an iodine
deficiency.
2. During a period of fasting, adipocytes lose their fat droplets, shrink, and
become more like fibroblasts again.
d. Dense Connective Tissue
i. Two subclasses according to how organized the fiber patterns are:
1. Regular
2. Irregular
ii. Collagenous fibers of regular dense connective tissue are very strong, enabling
the tissue to withstand pulling forces.
1. Binds body parts together (tendons, ligaments)
2. Blood supply to dense connective tissue is poor, slowing tissue repair.
3. This is why a sprain, which damages tissues surrounding a joint, may
take considerable time to heal
iii. Fibers of irregular dense connective tissue are thicker, interwoven, and more
randomly organized
1. Allows tissue to sustain tension exerted from many different directions
2. Found in the dermis (inner layer of skin)
e. Elastic Connective Tissue
i. Consists elastic fibers in parallel strands
ii. Found between these elastic fibers are collagenous fibers and fibroblasts
iii. This tissue is located: (where elasticity is crucial to function)
1. Between vertebrae
2. Larger arteries
3. Portion of the heart
4. Large airways
(Specialized Connective Tissue)
f. Cartilage
i. A rigid connective tissue
ii. Functions to:
1. Provide support
2. Provide frameworks
3. Serve as attachment site
4. Protects underlying tissues
5. Forms structural models for many
developing bones
iii. Cartilage extracellular matrix
1. Largely compose of Collagenous
fibers embedded in gel-like ground
substance
a. Chondrocytes (cartilage cells)
occupy small chambers called
lacunae and lie completely
protected within the matrix
iv. Cartilaginous structures are enclosed in a
covering of connective tissue called
perichondrium
v. Although cartilage tissue lacks a direct
blood supply, blood vessels lie in the
surrounding perichondrium
1. Cells near the perichondrium obtain
nutrients from these vessels by
diffusion, which is aided by water
in the extracellular matrix’
vi. The lack of a direct blood supply is why torn cartilage heals so slowly, and
why Chondrocytes do not divide frequently
vii. 3 different types of cartilage defined by their extracellular matrix
1. Hyaline cartilage (very fine Collagenous fibers)
2. Elastic cartilage (dense network of elastic fibers)
3. Fibrocartilage (large Collagenous fibers)
viii. Hyaline Cartilage
1. Most common type of cartilage
2. Looks somewhat like white glass
3. Found:
a. At the end of bones
b. In many joints
c. Soft part of the nose
d. Supporting rings of the
respiratory system
4. Parts of an embryo’s skeleton begins
as hyaline cartilage that “models” a bone that will gradually replace it
a. Ossification
ix. Elastic Cartilage
1. More flexible than hyaline cartilage
because extracellular matrix contains
many elastic fibers
2. Provides framework for:
a. External ears
b. Parts of the larynx (vocal cords)
x. Fibrocartilage
1. Very tough tissue, contains many dense Collagenous
fibers
2. Shock absorber for structures that are subjected to
pressure
a. Intervertebral discs between vertebrae
b. Cushions bones in knees and in the pelvic
girdle
g. Bone
h. Blood
i. Composed of cells that are suspended in a fluid of extracellular matrix called
plasma
ii. These cells include:
1. Red Blood Cells (Erythrocytes)
2. White Blood Cells (Leukocytes)
3. Cellular fragments called platelets (Megakaryocytes)
iii. Red blood cells transport gases
1. Exchange oxygen and carbon dioxide via respiration (inhalation/
exhalation)
iv. White blood cells fight infection
v. Platelets are involved in blood clotting
vi. Most blood cells form in special tissues called hematopoietic tissues
1. These tissues are located red bone marrow
vii. Of all the blood cells, only RBC’s function entirely within the blood vessels
viii. WBC’s typically migrate from the blood through capillary walls. They then
enter connective tissues where they carry on their major activities
4. Muscle Tissue
a. General Characteristics
i. Cells in muscle tissue are elongated and are called muscle fibers
ii. Contractile units- they can shorten and thicken
1. As they contract,
muscle cells pull
at their attached
ends, which moves
body parts
iii. 3 types:
1. Skeletal
2. Smooth
3. Cardiac
b. Skeletal muscle tissue
i. Forms muscles that
usually attach to bones
and that are controlled
ii.
iii.
iv.
v.
vi.
by conscious effort (voluntary muscles)
Skeletal muscles cells are long and narrow
Have alternating light and dark cross-markings called striations
Each cell has many nuclei (multinucleate)
A message from a nerve cell can stimulate a muscle cell to contract by causing
protein filaments within the muscles cell to slide past one another
1. Then, the muscle cell relaxes when nerve cell stimulation stops
Skeletal muscles move the head, trunk, and limbs and enable us to make facial
expressions, write, talk, and sing, as well as chew, swallow, and breathe.
c. Smooth muscle tissue
i. Called smooth muscle because it
lacks striations
ii. Shorter than skeletal muscles
iii. Spindle-shaped and each have a
single, centrally located nucleus
iv. Makes up the walls of hollow
internal organs
1. Stomach, intestines, urinary
bladder, uterus, and blood
vessels
v. Unlike skeletal muscle, smooth
muscle usually cannot be
stimulated to contract by
conscious efforts (involuntary
muscles)
vi. For example, smooth muscle
tissue moves food through the
digestive tract, constricts blood
vessels, and empties the urinary
bladder
1. Peristalsis
d. Cardiac muscle
i. Found only in the heart
ii. Cells are striated and branched and are
joined end to end
1. The result is muscle cells that
are branched and interconnected
in complex networks
iii. Each cell has a single nucleus
iv. Where one cell touches another cells is
a specialized intercellular junction
called an intercalated disc
v. Cardiac muscle, like smooth muscle, is involuntary and in fact can continue to
function without being stimulated by nerve impulses
vi. This tissue makes up the bulk of the heart and pumps blood through the heart
chambers and into blood vessels.
5. Nervous Tissue
a. Found in the brain, spinal cord, and
peripheral nerves
b. Cells are called nerve cells or
neurons
i. Highly specialized cells
c. Neurons sense certain changes in
their surroundings and respond by
transmitting nerve impulses along
cellular processes to other neurons or
to muscles or glands
i. As a result of the extremely
complex patterns by which neurons
connect with each other and with
muscle and gland cells, they can
coordinate, regulate and integrate
many body functions
d. In addition to neurons, nervous tissue
includes very abundant neuroglia cells.
i. These cells support and bind the
components of nervous tissue
ii. They connect neurons to blood
vessels
iii. They also play a role in cell-to-cell
communication